A new tetra­kis-substituted pyrazine carb­oxy­lic acid, 3,3′,3′′,3′′′-{[pyrazine-2,3,5,6-tetra­yltetra­kis(methyl­ene)]tetra­kis­(sulfanedi­yl)}tetra­propionic acid: crystal structures of two triclinic polymorphs and of two potassium–organic frameworks

The crystal structures of two triclinic polymorphs of a new tetra­kis-substituted pyrazine carb­oxy­lic acid, 3,3′,3′′,3′′′-[(pyrazine-2,3,5,6-tetra­yltetra­kis­(methyl­ene))tetra­kis­(sulfanedi­yl)]tetra­propionic acid, are reported, together with the crystal structures of two potassium-organic frameworks.

Abstract

Two polymorphs of the title tetra­kis-substituted pyrazine carb­oxy­lic acid, 3,3′,3′′,3′′′-{[pyrazine-2,3,5,6-tetra­yltetra­kis­(methyl­ene))tetra­kis­(sulfanedi­yl]}tetra­propionic acid, C₂₀H₂₈N₂O₈S₄, (H₄L1), have been obtained, H₄L1_A and H₄L1_B. Each structure crystallized with half a mol­ecule in the asymmetric unit of a triclinic P unit cell. The whole mol­ecules are generated by inversion symmetry, with the pyrazine rings being located about inversion centers. The crystals of H₄L1_B were of poor quality, but the X-ray diffraction analysis does show the change in conformation of the –CH₂—S—CH₂—CH₂– side chains compared to those in polymorph H₄L1_A. In the crystal of H₄L1_A, mol­ecules are linked by two pairs of O—H⋯O hydrogen bonds, enclosing R ² ₂(8) ring motifs forming layers parallel to plane (100), which are linked by C—H⋯O hydrogen bonds to form a supra­molecular framework. In the crystal of H₄L1_B, mol­ecules are also linked by two pairs of O—H⋯O hydrogen bonds enclosing R ² ₂(8) ring motifs, however here, chains are formed propagating in the [001] direction and stacking up the a-axis. Reaction of H₄L1 with Hg(NO₃)₂ in the presence of a potassium acetate buffer did not produce the expected binuclear complex, instead crystals of a potassium–organic framework were obtained, poly[(μ-3-{[(3,5,6-tris­{[(2-carb­oxy­eth­yl)sulfan­yl]meth­yl}pyrazin-2-yl)meth­yl]sulfan­yl}propano­ato)potassium], [K(C₂₀H₂₇N₂O₈S₄)]_n (KH₃L1). The organic mono-anion possesses inversion symmetry with the pyrazine ring being located about an inversion center. A carb­oxy H atom is disordered by symmetry and the charge is compensated for by a potassium ion. A similar reaction with Zn(NO₃)₂ resulted in the formation of crystals of a dipotassium-organic framework, poly[(μ-3,3′-{[(3,6-bis­{[(2-carb­oxy­eth­yl)sulfan­yl]meth­yl}pyrazine-2,5-di­yl)bis(methyl­ene)]bis­(sulfanedi­yl)}dipropionato)dipotassium], [K₂(C₂₀H₂₆N₂O₈S₄)]_n (K₂H₂L1). Here, the organic di-anion possesses inversion symmetry with the pyrazine ring being located about an inversion center. Two symmetry-related acid groups are deprotonated and the charges are compensated for by two potassium ions.

Chemical context  

The title tetrakis-substituted pyrazine carb­oxy­lic acid, 3,3′,3′′,3′′′-[(pyrazine-2,3,5,6-tetra­yltetra­kis­(methyl­ene))tetra­kis­(sulfane­di­yl)]tetra­propionic acid (H₄L1), is to the best of our knowledge, only the third pyrazine tetrakis-substituted carb­oxy­lic acid ligand to have been synthesized. The first is pyrazine-2,3,5,6-tetra­carb­oxy­lic acid (pztca), which was originally synthesized by Wolff at the end of the 19th century (Wolff, 1887 ▸, 1893 ▸), while the second is 4,4′,4′′,4′′′-(pyrazine-2,3,5,6-tetra­yl)tetra­benzoic acid (pztba), which was first synthesized by Jiang et al. (2017 ▸). Pztca (Fig. 1 ▸) has been used to synthesize a number of coordination polymers, the first being poly{[(2,5-di­carb­oxy­pyrazine-3,6-di­carboxyl­ato)transdi­aqua­iron(II) dihydrate]} (Marioni et al., 1986 ▸), while pztba (Fig. 1 ▸) has been shown to form a series of metal–organic frameworks (Jiang et al., 2017 ▸; Wang et al., 2019 ▸).

Figure 1.

Chemical diagrams for pyrazine-2,3,5,6-tetra­carb­oxy­lic acid (pztca), 4,4′,4′′,4′′′-(pyrazine-2,3,5,6-tetra­yl)tetra­benzoic acid (pztba), pyrazine-2,3-di­carb­oxy­lic acid (pzdca) and pyridine-2,6-di­carb­oxy­lic acid (pydca).

The title ligand was synthesized to study its coordination behaviour with various transition metal ions (Pacifico, 2003 ▸). Potentially the ligand can coordinate in a bis-penta­dentate manner, as was shown to be the case for a similar ligand, 2,2′,2′′,2′′′-{[pyrazine-2,3,5,6-tetra­yltetra­kis­(methyl­ene)]tetra­kis­(sulfanedi­yl)}tetra­kis­(ethan-1-amine) (H₄L2), for which two nickel(II) binuclear complexes, I and II, were synthesized (Pacifico, 2003 ▸; Pacifico & Stoeckli-Evans, 2020 ▸); see Fig. 2 ▸.

Figure 2.

Chemical diagram for 2,2′,2′′,2′′′-[(pyrazine-2,3,5,6-tetra­yltetra­kis(methyl­ene)tetra­kis­(sulfanedi­yl)]tetra­kis­(ethan-1-amine) (H₄L2) and two nickel(II) binuclear complexes, I and II (Pacifico & Stoeckli-Evans, 2020 ▸).

Structural commentary  

The title tetra­kis-substituted pyrazine carb­oxy­lic acid, 3,3′,3′′,3′′′-[(pyrazine-2,3,5,6-tetra­yltetra­kis­(methyl­ene))tetra­kis­(sulfanedi­yl)]tetra­propionic acid (H₄L1_A), crystallized with half a mol­ecule in the asymmetric unit (Fig. 3 ▸). The whole mol­ecule is generated by inversion symmetry, with the pyrazine ring being located about an inversion center.

Figure 3.

The mol­ecular structure of H₄L1_A, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level. Unlabelled atoms are related to labelled atoms by symmetry operator −x + 2, −y + 1, −z + 1.

In an attempt to form a co-crystal, equimolar amounts of H₄L1 and terephthalic acid were mixed in methanol. On slow evaporation of the solvent, colourless plate-like crystals were obtained. X-ray diffraction analysis revealed their structure to be that of a second triclinic P polymorph, H₄L1_B (Fig. 4 ▸). It crystallized with half a mol­ecule in the asymmetric unit and the whole mol­ecule is generated by inversion symmetry, with the pyrazine ring being located about an inversion center. The crystals were of poor quality with one CH₂—CH₂—CO₂H side chain (atoms C8/C8B, C9/C9B, C10/C10B, O3/O3B, O4/O4B) of the centrosymmetric mol­ecule being positionally disordered (Fig. 4 ▸ b). The difference in the two polymorphs is essentially in the orientation of the –CH₂—S—CH₂—CH₂—C– side arms, as shown in Fig. 5 ▸ a and b. Selected torsion angles are given in Table 1 ▸.

Figure 4.

(a) The mol­ecular structure of H₄L1_B, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level. (b) A view of the mol­ecular structure of H₄L1_B with the symmetry-related disordered side chains (C8/C8B, C9/C9B, C10/C10B, O3/O3B and O4/O4B) shown with dashed bonds. Unlabelled atoms are related to labelled atoms by symmetry operator −x + 2, −y + 1, −z + 1.

Figure 5.

A comparison of the orientation of the –CH₂—S—CH₂—CH₂– side chains in (a) polymorph H₄L1_A, (b) for the major disordered component of polymorph H₄L1_B, (c) KH₃L1 and (d) K₂H₂L1 [see Table 1 ▸ for further details; symmetry codes: (i) = (ii) −x + 2, −y + 1, −z + 1; (iii) −x + , −y + , −z; (iv) −x + , −y + , −z + 1].

Table 1. Selected torsion angles (°) along the C_ar—CH₂—S—CH₂—CH₂—CO₂H side chains in compounds H₄L1_A, H₄L1_B, KH₃L1 and K₂H₂L1 .

Torsion angle	H4L1_A	H4L1_B	KH3L1	K2H2L1
C1—C3—S1—C4	174.1 (2)	−72.6 (4)	−72.32)	−65.81 (15)
C3—S1—C4—C5	−155.3 (2)	−86.7 (4)	−90.3 (2)	−87.72 (15)
S1—C4—C5—C6	−167.9 (2)	−65.0 (6)	−76.4 (3)	−73.19 (18)
C2—C7—S2—C8	57.6 (2)	−66.8 (4)	−62.3 (2)	−67.34 (15)
C7—S2—C8—C9	65.7 (2)	−178.1 (5)	−77.5 (2)	97.89 (15)
S2—C8—C9—C10	174.8 (2)	−172.5 (5)	−173.8 (2)	174.51 (12)

Reaction of H₄L1 with Hg(NO₃)₂ in the presence a 1 M potassium acetate buffer led to the formation of colourless crystals that proved to be a potassium–organic framework (KH₃L1); see Fig. 6 ▸. The asymmetric unit consists of half a mono-deprotonated ligand mol­ecule located about an inversion center, and half a potassium ion located on an inversion center. The carb­oxy H atom is disordered by symmetry. The K⁺ ion is linked to the O atoms of the acid groups and has a coordination number of eight (KO₈) and a distorted dodeca­hedral geometry (Fig. 7 ▸ a). The K⋯O bond lengths vary between 2.682 (2) and 3.069 (3) Å (Table 2 ▸). Inter­estingly, here there is a significant difference between the K⋯O(C=O) and K⋯O(O⁻) distances: 2.6823 (2) and 2.828 (2) Å compared to 3.056 (3) and 3.069 (3) Å, respectively.

Figure 6.

The mol­ecular structure of complex KH₃L1, with labels for the atoms in the asymmetric unit of the organic anion. Unlabelled atoms are related to labelled atoms by symmetry operator (i) −x + , −y + , −z. Displacement ellipsoids are drawn at the 50% probability level. [Further symmetry codes are: (ii) −x + 1, −y, −z: (iii) x, y + 1, z; (iv) x, y, z + 1; (v) −x + , −y + , −z − 1; (vi) x − , y + , z; (vii) −x + , −y − , −z.]

Figure 7.

(a) Views of the coordination sphere of the potassium ion in KH₃L1 [symmetry code: (i) −x + 1, y, −z − ] and (b) views of the coordination sphere of the potassium ions in K₂H₂L1 [symmetry codes: (i) −x, y, −z + ; (ii) x, y − 1, z; (iii) x, y + 1, z; (iv) −x, y + 1, −z + ].

Table 2. Selected bond lengths (Å) for KH₃L1 .

K1—O1	2.828 (2)	K1—O3ii	2.682 (2)
K1—O2i	3.056 (3)	K1—O4iii	3.069 (3)

Symmetry codes: (i) x, -y, z-{\script{1\over 2}}; (ii) -x+{\script{1\over 2}}, y-{\script{1\over 2}}, -z-{\script{1\over 2}}; (iii) x+{\script{1\over 2}}, -y-{\script{1\over 2}}, z-{\script{1\over 2}}.

Reaction of H₄L1 with Zn(NO₃)₂ in the presence of a 1 M potassium acetate buffer led to the formation of colourless crystals that proved to be a dipotassium–organic framework (K₂H₂L1); see Fig. 8 ▸. The asymmetric unit consists of half a di-deprotonated ligand mol­ecule located about an inversion center, and two half potassium ions located on inversion centers. The K⁺ ions are linked to the O atoms of the acid groups and both K⁺ ions have a coordination number of six (KO₆) and have edge-sharing bipyramidal geometries. The K⁺ ions are bridged by atoms O1 and O3, forming chains propagating along the b-axis direction (Fig. 7 ▸ b). The K⋯O bond lengths vary between 2.6682 (12) and 2.8099 (14) Å (Table 3 ▸). Here, the difference between the K⋯O(C=O) and K⋯O(O⁻) bond lengths is much less significant (Table 3 ▸).

Figure 8.

The mol­ecular structure of complex K₂H₂L1, with labels for the atoms in the asymmetric unit of the organic dianion. Unlabelled atoms are related to labelled atoms by symmetry operator (i) −x + , −y + , −z + 1. Displacement ellipsoids are drawn at the 50% probability level. [Further symmetry codes are: (ii) −x, −y + 2, −z + 1; (iii) x, y + 1, z; (iv) x + , y + , z; (v) −x + , −y + , −z + 1; (vi) x + , y + , z.]

Table 3. Selected bond lengths (Å) for K₂H₂L1 .

K1—O1i	2.7084 (14)	K2—O1	2.7132 (13)
K1—O2	2.6682 (12)	K2—O3iii	2.6682 (13)
K1—O3ii	2.8099 (14)	K2—O4ii	2.7209 (12)

Symmetry codes: (i) x, -y+2, z+{\script{1\over 2}}; (ii) x-{\script{1\over 2}}, y-{\script{1\over 2}}, z; (iii) -x+{\script{1\over 2}}, -y+{\script{3\over 2}}, -z+1.

The K⋯O bond lengths in the KH₃L1 and K₂H₂L1 frameworks are close to those observed for similar compounds; see §6 Database survey. The conformation of one of the –CH₂—S—CH₂—CH₂– side chains (involving atom S1) of the organic anion are similar, and similar to that in H₄L1_B (Fig. 5 ▸ b), while the conformation of the second (involving atom S2) differs significantly (Fig. 5 ▸ c and d, and Table 1 ▸).

Supra­molecular features  

In the crystal of H₄L1_A, mol­ecules are linked by pairs of O—H⋯O hydrogen bonds, forming classical carb­oxy­lic acid inversion dimers enclosing (8) loops (Fig. 9 ▸ and Table 4 ▸). These inter­actions lead to the formation of layers lying parallel to the bc plane. The layers are linked by C—H⋯O hydrogen bonds (Table 4 ▸), forming a supra­molecular framework.

Figure 9.

A view along the a axis of the crystal packing of H₄L1_A. The hydrogen bonds are shown as dashed lines (see Table 4 ▸).

Table 4. Hydrogen-bond geometry (Å, °) for H₄L1_A .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2O⋯O1i	0.87 (2)	1.80 (2)	2.667 (3)	172 (5)
O4—H4O⋯O3ii	0.83 (2)	1.85 (2)	2.673 (3)	175 (5)
C5—H5A⋯O3iii	0.97	2.55	3.405 (4)	147
C8—H8A⋯O4iv	0.97	2.40	3.308 (4)	156

Symmetry codes: (i) -x-1, -y, -z; (ii) -x+1, -y+1, -z; (iii) x-1, y, z; (iv) x+1, y, z.

In the crystal of H₄L1_B, mol­ecules are linked by pairs of O—H⋯O hydrogen bonds, forming chains propagating along the c-axis direction and enclosing (8) loops (Fig. 10 ▸ and Table 5 ▸). There are no other significant directional contacts present in the crystal.

Figure 10.

A view along the a-axis of the crystal packing of H₄L1_B. Only atoms of the major component are shown. The hydrogen bonds are shown as dashed lines (see Table 5 ▸).

Table 5. Hydrogen-bond geometry (Å, °) for H₄L1_B .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2O⋯O3i	0.82	1.94	2.66 (1)	146
O2—H2O⋯O3B i	0.82	2.20	2.77 (3)	127
O4—H4O⋯O1ii	0.82	1.88	2.66 (1)	158
O4B—H4OB⋯O1ii	0.82	1.86	2.67 (4)	170

Symmetry codes: (i) x, y, z+1; (ii) x, y, z-1.

In both KH₃L1 and K₂H₂L1, the organic anions are arranged as rungs of parallel ladders, so forming the framework structures, as shown in Figs. 11 ▸ and 12 ▸, respectively. The frameworks are reinforced by O—H⋯O, C—H⋯O and C—H⋯N hydrogen bonds (Tables 6 ▸ and 7 ▸, respectively).

Figure 11.

A view along the b axis of the crystal packing of complex KH₃L1. For clarity, the H atoms have been omitted.

Figure 12.

A view along the b axis of the crystal packing of complex K₂H₂L1. For clarity, the H atoms have been omitted.

Table 6. Hydrogen-bond geometry (Å, °) for KH₃L1 .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O4—H4O⋯O1iv	0.80 (5)	1.86 (5)	2.661 (3)	180 (7)
O2—H20⋯O2v	1.24 (1)	1.24 (1)	2.436 (3)	159 (7)
C4—H4A⋯N1	0.99	2.52	3.340 (4)	140
C4—H4B⋯O3vi	0.99	2.49	3.114 (4)	121
C5—H5B⋯O2i	0.99	2.60	3.467 (4)	146
C7—H7B⋯N1vii	0.99	2.60	3.454 (4)	144
C9—H9A⋯O3vii	0.99	2.58	3.465 (4)	149

Symmetry codes: (i) x, -y, z-{\script{1\over 2}}; (iv) x-{\script{1\over 2}}, y+{\script{1\over 2}}, z; (v) -x+1, y, -z+{\script{1\over 2}}; (vi) -x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z; (vii) x, -y, z+{\script{1\over 2}}.

Table 7. Hydrogen-bond geometry (Å, °) for K₂H₂L1 .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O4—H4O⋯O2iv	0.85 (2)	1.61 (2)	2.4637 (16)	177 (3)
C4—H4A⋯N1	0.99	2.44	3.266 (2)	141
C8—H8A⋯O3v	0.99	2.53	3.436 (2)	151

Symmetry codes: (iv) x+{\script{1\over 2}}, y+{\script{1\over 2}}, z; (v) x, -y+2, z-{\script{1\over 2}}.

Hirshfeld surface analysis and two-dimensional fingerprint plots for H₄L1_A, and H₄L1_B  

The Hirshfeld surface analysis (Spackman & Jayatilaka, 2009 ▸) and the associated two-dimensional fingerprint plots (McKinnon et al., 2007 ▸) were performed with CrystalExplorer17 (Turner et al., 2017 ▸) following the protocol of Tiekink and collaborators (Tan et al., 2019 ▸).

The Hirshfeld surfaces are colour-mapped with the normalized contact distance, d _norm, varying from red (distances shorter than the sum of the van der Waals radii) through white to blue (distances longer than the sum of the van der Waals radii). The Hirshfeld surfaces (HS) of H₄L1_A, and H₄L1_B mapped over d _norm are given in Fig. 13 ▸. The most significant short contacts in the crystal structures of the two polymorphs are given in Table 8 ▸. The large red spots in Fig. 13 ▸ a and b concern the O—H⋯O hydrogen bonds in the crystal structures of both compounds.

Figure 13.

The Hirshfeld surfaces of compounds (a) H₄L1_A and (b) H₄L1_B, mapped over d _norm in the colour ranges of −0.7146 to 1.2167 and −0.6847 to 1.3548 au., respectively.

Table 8. Short contacts (Å) in the crystal structures of H₄L1_A and H₄L1_B ^a .

Atom 1	Atom 2	Length	Length − VdW	Symm. op. 1	Symm. op. 2
H4L1_A
O1	H2O	1.798	−0.922	x, y, z	−1 − x, −y, −z
O3	H4O	1.843	−0.877	x, y, z	1 − x, 1 − y, −z
O1	O2	2.667	−0.373	x, y, z	−1 − x, −y, −z
O3	O4	2.673	−0.367	x, y, z	1 − x, 1 − y, −z
O4	H8A	2.399	−0.321	x, y, z	−1 + x, y, z
O2	O4	3.015	−0.025	x, y, z	−x, 1 − y, −z
C6	H2O	2.667	−0.233	x, y, z	−1 − x, −y, −z
C10	H4O	2.668	−0.232	x, y, z	1 − x, 1 − y, −z
H5A	O3	2.549	−0.171	x, y, z	−1 + x, y, z
H4O	H4O	2.371	−0.029	x, y, z	1 − x, 1 − y, −z
H2O	H2O	2.389	−0.011	x, y, z	−1 − x, −y, −z
N1	H3A	2.807	0.057	x, y, z	1 − x, 1 − y, 1 − z
O4	C8	3.308	0.088	x, y, z	−1 + x, y, z
O2	H8A	2.820	0.100	x, y, z	1 − x, 1 − y, −z
H4L1_Ba
H4O	O1	1.879	−0.841	x, y, z	x, y, −1 + z
O4	O1	2.658	−0.382	x, y, z	x, y, −1 + z
O3	O2	2.663	−0.377	x, y, z	x, y, −1 + z
H4O	C6	2.580	−0.320	x, y, z	x, y, −1 + z
O4	O2	2.799	−0.241	x, y, z	−1 + x, y, −1 + z
H4O	H2O	2.173	−0.227	x, y, z	x, y, −1 + z
O1	O2	2.982	−0.058	x, y, z	−1 + x, y, z
S1	H3A	2.951	−0.049	x, y, z	−1 + x, y, z
S1	S2	3.590	−0.010	x, y, z	1 − x, −y, 1 − z
O4	O3	3.041	0.001	x, y, z	−1 + x, y, z
S2	S2	3.613	0.013	x, y, z	1 − x, −y, 1 − z
H8A	O3	2.749	0.029	x, y, z	−1 + x, y, z
S1	H5A	3.047	0.047	x, y, z	−1 + x, y, z
H4O	O2	2.775	0.055	x, y, z	−1 + x, y, −1 + z
O4	H2O	2.776	0.056	x, y, z	−1 + x, y, −1 + z
C10	H2O	2.960	0.060	x, y, z	2 − x, −y, 1 − z
O3	H2O	2.796	0.076	x, y, z	2 − x, −y, 1 − z
H7B	C3	2.974	0.074	x, y, z	−1 + x, y, z
S2	H7B	3.082	0.082	x, y, z	1 − x, −y, 1 − z
O2	H5B	2.802	0.082	2 − x, 1 − y, 1 − z	−1 + x, y, −1 + z
S1	H9A	3.085	0.085	x, y, z	1 − x, −y, 1 − z

Note: (a) major component of H₄L1_B.

The percentage contributions of inter-atomic contacts to the HS for both compounds are compared in Table 9 ▸. The two-dimensional fingerprint plots for compounds H₄L1_A, and H₄L1_B are shown in Fig. 14 ▸. They reveal that the principal contributions to the overall HS involve H⋯H contacts at 37.2 and 36.3%, respectively, and O⋯H/H⋯O contacts at, respectively, 37.7 and 32.2%.

Table 9. Percentage contributions of inter-atomic contacts to the Hirshfeld surfaces of H₄L1_A and H₄L1_B^a .

Contact	% contribution	% contribution
	H4L1_A	H4L1_B a
H⋯H	37.2	36.3
O⋯H/H⋯O	37.7	32.2
S⋯H/H⋯S	13.4	16.1
C⋯H/H⋯C	4.5	4.9
N⋯H/H⋯N	3.0	2.5
C⋯N	0	0.8
C⋯O	1.0	0.7
C⋯S	1.2	0
N⋯S	0.4	0.4
O⋯O	1.3	4.9
O⋯S	0.2	0
S⋯S	0.2	1.2

Note: (a) major component of H₄L1_B.

Figure 14.

The full two-dimensional fingerprint plots for compounds (a) H₄L1_A and (b) H₄L1_B, and those delineated into H⋯H, O⋯H/H⋯O and S⋯H/H⋯S contacts.

The third most important contribution to the HS is from the S⋯H/H⋯S contacts at 13.4 and 16.1%, for H₄L1_A, and H₄L1_B, respectively. These are followed by C⋯H/H⋯H contacts at, respectively, 4.5 and 4.9%. The N⋯H/H⋯N contacts contribute, respectively, 3.0 and 2.5%.

Energies frameworks for H₄L1_A, and H₄L1_B  

The colour-coded inter­action mappings within a radius of 6 Å of a central reference mol­ecule for H₄L1_A, and H₄L1_B, are given in Fig. 15 ▸. Full details of the various contributions to the total energy (E _tot) are also included there; see Tan et al. (2019 ▸) for an explanation of the various parameters.

Figure 15.

The colour-coded inter­action mappings within a radius of 6 Å of a central reference mol­ecule for (a) H₄L1_A and (b) H₄L1_B.

A comparison of the energy frameworks calculated for H₄L1_A, and H₄L1_B, showing the electrostatic potential forces (E _ele), the dispersion forces (E _dis) and the total energy diagrams (E_tot), are shown in Fig. 16 ▸. The energies were obtained by using the wave function at the HF/3-21G level of theory. The cylindrical radii are proportional to the relative strength of the corresponding energies (Turner et al., 2017 ▸; Tan et al., 2019 ▸). They have been adjusted to the same scale factor of 80 with a cut-off value of 5 kJ mol⁻¹ within a radius of 6 Å of a central reference mol­ecule. It can be seen that for both polymorphs the major contribution to the inter­molecular inter­actions is from electrostatic potential forces (E _ele), reflecting the presence of the classical O—H⋯O hydrogen bonds.

Figure 16.

The energy frameworks calculated for (a) H₄L1_A and (b) H₄L1_B, both viewed along the b-axis direction, showing the electrostatic potential forces (E _ele), the dispersion forces (E _dis) and the total energy diagrams (E _tot).

Database survey  

A search of the Cambridge Structural Database (CSD, Version 5.42, last update February 2021; Groom et al., 2016 ▸) for tetrakis-substituted pyrazine carb­oxy­lic acids gave results for only two such ligands, viz. 2,3,5,6-pyrazine­tetra­carb­oxy­lic acid (pztca) and 2,3,5,6-tetra­kis­(4-carb­oxy­phen­yl)pyrazine (pztba). Ligand pztba has been shown to be extremely successful in forming metal–organic frameworks (Jiang et al., 2017 ▸; Wang et al., 2019 ▸).

Potassium salts of carb­oxy­lic acids are relatively common. A search for potassium salts of purely organic carb­oxy­lic acids and excluding hydrates, yielded over 200 hits. The potassium salt of pztca has been reported, viz. catena-[(μ₄-3,5,6-tri­carb­oxy­pyrazine-2-carboxyl­ato)potassium] (CSD refcode UBUPAK; Masci et al., 2010 ▸). The structure of UBUPAK is that of a potassium–organic framework (Fig. 17 ▸ a). The asymmetric unit consists of half a mono-deprotonated ligand mol­ecule located about an inversion center, and half a potassium ion. The carb­oxy H atom is disordered by symmetry, similar to the situation in the structure of KH₃L1. Here the K⋯O bond lengths vary from 2.7951 (11) to 2.8668 (13) Å. The K⁺ cation has a coordination number of 8 (KO₈) and a distorted dodeca­hedral geometry as in KH₃L1 (Fig. 7 ▸ a and 11).

Figure 17.

(a) A view along the a axis of the potassium–organic framework of UBUPAK (Masci et al., 2010 ▸) and (b) a view along the c axis of the potassium–organic framework of MUMPIW (Li et al., 2020 ▸).

The structure of the potassium salt of pyrazine-2,3-di­carb­oxy­lic acid (pzdca; Fig. 1 ▸), catena-[(μ₂-3-carb­oxy­pyrazine-2-carboxyl­ato)-(μ₂-pyrazine-2,3-di­carb­oxy­lic acid)di­aqua­potassium], has been reported (RISYIC; Tombul et al., 2008 ▸). It has a polymer chain structure with the chains linked by O—H⋯O hydrogen bonds, forming a supra­molecular framework. Here the K⋯O bond lengths vary from 2.8772 (14) to 3.0898 (14) Å.

The structures of two potassium salts of 2,6-pyridine-di­carb­oxy­lic acid (pydca; Fig. 1 ▸) have been reported. They include, bis­(μ₂-pyridine-2,6-di­carb­oxy­lic acid-N,O,O′:O′)-hexa­aqua­bis­(6-carb­oxy­pyridine-2-carboxyl­ato-O)dipotassium (HAMBEE; Santra et al., 2011 ▸; HAMBEE01; Hayati et al., 2017 ▸), and catena-[(μ-6-carb­oxy­pyridine-2-carboxyl­ato)potassium] (MUMPIW; Li et al., 2020 ▸). HAMBEE is a binuclear complex, which is linked by O—H⋯O hydrogen bonds to form supra­molecular chains. The K⋯O bond lengths vary from 2.721 (2) to 3.054 (3) Å.

The structure of MUMPIW is that of a potassium-organic framework (Fig. 17 ▸ b), with the K⋯O bonds lengths varying from 2.8197 (14) to 3.0449 (15) Å. The K⁺ ion has a coordination number of seven (KO₆N) and has an edge-sharing penta­gonal anti­prism geometry, forming chains (Fig. 17 ▸ b). This structure can be compared to that of K₂H₂L1 where the two independent K⁺ ions, each with a coordination number of six (KO₆), have edge-sharing bipyramidal geometries, also forming chains (Fig. 7 ▸ b and 12).

Synthesis and crystallization  

The synthesis and crystal structure of the reagent tetra-2,3,5,6-bromo­methyl-pyrazine (TBr) have been reported (Ferigo et al., 1994 ▸; Assoumatine & Stoeckli-Evans, 2014 ▸ [CSD refcode: TOJXUN]).

Synthesis of 3,3′,3′′,3′′′-{[pyrazine-2,3,5,6-tetra­yltetra­kis(methyl­ene)]tetra­kis­(sulfanedi­yl)}tetra­propionic acid (H₄L1):

Mercaptopropionic acid (1.8795 g, 1.77 mol, 4 eq) was dissolved in 50 ml THF. A minimum amount of water (a few ml) was added to dissolve 1.4166 g (3.54 mol, 8 eq) of NaOH. The volume of the mixture was increased to 100 ml by adding THF and the reaction was stirred under reflux for 1 h. Then TBr (2 g, 4.42 mol, 1 eq) dissolved in 50 ml THF was added dropwise using an addition funnel. The mixture was stirred under reflux for 6 h. After drying under vacuum, the residue was dissolved in 50 ml of deionized water, and HCl puriss. was added dropwise until a clearly acid pH was obtained. This mixture was stirred at room temperature for 1–2 h. The yellow precipitate that formed was filtered off and washed with a minimum amount of water and then CHCl₃. It was then dried under vacuum conditions. Recrystallization carried out with methanol gave pale-yellow crystals of H₄L1 (yield 88%, m.p. 466 K) that X-ray diffraction analysis indicated to be triclinic polymorph H₄L1_A.

The presence of terephthalic acid in an equimolar qu­antity with H₄L1 in methanol gave colourless crystals of rather poor quality. However, X-ray diffraction analysis indicated that a second triclinic (P ) polymorph, H₄L1_B, had been obtained.

Spectroscopic and elemental analyses:

R _f: 0.77 (solvent: CH₃OH).

¹H NMR (CD₃OD, 400 MHz), δ(ppm): 4.03 (s, 8H, H2), 2.78 (t, 8H, ³ J _(3,4) = 7.0, H3), 2.62 (t, 8H, ³ J _(4,3) = 7.0, H4).

¹³C NMR (CD₃OD, 50 MHz), δ(ppm): 174.54 (4C, C5), 150.12 (4C, C1), 34.29 (4C, C4), 33.64 (4C, C2), 26.65 (4C, C3).

Elemental Analysis for C₂₀H₂₈N₂O₈S₄, M _w = 552.71 g mol⁻¹: Calculated: C 43.46, H 5.11, N 5.07%. Found: C 43.40, H 5.17, N 4.87%.

ESI–MS, m/z: 591.04 [M + K]⁺; 575.06 [M + Na]⁺; 553.08 [M + H]⁺; 471.07; 449.09.

IR (KBr disc, cm⁻¹) ν: 2926(s), 2666(m), 2590(s), 1693(s), 1429(s), 1406(s), 1340(m), 1270(s), 1200(s), 1163(m), 1134(s), 1107(m), 1055(w), 918(s), 658(m), 489(m).

Synthesis of poly[(μ-3-{[(3,5,6-tris­{[(2-carb­oxy­eth­yl)sulfan­yl]meth­yl}pyrazin-2-yl)meth­yl]sulfan­yl}propano­ate)potas­sium] (KH₃L1):

Hg(NO₃)₂ (45.0 mg, 0.109 mmol, 2 eq) and H₄L1 (30 mg, 0.054 mmol, 1 eq) were mixed together in 20 ml of a 1 M potassium acetate buffer. The mixture was left at 323 K under stirring and nitro­gen conditions for 1 h. The mixture was then filtered and left to evaporate in air for six weeks. Colourless plate-like crystals were obtained, which were shown to be a potassium–organic framework.

IR (KBr disc, cm⁻¹) ν: 3422(m), 2922(m), 1713(m), 1580(s), 1399(s), 1247(m), 1190(m), 1152(m), 1114(m), 811(m), 787(m).

Synthesis of poly[(μ-3,3′-{[(3,6-bis­{[(2-carb­oxy­eth­yl)sulf­an­yl]meth­yl}pyrazine-2,5-di­yl)bis­(methyl­ene)]bis­(sulfanedi­yl)}dipropionato)dipotassium] (K₂H₂L1):

Zn(NO₃)₂ (28.4 mg, 0.109 mmol, 2 eq) and H₄L1 (30 mg, 0.054 mmol, 1eq) were mixed together in 20 ml of a 1M potassium acetate buffer. The mixture was left at 323 K under stirring and nitro­gen for 1 h. The mixture was then filtered and left to evaporate in air for 6 weeks. Colourless plate-like crystals were obtained, which proved to be a dipotassium-organic framework.

IR (KBr disc, cm⁻¹) ν: 3401(m), 1579(s), 1401(s), 1303(m).

Refinement  

Crystal data, data collection and structure refinement details are summarized in Table 10 ▸.

Table 10. Experimental details.

	H4L1_A	H4L1_B	KH3L1	K2H2L1
Crystal data
Chemical formula	C20H28N2O8S4	C20H28N2O8S4	[K(C20H27N2O8S4)]	[K2(C20H26N2O8S4)]
M r	552.68	552.68	590.77	628.87
Crystal system, space group	Triclinic, P\overline{1}	Triclinic, P\overline{1}	Monoclinic, C2/c	Monoclinic, C2/c
Temperature (K)	293	293	153	153
a, b, c (Å)	5.5843 (8), 9.0061 (14), 12.739 (2)	4.9424 (17), 8.993 (3), 14.190 (6)	30.080 (4), 8.4716 (10), 9.5908 (12)	27.908 (2), 8.2916 (6), 11.3035 (9)
α, β, γ (°)	101.537 (18), 94.313 (18), 103.701 (17)	96.96 (3), 97.14 (3), 100.72 (3)	90, 94.717 (11), 90	90, 94.753 (6), 90
V (Å3)	604.80 (17)	608.1 (4)	2435.7 (6)	2606.7 (3)
Z	1	1	4	4
Radiation type	Mo Kα	Mo Kα	Mo Kα	Mo Kα
μ (mm−1)	0.44	0.44	0.61	0.73
Crystal size (mm)	0.35 × 0.30 × 0.05	0.50 × 0.50 × 0.05	0.50 × 0.50 × 0.10	0.50 × 0.50 × 0.05
Data collection
Diffractometer	Stoe IPDS 1	Stoe IPDS 2	Stoe IPDS 2	Stoe IPDS 2
Absorption correction	Empirical (using intensity measurements) (ShxAbs; Spek, 2020 ▸)	Empirical (using intensity measurements) (ShxAbs; Spek, 2020 ▸)	Multi-scan (MULABS; Spek, 2020 ▸)	Empirical (using intensity measurements) (ShxAbs; Spek, 2020 ▸)
T min, T max	0.647, 0.897	0.144, 0.616	0.640, 1.000	0.416, 0.803
No. of measured, independent and observed [I > 2σ(I)] reflections	4709, 2194, 1452	4152, 2201, 1537	10309, 2084, 1646	19423, 3646, 3175
R int	0.058	0.080	0.064	0.042
(sin θ/λ)max (Å−1)	0.615	0.617	0.590	0.695
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.041, 0.097, 0.88	0.071, 0.208, 1.05	0.039, 0.106, 1.02	0.037, 0.103, 1.05
No. of reflections	2194	2201	2084	3646
No. of parameters	162	173	165	167
No. of restraints	2	6	0	1
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement	H-atom parameters constrained	H atoms treated by a mixture of independent and constrained refinement	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)	0.35, −0.28	0.47, −0.39	0.26, −0.36	0.76, −0.51

Computer programs: EXPOSE, CELL and INTEGRATE in IPDS-I (Stoe & Cie, 2000 ▸), X-AREA and X-RED32 (Stoe & Cie, 2002 ▸), SHELXS97 (Sheldrick, 2008 ▸), SHELXL2018/3 (Sheldrick, 2015 ▸), PLATON (Spek, 2020 ▸) Mercury (Macrae et al., 2020 ▸) and publCIF (Westrip, 2010 ▸).

For H₄L1_A, KH₃L1 and K₂H₂L1, the various –CO₂H H atoms were located in difference-Fourier maps and freely refined. For H₄L1_B, the –CO₂H H atoms were difficult to locate, probably due to the poor quality of the crystal and the disorder in the side chain (atoms C8/C8B, C9/C9B, C10/C10B, O3/O3B, O4/O4B; Fig. 4 ▸ b). They were therefore included in calculated positions assuming the formation of carb­oxy­lic acid dimers; O—H = 0.82 Å and refined as riding with U _iso(H) = 1.5U _eq(O).

As in the K⁺ salt of pyrazine tetra­carb­oxy­lic acid (UBUPAK; Masci et al., 2010 ▸), the carb­oxy H atom in KH₃L1 is disordered by symmetry, hence the H atom on O3 was given an occupancy factor of 0.5 to balance the charges.

For all four compounds, the C-bound H atoms were included in calculated positions and treated as riding on their parent C atom with C—H = 0.97 Å and U _iso(H) = 1.2U _eq(C).

For H₄L1_A and H₄L1_B, the alert _diffrn_reflns_point_group_measured_fraction_full value (0.94 and 0.93, respectively) below minimum (0.95) was given. For H₄L1_A it involves 131 random reflections out of a total of 2180, viz. 6.0%, while for H₄L1_B it involves 158 random reflections out of a total of 2184, viz. 7.2%.

For H₄L1_A, H₄L1_B and K₂H₂L1 the multiplicity of reflections was 2 or less and so an empirical absorption correction was applied.

Supplementary Material

CCDC references: 2074770, 2074769, 2074768, 2074767

Additional supporting information: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1A). Crystal data

C20H28N2O8S4	Z = 1
Mr = 552.68	F(000) = 290
Triclinic, P1	Dx = 1.517 Mg m−3
a = 5.5843 (8) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.0061 (14) Å	Cell parameters from 3225 reflections
c = 12.739 (2) Å	θ = 2.4–25.9°
α = 101.537 (18)°	µ = 0.44 mm−1
β = 94.313 (18)°	T = 293 K
γ = 103.701 (17)°	Plate, pale-yellow
V = 604.80 (17) Å3	0.35 × 0.30 × 0.05 mm

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1A). Data collection

STOE IPDS 1 diffractometer	2194 independent reflections
Radiation source: fine-focus sealed tube	1452 reflections with I > 2σ(I)
Plane graphite monochromator	Rint = 0.058
φ rotation scans	θmax = 25.9°, θmin = 2.4°
Absorption correction: empirical (using intensity measurements) (ShxAbs; Spek, 2020)	h = −6→6
Tmin = 0.647, Tmax = 0.897	k = −11→11
4709 measured reflections	l = −14→15

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1A). Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.041	Hydrogen site location: mixed
wR(F2) = 0.097	H atoms treated by a mixture of independent and constrained refinement
S = 0.88	w = 1/[σ2(Fo2) + (0.0478P)2] where P = (Fo2 + 2Fc2)/3
2194 reflections	(Δ/σ)max < 0.001
162 parameters	Δρmax = 0.35 e Å−3
2 restraints	Δρmin = −0.28 e Å−3

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1A). Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1A). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
S1	0.40170 (15)	0.39121 (9)	0.29698 (6)	0.0312 (2)
S2	1.27548 (15)	0.86290 (9)	0.37908 (6)	0.0288 (2)
O1	−0.3381 (5)	0.0716 (3)	0.12207 (17)	0.0435 (6)
O2	−0.2098 (5)	0.1064 (3)	−0.03567 (17)	0.0409 (6)
H2O	−0.363 (5)	0.052 (5)	−0.059 (4)	0.098 (19)*
O3	0.7761 (4)	0.5277 (3)	0.08084 (16)	0.0379 (6)
O4	0.5045 (5)	0.6736 (3)	0.09232 (19)	0.0422 (6)
H4O	0.422 (8)	0.607 (4)	0.039 (3)	0.087 (17)*
N1	0.8353 (4)	0.5540 (3)	0.44074 (17)	0.0198 (5)
C1	0.7859 (5)	0.4024 (3)	0.4451 (2)	0.0194 (6)
C2	1.0447 (5)	0.6523 (3)	0.4952 (2)	0.0183 (6)
C3	0.5460 (5)	0.2957 (3)	0.3850 (2)	0.0248 (6)
H3A	0.434405	0.264980	0.436177	0.030*
H3B	0.577409	0.201607	0.342827	0.030*
C4	0.1473 (6)	0.2234 (4)	0.2308 (2)	0.0328 (7)
H4A	0.202811	0.128008	0.222673	0.039*
H4B	0.011542	0.214305	0.274306	0.039*
C5	0.0600 (6)	0.2449 (4)	0.1219 (2)	0.0347 (8)
H5A	0.041788	0.350865	0.129466	0.042*
H5B	0.186183	0.233148	0.074799	0.042*
C6	−0.1807 (6)	0.1321 (3)	0.0698 (2)	0.0291 (7)
C7	1.0877 (6)	0.8196 (3)	0.4857 (2)	0.0239 (6)
H7A	1.170302	0.887935	0.554088	0.029*
H7B	0.928434	0.841937	0.471163	0.029*
C8	1.0935 (6)	0.7220 (4)	0.2615 (2)	0.0277 (7)
H8A	1.187763	0.725553	0.200717	0.033*
H8B	1.068152	0.617707	0.275367	0.033*
C9	0.8427 (6)	0.7491 (3)	0.2307 (2)	0.0290 (7)
H9A	0.742172	0.735720	0.288698	0.035*
H9B	0.866452	0.856524	0.223186	0.035*
C10	0.7046 (6)	0.6407 (4)	0.1277 (2)	0.0283 (7)

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1A). Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
S1	0.0292 (5)	0.0246 (4)	0.0348 (4)	−0.0018 (3)	−0.0101 (3)	0.0109 (3)
S2	0.0243 (5)	0.0241 (4)	0.0376 (4)	−0.0013 (3)	0.0027 (3)	0.0156 (3)
O1	0.0333 (15)	0.0501 (14)	0.0362 (13)	−0.0022 (12)	−0.0093 (10)	0.0054 (11)
O2	0.0322 (16)	0.0486 (14)	0.0345 (13)	0.0001 (13)	−0.0099 (10)	0.0099 (10)
O3	0.0400 (15)	0.0425 (13)	0.0341 (12)	0.0216 (12)	−0.0002 (10)	0.0039 (10)
O4	0.0345 (15)	0.0519 (15)	0.0396 (13)	0.0217 (13)	−0.0064 (11)	0.0004 (12)
N1	0.0182 (14)	0.0159 (11)	0.0242 (11)	0.0010 (10)	−0.0009 (9)	0.0072 (9)
C1	0.0184 (16)	0.0158 (13)	0.0222 (13)	0.0006 (12)	0.0005 (10)	0.0055 (10)
C2	0.0182 (16)	0.0125 (12)	0.0226 (13)	0.0011 (12)	0.0009 (10)	0.0047 (10)
C3	0.0191 (17)	0.0189 (14)	0.0327 (15)	−0.0025 (13)	−0.0028 (11)	0.0085 (11)
C4	0.0259 (19)	0.0290 (16)	0.0359 (16)	−0.0069 (14)	−0.0053 (13)	0.0097 (13)
C5	0.032 (2)	0.0279 (16)	0.0404 (18)	0.0008 (15)	−0.0080 (14)	0.0114 (13)
C6	0.0228 (19)	0.0264 (16)	0.0360 (17)	0.0048 (15)	−0.0074 (13)	0.0083 (13)
C7	0.0251 (18)	0.0155 (13)	0.0313 (15)	0.0028 (13)	0.0021 (12)	0.0088 (11)
C8	0.0263 (18)	0.0316 (16)	0.0293 (15)	0.0092 (14)	0.0066 (12)	0.0132 (12)
C9	0.0281 (19)	0.0276 (16)	0.0324 (16)	0.0074 (15)	0.0008 (12)	0.0097 (12)
C10	0.0262 (18)	0.0385 (17)	0.0254 (15)	0.0125 (15)	0.0068 (12)	0.0129 (13)

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1A). Geometric parameters (Å, º)

S1—C3	1.796 (3)	C3—H3B	0.9700
S1—C4	1.818 (3)	C4—C5	1.500 (4)
S2—C8	1.813 (3)	C4—H4A	0.9700
S2—C7	1.825 (3)	C4—H4B	0.9700
O1—C6	1.233 (4)	C5—C6	1.493 (4)
O2—C6	1.307 (4)	C5—H5A	0.9700
O2—H2O	0.87 (2)	C5—H5B	0.9700
O3—C10	1.240 (4)	C7—H7A	0.9700
O4—C10	1.294 (4)	C7—H7B	0.9700
O4—H4O	0.830 (19)	C8—C9	1.514 (4)
N1—C2	1.332 (3)	C8—H8A	0.9700
N1—C1	1.341 (3)	C8—H8B	0.9700
C1—C2i	1.406 (3)	C9—C10	1.499 (4)
C1—C3	1.499 (4)	C9—H9A	0.9700
C2—C7	1.500 (3)	C9—H9B	0.9700
C3—H3A	0.9700
C3—S1—C4	97.53 (13)	C4—C5—H5B	108.8
C8—S2—C7	101.68 (14)	H5A—C5—H5B	107.7
C6—O2—H2O	108 (3)	O1—C6—O2	123.6 (3)
C10—O4—H4O	113 (3)	O1—C6—C5	122.7 (3)
C2—N1—C1	119.1 (2)	O2—C6—C5	113.7 (3)
N1—C1—C2i	120.3 (2)	C2—C7—S2	112.8 (2)
N1—C1—C3	117.7 (2)	C2—C7—H7A	109.0
C2i—C1—C3	122.0 (2)	S2—C7—H7A	109.0
N1—C2—C1i	120.6 (2)	C2—C7—H7B	109.0
N1—C2—C7	115.9 (2)	S2—C7—H7B	109.0
C1i—C2—C7	123.4 (2)	H7A—C7—H7B	107.8
C1—C3—S1	110.88 (18)	C9—C8—S2	114.2 (2)
C1—C3—H3A	109.5	C9—C8—H8A	108.7
S1—C3—H3A	109.5	S2—C8—H8A	108.7
C1—C3—H3B	109.5	C9—C8—H8B	108.7
S1—C3—H3B	109.5	S2—C8—H8B	108.7
H3A—C3—H3B	108.1	H8A—C8—H8B	107.6
C5—C4—S1	109.2 (2)	C10—C9—C8	113.5 (2)
C5—C4—H4A	109.8	C10—C9—H9A	108.9
S1—C4—H4A	109.8	C8—C9—H9A	108.9
C5—C4—H4B	109.8	C10—C9—H9B	108.9
S1—C4—H4B	109.8	C8—C9—H9B	108.9
H4A—C4—H4B	108.3	H9A—C9—H9B	107.7
C6—C5—C4	113.8 (3)	O3—C10—O4	122.8 (3)
C6—C5—H5A	108.8	O3—C10—C9	122.4 (3)
C4—C5—H5A	108.8	O4—C10—C9	114.8 (3)
C6—C5—H5B	108.8
C2—N1—C1—C2i	−1.2 (4)	C4—C5—C6—O1	26.8 (4)
C2—N1—C1—C3	178.6 (2)	C4—C5—C6—O2	−154.4 (3)
C1—N1—C2—C1i	1.2 (4)	N1—C2—C7—S2	−94.0 (3)
C1—N1—C2—C7	179.6 (2)	C1i—C2—C7—S2	84.3 (3)
N1—C1—C3—S1	11.3 (3)	C8—S2—C7—C2	57.6 (2)
C2i—C1—C3—S1	−168.8 (2)	C7—S2—C8—C9	65.7 (2)
C4—S1—C3—C1	174.1 (2)	S2—C8—C9—C10	174.8 (2)
C3—S1—C4—C5	−155.3 (2)	C8—C9—C10—O3	8.8 (4)
S1—C4—C5—C6	−167.9 (2)	C8—C9—C10—O4	−171.8 (3)

Symmetry code: (i) −x+2, −y+1, −z+1.

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1A). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2O···O1ii	0.87 (2)	1.80 (2)	2.667 (3)	172 (5)
O4—H4O···O3iii	0.83 (2)	1.85 (2)	2.673 (3)	175 (5)
C5—H5A···O3iv	0.97	2.55	3.405 (4)	147
C8—H8A···O4v	0.97	2.40	3.308 (4)	156

Symmetry codes: (ii) −x−1, −y, −z; (iii) −x+1, −y+1, −z; (iv) x−1, y, z; (v) x+1, y, z.

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1B). Crystal data

C20H28N2O8S4	Z = 1
Mr = 552.68	F(000) = 290
Triclinic, P1	Dx = 1.509 Mg m−3
a = 4.9424 (17) Å	Mo Kα radiation, λ = 0.71073 Å
b = 8.993 (3) Å	Cell parameters from 5563 reflections
c = 14.190 (6) Å	θ = 2.4–25.5°
α = 96.96 (3)°	µ = 0.44 mm−1
β = 97.14 (3)°	T = 293 K
γ = 100.72 (3)°	Plate, colourless
V = 608.1 (4) Å3	0.50 × 0.50 × 0.05 mm

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1B). Data collection

STOE IPDS 2 diffractometer	2201 independent reflections
Radiation source: fine-focus sealed tube	1537 reflections with I > 2σ(I)
Plane graphite monochromator	Rint = 0.080
φ + ω scans	θmax = 26.0°, θmin = 2.3°
Absorption correction: empirical (using intensity measurements) (ShxAbs; Spek, 2020)	h = −5→5
Tmin = 0.144, Tmax = 0.616	k = −11→9
4152 measured reflections	l = −17→17

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1B). Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.071	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.208	H-atom parameters constrained
S = 1.05	w = 1/[σ2(Fo2) + (0.1049P)2 + 0.4241P] where P = (Fo2 + 2Fc2)/3
2201 reflections	(Δ/σ)max = 0.001
173 parameters	Δρmax = 0.47 e Å−3
6 restraints	Δρmin = −0.39 e Å−3

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1B). Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1B). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
S1	0.7886 (3)	0.28919 (12)	0.71512 (9)	0.0583 (4)
S2	0.6227 (3)	0.07568 (12)	0.39724 (10)	0.0682 (5)
N1	1.2114 (8)	0.5110 (4)	0.5754 (3)	0.0500 (9)
C1	0.9965 (9)	0.3908 (4)	0.5566 (3)	0.0467 (10)
C2	0.7852 (9)	0.3796 (4)	0.4821 (3)	0.0469 (10)
C3	1.0020 (10)	0.2707 (4)	0.6214 (3)	0.0537 (11)
H3A	1.192760	0.277226	0.650755	0.064*
H3B	0.937959	0.170470	0.583113	0.064*
C4	0.9971 (12)	0.4560 (5)	0.7916 (4)	0.0644 (13)
H4A	1.087916	0.524956	0.752231	0.077*
H4B	0.876729	0.509027	0.826037	0.077*
C5	1.2177 (12)	0.4158 (6)	0.8638 (4)	0.0682 (14)
H5A	1.332589	0.358948	0.829232	0.082*
H5B	1.337009	0.509683	0.898069	0.082*
C6	1.0984 (14)	0.3238 (6)	0.9345 (4)	0.0728 (15)
O1	0.8532 (10)	0.3158 (5)	0.9473 (3)	0.0828 (12)
O2	1.2630 (12)	0.2603 (9)	0.9826 (5)	0.136 (2)
H2O	1.173990	0.186783	1.001978	0.204*
C7	0.5410 (10)	0.2468 (5)	0.4572 (4)	0.0559 (11)
H7A	0.394220	0.276430	0.416093	0.067*
H7B	0.470023	0.224151	0.515671	0.067*
C8	0.6926 (16)	0.1494 (6)	0.2872 (5)	0.0604 (17)	0.821 (6)
H8A	0.530565	0.183752	0.258819	0.072*	0.821 (6)
H8B	0.847467	0.236521	0.301719	0.072*	0.821 (6)
C9	0.7607 (15)	0.0292 (6)	0.2173 (5)	0.0657 (16)	0.821 (6)
H9A	0.597449	−0.051856	0.196091	0.079*	0.821 (6)
H9B	0.906849	−0.014697	0.248293	0.079*	0.821 (6)
C10	0.8546 (16)	0.0963 (7)	0.1325 (5)	0.0622 (15)	0.821 (6)
O3	1.0881 (16)	0.0900 (11)	0.1127 (6)	0.132 (3)	0.821 (6)
O4	0.6974 (19)	0.1598 (10)	0.0858 (6)	0.117 (3)	0.821 (6)
H4O	0.785351	0.212989	0.052298	0.175*	0.821 (6)
C8B	0.834 (7)	0.112 (3)	0.3062 (18)	0.0604 (17)	0.179 (6)
H8B1	0.957385	0.212176	0.321614	0.072*	0.179 (6)
H8B2	0.941870	0.034250	0.294752	0.072*	0.179 (6)
C9B	0.609 (6)	0.106 (3)	0.2219 (19)	0.0657 (16)	0.179 (6)
H9B1	0.490282	0.005115	0.207464	0.079*	0.179 (6)
H9B2	0.494650	0.179949	0.237286	0.079*	0.179 (6)
C10B	0.748 (6)	0.143 (4)	0.137 (2)	0.0622 (15)	0.179 (6)
O3B	0.998 (6)	0.188 (6)	0.137 (3)	0.132 (3)	0.179 (6)
O4B	0.576 (9)	0.176 (6)	0.073 (3)	0.117 (3)	0.179 (6)
H4OB	0.660348	0.228397	0.038152	0.175*	0.179 (6)

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1B). Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
S1	0.0546 (9)	0.0462 (6)	0.0762 (8)	0.0041 (5)	0.0158 (6)	0.0205 (5)
S2	0.0868 (11)	0.0329 (5)	0.0834 (9)	−0.0047 (5)	0.0293 (7)	0.0119 (5)
N1	0.045 (2)	0.0322 (16)	0.075 (2)	0.0074 (14)	0.0141 (17)	0.0146 (15)
C1	0.048 (3)	0.0259 (16)	0.071 (3)	0.0081 (15)	0.017 (2)	0.0160 (16)
C2	0.045 (3)	0.0292 (17)	0.070 (3)	0.0054 (15)	0.017 (2)	0.0152 (16)
C3	0.051 (3)	0.0350 (19)	0.080 (3)	0.0097 (17)	0.015 (2)	0.0220 (19)
C4	0.073 (4)	0.043 (2)	0.083 (3)	0.009 (2)	0.026 (3)	0.022 (2)
C5	0.063 (4)	0.061 (3)	0.077 (3)	−0.001 (2)	0.015 (3)	0.017 (2)
C6	0.064 (4)	0.066 (3)	0.090 (4)	0.003 (2)	0.013 (3)	0.033 (3)
O1	0.079 (3)	0.086 (3)	0.093 (3)	0.019 (2)	0.029 (2)	0.034 (2)
O2	0.085 (4)	0.190 (6)	0.162 (5)	0.031 (4)	0.031 (3)	0.122 (5)
C7	0.051 (3)	0.042 (2)	0.073 (3)	−0.0032 (18)	0.012 (2)	0.0155 (19)
C8	0.078 (5)	0.034 (3)	0.074 (4)	0.010 (2)	0.023 (3)	0.017 (2)
C9	0.084 (5)	0.040 (3)	0.079 (4)	0.011 (3)	0.026 (3)	0.022 (3)
C10	0.068 (5)	0.048 (3)	0.080 (4)	0.019 (3)	0.024 (3)	0.020 (3)
O3	0.096 (5)	0.194 (8)	0.145 (6)	0.052 (5)	0.052 (4)	0.113 (6)
O4	0.132 (8)	0.140 (5)	0.131 (5)	0.087 (5)	0.067 (5)	0.090 (4)
C8B	0.078 (5)	0.034 (3)	0.074 (4)	0.010 (2)	0.023 (3)	0.017 (2)
C9B	0.084 (5)	0.040 (3)	0.079 (4)	0.011 (3)	0.026 (3)	0.022 (3)
C10B	0.068 (5)	0.048 (3)	0.080 (4)	0.019 (3)	0.024 (3)	0.020 (3)
O3B	0.096 (5)	0.194 (8)	0.145 (6)	0.052 (5)	0.052 (4)	0.113 (6)
O4B	0.132 (8)	0.140 (5)	0.131 (5)	0.087 (5)	0.067 (5)	0.090 (4)

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1B). Geometric parameters (Å, º)

S1—C4	1.801 (5)	C7—H7A	0.9700
S1—C3	1.808 (5)	C7—H7B	0.9700
S2—C8B	1.78 (3)	C8—C9	1.490 (8)
S2—C7	1.804 (5)	C8—H8A	0.9700
S2—C8	1.816 (6)	C8—H8B	0.9700
N1—C1	1.342 (5)	C9—C10	1.496 (8)
N1—C2i	1.351 (5)	C9—H9A	0.9700
C1—C2	1.371 (6)	C9—H9B	0.9700
C1—C3	1.503 (5)	C10—O4	1.224 (8)
C2—C7	1.504 (6)	C10—O3	1.231 (9)
C3—H3A	0.9700	O4—H4O	0.8200
C3—H3B	0.9700	C8B—C9B	1.516 (19)
C4—C5	1.526 (8)	C8B—H8B1	0.9700
C4—H4A	0.9700	C8B—H8B2	0.9700
C4—H4B	0.9700	C9B—C10B	1.505 (19)
C5—C6	1.485 (7)	C9B—H9B1	0.9700
C5—H5A	0.9700	C9B—H9B2	0.9700
C5—H5B	0.9700	C10B—O3B	1.226 (19)
C6—O1	1.238 (7)	C10B—O4B	1.265 (19)
C6—O2	1.258 (8)	O4B—H4OB	0.8200
O2—H2O	0.8200
C4—S1—C3	100.2 (2)	C2—C7—H7B	108.8
C8B—S2—C7	112.9 (9)	S2—C7—H7B	108.8
C7—S2—C8	96.8 (2)	H7A—C7—H7B	107.7
C1—N1—C2i	117.9 (4)	C9—C8—S2	110.8 (4)
N1—C1—C2	121.2 (4)	C9—C8—H8A	109.5
N1—C1—C3	116.3 (4)	S2—C8—H8A	109.5
C2—C1—C3	122.5 (4)	C9—C8—H8B	109.5
N1i—C2—C1	120.9 (4)	S2—C8—H8B	109.5
N1i—C2—C7	115.7 (4)	H8A—C8—H8B	108.1
C1—C2—C7	123.5 (4)	C8—C9—C10	110.3 (5)
C1—C3—S1	113.3 (3)	C8—C9—H9A	109.6
C1—C3—H3A	108.9	C10—C9—H9A	109.6
S1—C3—H3A	108.9	C8—C9—H9B	109.6
C1—C3—H3B	108.9	C10—C9—H9B	109.6
S1—C3—H3B	108.9	H9A—C9—H9B	108.1
H3A—C3—H3B	107.7	O4—C10—O3	121.6 (7)
C5—C4—S1	112.3 (3)	O4—C10—C9	118.5 (7)
C5—C4—H4A	109.2	O3—C10—C9	119.8 (6)
S1—C4—H4A	109.2	C10—O4—H4O	109.5
C5—C4—H4B	109.2	C9B—C8B—S2	99.9 (19)
S1—C4—H4B	109.2	C9B—C8B—H8B1	111.8
H4A—C4—H4B	107.9	S2—C8B—H8B1	111.8
C6—C5—C4	113.3 (5)	C9B—C8B—H8B2	111.8
C6—C5—H5A	108.9	S2—C8B—H8B2	111.8
C4—C5—H5A	108.9	H8B1—C8B—H8B2	109.5
C6—C5—H5B	108.9	C10B—C9B—C8B	108 (2)
C4—C5—H5B	108.9	C10B—C9B—H9B1	110.0
H5A—C5—H5B	107.7	C8B—C9B—H9B1	110.0
O1—C6—O2	122.4 (5)	C10B—C9B—H9B2	110.0
O1—C6—C5	121.3 (5)	C8B—C9B—H9B2	110.0
O2—C6—C5	116.3 (6)	H9B1—C9B—H9B2	108.4
C6—O2—H2O	109.5	O3B—C10B—O4B	119 (3)
C2—C7—S2	113.8 (3)	O3B—C10B—C9B	126 (3)
C2—C7—H7A	108.8	O4B—C10B—C9B	110 (3)
S2—C7—H7A	108.8	C10B—O4B—H4OB	109.5
C2i—N1—C1—C2	−0.6 (6)	N1i—C2—C7—S2	103.4 (4)
C2i—N1—C1—C3	179.3 (4)	C1—C2—C7—S2	−75.4 (5)
N1—C1—C2—N1i	0.6 (7)	C8B—S2—C7—C2	−43.7 (10)
C3—C1—C2—N1i	−179.3 (4)	C8—S2—C7—C2	−66.8 (4)
N1—C1—C2—C7	179.3 (4)	C7—S2—C8—C9	−178.1 (5)
C3—C1—C2—C7	−0.6 (6)	S2—C8—C9—C10	−172.5 (5)
N1—C1—C3—S1	98.8 (4)	C8—C9—C10—O4	−57.8 (10)
C2—C1—C3—S1	−81.3 (5)	C8—C9—C10—O3	120.5 (9)
C4—S1—C3—C1	−72.6 (4)	C7—S2—C8B—C9B	−87.0 (16)
C3—S1—C4—C5	−86.7 (4)	S2—C8B—C9B—C10B	177 (2)
S1—C4—C5—C6	−65.0 (6)	C8B—C9B—C10B—O3B	−8 (5)
C4—C5—C6—O1	−17.0 (8)	C8B—C9B—C10B—O4B	−164 (3)
C4—C5—C6—O2	165.7 (6)

Symmetry code: (i) −x+2, −y+1, −z+1.

3,3',3'',3'''-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene))tetrakis(sulfanediyl]}tetrapropionic acid (H4L1B). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2O···O3ii	0.82	1.94	2.66 (1)	146
O2—H2O···O3Bii	0.82	2.20	2.77 (3)	127
O4—H4O···O1iii	0.82	1.88	2.66 (1)	158
O4B—H4OB···O1iii	0.82	1.86	2.67 (4)	170

Symmetry codes: (ii) x, y, z+1; (iii) x, y, z−1.

Poly[(µ-3-{[(3,5,6-tris{[(2-carboxyethyl)sulfanyl]methyl}pyrazin-2-yl)methyl]sulfanyl}propanoato)potassium] (KH3L1). Crystal data

[K(C20H27N2O8S4)]	F(000) = 1232
Mr = 590.77	Dx = 1.611 Mg m−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 30.080 (4) Å	Cell parameters from 7965 reflections
b = 8.4716 (10) Å	θ = 1.4–25.0°
c = 9.5908 (12) Å	µ = 0.61 mm−1
β = 94.717 (11)°	T = 153 K
V = 2435.7 (6) Å3	Plate, colourless
Z = 4	0.50 × 0.50 × 0.10 mm

Poly[(µ-3-{[(3,5,6-tris{[(2-carboxyethyl)sulfanyl]methyl}pyrazin-2-yl)methyl]sulfanyl}propanoato)potassium] (KH3L1). Data collection

STOE IPDS 2 diffractometer	2084 independent reflections
Radiation source: fine-focus sealed tube	1646 reflections with I > 2σ(I)
Plane graphite monochromator	Rint = 0.064
φ + ω scans	θmax = 24.8°, θmin = 2.5°
Absorption correction: multi-scan (MULABS; Spek, 2020)	h = −35→35
Tmin = 0.640, Tmax = 1.000	k = −9→9
10309 measured reflections	l = −11→11

Poly[(µ-3-{[(3,5,6-tris{[(2-carboxyethyl)sulfanyl]methyl}pyrazin-2-yl)methyl]sulfanyl}propanoato)potassium] (KH3L1). Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.039	Hydrogen site location: mixed
wR(F2) = 0.106	H atoms treated by a mixture of independent and constrained refinement
S = 1.02	w = 1/[σ2(Fo2) + (0.0648P)2 + 1.5958P] where P = (Fo2 + 2Fc2)/3
2084 reflections	(Δ/σ)max = 0.002
165 parameters	Δρmax = 0.26 e Å−3
0 restraints	Δρmin = −0.36 e Å−3

Poly[(µ-3-{[(3,5,6-tris{[(2-carboxyethyl)sulfanyl]methyl}pyrazin-2-yl)methyl]sulfanyl}propanoato)potassium] (KH3L1). Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Poly[(µ-3-{[(3,5,6-tris{[(2-carboxyethyl)sulfanyl]methyl}pyrazin-2-yl)methyl]sulfanyl}propanoato)potassium] (KH3L1). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
K1	0.500000	−0.28423 (13)	−0.250000	0.0357 (3)
S1	0.34409 (2)	−0.03261 (9)	0.17646 (7)	0.0305 (2)
S2	0.18978 (2)	−0.11089 (9)	0.16606 (8)	0.0342 (2)
O1	0.46781 (7)	−0.2235 (3)	0.0136 (2)	0.0404 (5)
O2	0.46330 (7)	−0.0466 (3)	0.1860 (2)	0.0402 (6)
H20	0.500000	−0.073 (9)	0.250000	0.12 (3)*
O3	0.06245 (6)	0.1153 (3)	−0.0544 (2)	0.0363 (5)
O4	0.03178 (7)	0.1057 (3)	0.1493 (2)	0.0472 (7)
H4O	0.0125 (17)	0.157 (7)	0.109 (5)	0.097 (19)*
N1	0.28457 (7)	0.2024 (3)	−0.0774 (2)	0.0240 (5)
C1	0.27160 (8)	0.1117 (3)	0.0267 (3)	0.0240 (6)
C2	0.23661 (8)	0.1606 (3)	0.1047 (3)	0.0229 (6)
C3	0.29578 (8)	−0.0422 (3)	0.0500 (3)	0.0280 (6)
H3A	0.305554	−0.079313	−0.040443	0.034*
H3B	0.274689	−0.121452	0.082227	0.034*
C4	0.38202 (9)	0.0765 (4)	0.0748 (3)	0.0352 (7)
H4A	0.364384	0.148969	0.010857	0.042*
H4B	0.401718	0.141946	0.139218	0.042*
C5	0.41100 (9)	−0.0265 (4)	−0.0116 (3)	0.0335 (7)
H5A	0.391756	−0.108161	−0.059355	0.040*
H5B	0.422744	0.040143	−0.084955	0.040*
C6	0.44979 (9)	−0.1079 (4)	0.0676 (3)	0.0326 (7)
C7	0.22055 (9)	0.0650 (3)	0.2220 (3)	0.0283 (6)
H7A	0.201211	0.132352	0.275893	0.034*
H7B	0.246620	0.033583	0.285664	0.034*
C8	0.14217 (9)	−0.0295 (4)	0.0628 (3)	0.0329 (7)
H8A	0.152427	0.055219	0.002031	0.039*
H8B	0.128312	−0.113189	0.001607	0.039*
C9	0.10744 (9)	0.0371 (4)	0.1528 (3)	0.0350 (7)
H9A	0.099826	−0.044379	0.220895	0.042*
H9B	0.120475	0.128185	0.206358	0.042*
C10	0.06542 (9)	0.0895 (4)	0.0702 (3)	0.0307 (7)

Poly[(µ-3-{[(3,5,6-tris{[(2-carboxyethyl)sulfanyl]methyl}pyrazin-2-yl)methyl]sulfanyl}propanoato)potassium] (KH3L1). Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
K1	0.0254 (4)	0.0547 (6)	0.0267 (5)	0.000	−0.0009 (3)	0.000
S1	0.0189 (3)	0.0428 (5)	0.0297 (4)	0.0034 (3)	0.0011 (3)	0.0042 (3)
S2	0.0224 (4)	0.0335 (4)	0.0466 (5)	−0.0003 (3)	0.0027 (3)	0.0034 (3)
O1	0.0302 (11)	0.0590 (15)	0.0320 (11)	0.0130 (10)	0.0022 (9)	−0.0023 (10)
O2	0.0246 (10)	0.0633 (15)	0.0319 (11)	0.0051 (10)	−0.0024 (9)	−0.0077 (10)
O3	0.0259 (10)	0.0554 (15)	0.0278 (11)	0.0021 (9)	0.0032 (8)	0.0038 (9)
O4	0.0266 (12)	0.0804 (19)	0.0356 (13)	0.0138 (12)	0.0085 (10)	0.0044 (12)
N1	0.0156 (10)	0.0304 (13)	0.0255 (12)	−0.0007 (9)	−0.0019 (9)	−0.0021 (10)
C1	0.0152 (12)	0.0299 (16)	0.0256 (14)	0.0007 (11)	−0.0048 (10)	−0.0038 (11)
C2	0.0159 (11)	0.0278 (15)	0.0239 (14)	−0.0009 (11)	−0.0036 (10)	−0.0026 (11)
C3	0.0187 (13)	0.0317 (16)	0.0331 (15)	0.0022 (11)	−0.0012 (11)	−0.0003 (12)
C4	0.0210 (13)	0.0424 (19)	0.0421 (18)	−0.0024 (13)	0.0018 (12)	0.0070 (14)
C5	0.0213 (13)	0.051 (2)	0.0280 (15)	−0.0009 (12)	0.0017 (12)	0.0039 (13)
C6	0.0185 (13)	0.053 (2)	0.0268 (15)	−0.0019 (13)	0.0047 (11)	0.0024 (14)
C7	0.0229 (14)	0.0366 (16)	0.0251 (14)	−0.0005 (12)	0.0013 (11)	0.0024 (12)
C8	0.0224 (14)	0.0422 (19)	0.0338 (16)	−0.0034 (12)	0.0011 (12)	−0.0009 (13)
C9	0.0208 (14)	0.056 (2)	0.0280 (15)	0.0017 (13)	0.0037 (12)	0.0032 (14)
C10	0.0217 (13)	0.0388 (18)	0.0321 (16)	−0.0033 (12)	0.0052 (12)	−0.0013 (13)

Poly[(µ-3-{[(3,5,6-tris{[(2-carboxyethyl)sulfanyl]methyl}pyrazin-2-yl)methyl]sulfanyl}propanoato)potassium] (KH3L1). Geometric parameters (Å, º)

K1—O1	2.828 (2)	C1—C2	1.403 (4)
K1—O1i	2.828 (2)	C1—C3	1.501 (4)
K1—O2ii	3.056 (3)	C2—C7	1.498 (4)
K1—O2iii	3.056 (3)	C3—H3A	0.9900
K1—O3iv	2.682 (2)	C3—H3B	0.9900
K1—O3v	2.682 (2)	C4—C5	1.525 (4)
K1—O4vi	3.069 (3)	C4—H4A	0.9900
K1—O4vii	3.069 (3)	C4—H4B	0.9900
S1—C4	1.814 (3)	C5—C6	1.506 (4)
S1—C3	1.816 (3)	C5—H5A	0.9900
S2—C8	1.809 (3)	C5—H5B	0.9900
S2—C7	1.812 (3)	C7—H7A	0.9900
O1—C6	1.252 (4)	C7—H7B	0.9900
O2—C6	1.284 (4)	C8—C9	1.517 (4)
O2—H20	1.239 (15)	C8—H8A	0.9900
O3—C10	1.211 (3)	C8—H8B	0.9900
O4—C10	1.321 (3)	C9—C10	1.502 (4)
O4—H4O	0.80 (5)	C9—H9A	0.9900
N1—C2viii	1.339 (4)	C9—H9B	0.9900
N1—C1	1.343 (4)
O3iv—K1—O3v	143.00 (11)	C1—C2—C7	122.9 (3)
O3iv—K1—O1	114.30 (6)	C1—C3—S1	114.31 (19)
O3v—K1—O1	72.78 (6)	C1—C3—H3A	108.7
O3iv—K1—O1i	72.78 (6)	S1—C3—H3A	108.7
O3v—K1—O1i	114.30 (6)	C1—C3—H3B	108.7
O1—K1—O1i	159.05 (11)	S1—C3—H3B	108.7
O3iv—K1—O2ii	130.71 (7)	H3A—C3—H3B	107.6
O3v—K1—O2ii	85.98 (6)	C5—C4—S1	114.4 (2)
O1—K1—O2ii	78.37 (7)	C5—C4—H4A	108.7
O1i—K1—O2ii	82.42 (6)	S1—C4—H4A	108.7
O3iv—K1—O2iii	85.98 (6)	C5—C4—H4B	108.7
O3v—K1—O2iii	130.71 (7)	S1—C4—H4B	108.7
O1—K1—O2iii	82.42 (6)	H4A—C4—H4B	107.6
O1i—K1—O2iii	78.37 (7)	C6—C5—C4	116.2 (2)
O2ii—K1—O2iii	46.99 (8)	C6—C5—H5A	108.2
O3iv—K1—O4vi	73.54 (7)	C4—C5—H5A	108.2
O3v—K1—O4vi	73.75 (7)	C6—C5—H5B	108.2
O1—K1—O4vi	125.54 (7)	C4—C5—H5B	108.2
O1i—K1—O4vi	75.02 (7)	H5A—C5—H5B	107.4
O2ii—K1—O4vi	139.50 (6)	O1—C6—O2	124.5 (3)
O2iii—K1—O4vi	150.17 (6)	O1—C6—C5	119.6 (3)
O3iv—K1—O4vii	73.75 (7)	O2—C6—C5	115.9 (3)
O3v—K1—O4vii	73.54 (7)	C2—C7—S2	114.24 (19)
O1—K1—O4vii	75.02 (7)	C2—C7—H7A	108.7
O1i—K1—O4vii	125.54 (7)	S2—C7—H7A	108.7
O2ii—K1—O4vii	150.17 (6)	C2—C7—H7B	108.7
O2iii—K1—O4vii	139.50 (6)	S2—C7—H7B	108.7
O4vi—K1—O4vii	54.87 (9)	H7A—C7—H7B	107.6
C4—S1—C3	99.68 (14)	C9—C8—S2	112.4 (2)
C8—S2—C7	102.17 (14)	C9—C8—H8A	109.1
C6—O1—K1	134.73 (19)	S2—C8—H8A	109.1
C6—O2—K1ii	129.17 (19)	C9—C8—H8B	109.1
C6—O2—H20	125 (2)	S2—C8—H8B	109.1
K1ii—O2—H20	77 (4)	H8A—C8—H8B	107.9
C10—O3—K1ix	137.58 (18)	C10—C9—C8	113.5 (2)
C10—O4—K1vii	111.2 (2)	C10—C9—H9A	108.9
C10—O4—H4O	110 (4)	C8—C9—H9A	108.9
K1vii—O4—H4O	114 (4)	C10—C9—H9B	108.9
C2viii—N1—C1	118.6 (2)	C8—C9—H9B	108.9
N1—C1—C2	120.3 (2)	H9A—C9—H9B	107.7
N1—C1—C3	116.2 (2)	O3—C10—O4	123.4 (3)
C2—C1—C3	123.5 (2)	O3—C10—C9	124.3 (2)
N1viii—C2—C1	121.1 (2)	O4—C10—C9	112.3 (2)
N1viii—C2—C7	116.0 (2)
C2viii—N1—C1—C2	−0.1 (4)	K1ii—O2—C6—C5	−60.6 (3)
C2viii—N1—C1—C3	178.5 (2)	C4—C5—C6—O1	161.6 (3)
N1—C1—C2—N1viii	0.1 (4)	C4—C5—C6—O2	−21.4 (4)
C3—C1—C2—N1viii	−178.4 (2)	N1viii—C2—C7—S2	107.9 (2)
N1—C1—C2—C7	180.0 (2)	C1—C2—C7—S2	−72.0 (3)
C3—C1—C2—C7	1.5 (4)	C8—S2—C7—C2	−62.3 (2)
N1—C1—C3—S1	91.6 (3)	C7—S2—C8—C9	−77.5 (2)
C2—C1—C3—S1	−89.8 (3)	S2—C8—C9—C10	−173.8 (2)
C4—S1—C3—C1	−72.3 (2)	K1ix—O3—C10—O4	1.7 (5)
C3—S1—C4—C5	−90.3 (2)	K1ix—O3—C10—C9	−177.7 (2)
S1—C4—C5—C6	−76.4 (3)	K1vii—O4—C10—O3	110.5 (3)
K1—O1—C6—O2	−127.8 (3)	K1vii—O4—C10—C9	−70.0 (3)
K1—O1—C6—C5	48.8 (4)	C8—C9—C10—O3	−17.9 (5)
K1ii—O2—C6—O1	116.1 (3)	C8—C9—C10—O4	162.6 (3)

Symmetry codes: (i) −x+1, y, −z−1/2; (ii) −x+1, −y, −z; (iii) x, −y, z−1/2; (iv) −x+1/2, y−1/2, −z−1/2; (v) x+1/2, y−1/2, z; (vi) x+1/2, −y−1/2, z−1/2; (vii) −x+1/2, −y−1/2, −z; (viii) −x+1/2, −y+1/2, −z; (ix) x−1/2, y+1/2, z.

Poly[(µ-3-{[(3,5,6-tris{[(2-carboxyethyl)sulfanyl]methyl}pyrazin-2-yl)methyl]sulfanyl}propanoato)potassium] (KH3L1). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O4—H4O···O1ix	0.80 (5)	1.86 (5)	2.661 (3)	180 (7)
O2—H20···O2x	1.24 (1)	1.24 (1)	2.436 (3)	159 (7)
C4—H4A···N1	0.99	2.52	3.340 (4)	140
C4—H4B···O3viii	0.99	2.49	3.114 (4)	121
C5—H5B···O2iii	0.99	2.60	3.467 (4)	146
C7—H7B···N1xi	0.99	2.60	3.454 (4)	144
C9—H9A···O3xi	0.99	2.58	3.465 (4)	149

Symmetry codes: (iii) x, −y, z−1/2; (viii) −x+1/2, −y+1/2, −z; (ix) x−1/2, y+1/2, z; (x) −x+1, y, −z+1/2; (xi) x, −y, z+1/2.

Poly[(µ-3,3'-{[(3,6-bis{[(2-carboxyethyl)sulfanyl]methyl}pyrazine-2,5-diyl)bis(methylene)]bis(sulfanediyl)}dipropionato)dipotassium] (K2H2L1). Crystal data

[K2(C20H26N2O8S4)]	F(000) = 1304
Mr = 628.87	Dx = 1.602 Mg m−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 27.908 (2) Å	Cell parameters from 20250 reflections
b = 8.2916 (6) Å	θ = 1.8–29.6°
c = 11.3035 (9) Å	µ = 0.73 mm−1
β = 94.753 (6)°	T = 153 K
V = 2606.7 (3) Å3	Plate, colourless
Z = 4	0.50 × 0.50 × 0.05 mm

Poly[(µ-3,3'-{[(3,6-bis{[(2-carboxyethyl)sulfanyl]methyl}pyrazine-2,5-diyl)bis(methylene)]bis(sulfanediyl)}dipropionato)dipotassium] (K2H2L1). Data collection

STOE IPDS 2 diffractometer	3646 independent reflections
Radiation source: fine-focus sealed tube	3175 reflections with I > 2σ(I)
Plane graphite monochromator	Rint = 0.042
φ + ω scans	θmax = 29.6°, θmin = 2.6°
Absorption correction: empirical (using intensity measurements) (ShxAbs; Spek, 2020)	h = −38→38
Tmin = 0.416, Tmax = 0.803	k = −11→11
19423 measured reflections	l = −15→15

Poly[(µ-3,3'-{[(3,6-bis{[(2-carboxyethyl)sulfanyl]methyl}pyrazine-2,5-diyl)bis(methylene)]bis(sulfanediyl)}dipropionato)dipotassium] (K2H2L1). Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.037	Hydrogen site location: mixed
wR(F2) = 0.103	H atoms treated by a mixture of independent and constrained refinement
S = 1.05	w = 1/[σ2(Fo2) + (0.0541P)2 + 3.5192P] where P = (Fo2 + 2Fc2)/3
3646 reflections	(Δ/σ)max < 0.001
167 parameters	Δρmax = 0.76 e Å−3
1 restraint	Δρmin = −0.51 e Å−3

Poly[(µ-3,3'-{[(3,6-bis{[(2-carboxyethyl)sulfanyl]methyl}pyrazine-2,5-diyl)bis(methylene)]bis(sulfanediyl)}dipropionato)dipotassium] (K2H2L1). Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Poly[(µ-3,3'-{[(3,6-bis{[(2-carboxyethyl)sulfanyl]methyl}pyrazine-2,5-diyl)bis(methylene)]bis(sulfanediyl)}dipropionato)dipotassium] (K2H2L1). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
K1	0.000000	0.82906 (7)	0.750000	0.02908 (13)
K2	0.000000	0.64758 (6)	0.250000	0.02585 (12)
S1	0.15530 (2)	0.94369 (6)	0.36528 (5)	0.03200 (12)
S2	0.31454 (2)	0.91861 (6)	0.30731 (4)	0.02972 (12)
O1	0.03202 (5)	0.90961 (16)	0.37679 (12)	0.0288 (3)
O2	0.03173 (4)	0.75961 (15)	0.53962 (10)	0.0251 (2)
O3	0.44445 (5)	1.07891 (16)	0.64145 (11)	0.0264 (3)
O4	0.45504 (4)	1.14483 (16)	0.45457 (11)	0.0246 (2)
H4O	0.4811 (7)	1.187 (3)	0.485 (2)	0.037*
N1	0.22122 (5)	1.18192 (18)	0.58094 (13)	0.0226 (3)
C1	0.23166 (6)	1.10103 (19)	0.48370 (15)	0.0214 (3)
C2	0.26072 (6)	1.1694 (2)	0.40166 (14)	0.0214 (3)
C3	0.20952 (6)	0.9373 (2)	0.46641 (17)	0.0261 (3)
H3A	0.201509	0.894439	0.544105	0.031*
H3B	0.233073	0.863252	0.434300	0.031*
C4	0.11775 (7)	1.0635 (2)	0.4543 (2)	0.0344 (4)
H4A	0.138286	1.142471	0.500499	0.041*
H4B	0.094632	1.125024	0.400576	0.041*
C5	0.08989 (6)	0.9666 (2)	0.53952 (18)	0.0301 (4)
H5A	0.112007	0.889825	0.583250	0.036*
H5B	0.077277	1.040676	0.598231	0.036*
C6	0.04848 (6)	0.8740 (2)	0.47738 (14)	0.0215 (3)
C7	0.27238 (6)	1.0859 (2)	0.28997 (15)	0.0260 (3)
H7A	0.285609	1.166910	0.237196	0.031*
H7B	0.241998	1.045256	0.249183	0.031*
C8	0.37036 (6)	1.0182 (3)	0.35882 (16)	0.0295 (4)
H8A	0.397073	0.966995	0.320275	0.035*
H8B	0.368597	1.132425	0.333262	0.035*
C9	0.38174 (6)	1.0126 (2)	0.49202 (15)	0.0243 (3)
H9A	0.380284	0.899037	0.518480	0.029*
H9B	0.356583	1.073093	0.530128	0.029*
C10	0.43036 (6)	1.08130 (19)	0.53492 (14)	0.0216 (3)

Poly[(µ-3,3'-{[(3,6-bis{[(2-carboxyethyl)sulfanyl]methyl}pyrazine-2,5-diyl)bis(methylene)]bis(sulfanediyl)}dipropionato)dipotassium] (K2H2L1). Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
K1	0.0442 (3)	0.0240 (2)	0.0186 (2)	0.000	−0.0001 (2)	0.000
K2	0.0356 (3)	0.0230 (2)	0.0189 (2)	0.000	0.00191 (18)	0.000
S1	0.0250 (2)	0.0304 (2)	0.0399 (3)	−0.00503 (16)	−0.00202 (17)	−0.00557 (18)
S2	0.0236 (2)	0.0297 (2)	0.0355 (2)	−0.00158 (16)	0.00042 (16)	−0.00746 (17)
O1	0.0311 (6)	0.0272 (6)	0.0269 (6)	−0.0064 (5)	−0.0040 (5)	0.0023 (5)
O2	0.0235 (5)	0.0282 (6)	0.0233 (5)	−0.0027 (5)	0.0009 (4)	0.0005 (5)
O3	0.0276 (6)	0.0300 (6)	0.0217 (5)	−0.0011 (5)	0.0019 (4)	0.0021 (5)
O4	0.0228 (5)	0.0299 (6)	0.0212 (5)	−0.0051 (5)	0.0024 (4)	0.0004 (5)
N1	0.0196 (6)	0.0235 (6)	0.0242 (6)	−0.0010 (5)	−0.0004 (5)	0.0030 (5)
C1	0.0173 (6)	0.0206 (7)	0.0256 (7)	−0.0002 (5)	−0.0027 (5)	0.0020 (6)
C2	0.0183 (7)	0.0230 (7)	0.0223 (7)	0.0002 (5)	−0.0022 (5)	0.0019 (6)
C3	0.0214 (7)	0.0213 (7)	0.0353 (9)	−0.0017 (6)	0.0007 (6)	0.0016 (6)
C4	0.0220 (8)	0.0231 (8)	0.0576 (12)	−0.0023 (6)	−0.0009 (8)	−0.0060 (8)
C5	0.0230 (8)	0.0295 (9)	0.0368 (9)	−0.0023 (6)	−0.0035 (7)	−0.0092 (7)
C6	0.0180 (7)	0.0212 (7)	0.0250 (7)	0.0004 (5)	0.0006 (5)	−0.0046 (6)
C7	0.0250 (8)	0.0290 (8)	0.0237 (7)	−0.0007 (6)	−0.0005 (6)	−0.0005 (6)
C8	0.0211 (7)	0.0402 (10)	0.0271 (8)	−0.0049 (7)	0.0021 (6)	−0.0020 (7)
C9	0.0218 (7)	0.0250 (8)	0.0261 (7)	−0.0017 (6)	0.0025 (6)	−0.0010 (6)
C10	0.0224 (7)	0.0205 (7)	0.0220 (7)	0.0019 (5)	0.0031 (6)	−0.0003 (5)

Poly[(µ-3,3'-{[(3,6-bis{[(2-carboxyethyl)sulfanyl]methyl}pyrazine-2,5-diyl)bis(methylene)]bis(sulfanediyl)}dipropionato)dipotassium] (K2H2L1). Geometric parameters (Å, º)

K1—O1i	2.7084 (14)	O1—C6	1.227 (2)
K1—O1ii	2.7084 (14)	O4—C10	1.296 (2)
K1—O2	2.6682 (12)	O4—H4O	0.855 (16)
K1—O2iii	2.6683 (12)	O3—C10	1.236 (2)
K1—O3iv	2.8099 (14)	N1—C1	1.340 (2)
K1—O3v	2.8099 (13)	N1—C2xi	1.341 (2)
K1—C6iii	3.4864 (17)	C1—C2	1.401 (2)
K1—C6	3.4865 (17)	C1—C3	1.498 (2)
K1—K2vi	3.9521 (8)	C2—C7	1.499 (2)
K1—K2ii	4.3395 (8)	C3—H3A	0.9900
K2—O1vii	2.7131 (13)	C3—H3B	0.9900
K2—O1	2.7132 (13)	C4—C5	1.518 (3)
K2—O3viii	2.6683 (13)	C4—H4A	0.9900
K2—O3ix	2.6682 (13)	C4—H4B	0.9900
K2—O4x	2.7209 (12)	C5—C6	1.511 (2)
K2—O4iv	2.7209 (12)	C5—H5A	0.9900
K2—C6vii	3.3739 (16)	C5—H5B	0.9900
K2—C6	3.3739 (16)	C7—H7A	0.9900
K2—C10viii	3.5364 (16)	C7—H7B	0.9900
K2—C10ix	3.5364 (16)	C8—C9	1.513 (2)
S1—C4	1.809 (2)	C8—H8A	0.9900
S1—C3	1.8200 (18)	C8—H8B	0.9900
S2—C8	1.8159 (18)	C9—C10	1.514 (2)
S2—C7	1.8190 (19)	C9—H9A	0.9900
O2—C6	1.291 (2)	C9—H9B	0.9900
O2—K1—O2iii	155.07 (6)	O3ix—K2—K1vi	45.27 (3)
O2—K1—O1i	121.67 (4)	O1vii—K2—K1vi	143.21 (3)
O2iii—K1—O1i	79.65 (4)	O1—K2—K1vi	143.21 (3)
O2—K1—O1ii	79.65 (4)	O4x—K2—K1vi	89.52 (3)
O2iii—K1—O1ii	121.67 (4)	O4iv—K2—K1vi	89.52 (3)
O1i—K1—O1ii	73.73 (6)	C6vii—K2—K1vi	123.80 (3)
O2—K1—O3iv	70.32 (4)	C6—K2—K1vi	123.80 (3)
O2iii—K1—O3iv	91.03 (4)	C10viii—K2—K1vi	57.55 (3)
O1i—K1—O3iv	165.36 (4)	C10ix—K2—K1vi	57.55 (3)
O1ii—K1—O3iv	102.33 (4)	O3viii—K2—K1ii	134.73 (3)
O2—K1—O3v	91.03 (4)	O3ix—K2—K1ii	134.73 (3)
O2iii—K1—O3v	70.32 (4)	O1vii—K2—K1ii	36.79 (3)
O1i—K1—O3v	102.33 (4)	O1—K2—K1ii	36.79 (3)
O1ii—K1—O3v	165.36 (4)	O4x—K2—K1ii	90.48 (3)
O3iv—K1—O3v	84.85 (5)	O4iv—K2—K1ii	90.48 (3)
O2—K1—C6iii	172.97 (4)	C6vii—K2—K1ii	56.20 (3)
O2iii—K1—C6iii	18.84 (4)	C6—K2—K1ii	56.20 (3)
O1i—K1—C6iii	65.30 (4)	C10viii—K2—K1ii	122.45 (3)
O1ii—K1—C6iii	104.31 (4)	C10ix—K2—K1ii	122.45 (3)
O3iv—K1—C6iii	102.96 (4)	K1vi—K2—K1ii	180.0
O3v—K1—C6iii	86.17 (4)	C4—S1—C3	99.00 (9)
O2—K1—C6	18.84 (4)	C8—S2—C7	102.58 (9)
O2iii—K1—C6	172.97 (4)	C6—O2—K1	119.28 (10)
O1i—K1—C6	104.31 (4)	C6—O1—K1ii	139.92 (11)
O1ii—K1—C6	65.30 (4)	C6—O1—K2	112.22 (11)
O3iv—K1—C6	86.17 (4)	K1ii—O1—K2	106.34 (4)
O3v—K1—C6	102.96 (4)	C10—O4—K2xii	155.24 (11)
C6iii—K1—C6	167.74 (6)	C10—O4—H4O	111.3 (17)
O2—K1—K2vi	77.54 (3)	K2xii—O4—H4O	84.7 (17)
O2iii—K1—K2vi	77.54 (3)	C10—O3—K2ix	125.83 (11)
O1i—K1—K2vi	143.13 (3)	C10—O3—K1xii	122.23 (11)
O1ii—K1—K2vi	143.13 (3)	K2ix—O3—K1xii	92.31 (4)
O3iv—K1—K2vi	42.42 (3)	C1—N1—C2xi	118.43 (14)
O3v—K1—K2vi	42.42 (3)	N1—C1—C2	121.17 (15)
C6iii—K1—K2vi	96.13 (3)	N1—C1—C3	116.44 (15)
C6—K1—K2vi	96.13 (3)	C2—C1—C3	122.37 (15)
O2—K1—K2ii	102.46 (3)	N1xi—C2—C1	120.40 (15)
O2iii—K1—K2ii	102.46 (3)	N1xi—C2—C7	116.30 (15)
O1i—K1—K2ii	36.87 (3)	C1—C2—C7	123.28 (15)
O1ii—K1—K2ii	36.87 (3)	C1—C3—S1	111.60 (12)
O3iv—K1—K2ii	137.58 (3)	C1—C3—H3A	109.3
O3v—K1—K2ii	137.58 (3)	S1—C3—H3A	109.3
C6iii—K1—K2ii	83.87 (3)	C1—C3—H3B	109.3
C6—K1—K2ii	83.87 (3)	S1—C3—H3B	109.3
K2vi—K1—K2ii	180.0	H3A—C3—H3B	108.0
O3viii—K2—O3ix	90.54 (6)	C5—C4—S1	114.41 (14)
O3viii—K2—O1vii	99.63 (4)	C5—C4—H4A	108.7
O3ix—K2—O1vii	163.72 (4)	S1—C4—H4A	108.7
O3viii—K2—O1	163.72 (4)	C5—C4—H4B	108.7
O3ix—K2—O1	99.63 (4)	S1—C4—H4B	108.7
O1vii—K2—O1	73.59 (6)	H4A—C4—H4B	107.6
O3viii—K2—O4x	83.95 (4)	C6—C5—C4	112.73 (16)
O3ix—K2—O4x	95.38 (4)	C6—C5—H5A	109.0
O1vii—K2—O4x	73.30 (4)	C4—C5—H5A	109.0
O1—K2—O4x	107.50 (4)	C6—C5—H5B	109.0
O3viii—K2—O4iv	95.38 (4)	C4—C5—H5B	109.0
O3ix—K2—O4iv	83.95 (4)	H5A—C5—H5B	107.8
O1vii—K2—O4iv	107.50 (4)	O1—C6—O2	123.88 (15)
O1—K2—O4iv	73.30 (4)	O1—C6—C5	121.42 (16)
O4x—K2—O4iv	179.04 (6)	O2—C6—C5	114.67 (15)
O3viii—K2—C6vii	81.96 (4)	O1—C6—K2	48.11 (8)
O3ix—K2—C6vii	157.35 (4)	O2—C6—K2	82.31 (9)
O1vii—K2—C6vii	19.67 (4)	C5—C6—K2	151.60 (11)
O1—K2—C6vii	92.90 (4)	O1—C6—K1	134.60 (11)
O4x—K2—C6vii	62.69 (4)	O2—C6—K1	41.88 (8)
O4iv—K2—C6vii	117.91 (4)	C5—C6—K1	88.93 (10)
O3viii—K2—C6	157.35 (4)	K2—C6—K1	116.96 (5)
O3ix—K2—C6	81.96 (4)	C2—C7—S2	116.42 (12)
O1vii—K2—C6	92.90 (4)	C2—C7—H7A	108.2
O1—K2—C6	19.67 (4)	S2—C7—H7A	108.2
O4x—K2—C6	117.91 (4)	C2—C7—H7B	108.2
O4iv—K2—C6	62.69 (4)	S2—C7—H7B	108.2
C6vii—K2—C6	112.40 (6)	H7A—C7—H7B	107.3
O3viii—K2—C10viii	16.46 (4)	C9—C8—S2	114.13 (13)
O3ix—K2—C10viii	101.75 (4)	C9—C8—H8A	108.7
O1vii—K2—C10viii	85.89 (4)	S2—C8—H8A	108.7
O1—K2—C10viii	158.61 (4)	C9—C8—H8B	108.7
O4x—K2—C10viii	71.16 (4)	S2—C8—H8B	108.7
O4iv—K2—C10viii	108.29 (4)	H8A—C8—H8B	107.6
C6vii—K2—C10viii	67.17 (4)	C8—C9—C10	114.57 (14)
C6—K2—C10viii	170.09 (4)	C8—C9—H9A	108.6
O3viii—K2—C10ix	101.75 (4)	C10—C9—H9A	108.6
O3ix—K2—C10ix	16.46 (4)	C8—C9—H9B	108.6
O1vii—K2—C10ix	158.61 (4)	C10—C9—H9B	108.6
O1—K2—C10ix	85.89 (4)	H9A—C9—H9B	107.6
O4x—K2—C10ix	108.29 (4)	O3—C10—O4	122.99 (16)
O4iv—K2—C10ix	71.16 (4)	O3—C10—C9	120.71 (15)
C6vii—K2—C10ix	170.09 (4)	O4—C10—C9	116.27 (14)
C6—K2—C10ix	67.17 (4)	O3—C10—K2ix	37.72 (8)
C10viii—K2—C10ix	115.09 (5)	O4—C10—K2ix	113.96 (10)
O3viii—K2—K1vi	45.27 (3)	C9—C10—K2ix	116.44 (10)
C2xi—N1—C1—C2	0.0 (2)	C4—C5—C6—O1	−18.7 (2)
C2xi—N1—C1—C3	−178.32 (14)	C4—C5—C6—O2	162.94 (15)
N1—C1—C2—N1xi	0.0 (3)	C4—C5—C6—K2	40.3 (3)
C3—C1—C2—N1xi	178.22 (14)	C4—C5—C6—K1	−162.96 (14)
N1—C1—C2—C7	−178.30 (15)	N1xi—C2—C7—S2	108.63 (15)
C3—C1—C2—C7	−0.1 (2)	C1—C2—C7—S2	−72.98 (19)
N1—C1—C3—S1	97.64 (16)	C8—S2—C7—C2	−67.34 (15)
C2—C1—C3—S1	−80.62 (18)	C7—S2—C8—C9	97.89 (15)
C4—S1—C3—C1	−65.81 (15)	S2—C8—C9—C10	174.51 (12)
C3—S1—C4—C5	−87.72 (15)	K2ix—O3—C10—O4	−87.24 (18)
S1—C4—C5—C6	−73.29 (18)	K1xii—O3—C10—O4	33.7 (2)
K1ii—O1—C6—O2	128.23 (16)	K2ix—O3—C10—C9	94.51 (17)
K2—O1—C6—O2	−35.0 (2)	K1xii—O3—C10—C9	−144.57 (12)
K1ii—O1—C6—C5	−49.9 (3)	K1xii—O3—C10—K2ix	120.92 (16)
K2—O1—C6—C5	146.80 (13)	K2xii—O4—C10—O3	125.1 (2)
K1ii—O1—C6—K2	163.2 (2)	K2xii—O4—C10—C9	−56.6 (3)
K1ii—O1—C6—K1	74.9 (2)	K2xii—O4—C10—K2ix	83.1 (3)
K2—O1—C6—K1	−88.34 (15)	C8—C9—C10—O3	−177.68 (16)
K1—O2—C6—O1	−121.20 (15)	C8—C9—C10—O4	3.9 (2)
K1—O2—C6—C5	57.09 (17)	C8—C9—C10—K2ix	−134.75 (13)
K1—O2—C6—K2	−146.73 (7)

Symmetry codes: (i) x, −y+2, z+1/2; (ii) −x, −y+2, −z+1; (iii) −x, y, −z+3/2; (iv) x−1/2, y−1/2, z; (v) −x+1/2, y−1/2, −z+3/2; (vi) −x, −y+1, −z+1; (vii) −x, y, −z+1/2; (viii) x−1/2, −y+3/2, z−1/2; (ix) −x+1/2, −y+3/2, −z+1; (x) −x+1/2, y−1/2, −z+1/2; (xi) −x+1/2, −y+5/2, −z+1; (xii) x+1/2, y+1/2, z.

Poly[(µ-3,3'-{[(3,6-bis{[(2-carboxyethyl)sulfanyl]methyl}pyrazine-2,5-diyl)bis(methylene)]bis(sulfanediyl)}dipropionato)dipotassium] (K2H2L1). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O4—H4O···O2xii	0.85 (2)	1.61 (2)	2.4637 (16)	177 (3)
C4—H4A···N1	0.99	2.44	3.266 (2)	141
C8—H8A···O3xiii	0.99	2.53	3.436 (2)	151

Symmetry codes: (xii) x+1/2, y+1/2, z; (xiii) x, −y+2, z−1/2.

Funding Statement

This work was funded by Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung grant . Université de Neuchâtel grant .