Synthesis, crystal structure and Hirshfeld surface analysis of bis­(1H-benzimidazole-κN³)bis(benzimidazole-2-carboxyl­ato-κ²N³,O)cobalt(II)

The cobalt(II) complex, [C₃₀H₂₂CoN₈O₄], crystallizes in the monoclinic space group P2₁/c, with the Co⁺² ion adopting an octa­hedral coordination environment. The crystal structure features N—H⋯O hydrogen bonds and C—H⋯π contacts forming a chain along [011]. Hirshfeld surface analysis indicates that H⋯C/C⋯H and H⋯H contacts dominate the inter­molecular inter­actions.

Abstract

The title complex, [Co(C₈H₅N₂O₂)₂(C₇H₆N₂)₂], crystallizes in the monoclinic space group P2₁/c with one-half of the mol­ecule in the asymmetric unit. The Co²⁺ ion exhibits a distorted octa­hedral environment formed by two monodentate benzimidazole ligands and two bidentate benzimidazole-2-carboxyl­ate ligands. The crystal packing features N—H⋯O hydrogen bonds and C—H⋯π contacts, which generate a chain along [011]. Hirshfeld surface analysis shows that H⋯C/C⋯H (36.2%) and H⋯H (35.3%) contacts dominate the inter­molecular inter­actions, followed by O⋯H/H⋯O and N⋯H/H⋯N contributions.

1. Chemical context

Benzimidazole is an aromatic heterocyclic ligand containing two nitro­gen atoms in a five-membered fragment: one can serve as a coordination donor, while the second bears a proton (N—H) and is capable of forming directional hydrogen bonds, which determines its behavior in complexation (Walia et al., 2011 ▸). Thanks to its delocalized π-system, benzimidazole is prone to π–π and C—H⋯π inter­actions, which significantly influence crystal packing and the inter­molecular interactions in complexes (Keri et al., 2015 ▸). Electron-donating or -accepting substituents on the benzene or imidazole ring markedly alter the nitrogen donor character, enabling tuning of the metal-center electron density, stabilization of particular oxidation states and modification of the coordination geometry (Bansal & Silakari, 2012 ▸). Benzimidazole derivatives demonstrate a wide spectrum of biological activities and are therefore frequently used in the development of bioactive mol­ecules and pharmaceutical candidates (Singh et al., 2012 ▸). Taken together, these features make benzimidazole a versatile and readily modifiable building block for the synthesis of functional coordination complexes.

Benzimidazole-2-carb­oxy­lic acid is a benzimidazole functionalized at the 2-position with a carboxyl group, which imparts additional acidic and coordination activity to the mol­ecule. Classical methods for its preparation and reactions are described in detail by Copeland & Day (1943 ▸). Derivatives of benzimidazole-2-carb­oxy­lic acid exhibit pharmacological activity, including anti-inflammatory effects, and their synthetic modifications have been explored to obtain bioactive compounds (Thakurdesai et al., 2007 ▸). The carboxyl function enables the formation of carboxyl­ate coordination and bridging between metals, as well as directional O—H⋯A and N—H⋯O hydrogen bonds, which substanti­ally affect crystal packing, complex stabilization, and their chemical properties (Doring et al., 1997 ▸).

In this context, we synthesized the title complex [Co(C₈H₅N₂O₂)₂(C₇H₆N₂)₂], (I). This work provides an analysis of the structural and supra­molecular properties and of the Hirshfeld surface.

2. Structural commentary

The structure of (I) crystallized in space group P2₁/c with half a molecule in the asymmetric unit (Fig. 1 ▸). The central Co^II atom (site symmetry ) is coordinated by four ligands and has a coordination number of six; two of these are neutral benzimidazole molecules (BI), coordinated monodentately through an sp² nitro­gen atom [Co—N3 = 2.162 (5) Å]. The other two ligands are benzimidazole-2-carb­oxy­late anions (BICA), which acts as a bidentate ligand and coordinates via the carboxyl­ate oxygen atom [Co—O1 = 2.128 (4) Å] and the sp² nitro­gen atom [Co—N1 = 2.101 (5) Å] of the imidazole ring (Table 1 ▸). The BICA ligand forms a five-membered chelate ring, with a chelate angle N1—Co1—O1 = 79.00 (18)° (Table 1 ▸). The coordination environment around the central Co²⁺ ion is distorted n octa­hedron (4 + 2), with four shorter equatorial Co—N/O bonds and two longer axial Co—N/O bonds. The metal–ligand distances range from 2.101 (5) to 2.162 (5) Å, which is consistent with a Co²⁺ oxidation state, since Co³⁺ typically exhibits shorter bond lengths (≈1.8–2.0 Å), especially to oxygen atoms (Heffern et al., 2015 ▸; Tojiboyeva et al., 2025 ▸). The bond-valence sum calculated for Co1 is 1.94 v.u., further supporting the assignment of the +2 oxidation state. The BI and BICA ligands are not coplanar: the dihedral angle between their least-squares (mean) planes in the asymmetric unit is 81.7(4)°, a pronounced non-coplan­arity that may influence the molecular geometry and crystal packing.

Figure 1.

Molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level. Only atoms of the asymmetric unit are labelled; the remaining atoms are generated by the symmetry operation −x, −y, −;z.

Table 1. Selected geometric parameters (Å, °).

Co1—O1	2.128 (4)	Co1—N1	2.101 (5)
Co1—N3	2.162 (5)
N1—Co1—O1	79.00 (18)	N1—Co1—N3	88.9 (2)

Structural data for the obtained complex were compared with a related synthesized complex (Döring et al., 1997 ▸) in which the coordination environment includes benzimidazole and quinaldinate ligands. The cobalt atom in that structure also lies on an inversion centre but the five-membered chelate ring formed by the quinaldinate ligand has a bite angle of 77.52°, which is 1.5° smaller than in the present complex. This difference can be attributed to ligand flexibility, stereochemical factors (including variations in the chelate-ring conformation, metal–ligand bond distances and the relative orientation of donor atoms), as well as crystal packing effects. Axial bond lengths reported for that complex are Co—N1 = 2.174 (3) Å for the two benzimidazole ligands, compared with Co—N3 = 2.162 (5) Å in our complex. Equatorial bond lengths in the referenced complex are Co—O1 = 2.051 (2) Å and Co—N3 = 2.218 (2) Å, whereas the corresponding values in our complex are 2.128 (4) and 2.101 (5) Å, respectively. Such pronounced differences in the equatorial plane most likely reflect variations in the donor strengths and conformations of the respective ligands (different electron densities on the O and N donors), as well as the influence of the bite angle and crystal-packing effects (hydrogen bonds and C—H⋯π contacts), which can further ‘stretch’ or ‘compress’ individual bonds.

3. Supra­molecular features

In the crystal, pairs of N—H⋯O hydrogen bonds link adjacent BICA ligands: N2—H2⋯O2ⁱⁱ [symmetry code: (ii) −x, −y + 1, −z + 1] and N4—H4⋯O1ⁱⁱⁱ [and the bifurcated contact N4—H4⋯O2ⁱⁱⁱ; symmetry code: (iii) −x + 1, y − , −z + ]. These pairs connect mol­ecules into a chain running along the crystallographic [100] direction (Fig. 2 ▸a). In addition to the classical N—H⋯O inter­actions, a C—H⋯π contact [C12—H12⋯Cg5^iv; symmetry code: (iv) −x + 1, y + , −z + ] is also identified, reinforcing the packing and providing additional cohesion to the supra­molecular network (Fig. 2 ▸b). The hydrogen bonds and non-classical contacts form a directional chain along [011]; all inter­molecular contacts are presented in Table 2 ▸.

Figure 2.

Packing diagram for (I) illustrating the inter­molecular hydrogen-bonding: classical N—H⋯O and non-classical C—H⋯π inter­actions. Classical N—H⋯O hydrogen bonds are shown as blue dashed lines; non-classical C—H⋯π inter­actions are shown in green. These contacts form chains along the [011] direction.

Table 2. Hydrogen-bond geometry (Å, °).

Cg is the centroid of the C3–C8ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2⋯O2ii	0.86 (1)	1.91 (1)	2.750 (8)	167 (1)
N4—H4⋯O1iii	0.86 (1)	2.41 (1)	3.044 (8)	132 (1)
N4—H4⋯O2iii	0.86 (1)	2.30 (1)	3.064 (8)	148 (1)
C12—H12⋯Cg5iv	0.93 (2)	2.83 (2)	3.702 (15)	156 (2)

Symmetry codes: (ii) ; (iii) ; (iv) .

4. Hirshfeld surface

A Hirshfeld surface analysis was performed using CrystalExplorer 21.5 (Spackman et al., 2021 ▸) and d_norm maps and two-dimensional fingerprint plots were generated, providing a qu­anti­tative assessment of the contributions of different types of inter­molecular contacts to the total Hirshfeld surface.

In the d_norm map (Fig. 3 ▸), localized dark-red spots correspond to contacts shorter than the sum of the van der Waals radii, white regions indicate contacts close to the sum of the radii, and blue areas denote elongated contacts. In the complex under study, the most significant close contacts and directional inter­molecular inter­actions are represented by the following inter­actions identified in the structural analysis. The pronounced red spots around atoms N2/N4 and O1/O2 indicate directional N—H⋯O hydrogen bonds. The presence of small red spots in the region of the aromatic ring points to possible π–π and C—H⋯π contacts. These contacts are consistent with the localized red spots on the d_norm map, indicating the presence of directional hydrogen bonds and edge contacts between aromatic fragments.

Figure 3.

Two-dimensional fingerprint plots for the title compound, showing (a) all inter­actions, and decomposed into (b) C⋯H/H⋯C, (c) H⋯H and (d) O⋯H/H⋯O inter­actions.

The two-dimensional fingerprint plots (Fig. 4) qu­anti­tatively characterize the contribution of different contact pairs to the overall Hirshfeld surface. For this structure the following contributions are observed: H⋯C/C⋯H = 36.2%, H⋯H = 35.3%, O⋯H/H⋯O = 18.1%, N⋯H/H⋯N = 7.3%, C⋯C = 2.6% and N⋯C/C⋯N = 0.5%. The approximately equal contributions of H⋯C and H⋯H contacts indicate that mol­ecular packing is determined both by close van der Waals inter­actions between hydrogen atoms and by numerous edge contacts between aromatic rings (C—H⋯π and close ring–ring approaches). The significant contribution of O⋯H/H⋯O (18.1%), together with the notable contribution of N⋯H/H⋯N (7.3%), confirms the presence of directional hydrogen bonds in the crystal, which include N—H⋯O-type contacts, which play an important role in consolidating the packing. The low C⋯C contribution (2.6%) indicates that direct π–π inter­actions between rings are present but are not a dominating factor – this is consistent with the visual data from the d_norm map.

5. Database survey

A search of the Cambridge Structural Database (CSD, version 2024.2.0; Groom et al., 2016 ▸) showed that no similar structures containing a cobalt–BICA fragment were recorded. A search for a cobalt–BI fragment yielded 1053 similar structures, among which one can find related compounds, for example a cobalt complex based on benzimidazole and quinaldinate (CSD refcode BECFAR; Döring et al., 1997 ▸). In addition, cobalt coordination compounds based on benzimidazole with various secondary ligands can be found [CSD refcodes YOJJAK (Cheng et al., 2013 ▸), BAWNAP (Feng, 2003 ▸), EKEQIU (Lin et al., 2003 ▸), ESUZUN (Ling & Feng, 2003 ▸) and GAVZAF (Zheng et al., 2005 ▸)]. Organometallic coordination compounds based on benzimidazole occur with various d-block metals, as well as with derivatives of this ligand, for example XUGJIW (Siddikova et al., 2024 ▸); additionally, organic salts involving benzimidazole have been reported, e.g. HOWKUD (Mukhammadiev et al., 2024 ▸).

6. Synthesis and crystallization

Preparation of solutions: (a) CoCl₂·6H₂O (0.1 mmol) dissolved in 5 ml of ethanol, (b) BI (0.2 mmol) dissolved in 3 ml of ethanol, and (c) BICA (0.2 mmol) dissolved in 3 ml of ethanol. Solution (a) was added to solution (b) and stirred for 30 minutes at room temperature on a magnetic stirrer. After that, solution (c) was added dropwise and the mixture was stirred for 12 h, during which it acquired a pink color. After several days a pale-pink precipitate formed, which was filtered off and washed several times with ethanol. Because both the initial precipitate and the obtained crystals were soluble in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), recrystallization was carried out from N,N-dimethylformamide (DMF). Bright-pink single crystals were obtained after recrystallization.

7. Refinement

Crystallographic data, data-collection conditions and structure-refinement parameters are summarized in Table 3 ▸. Hydrogen atoms were placed in calculated idealized positions and refined using a riding model with C—H distances of 0.93–0.98 Å and U_iso(H) = 1.2U_eq(C).

Table 3. Experimental details.

Crystal data
Chemical formula	[Co(C8H5N2O2)2(C7H6N2)2]
M r	617.49
Crystal system, space group	Monoclinic, P21/c
Temperature (K)	273
a, b, c (Å)	10.449 (4), 13.111 (5), 11.508 (5)
β (°)	113.427 (17)
V (Å3)	1446.6 (11)
Z	2
Radiation type	Mo Kα
μ (mm−1)	0.64
Crystal size (mm)	0.42 × 0.28 × 0.08
Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 ▸)
Tmin, Tmax	0.672, 0.754
No. of measured, independent and observed [I ≥ 2u(I)] reflections	3327, 3324, 1747
R int	0.050
(sin θ/λ)max (Å−1)	0.651
Refinement
R[F2 > 2σ(F2)], wR(F2), S	0.119, 0.337, 1.01
No. of reflections	3324
No. of parameters	196
No. of restraints	120
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)	2.22, −1.92

Computer programs: APEX2 and SAINT (Bruker, 2014 ▸), OLEX2.refine (Bourhis et al., 2015 ▸), OLEX2 (Dolomanov et al., 2009 ▸), Mercury (Macrae et al., 2020 ▸), ShelXle (Hübschle et al., 2011 ▸) and PLATON (Spek, 2020 ▸).

Supplementary Material

CCDC reference: 2515503

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

supplementary crystallographic information

Bis(1H-benzimidazole-κN³)bis(benzimidazole-2-carboxylato-κ²N³,O)cobalt(II) . Crystal data

[Co(C8H5N2O2)2(C7H6N2)2]	F(000) = 634
Mr = 617.49	Dx = 1.418 Mg m−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 10.449 (4) Å	Cell parameters from 9790 reflections
b = 13.111 (5) Å	θ = 2.2–22.5°
c = 11.508 (5) Å	µ = 0.64 mm−1
β = 113.427 (17)°	T = 273 K
V = 1446.6 (11) Å3	Plate, clear light pink
Z = 2	0.42 × 0.28 × 0.08 mm

Bis(1H-benzimidazole-κN³)bis(benzimidazole-2-carboxylato-κ²N³,O)cobalt(II) . Data collection

Bruker APEXII CCD diffractometer	1747 reflections with I≥ 2u(I)
ω scans	Rint = 0.050
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	θmax = 27.6°, θmin = 2.6°
Tmin = 0.672, Tmax = 0.754	h = −13→12
3327 measured reflections	k = 0→17
3324 independent reflections	l = 0→14

Bis(1H-benzimidazole-κN³)bis(benzimidazole-2-carboxylato-κ²N³,O)cobalt(II) . Refinement

Refinement on F2	22 constraints
Least-squares matrix: full	Primary atom site location: dual
R[F2 > 2σ(F2)] = 0.119	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.337	H atoms treated by a mixture of independent and constrained refinement
S = 1.01	w = 1/[σ2(Fo2) + (0.1973P)2] where P = (Fo2 + 2Fc2)/3
3324 reflections	(Δ/σ)max = −0.0003
196 parameters	Δρmax = 2.22 e Å−3
120 restraints	Δρmin = −1.92 e Å−3

Bis(1H-benzimidazole-κN³)bis(benzimidazole-2-carboxylato-κ²N³,O)cobalt(II) . Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Co1	0.5	0.5	0.5	0.0425 (5)
O2	0.1616 (5)	0.5781 (3)	0.5794 (5)	0.0611 (13)
O1	0.3716 (4)	0.5810 (3)	0.5730 (4)	0.0492 (11)
N2	0.1003 (5)	0.3967 (4)	0.4220 (5)	0.0523 (14)
H2	0.0250 (5)	0.4102 (4)	0.4323 (5)	0.0628 (17)*
N3	0.5820 (5)	0.4044 (4)	0.6666 (5)	0.0526 (14)
N1	0.3189 (5)	0.4098 (4)	0.4329 (5)	0.0478 (14)
C3	0.2586 (7)	0.3223 (5)	0.3667 (6)	0.0478 (16)
C8	0.1262 (7)	0.3132 (5)	0.3579 (6)	0.0522 (17)
C2	0.2511 (6)	0.5450 (5)	0.5456 (6)	0.0434 (15)
N4	0.6677 (7)	0.2634 (5)	0.7808 (7)	0.075 (2)
H4	0.6871 (7)	0.1999 (5)	0.7968 (7)	0.090 (2)*
C1	0.2220 (6)	0.4517 (5)	0.4647 (6)	0.0423 (15)
C15	0.6984 (10)	0.3401 (7)	0.8632 (8)	0.090 (3)
C10	0.6416 (12)	0.4264 (6)	0.7911 (9)	0.098 (3)
C7	0.0370 (8)	0.2328 (6)	0.2923 (7)	0.068 (2)
H7	−0.0550 (8)	0.2272 (6)	0.2840 (7)	0.082 (3)*
C5	0.2337 (9)	0.1699 (6)	0.2510 (7)	0.077 (2)
H5	0.2686 (9)	0.1196 (6)	0.2145 (7)	0.092 (3)*
C6	0.0995 (10)	0.1636 (6)	0.2418 (8)	0.086 (3)
H6	0.0464 (10)	0.1083 (6)	0.1980 (8)	0.103 (3)*
C9	0.5984 (9)	0.3079 (7)	0.6647 (8)	0.082 (3)
H9	0.5656 (9)	0.2705 (7)	0.5898 (8)	0.099 (3)*
C4	0.3154 (8)	0.2480 (6)	0.3125 (7)	0.067 (2)
H4a	0.4068 (8)	0.2530 (6)	0.3191 (7)	0.081 (3)*
C14	0.7669 (17)	0.3382 (9)	0.9911 (10)	0.165 (5)
H14	0.8126 (17)	0.2808 (9)	1.0360 (10)	0.198 (6)*
C11	0.640 (2)	0.5186 (9)	0.8471 (12)	0.167 (6)
H11	0.601 (2)	0.5768 (9)	0.8000 (12)	0.201 (7)*
C13	0.762 (2)	0.4299 (11)	1.0480 (14)	0.214 (7)
H13	0.802 (2)	0.4327 (11)	1.1360 (14)	0.257 (8)*
C12	0.701 (2)	0.5195 (11)	0.9814 (15)	0.216 (7)
H12	0.701 (2)	0.5790 (11)	1.0253 (15)	0.260 (8)*

Bis(1H-benzimidazole-κN³)bis(benzimidazole-2-carboxylato-κ²N³,O)cobalt(II) . Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Co1	0.0417 (7)	0.0411 (8)	0.0423 (8)	−0.0004 (5)	0.0143 (5)	−0.0002 (5)
O2	0.049 (3)	0.064 (3)	0.070 (3)	0.005 (2)	0.023 (2)	−0.015 (3)
O1	0.045 (2)	0.051 (3)	0.044 (3)	−0.0022 (19)	0.009 (2)	−0.003 (2)
N2	0.045 (3)	0.053 (3)	0.053 (3)	−0.007 (2)	0.013 (3)	−0.006 (3)
N3	0.061 (3)	0.040 (3)	0.056 (4)	−0.001 (2)	0.022 (3)	0.003 (3)
N1	0.046 (3)	0.055 (3)	0.040 (3)	0.006 (2)	0.015 (2)	−0.007 (3)
C3	0.045 (4)	0.051 (4)	0.038 (4)	0.004 (3)	0.006 (3)	−0.005 (3)
C8	0.055 (4)	0.049 (4)	0.042 (4)	−0.008 (3)	0.008 (3)	−0.002 (3)
C2	0.043 (3)	0.041 (4)	0.039 (4)	0.009 (3)	0.009 (3)	0.002 (3)
N4	0.091 (5)	0.056 (4)	0.071 (5)	0.011 (3)	0.024 (4)	0.023 (4)
C1	0.033 (3)	0.050 (4)	0.037 (4)	0.000 (3)	0.007 (3)	0.006 (3)
C15	0.130 (7)	0.070 (5)	0.044 (4)	−0.017 (4)	0.007 (4)	0.014 (3)
C10	0.164 (9)	0.058 (5)	0.053 (5)	0.001 (4)	0.023 (5)	0.006 (3)
C7	0.073 (5)	0.064 (5)	0.049 (4)	−0.014 (4)	0.005 (4)	−0.016 (4)
C5	0.080 (6)	0.068 (5)	0.067 (6)	0.004 (4)	0.014 (5)	−0.025 (4)
C6	0.093 (7)	0.064 (5)	0.065 (6)	−0.022 (4)	−0.006 (5)	−0.024 (4)
C9	0.109 (7)	0.068 (6)	0.054 (5)	−0.011 (5)	0.015 (5)	0.000 (4)
C4	0.074 (5)	0.072 (5)	0.051 (5)	0.003 (4)	0.019 (4)	−0.011 (4)
C14	0.280 (13)	0.108 (7)	0.050 (5)	−0.008 (6)	0.005 (5)	0.007 (4)
C11	0.324 (16)	0.087 (6)	0.069 (6)	0.015 (6)	0.054 (7)	−0.008 (4)
C13	0.391 (17)	0.132 (9)	0.073 (7)	0.010 (7)	0.043 (7)	−0.003 (5)
C12	0.411 (19)	0.127 (8)	0.082 (7)	0.028 (8)	0.068 (7)	−0.009 (5)

Bis(1H-benzimidazole-κN³)bis(benzimidazole-2-carboxylato-κ²N³,O)cobalt(II) . Geometric parameters (Å, º)

Co1—O1	2.128 (4)	N4—C15	1.331 (10)
Co1—O1i	2.128 (4)	N4—C9	1.372 (10)
Co1—N3	2.162 (5)	C15—C10	1.389 (12)
Co1—N3i	2.162 (5)	C15—C14	1.357 (12)
Co1—N1	2.101 (5)	C10—C11	1.373 (14)
Co1—N1i	2.101 (5)	C7—H7	0.9300
O2—C2	1.226 (7)	C7—C6	1.375 (12)
O1—C2	1.262 (7)	C5—H5	0.9300
N2—H2	0.8600	C5—C6	1.366 (11)
N2—C8	1.405 (8)	C5—C4	1.341 (10)
N2—C1	1.372 (7)	C6—H6	0.9300
N3—C10	1.346 (10)	C9—H9	0.9300
N3—C9	1.278 (9)	C4—H4a	0.9300
N1—C3	1.383 (8)	C14—H14	0.9300
N1—C1	1.324 (8)	C14—C13	1.379 (16)
C3—C8	1.351 (9)	C11—H11	0.9300
C3—C4	1.409 (10)	C11—C12	1.418 (18)
C8—C7	1.410 (9)	C13—H13	0.9300
C2—C1	1.494 (10)	C13—C12	1.41 (2)
N4—H4	0.8600	C12—H12	0.9300
O1i—Co1—O1	180.0	N1—C1—N2	112.6 (6)
N3i—Co1—O1i	91.66 (18)	C2—C1—N2	125.7 (5)
N3—Co1—O1	91.66 (18)	C2—C1—N1	121.6 (5)
N3i—Co1—O1	88.34 (18)	C10—C15—N4	105.4 (7)
N3—Co1—O1i	88.34 (18)	C14—C15—N4	129.3 (9)
N3—Co1—N3i	180.0	C14—C15—C10	125.3 (10)
N1i—Co1—O1	101.00 (18)	C15—C10—N3	111.6 (8)
N1i—Co1—O1i	79.00 (18)	C11—C10—N3	126.9 (9)
N1—Co1—O1i	101.00 (18)	C11—C10—C15	121.2 (10)
N1—Co1—O1	79.00 (18)	H7—C7—C8	123.3 (5)
N1—Co1—N3	88.9 (2)	C6—C7—C8	113.3 (8)
N1i—Co1—N3	91.1 (2)	C6—C7—H7	123.3 (5)
N1i—Co1—N3i	88.9 (2)	C6—C5—H5	119.8 (5)
N1—Co1—N3i	91.1 (2)	C4—C5—H5	119.8 (5)
N1i—Co1—N1	180.0	C4—C5—C6	120.4 (8)
C2—O1—Co1	115.9 (4)	C5—C6—C7	124.9 (7)
C8—N2—H2	127.7 (3)	H6—C6—C7	117.5 (5)
C1—N2—H2	127.7 (4)	H6—C6—C5	117.5 (5)
C1—N2—C8	104.7 (5)	N4—C9—N3	115.2 (8)
C10—N3—Co1i	132.2 (5)	H9—C9—N3	122.4 (5)
C9—N3—Co1i	124.5 (5)	H9—C9—N4	122.4 (5)
C9—N3—C10	102.8 (7)	C5—C4—C3	118.0 (8)
C3—N1—Co1i	144.7 (4)	H4a—C4—C3	121.0 (4)
C1—N1—Co1i	109.9 (4)	H4a—C4—C5	121.0 (5)
C1—N1—C3	105.4 (5)	H14—C14—C15	123.3 (7)
C8—C3—N1	110.1 (6)	C13—C14—C15	113.3 (12)
C4—C3—N1	129.6 (6)	C13—C14—H14	123.3 (8)
C4—C3—C8	120.3 (6)	H11—C11—C10	122.1 (7)
C3—C8—N2	107.3 (5)	C12—C11—C10	115.8 (12)
C7—C8—N2	129.7 (7)	C12—C11—H11	122.1 (8)
C7—C8—C3	123.0 (7)	H13—C13—C14	117.9 (8)
O1—C2—O2	126.8 (6)	C12—C13—C14	124.2 (14)
C1—C2—O2	119.7 (6)	C12—C13—H13	117.9 (9)
C1—C2—O1	113.5 (5)	C13—C12—C11	119.7 (14)
C15—N4—H4	127.5 (4)	H12—C12—C11	120.1 (8)
C9—N4—H4	127.5 (5)	H12—C12—C13	120.1 (9)
C9—N4—C15	104.9 (7)
Co1—O1—C2—O2	178.5 (4)	C3—C8—N2—C1	0.6 (6)
Co1—O1—C2—C1	−0.7 (4)	C3—C8—C7—C6	1.8 (8)
Co1—N3—C10—C15	−170.5 (10)	C3—C4—C5—C6	0.2 (9)
Co1—N3—C10—C11	14.8 (12)	C8—N2—C1—C2	−176.1 (5)
Co1—N3—C9—N4	172.3 (6)	C8—C3—N1—C1	0.8 (6)
Co1—N1—C3—C8	−178.7 (8)	C8—C3—C4—C5	1.0 (8)
Co1—N1—C3—C4	1.4 (9)	C8—C7—C6—C5	−0.7 (9)
Co1—N1—C1—N2	179.3 (4)	N4—C15—C10—C11	172.7 (11)
Co1—N1—C1—C2	−4.5 (5)	N4—C15—C14—C13	−171.0 (17)
O2—C2—C1—N2	0.1 (7)	N4—C9—N3—C10	−1.0 (9)
O2—C2—C1—N1	−175.6 (6)	C1—N2—C8—C7	−178.3 (5)
O1—C2—C1—N2	179.4 (5)	C1—N1—C3—C4	−179.0 (5)
O1—C2—C1—N1	3.7 (6)	C15—C10—N3—C9	2.0 (10)
N2—C8—C3—N1	−0.9 (6)	C15—C10—C11—C12	0.7 (16)
N2—C8—C3—C4	179.0 (5)	C15—C14—C13—C12	−4 (2)
N2—C8—C7—C6	−179.5 (8)	C10—C15—N4—C9	1.6 (10)
N2—C1—N1—C3	−0.4 (6)	C10—C15—C14—C13	7.2 (15)
N3—C10—C15—N4	−2.4 (10)	C10—C11—C12—C13	2 (2)
N3—C10—C15—C14	179.0 (11)	C7—C8—C3—C4	−2.0 (8)
N3—C10—C11—C12	175.0 (18)	C7—C6—C5—C4	−0.3 (11)
N3—C9—N4—C15	−0.5 (9)	C9—N3—C10—C11	−172.7 (12)
N1—C3—C8—C7	178.1 (5)	C9—N4—C15—C14	−179.9 (11)
N1—C3—C4—C5	−179.2 (8)	C14—C15—C10—C11	−5.8 (17)
N1—C1—N2—C8	−0.1 (6)	C14—C13—C12—C11	−0 (3)
C3—N1—C1—C2	175.8 (5)

Symmetry code: (i) −x+1, −y+1, −z+1.

Bis(1H-benzimidazole-κN³)bis(benzimidazole-2-carboxylato-κ²N³,O)cobalt(II) . Hydrogen-bond geometry (Å, º)

Cg is the centroid of the C3–C8ring.

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···O2ii	0.86 (1)	1.91 (1)	2.750 (8)	167 (1)
N4—H4···O1iii	0.86 (1)	2.40 (1)	3.044 (8)	132 (1)
N4—H4···O2iii	0.86 (1)	2.30 (1)	3.064 (8)	148 (1)
C12—H12···Cg5iv	0.93 (2)	2.83 (2)	3.702 (15)	156 (2)

Symmetry codes: (ii) −x, −y+1, −z+1; (iii) −x+1, y−1/2, −z+3/2; (iv) −x+1, y+1/2, −z+3/2.