2,2′-[4,10-Bis(carb­oxy­meth­yl)-4,10-diaza-1,7-diazo­niacyclo­dodecane-1,7-di­yl]diacetate dihydrate

Paul S Szalay; Matthias Zeller; Allen D Hunter

doi:10.1107/S1600536811004843

. 2011 Feb 16;67(Pt 3):o644. doi: 10.1107/S1600536811004843

2,2′-[4,10-Bis(carboxymethyl)-4,10-diaza-1,7-diazoniacyclododecane-1,7-diyl]diacetate dihydrate

Paul S Szalay ^a,^*, Matthias Zeller ^b, Allen D Hunter ^b

PMCID: PMC3052104 PMID: 21522397

Abstract

In the title compound, C₁₆H₂₈N₄O₈·2H₂O, the 12-membered macrocycle has twofold crystallographic symmetry and the asymmetric unit comprises one half-molecule. The four carboxyl/carboxylate groups reside on the same side of the macrocycle. The molecule is a double zwitterion with two of the carboxylic acid H atoms transferred to the two N atoms on the opposite sides of the macrocycle, resulting in both N atoms having positive charges and leaving the two resulting carboxylate groups with negative charges. The two remaining carboxylic acid groups and the carboxylate groups form O—H⋯O hydrogen bonds with the crystal water molecules. The H atoms bound to the N atoms within the macrocyle are engaged in two equivalent hydrogen bonds with the adjacent N atoms.

Related literature

Kumagai et al. (2002 ▶) describe different coordinations for carboxylate groups. For background information about the title compound and its metal complexes, see: Viola-Villegas & Doyle (2009 ▶). For macrocycle configurations, see: Bosnich et al. (1965 ▶); Dale (1973 ▶, 1976 ▶, 1980 ▶); Meyer et al. (1998 ▶).

Experimental

Crystal data

C₁₆H₂₈N₄O₈·2H₂O
M _r = 440.46
Orthorhombic,
a = 17.183 (2) Å
b = 6.5826 (9) Å
c = 17.983 (2) Å
V = 2034.0 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.12 mm⁻¹
T = 100 K
0.43 × 0.27 × 0.27 mm

Data collection

Bruker SMART APEX CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker 2003 ▶) T _min = 0.810, T _max = 1.000
19408 measured reflections
2520 independent reflections
2236 reflections with I > 2σ(I)
R _int = 0.037

Refinement

R[F ² > 2σ(F ²)] = 0.042
wR(F ²) = 0.112
S = 1.08
2520 reflections
144 parameters
2 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.70 e Å⁻³
Δρ_min = −0.19 e Å⁻³

Data collection: SMART (Bruker, 2001 ▶); cell refinement: SAINT-Plus (Bruker, 2001 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXL97 and PLATON Spek (2009) ▶.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811004843/kp2290sup1.cif

e-67-0o644-sup1.cif^{(16.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811004843/kp2290Isup2.hkl

e-67-0o644-Isup2.hkl^{(123.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Enhanced figure: interactive version of Fig. 3

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3⋯O5	0.84	1.71	2.5295 (14)	166
N1—H1⋯N2	0.93	2.44	2.8940 (14)	110
O5—H5D⋯O1ⁱ	0.86 (1)	1.78 (2)	2.6380 (14)	173 (2)
O5—H5C⋯O1ⁱⁱ	0.84 (1)	1.85 (2)	2.6776 (14)	170 (2)

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

MZ was supported by NSF grant 0111511. The diffractometer was funded by NSF grant 0087210, by the Ohio Board of Regents grant CAP-491 and by Youngstown State University.

supplementary crystallographic information

Comment

In the course of our studies to prepare coordination polymer and metal-organic framework type compounds we investigated the title compound as a potentional building block. The molecule 1,4,7,10-tetraazacyclodecane-1,4,7,10-tetraacetic acid DOTAH₄ and its deprotonated analogs, [DOTAH₂]^2- and [DOTA]^4- have several features desirable in coordination chemistry. The ligand offers a macrocycle with four neutral nitrogen donor sites as well as four dangling carboxylic acid groups. Carboxylate groups when deprotonated have been shown to exhibit nine different coordination modes with metal ions, seven of which coordinate two or more metal ions (Kumagai et al., 2002). Therefore, the potential for forming molecular species as well as coordination polymers or metal-organic framework type compounds exists for this organic building block. For numerous examples of metal containing DOTAH₄ compounds and its charged analogues see Viola-Villegas & Doyle (2009).

Only half of DOTAH₄ molecule (Fig. 1) in the structure is an asymmetric unit. The other half of the macrocycle is generated by a twofold rotation axis parallel to the b axis. There is no significant ring strain based on an analysis of the bond angles withing the ring. The ring is composed of eight methylene carbons (C1—C4, C1ⁱ—C4ⁱ), two ammonium N atoms (N1, N1ⁱ) and two tertiary N atoms (N2, N2ⁱ) (symmetry operator (i): -x + 1, y, -z + 3/2). The bond angles between them range from 110–112°. The configuration has all four N atoms located above the eight methylene carbons along the direction of the twofold axis in the centre of the ring producing a basket-like shape that would be able to coordinate a metal without large changes of the overall structure of the molecule. According to the system outlined by Dale this arrangement would be described as (3,3,3,3)-B (Dale, 1973, 1976, 1980, Meyer et al., 1998). This system uses numbers to indicate the number of chemical bonds between the genuinie corners in the macrocycle. Genuine corners are the central atoms in an anti-gauche-gauche-anti bond sequence. In the title compound the atoms C1, C3, C1A, and C3A constitute genuine corners which are separated from each other along the macrocycle by three bonds. The "B" designation indicates that the four heteroatoms in this 12-membered macrocylce reside in a square planar arrangement above the methylene carbons (as described above). Using the terminology of Bosnich et al. (1965) the configuration of the macrocycle would be cis-I since all of the carboxylate containing groups project in the same direction.

The weighted average ring bond distance is 1.503 Å (PLATON, Spek (2009)). The weighted average absolute torsion angle is 100.45°. The total puckering amplitude of the ring is 1.526 Å. The four carboxylic acid and carboxylate groups are bound to the N atoms and also all reside above the macrocycle. This arrangement leads to well separated hydrophobic and hydrophilic parts within the molecule. The H atoms bound to the N atoms within the macrocyle are engaged in two equivalent hydrogen bonds with the adjacent nitrogen atoms (N1—H1···N2, N1ⁱ—H1ⁱ···N2ⁱ, Table 1). The N1—H1 and H1···N2 distances are 0.93 Å and 2.44 Å respectively. The angle between the donor and acceptor is 110.1° in accord with the donor and acceptor both residing within the ring and being separated by two atoms.

The crystal packing (Figs. 2 and 3) is dominated by hydrogen bonding between the crystal water molecules and the carboxylic acid and carboxylate groups. Each water molecule forms three hydrogen bonding interactions with the two hydrogen atoms oriented towards carboxylate groups (O5—H5D···O1ⁱⁱ, O5—H5C···O1ⁱⁱⁱ, Table 1) and the oxygen directed towards a carboxylic acid group (O3—H3···O5, Table 1).

Experimental

The title compound 1,4,7,10-tetraazacyclodecane-1,4,7,10-tetraacetic acid was purchased from Strem Chemicals and used without further purification.

The compound was crystallized from a saturated DMSO solution. A DMSO solution (2 mL) was saturated with DOTAH₄ at 323 K. Upon cooling to room temperature and sitting for four days colourless block shaped crystals were formed.