Imidazolate

Imidazolate

Names
IUPAC name Imidazolate
Other names Imidazolide
Identifiers
CAS Number	36954-03-7
ChemSpider	2631931
Jmol interactive 3D	Image
SMILES c1cnc[n-]1
Properties
Chemical formula	C3H3N2
Molar mass	67.070
Acidity (pKa)	14.05[1]
Thermochemistry
Std enthalpy of formation (ΔfH^o298)	67.8 kJ·mol^−1 (16.2 kcal·mol^−1) Gas phase.[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Imidazolate (C₃H₃N₂^-) is the conjugate base of imidazole. It is a nucleophile and a strong base. The free anion has C_2v symmetry. Imidazole has a pK_a of 14.05,^[1] so the deprotonation of imidazole (C₃H₃N₂H) requires a strong base.

Occurrence

Imidazolate is a common bridging ligand in coordination chemistry. In the zeolitic imidazolate frameworks, the metals are interconnected via imidazolates.^[3][4] In the enzyme superoxide dismutase, imidazolate links a Cu and Zn centers.

In the human SOD1 enzyme (rainbow-color N-terminus = blue, C-terminus = red), the copper (orange sphere) and zinc (grey sphere) centers are bridged by imidazolate.^[5]

References

1. WALBA, HAROLD; ISENSEE, ROBERT W. (August 1961). "Acidity Constants of Some Arylimidazoles and Their Cations". The Journal of Organic Chemistry 26 (8): 2789–2791. doi:10.1021/jo01066a039.
2. Gutowski, Keith E.; Rogers, Robin D.; Dixon, David A. (May 2007). "Accurate Thermochemical Properties for Energetic Materials Applications. II. Heats of Formation of Imidazolium-, 1,2,4-Triazolium-, and Tetrazolium-Based Energetic Salts from Isodesmic and Lattice Energy Calculations". The Journal of Physical Chemistry B 111 (18): 4788–4800. doi:10.1021/jp066420d.
3. Phan, A.; Doonan, C. J.; Uribe-Romo, F. J.; Knobler, C. B.; O'Keeffe, M.; Yaghi, O. M. "Synthesis, Structure, and Carbon Dioxide Capture Properties of Zeolitic Imidazolate Frameworks" Acc. Chem. Res. 2010, 43, 58-67. doi:10.1021/ar900116g
4. Zhang, J.-P.; Zhang, Y.-B.; Lin, J.-B.; Chen, X.-M., "Metal Azolate Frameworks: From Crystal Engineering to Functional Materials", Chem. Rev. 2012, vol. 112, pp. 1001-1033. doi:10.1021/cr200139g
5. PDB: 3CQQ​; Cao X, Antonyuk SV, Seetharaman SV, Whitson LJ, Taylor AB, Holloway SP, Strange RW, Doucette PA, Valentine JS, Tiwari A, Hayward LJ, Padua S, Cohlberg JA, Hasnain SS, Hart PJ (June 2008). "Structures of the G85R variant of SOD1 in familial amyotrophic lateral sclerosis". J. Biol. Chem. 283 (23): 16169–77. doi:10.1074/jbc.M801522200. PMC 2414278. PMID 18378676.