Zinc imidazole liganding

Many of the biologically active zinc metalloproteins contain a zinc(II) ion bound to one or more imidazole ligands of the amino add residue histidine. For this reason a large number of studies over an extended period have been carried out on zinc and cadmium complexes of imidazole, substituted imidazoles, histidine and related ligands. There has also been much recent activity in this field much structural information is available. 

The self-assembled diad formed by axial coordination of zinc naphthalocyanine (ZnNc) and fulleropyrrolidine bearing a coordinating imidazole ligand (Qolm) is a good example of a supramolecular system undergoing photoinduced electron... 

One of the most unusual aspects of the structure of this enzyme is the occurrence of the bridging imidazolate ligand, which holds the copper and zinc ions 6 A apart. Such a configuration is not unusual for imidazole complexes of... 

X-Ray studies of carbonic anhydrase show that the active center is composed of three imidazole ligands which have distorted tetrahedral coordination to the Zn(II) ion. Molecular models suggested that a similar geometry could be attained with a tris(imidazolyl) methane derivation. For this reason, R. Breslow s team (218) in 1978 synthesized tris[4(5)imidazolyl] carbinol (4-TIC) and tris(2-imidazolyl) carbinol (2-TIC) as models for the zinc binding site of carbonic anhydrase and alkaline phosphatase. Similarly, bis[4(5)-... 

Li and coworkers also recently reported the separation of propene and propane using zinc-based ZIFs, utilizing the different rates of adsorption of the two molecules (Figure 7). The ZIF series, as previously mentioned in Section 2.2, is comprised of 3-D frameworks formed upon divalent metals with tetrahedral coordination geometry and imidazole ligands. Apart from their chemical and thermal stability, ZIFs also lack Lewis and Bronsted acid sites that can result in the... 

Despite the weak basicity of isoxazoles, complexes of the parent methyl and phenyl derivatives with numerous metal ions such as copper, zinc, cobalt, etc. have been described (79AHC(25) 147). Many transition metal cations form complexes with Imidazoles the coordination number is four to six (70AHC(12)103). The chemistry of pyrazole complexes has been especially well studied and coordination compounds are known with thlazoles and 1,2,4-triazoles. Tetrazole anions also form good ligands for heavy metals (77AHC(21)323). 

Imidazole is of particular relevance to biological mimic ligands due to the presence of histidine as a coordinating group for zinc in biological systems and has been a particular target for zinc complex formation. 

An imidazole/pyridyl ligand (4) coordinates to a copper(II) center and on deprotonation the imidazole reacts with bis(hexafluoroacetylacetonato)zinc to form a trimeric Cu2Zn species bridged by imidazoles. The zinc ion is in an octahedral coordination environment with Zn-N distances of 2.029(2) A.116... 

The biphenyl ligand functionalized with two imidazoles (6) was used to produce distorted tetrahedral complexes of zinc.119 2,2 -Biimidazole can act as a bidentate ligand coordinating to one zinc ion (7) or as a bridging ligand in the formation of dimeric species (8) with X-ray structures of both binding motifs.120... 

---