The title compound, {(C6H11N2)[CrCl3]}n, was generated via mixing of the ionic liquid 1-ethyl-3-methyl­imidazolium chloride with CrCl2 in ethanol. Crystals were obtained by a diffusion method. In the crystal structure, the anion forms one-dimensional chains of chloride-bridged Jahn–Teller distorted chromium(II) centers extending along the [100] direction. The imidazolium cations are positioned between these chains.

Glyoxalase II enzymes catalyze the hydrolysis of a thioester substrate and have been found to coordinate a variety of dimetal combinations, including Fe(III)Zn(II), within the enzyme active site. Of relevance to these enzymes, the thioester hydrolysis reactivity of the Fe(III)Zn(II) compound [(BPBPMP)Fe(III)Zn(II)(mu-OAc)(2)]ClO(4) (1) was evaluated in CH(3)CN/H(2)O (50:50; buffered) at 26.5 degrees C. Thioester hydrolysis in the absence and presence of 1 was monitored using (2)H NMR by following the loss of the thioester -SCD(3) signal. Two products are generated in the reaction involving the metal complex, D(3)CSSCD(3) and CD(3)SH. Kinetic studies of this reaction as a function of pH revealed maximum rate above the pK(a) of a Zn-OH(2) moiety of [(BPBPMP)Fe(III)(OH)(mu-OH)Zn(II)(OH(2))](+), which forms from 1 in CH(3)CN/H(2)O (50:50). UV-vis and electron paramagnetic resonance (EPR) studies of a single turnover thioester hydrolysis reaction in the presence of 1 equiv of 1 at pH = 9.0 suggest that the thioester does not initially interact with the Fe(III) center, but that changes occur at this site over the course of the reaction. The formation of a Fe(III)-SCD(3) moiety is proposed based on the observed D(3)CSSCD(3) formation, which likely results from redox activity involving a iron(III) thiolate species. A mechanism for thioester hydrolysis is proposed involving initial coordination of the deprotonated alpha-hydroxy thioester to the zinc center followed by nucleophilic attack by a terminal Fe(III)-OH moiety and thiolate leaving group stabilization by the Fe(III) center. Overall, this study outlines a novel approach of using an aliphatic thioester substrate and (2)H NMR to provide mechanistic insight into thioester hydrolysis involving an Fe(III)Zn(II) complex of relevance to glyoxalase II.

The mononuclear zinc complex [(bpta)Zn](ClO(4))(2).0.5H(2)O promotes the hydrolysis of the thioester PhCH(OH)C(O)SCD(3) when dissolved in CH(3)CN:H(2)O (50:50 buffered at pH 9.0). This reaction results in the formation of a mixture of CD(3)SH and a zinc thiolate complex, the latter of which can be protonated to generate additional CD(3)SH. Kinetic studies revealed an overall second-order reaction with an activation energy that is similar to that found for aqueous OH(-) promoted thioester hydrolysis. These studies represent the first investigation of chemistry relevant to that occurring in the monozinc-containing form of human glyoxalase II.

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