Synthesis, structure, and properties of bis(2-(1-ethyl-1H-imidazol-4-yl)acetate) copper(II)

Ethylation of imidazole-4-acetate methyl ester affords 1-ethyl-1H-Imidazol-4-ylacetic acid methyl ester (1) and 1-ethyl-1H-Imidazol-5-ylacetic acid methyl ester (2) in a 3:1 ratio. Both 1 and 2 can be converted to their potassium carboxylate salts, 3 and 4, respectively. Reaction of 3 with CuCl2 in methanol yields [Cu(eia)(2)]center dot 4MeOH (5 center dot 4MeOH) (eia(-) = 1-ethyl-1H-imidazol-4-yl)acetate). EPR measurement of 5 in methanol glass exhibits near axial symmetry with g(perpendicular to) (g(x) = 2.060, g(y) = 2.087) and g(parallel to) = g(z) = 2.293 with A(parallel to)(Cu) = A(z)(Cu) = 152 G, A(perpendicular to)(Cu) similar to 10 G, and A(y)(N) = 14G. Accordingly, the structure of 5 center dot 4MeOH reveals Cu(II) in tetragonally distorted octahedral geometry with O, N coordination from eia- and elongated bonding (2.506 angstrom) to methanol oxygens in the axial positions. An infinite 1-dimensional hydrogen bonding network involving methanol molecules is present. DFT studies have been carried out to assist in assignment of electronic transitions. Electrochemical studies on 5 in methanol and DMF reveal quasi-reversible redox behavior for the Cu-II/I couple while for MeCN a Cu-I/O stripping process is seen. (C) 2013 Elsevier B.V. All rights reserved.