ISSN:
0947-6539
Keywords:
copper complexes
;
imidazole ligands
;
redox systems
;
structure elucidation
;
enzyme models
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The new diimidazole ligand, bis (1-methyl-4,5-diphenylimidazol-2-yl)ke-tone (BIMDPK), has been synthesised, characterised and shown to form four-coordinate bis(diimidazole) CuII and CuI complexes in the salts [Cu(bimdpk)2]-[BF4]2 and [Cu(bimdpk)2][PF6], the structures of which have been determined by X-ray crystallography. The cations of these salts have a very similar geometry with CuII-Nav = 1.949 and CuI-Nav = 1.999 Å; the N-Cu-N interbond angles are constrained by 1) the bite angle of the BIMDPK ligand to 94 ± 2° and 2) the interligand steric interactions, which lead to the dihedral angle of the intraligand CuN2 planes of 68.2° for CuII and 74.9° for CuI-that is, a CuN4 geometry intermediate between tetrahedral and square planar. The X-band EPR spectrum for the powdered CuII compound is typical of an approximately D2 CuN4 centre possessing a dxy ground state (gx = 2.080, gy = 2.075, gz = 2.291; Az = 112.3 × 10-4 cm-1). The UV/vis spectra are dominated by charge-transfer bands, and both the CuII and CuI systems are intensely coloured. The EPR and electronic spectra indicate that these cations have a very similar structure in the solid state and in solution; the potential of the [Cu(bimdpk)2]2+/[Cu(bimdpk)2]+ couple is 0.59 V vs. SCE in MeCN and 0.80 V vs. SCE in CH2Cl2, and the electron self-exchange constant in MeCN is 1.9 × 104M-1S-1. Comparisons are made between the properties of the [Cu(bimdpk)2]2+/+ centres and related Cu centres in chmical and biological systems; the results of this study reinforce the view that a [Cu(His)4] centre should not be precluded from consideration in biological electron transport.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/chem.1460020611
