89252-48-2Relevant academic research and scientific papers
Metall ?-Complexes of Benzene Derivatives, XIX, Intramolecular Ligand-Ligand Electron Transfer in Paramagnetic Bis(η6-arene)chromium Complex Anions
Elschenbroich, Christoph,Bilger, Edgar,Heck, Juergen,Stohler, Felix,Heinzer, Josef
, p. 23 - 41 (2007/10/02)
Two series of aroyl-substituted bis(η6-arene)chromium derivatives (RCO-η6-C6H5)(η6-C6H6)Cr and (RCO-η6-C6H5)2Cr were prepared: R = C6H5 (6,9); R = 4-H3CC6H4 (7,10); R = 4-FC6H4 (8,11); R = 4-F3CC6H4 (12,14); R = 4-NC5H4(pyridyl) (13,15).These complexes were reduced to their radical anions by potassium in dimethoxyethane as well as by electrochemical methods.Reduction potentials obtained via cyclic voltammetry are reported and the ESR spectra of the radical anions in fluid solution are assigned.Whereas in the case of the radical anions of the monosubstituted derivates 6-., 7-., 8-., 12-., and 13-. the unpaired electron necessarily is localized on one ligand, the radical anions of the disubstituted complexes 9-., 10-., 11-., 14-., and 15-. display diversified behavior.The ligand hyperfine structure in the ESR spectra reveals, that for 15-. intramolecular electron transfer (ET) is slow on the ESR time scale.The transfer rate νET increases in the sequence 15-. (νET 7 s-1) -. (3.5 x 107 s-1) -. -. -. (5.3 x 108 s-1).The radical anions 6-C6H5>2Cr-. (22-.), 6-C6H4>2Cr-. (23-.), and 6-C6H3>2Cr-. (24-.) exhibit intramolecular ET which is fast on the ESR time scale (νET > 109 s-1).
