402498-32-2Relevant academic research and scientific papers
Complexes of ruthenium(III) and chromium(III) with a new tetradentate N2O2-donor ligand: Crystal structures, redox properties and spectroelectrochemistry
Frey, Guido D,Bell, Z?e R,Jeffery, John C,Ward, Michael D
, p. 3231 - 3237 (2001)
Reaction of 3-(2-methoxyphenyl)pyrazole with 1,2- bis(bromomethyl) benzene under phase-transfer conditions, followed by demethylation of the methoxyphenyl units with BBr3, affords the new ligand H2L in which two bidentate chelating units (pyrazolyl -phenol) are separated by a o-xylyl spacer. Reaction of H2L with [M(acac)3] (M = Cr, Ru) afforded in each case two mononuclear products [M(L)(acac)] and [M(L)(HL)]. Crystal structure determinations of [M(L)(acac)] for both M = Cr and Ru show that the complexes have similar structures, with the ligand L2- folded such that it coordinates as a tetradentate chelate in a cis-N2, cis-O2 manner with the remaining two coordination sites at the metal occupied by the acac ligand. Neither complex [M(L)(HL)] formed X-ray quality crystals but we assume a similar mononuclear structure in which one L2- is coordinated as a tetradentate chelate, and the second (HL)- is coordinated via one bidentate N,O-binding site with the second site pendant and remaining protonated. [Ru(L)(acac)] undergoes reversible oxidation to Ru(IV) and an irreversible reduction to Ru(II); in contrast, for [Ru(L)(HL)] the Ru(III)-Ru(IV) and Ru(II)-Ru(III) couples are both reversible. A UV-Vis-NIR spectroelectrochemical study of [Ru(L)(HL)] was accordingly carried out, and shows that in the Ru(IV) state the spectrum develops intense, low-energy charge-transfer transitions in the near-IR region.
