Abstract
The isomeric title complexes Ru(trpy)(L)Cl+ were obtained in almost equimolar ratio from the reaction of Ru(trpy)Cl3 and 3-amino-6-(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine (L). Crystal structure analyses of the perchlorate hemihydrates, electrochem. and spectroscopic (NMR, UV/visible, EPR) studies, supported by DFT calcns., reveal distinct differences between the isomeric redox series 1n+ (tetrazine-Nt trans to Cl) and 2n+ (pyrazolyl-Np trans to Cl; n = 0, 1, 2). The latter system with the p acceptors trpy and tetrazine in the equatorial plane and the pyrazolyl and chloride donors in the axial positions exhibits facilitated oxidn., lower energy MLCT transitions, more balanced chelate coordination, and a higher g anisotropy in the oxidized (RuIII) state. According to partially resolved EPR spectra of 1-electron reduced neutral compds. 1 and 2, they have the unpaired electron predominantly in the tetrazine ring of L. on SciFinder(R)
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