Mixed-valence outer-sphere RuII/RuIII ion-pair complexes. Synthesis, experimental, and theoretical studies

Two new ion-pair complexes, consisting of a cationic polypirydyl Ru(II) complex ([Ru-II(terpy)(bipy)Cl](+) or [RuII(terpy)(phen)Cl](+)) and the cis-[RuIIICl2(pic)(2)](-) anion (terpy = 2,2 ':6 ',2 ''-terpyridine, bipy = 2,2 '-bipyr-idine, phen = 1,10-phenanthroline and pic- = picolinate) were synthesized. Magnetic and EPR studies were preceded by identifying the obtained species and checking the homogeneity and purity of the bulk material using various analytical techniques: single-crystal and powder X-ray diffraction, SEM, EDX, and FT-IR spectroscopies in the solid state, and ESI-MS in solution. The spectral characteristics in the UV-vis range and redox behavior of the ion-pair complexes were examined. The principal g components for [RuII(terpy)(bipy)Cl](+)[cis-(RuCl2)-Cl-III(- pic)(2)](-) .(CH3)(2)CO.H2O,1, and [RuII(terpy)(phen)Cl]+[cis-(RuCl2)-Cl-III(pic)(2)](-) .2H(2)O, 2, and their Ru(III )precursor [H (Hpic)(2)](+)[cis-(RuCl2)-Cl-III(pic)(2)](-)center dot 2H(2)O were similar and typical for low-spin d5 species. The presence of one un-paired electron (in the dxy orbital) was shown by DFT calculations. The EPR spectra of 1 and 2 were characteristic for species in a singlet state (S = 1/2 systems) in contrast to that of their analog, previously reported for the first Ru-II/Ru(III )ion-pair complex, [RuII(bipy)2(pic)](+)[cis-(RuCl2)-Cl-III(pic)2]-, typical for a species in the triplet state (S = 1 system).

Automated summary

Two new ion-pair complexes were synthesized and their properties and purity were characterized using various analytical techniques. The spectral characteristics and redox behavior of these complexes were examined, and their EPR spectra were found to be different from previously reported analogs. The presence of an unpaired electron was confirmed by DFT calculations.