On the Electronic Structure of mer,trans−[RuCl3(1H−indazole)2(NO)], a Hypothetical Metabolite of the Antitumor Drug Candidate KP1019: An Experimental and DFT Study
The study reported herein focused on the electronic structure of the {Ru(NO)}6 fragment and characterization of the oxidation state of ruthenium in mer,trans-[RuCl3(Hind)2(NO)] (1; Hind = 1H-indazole) resulting from the reaction of mer,trans-[RuCl3(H2O)(Hind)2] (2) with NO in acetone or solid-state Anderson rearrangement of (H2ind)2[RuCl5(NO)] at 180 °C. The results of X-ray diffraction, 1H, 13C, and 15N NMR, EPR, IR, and UV/Vis spectroscopy, cyclic voltammetry, magnetic susceptibility, and XANES/EXAFS as well as theoretical data have been critically analyzed. The localized orbitals, domain-averaged Fermi holes, frontier orbitals, Mulliken population, and quantum theory of atoms-in-molecules (QTAIM) analyses are presented. In addition, mer,trans-[RuIIICl3(H2O)(Hind)2] (2) and trans-[RuIICl2(Hind)4] (3) were experimentally and theoretically investigated as reference compounds. A complete active space SCF calculation was performed to estimate the extent of antiferromagnetic spin–spin coupling in 1. We found that the closed-shell structure {RuIII(NO)0}6 fits better to the physical/spectroscopic properties of 1, although {RuII(NO)+}6 is formally still suitable for describing the oxidation state of Ru in this entit
