Electronic structure of metastable isomers of Ru nitroso complexes

Abstract

Since the time the authors of [1] have established the endogenic formation of NO, the number of the studies elucidating the role of this diatomic radical-molecule in biological processes is being steadily increased. In so far as nitrogen oxide is involved in numerous processes and affects the functions of many systems (including cardio-vascular system) and the transfer of nervous impulses, its excess or deficit in organs and tissues cause different pathophysiological conditions. The problem of monitoring the NO content in the organism stimulated an interest in the chemistry of NO and its compounds. The transition metal nitroso complexes, particularly, the Fe and Ru nitroso complexes, are extensively studied as the potential donors of nitrogen(II) oxide capable of delivering NO to the biological targets. Much attention is given to the quantum chemistry of nitroso complexes. The quantum-chemical calculations of Ru complexes were performed aimed at the search of metastable isomers [2-7]; their UV and visible spectra were assigned in [8][9][10]; the mutual effect of their ligands was studied and the proposed intermediates in the reactions with participation of the coordinated NO were modeled [11][12][13]. 1 The structural and energy characteristics of isomers with the linear η 1 -coordination of NO through the oxygen atom (MS1) and with the side η 2 -coordination of NO (MS2) were obtained for the [ Ru ( NO )( NH 3 ) 5 ] 3+ and [ Ru ( NO )( CN ) 5 ] 2-complexes [4]. The relative energies of the MS1 and MS2 isomers of some nitrosopor-1 The reports that most closely concern with the subject matter of this paper are only indicated.) [3, 6] were determined. Metastable isomers MS1 were experimentally detected for the above compounds, while the MS2 isomers were only found in [ Ru ( NO )(ë N ) 5 ] 2- [14] and [ Ru ( NO )(ë l ) 5 ] 2- [15]. Intermediates with a side η 2 -coordination of N 2 O, which were obtained theoretically when modeling the coordinate of reaction between [ Fe ( CN ) 5 NO ] 2-and hydrazines [12] are also considered in the context of the studies of the linkage isomers for the coordinated small molecules.The structural characteristics of the nitroso complexes [ Ru ( NO )( X ) 5 ] q (X = NH 3 , Cl -, CN -) and trans -[ Ru ( NO )( NH 3 ) 4 ( L )] 3+ (L is imidazole (Im), pyridine (Py), pyrazine (Pyz), Nc) were calculated by the DFT method in [16]. In addition to a stable structure with the η 1 -coordination of the nitroso group through the N atom (GS), each of the above complexes exhibited two metastable isomers MS1 and MS2. The results of the quantum-chemical calculations are presented in [17] for the trans -[ Ru ( L )( NO )( X )] q complexes with two tetradentate two-charge anions (L is porphine (Por); X = Cl -and L is N , N '-ethylenebis(salicylideneiminate) ion (Salen); X = Cl -, H 2 O) in the cis -position with respect to NO. Calculations performed in [16] made it possible to conclude that in a series of amino complexes trans -[ Ru ( NO )( NH 3 ) 4 ( L )] 3+ , the energy difference ∆ E ( MS 1) = E ( MS 1)...

Photolysis of [Ru(bipy)2(NO)Cl](PF6)2 in frozen ionic glass matrices. Evidence for nitrosyl linkage isomerism and NO-loss in a physiologically relevant nitric oxide source

“…Dft calculations of I have been carried out by Di Salvo et al [8] and Sizova and Lubimova [9]. The latter workers have also calculated the optimized geometries for the MS1 (isonitrosyl) and MS2 (side-on nitrosyl) metastable species, and have calculated m(NO) frequencies for the ground state, MS1 and MS2 species.…”