Isolation and characterization of nitrososulphide species (SNO-/SNOH) stabilized by coordination to iridium (III)

CRISTIÁN HUCK IRIART; ANA FOI; LEANDRO ANDRINI; JOSE M. RAMALLO LÓPEZ; YVES JOLY; FLORENCIA DI SALVO; FABIO DOCTOROVICH

Campinas

Congreso; 27th Annual User Meeting LNLS/CNPEM (RAU); 2017

CNPEM

Nitric oxide (NO) and hydrogen sulfide (H2S)are gaseotransmitters that regulate numerous physiological functions. Base onthe similarity in their physiological effects, it is suggested a possible"link" between these two endogenous species [1]. Although theexistence of S-nitrosothiols (RSNO) in biological systems is known since 1992[2], the existence of the simplest RSNO, the thionitrous acid (HSNO), wasdemonstrated in solution in 2012 [3]. The study of the reaction between H2Sand NO in the context of coordination chemistry was approached by Olabe et al.,who studied the reaction of nitroprusside ([Fe(CN)5(NO)]2?)with HS? and detected formation of the species [Fe(CN)5N(O)SH]3?and then, [Fe(CN)5N(O)S]4?; both characterized insolution [4]. The NO+ in the complex [IrCl5(NO)]?(1) is the most nucleophilic knownto date, specially due to the weak backbonding. On the other hand, thanks tothe inertness of the [IrCl5]? moiety, several N-nitrosoderivatives (RXNO), highly instable species in their free form, were obtainedby reaction of 1 with differentnucleophiles and stabilized by coordination to the metal centre [5]. Thisbackground motivated us to study the reaction of 1 with H2S/HS? as nucleophiles. The reactionwas studied at both 25 °C and ?30 °C in different solvents and using H2S(g),NaSH, and Na2S in acid medium as H2S/HS-sources. In all the studied conditions, a red solid is immediately obtained asproduct. The product was characterized by standard spectroscopic techniques(UV-vis, IR), low-temperature high resolution ESI-MS studies and X-rayAbsorption Fine Structure (XAFS) spectroscopy at the S K-edge and Ir L3-edge.The geometry of the proposed Ir complex was optimized by DFT calculation using ORCA.S K edge XANES and Ir L3 EXAFS were simulated using FDMNES and FEFF9.6.4. The experimental and theoretical results show strong evidence of thestabilization of SNO?/SNOH species through coordination to Ir(III).This work includes evidences for the formation and isolation in solid form of aIrIII-SNOX coordination complex which is unprecedented. Thus, thisstudy opens the way to use transition metals other than iron and ruthenium forS-nitrosylation of sulfides using NO and contributes to the understanding of speciesof physiological relevance.