Formation, reactivity, and photorelease of metal bound nitrosyl in [Ru(trpy)(L)(NO)]n+ (trpy = 2,2':6',2''-Terpyridine, L = 2-Phenylimidazo[4,5-f]1,10-phenanthroline)

Maji, Somnath ; Sarkar, Biprajit ; Patra, Malay ; Das, Atanu Kumar ; Mobin, Shaikh M. ; Kaim, Wolfgang ; Lahiri, Goutam Kumar (2008) Formation, reactivity, and photorelease of metal bound nitrosyl in [Ru(trpy)(L)(NO)]n+ (trpy = 2,2':6',2''-Terpyridine, L = 2-Phenylimidazo[4,5-f]1,10-phenanthroline) Inorganic Chemistry, 47 (8). pp. 3218-3227. ISSN 0020-1669

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Official URL: http://pubs.acs.org/doi/abs/10.1021/ic702160w

Related URL: http://dx.doi.org/10.1021/ic702160w

Abstract

Nitrosyl complexes with {Ru-NO}6 and {Ru-NO}7 configurations have been isolated in the framework of [Ru(trpy)(L)(NO)]n+ [trpy = 2,2':6',2''-terpyridine, L = 2-phenylimidazo[4,5-f]1,10-phenanthroline] as the perchlorate salts [4](ClO4)3 and [4](ClO4)2, respectively. Single crystals of protonated material [4-H+](ClO4)4.2H2O reveal a Ru-N-O bond angle of 176.1(7)° and triply bonded N-O with a 1.127(9) Å bond length. Structures were also determined for precursor compounds of [4]3+ in the form of [Ru(trpy)(L)(Cl)](ClO4).4.5H2O and [Ru(trpy)(L-H)(CH3CN)](ClO4)3.H2O. In agreement with largely NO centered reduction, a sizable shift in ν(NO) frequency was observed on moving from [4]3+ (1953 cm-1) to [4]2+ (1654 cm-1). The RuII-NO°in isolated or electrogenerated [4]2+ exhibits an EPR spectrum with g1 = 2.020, g2 = 1.995, and g3 = 1.884 in CH3CN at 110 κ, reflecting partial metal contribution to the singly occupied molecular orbital (SOMO); 14N (NO) hyperfine splitting (A2 = 30 G) was also observed. The plot of ν(NO) versus E°({RuNO}6 → {RuNO}7) for 12 analogous complexes [Ru(trpy)(L')(NO)]n+ exhibits a linear trend. The electrophilic Ru-NO+ species [4]3+ is transformed to the corresponding Ru-NO2- system in the presence of OH- with k = 2.02 × 10-4 s-1 at 303 κ. In the presence of a steady flow of dioxygen gas, the RuII-NO·state in [4]2+ oxidizes to [4]3+ through an associatively activated pathway (ΔS ≠-190.4 J K-1 M-1) with a rate constant (k [s-1]) of 5.33 × 10-3. On irradiation with light (Xe lamp), the acetonitrile solution of paramagnetic [Ru(trpy)(L)(NO)]2+ ([4]2+) undergoes facile photorelease of NO (kNO = 2.0 × 10-1 min-1 and t½ ≈ 3.5 min) with the concomitant formation of the solvate [RuII(trpy)(L)(CH3CN)]2+ [2']2+. The photoreleased NO can be trapped as an Mb-NO adduct.

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