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) (original) (raw)

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](ClO 4) 3 and [4](ClO 4) 2 , respectively. Single crystals of protonated material [4-H + ](ClO 4) 4 • 2H 2 O reveal a RuN -O bond angle of 176.1(7)°and triply bonded NO 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)](ClO 4) • 4.5H 2 O and [Ru(trpy)-(L-H)(CH 3 CN)](ClO 4) 3 • H 2 O. 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 Ru II-NO • in isolated or electrogenerated [4] 2+ exhibits an EPR spectrum with g 1) 2.020, g 2) 1.995, and g 3) 1.884 in CH 3 CN at 110 K, reflecting partial metal contribution to the singly occupied molecular orbital (SOMO); 14 N (NO) hyperfine splitting (A 2) 30 G) was also observed. The plot of ν(NO) versus E°({RuNO} 6 f {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-NO 2system in the presence of OHwith k) 2.02 × 10-4 s-1 at 303 K. In the presence of a steady flow of dioxygen gas, the Ru II-NO • state in [4] 2+ oxidizes to [4] 3+ through an associatively activated pathway (∆S q)-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 (k NO) 2.0 × 10-1 min-1 and t 1/2 ≈ 3.5 min) with the concomitant formation of the solvate [Ru II (trpy)(L)(CH 3 CN)] 2+ [2′] 2+. The photoreleased NO can be trapped as an Mb-NO adduct.