Visible-light NO photolysis of ruthenium nitrosyl complexes with N2O2 ligands bearing π-extended rings and their photorelease dynamics

Minyoung Kim, Seongchul Park, Dayoon Song, Dohyun Moon, Youngmin You, Manho Lim, Hong In Lee

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Abstract

NO photorelease and its dynamics for two {RuNO}6 complexes, Ru(salophen)(NO)Cl (1) and Ru(naphophen)(NO)Cl (2), with salen-type ligands bearing π-extended systems (salophenH2 = N,N′-(1,2-phenylene)-bis(salicylideneimine) and naphophenH2 = N,N′-1,2-phenylene-bis(2-hydroxy-1-naphthylmethyleneimine)) were investigated. NO photolysis was performed under white room light and monitored by UV/Vis, EPR, and NMR spectroscopies. NO photolysis was also performed under 459 and 489 nm irradiation for 1 and 2, respectively. The photochemical quantum yields of the NO photolysis (ΦNO) of both 1 and 2 were determined to be 9% at the irradiation wavelengths. The structural and spectroscopic characteristics of the complexes before and after the photolysis confirmed the conversion of diamagnetic Ru(ii)(L)(Cl)-NO+ to paramagnetic S = ½ Ru(iii)(L)(Cl)-solvent by photons (L = salophen2− and naphophen2−). The photoreleased NO radicals were detected by spin-trapping EPR. DFT and TDDFT calculations found that the photoactive bands are configured as mostly the ligand-to-ligand charge transfer (LLCT) of π(L) → π*(Ru-NO), suggesting that the NO photorelease was initiated by the LLCT. Dynamics of NO photorelease from the complexes in DMSO under 320 nm excitation were investigated by femtosecond (fs) time-resolved mid-IR spectroscopy. The primary photorelease of NO occurred for less than 0.32 ps after the excitation. The rate constants (k−1) of the geminate rebinding of NO to the photolyzed 1 and 2 were determined to be (15 ps)−1 and (13 ps)−1, respectively. The photochemical quantum yields of NO photolysis (ΦNO, λ = 320 nm) were estimated to be no higher than 14% for 1 and 11% for 2, based on the analysis of the fs time-resolved IR data. The results of fs time-resolved IR spectroscopy and theoretical calculations provided some insight into the overall kinetic reaction pathway, localized electron pathway or resonance pathway, of the NO photolysis of 1 and 2. Overall, our study found that the investigated {RuNO}6 complexes, 1 and 2, with planar N2O2 ligands bearing π-extended rings effectively released NO under visible light.

Original languageEnglish
Pages (from-to)11404-11415
Number of pages12
JournalDalton Transactions
Volume51
Issue number30
DOIs
Publication statusPublished - 2022 Jun 28

Bibliographical note

Publisher Copyright:
© 2022 The Royal Society of Chemistry.

All Science Journal Classification (ASJC) codes

  • Inorganic Chemistry

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