Photoinduced NO and HNO Production from Mononuclear {FeNO}⁶ Complex Bearing a Pendant Thiol

Abstract

Light triggers the formation of HNO from a metal− nitrosyl species, facilitated by an intramolecular pendant thiol proton. Two {FeNO} 6 complexes (the Enemark−Felthan notation), [Fe(NO)( TMS PS2)( TMS PS2H)] (1, TMS PS2H 2 = 2,2′dimercapto-3,3′-bis(trimethylsilyl)diphenyl)phenylphosphine; H is a dissociable proton) with a pendant thiol and [Fe(NO)-( TMS PS2)( TMS PS2CH 3 )] (2) bearing a pendant thioether, are spectroscopically and structurally characterized. Both complexes are highly sensitive to visible light. Upon photolysis, complex 2 undergoes NO dissociation to yield a mononuclear Fe(III) complex, [Fe( TMS PS2)( TMS PS2CH 3 )] (3). In contrast, the pendant SH of 1 can act as a trap for the departing NO radical upon irradiation, resulting in the formation of an intermediate A with an intramolecular [SH•••ON−Fe] interaction. As suggested by computational results (density functional theory), the NO stretching frequency (ν NO ) is sensitive to the intramolecular interaction between the pendant ligand and the iron-bound NO, and a shift of ν NO from 1833 (1) to 1823 cm −1 (A) is observed experimentally. Subsequent photolysis of the intermediate A results in HNO production and a thiyl group that then coordinates to the Fe center for the formation of [Fe( TMS PS2) 2 ] (4). In contrast with the common acid−base coupling pathway, the HNO is not voluntarily yielded from 1 but rather is generated by the photopromoted pathway. The photogenerated HNO can further react with [Mn III ( TMS PS3)(DABCO)] ( TMS PS3H 3 = (2,2′2′′-trimercapto-3,3′,3′′tris(trimethylsilyl)triphenylphosphine; DABCO = 1,4-diazabicyclo[2.2.2]octane) in organic media to yield anionic [Mn(NO)-( TMS PS3)] − (5 − ) with a {MnNO} 6 electronic configuration, whereas [Mn III ( TMS PS3)(DABCO)] reacts with NO gas for the formation of a {MnNO} 5 species, [Mn(NO)( TMS PS3)] (6). Effective differentiation of the formation of HNO from complex 1 with the pendant SH versus NO from 2 with the pendant SMe is achieved by the employment of [Mn III ( TMS PS3)(DABCO)].

NO Reduction to N2O Triggered by a Dinuclear Dinitrosyl Iron Complex via the Associated Pathways of Hyponitrite Formation and NO Disproportionation

“…The crystallographic structure of complex 3 is depicted in Figure , and the selected bond distances and angles are presented in Table S1. The bond lengths of Fe–N­(O) range from 1.681(5) to 1.703(5) Å, and the N–O bond lengths are within 1.154(6)–1.174(6) Å, consistent with the published Fe–N­(O) and N–O bond lengths of {Fe­(NO) 2 } 9 DNICs. − It is noticed that complex 3 shows linkage isomers, that is, complex 3 with κ 2 - O , N -NO 2 linkage (O(5)–N(5)–O(6) (75%)) and complex 3 ′ with terminal η 2 - O -ONO linkage (O(5′)–N(5′)–O(6′) (25%)). Variable-temperature UV–vis spectra indicate that the linkage isomers of complex 3 with κ 2 - O , N -NO 2 and complex 3 ′ with η 2 - O -ONO are interconvertible, as shown in Figure S5.…”

“…The oven temperature was kept at 40 °C and then increased to 240 °C (rate 20 °C/min), and the detector was heated to 280 °C. The identification and quantification of N 2 O were achieved by utilizing a gastight syringe to acquire 0.1 mL of sample headspace gas and injected into GC. ,, The calibration curves were derived by the injection of various amounts of NO ((10% NO + 90% N 2 ; 2.2, 4.5, 6.8, 11.2, and 22.4 mL) and pure N 2 O (0.10, 0.15, 0.20, 0.30, and 0.50 mL) into a vial (65 mL) containing 2 mL of THF. The calibration curve was plotted in Figure S2.…”

Generation of a Sulfinamide Species from Facile N–O Bond Cleavage of Nitrosobenzene by a Thiolate-Bridged Diiron Complex

“…Complex 4 possesses an S = 0 ground state as suggested by the 1 H NMR spectroscopic result wherein all of its unambiguously assigned proton resonances located in the common diamagnetic range. The IR spectrum of 4 exhibits a diagnostic strong absorption peak at 1805 cm –1 assigned for the N–O stretch vibration of terminally coordinated NO ligand (Figure b), , which is in good agreement with its molecular structure (Figure c). In addition, the N–O stretch vibration frequency of the bridging PhNO ligand in 4 is identical to that found for 2a (Figure b).…”

When NO. Is not Enough: Chemical Systems, Advances and Challenges in the Development of NO. and HNO Donors for Old and Current Medical Issues

“…Another exciting case is based on the photorelease of HNO. Lee and collaborators developed a nitrosyl iron complex containing the 2,2′‐dimercapto‐3,3′‐bis(trimethylsilyl)diphenyl)phenylphosphine ( TMS PS2H 2 ) ligand [142] . This compound upon light irradiation (>400 nm) showed formation of HNO, which was associated to a reduction of NO .…”