文摘
To carry and deliver nitric oxide with a controlled redox state and rate is crucial for its pharmaceutical/medicinal applications. In this study, the capability of cationic {Fe(NO)2}9 dinitrosyl iron complexes (DNICs) [(RDDB)Fe(NO)2]+ (R = Me, Et, Iso; RDDB = <i>N,Ni>′-bis(2,6-dialkylphenyl)-1,4-diaza-2,3-dimethyl-1,3-butadiene) carrying nearly unperturbed nitric oxide radical to form [(RDDB)Fe(NO)2(•NO)]+ was demonstrated and characterized by IR, UV–vis, EPR, NMR, and single-crystal X-ray diffractions. The unique triplet ground state of [(RDDB)Fe(NO)2(•NO)]+ results from the ferromagnetic coupling between two strictly orthogonal orbitals, one from Fe d<i>zi>2 and the other a π*op orbital of a unique bent axial NO ligand, which is responsible for the growth of a half-field transition (Δ<i>Mi>S = 2) from 70 to 4 K in variable-temperature EPR measurements. Consistent with the NO radical character of coordinated axial NO ligand in complex [(MeDDB)Fe(NO)2(•NO)]+, the simple addition of MeCN/H2O into CH2Cl2 solution of complexes [(RDDB)Fe(NO)2(•NO)]+ at 25 °C released NO as a neutral radical, as demonstrated by the formation of [S5Fe(NO)2]− from [S5Fe(μ-S)2FeS5]2–.