Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
Dalton Trans. 2011 Dec 14;40(46):12527-39. doi: 10.1039/c1dt10761e. Epub 2011 Oct 11.
The present article describes ruthenium nitrosyl complexes with the {RuNO}(6) and {RuNO}(7) notations in the selective molecular frameworks of Ru(II)([9]aneS(3))(bpy)(NO(+)) (4(3+)), Ru(II)([9]aneS(3))(pap) (NO(+)) (8(3+)) and Ru(II)([9]aneS(3))(bpy)(NO˙) (4(2+)), Ru(II)([9]aneS(3))(pap)(NO˙) (8(2+)) ([9]aneS(3) = 1,4,7-trithiacyclononane, bpy = 2,2'-bipyridine, pap = 2-phenylazopyridine), respectively. The nitrosyl complexes have been synthesized by following a stepwise synthetic procedure: {Ru(II)-Cl} → {Ru(II)-CH(3)CN} → {Ru(II)-NO(2)} → {Ru(II)-NO(+)} → {Ru(II)-NO˙}. The single-crystal X-ray structure of 4(3+) and DFT optimised structures of 4(3+), 8(3+) and 4(2+), 8(2+) establish the localised linear and bent geometries for {Ru-NO(+)} and {Ru-NO˙} complexes, respectively. The crystal structures and (1)H/(13)C NMR suggest the [333] conformation of the coordinated macrocyclic ligand ([9]aneS(3)) in the complexes. The difference in π-accepting strength of the co-ligands, bpy in 4(3+) and pap in 8(3+) (bpy < pap) has been reflected in the ν(NO) frequencies of 1945 cm(-1) (DFT: 1943 cm(-1)) and 1964 cm(-1) (DFT: 1966 cm(-1)) and E°({Ru(II)-NO(+)}/{Ru(II)-NO˙}) of 0.49 and 0.67 V versus SCE, respectively. The ν(NO) frequency of the reduced {Ru-NO˙} state in 4(2+) or 8(2+) however decreases to 1632 cm(-1) (DFT: 1637 cm(-1)) or 1634 cm(-1) (DFT: 1632 cm(-1)), respectively, with the change of the linear {Ru(II)-NO(+)} geometry in 4(3+), 8(3+) to bent {Ru(II)-NO˙} geometry in 4(2+), 8(2+). The preferential stabilisation of the eclipsed conformation of the bent NO in 4(2+) and 8(2+) has been supported by the DFT calculations. The reduced {Ru(II)-NO˙} exhibits free-radical EPR with partial metal contribution revealing the resonance formulation of {Ru(II)-NO˙}(major)↔{Ru(I)-NO(+)}(minor). The electronic transitions of the complexes have been assigned based on the TD-DFT calculations on their DFT optimised structures. The estimated second-order rate constant (k, M(-1) s(-1)) of the reaction of the nucleophile, OH(-) with the electrophilic {Ru(II)-NO(+)} for the bpy derivative (4(3+)) of 1.39 × 10(-1) is half of that determined for the pap derivative (8(3+)), 2.84 × 10(-1) in CH(3)CN at 298 K. The Ru-NO bond in 4(3+) or 8(3+) undergoes facile photolytic cleavage to form the corresponding solvent species {Ru(II)-CH(3)CN}, 2(2+) or 6(2+) with widely varying rate constant values, (k(NO), s(-1)) of 1.12 × 10(-1) (t(1/2) = 6.2 s) and 7.67 × 10(-3) (t(1/2) = 90.3 s), respectively. The photo-released NO can bind to the reduced myoglobin to yield the Mb-NO adduct.
本文描述了具有 {RuNO}(6) 和 {RuNO}(7) 符号的钌亚硝酰配合物，它们位于 Ru(II)([9]aneS(3))(bpy)(NO(+)) (4(3+))、Ru(II)([9]aneS(3))(pap)(NO(+)) (8(3+)) 和 Ru(II)([9]aneS(3))(bpy)(NO˙) (4(2+))、Ru(II)([9]aneS(3))(pap)(NO˙) (8(2+))（[9]aneS(3) = 1,4,7-三硫杂环壬烷，bpy = 2,2'-联吡啶，pap = 2-苯基偶氮吡啶）的选择性分子框架中。亚硝酰配合物通过以下逐步合成程序合成：{Ru(II)-Cl} → {Ru(II)-CH(3)CN} → {Ru(II)-NO(2)} → {Ru(II)-NO(+)} → {Ru(II)-NO˙}。4(3+) 的单晶 X 射线结构和 4(3+)、8(3+) 和 4(2+)、8(2+) 的 DFT 优化结构确定了 {Ru-NO(+)} 和 {Ru-NO˙} 配合物的局部线性和弯曲几何形状。晶体结构和 1H/13C NMR 表明配合物中配位大环配体 ([9]aneS(3)) 采用 [333] 构象。协同配体 bpy 在 4(3+) 中的 π-接受强度和 pap 在 8(3+) 中的 π-接受强度（bpy < pap）的差异反映在 ν(NO) 频率 1945 cm(-1)（DFT：1943 cm(-1)）和 1964 cm(-1)（DFT：1966 cm(-1)）以及 E°({Ru(II)-NO(+)}/{Ru(II)-NO˙}) 为 0.49 和 0.67 V 相对于 SCE。然而，{Ru-NO˙} 还原态的 ν(NO) 频率在 4(2+) 或 8(2+) 中降低至 1632 cm(-1)（DFT：1637 cm(-1)）或 1634 cm(-1)（DFT：1632 cm(-1)），其中 4(3+)、8(3+) 中的线性 {Ru(II)-NO(+)} 几何结构变为 4(2+)、8(2+) 中的弯曲 {Ru(II)-NO˙} 几何结构。DFT 计算支持 4(2+) 和 8(2+) 中弯曲 NO 优先稳定的交错构象。还原的 {Ru(II)-NO˙} 表现出自由基 EPR，具有部分金属贡献，表明共振形式为 {Ru(II)-NO˙}(主要)↔{Ru(I)-NO(+)}(次要)。基于对其 DFT 优化结构的 TD-DFT 计算，分配了配合物的电子跃迁。用 OH(-) 作为亲核试剂与电正性 {Ru(II)-NO(+)} 反应的速率常数 (k, M(-1) s(-1)) 估计为 1.39 × 10(-1)，对于 bpy 衍生物 (4(3+))，是与 pap 衍生物 (8(3+)) 2.84 × 10(-1) 的一半，在 298 K 下在 CH(3)CN 中进行。4(3+) 或 8(3+) 中的 Ru-NO 键易于光解断裂，形成相应的溶剂物种 {Ru(II)-CH(3)CN}、2(2+) 或 6(2+)，其速率常数值变化很大，分别为 1.12 × 10(-1) (t(1/2) = 6.2 s) 和 7.67 × 10(-3) (t(1/2) = 90.3 s)。光释放的 NO 可以与还原的肌红蛋白结合生成 Mb-NO 加合物。
