Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
Dalton Trans. 2011 Sep 7;40(33):8377-90. doi: 10.1039/c1dt10609k. Epub 2011 Jul 21.
The article deals with the ruthenium complexes, [(bpy)Ru(Q')(2)] (1-3) incorporating two unsymmetrical redox-noninnocent iminoquinone moieties [bpy = 2,2'-bipyridine; Q' = 3,5-di-tert-butyl-N-aryl-1,2-benzoquinonemonoimine, aryl = C(6)H(5) (Q'(1)), 1; m-Cl(2)C(6)H(3) (Q'(2)), 2; m-(OCH(3))(2)C(6)H(3) (Q'(3)), 3]. 1 and 3 have been preferentially stabilised in the cc-isomeric form while both the ct- and cc-isomeric forms of 2 are isolated [ct: cis and trans and cc: cis and cis with respect to the mutual orientations of O and N donors of two Q']. The isomeric identities of 1-3 have been authenticated by their single-crystal X-ray structures. The collective consideration of crystallographic and DFT data along with other analytical events reveals that 1-3 exhibit the valence configuration of [(bpy)Ru(II)(Q'(Sq))(2)]. The magnetization studies reveal a ferromagnetic response at 300 K and virtual diamagnetic behaviour at 2 K. DFT calculations on representative 2a and 2b predict that the excited triplet (S = 1) state is lying close to the singlet (S = 0) ground state with singlet-triplet separation of 0.038 eV and 0.075 eV, respectively. In corroboration with the paramagnetic features the complexes exhibit free radical EPR signals with g∼2 and (1)HNMR spectra with broad aromatic proton signals associated with the Q' at 300 K. Experimental results in conjunction with the DFT (for representative 2a and 2b) reveal iminoquinone based preferential electron-transfer processes leaving the ruthenium(ii) ion mostly as a redox insensitive entity: (bpy)Ru(II)(Q'(Q))(2) (1(2+)-3(2+)) ⇋ (bpy)Ru(II)(Q(')(Sq))(Q(')(Q)) (1(+)-3(+)) ⇋ [(bpy)Ru(II)(Q(')(Sq))(2)] (1-3) ⇋ (bpy)Ru(II)(Q(')(Sq))(Q(')(Cat))/(bpy)Ru(III)(Q(')(Cat))(2) (1(-)-3(-)). The diamagnetic doubly oxidised state, (bpy)Ru(II)(Q'(Q))(2) in 1(2+)-3(2+) has been authenticated further by the crystal structure determination of the representative (bpy)Ru(II)(Q'(3))(2)(2) 3(2) as well as by its sharp (1)H NMR spectrum. The key electronic transitions in each redox state of 1(n)-3(n) have been assigned by TD-DFT calculations on representative 2a and 2b.
本文研究了钌配合物[(bpy)Ru(Q')(2)]（1-3），其中包含两个不对称的氧化还原非键亚胺醌部分[ bpy = 2,2'-联吡啶；Q'= 3,5-二叔丁基-N-芳基-1,2-苯醌单亚胺，芳基=C 6 H 5（Q'（1）），1；m-Cl 2 C 6 H 3（Q'（2）），2；m-（OCH 3）2 C 6 H 3（Q'（3）），3]。1 和 3 优先稳定在 cc-异构体形式，而 2 的 ct-和 cc-异构体形式均被分离[ct：顺式和反式，cc：顺式和顺式，相对于两个 Q'的 O 和 N 供体的相互取向]。1-3 的异构体身份已通过单晶 X 射线结构得到证实。晶体学和 DFT 数据的综合考虑以及其他分析事件表明，1-3 表现出[(bpy)Ru(II)(Q'(Sq))(2)]的价态配置。磁化研究表明，在 300 K 时存在铁磁响应，在 2 K 时存在虚拟抗磁性行为。对代表性的 2a 和 2b 的 DFT 计算预测，激发三重态（S = 1）状态接近单重态（S = 0）基态，单重态-三重态分离分别为 0.038 eV 和 0.075 eV。与顺磁性特征一致，复合物在 300 K 时表现出自由基 EPR 信号，g∼2 和（1）H NMR 谱与 Q'相关的宽芳香质子信号。实验结果与 DFT（代表性的 2a 和 2b）相结合，揭示了基于亚胺醌的优先电子转移过程，使钌（ii）离子主要保持为氧化还原不敏感实体：(bpy)Ru(II)(Q'(Q))(2)（1(2+)-3(2+））⇋(bpy)Ru(II)(Q(')(Sq))(Q(')(Q))（1(+)-3(+））⇋[(bpy)Ru(II)(Q(')(Sq))(2)]（1-3））⇋(bpy)Ru(II)(Q(')(Sq))(Q(')(Cat))/(bpy)Ru(III)(Q(')(Cat))(2)]（-）（1(-)-3(-)）。在 1(2+)-3(2+)中，代表物[(bpy)Ru(II)(Q'(3))(2)](ClO 4 )(2) [3](ClO 4 )(2) 的晶体结构测定以及其尖锐的（1）H NMR 光谱进一步证实了顺磁性双氧化态(bpy)Ru(II)(Q'(Q))(2)的存在。1(n)-3(n)中每个氧化还原态的关键电子跃迁已通过代表性的 2a 和 2b 的 TD-DFT 计算进行了分配。
