Chandra Patra Sarat, Saha Roy Amit, Manivannan Vadivelu, Weyhermüller Thomas, Ghosh Prasanta
Department of Chemistry, R. K. Mission Residential College, Narendrapur, Kolkata-700103, India.
Dalton Trans. 2014 Sep 28;43(36):13731-41. doi: 10.1039/c4dt01241k.
Ruthenium, osmium and rhodium complexes of 1,4-di(3-nitrophenyl)-1,4-diazabutadiene (LDAB) of types trans-[RuII(LDAB)(PPh3)2Cl2] (1), trans-[OsII(LDAB)(PPh3)2Br2] (2) and trans-[Rh(LDAB)(PPh3)2Cl2] (3) are isolated and characterized by elemental analyses, IR, mass and 1H NMR spectra including the single crystal X-ray structure determination of 1·2toluene. The α-diimine fragment of the LDAB ligand in 1·2toluene is deformed, showing a relatively longer -C=N- bond, 1.320 Å, and a shorter =CH–CH= bond, 1.395 Å. Density functional theory (DFT) calculations on trans-[Ru(LDAB)(PMe3)2Cl2] (1Me) and trans-[Os(LDAB)(PMe3)2Br2] (2Me) with singlet spin states authenticated that the closed shell singlet state (CSS) solutions of 1 and 2 are stable and no perturbation occurs because of the diradical open shell singlet (OSS) state. The EPR spectra of 3 and the Mulliken spin density distribution obtained from the DFT calculation on trans-[Rh(LDAB)(PMe3)2Cl2] (3Me) imply that the ground electronic state of 3 can be defined by the [RhIII(LDAB˙−)(PPh3)2Cl2] (3RhL˙) ↔ [RhII(LDAB)(PPh3)2Cl2] (3Rh˙L) resonating states. In solid, the contribution of 3RhL˙ is higher and the gav is 2.018 with Δg = 0.10, whereas in frozen glasses the contribution of 3Rh˙L is higher and the gav is 2.026 with Δg (frozen glasses) = 0.13. The g parameters of the electrogenerated [1]+ (g1 = 2.456, g2 = 2.128 and g3 = 1.624, Δg = 0.824), [2]+ (g1 = 2.599, g2 = 2.041 and g3 = 1.965, Δg = 0.634), [1]− (g1 = 2.138, g2 = 2.109, g3 = 1.978 and Δg = 0.160) and [2]− (g1 = 2.168, g2 = 2.097, g3 = 1.987 and Δg = 0.181) ions and the spin density distributions obtained from the DFT calculations on [1Me]+, [2Me]+, [1Me]− and [2Me]− reveal that the reversible anodic peaks of 1 and 2 at 0.11 and 0.34 V, referenced versus Fc+/Fc couple, are due to the M(III)/M(II) redox couple, while the reversible cathodic waves at −1.27 V and −0.82 V of 1 and 2 are caused by the LDAB/LDAB˙− redox couple. Both [MII(LDAB˙−)(PPh3)2Br2]− and [MI(LDAB)(PPh3)2Br2]− tautomers contribute to the ground electronic states of [1]− (g = 2.075) and [2]− (g = 2.084) ions, which are isoelectronic to 3. Time dependent (TD) DFT calculations and spectroelectrochemical measurements elucidated that lower energy absorption bands of 1 and 2 are caused by the metal to ligand charge transfer (MLCT) that disappears upon oxidation or reduction.
分离出了反式-[RuII(1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯)(三苯基膦)2Cl2] (1)、反式-[OsII(1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯)(三苯基膦)2Br2] (2)和反式-[Rh(1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯)(三苯基膦)2Cl2] (3)类型的钌、锇和铑配合物，并通过元素分析、红外光谱、质谱和1H NMR光谱进行了表征，包括对1·2甲苯进行单晶X射线结构测定。在1·2甲苯中，1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯配体的α - 二亚胺片段发生了变形，显示出相对较长的 -C=N- 键，键长为1.320 Å，以及较短的 =CH–CH= 键，键长为1.395 Å。对具有单重态自旋态的反式-[Ru(1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯)(三甲基膦)2Cl2] (1Me)和反式-[Os(1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯)(三甲基膦)2Br2] (2Me)进行密度泛函理论(DFT)计算证实，1和2的闭壳单重态(CSS)解是稳定的，并且由于双自由基开壳单重态(OSS)态不会发生微扰。3的电子顺磁共振光谱以及对反式-[Rh(1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯)(三甲基膦)2Cl2] (3Me)进行DFT计算得到的穆利肯自旋密度分布表明，3的基态电子态可以由[RhIII(1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯˙−)(三苯基膦)2Cl2] (3RhL˙) ↔ [RhII(1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯)(三苯基膦)2Cl2] (3Rh˙L)共振态来定义。在固体中，3RhL˙的贡献更高，gav为2.018，Δg = 0.10，而在冷冻玻璃中，3Rh˙L的贡献更高，gav为2.026，Δg(冷冻玻璃)= 0.13。电生成的[1]+ (g1 = 2.456，g2 = 2.128，g3 = 1.624，Δg = 0.824)、[2]+ (g1 = 2.599，g2 = 2.041，g3 = 1.965，Δg = 0.634)、[1]− (g1 = 2.138，g2 = 2.109，g3 = 1.978，Δg = 0.160)和[2]− (g1 = 2.168，g2 = 2.097，g3 = 1.987，Δg = 0.181)离子的g参数以及对[1Me]+、[2Me]+、[1Me]−和[2Me]−进行DFT计算得到的自旋密度分布表明，相对于Fc+/Fc电对，1和2在0.11和0.34 V处的可逆阳极峰归因于M(III)/M(II)氧化还原对，而1和2在−1.27 V和−0.82 V处的可逆阴极波是由1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯/1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯˙−氧化还原对引起的。[MII(1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯˙−)(三苯基膦)2Br2]−和[MI(1,4 - 二(3 - 硝基苯基)-1,4 - 二氮杂丁二烯)(三苯基膦)2Br2]−互变异构体都对与3等电子的[1]− (g = 2.075)和[2]− (g = 2.084)离子的基态电子态有贡献。含时(TD)DFT计算和光谱电化学测量表明，1和2的较低能量吸收带是由金属到配体的电荷转移(MLCT)引起的，这种电荷转移在氧化或还原时消失。
