School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
Inorg Chem. 2010 Oct 18;49(20):9136-50. doi: 10.1021/ic1000842.
A large series of complexes has been synthesized with two chelating, Schiff base azobenzene derivatives connected linearly by coordination to a central nickel(II) or palladium(II) ion. These compounds have the general formulas M(II)(OC(6)H(3)-2-CHNR-4-N═NC(6)H(4)-4-CO(2)Et)(2) [M = Ni; R = n-Bu (3c), n-C(6)H(13) (3d), n-C(8)H(17) (3e), n-C(12)H(25) (3f), Ph (3g), OH (3h), C(6)H(4)-4-CO(2)Et (3i). M = Pd; R = i-Pr (4a), t-Bu (4b), n-Bu (4c), n-C(6)H(13) (4d), n-C(8)H(17) (4e), n-C(12)H(25) (4f), Ph (4g)], M(II)OC(6)H(3)-2-CHN(n-C(8)H(17))-4-N═NC(6)H(4)-4-CO(2)(n-C(8)H(17)) [M = Ni (9), Pd (10)], M(II)OC(6)H(3)-2-CHN(n-C(8)H(17))-4-N═NC(6)H(4)-4-C(6)H(4)-4-O(n-C(7)H(15)) [M = Ni (14), Pd (15)], and M(II)OC(6)H(3)-2-CHN(CMe(2))-4-N═NC(6)H(4)-4-CO(2)Et [M = Ni (17), Pd (18); the CMe(2) groups are connected]. These compounds have been characterized by using various physical techniques including (1)H NMR spectroscopy and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Single-crystal X-ray structures have been obtained for two pro-ligands and five complexes (3e, 4e, 14, 15, and 17). The latter always show a strictly square planar arrangement about the metal center, except for the Ni(II) complex of a salen-like ligand (17). In solution, broadened (1)H NMR signals indicate distortions from square planar geometry for the bis-chelate Ni(II) complexes. Electronic absorption spectroscopy and ZINDO_S (Zerner's intermediate neglect of differential overlap) and TD-DFT (time-dependent density functional theory) calculations show that the lowest energy transition has metal-to-ligand charge-transfer character. The λ(max) of this band lies in the range of 409-434 nm in dichloromethane, and replacing Ni(II) with Pd(II) causes small blue-shifts. Dichroic ratios measured in various liquid crystal hosts show complexation-induced increases with Ni(II), but using Pd(II) has a detrimental effect.
已经合成了一系列由两个螯合的席夫碱偶氮苯衍生物通过配位连接到中心镍（II）或钯（II）离子线性连接的配合物。这些化合物具有通式 M(II)(OC(6)H(3)-2-CHNR-4-N═NC(6)H(4)-4-CO(2)Et)(2) [M = Ni; R = n-Bu (3c), n-C(6)H(13) (3d), n-C(8)H(17) (3e), n-C(12)H(25) (3f), Ph (3g), OH (3h), C(6)H(4)-4-CO(2)Et (3i). M = Pd; R = i-Pr (4a), t-Bu (4b), n-Bu (4c), n-C(6)H(13) (4d), n-C(8)H(17) (4e), n-C(12)H(25) (4f), Ph (4g)], M(II)OC(6)H(3)-2-CHN(n-C(8)H(17))-4-N═NC(6)H(4)-4-CO(2)(n-C(8)H(17)) [M = Ni (9), Pd (10)], M(II)OC(6)H(3)-2-CHN(n-C(8)H(17))-4-N═NC(6)H(4)-4-C(6)H(4)-4-O(n-C(7)H(15)) [M = Ni (14), Pd (15)], 和 M(II)OC(6)H(3)-2-CHN(CMe(2))-4-N═NC(6)H(4)-4-CO(2)Et [M = Ni (17), Pd (18); 连接的 CMe(2) 基团]。这些化合物已经通过使用各种物理技术进行了表征，包括（1）H NMR 光谱和基质辅助激光解吸/电离（MALDI）质谱。获得了两个前配体和五个配合物（3e、4e、14、15 和 17）的单晶 X 射线结构。后者始终显示出金属中心严格的平面正方形排列，除了类似 salen 的配体的 Ni(II)配合物（17）。在溶液中，宽化的（1）H NMR 信号表明双螯合 Ni(II)配合物的扭曲偏离平面正方形几何形状。电子吸收光谱和 ZINDO_S（Zerner 的中间忽略微分重叠）和 TD-DFT（时间相关密度泛函理论）计算表明，最低能量跃迁具有金属到配体电荷转移的性质。该带的 λ(max)在二氯甲烷中为 409-434nm，用 Pd(II)取代 Ni(II)会导致小的蓝移。在各种液晶主体中测量的二向色性比表明，与 Ni(II)络合诱导增加，但使用 Pd(II)会产生不利影响。
