Syntheses, Crystal Structures, and Photoluminescent Properties of a Series of M(II) Coordination Polymers Containing M−X2−M Bridges: From 1-D Chains to 2-D Networks

The novel blue-purple luminescent bridging ligand N,N,N‘,N‘-tetrakis(2-pyridyl)-2,6-pyridinediamine (L) has been
synthesized. The coordination of this ligand with a series of Zn(II), Cd(II), and Hg(II) salts has been investigated. Seven new
complexes (1−7) were obtained and characterized by elemental analyses and single-crystal X-ray analyses. In the compounds Zn2LCl4(1), Hg2LCl4(5), Hg2LBr4(6), and Hg2LI4 (7), each ligand is coordinated to two metal ions, forming dinuclear moieties, which
are further connected via weak intermolecular M···X interactions, affording one-dimensional chains. The complexes {[Cd2L(μ-Cl)2]Cl2}n·nH2O (2) and {[Cd2L(μ-Br)2]Br2}n·nH2O (3) form pseudo-helix 1-D coordination polymers through Cd−X2−Cd (X =
Cl, Br) bridges. The compound {[Cd2L(μ-I)(μ···I)]I2}n (4) forms a zigzag 1-D motif with two kinds of Cd−I−Cd bridges. Furthermore,
the 1-D chains in all these complexes are connected by face-to-face π−π stacking interactions, affording 2-D networks with various
structural geometries. All of these complexes are luminescent in the solid state, with the emission maxima varying in the visible
light region within the range of 440−520 nm.

本研究成功合成了新型的蓝紫色发光桥连配体N,N,N‘,N‘-四(2-吡啶基)-2,6-吡啶二胺（L）。该配体与一系列的Zn(II)、Cd(II)和Hg(II)盐的配位作用已被探究。通过元素分析和单晶X射线分析，获得了七个新的复合物（1-7）。在化合物Zn2LCl4(1)、Hg2LCl4(5)、Hg2LBr4(6)和Hg2LI4(7)中，每个配体均与两个金属离子配位，形成双核基元，这些基元通过弱分子间M···X相互作用进一步连接，从而形成一维链。复合物{[Cd2L(μ-Cl)2]Cl2}n·nH2O(2)和{[Cd2L(μ-Br)2]Br2}n·nH2O(3)通过Cd−X2−Cd（X = Cl, Br）桥形成了假螺旋一维配位聚合物。化合物{[Cd2L(μ-I)(μ···I)]I2}n(4)形成了带有两种Cd−I−Cd桥的锯齿状一维结构。此外，所有这些复合物中的一维链通过面对面π−π堆积相互作用连接，形成了具有多种结构几何形状的二维网络。所有这些复合物在固态下均具有发光特性，其发射光谱在可见光区域内的最大发射波长范围在440−520 nm之间。