Structures, Magnetic Properties, and Photoluminescence of Dicarboxylate Coordination Polymers of Mn, Co, Ni, Cu Having N‑(4-Pyridylmethyl)-1,8-naphthalimide
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Supramolecular interactions of N-(4-pyridylmethyl)-1,8-naphthalimide (L) and flexibility of intervening units of dicarboxylate ligands contribute to formation of different types of coordination polymers such as [MnL2(Adp)(H2O)2]n·2nH2O (1), [CoL2(Fum)(H2O)2]n·2nH2O (2), [CoL2(Adp)(H2O)2]n·2nH2O (3), [NiL(Fum)(H2O)3]n·H2O (4), [CuL2(Fum)]n·nH2O (5), [CuL(Mal)]n (6), and [Cu3L6(Adp)3(H2O)3]n (7) (where Adp = adipate, Fum = fumarate, and Mal = malonate). These coordination polymers are structurally characterized. Coordination polymers 1 and 3 are isostructural having three-dimensional (3D) supramolecular layer-like structures. Coordination polymer 2 forms a two-dimensional (2D) supramolecular network through C–H···π and O···π interactions. Coordination polymer 4 forms H-bonded 3D chainlike supramolecular architecture. Coordination polymer 5 forms a 3D supramolecular sheet-like structure, whereas coordination polymer 6 and coordination polymer 7 forms a 2D lamellar structure through π···π and C–H···π interactions. Manganese coordination polymer 1 shows weak antiferromagnetic interactions between chains at low temperature and also exhibits single chain magnetic behavior. Coordination polymers 2 and 3 show saturation value of magnetic moment at 2 K and 7 T, which are lower than the spin-only Co(II) ion. Coordination polymer 4 show spin-only values for Ni(II) ion. The room-temperature χMT value for coordination polymer 5 is close to the spin-only value for two Cu(II) ions. With lowering of the temperature, the χMT value remains constant to 35 K, from where the value begins to decrease to a minimum at 2 K. For copper coordination polymer 6 value of χMT smoothly decreases with lowering of the temperature to attain a quasi plateau between 80 K and 35 K, and it further sharply increases at 2 K. Coordination polymer 7 shows spin-only Cu(II) ion. These coordination polymers in solid state show quenching of fluorescence emission of ligand L, as well as a shift of emission toward a shorter wavelength.
N-(4-吡啶甲基)-1,8-萘酰亚胺（N-(4-pyridylmethyl)-1,8-naphthalimide，记为配体L）与二羧酸配体桥联单元的柔性共同作用，促成了多种配位聚合物的构筑，具体包括：[MnL₂(Adp)(H₂O)₂]ₙ·2nH₂O（1）、[CoL₂(Fum)(H₂O)₂]ₙ·2nH₂O（2）、[CoL₂(Adp)(H₂O)₂]ₙ·2nH₂O（3）、[NiL(Fum)(H₂O)₃]ₙ·H₂O（4）、[CuL₂(Fum)]ₙ·nH₂O（5）、[CuL(Mal)]ₙ（6）以及[Cu₃L₆(Adp)₃(H₂O)₃]ₙ（7）（其中Adp为己二酸根（adipate），Fum为富马酸根（fumarate），Mal为丙二酸根（malonate））。上述所有配位聚合物均已完成结构表征。配位聚合物1与3为同构结构，均具有三维（3D）超分子层状结构。配位聚合物2通过C-H···π与O···π相互作用构筑二维（2D）超分子网络。配位聚合物4通过氢键构建三维链状超分子架构。配位聚合物5具有三维超分子片层结构；而配位聚合物6与7则通过π···π及C-H···π相互作用形成二维层状结构。锰基配位聚合物1在低温下展现出链间弱反铁磁相互作用，同时表现出单链磁行为。配位聚合物2与3在2 K、7 T条件下呈现磁矩饱和值，该值低于Co(II)离子的自旋仅磁矩理论值。配位聚合物4的磁学响应匹配Ni(II)离子的自旋仅磁矩理论值。室温下配位聚合物5的摩尔磁化率-温度积（χMT）与两个Cu(II)离子的自旋仅磁矩理论值相近。随着温度降低，其χMT值在35 K前保持恒定，此后逐渐下降并在2 K时达到最小值。对于铜基配位聚合物6，其χMT值随温度降低平稳下降，在80 K至35 K区间达到准平台，随后在2 K时急剧上升。配位聚合物7的磁学行为符合Cu(II)离子的自旋仅磁矩理论值。上述固态配位聚合物均表现出配体L的荧光发射猝灭现象，且发射峰发生蓝移（即向短波长方向移动）。
