Construction of Tube- and Ladderlike Copper(II) Coordination Polymers Based on the Nicotinato Tecton

Three 1-D copper(II) coordination polymers have been obtained by using the nicotinato anion
(NA-) as a bridge, and 2,2‘-bipyridine or dicyanamide (dca) as coligands: 

Cu2(bipy)2(NA)2](ClO4)2·H2O 1,

Cu2(Me2bipy)2(NA)2](ClO4)2 2,

Cu3(NA)4(dca)2(H2O)8]·2H2O 3 (bipy = 2,2‘-bipyridine; Me2bipy = 4,4‘-dimethyl-2,2‘-bipyridine, dca = dicyanamide anion). The metal−ligand association in compounds 1 and 2 is very similar and
generates tubelike coordination polymers, which are constructed from pairs of copper atoms connected through two
carboxylato groups from two NA- ligands. Each pyridyl moiety from the NA- ligand coordinates at the apical position
of the copper ions from another pair, resulting in chains running along the crystallographic c axis. The structure of
3 consists of infinite ladderlike chains:  the rungs are formed by trinuclear [Cu3] moieties, with the copper(II) ions
connected through NA- bridges, the ladder sides being constructed from dca- bridging ligands. The cryomagnetic
investigation of the three compounds reveals weak antiferromagnetic interactions mediated by the nicotinato ligand,
1:  J = −7.3 cm-1, 2: −15.3 cm-1, 3: −0.58 cm-1.

本研究以烟酸根阴离子（nicotinato anion, NA⁻）作为桥联配体，2,2'-联吡啶（2,2'-bipyridine）或二氰胺根（dicyanamide, dca）作为辅助配体，成功合成了三种一维铜(II)配位聚合物，分别为：
[Cu₂(bipy)₂(NA)₂](ClO₄)₂·H₂O（编号1）、
[Cu₂(Me₂bipy)₂(NA)₂](ClO₄)₂（编号2）、
[Cu₃(NA)₄(dca)₂(H₂O)₈]·2H₂O（编号3）；
其中bipy=2,2'-联吡啶，Me₂bipy=4,4'-二甲基-2,2'-联吡啶，dca=二氰胺根阴离子。
化合物1与2的金属-配体配位模式高度相似，均构筑得到管状配位聚合物：其结构由成对铜原子构成，每对铜原子通过两个烟酸根配体的两个羧基基团实现桥联；烟酸根配体上的每个吡啶基团均与另一对铜离子的轴向配位位点结合，最终形成沿晶体学c轴延伸的一维链状结构。
化合物3的结构为无限长梯状链：梯级由三核[Cu₃]结构单元构成，铜(II)离子通过烟酸根配体桥联，梯边则由二氰胺根桥联配体构筑而成。
对三种化合物的低温磁学研究表明，其磁相互作用均为烟酸根配体介导的弱反铁磁耦合：化合物1的磁耦合常数J=-7.3 cm⁻¹，化合物2为-15.3 cm⁻¹，化合物3为-0.58 cm⁻¹。