A Family of Fe(II)/Cl Supramolecular Coordination Systems Incorporating 5,5′-Di(pyridin-2-yl)-3,3′-bi(1,2,4-triazole)

By
using a new N-heterocyclic building block, 5,5′-di­(pyridin-2-yl)-3,3′-bi­(1,2,4-triazole)
(2,2′-H2dbpt), five novel coordination complexes,
Fe4(2,2′-Hdbpt)2­Cl6(H2O)6 (1), [Fe­(2,2′-H2dbpt)­Cl2­·H2O]n (2), [Fe­(2,2′-H2dbpt)­Cl2]n (3), [Fe2(2,2′-H2dbpt)­Cl4]n (4), and [Fe­(2,2′-H2dbpt)0.5Cl2]n (5), based on a Fe­(II)/Cl system with diversiform connectivity from
zero- to two-dimensional (2D) were constructed successfully. By regulating
the metal–ligand ratio and solvents, 2,2′-H2dbpt changed various coordination modes. Consequently, 1 reveals
a discrete Fe4(2,2′-Hdbpt)2­Cl6(H2O)6 supramolecule. 2 and 3 are pseudo-polymorphic. 2 reveals
a helical chain based on the cis-FeCl2N4 unit and the cis-bridging 2,2′-H2dbpt ligand, while 3 reveals a straight-chain
based on the trans-FeCl2N4 unit
and the trans-bridging 2,2′-H2dbpt
ligand. 4 and 5 are also supramolecular
isomers. Different from 2 and 3, both of
them have a cis-FeCl2N4 unit.
Owing to the different rotation angles of pyridine rings in 2,2′-H2dbpt, 4 and 5 reveal a one-dimensional
modified trapezoid chain based on the trans-bridging
2,2′-H2dbpt ligand and a 2D wave-like layer based
on the cis-bridging 2,2′-H2dbpt
ligand, respectively. Furthermore, compound 4 could also
be viewed as a wave banded chain constructed by 3 with μ2-Cl ions replaced by the terminal Cl ions and water molecules
from another perspective. 1 reveals weak antiferromagnetic
behavior. 2, and 3 both reveal paramagnetic
behavior, while 4 and 5 both reveal ferromagnetic
behavior. These results indicate that 2,2′-H2dbpt
is an excellent multi-connection linker to construct supramolecular
coordination complexes with interesting structures and properties.

本研究采用新型氮杂环构筑基元5,5'-二(吡啶-2-基)-3,3'-二(1,2,4-三唑)（2,2'-H₂dbpt，英文全称5,5′-di(pyridin-2-yl)-3,3′-bi(1,2,4-triazole)），成功构建了基于Fe(II)/Cl体系的5种新型配位配合物：Fe₄(2,2'-Hdbpt)₂Cl₆(H₂O)₆(1)、[Fe(2,2'-H₂dbpt)Cl₂·H₂O]ₙ(2)、[Fe(2,2'-H₂dbpt)Cl₂]ₙ(3)、[Fe₂(2,2'-H₂dbpt)Cl₄]ₙ(4)以及[Fe(2,2'-H₂dbpt)₀.₅Cl₂]ₙ(5)，上述配合物具备从零维至二维（2D）的多样连接方式。
通过调控金属与配体的投料比及溶剂种类，2,2'-H₂dbpt可呈现多种配位模式。其中，配合物1为离散的Fe₄(2,2'-Hdbpt)₂Cl₆(H₂O)₆超分子结构。配合物2与3属于假多晶型物：2是以顺式-FeCl₂N₄单元与顺式桥联2,2'-H₂dbpt配体构筑的螺旋链结构，而3则是以反式-FeCl₂N₄单元与反式桥联2,2'-H₂dbpt配体形成的直链结构。
配合物4与5同为超分子异构体，与2、3不同的是，二者均含有顺式-FeCl₂N₄单元。由于2,2'-H₂dbpt中吡啶环的旋转角度存在差异，4呈现为基于反式桥联2,2'-H₂dbpt配体构筑的一维修饰梯形链结构，而5则为基于顺式桥联2,2'-H₂dbpt配体形成的二维波浪状层状结构。此外，从另一视角来看，配合物4可被视为由3中的μ₂-Cl离子被端基氯离子与水分子取代后所形成的波浪带状链结构。
磁性能测试结果显示，配合物1表现出弱反铁磁行为，配合物2与3均呈现顺磁行为，而配合物4与5则均表现出铁磁行为。上述结果证实，2,2'-H₂dbpt是一种优异的多连接桥联配体，可用于构建具有新颖结构与有趣性能的超分子配位配合物。