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.