Substituent group tuned structural dimensionalities and magnetic properties of V-shaped bis-pyridyl ligands based Fe(II) coordination polymers

Abstract

A series of V-shaped thioether-based bis-pyridyl ligands containing different substituent groups have been successfully employed to assemble Fe(II)-based complexes by using H-tube diffusion method, resulting in six new coordination polymers with different structure types, [Fe(L1)(SCN)2]n·1.5nCH3OH (1), [Fe(L1)(SeCN)2]n·nCH3OH·nH2O (2), [Fe(L2)(SCN)2]n (3), [Fe(L2)(SeCN)2]n (4), [Fe(L3)(SCN)2]n (5), [Fe(L3)(SeCN)2]n (6) (L1 = 1,3-bis((pyridin-4-ylthio)methyl)benzene, L2 = 4,4′-(((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(sulfanediyl))dipyridine, L3 = 4,4′-(((perchloro-1,3-phenylene)bis(methylene))bis(sulfanediyl))dipyridine). All the complexes have been structurally characterized by elemental analysis, FT-IR spectroscopy, single crystal and powder X-ray diffraction. The single crystal structure analysis revealed the one-dimensional (1D) chain for complexes 1–4, in which the different conformation the ligand adopted was found, and two-dimensional (2D) grid-like network for 5 and 6, respectively. Investigation of the temperature dependent magnetic susceptibilities discovered the always high spin state of the Fe(II) ion in all the compounds within the whole temperature range of 10-300 K, except complex 2 with the obvious temperature dependent color change from yellow (293 K) to violet (100 K). The thermo- and photomagnetic property study for complex 2 showed the incomplete spin transition behavior with interesting light-induced excited spin state trapping effect (LIESST). The current results indicated that the steric effect and/or the electronegativity of the substitute groups on the ligand and the conformation of the ligand could play an important role on the topologic structure of the target products, therefore putting obvious influence on spin state of the central Fe(II) ion.