Co-ligand and Solvent Effects on the Spin-Crossover Behaviors of PtS-type Porous Coordination Polymers
- 化学化工－已发表论文 
In our previous work (Chen, X.-Y.; et al. Chem. Commun. 2013, 49, 10977-10979), we have reported the crystal structure and spin-crossover properties of a compound [Fe(NCS)(2)(tppm)]center dot S [1 center dot S, tppm = 4,4',4 '',4'''-tetrakis(4-pyridylethen-2-yl)tetraphenylmethane, S = 5CH(3)OH center dot 2CH(2)Cl(2)]. Here, its analogues [Fe(X)2(tppm)]center dot S [X = NCSe-, NCBH3-, and N(CN)(2)(-) for compounds 2 center dot S, 3 center dot S, and 4 center dot S, respectively] have been synthesized and characterized by variable-temperature X-ray diffraction and magnetic measurements. The crystal structure analyses of 2 center dot S and 3 center dot S reveal that both compounds possess the same topologic framework (PtS-type) building from the tetrahedral ligand tppm and planar unit FeX2; the framework is twofold self-interpenetrated to achieve one-dimensional open channels occupied by solvent molecules. Powder X-ray diffraction study indicates the same crystal structure for 4. The average values of Fe-N distances observed, respectively, at 100, 155, and 220 K for the Fe1/Fe2 centers are 1.969/2.011, 1.970/2.052, and 2.098/2.136 angstrom for 2 center dot S, whereas those at 110, 175, and 220 K are 1.972/2.013, 1.974/2.056, and 2.100/2.150 A for 3 center dot S, indicating the presence of a two-step spin crossover in both compounds. Temperature-dependent magnetic susceptibilities (chi T-M) confirm the two-step spin-crossover behavior at 124 and 200 K in 2 center dot S, 151 and 225 K in 3 center dot S, and 51 and 126 K in 4 center dot S, respectively. The frameworks of 2-4 are reproducible upon solvent exchange and thereafter undergo solvent-dependent spin-crossover behaviors.