title: Enhanced spin-crossover behavior mediated by supramolecular cooperative interactions.
abstract: Three one-dimensional (1D) hetereobimetallic coordination polymers [Fe(II)(L)2(AgCN)2]·Solv (L = bpt(-), 1; L = Mebpt(-), Solv = 1.75EtOH, 2; L = bpzt(-), 3) with in situ generated AgCN species were synthesized by solvothermal reactions of Fe(II) salt, K[Ag(CN)2], and the corresponding ligands [bptH = 3,5-bis(pyridin-2-yl)-1,2,4-triazole, MebptH = 3-(3-methyl-2-pyridyl)-5-(2-pyridyl)-1,2,4-triazole, and bpztH = 3,5-bis(pyrazin-2-yl)-1,2,4-triazole]. They were further characterized by X-ray crystallography, magnetic and photomagnetic measurements, and differential scanning calorimetry. Single-crystal X-ray analyses show that they are isostructural with 1D zigzag chain structures with rhombus {Fe2Ag2} units, in which the substituted bpt(-) ligand connects the Fe(II) ion and AgCN species in a cis bridging mode. Then the zigzag chains are packed into three-dimensional supramolecular structures by π···π interactions. Most importantly, weak Ag···N interactions (2.750 Å at 150 K) between the π-stacked neighboring chains present in complex 3. Magnetic susceptibility measurements exhibit that complex 1 displays characteristic paramagnetic behavior in the temperature range investigated. Complex 2 undergoes a gradual spin-crossover (SCO) with critical temperatures T(1/2)↓ = 232 K and T(1/2)↑ = 235 K, whereas 3 exhibits an abrupt SCO with critical temperatures T(1/2)↓ = 286 K and T(1/2)↑ = 292 K. The magnetostructural relationships suggest that the magnetic behaviors can be modulated from paramagnetic behavior to abrupt and hysteretic SCO near room temperature through adjustment of the electronic substituent effect and intermolecular interactions.
authors.affiliation: Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-Sen University , Guangzhou 510275, P. R. China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Yan
authors.forename: Jin-Yan
authors.initials: JY
authors.lastname: Li
authors.forename: Tao
authors.initials: T
authors.lastname: Liu
authors.forename: Zhao-Ping
authors.initials: ZP
authors.lastname: Ni
authors.forename: Yan-Cong
authors.initials: YC
authors.lastname: Chen
authors.forename: Fu-Sheng
authors.initials: FS
authors.lastname: Guo
authors.forename: Ming-Liang
authors.initials: ML
authors.lastname: Tong