Tuning the Spin States of Two Apical Iron(II) Ions in a Pentanuclear Iron(II) Cluster Helicate through the Choice of Anions

摘要

Spin-crossover clusters with iron(II) high nuclearity are rare. By using 3,5-bis(pyridin-2-yl)-1,2,4-triazole (bptH) as the ligand with two bidentate chelating sites, we successfully obtained three pentanuclear iron(II) cluster helicate compounds [{Fe II ( μ -bpt) 3 } 2 Fe II 3 ( μ 3 -O)][Fe II 2 ( μ -Br)( μ -bpt)(NCS) 4 (H 2 O)]·2H 2 O·C 2 H 5 OH ( 1 ), [{Fe II ( μ -bpt) 3 } 2 Fe II 3 ( μ 3 -O)][Fe II 2 ( μ -bpt) 2 (NCS) 4 ] ( 2 ), and [{Fe II ( μ -bpt) 3 } 2 Fe II 3 ( μ 3 -O)]I 2 ·2C 2 H 5 OH ( 3 ). Research on single-crystal structure and magnetism has indicated that tuning the spin state of two iron(II) ions in axial direction is successfully realized by regulating the different counter anions: one apical [Fe II (bpt) 3 ] ? unit exhibits spin-crossover behavior while the other [Fe II (bpt) 3 ] ? unit remains in low spin state in 1 , both apical ions are of high spin states in 2 , and are of low spin states in 3 .