Spin Crossover in Polymeric Materials Using Schiff Base Functionalized Triazole Ligands

Abstract

Abstract Functionalized 1,2,4‐( R )‐triazole‐based Schiff base (R‐N=CH‐R′) ligands have been incorporated into spin crossover 1D materials of the general formula [Fe(Xtrz) 3 ](A) 2 · 2H 2 O (A = BF 4 , ClO 4 , Br, NO 3 ; Xtrz = triazole liands). The ligand N ‐salicylidene 4‐amino‐1,2,4‐triazole (Hsaltrz) and the novel ligand N ‐cinimalidene 4‐amino‐1,2,4‐triazole (Hcintrz) were targeted to assess the implication of incorporating various aromatic functional groups on the spin crossover properties of this well‐known family of one‐dimensional materials. Magnetic susceptibility measurements on the polycrystalline powdered materials [Fe(Hsaltrz) 3 ](A) 2 · 2H 2 O [A = BF 4 ( 1 ), ClO 4 ( 2 ), Br ( 3 )] and [Fe(Hcintrz) 3 ](A) 2 · 1.5(H 2 O) [A = BF 4 ( 4 ), ClO 4 ( 5 ), Br ( 6 )] revealed spin transitions over the range T ${1 \over 2}$ = 100–225 K. The spin crossover properties of the dehydrated materials were also investigated [ 1 – 6(dh) ]. In attempts to prepare single crystals of these materials a dinuclear {[Fe 2 (Hsaltrz) 5 (NCS) 4 ] · 2MeOH ( 7 )} and a trinuclear {[Fe 3 (Hsaltrz) 6 (H 2 O) 2 (EtOH) 4 ](ClO 4 ) 6 · 2(EtOH) ( 8 )} complex were obtained; these materials remain high spin over all temperatures and display weak antiferromagnetic exchange coupling. The structure of the novel ligand Hcintrz ( 9 ) is reported.