Spin Crossover in Polymeric Materials Using Schiff Base Functionalized Triazole Ligands



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)2·2H2O (A = BF4, ClO4, Br, NO3; 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)2·2H2O [A = BF4 (1), ClO4 (2), Br (3)] and [Fe(Hcintrz)3](A)2·1.5(H2O) [A = BF4 (4), ClO4 (5), Br (6)] revealed spin transitions over the range Tequation image = 100–225 K. The spin crossover properties of the dehydrated materials were also investigated [16(dh)]. In attempts to prepare single crystals of these materials a dinuclear {[Fe2(Hsaltrz)5(NCS)4]·2MeOH (7)} and a trinuclear {[Fe3(Hsaltrz)6(H2O)2(EtOH)4](ClO4)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.