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)center dot 2H(2)O (A = BF4, ClO4, Br, NO3; Xtrz = triazole hands). 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)center dot 2H(2)O [A = BF4 (1), ClO4 (2), Br (3)1 and [Fe(Hcintrz)(3)](A)(2)center dot 1.5(H2O) [A = BF4 (4), ClO4 (5), Br (6)] revealed spin transitions over the range T-1/2 = 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)]center dot 2MeOH (7)} and a trinuclear {[Fe-3(Hsaltrz)(6)(H2O)(2)(EtOH)(4)](ClO4)(6)center dot 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.