2D/3D spin crossover porous coordination polymers based on isomeric tetrapyridyl benzene ligands

By employing cyanoborohydride and isomeric tetrapyridyl benzene ligands, a new three-dimensional (3D) [Fe(3-tpb)(NCBH3)(2)] (1 center dot 2H(2)O, 3-tpb = 1,2,4,5-tetra(pyridin-3-yl)benzene) and a two-dimensional (2D) [Fe(4-tpb)(NCBH3)(2)] (2.2-NapSMe and 2 center dot H2O center dot 3DMF, 4-tpb = 1,2,4,5-tetra(pyridin-4-yl)benzene, 2-NapSMe = 2-(methylthio)naphthalene) porous coordination polymer (PCP) were synthesized, and exhibited the diamond (dia) and square lattice (sql) topologies, respectively. Complex 1 center dot 2H(2)O shows gradual and incomplete spin crossover (SCO) behavior because of the rigid framework and larger octahedral distortion. In contrast, abrupt SCO and hysteretic two-step SCO behaviors are observed in 2.2-NapSMe and 2 center dot H2O center dot 3DMF, respectively. This work proves that the modulation of host-guest interactions significantly influences the transition temperatures and SCO characteristics in a flexible PCP. More importantly, diverse multidentate ligands can be used to construct PCPs with novel topologies and tunable SCO properties.

Automated summary

By using different ligands, porous coordination polymers with different topologies can be synthesized, and their spin crossover properties can be tuned by modulating the host-guest interactions.