Humidity-Induced Structural Transformation in Pseudopolymorph Coordination Polymers

Three cadmium coordination polymers, namely, {[CdL(OAc)(2)](C2H5OH)}(n) (1), {[CdL(OAc)(2)](CH3CN)}(n) (2), and [CdL(OAc)(2)(H2O)](n) (3), were synthesized by an exoditopic 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene Schiff base ligand (L) and cadmium acetate in the presence of different solvent systems. Single-crystal X-ray diffraction, powder X-ray diffraction, and thermogravimetric analysis showed that 1D ladder pseudopolymorphic compounds (1 and 2) transformed to the solvent-free 1D linear compound 3 through a rare case of water absorption from air at room temperature. Interestingly, compound 3 was transformed to compound 1 through a dissolution-recrystallization structural transformation process. The results illustrated that solvents and humidity have an important role in the formation of pseudopolymorphs with the same or different structural motifs.

Automated summary

Three cadmium coordination polymers were synthesized using a Schiff base ligand and cadmium acetate in different solvent systems. The compounds underwent structural transformations under different conditions, with solvents and humidity playing important roles in the formation of pseudopolymorphs.