Solvent and additive-controlled supramolecular isomerism in zinc coordination polymers

Abstract

A new series of Zn(II) supramolecular isomers containing ditopic 1,3-di(pyridin-4-yl)urea (4bpu) ligand were synthesized and characterized by infrared analysis, elemental analysis and TGA as well as single-crystal X-ray diffraction analysis. Four solvent-induced pseudopolymorphic zinc (II) coordination polymers (CPs), namely, {[Zn(4bpu)(OAc)2](CH3OH)}n (1), {[Zn(4bpu)(OAc)2](C2H5OH)}n (2), {[Zn(4bpu)(OAc)2](HOCH2CH2OH)}n (3), and {[Zn(4bpu)(OAc)2](0.5H2O)}n (4), were prepared by the reaction of Zn(OAc)2.2H2O and 4bpu via self-assembly under varying solvent systems. Also, a pair of polymorphic coordination polymers namely, {[Zn(4bpu)(OAc)2](CH3OH)}n (1α) and {[Zn3(4bpu)3(OAc)6](CH3OH)2}n(1β), was prepared in the presence of different organic additives. Single-crystal X-ray diffraction confirmed that 1−4 and 1α display 1D polymeric zig-zag chains and 1β exhibits 1D triple-stranded ladders that were self-assembled through various supramolecular interactions. In addition, a series of dissolution-recrystallization structural transformations (DRST) were performed on these supramolecular isomers.