Crystal engineering studies of a series of pyridine-3,5-dicarboxamide ligands possessing alkyl ester arms, and their coordination chemistry

Abstract

Five pyridine-3,5-dicarboxamide, 3,5-pda, ligands were synthesised and characterised. All of these ligands possess pendant arms with terminal carboxylic esters. The crystal structures of several of these ligands were obtained, these demonstrating various degrees of supramolecular interactions depending on the structural nature of the pendant arms. Discrete complexes and coordination networks from these ligands with d-block metal ions were also investigated; with manganese(II) and cadmium(II) four new coordination polymer species were obtained, while reactions with cobalt(II) and platinum(II) gave a non-crystalline polymer and a discrete complex, respectively. X-ray powder diffraction was used to determine the phase purity, while the morphological properties of some of these ligands and metal complexes were also probed using AFM and SEM imaging and physical properties were investigated using techniques such as EDX and DSC. The results herein demonstrate that these 3,5-pda ligands and their transition metal complexes possess structural properties analogous to popular aryl carboxamide building blocks that can be harnessed in crystal engineering and supramolecular chemistry.