Synthesis, structure, and ligand exchange of a copper(II)-based molecular helix with 2,6-pyridinedicarboxylates

Abstract

An one-dimensional (1-D) metal–organic polymer, [Cu₂(PDA)₂(DMF)₂]_n (PDA = 2,6-pyridinedicarboxylate, DMF = dimethylformamide), was synthesized by reaction of copper(II) nitrate hemi(pentahydrate) and 2,6-pyridinedicarboxylic acid in DMF. The complex shows a molecular helix structure consisting of five-coordinate Cu(II) building blocks with distorted square pyramidal geometry. Tridentate chelating PDA, DMF, and an oxygen from the carboxylate of the adjacent Cu(II) building unit are coordinated to the copper(II) center. The weakly coordinated DMF groups in [Cu₂(PDA)₂(DMF)₂]_n easily exchange with a pyridine to generate a pyridine-coordinated non-helical 1-D metal–organic polymer with six-coordinate pseudooctahedral Cu(II) units.

Keywords:

• Metal–organic polymer
• 2,6-Pyridinedicarboxylate
• Molecular helix
• Ligand exchange

Acknowledgements

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education [NRF-2013R1A1A2057675]; Hallym University Research Fund, 2014 [HRF-201401-010].