Hydrogen bonded supramolecular architecture of a copper(II)-citrate coordination building block: Synthesis and crystal structure with theoretical insight

Abstract

A tricarboxylate supported binuclear metal organic hybrids of Cu(II), [Cu₂(µ-cit)(phen)₄]·9H₂O (1) has been synthesized using well known pyridyl based N,N′ linker, 1,10-phenanthroline and has been structurally characterized. The use of the flexible hydroxyl tricarboxylate, citrate, in designing such framework has created a marked diversity in the topology. The structural and topological diversity has been analyzed from the single crystal X-ray structure. Here, in an unit, each of the two Cu(II) centres are chelated by two phenanthrolineligands and citrate (cit^4-) serves the role of a bridging ligand. Furthermore, the carboxylate moiety/hydroxyl oxygen sites of citrate and the aromatic chelating ligands promote the supramolecular recognition through hydrogen bonding and other non-covalent interactions (like π-π interaction) and thereby results in higher dimensional architecture.Along with this, there are water molecules as water of crystallization. The oxygen atoms of the carboxylate moiety involve in both inter and intra-molecular hydrogen bonding with the hydrogen atoms of the water molecules resulting in a hydrogen bonded helical supramolecular solid. Theoretical study is performed to analyze the structure and the role of non-covalent interactions through DFT based calculations and Hirshfeld surface analysis.