Lanthanide Luminescent Coordination Polymer Constructed from Unsymmetrical Dinuclear Building Blocks Based on 4-((1H-Benzo[d]imidazol-1-yl)methyl)benzoic Acid

Lanthanide coordination polymers of the general formula [Ln 2 (L) 5 (NO 3 )(H 2 O) 4 ] n (Ln = Eu ( 1 ), Tb ( 2 ), Gd ( 3 )) supported by a novel aromatic carboxylate ligand 4-((1H-benzo[d]imidazol-1-yl)methyl)benzoic acid (HL) have been synthesized, characterized, and their photoluminescence behavior is examined. The powder X-ray diffraction patterns of complexes 1 − 3 showed that 1 − 3 are isostructural; thus, 1 has been chosen as an example to discuss in detail about the molecular structure by single-crystal X-ray diffraction. Complex 1 is a one-dimensional (1D) helical chain-like coordination polymer consisting of unique unsymmetrical dinuclear lanthanide building blocks. The 1D chains are further linked by the significant intermolecular hydrogen-bonding interactions to form a two-dimensional supramolecular network. The Tb 3+ complex exhibits bright green luminescence efficiency in the solid state with a quantum yield of 15%. On the other hand, poor luminescence efficiency has been noted for Eu 3+ -benzoate complex.