Coordination polymers derived from a bis-pyridyl-bis-amide ligand: Supramolecular structural diversities and anion binding properties

Six new coordination polymers namely [{Cu(μ-L1)(CH3COO)2}]∝ 1a, [{Cu(μ-L1)2(CH3COO)2]∝ 1b, [{Cu(μ-L1)2(H2O)2}(NO3)2]∝ 2, [{Cu(μ-L1)2(H2O)2}(ClO4)2]∝ 3, [{Cu(μ-L1)(H2O)2(μ-SO4)}·3H2O]∝ 4a and [{Cu(μ-L1)2SO4}·X]∝ 4b (L1 = N,N′-bis-(3-pyridyl)terephthalamide) have been synthesized. Single crystal structures of five coordination polymers namely 1a, 2–4b and the free ligand L1 are discussed in the context of the effect of conformation dependent ligating topology of the ligands, hydrogen bonding backbone, counter anions on the resultant supramolecular structures observed in these coordination polymers. It was revealed from the single crystal X-ray structure analysis that conformation dependent ligating topology of the bis-amide ligand L1, counter anion’s ligating strength dependent metal: ligand ratio, hydrogen bonding ability of the ligand as well as counter anions are responsible for the formation of 1D zigzag, 1D looped chain, 2D corrugated sheet in 1a, 2–3, 4a−4b, respectively. By following in situ coordination polymer crystallization technique, anion binding and separation studies have also been performed; nitrate anion has been separated as neat coordination polymer crystals from a complex mixture of anions.