Solvothermal self assembly of three lanthanide(III)-succinates: Crystal structure, topological analysis and DFT calculations on water channel

Abstract

Three new coordination polymers have been assembled by self-assembly of lanthanide(III) ions and succinic acid in dimethylformamide–water (DMF-H2O) mixed solvent having formulae; {[Ln(suc)1.5(H2O)2]•xH2O}n; (1), (2) and (3) [Where Ln = La (1), Pr (2) and Nd (3), suc = succinate dianion; x = 2 for CP 1, x = 1 for CP 2 and x = 4 for CP 3]. In all three coordination polymers (CPs) 1-3, the Ln(III) centres are ten coordinated with bicapped square antiprismatic geometry (SAPRS-10). Crystallographic analysis reveals that CPs 1-3 crystallize in triclinic system P¯1 space group. The linker succinic acid displays two different bonding modes: (μ2-κ4, η2:η2) and (μ4-κ6, η1:η2:η2:η1). All CPs 1-3 are isostructural and isomorphous. The two Ln centres in CPs 1-3 are bridged together through succinate anions via (μ4-κ6, η1:η2:η2:η1) mode forming dinuclear (Ln2O18) Secondary building unit (SBU) which are extended infinitely to generate one-dimensional chains. These 1D chains are further extended along the b-axis to form two-dimensional layered structures via (μ2-κ4, η2:η2) mode and finally three-dimensional network. In case of Nd, the quality of the crystal allows to locate a major number of lattice water molecules (x = 4) than in the other two complexes and, remarkably, the formation of water channels can be realized and studied. It has been analyzed using DFT calculations combined with the molecular electrostatic potential (MEP) surfaces, the quantum theory of “atoms-in-molecules” QTAIM and non–covalent interaction index (NCIplot) analyses.