Preparation, Crystal Structure and Enthalpy Change of Formation of the Reaction in Liquid Phase of a New Three‐Dimensional Mixed‐Ligand Holmium(III) Coordination Polymer Based on Strong π‐π Stacking Interactions

Abstract

AbstractA new three‐dimensional coordination polymer, [Ho(5‐nip)(phen)(NO3)(DMF)] (5‐nip=5‐nitroisophthalic acid and phen=1,10‐phenanthroline), was prepared and characterized by single crystal X‐ray diffraction, elemental analysis, IR spectrum and DTG‐DSC techniques. The results show that the title complex crystallizes in space group P2/m with a=1.0906(3) nm, b=1.2804 (3) nm, c=1.6987(4) nm, β=91.400(5)°, Z=4, Dc1.931 Mg/m3, F(000)= 1352. Each Ho(III) ion is nine‐coordinated by one chelating bidentate and two monodentate bridging carboxylate groups, one chelating bidentate NO−3 anion, one DMF molecule and one 1,10‐phenanthroline molecule. The complex is constructed with one‐dimensional ribbons featuring dinuclear units and the one‐dimensional ribbons are further assembled into two‐dimensional networks by strong π‐π stacking interactions with the distance of 0.327 nm, then the networks are arranged into three‐dimensional structure according to ABAB fashion. The complex exhibits high stability up to 600 °C. Its enthalpy change of formation of the reaction in liquid‐phase in solvent DMF was measured using an RD496‐III type microcalorimeter with a value of (−11.016±0.184) kJ·mol−1.