Solvothermal synthesis and multifunctional characterization of a two-dimensional Mn(II) coordination polymer with dibromoterephthalate linkers: Dielectric, BET, and hirshfeld surface studies

Abstract

A new two-dimensional Mn(II)-based coordination polymer, poly[(μ 2 -2,5-dibromobenzene-1,4-dicarboxylato-κ 2 O:O′)bis(μ 2 -formato-κ 2 O:O′)bis(N,N-dimethylformamide-κO)dimanganese(II)] ([Mn 2 (Br 2 BDC)(Fo) 2 (DMF) 2 ] n ), was synthesized solvothermally at 150 °C for 24 h and obtained in approximately 75% yield. Single-crystal X-ray diffraction revealed a trigonal centrosymmetric structure with space group P-3, in which Mn(II) adopts a slightly distorted MnO 6 octahedral coordination environment, and Br 2 BDC/formate bridges generate an extended two-dimensional framework. Hirshfeld surface analysis showed that H···H (24.8%), H···O/O···H (20.6%), Br···H/H···Br (13.0%), and Mn···O/O···Mn (9.8%) contacts make major contributions to crystal packing. Thermal analysis revealed three main decomposition stages with weight losses of 20.8%, 19.2%, and 14.1%, while nitrogen adsorption–desorption measurements indicated Type IV mesoporous behaviour with a Brunauer–Emmett–Teller (BET) surface area of 68.22 m 2 g –1 and an average pore radius of 29.19 Å. Dielectric measurements demonstrated frequency- and temperature-dependent polarization with reduced dielectric loss at higher frequencies. A.C. conductivity measurements showed frequency-dependent hopping transport, reaching approximately 1.0 × 10 –4 S m –1 in the high-frequency region at 40 °C. Complementary ESP, NCI–RDG, ELF, LOL, and IRI analyses further provided insights into the electrostatic distribution, non-covalent interactions, and electron localization within the coordination framework. The combined structural and physicochemical characteristics highlight [Mn 2 (Br 2 BDC)(Fo) 2 (DMF) 2 ] n as a promising multifunctional coordination material for potential dielectric, insulating, and adsorption-related applications.