Rare earth complexes with 3,4-dimethylbenzoic acid and 5,5′-dimethyl-2,2′-bipyridineSynthesis, crystal structures and thermal behavior

The combination of 3,4-dimethylbenzoic acid (3,4-DMHBA) and 5,5′-dimethyl-2,2′-bipyridine (5,5′-DM-2,2′-bipy) with rare earth nitrate under the room-temperature conditions results in two novel complex formulated as [Ho(3,4-DMBA)3(5,5′-DM-2,2′-bipy)(H2O)] (1) and [La(3,4-DMBA)3(3,4-DMHBA)(5,5′-DM-2,2′-bipy)]2(2), respectively. The structures were confirmed by single-crystal X-ray diffraction. Two complexes are all characterized with elemental analysis and PXRD. Interestingly enough, because of the lanthanide contraction phenomena, the complex 1 is a mononuclear molecule with the coordination number of eight, but the complex 2 is a binuclear molecule with the coordination number of nine. The thermal decomposition mechanism for two complexes was discussed by TG-DTG technology. In addition, the three-dimensional infrared accumulation spectra of the evolved gas during the thermal decomposition for title complexes were investigated via the simultaneous TG/DSC-FTIR techniques. Beyond that, the heat capacities of complexes were measured by DSC. And the smoothed value of heat capacities and thermodynamic functions (HT-H298.15) and (ST-S298.15) were calculated according to the fitted polynomial and thermodynamic equations.