Rigidity Controlled Structures of Zn(II)-based Coordination Complexes: Synthesis and Photophysical Property Study

Abstract Crystal engineering has been a hot research area for over two decades, due to the potential applications for gas storage and energy conversion et al. In this work, we have demonstrated that the rigidity of the building ligand has played a decisive influence on the final structure of coordination complex. XXQ-1 ({[Zn3(μ2-OH)2(TIMB)(BDC)2]•0.25H2O}n) and XXQ-2 {[Zn2(IBIMB)(BDC)2(H2O)].5H2O}n (TIMB = 1,3,5-tris(imidazol-1-ylmethyl)benzene, IBIMB = 1-(1-imidazolyl)-3,5-bis(imidazole-1-ylmethyl)benzene, BDC = 1,4-benzenedicarboxylate) were successfully synthesized from the hydrothermal reaction. XXQ-1 owned 3D framework with a (3,7)-connected network, and XXQ-2 was a 4-fold interpenetrated 3D framework. The structural differences for XXQ-1 and XXQ-2 were ascribed to the distinct rigidity of imidazole containing ligands, where the TIMB and IBIMB owned three and two flexible imidazole arms, respectively. Photophysical property for XXQ-1 and XXQ-2 has been investigated, where the strong photoluminescence was originated from the intraligand charge transfer (ILCT). Both complexes owned semiconductor property with the band gap energy of 3.77 eV and 2.83 eV for XXQ-1 and XXQ-2, respectively. This work has provided a great example to adjust the structures of coordination complexes through the ligand modification.