[A purple-emitting luminescence complex [Cd(bpdc)(phen)2(H2O)] . 6H2O: synthesis, structure and spectral properties]

A supramolecular Cd(II) complex[Cd(bpdc) (phen)2 (H2O)] . 6H20 (1) was synthesized with 2, 4'-biphenyldicarboxylic acid (H2bpdc) and 1, 10-phenanthroline (phen) under hydrothermal conditions and characterized by single-crystal X-ray diffraction elemental analysis, and IR spectrum. Single-crystal X-ray analysis reveals complex 1 crystalizes in the triclinic P 1 space group, the metal center Cd(II) ion is six-coordinated and exhibits a distorted octahedron geometry arrangement. 3D supramolecular structure could be formed taking into account two kinds of hydrogen bonds and π--π interactions. At the same time, we discussed the luminescent properties of complex 1 in the solid-state as well as in the solvents at different temperatures. When excited at 350 nm, in the solid state at 298 K, 1 has purple luminescence with emission band at 390 nm; in the solid state at 77 K, 1 displays two emission bands at 380 and 520 nm. Because the vibration structure is more defined at low temperature, at 298 K, 1 also has purple luminescence in DMSO and CH3OH solutions with emission bands at 380 and 375 nm, which are blue-shifted compared with solid-state maximum emission band. These all can be attribute to the π*-->π transition based on the coordinate ligands. The fluorescence decay curves of complex 1 indicate that the processes of decay consist of two components. At 298 K, the lifetime of 1 is longer in DMSO solution (τ1 =1. 73 µs and τ2 =14. 07 µs) than that in CH3OH solution (τ1 =1. 21 µs and τ2 = 12. 44 µs). Moreover, the-lifetime of 1 is longer at 77 K (τ1 =1. 96 µs and τ2= 16. 11 µs) than that at 298 K in the solid state (τ1= 1. 20 µs and τ2 =11. 34 µs). The results might be caused by the increase in radiative rate and decrease in non-radiative rate at low temperature.