Synthesis, structures and optical properties of coordination compounds bearing N,N-dimethyl-4-(pyridin-4-yldiazenyl) aniline

Seven coordination compounds, [Zn(Dpya)SO4(H2O)3]n (1, 1D chain), [Cu(Dpya)SO4(H2O)3]n (2, 1D chain), [MoOS3(Dpya)2Cu3I]n (3, 1D chain), [Cu(Dpya)I]n (4, 1D chain), [Zn(Dpya)(NO3)2]n (5, dimer), [Cu(Dpya)(Ac)2]n (6, dimer), [Zn(Dpya)2Cl2]n (7, mononuclear) (Dpya=N,N-dimethyl-4-(pyridin-4-yldiazenyl) aniline) were synthesized and characterized by FTIR, elemental analysis and TG analysis. The structures of all these compounds were determined by single crystal X-ray diffraction, and structural analysis reveals that compounds 1–4 are 1D coordination polymers, compounds 5 and 6 are dimers with a similar structure and compound 7 is a mononuclear complex. The structural construction of these compounds is affected not only by the metal centers but also by the different counteranions. The photophysical properties of the ligand and the coordination compounds were also studied. For example, the third-order non-linear optical (NLO) properties of the ligand and its coordination compounds were measured by a 532nm laser using the Z-scan technique. The ligand Dpya and three coordination compounds (1, 2 and 4) show non-linear reversible saturated absorption (RSA) behavior. More interestingly, the ligand Dpya shows visible green luminescence (λex 520nm). The luminescent property was tuned by different metal ions and structures. It should be noted that compound 1 exhibits a strong orange-light emission assigned to a ligand–metal charge transfer (LMCT).