Binuclear and polymeric Zn(II) and Cd(II) coordination compounds with chromophore N-((pyridin-4-yl)methylene)benzene-1,4-diamine obtained in situ: Preparation, structural and spectroscopic study

Four coordination compounds, that include the discrete binuclear complex [Zn(H2O)4(bda4Py)]2(SO4)2 (1), two isomorphous one-dimensional coordination polymers, {[Zn(NO3)2(bda4Py)2]·2H2O}n (2) and {[Cd(NO3)2(bda4Py)2]·2H2O}n (3), and one two-dimensional coordination polymer {[Cd(bda4Py)2(dpa)2]·2H2O}n (4) [where bda4Py = N-((pyridin-4-yl)methylene)benzene-1,4-diamine, H2dpa = diphenic acid, as a potential anionic competitor ligand having two carboxylic groups] were obtained as the products of partial hydrolysis of the ligand N1,N4-bis(pyridin-4-ylmethylene)-benzene-1,4-diamine (bda4bPy) in the reaction conditions. Single crystal X-ray data reveal that N-((pyridin-4-yl)methylene)benzene-1,4-diamine acts as a bidentate linker between two metal centers through nitrogen atoms of pyridino- and amino-groups. The additional stabilization of the crystalline solids 1–4 is provided via hydrogen bonds. N-((pyridin-4-yl)methylene)benzene-1,4-diamine (bda4Py) was also obtained by direct synthesis, and two ligands (bda4bPy and bda4Py) were characterized in the solid state and in solution by spectroscopic (FTIR, UV–vis, NMR) methods. Luminescence studies for the reported compounds are also documented.