Syntheses, structures and properties of cadmium(II) halide complexes containing tridentate Schiff bases

Three neutral mononuclear complexes of the type [Cd(L1)I-2] (1) [L1 = (N,N-diethyl,N'-(pyridin-2-yl)formylidene)ethane-1,2-diamine] and [Cd(L2)X-2] [L2 = (N,N-diethyl,N'-(pyridin-2-yl)benzylidene)ethane-1,2-diamine; X = Br- (2), I- (3)] are isolated using one-pot reactions of cadmium(II) halides and tridentate Schiff bases (L1 and L2) in a 1:1 molar ratio in MeOH. solutions at room temperature. The compounds are characterized by elemental analyses and spectroscopic and other physicochemical data. Single-crystal X-ray diffraction analyses of (1)-(3) show that cadmium(II) center in each complex adopts a distorted square pyramidal geometry bound by three N atoms of L1/L2 and two terminal halides. Intermolecular pi center dot center dot center dot pi interactions in (1), cooperative C-H center dot center dot center dot Br hydrogen bonds and C-H center dot center dot center dot pi interactions in (2) and C-H center dot center dot center dot pi interactions in (3) lead to different crystalline architectures. Thermogravimetric analyses show that the compounds have reasonable thermal stabilities. The complexes display ligand-centered pi-pi* fluorescence in DMF solutions at room temperature.