Synthesis, structure and luminescence behaviour of heptacoordinated one-dimensional coordination polymers of the type [Cd(L)(dca)]n(X)n (L = a pentadentate Schiff base; dca = dicyanamide; X = ClO4-, PF6-)

Two heptacoordinated one-dimensional coordination polymers of the type [Cd(L)(dca)]n(X)n (1 and 2) [L = N,N′-(bis-(pyridin-2-yl)benzylidene)diethylenetriamine; dca = dicyanamide; X = ClO4- (1), PF6- (2)] have been prepared and characterized on the basis of microanalytical, spectroscopic and other physicochemical properties. Structures of 1 and 2 are solved by single crystal X-ray diffraction measurements. Structural study reveals that in both compounds each cadmium(II) center adopts a distorted pentagonal bipyramidal geometry with a CdN7 chromophore coordinated by five N atoms of the pentadentate Schiff base and two nitrile N atoms of single bridged dca in μ1,5 fashion. The polynuclear units in 1 are engaged in weak N–H…O and C–H…O hydrogen bondings with perchlorate ions embedded among the chains to give a 2D sheet structure. In the long-range form, the 1D polymeric chains of 2 pack through N–H…F and C–H…F hydrogen bonds with hexafluorophosphate placed in between chains resulting a 2D continuum. The complexes display intraligand 1(π–π∗) fluorescence in DMF solutions at room temperature.