Syntheses, molecular and crystalline architectures, and luminescence behaviours of two dinuclear cadmium(II) compounds containing a tetradentate N-donor di-Schiff base

Abstract

Two dinuclear cadmium(II) compounds of the types [Cd(L)(μ-Cl)] 2(PF 6) 2 ( 1) and [Cd(L)(μ 1,5-dca)] 2(ClO 4) 2.0.66MeOH ( 2) [L = N,N′-(bis(pyridin-2-yl)benzylidene)-1,3-propanediamine; dca = dicyanamide] have been synthesized and characterized on the basis of microanalytical, spectroscopic and other physicochemical results. X-ray structural studies show that in 1 and 2 each hexacoordinated cadmium(II) adopts a distorted octahedral geometry with CdN 4Cl 2 ( 1)/CdN 6 ( 2) chromophore ligated through four N atoms of L along with two chlorides in 1 forming a four-membered Cd–(Cl) 2–Cd rhombohedral bridging loop and two nitrile N atoms of two μ 1,5 dicyanamides in 2 affording a larger 12-membered Cd–(NCNCN) 2–Cd ring with boat conformation. In the crystalline state, individual units in 1 are packed through multiple weak C H⋯F hydrogen bonds and C H⋯ π and π ⋯ π interactions affording a 2D sheet structure. The dinuclear units in 2 are engaged in weak intermolecular C H⋯O and C H⋯N hydrogen bondings to give a 2D continuum, which is further stabilized by π⋯ π interactions through pyridine rings of L. In DMF solutions, 1 and 2 show high-energy intraligand 1( π– π *) fluorescence at room temperature.