Spectral, structural and theoretical study of the effects of thiocyanato and dicyanamido ligands on the geometry of PbII complexes containing a triazinic ligand.

Abstract

Two lead(II) complexes of 5,6-bis(furan-2-yl)-3-(pyridin-2-yl)-1,2,4-triazine (DFPT), namely one-dimensional (1D) catena-poly[[bis[5,6-bis(furan-2-yl)-3-(pyridin-2-yl-κN)-1,2,4-triazine-κN2]lead(II)]-di-μ-thiocyanato-κ2N:S;κ2S:N], [Pb(NCS)2(C16H10N4O2)2]n, 1, and binuclear di-μ-dicyanamido-κ2N1:N5;κ2N5:N1-bis{[5,6-bis(furan-2-yl)-3-(pyridin-2-yl-κN)-1,2,4-triazine-κN2](nitrato-κ2O,O')lead(II)}, [Pb2(C2N3)2(NO3)2(C16H10N4O2)4], 2, as well as DFPT itself, were prepared and identified by elemental analysis, FT-IR, 1H NMR spectroscopy and single-crystal X-ray structural analyses. In the double-chain 1D coordination polymer of 1 and the binuclear structure of 2, the Pb atom has a hemidirected-PbN6S2 and a rare holodirected-PbN6O2 environment, respectively, with a distorted cubic geometry. All the coordination modes of dicyanamide ligands within lead complexes were studied using the Cambridge Structural Database (CSD) to compare them with the structures of 1 and 2. In addition to hydrogen bonds, the crystal networks are stabilized by π-π stacking interactions between the triazine, furyl and pyridine aromatic rings. The most stable theoretical structures of the title compounds predicted by density functional theory (DFT) calculations were compared with the solid-state results.