Copper() halide cluster-based coordination polymers modulated by chiral ditopic dithiodianthranilide ligands: synthesis, crystal structure and photoluminescence

Reaction of copper( i ) halides with chiral dithiodianthranilides mdta and bdta afforded polymeric complexes where polynuclear CuX clusters were linked together by ditopic bridging ligands into 1D chains or 2D layer structures. In the case of racemic ligands double stranded chain polymers were formed where the Cu 4 X 4 (X = I or Br) cores are connected by enantiomeric pairs of the ditopic ligands. In contrast, a homochiral mdta ligand created a single stranded hybrid chain involving single mdta enantiomers and solvated Cu 5 I 5 clusters or 2D square (4,4) nets composed of rings comprising four Cu 3 X 3 clusters in nodes and four homochiral ligand molecules in sides with solvent MeCN molecules between the grid layers. The hybrid layer structure obtained from CuCl and the racemic mdta ligand crystallized as a conglomerate that led to its self-resolution into enantiomeric chiral crystals. The solid state CD spectra revealed contribution of two electronic transitions to the diffuse lowest energy absorption band of the complexes. In addition the observed long wavelength Cotton effect sign reflected the helicity of the thiobenzamide chromophore in the ligand unit. At room temperature the solid complexes exhibited weak red phosphorescence near 600-620 nm. Upon cooling down to 10 K all investigated complexes are phosphorescent with average lifetimes of 17-84 μs. The influence of ligand chirality on the self-assembly and spectroscopic properties of copper( i ) halide coordination polymers was investigated.