Effects of length and number of aromatic rings in carboxylic acid ligands on structure and optical properties of lead(II) coordination polymers

Abstract

To systematically examine the effects of the length and number of aromatic rings in carboxylic acid ligands on the structure and properties of lead(II) coordination polymers, terephthalic acid (L1) and 4,4-biphenyl dicarboxylic acid (L2) as primary ligands and 1-(dimethylamino)propan-2-ol (L3) as ancillary ligand were used for preparation of two new lead(II) coordination polymers: [Pb2L21L3(DMF)]n (1) and [PbL2L3]n (2). Single-crystal X-ray diffraction analysis was used to determine the crystal structure of the prepared compounds. The results showed that the length of the π-conjugation system of the aromatic carboxylic acid ligands was a primary factor controlling the structure of the coordination compounds. Connecting Pb(II) atoms using ligands L1 and L3 led to formation of compound 1 with two-dimensional network structure, while use of ligands L3 and L2 resulted in formation of compound 2 with zigzag one-dimensional (1D) polymeric network structure. Study of the thermal behavior of the prepared compounds revealed that the structure and type of the ligands in the coordination compounds affected their thermal stability. Investigation of the optical properties of the compounds demonstrated that changing the length of the π-conjugation system of the aromatic carboxylic acid ligands in the structure of the coordination compounds can be used to tune their photophysical properties.