Synthesis and characterization of a novel kind soluble, conjugated, and fluorescent chelate polymer containing fluorene ring in the backbone: Optical, electrical, and electrochemical properties

A novel highly soluble coordination polymer, poly(3,4-HBA-Cr-FDA), containing Cr(III) ion in the backbone was synthesized. Monomeric model compounds (MC-1 and MC-2) were also synthesized as the comparison materials. The structures were characterized by FT-IR, UV–vis, 1H and 13C NMR, and size exclusion chromatography (SEC). SEC results showed that the novel polymer had 65–68 repeated units. ICP-AES was used to determine the chromium content of MC-2. Thermal data were obtained by TGA and DSC techniques showing that MC-2 and the novel polymer had high rate of hydrate water. Cyclic voltammetry (CV) measurements were carried out and the HOMO–LUMO energy levels and electrochemical band gaps ( E ′ g ) were calculated. Additionally, the optical band gaps (Eg) were determined using UV–vis spectra of the materials. Electrical conductivity measurements of the doped (with iodine) and undoped polymer related to temperature and doping time were carried out by four point probe technique using a Keithley 2400 electrometer. Measurements were made using the polymeric film deposited on ITO glass plate by dip-coating method. Also, absorption spectra of doped polymeric film were recorded by a single beam spectrophotometer showing that doping procedure causes peak growing in absorption spectra. Ability of processing of poly(3,4-HBA-Cr-FDA) in gas sensors was discussed. Fluorescence spectra of the polymer in a series of solvents were obtained and it was found that poly(3,4-HBA-Cr-FDA) had green–red emitting emission in different solvents.