A Series of CrIII Coordination Supramolecules: Synthesis, Structure and Study of Surface Electron Behaviors

Abstract

Three chromium(III) coordination supramolecules, [CrQ2(H2O)Cl]·H2O 1, [Cr(Pic)2(phen)]·NO3·2.5H2O 2, [Cr(ATA)(phen)]·CH3OH·3H2O 3 (HQ = Quinoline 2-acid, HPic = Picolinic 2-acid, H3ATA = Ammonia triacetic acid, phen = 1,10-Phenanthroline), have been synthesized solvothermally and characterized by single-crystal X-ray diffraction, IR spectra, UV-Vis absorption spectra and elemental analysis. The surface electron behavior of chromium complexes have been studied emphatically by surface photovoltage spectroscopy (SPS). Structural analyses indicate that the three complexes are all molecular complexes with the ligands of carboxylate groups; and, they are further connected into supramolecules by hydrogen bonds and π–π interactions. The results of SPS show that there are positive photovoltage response bands within 300–800 nm, which indicate that they all possess obvious photoelectric conversion properties. Energy-band theory for semiconductors and crystal field theory have been combined to analyze and assign the SPS bands. There are three types of band-to-band transitions in the SPS of the complexes; i.e., LMCT bands for Cl → Cr, O → Cr, N → Cr. The similarities and differences between the SPS and UV-Vis absorption spectra for the three complexes were compared and reasonably explained. There was a good correlation between the SPS and UV-Vis absorption spectra.