Electronic Structures of Bis- and Monothiophene Complexes with Fe, Co, Ni: A Density Functional Theory Study
文摘
A density functional theory study for the bis- and monothiohene complexes of Fe, Co, and Ni (MT2 and MT, T = thiophene, M = Fe, Co, Ni) was performed to understand their coordination geometries, bonding properties, vibration spectra and singlet excited state spectra. The typical metal coordination exists in the complexes. The Fe−thiophene coordination has the highest stability, with Ni−thiophene being the second highest, and Co−thiophene the lowest. Bisthiophene complexes of Co and Ni prefer to homolytically dissociate to their monothiophene ones and free thiophene. Frequency calculation shows that the ligand−M−ligand asymmetric stretching vibration in bisthiophene complexes shows a strong absorption, at 435.2, 495.7, and 383 cm−1 for Fe(η4-T)2, Co(η2-T)2 and Ni(η2-T)2, respectively. The M−S stretching vibration in monothiophene complexes shows a strong absorption in the far-infrared region, at 209, 156, and 150 cm−1 for Fe(η4-T), Co(η4-T) and Ni(η5-T), respectively. The excited state spectra indicate that the characteristic absorption wavelengths of the complexes have a red shift of more than 12.40 eV compared to free thiophene, at 3.54, 1.64, 3.83, 2.75, 1.43, and 2.58 eV for Fe(η4-T)2, Co(η2-T)2, Ni(η2-T)2, Fe(η4-T), Co(η4-T), and Ni(η5-T), respectively.