title: Preparation, optical and electrochemical properties, and molecular orbital calculations of tetraazaporphyrinato ruthenium (II) bis(4-methylpyridine) fused with one to four diphenylthiophene units.
abstract: 2,5-Diphenyl-3,4-dicyanothiophene (1) and phthalonitrile (2) were mixed and treated with ruthenium (III) trichloride, 4-methylpyridine, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in 2-ethoxyethanol at 135°C, to produce low-symmetrical tetraazaporphyrins (TAPs) (3), (4), (5), and (6) with one to three thiophene rings. Two thiophene-annelated tetraazaporphyrins were isolated as opposite and adjacent isomers 4 and 5. The structure of 3 was determined by X-ray crystallography, showing that the thiophene ring linked at the 3,4-positions on the tetraazaporphyrin scaffold deviates from the mean plane of the four central pyrrole nitrogen atoms (N1-N3-N5-N7). Optical and electrochemical properties of the products were examined by UV-vis and magnetic circular dichroism (MCD) spectroscopy, together with cyclic voltammetry. In the (1)H NMR spectra, the signals of 4-methylpyridine coordinating to the central ruthenium atom appeared at a higher magnetic field than those of uncoordinated 4-methylpyridine itself due to the shielding effect of the TAP ring. Increasing the number of fused thiophene rings resulted in 1) lower magnetic field shifts of the signals of axially coordinated 4-methylpyridine in the (1)H NMR spectra, 2) lower energy shifts of the Q band absorption in the UV-vis spectra, and 3) decreasing (cathodic shift) of the first oxidation potentials. The structures of simplified model compounds were optimized using the DFT method with the Gaussian 09 program at the B3LYP/LANL2DZ level for the Ru atom and the B3LYP/6-31G (d, p) level for the C, H, N, and S atoms. The optimized structures were utilized to calculate the NMR shielding constants, the HOMO and LUMO orbital energies, and the electronic absorption spectra.
authors.affiliation: Center for Instrumental Analysis, Iwate University, Morioka 020-8551, Japan. Electronic address: kimura@iwate-u.ac.jp.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kimura
authors.affiliation: Center for Instrumental Analysis, Iwate University, Morioka 020-8551, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Murakami
authors.affiliation: Department of Chemistry and Bioengineering, Faculty of Engineering, Iwate University, Morioka 020-8551, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Suzuki
authors.affiliation: Department of Chemistry, Graduated School of Science, Tohoku University, Sendai 980-8578, Japan.
authors.forename: Taniyuki
authors.initials: T
authors.lastname: Furuyama
authors.affiliation: Department of Applied Chemistry, Kinki University, Higashi-Osaka 577-8502, Japan.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Nakahodo
authors.affiliation: Department of Applied Chemistry, Kinki University, Higashi-Osaka 577-8502, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Fujihara
authors.affiliation: Department of Chemistry, Graduated School of Science, Tohoku University, Sendai 980-8578, Japan. Electronic address: nagaok@m.tohoku.ac.jp.
authors.forename: Nagao
authors.initials: N
authors.lastname: Kobayashi
mesh_terms: D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010847:Picolines / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D017975:Ruthenium Compounds / Q000737:chemistry*; D013876:Thiophenes / Q000737:chemistry
chemical_list: D010847:Picolines; D017975:Ruthenium Compounds; D013876:Thiophenes; C051763:thiophene A; D012428:Ruthenium; C515325:4-methylpyridine
keywords: Electrochemistry; Magnetic circular dichroism; Molecular orbital calculations; Phthalocyanine; Ruthenium; Thiophene