12212-68-9Relevant articles and documents
Gas-phase electronic absorption spectroscopy of substituted bis(η6-benzene)chromium derivatives: Rydberg transitions in bis(η6-anisole)chromium and bis(η6-2,6- dimethylpyridine)chromium
Ketkov,Domrachev,Ob'edkov,Vasil'kov,Yur'eva,Mehnert
, p. 1932 - 1937 (2004)
Gas-phase electronic absorption spectra of chromium bisarene complexes with oxygen- and nitrogen-containing ligands, (η6-PhOMe) 2Cr (1) and (η6-2,6-Me2C5H 3N)2Cr (2), were first measured. Rydberg bands disappearing on going to the condensed-phase spectra were revealed. The first ionization potentials of complexes 1 and 2 (5.30 and 5.40 eV, respectively) were determined from the Rydberg frequencies. The Rydberg transitions were assigned and the corresponding Rydberg term values and quantum defects were determined. The effect of heteroatoms on the Rydberg structure parameters was revealed by comparing the spectra of complexes 1 and 2 with those of unsubstituted analogs. The appearance, in the ligand side chain, of an oxygen atom capable of being involved in conjugation with the π-electron system of the aromatic ring results in substantial broadening of the observed Rydberg bands. This can be associated with an increased ligand contribution to the HOMO of the sandwich compound. The influence of the oxygen atom on the ionization energy of the molecule is insignificant. In contrast to this, introduction of a nitrogen atom into the carbocycle leads to a noticeable increase in the ionization potential of the molecule, while the ligand contribution to the HOMO of the complex remains practically unchanged.
The electronic absorption spectra of the alkyl-substituted derivatives of bis(benzene)chromium(0) in the vapour phase
Domrachev, G. A.,Ketkov, S. Yu.,Razuvaev, G. A.
, p. 341 - 348 (2007/10/02)
The UV and visible absorption spectra of (arene)2chromium(0) (arene=benzene (I), toluene (II), ethylbenzene (III), cumene (IV), tert-butylbenzene (V), mesitylene (VI)) in the vapour phase have been invesigated.Four band systems A, B, C and D are revealed in the spectra.The bands of the system with the shortest wavelengths, D, represent the Rydberg series.The first ionisation potentials IPa1g of I-VI determined from the Rydberg band frequencies are 5.45, 5.29, 5.25, 5.21, 5.18 and 5.01 eV respectively.The Rydberg bands correspond to the allowed electrodipole transitions from the highest occupied moloecular orbital (MO) a1g to the vacant MO of either the a2u or e1u type.System C corresponds to the intense band of the solution spectra.The electronic transition e2g -> e*2u obviously makes a great contribution to this system.System B is assigned to the transition from a1g to vacant a2u or e1u MO, which can be Rydberg orbitals.System A can be assigned to the a1g -> e*2u transition or to the Rydberg transition, which is forbidden in the D6h point group but becomes allowed upon reduction of symmetry.
