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Electronic Structure and Absorption Spectra of Biferrocenyl and Bisfulvalenide Diiron Radical Cations: Detection and Assignment of New Low‐Energy Transitions
Author(s) -
Warratz Ralf,
Aboulfadl Hanane,
Bally Thomas,
Tuczek Felix
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200801054
Subject(s) - delocalized electron , chemistry , absorption spectroscopy , molecular orbital , triiodide , electronic structure , absorption (acoustics) , atomic electron transition , atomic orbital , molecular electronic transition , matrix isolation , spectral line , spectroscopy , ground state , infrared spectroscopy , atomic physics , crystallography , electron , computational chemistry , materials science , molecule , physics , electrolyte , organic chemistry , electrode , quantum mechanics , astronomy , dye sensitized solar cell , composite material
New transitions : Low‐energy electronic transitions have been detected spectroscopically in the Fe II –Fe III mixed‐valent biferrocenyl radical cation, but are absent in the spectra of the neutral analogue. They have been assigned by time‐dependent DFT calculations (squares in figure). Analogous investigations were performed for the bisfulvalenide Fe II –Fe III radical cation.UV‐visible/near‐IR (NIR)/mid‐IR (MIR) solution, solid‐state, and matrix‐isolation electronic absorption spectra of the Fe II –Fe III mixed‐valent homobimetallic compounds biferrocenyl triiodide ( 1 ) and 1′,1′′′‐diethylbiferrocenyltriiodide ( 2 ) reveal the presence of a low‐energy transition in the MIR region that has not been reported before. The new absorption feature and the known NIR band are both assigned to intervalence charge‐transfer (IVCT) transitions. To obtain insight into the electronic structures of 1 and 2 , DFT calculations with the BP86 functionals and different basis sets have been performed. Based on the molecular orbital scheme of cation 1 , one band corresponds to the transition between the highest occupied d x 2 − y 2orbitals on the two iron centers, whereas the other one is assigned to a transition from a lower‐lying d z 2orbital to the d x 2 − y 2orbital. For comparison, the doubly bridged bisfulvalenide diiron cation ( 3 ) has been investigated by optical absorption spectroscopy and DFT calculations. The experimental and theoretical results are discussed with respect to the degree of electron localization/delocalization in these systems.