Frequency shifts and intensity changes in the raman spectra of liquid mixtures of TCNE with aromatic electron donors
01 Nov 1973-Chemical Physics Letters (North-Holland)-Vol. 23, Iss: 1, pp 5-8
TL;DR: The Ramaman spectra of liquid mixtures of TCNE with aromatic electron donors were studied in this article, where the electron transfer of up to 9% in the ground state of these complexes was observed.
Abstract: Raman spectra of liquid mixtures of TCNE with aromatic electron donors were studied. Red-shifts up to 20 cm-1 and changes in the intensity ratio of the CC and CN stretching modes of TCNE from 0.5 to 1.5–3.0 upon complexation were observed and related to an electron transfer of up to 9% in the ground state of these complexes. Some surprising shifts in donor lines are reported for complexes of TCNE with methoxy-substituted benzenes.
01 Apr 1994-Journal of Chemical Physics
TL;DR: In this article, the experimental electron transfer rates are compared with nonadiabatic and adiabatic electron transfer theories using a previously published analysis of all the vibrational modes active in the reaction.
Abstract: Ultrafast pump–probe measurements on the electron donor–acceptor complex of tetracyanoethylene with hexamethylbenzene in polar and nonpolar solvents are reported. Ground state coherence in the complex stretching mode at 165 cm−1 excited by impulsive stimulated Raman scattering is observed as well as decay of the ground state bleaching signal due to return electron transfer to the ground state. The experimental electron‐transfer rates are compared with nonadiabatic and adiabatic electron‐transfer theories using a previously published analysis of all the vibrational modes active in the reaction. It is shown that a breakdown of the Born–Oppenheimer approximation can give rise to a coupling that leads to the observed electron‐transfer reaction. The non‐Born–Oppenheimer matrix element is estimated using information obtained from the absorption and Raman spectra. Using this coupling, good agreement is found between the experimentally observed and theoretically predicted rates. Caveats of the various theories, the reliability of the normal mode analysis, and aspects of electron transfer that theory should address are discussed.
14 Mar 2007-Advances in Chemical Physics
TL;DR: The resonance Raman scattering spectra of the complexation between tetrathiafulvalene and cyclobis(paraquat-p-phenylene) and CBPQT(4+) have been used as the model system to characterize the binding event of a host-guest system, providing a basis to identify the structural and vibrational changes occurring upon complexation.
Abstract: The detection of analyte-binding events by receptors is drawing together the fields of Raman spectroscopy and supramolecular chemistry. This study is intended to facilitate this cohering by examining a model in the solution phase. The resonance Raman scattering (RRS) spectra of the complexation between tetrathiafulvalene (TTF) and cyclobis(paraquat-p-phenylene) (CBPQT(4+)) has been used as the model system to characterize the binding event of a host-guest system. RRS spectra are generated by excitation (lambda(exc) = 785 nm) within the lowest-energy charge-transfer (CT) transition (lambda(max) = 865 nm) of the TTF subsetCBPQT(4+) complex. The paired binding curves from the RRS and UV-vis-NIR titration data agrees with prior work, and a DeltaG of -5.7 +/- 0.6 kcal mol(-1) (MeCN, 298 K) was obtained for the complexation of TTF with CBPQT(4+). Computations on the complex and its components reproduce the energy shifts and resonance enhancements of the Raman band intensities, providing a basis to identify the structural and vibrational changes occurring upon complexation. The changes in bond lengths coincide with partial depopulation of a TTF-based HOMO and population of a CBPQT(4+)-based LUMO through CT mixing in the ground state of 0.46e(-). The structural changes upon complexation generally lead to lower wavenumber vibrations and to changes in the normal mode descriptions.
15 Aug 1976-Chemical Physics
TL;DR: In this article, the authors used laser Raman spectroscopy to study the molecular motions in the crystalline charge transfer complex durene:sym-trinitrobenzene.
Abstract: Molecular motions in the crystalline charge-transfer complex durene:sym-trinitrobenzene have been investigated using laser Raman spectroscopy. Isotopic substitutions of the donor and the acceptor are used to study relative amplitudes of various modes on the donor and the acceptor molecules. The low frequency motions comprised of phonons and intracharge-transfer modes appear to follow the giant molecule model with appreciable amplitude on both the donor and the acceptor molecules. The internal vibrations, on the other hand, can be characterized as totally a donor mode or an acceptor mode and show no observable exciton splittings. Splittings are found on the degenerate vibrations of the trinitrobenzene which suggest an appreciable distortion from D3h symmetry of this molecules in the complex.
01 May 1976-Chemical Physics Letters
TL;DR: In this paper, a resonance-enhanced 155−167 cm−1 Raman band was found in TCNE/EDA complexes in solution and was assigned to the totally symmetric νs vibration of uncomplexed TCNE, necessitating a reinterpretation of previously published data.
Abstract: A new resonance-enhanced 155–167 cm−1 Raman band has been found in TCNE/EDA complexes in solution. This band behaves similarly to the νCC and νCN bands in complexed TCNE. It is assigned to the totally symmetric νs vibration of uncomplexed TCNE, necessitating a reinterpretation of previously published data on TCNE.
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