TY - JOUR
T1 - Determination of binding strengths of a host-guest complex using resonance raman scattering
AU - Witlicki, E.H.
AU - Hansen, Stinne Wessel
AU - Christensen, M.
AU - Hansen, T.S.
AU - Nygaard, S.D.
AU - Jeppesen, J.O.
AU - Wong, E.W.
AU - Jensen, L.
AU - Flood, A.H.
PY - 2009/8/27
Y1 - 2009/8/27
N2 - 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 system in the solution phase. The resonance Raman scattering (RRS) spectra of the complexation between tetrathiafulvalene (TTF) and cyclobis(paraquat-p-phenylene) (CBPQT ) has been used as the model to characterize the binding event of a host-guest system. RRS spectra are generated by excitation (λ = 785 nm) within the lowest-energy charge-transfer (CT) transition (λ = 865 nm) of the TTFCCBPQT complex. The paired binding curves from the RRS and UV-vis-NIR titration data agrees with prior work, and a AG of -5.7 ± 0.6 kcal mol (MeCN, 298 K) was obtained for the complexation of TTF with CBPQT4+. 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 -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.
AB - 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 system in the solution phase. The resonance Raman scattering (RRS) spectra of the complexation between tetrathiafulvalene (TTF) and cyclobis(paraquat-p-phenylene) (CBPQT ) has been used as the model to characterize the binding event of a host-guest system. RRS spectra are generated by excitation (λ = 785 nm) within the lowest-energy charge-transfer (CT) transition (λ = 865 nm) of the TTFCCBPQT complex. The paired binding curves from the RRS and UV-vis-NIR titration data agrees with prior work, and a AG of -5.7 ± 0.6 kcal mol (MeCN, 298 K) was obtained for the complexation of TTF with CBPQT4+. 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 -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.
UR - http://www.scopus.com/inward/record.url?scp=68949199499&partnerID=8YFLogxK
U2 - 10.1021/jp905202x
DO - 10.1021/jp905202x
M3 - Journal article
C2 - 19645430
AN - SCOPUS:68949199499
VL - 113
SP - 9450
EP - 9457
JO - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
JF - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
SN - 1089-5639
IS - 34
ER -