TY - JOUR
T1 - Excited state distortions in a charge transfer state of a donor-acceptor [2]rotaxane
AU - Stephenson, Rachel M.
AU - Wang, Xianghuai
AU - Coskun, Ali
AU - Stoddart, J. Fraser
AU - Zink, Jeffrey I.
PY - 2010/11/14
Y1 - 2010/11/14
N2 - The charge transfer excited state of a mechanically interlocked [2]rotaxane (R4+) with a donor 1,5-dioxynaphthalene (DNP) unit in the rod and the acceptor cyclobis(paraquat-p-phenylene) (CBPQT4+) ring component, along with the analogous non-interlocked [2]pseudorotaxane (P4+), is studied by resonance Raman spectroscopy and electronic absorption spectroscopy. Resonance Raman excitation profiles are obtained, calculated quantitatively using time-dependent theoretical methods, and interpreted with the assistance of DFT calculations. The active vibrational modes are consistent with an electron transfer from the HOMO centered on the DNP unit to the LUMO on the CBPQT 4+ ring. Displacement vectors of highly distorted modes agree with the bonding changes predicted from the MO nodal pattern. Subtle changes in the frequency of some modes in the free components compared with those in R 4+ are observed. The largest distortions are found for modes involving ring breathing in the DNP unit of the rod and the paraquat units of the CBPQT4+ ring. The individual mode contributions to the vibrational reorganization energy, as well as the total vibrational reorganization energy, are calculated. Very similar values of λv for R4+ and P4+ are calculated (∼2910 cm-1), indicating that the mechanical stoppers in the interlocked system do not significantly affect the excited state properties of R4+ compared with P4+.
AB - The charge transfer excited state of a mechanically interlocked [2]rotaxane (R4+) with a donor 1,5-dioxynaphthalene (DNP) unit in the rod and the acceptor cyclobis(paraquat-p-phenylene) (CBPQT4+) ring component, along with the analogous non-interlocked [2]pseudorotaxane (P4+), is studied by resonance Raman spectroscopy and electronic absorption spectroscopy. Resonance Raman excitation profiles are obtained, calculated quantitatively using time-dependent theoretical methods, and interpreted with the assistance of DFT calculations. The active vibrational modes are consistent with an electron transfer from the HOMO centered on the DNP unit to the LUMO on the CBPQT 4+ ring. Displacement vectors of highly distorted modes agree with the bonding changes predicted from the MO nodal pattern. Subtle changes in the frequency of some modes in the free components compared with those in R 4+ are observed. The largest distortions are found for modes involving ring breathing in the DNP unit of the rod and the paraquat units of the CBPQT4+ ring. The individual mode contributions to the vibrational reorganization energy, as well as the total vibrational reorganization energy, are calculated. Very similar values of λv for R4+ and P4+ are calculated (∼2910 cm-1), indicating that the mechanical stoppers in the interlocked system do not significantly affect the excited state properties of R4+ compared with P4+.
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U2 - 10.1039/c0cp00801j
DO - 10.1039/c0cp00801j
M3 - Article
C2 - 20871904
AN - SCOPUS:77958612772
SN - 1463-9076
VL - 12
SP - 14135
EP - 14143
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 42
ER -