Excited state distortions in a charge transfer state of a donor-acceptor [2]rotaxane.

The charge transfer excited state of a mechanically interlocked [2]rotaxane (R(4+)) with a donor 1,5-dioxynaphthalene (DNP) unit in the rod and the acceptor cyclobis(paraquat-p-phenylene) (CBPQT(4+)) ring component, along with the analogous non-interlocked [2]pseudorotaxane (P(4+)), 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.

Solvent effects on the coexistence of localized and delocalized 4,4'-dinitrotolane radical anion by resonance Raman spectroscopy.

The resonance Raman spectrum of the simple alkyne bridge in 4,4'-dinitrotolane radical anion shows two distinct bands, providing proof of the solvent-dependent coexistence of charge-localized and -delocalized species. The Raman spectra of normal modes primarily involving the charge-bearing -PhNO(2) units also support the coexistence of two solvent-dependent electronic species. The temperature dependence of the spectra of the bridging unit shows an inverse relationship between the solvent reorganization energy (lambda(s)) and the temperature.

Comparisons of measured rate constants with spectroscopically determined electron-transfer parameters.

This work involves comparison of rate constants measured for an intervalence (IV) compound with electron-transfer parameters derived from its optical absorption spectrum. The temperature-dependent rate constants for the radical cation having 3-tert-butyl-2,3-diazabicyclo[2.2.