Jl. Del Riccio et al., The electronic spectroscopy of 2,2 '-binaphthyl in solution, cryogenic matrix and supersonic jet, J PHYS CH A, 104(32), 2000, pp. 7442-7451
The electronic spectroscopy of 2,2'-binaphthyl near 330 nm has been investi
gated by absorption spectroscopy in room-temperature solution and Shpolskii
matrix at 4 K and by fluorescence excitation spectroscopy in a supersonic
free-jet expansion. In the solution and gas phase, where the molecules are
free to form the minimum-energy conformation, the spectra are quite differe
nt from those of 1,1'-binaphthyl and the parent naphthalene. However, when
frozen in a matrix, aspects of the electronic spectrum resembled features o
f the spectra of these molecules. The fluorescence excitation spectrum in t
he free jet showed several long progressions in the torsional vibration wit
h a characteristic, but anharmonic, frequency of about 30 cm(-1). The spect
rum was assigned as the 1(1)B <-- 1(1)A transition with an origin transitio
n, which, although it could not be observed, was estimated to be at 30 060
+/- 30 cm(-1). The frequency of 29 members of this progression allowed an a
ccurate torsional potential to be calculated, which was flattened at low en
ergy and approached harmonic at higher energy. The change in equilibrium to
rsional angle was estimated to be 32 degrees upon electronic excitation, wi
th the excited state being planar (either cis or trans). Several low-freque
ncy vibrations were assigned in the gas phase that probably involve motions
of the naphthalene structures as a whale about the central C-C bend. In th
e matrix, the torsional vibrations were frozen out, which allowed for the o
bservation and tentative assignment of several higher-frequency vibrations
resembling those of the bare naphthalene. The origin frequency was measured
at 28 460 cm(-1). The difference between the gas-phase and solid-phase fre
quencies was attributed to the constrained structure of the molecule in the
matrix.