Electronic spectroscopy of jet-cooled benzylidenecyclobutane, a sterically hindered styrene

Abstract

Articles you may be interested inResonance enhanced multiphoton ionization spectroscopy of carbon disulphideThe electronic spectrum of the styrene derivative, benzylidenecyclobutane, seeded in a supersonic jet expansion has been recorded using resonantly enhanced two-photon ionization spectroscopy. The main vibronic features in the spectrum are associated with a low frequency progression assigned to the torsional motion of the phenyl ring. Analysis of the observed torsional levels reveals an excited state potential energy surface characteristic of a planar equilibrium geometry which undergoes large amplitude motion and a ground state surface having a minimum at a torsional angle of 25°between the phenyl and vinyl groups. Ab initio calculations of the ground state torsional potential surface predict a minimum in the range of 28°-26°, depending on the size of the basis set. In these structures the cyclobutane ring adopts a puckering angle between 17°and 19°. Deuterated isotopomers have also been synthesized and their corresponding photoionization spectra analyzed to reveal the mixing between the torsion and other low frequency modes such as cyclobutane ring puckering. The extent of this mixing is found to be sensitive to the sites of deuteration on the molecule.

Electronic spectroscopy and molecular structure of jet-cooled diphenylamine and diphenylamine derivatives

“…19 Both helium and argon were used as carrier gases at typical pressures of 40 psi for He and 30 psi for Ar and expanded from a pulsed valve with a 1 mm orifice. To increase the vapor pressure of the solid samples both sample and nozzle were heated to 90°C.…”