First measurements of fluorescence excitation spectra of the recently synthesized rigid stilbene analog 1,1'-bi(benzocyclobutylidene) in a supersonic jet expansion show that, in contrast to the parent compd., both the trans- and the cis-conformer fluoresce under these conditions. The excitation energy dependence of fluorescence lifetimes indicates the onset of an efficient non-radiative decay channel above energy thresholds of 1340 cm-1 and 990 cm-1 for the trans- and cis-form, resp., which is assigned to photoisomerization in the singlet state. From an RRKM anal. of the microcanonical rate coeffs. an est. of the high pressure limit of the thermal photoisomerization rate coeff. is obtained and compared with photoisomerization rate coeffs. measured in low viscosity soln. and in thermal vapor. There are strong indications that for this compd. there are no dynamic or static solvent induced effects that lead to an anomalous acceleration of the reaction in soln. [on SciFinder(R)]     «

First measurements of fluorescence excitation spectra of the recently synthesized rigid stilbene analog 1,1'-bi(benzocyclobutylidene) in a supersonic jet expansion show that, in contrast to the parent compd., both the trans- and the cis-conformer fluoresce under these conditions. The excitation energy dependence of fluorescence lifetimes indicates the onset of an efficient non-radiative decay channel above energy thresholds of 1340 cm-1 and 990 cm-1 for the trans- and cis-form, resp., which is a...     »

Laser induced fluorescence (excitation fluorescence excitation spectrum, lifetimes and photoisomerization of jet-cooled 1,1'-bi(benzocyclobutylidene) conformers) Conformation Conformers Electronic transition Normal modes Physical process kinetics Potential barrier Vibrational frequency (fluorescence excitation spectrum, lifetimes and photoisomerization of jet-cooled 1,1'-bi(benzocyclobutylidene) conformers) Diastereomers (geometric fluorescence excitation spectrum, lifetimes and photoisomerization of jet-cooled 1,1'-bi(benzocyclobutylidene) conformers) Fluorescence excitation (laser induced fluorescence excitation spectrum, lifetimes and photoisomerization of jet-cooled 1,1'-bi(benzocyclobutylidene) conformers) Isomerization Isomerization kinetics (photoisomerization fluorescence excitation spectrum, lifetimes and photoisomerization of jet-cooled 1,1'-bi(benzocyclobutylidene) conformers) Expansion (supersonic fluorescence excitation spectrum, lifetimes and photoisomerization of jet-cooled 1,1'-bi(benzocyclobutylidene) conformers) benzocyclobutylidenebenzocyclobutane isomer fluorescence excitation photoisomerization     «

Laser induced fluorescence (excitation fluorescence excitation spectrum, lifetimes and photoisomerization of jet-cooled 1,1'-bi(benzocyclobutylidene) conformers) Conformation Conformers Electronic transition Normal modes Physical process kinetics Potential barrier Vibrational frequency (fluorescence excitation spectrum, lifetimes and photoisomerization of jet-cooled 1,1'-bi(benzocyclobutylidene) conformers) Diastereomers (geometric fluorescence excitation spectrum, lifetimes and photoisomerizati...     »

CAN 137:185189 22-9 Physical Organic Chemistry Institut fur Physikalische Chemie der Universitat, Gottingen, Germany. Journal 0044-3336 72610-87-8P (trans-Benzocyclobutylidenebenzocyclobutane); 72610-88-9P (cis-Benzocyclobutylidenebenzocyclobutane) Role: CPS (Chemical process), PEP (Physical, engineering or chemical process), PRP (Properties), PUR (Purification or recovery), PYP (Physical process), PREP (Preparation), PROC (Process) (fluorescence excitation spectrum, lifetimes and photoisomerization of jet-cooled 1,1'-bi(benzocyclobutylidene) conformers)     «

CAN 137:185189 22-9 Physical Organic Chemistry Institut fur Physikalische Chemie der Universitat, Gottingen, Germany. Journal 0044-3336 72610-87-8P (trans-Benzocyclobutylidenebenzocyclobutane); 72610-88-9P (cis-Benzocyclobutylidenebenzocyclobutane) Role: CPS (Chemical process), PEP (Physical, engineering or chemical process), PRP (Properties), PUR (Purification or recovery), PYP (Physical process), PREP (Preparation), PROC (Process) (fluorescence excitation spectrum, lifetimes and photoisomeriz...     »