@Article{JPhysChemA_113_5061, author = {O.F. Mohammed and S.A. Ahmed and E. Vauthey and E.T.J. Nibbering}, title = {{Photoinduced Ring-Opening of a Photochromic Dihydroindolizine Derivative Monitored with Femtosecond Visible and Infrared Spectroscopy}}, journal= {J. Phys. Chem. A}, ISSN = {1089-5639}, volume= {113}, number= {17}, pages = {5061-5065}, url = {http://pubs.acs.org/doi/abs/10.1021/jp811248u}, eprint= {http://www.unige.ch/sciences/chifi/publis/refs_pdf/ref00980.pdf}, doi= {10.1021/jp811248u}, abstract = {{We present results of a femtosecond spectroscopy study of the ring-opening dynamics of the photochromiccompound trimethyl-1′H-spiro[fluorene-9,1′-pyrrolo[1,2-b]pyridazines]-2′,3′,6′-tricarboxylate (also known asdihydroindolizine and abbreviated as DHI) in solvents of different polarities. We follow the ring-openingdynamics of photoexcited DHI by probing the transient response in the visible region between 450 and 700nm, as well as in the fingerprint region between 1100 and 1800 cm$^{-1}$. We conclude that photoexcited DHIconverts into the ring-opened betaine isomer while remaining in the electronic excited state. Subsequentelectronic excited-state decay on a time scale of 40-80 ps results in regeneration of ground-state DHI (0.75-0.9quantum yield) or betaine photoproduct, the exact value for DHI quantum yield recoveries and rates beingsolvent dependent. Figure Steady state of DHI in ACN-d$_3$, DCM-d$_2$, and TCE (A).Transient spectra of DHI at different pulse delays after 400 nm laserexcitation in ACN-d$_3$ (B), in DCM-d$_2$ (C), and in TCE (D).}}, year = {2009} }