Protonated Benzaldehyde Clusters:

1. GMPCS Excited state characterization of protonated aromatic molecules I. Alataa,c, C. Dedondera,b, M. Broquiera,b, A. Patzerd, O.Dopferd andC. Jouveta,b a) CLUPS Centre laser de l'Université Paris Sud, b) ISMO Institut des Sciences Moléculaires d'Orsay (CNRS –UPSud, FRE 3363) c) Atomic Energy Commission of Syria, Damascus, P.O. Box 6091, d) Institut für Optik und Atomare Physik, Technische Universität Berlin. Introduction:Very little is known about the structure, dynamics, and electronic properties of protonated aromatic molecules, of even simple isolated protonated PAHs ions. Protonated aromatic molecules present a fundamental interest in physical organic chemistry : dynamics and selectivity of chemical processes (1). Also they play a role as short-lived intermediates in a broad range of environments, (astrochemistry (2), jet engine gas exhaust and in various hydrocarbon plasmas). We characterized the first electronic excited state of the protonated PAHn ; n=2,3,4 (n: number of aromatic rings) in the gaz phase, with enoughf resolution to investigate the vibrational structure of these species, Ab initio calculations have been done, which are in excellent agreement with the experimental results . 1) Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, Wiley, New York, 5th edn, 2001. 2) Nature 391(6664), 15 January 1998, The protonated molecules have closed shell electronic structure, like the neutral molecules while the radical cation heve an open shell electronic structure Closed-shell neutral molecules and their protonated counterparts have high chemical stability. The protonated and neutral molecules have a closed shell electronic structure The Radical cation have an open shell electronic structure Experiment Fragmentation produit par le laser Electronic transition UV Electronic transition IR/visible Fragmentation produit par la collision S0-S1=HOMO_LUMO EX:Protonated Anthracene Protonated anthracene detection of neutral fragment Cation C13 Absorption spectrum of protonated Naphthalene, Anthracene and Tetracene Even number Excitation with charge transfer Tetracene Odd number Excitation without charge transfer Anthracene LUMO HOMO-1 HOMO The molecule is symmetric with respect to The proton position S1-S0 = 2.53 eV The molecule is not symmetric with respect to The proton position S1-S0 = 1.82 eV Variation of the first S1-S0 electronic transition of linear PAH with the number of aromatic rings Protonated Benzaldehyde Clusters: Resonant photodissociation spectra of the S1←S0 transition of BZH+ (reproduced from ref 30) and BZH+-L dimers with L=Ar and N2. The origin bands and first vibrational transitions are indicated. No signal is detected in the spectral range 20 000-23 300 cm-1. increase in the proton affinity of BZH+ upon S1 excitation ricc2-SVP turbomole Alexander Patzer, Max Zimmermann, Ivan Alata, Christophe Jouvet, and Otto Dopfer, The Journal Of Physical Chemistry A 114, 12600-12604 (2010).