1. Charge-Transfer State and Large First Hyperpolarizability Constant in a Highly Electronically Coupled Zinc and Gold Porphyrin Dyad
- Author
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Koen Clays, Magnus Falkenström, Yann Pellegrin, Annabelle Scarpaci, Inge Asselberghs, Jérôme Fortage, Mattias P. Eng, Wim Libaers, Leif Hammarström, Fabrice Odobel, Ruben Kellens, Errol Blart, Lydie Viau, Chimie Et Interdisciplinarité : Synthèse, Analyse, Modélisation (CEISAM), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut Lavoisier de Versailles (ILV), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Department of Chemistry, University of Leuven (INPAC), Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), Programming Technology Laboratory (PROG), and Vrije Universiteit Brussel (VUB)
- Subjects
photochemistry ,Absorption spectroscopy ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,nonlinear optics ,charge transfer ,Hyperpolarizability ,porphyrinoids ,General Chemistry ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Porphyrin ,Catalysis ,0104 chemical sciences ,Photoexcitation ,chemistry.chemical_compound ,Ultrafast laser spectroscopy ,Molecular orbital ,[CHIM.COOR]Chemical Sciences/Coordination chemistry ,fluorescence ,Ground state ,HOMO/LUMO - Abstract
We report the synthesis and the characterizations of a novel dyad composed of a zinc porphyrin (ZnP) linked to a gold porphyrin (AuP) through an ethynyl spacer. The UV/Vis absorption spectrum and the electrochemical properties clearly reveal that this dyad exhibits a strong electronic coupling in the ground state as evidenced by shifted redox potentials and the appearance of an intense charge-transfer band localized at lambda = 739 nm in dichloromethane. A spectroelectrochemical study of the dyad along with the parent homometallic system (i.e., ZnP-ZnP and AuP-AuP) was undertaken to determine the spectra of the reduced and oxidized porphyrin units. Femtosecond transient absorption spectroscopic analysis showed that the photoexcitation of the heterometallic dyad leads to an ultrafast formation of a charge-separated state (+ZnP-AuP center dot) that displays a particularly long lifetime (tau=4 ns in toluene) for such a short separation distance. The molecular orbitals of the dyad were determined by DFT quantum-chemical calculations. This theoretical study confirms that the observed intense band at lambda = 739 nm corresponds to an interporphyrin charge-transfer transition from the HOMO orbital localized on the zinc porphyrin to LUMO orbitals localized on the gold porphyrin. Finally, a Hyper-Rayleigh scattering study shows that the dyad possesses a large first molecular hyperpolarizability coefficient (beta = 2100 x 10(-30) esu at lambda = 1064 nm), thus highlighting the valuable nonlinear optical properties of this new type of push-pull porphyrin system.
- Published
- 2009
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