Title: Charge-Transfer State and Large First Hyperpolarizability Constant in a Highly Electronically Coupled Zinc and Gold Porphyrin Dyad
Authors: Fortage, Jérôme ×
Scarpaci, Annabelle
Viau, Lydie
Pellegrin, Yann
Blart, Errol
Falkenström, Magnus
Hammarström, Leif
Asselberghs, Inge
Kellens, Ruben
Libaers, Wim
Clays, Koen
Eng, Mattias P
Odobel, Fabrice #
Issue Date: Jul-2009
Publisher: VCH Verlagsgesellschaft
Series Title: Chemistry - a European Journal vol:15 issue:36 pages:9058-9067
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(.)) 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=2100x10(-30) esu at lambda=1064 nm), thus highlighting the valuable nonlinear optical properties of this new type of push-pull porphyrin system.
ISSN: 0947-6539
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Molecular Imaging and Photonics
× corresponding author
# (joint) last author

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