Charge transfer state and large first hyperpolarizability in a highly electronically coupled zinc and gold porphyrin dyad
Artikel i vetenskaplig tidskrift, 2009

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.

NONLINEAR-OPTICAL PROPERTIES

TRIPLET EXCITED-STATES

CRYSTAL-STRUCTURE

2-PHOTON ABSORPTION

ELECTROCHEMICAL PROPERTIES

EFFECTIVE CORE POTENTIALS

DENSITY-FUNCTIONAL THEORY

SENSITIZED SOLAR-CELLS

HYPER-RAYLEIGH SCATTERING

ORGANIC-DYES

Författare

Jerome Fortage

Annabelle Scarpaci

Lydie Viau

Yann Pellegrin

Errol Blart

Magnus Falkenström

Leif Hammarström

Inge Asselberghs

Ruben Kellens

Wim Libaers

Koen Clays

Fabrice Odobel

Chemistry - A European Journal

0947-6539 (ISSN) 1521-3765 (eISSN)

Vol. 15 36 9058-9067

Ämneskategorier

Fysikalisk kemi

Teoretisk kemi

Organisk kemi