Position isomerism on one and two photon absorption in multibranched chromophores: a TDDFT investigation.

CK's Secondary address during the work : FOTON-INSA UMR6082 INSA de Rennes 20 Avenue des Buttes de Coësmes CS70839 F-35708 RENNES Cedex 7International audienceRecently, branching and click chemistry strategies have been combined to design a series of optically active chromophores built from triazole moieties. These triazole based multipolar chromophores have shown to be promising candidates for two-photon absorption (TPA) transparency optimization in perspective of optical limiting in the visible region. In this work, the nature of one- and two-photon absorption properties in a family of triazole based chromophores has been investigated using hybrid time dependent density functional theory (TD-DFT). We use recent extensions of TD-DFT to determine nonlinear optical responses, and Natural Transition Orbitals to analyze the underlying electronic processes. Our results are also interpreted in the framework of the Frenkel exciton model. In agreement with experimental data, we found that introducing triazole moiety into multibranched chromophores substantially modifies their optical behavior due to changes in electronic delocalization and charge-transfer properties between donating end-groups and branching center that can be controlled by the triazole ring. Structural conformations via modulation of the torsion between phenyl and triazole rings significantly alter excited state electronic structure. Moreover, isomer positioning also greatly influences both linear and nonlinear optical responses such as TPA. Our theoretical findings allow elucidating these differences and contribute to the general understanding of structure-property relations. Consequently, interplay of donor/acceptor strength, triazole regioisomerism, and branching are shown to provide flexible means allowing for precise tuning of both linear and nonlinear optical responses, thus opening new perspectives towards synergic TPA architectures

Synthesis, Fluorescence and Two-Photon Absorption Properties of Multichromophoric Boron-Dipyrromethene Fluorophores for Two-Photon-Excited Fluorescence Applications

International audienceThe synthesis and the characterization of new multichromophoric boron-dipyrromethene dyes are described. Their absorption, photoluminescence as well as their two-photon absorption properties have been investigated. This work shows that assembling several dyes in conjugated multichromophoric structures is a promising strategy for improving the two-photon absorption properties of such fluorophores in the NIR region while retaining their excellent photoluminescence properties

Membrane imaging by simultaneous second-harmonic generation and two-photon microscopy

International audienceWe demonstrate that simultaneous second-harmonic generation (SHG) and two-photon-excited fluorescence (TPEF) can be used to rapidly image biological membranes labeled with a styryl dye. The SHG power is made compatible with the TPEF power by use of near-resonance excitation, in accord with a model based on the theory of phased-array antennas, which shows that the SHG radiation is highly structured. Because of its sensitivity to local asymmetry, SHG microscopy promises to be a powerful tool for the study of membrane dynamics

Effect of chromophore-chromophore electrostatic interactions in the NLO response of functionalized organic-inorganic sol-gel materials

In the last years, important non-linear optical results on sol-gel and polymeric materials have been reported, with values comparable to those found in crystals. These new materials contain push-pull chromophores either incorporated as guest in a high Tg polymeric matrix (doped polymers) or grafted onto the polymeric matrix. These systems present several advantages; however they require significant improvement at the molecular level - by designing optimized chromophores with very large molecular figure of merit, specific to each application targeted. Besides, it was recently stated in polymers that the chromophore-chromophore electrostatic interactions, which are dependent of chromophore concentration, have a strong effect into their non-linear optical properties. This has not been explored at all in sol-gel systems. In this work, the sol-gel route was used to prepare hybrid organic-inorganic thin films with different NLO chromophores grafted into the skeleton matrix. Combining a molecular engineering strategy for getting a larger molecular figure of merit and by controlling the intermolecular dipole-dipole interactions through both: the tuning of the push-pull chromophore concentration and the control of TEOS (Tetraethoxysilane) concentration, we have obtained a r33 coefficient around 15 pm/V at 633 nm for the classical DR1 azo-chromophore and a r33 around 50 pm/V at 831 nm for a new optimized chromophore structure.Comment: 10 pages, 11 figures, 1 tabl

Enhanced two-photon absorption of organic chromophores: theoretical and experimental assessments

C. Katan present address: CNRS UMR6082 FOTON, INSA de Rennes, 20 avenue des Buttes de Coësmes, CS 70839, 35708 RENNES cedex 7, FranceInternational audienceFunctional organic materials with enhanced two-photon absorption (TPA) lead to new technologies in the fields of chemistry, biology, and photonics. In this article we review experimental and theoretical methodologies allowing detailed investigation and analysis of TPA properties of organic chromophores. This includes femtosecond two-photon excited fluorescence (TPEF) experimental setups and quantum-chemical methodologies based on time-dependent density functional theory (TD-DFT). We thoroughly analyze physical phenomena and trends leading to large TPA responses of a few series of model chromophores focusing on the effects of symmetric and asymmetric donor/acceptor substitution and branching

Two-photon Absorption Engineering of 5-(Fluorenyl)-1,10-phenanthroline-based Ru(II) Complexes

International audienceThis study deals with the fine tuning of the photophysical characteristics, and especially two-photon absorption (2PA) properties, of several homo- and heteroleptic ruthenium(II) complexes involving 5-substituted-1,10-phenanthroline ligands. The 2PA spectra of the complexes were determined in the 700-930 nm range by investigating their two-photon excited luminescence (2PEL). Structure - linear and nonlinear optical properties correlations are discussed, and potential applications (therapy and optical power limiting in the near infrared) can be anticipated

Novel chromophores from alternated pyridine–ethylenedioxythiophene unit oligomers: dramatic enhancement of photoluminescence properties in elongated derivatives

C. Katan present address: CNRS UMR6082 FOTON, INSA de Rennes, 20 avenue des Buttes de Coësmes, CS 70839, 35708 RENNES cedex 7, FranceInternational audienceNovel chromophores based on the alternation of electron-poor (pyridyl) and electron-rich (ethylenedioxythienyl) heterocycles were synthesized for the first time and shown to exhibit attractive optical properties in relation with their specific electronic and geometrical (coiled structure) features

Strong enhancement of two-photon absorption properties in synergic 'semi-disconnected' multiporphyrin assemblies designed for combined imaging and photodynamic therapy.

International audienceThe synthesis and photophysical properties of new multiporphyrin assemblies are described. Their design, based on a smooth electronic disconnection between two-photon absorbing (2PA) octupolar or quadrupolar cores and the peripheral porphyrins, leads to a major increase in (non-resonant) 2PA responses in the NIR, while fully retaining the fluorescence and photosensitization properties of isolated porphyrins. This approach, which involves electronic coupling of semi-disconnected moieties in the higher excited states of the synergic systems, is of interest to fully benefit from the advantages of selective 2PA for application in combined two-photon high resolution imaging and photodynamic therapy