Investigation of Two-Photon Absorption Properties in Branched Alkene and Alkyne Chromophores

Bhaskar, Ajit; Ramakrishna, G.; Lu, Zhiyuan; Twieg, Robert J.; Hales, Joel M.; Hagan, David J.; Stryland, Eric Van; Goodson, Theodore

doi:10.1021/ja060630m

Cited by 237 publications

(240 citation statements)

References 71 publications

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“…26 This may be another reason for the larger spectral red shift observed in chromophore 4. Goodson et al also showed that, for the D−π−A−π−D structure, replacement of a single bond by a double bond led to a larger red shift both in absorption and fluorescence than that by triple bond, 18,54,59 which is consistent with our experimental results. Moreover, similar phenomenon has also been observed in our previous study in which the branched chromophore, which formed by a simple unconjugated combination of two or three D−π−A−π−D moieties, showed only very small alteration in spectral features compared to the monomers, 12,28 whereas the chromophore formed by conjugated moieties, which have π bridge linkers, usually have a remarkable delocalized ICT state, and therefore, significantly different spectral features from those of isolated moieties.…”

supporting

confidence: 92%

Localized Emitting State and Energy Transfer Properties of Quadrupolar Chromophores and (Multi)Branched Derivatives

Yan

Chen

et al. 2012

J. Phys. Chem. A

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In order to better understand the nature of intramolecular charge and energy transfer in multibranched molecules, we have synthesized and studied the photophysical properties of a monomer quadrupolar chromophore with donor−acceptor−donor (D−A−D) electronic push−pull structure, together with its V-shaped dimer and star-shaped trimers. The comparison of steady-state absorption spectra and fluorescence excitation anisotropy spectra of these chromophores show evidence of weak interaction (such as charge and energy transfer) among the branches. Moreover, similar fluorescence and solvation behavior of monomer and branched chromophores (dimer and trimer) implies that the interaction among the branches is not strong enough to make a significant distinction between these molecules, due to the weak interaction and intrinsic structural disorder in branched molecules. Furthermore, the interaction between the branches can be enhanced by inserting π bridge spacers (−CC− or −CC−) between the core donor and the acceptor. This improvement leads to a remarkable enhancement of two-photon cross-sections, indicating that the interbranch interaction results in the amplification of transition dipole moments between ground states and excited states. The interpretations of the observed photophysical properties are further supported by theoretical investigation, which reveal that the changes of the transition dipole moments of the branched quadrupolar chromophores play a critical role in observed the two-photon absorption (2PA) cross-section for an intramolecular charge transfer (ICT) state interaction in the multibranched quadrupolar chromophores.

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supporting

confidence: 92%

Localized Emitting State and Energy Transfer Properties of Quadrupolar Chromophores and (Multi)Branched Derivatives

Yan

Chen

et al. 2012

J. Phys. Chem. A

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“…The excitation localization on one branch of a trimeric system has already been proven by photophysical experiments conducted on octupolar derivatives built from the TPAmine core 61,63,71 and on three-branched systems and conjugated dendrimers built from various joints/ cores. [61][62][63]70,77 4.2. Two-Photon Absorption.…”

Section: Geometry and Nature Of The Excited Statesmentioning

confidence: 87%

Two-Photon Transitions in Quadrupolar and Branched Chromophores: Experiment and Theory

et al. 2007

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A combined experimental and theoretical study is conducted on a series of model compounds in order to assess the combined role of branching and charge symmetry on absorption, photoluminescence, and twophoton absorption (TPA) properties. The main issue of this study is to examine how branching of quadrupolar chomophores can lead to different consequences as compared to branching of dipolar chromophores. Hence, three structurally related π-conjugated quadrupolar chromophores symmetrically substituted with donor end groups and one branched structure built from the assembly of three quadrupolar branches via a common donor moiety are used as model compounds. Their photophysical properties are studied using UV-vis spectroscopy, and the TPA spectra are determined through two-photon excited fluorescence experiments using femtosecond pulses in the 500-1000 nm range. Experimental studies are complemented by theoretical calculations. The applied theoretical methodology is based on time-dependent density functional theory, the Frenkel exciton model, and analysis in terms of the natural transition orbitals of relevant electronic states. Theory reveals that a symmetrical intramolecular charge transfer from the terminal donating groups to the middle of the molecule takes place in all quadrupolar chromophores upon photoexcitation. In contrast, branching via a central electron-donating triphenylamine moiety breaks the quadrupolar symmetry of the branches. Consequently, all Frank-Condon excited states have significant asymmetric multidimensional charge-transfer character upon excitation. Subsequent vibrational relaxation of the branched chromophore in the excited state leads to a localization of the excitation and fluorescence stemming from a single branch. As opposed to what was earlier observed when dipolar chromophores are branched via the same common electron-donating moiety, we find only a slight enhancement of the maximum TPA response of the branched compound with respect to an additive contribution of its quadrupolar branches. In contrast, substantial modifications of the spectral shape are observed. This is attributed to the subtle interplay of interbranch electronic coupling and asymmetry caused by branching.

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“…[33,36,57] In turn, exploitation of intermolecular interactions through branching strategies and the supramolecular approaches offers even more possibilities to tune or enhance TPA properties. This has already been demonstrated for branched chromophores built from the gathering of either dipolar [108][109][110][111][112][113][114][115][116][117][118][119][120][121][122][123] or quadrupolar [97,102,[124][125][126] sub-chromophores via common conjugated core moieties and multichromophore structures in which subchromophores interact only via electrostatic interactions. [127] Alternative routes such as those based on porphyrins, [128][129][130][131][132][133][134][135][136] oligomers and polymers [103,[137][138][139] have been explored as well.…”

Section: Introductionmentioning

confidence: 86%

Enhanced Two‐Photon Absorption of Organic Chromophores: Theoretical and Experimental Assessments

et al. 2008

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Investigation of Two-Photon Absorption Properties in Branched Alkene and Alkyne Chromophores

Cited by 237 publications

References 71 publications

Localized Emitting State and Energy Transfer Properties of Quadrupolar Chromophores and (Multi)Branched Derivatives

Localized Emitting State and Energy Transfer Properties of Quadrupolar Chromophores and (Multi)Branched Derivatives

Two-Photon Transitions in Quadrupolar and Branched Chromophores: Experiment and Theory

Enhanced Two‐Photon Absorption of Organic Chromophores: Theoretical and Experimental Assessments

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