Photodissociation spectroscopy of excimers in naphthalene clusters

Saigusa, Hiroyuki; Sun, Shihao; Lim, E. C.

doi:10.1021/j100204a005

Cited by 36 publications

(31 citation statements)

References 2 publications

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“…The new intermolecular force introduced with light absorption, the excimer interaction force, likely arises as a result of one or both of the following: (i) changes in the nodal structure of the molecular orbitals that occur following light absorption and (ii) changes in electron affinity and ionization potential of the system that occur following light absorption. This simple view of excimer relaxation may explain why it is generally observed in many systems comprising both atomic and conjugated organic chromophores. − Given that a change in nodal structural of the system wave function is necessary for light absorption (i.e., to compensate for the loss of spin angular momentum of the photon), it is not surprising that excimer relaxation is independent of many aspects of atomic and molecular structure. For molecules, side-chain sterics provide an effective means in which to inhibit excimer formation, ,, and those chromophores that exhibit appreciable π-stacking (overlap of ground-state π orbitals) seem most prone to excimer relaxation …”

Section: Results and Discussionmentioning

confidence: 99%

The Nature of Excimer Formation in Crystalline Pyrene Nanoparticles

et al. 2018

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Pyrene is an exemplary conjugated organic chromophore with a strong propensity for self-association through an excited-state process known as excimer formation. Pyrene “excimers” and molecular “excimers” more generally are strongly avoided in some applications, such as in light harvesting, yet have found widespread use in others, such as in sensing and structure determination. Despite this disparate view and despite their widespread use, a fundamental understanding of the structure and dynamics of these collective excitations remains outstanding. In this work, we shed key insights into the nature of excimer formation in crystalline pyrene. We developed a flash precipitation procedure incorporating a polymer additive that enabled us to prepare aqueous suspensions of crystalline pyrene nanoparticles. We provide evidence that the molecular-level packing in the nanoparticles is equivalent to the equilibrium packing of the single crystal and show that excimer formation is the primary excited-state decay pathway. We find that excimer formation in the crystalline pyrene nanoparticles occurs in two stages on a picosecond time scale and suggest that intermolecular structural dynamics are largely responsible for the observed two-stage dynamics. We discuss an exciton theory description of molecular “excimers” and provide insights into their mechanism of formation, which we argue is best viewed simply as the relaxation of a singlet exciton into an excimer geometry.

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Section: Results and Discussionmentioning

confidence: 99%

The Nature of Excimer Formation in Crystalline Pyrene Nanoparticles

et al. 2018

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“…For example, structural information on naphthalene trimer has been extracted from rotational coherence spectroscopy (23). Excimer formation dynamics has been studied by Lim's group through fluorescence spectroscopy (24)(25)(26)(27)(28). Excitonic interactions depend strongly on the distance and relative orientation of the transition moments of monomer units.…”

mentioning

confidence: 99%

Excitonic couplings and electronic coherence in bridged naphthalene dimers

Tretiak

Zhang

Chernyak

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

104

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The electronic excitations of naphthalene and a family of bridged naphthalene dimers are calculated and analyzed by using the Collective Electronic Oscillator method combined with the oblique Lanczos algorithm. All experimentally observed trends in absorption profiles and radiative lifetimes are reproduced. Each electronic excitation is linked to the corresponding real-space transition density matrix, which represents the motions of electrons and holes created in the molecule by photon absorption. Two-dimensional plots of these matrices help visualize the degree of exciton localization and explain the dependence of the electronic interaction between chromophores on their separation. R elating electronic excitations of molecular aggregates to those of the individual chromophores is a long-standing fundamental problem with numerous applications to organic superlattices and biological complexes (1, 2).Considerable effort has been devoted to clusters of the simplest aromatic molecules such as napthalene and benzene (3-7). Supersonic beam techniques have made it possible to study the excited-state dynamics and obtain detailed information about geometries and intermolecular interactions in these clusters (8-10). Naphthalene is one of the most thoroughly studied chromophores in crystals and in the gas phase both theoretically and experimentally (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). Calculations provided a test for quantum mechanical theories of molecular electronic structure (16,17). In recent years, detailed information about naphthalene clusters has been obtained through high-resolution rotational spectroscopy analysis (22, 23). For example, structural information on naphthalene trimer has been extracted from rotational coherence spectroscopy (23). Excimer formation dynamics has been studied by Lim's group through fluorescence spectroscopy (24-28). Excitonic interactions depend strongly on the distance and relative orientation of the transition moments of monomer units. The geometry can be obtained from high-resolution vibronic spectra and nonlinear Raman spectroscopy (10,22,29). Extensive study of benzene has been carried out as well. Recent interest focused on the structure and properties of benzene clusters (30-36). Isotopically mixed benzene clusters have been used in the investigation of intermolecular interactions. Discrete exciton spectra were observed for benzene dimers (9, 37).In this paper, we analyze the absorption spectra of naphthalene and a family of naphthalene-bridge-naphthalene systems DN-2, DN-4, and DN-6 (see Fig. 1) (38-41). These molecules may be regarded as naphthalene dimers where pairs of naphthalene chromophores are held at fixed distances and orientations by a rigid polynorbornyl-type bridge of variable length (two, four, or six bonds, respectively). The UV-spectra and radiative decay rates of these dimers have been measured (39-41) and interpreted by using a simple exciton model (42). Within this model, each excited state of the monomer generates two states in the dimer. The interac...

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“…), exciton resonance interaction is assumed to play a significant role in the formation of their excimers. [29][30][31][32] In the present case, the excitation energy for the S 1 S 0 transition of 2-cynonaphthalene is 1150 cm À1 , smaller than that of naphthalene and all the transitions in the FE spectrum of the mixed dimer are recognized as the corresponding red-shifted vibronic transitions of 2-CNN monomer. Therefore, the excitations in the NÁ Á Á2-CNN dimer are localized on the 2-CNN moiety and, unlike the homodimers, excitation exchange between two moieties at large separation is not permissible.…”

Section: Exciplex Of the Mixed Dimermentioning

confidence: 44%

Exciplex emission from the mixed dimer of naphthalene and 2-cyanonaphthalene in a supersonic jet

Das

Mahato

Nandi

et al. 2002

Phys. Chem. Chem. Phys.

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The photophysical behavior for the S 1 S 0 transition of the van der Waals mixed dimer of naphthalene and 2cyanonaphthalene has been investigated by use of laser-induced fluorescence spectroscopy in a supersonic free jet expansion. The structure of the dimer in the ground state has been computed by electrostatic and ab initio quantum chemical calculations. Our experimental results show that unlike the behavior of the molecules in nonpolar solutions, the jet-cooled dimer emits exciplex fluorescence upon excitation to the S 1 state. Charge transfer interactions between the naphthalene donor and the cyanonaphthalene acceptor and orbital overlap between the nearly identical p-systems of the two molecules are considered to be the main factors for the stability of the exciplex in the jet.

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Photodissociation spectroscopy of excimers in naphthalene clusters

Cited by 36 publications

References 2 publications

The Nature of Excimer Formation in Crystalline Pyrene Nanoparticles

The Nature of Excimer Formation in Crystalline Pyrene Nanoparticles

Excitonic couplings and electronic coherence in bridged naphthalene dimers

Exciplex emission from the mixed dimer of naphthalene and 2-cyanonaphthalene in a supersonic jet

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