Pump-probe fluorescence studies of excimer formation and dissociation for the van der Waals dimer of fluorene

Saigusa, Hiroyuki; Lim, E. C.

doi:10.1021/j100159a046

Cited by 26 publications

(16 citation statements)

References 1 publication

(1 reference statement)

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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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“…Another strong argument for dimers optical detection in flames relies on the fluorescence lifetimes of the excited species. It is known that dimers of PAHs have substantially longer fluorescence lifetimes than PAH monomers 44,49 , which can be highlighted by delaying the detection gate width of the fluorescence signals. In order to strengthen the evidence of dimer formation in the sooting flame, we carried out a series of LIF measurements in which we varied the gate delay (GD) of the ICCD camera with respect to the peak of the temporal LIF signal, considered to be the prompt fluorescence in this case.…”

Section: Effect Of the Delay On The Recorded Lif Spectramentioning

confidence: 99%

Dimers of polycyclic aromatic hydrocarbons: the missing pieces in the soot formation process

Mercier

Carrivain

Irimiea

et al. 2019

Phys. Chem. Chem. Phys.

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“…The fluorene core is assumed, by analogy with fluorene itself, to be the source of emission 9 and thus close attention was paid to orientation, intermolecular distances and, particularly, close contacts that would indicate intermolecular interactions. Both fluorescent crystals exhibit dimers with parallel fluorene aromatic systems in close, -stacked contact facilitating the formation of van der Waals dimers and/or excimers in the solid state analogous to those postulated in the gas phase 10,11 and similar to excimer emission in crystals of pyrene 12 and perulene. 13 Subtle differences in interplanar fluorene distances occur in the two crystals and the orientation and registration of these groups also differ slightly, as illustrated in Figs.…”

Section: Resultsmentioning

confidence: 76%

Novel Fluorene Based Host Compounds Designed to Probe Solid-State Fluorescence

Scott

Yamada

Tanaka

2004

Bulletin of the Chemical Society of Japan

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Two novel host compounds, 2,7-bis(3-hydroxy-3,3-diphenylprop-1-ynyl)fluorene and 2,7-bis [3,3-(biphenyl-2,2 0 -diyl)-3-hydroxyprop-1-ynyl]fluorene have been synthesized. Many inclusion complexes of these host compounds with common volatile guests show solid-state fluorescence, which is ascribed to the existence of rigid dimers in the crystal structures, allowing excimer formation. Differential intermolecular interactions about the fluorescent moiety result in various colored emissions.Guest specific fluorescence in solution is frequently used in sensing applications, 1 but solid-state fluorescence in host:guest complexes is rarer. Host complexes or sensors have been designed to respond selectively to specific organic analytes 2 (though fluorescence quenching, rather than enhancement, is more frequent in such applications 3 ). Recently, fluorescence due to toluene inclusion in crystals of disubstituted anthracenes 4 has been reported and we have previously noted guest specific solid-state fluorescence in crystalline inclusion complexes of 2,7-bis(3-hydroxy-3,3-diphenylprop-1-ynyl)fluoren-9-one (1).5 Analysis of molecular packing in the crystalline state led to the suggestion that emission was occurring from dimers that formed excimers due to the interactions of close stacked systems. Also of importance was the absence of strong intermolecular interactions (such as hydrogen bonds) to the fluorescent fluorenone core as these would allow radiationless decay to occur in analogous fashion to solution phase hydrogen-bond donors.5b To test this hypothesis, we have synthesized two new hosts, 2,7-bis(3-hydroxy-3,3-diphenylprop-1-ynyl)fluorene (2a) and 2,7-bis [3,3-(biphenyl-2,2 0 -diyl)-3-hydroxyprop-1-ynyl]fluorene (2b) as shown in Scheme 1, and have screened a range of inclusion complexes for the onset of fluorescence.Crystallographic investigations, used to probe intermolecular interactions in the solid state, provide a basis for explaining the source of solid state fluorescence and changes in emission max . ExperimentalPreparation of 2a. 2,7-Dibromofluorene (2.0 g, 6.2 mmol),

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Pump-probe fluorescence studies of excimer formation and dissociation for the van der Waals dimer of fluorene

Cited by 26 publications

References 1 publication

The Nature of Excimer Formation in Crystalline Pyrene Nanoparticles

The Nature of Excimer Formation in Crystalline Pyrene Nanoparticles

Dimers of polycyclic aromatic hydrocarbons: the missing pieces in the soot formation process

Novel Fluorene Based Host Compounds Designed to Probe Solid-State Fluorescence

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