Monomer Emission from Excimer Forming Crystals: Pyrene and Perylene

Chu, Nori Y. C.; Kearns, David R.

doi:10.1080/15421407208083580

Cited by 46 publications

(12 citation statements)

References 9 publications

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“…The monomer fluorescence spectrum in solution is well characterized by its sharp vibronic bands. On the contrary, the fluorescence spectrum of the nanoaggregates shows a broad emission band in the 420–600 nm region with the maximum at 465 nm, which agrees well with that of the emission spectrum recorded for a solution with high concentration of pyrene and hence this emission band of the nanoaggregates may be assigned to the excimer. , Position of this emission maximum may be compared with that appearing at 450 nm for α-pyrene crystals and that at 475 nm for the microcrystalline pyrene film. ,,,,, Appearance of the excimer emission, like in the case of perylene nanoaggregates, suggests that molecular packing in pyrene nanoaggregates consists of the dimeric or α-form of the crystal. Theoretical calculations predict that in the ground electronic state of α-pyrene crystals, the interplanar separation of the planar aromatic molecules aligned in a sandwich configuration is about 3.4 Å, which decreases by about 0.2 Å in the excited state. , …”

Section: Results and Discussionsupporting

confidence: 77%

“…Temperature dependence of the luminescence spectra of both α- and β-perylene crystals has been studied extensively in the 4.2–300 K range using both steady-state and time-resolved techniques to understand the origin of various bands appearing in their luminescence spectra. ,,,,,,,,, These works revealed that strong ST exciton emission is the most important feature of each of the α- and β-perylene crystals. In the case of β-perylene crystals, the most intense vibronic band of the monomeric ST exciton emission appears at ca.…”

Section: Results and Discussionmentioning

confidence: 99%

“…At room temperature, pyrene crystals have only dimeric structure and hence the crystal is in the α-form . As a consequence of the coplanar sandwiched dimeric structure of the α-pyrene and α-perylene crystals, structureless excimer-type emission is the most prominent feature in the steady-state emission spectra observed under most conditions. , Under certain special conditions, however, emission spectra of these crystals have shown structures characteristic of monomers in addition to excimer emissions. , …”

Section: Introductionmentioning

confidence: 99%

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Exciton Dynamics in Pyrene and Perylene Nanoaggregates

Manna

Palit

2020

J. Phys. Chem. C

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Photophysical and diffusion properties of excitons generated in perylene and pyrene nanoaggregates have been investigated using steady state as well as time-resolved absorption and emission spectroscopic techniques. The average sizes and heights of the nanoaggregates prepared by the reprecipitation method have been estimated as 120 ± 20 and 60 ± 10 nm, respectively. X-ray diffraction spectra reveal that molecular packing in these nanoaggregates is very similar to that in the α-form (face-to-face pair or dimeric structure) of the crystals, but with possibilities of a large number of disordered regions consisting of monomer molecules. Therefore, following photoexcitation of nanoaggregates, both monomeric and dimeric exciton states are populated. This work, for the first time, could reveal the dynamics of interactions between these two kinds of exciton states, because of which the photophysical and diffusion properties of the excitons are significantly different from those in single crystals. Population yield of the dimeric self-trapped exciton or E state, which is the lowest energy exciton state, is negligibly small via self-trapping of dimeric excitons (dimeric channel) in the <200 ps time domain because of efficient energy transfer from dimeric excitons to monomers. However, the monomeric excitons, which are populated either independently through direct photoexcitation or by energy transfer from the dimeric excitons, contribute to an additional (monomeric) channel populating the E state via energy transfer processes occurring in the nanosecond (ns) time domain. Diffusion coefficients and diffusion lengths of the monomeric excitons estimated in both these nanoaggregates are comparable to those in the β-form of the crystals but much larger than those values reported for the α-form and hence ensure a better or comparable efficiency of energy migration in nanoaggregates as compared to that of single crystals.

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Section: Results and Discussionsupporting

confidence: 77%

Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Exciton Dynamics in Pyrene and Perylene Nanoaggregates

Manna

Palit

2020

J. Phys. Chem. C

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“…As shown in Figure a, photoluminescence (PL) measurements were performed to study the effect of perylene domains on the optical properties of the seed wires. The spectrum (black curve) from pure coronene microwire film spin-coated on a quartz substrate exhibits multiple emission bands at 475, 484, 502, 512, and 524 nm, corresponding to the typical blue-green light of coronene. , In the previous report, , β-phase perylene crystals exhibited three emission peaks at 522, 564, and 627 nm. Meanwhile, the perylene molecule exhibits its absorption at around 400–450 nm in diluted solution. , Hence, energy transfer from coronene to perylene cannot occur because there is no overlap of the PL spectrum of green-emitting β-phase perylene crystals with the absorption spectrum of coronene.…”

mentioning

confidence: 78%

“…The spectrum (black curve) from pure coronene microwire film spin-coated on a quartz substrate exhibits multiple emission bands at 475, 484, 502, 512, and 524 nm, corresponding to the typical blue-green light of coronene. , In the previous report, , β-phase perylene crystals exhibited three emission peaks at 522, 564, and 627 nm. Meanwhile, the perylene molecule exhibits its absorption at around 400–450 nm in diluted solution. , Hence, energy transfer from coronene to perylene cannot occur because there is no overlap of the PL spectrum of green-emitting β-phase perylene crystals with the absorption spectrum of coronene. The spectrum (orange curve) from square α-phase perylene sheet film shows an emission band at 560 nm, as reported previously. , Besides a shoulder peak at 478 nm, the PL spectrum (blue curve) of the microdumbbells shows an emission band at 517 nm, and that (cyan curve) of perylene growth on the side surfaces of the seed wires consists of a weak shoulder peak at 475 nm and another peak at 525 nm.…”

mentioning

confidence: 78%

Facet-Selective Growth of Organic Heterostructured Architectures via Sequential Crystallization of Structurally Complementary π-Conjugated Molecules

et al. 2017

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In contrast to those for their polymeric counterparts, the controlled construction of organic heterostructured architectures derived from π-conjugated organic molecules has been rare and remains a great challenge. Herein, we develop a simple single-step solution strategy for the realization of organic heterostructures comprising coronene and perylene. Under a sequential crystallization process, an efficient doping step for coronene and perylene domains enables their perfect lattice matching, which facilitates facet-selective epitaxial growth of perylene domains on both the tips and the side surfaces of the preformed seed microwires by manipulating the growth pathways of the two pairs of materials. The present synthetic route provides a promising platform to investigate the detailed formation mechanism of complex organic heterostructures with specific topological configurations, further directing the construction of more functional heterostructured materials.

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A BF₂ Chelate Exhibiting Excimer‐like Fluorescence with an Unusually Large Stokes Shift in the Crystalline Phase

Bozdemir

Woodford

Waddell

et al. 2023

Chemistry A European J

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The target mono-BF 2 complex is weakly emissive in fluid solution because radiationless decay of the excitedsinglet state is promoted through an intramolecular N•••HÀ N hydrogen bond. The lack of mirror symmetry for this compound is attributed to vibronic effects, as reported previously for the bis-BF 2 complex (BOPHY). Red-shifted fluorescence is observed from single crystals, the emission quantum yield approaching 30 % with a fluorescence lifetime of 2 ns. The large Stokes shift of 5,700 cm À 1 helps minimize self-absorption. Crystallography indicates that the internal fold and twist angles are increased substantially in the crystal, but the hydrogen bond is weakened relative to solution. The crystal structure is compiled from pairs of head-to-tail molecules having a shift of ca. 4.1 Å and closest approach of ca. 3.5 Å. These molecular pairs are arranged in columns, which, in turn, assemble into sheets. The proximity favors excitonic coupling between individual molecules, with the coupling strength obtained by analysis of the absorption spectrum reaching ca. 1,000 cm À 1 . Both the ideal dipole approximation and the extended dipole methodology seriously overestimate the coupling strength, but the atomic transition charge density procedure leads to good agreement with experiment. Emission is attributed to the closely coupled molecular pair functioning in an excimer-like manner with the exciton trapped in a local minimum. Increasing temperature causes a slight blue shift and loss of fluorescence.

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Monomer Emission from Excimer Forming Crystals: Pyrene and Perylene

Cited by 46 publications

References 9 publications

Exciton Dynamics in Pyrene and Perylene Nanoaggregates

Exciton Dynamics in Pyrene and Perylene Nanoaggregates

Facet-Selective Growth of Organic Heterostructured Architectures via Sequential Crystallization of Structurally Complementary π-Conjugated Molecules

A BF₂ Chelate Exhibiting Excimer‐like Fluorescence with an Unusually Large Stokes Shift in the Crystalline Phase

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Monomer Emission from Excimer Forming Crystals: Pyrene and Perylene

Cited by 46 publications

References 9 publications

Exciton Dynamics in Pyrene and Perylene Nanoaggregates

Exciton Dynamics in Pyrene and Perylene Nanoaggregates

Facet-Selective Growth of Organic Heterostructured Architectures via Sequential Crystallization of Structurally Complementary π-Conjugated Molecules

A BF2 Chelate Exhibiting Excimer‐like Fluorescence with an Unusually Large Stokes Shift in the Crystalline Phase

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A BF₂ Chelate Exhibiting Excimer‐like Fluorescence with an Unusually Large Stokes Shift in the Crystalline Phase