Three-color polymorph-dependent luminescence: crystallographic analysis and theoretical study on excited-state intramolecular proton transfer (ESIPT) luminescence of cyano-substituted imidazo[1,2-a]pyridine

Mutai, Toshiki; Shono, Hideaki; Shigemitsu, Yasuhiro; Araki, Koji

doi:10.1039/c3ce42627k

Cited by 62 publications

(62 citation statements)

References 43 publications

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“…Polymorph‐dependent luminescence has been studied for 6‐CN‐HPIP, a molecule that undergoes ESIPT. This HPIP derivative (Figure ) has three polymorphs that fluoresce with different colors . The color of the emission is the result of different factors.…”

Section: Effect Of Intermolecular Interactions and The Environmentmentioning

confidence: 99%

“…Polymorph-dependent luminescence has been studied for 6-CN-HPIP,amolecule that undergoes ESIPT.T his HPIP derivative ( Figure 2) has three polymorphs that fluoresce with different colors. [87] The color of the emission is the result of different factors. First, the main effect comes from the molecules that are directly stacked with the emitterr ather than from the overall surroundings.S econd, the shifts in the emission energies come from the fact that the emitter is the keto form of 6-CN-HPIP surrounded by enol molecules with opposite dipole moment.…”

Section: Hversusjaggregationmentioning

confidence: 99%

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Exploring Potential Energy Surfaces for Aggregation‐Induced Emission—From Solution to Crystal

Crespo‐Otero

Blancafort

2019

Chemistry An Asian Journal

152

134

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Aggregation‐induced emission (AIE) is a phenomenon where non‐luminescent compounds in solution become strongly luminescent in aggregate and solid phase. It provides a fertile ground for luminescent applications that has rapidly developed in the last 15 years. In this review, we focus on the contributions of theory and computations to understanding the molecular mechanism behind it. Starting from initial models, such as restriction of intramolecular rotations (RIR), and the calculation of non‐radiative rates with Fermi's golden rule (FGR), we center on studies of the global excited‐state potential energy surfaces that have provided the basis for the restricted access to a conical intersection (RACI) model. In this model, which has been shown to apply for a diverse group of AIEgens, the lack of fluorescence in solution comes from radiationless decay at a CI in solution that is hindered in the aggregate state. We also highlight how intermolecular interactions modulate the photophysics in the aggregate phase, in terms of fluorescence quantum yield and emission color.

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Section: Effect Of Intermolecular Interactions and The Environmentmentioning

confidence: 99%

Section: Hversusjaggregationmentioning

confidence: 99%

Exploring Potential Energy Surfaces for Aggregation‐Induced Emission—From Solution to Crystal

Crespo‐Otero

Blancafort

2019

Chemistry An Asian Journal

152

134

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“…The requisite of chemical structures for ESIPT is the presence of an intramolecular hydrogen bond (H‐bond) between the proton donor (OH and NH 2 ) and the proton acceptor (N and CO) groups close to one another in a single molecule. Recent notable reports on the ESIPT fluorophores include the polymorph‐dependent emissive crystals, double proton transfer process with an extra‐large Stokes shift, amplified spontaneous emission, lasing system, environment‐sensitive multicolored materials, and the use as emitters with electrically generated intramolecular proton transfers . Most of ESIPT molecules show significant fluorescence in the solid states, not suffering from “concentration quenching” and thus serving as aggregation‐induced emission enhancement (AIEE) materials .…”

Section: Introductionmentioning

confidence: 99%

Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Zhang

Sakurai

Aotani

et al. 2018

Advanced Optical Materials

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solid-state emitters, electroluminescent devices, organic lasers, and so on. [1][2][3][4][5] Particularly, emission through excitedstate intramolecular proton transfer (ESIPT) mechanism with an extremely large Stokes shift [6][7][8][9] (anti-Kasha rule) suppresses excitation energy dissipation via self-absorption, providing attractive material platforms for optical device fabrication. [10,11] ESIPT is a photochemical process that produces a tautomer with a different electronic structure from the original excited form (Figure 1a). The requisite of chemical structures for ESIPT is the presence of an intramolecular hydrogen bond (H-bond) between the proton donor (OH and NH 2 ) and the proton acceptor (N and CO) groups close to one another in a single molecule. Recent notable reports on the ESIPT fluorophores include the polymorph-dependent emissive crystals, [12,13] double proton transfer process with an extra-large Stokes shift, [14] amplified spontaneous emission, [15][16][17] lasing system, [18][19][20] environment-sensitive multicolored materials, [21][22][23][24] and the use as emitters with electrically generated intramolecular proton transfers. [25] Most of ESIPT molecules show significant fluorescence in the solid states, not suffering from "concentration quenching" and thus serving as aggregation-induced emission enhancement (AIEE) materials. [26][27][28] The ESIPT process requires structural relaxations upon proton transfer, and thus a certain conformational freedom is allowed for the molecular structures. [29] The conformational freedom results in allowing the possible nonradiative pathways especially in solution (Figure 1b), giving AIEE characters to the ESIPT molecules. [30,31] The AIEE character is advantageous because light outputs from the systems are extremely high embedded into actual devices to avoid the concentration quenching. [32] However, most of the previous ESIPT as well as AIEE systems have been mostly reported in the rigid solid phase such as single crystals, polycrystals, or powders [11,12] -not in liquid crystals (LCs). Although columnar LCs with ESIPT-active cores were reported, [33,34] simple rod-shaped LC molecules embedded with ESIPT-active group have been limited. [35,36] In contrast to columnar and cubic liquid crystal phases with highly ordered structures, nematic as well as several smectic subphases can easily align macroscopically by rubbed surfaces, mechanical stimuli, and electric and magnetic fields. [37][38][39] Fluorescence via excited-state intramolecular proton transfer (ESIPT) provides strong light emission with a large Stokes shift and environment-sensitive unique spectral patterns. Particular systems including 2-(2-hydroxyphenyl) benzothiazole (HBT) serve as efficient solid-state emitters with the ESIPT mechanism and aggregation-induced emission enhancement (AIEE) property, but have not been used for liquid crystalline (LC) materials. Here, rod-shaped fluorescent LCs with ESIPT characters are newly developed based on the HBT motif. The design of the targeted mole...

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“…In this context, crystal packing and molecular arrangement have been recognized as important aspect fort he designo fi nnovative optical devices. [1][2][3][4][5][6][7][8][9][10] Most of these studies focusingo nc orrelations between crystal packing, polymorphism,a nd optical properties are foundw ithin the field of p-conjugated materials foro ptoelectronicd evices, that is, organic light-emitting diodes (OLEDs), organic thin-filmt ransistors, waveguides,r esonators or solar devices.A lternatively, photoluminescent lanthanide (Ln)-based molecules and materials are highly attractive candidates for opto-magnetic applications spanning the broad range from optical sensors, biomedical probesa nd contrast agents to waveguides, and single-molecule magnets, to name af ew. [11][12][13][14][15][16][17][18][19][20][21][22][23] While significant effect of crystal packing on the optical properties of Ln 3 + -based materials has been shown for coordi-nationp olymers and metal-organicframeworks (MOFs), surprisinglyt his has not yet been exploited in molecular species that exhibit polymorphism.…”

Section: Introductionmentioning

confidence: 99%

Probing Optical Anisotropy and Polymorph‐Dependent Photoluminescence in [Ln₂] Complexes by Hyperspectral Imaging on Single Crystals

Errulat

Gabidullin

Murugesu

et al. 2018

Chemistry A European J

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Two homodinuclear and one heterodinuclear lanthanide (Ln)-based complexes of the general formula [Ln (bpm)(tfaa) ] (Ln=Eu (1), Tb (2), Eu-Tb (3), bpm=2,2'-bipyrimidine, tfaa =1,1,1-trifluoroacetylacetonate) were synthesized and characterized by single-crystal photoluminescence spectroscopy and hyperspectral imaging. Complexes 1 and 2 crystallize in two polymorphic structures, while three polymorphs were isolated for 3, namely having needle-, plate-, and block-like morphologies. Single-crystal photoluminescence spectroscopy and imaging on Eu -containing 1 and 3 revealed polymorph-dependent J-splitting of the hypersensitive D → F Eu transition as well as electric-to-magnetic dipole emission intensity ratios. According to these observations, the lowest symmetry chemical environment was attributed to the Eu ions present in the needle-like polymorph, also in agreement with single-crystal X-ray diffraction analysis. More importantly, hyperspectral imaging on all three single-crystal polymorphs of 3 exhibits optical anisotropy with photoluminescence enhancement at specific crystallographic faces. This behavior was ascribed to the distinct molecular packing of the Ln-Ln dimers in each polymorphic crystal as well as to face-specific local symmetry of the Eu centers. Overall, opto-structural relationships of three Ln-Ln dimers and their single-crystal polymorphs were established as a particularly promising avenue for control of photoluminescence by chemical crystal engineering.

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Three-color polymorph-dependent luminescence: crystallographic analysis and theoretical study on excited-state intramolecular proton transfer (ESIPT) luminescence of cyano-substituted imidazo[1,2-a]pyridine

Cited by 62 publications

References 43 publications

Exploring Potential Energy Surfaces for Aggregation‐Induced Emission—From Solution to Crystal

Exploring Potential Energy Surfaces for Aggregation‐Induced Emission—From Solution to Crystal

Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Probing Optical Anisotropy and Polymorph‐Dependent Photoluminescence in [Ln₂] Complexes by Hyperspectral Imaging on Single Crystals

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Three-color polymorph-dependent luminescence: crystallographic analysis and theoretical study on excited-state intramolecular proton transfer (ESIPT) luminescence of cyano-substituted imidazo[1,2-a]pyridine

Cited by 62 publications

References 43 publications

Exploring Potential Energy Surfaces for Aggregation‐Induced Emission—From Solution to Crystal

Exploring Potential Energy Surfaces for Aggregation‐Induced Emission—From Solution to Crystal

Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Probing Optical Anisotropy and Polymorph‐Dependent Photoluminescence in [Ln2] Complexes by Hyperspectral Imaging on Single Crystals

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Probing Optical Anisotropy and Polymorph‐Dependent Photoluminescence in [Ln₂] Complexes by Hyperspectral Imaging on Single Crystals