Functional π-Gelators and Their Applications

Babu, Sukumaran Santhosh; Praveen, Vakayil K.; Ajayaghosh, Ayyappanpillai

doi:10.1021/cr400195e

Cited by 1,599 publications

(1,025 citation statements)

References 1,579 publications

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“…With respect to infinite graphene, PAHs show nonzero tunable bandgaps and are thus of use as chromophores in antennae7, 8, 9, 10, 11, 12 or emissive molecular architectures13, 14, 15, 16, 17, 18, 19 and in general in all optoelectronic applications requiring a tunable semiconducting material 6, 20. By exploiting organic synthetic tools,21, 22 one can tune the molecular HOMO–LUMO gap8 by 1) changing the size and edge of the carbon‐based aromatic framework; 2) varying the molecular planarity upon insertion of bulky substituents or bridging chains; 3) changing the aromatic properties of the constituent monomeric units; 4) varying the peripheral functionalization through the insertion of electron‐donating or electron‐ withdrawing substituents; 5) enclosing structural defects; 6) promoting supramolecular interactions between individual molecules governing their organization into a condensed phase, and 7) replacing selected carbon atoms by isostructural and isoelectronic analogues (i.e., doping).…”

Section: Introductionmentioning

confidence: 99%

Tailoring Colors by O Annulation of Polycyclic Aromatic Hydrocarbons

Miletić

Fermi

Orfanos

et al. 2017

Chemistry A European J

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The synthesis of O‐doped polyaromatic hydro‐ carbons in which two polycyclic aromatic hydrocarbon sub units are bridged through one or two O atoms has been achieved. This includes high‐yield ring‐closure key steps that, depending on the reaction conditions, result in the formation of furanyl or pyranopyranyl linkages through intramolecular C−O bond formation. Comprehensive photophysical measurements in solution showed that these compounds have exceptionally high emission yields and tunable absorption properties throughout the UV/Vis spectral region. Electrochemical investigations showed that in all cases O annulation increases the electron‐donor capabilities by raising the HOMO energy level, whereas the LUMO energy level is less affected. Moreover, third‐order nonlinear optical (NLO) measurements on solutions or thin films containing the dyes showed very good values of the second hyperpolarizability. Importantly, poly(methyl methacrylate) films containing the pyranopyranyl derivatives exhibited weak linear absorption and NLO absorption compared to the nonlinearity and NLO refraction, respectively, and thus revealed them to be exceptional organic materials for photonic devices.

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Section: Introductionmentioning

confidence: 99%

Tailoring Colors by O Annulation of Polycyclic Aromatic Hydrocarbons

Miletić

Fermi

Orfanos

et al. 2017

Chemistry A European J

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“…For example, the fiber formation is a result of molecular stacking, meaning that the self-assembly leads to aggregates that can be suitable for optoelectronic applications. 13,14 The ready reversibility of gelation can be exploited, for example, to release cells from gels on demand in a manner that does not lead to cell death. 15 Ready gel formation by a simple trigger can also be used to allow easy and efficient gel loading.…”

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confidence: 99%

Low-Molecular-Weight Gels: The State of the Art

Draper

Adams

2017

Chem

516

469

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Low-molecular-weight gels are currently a hugely important class of materials that are attracting significant interest. These gels are formed when small molecules self-assemble into one-dimensional structures that entangle and cross-link to form a network that is capable of immobilizing the solvent. Here, we critically discuss the current state of the art and highlight two key areas where we believe there is significant untapped potential. The first is the observation that the properties of the gels are highly process dependent, which means that it is possible to access materials with very different properties from a single gelator. Second, using multiple gelators offers the opportunity to prepare materials with a high degree of information content and with a wider range of properties. We aim to spark thought and discussion on these aspects. INTRODUCTIONLow-molecular-weight gels (LMWGs), or supramolecular gels, are a fascinating and useful class of material. The gels arise from the self-assembly of small molecules into long, anisotropic structures, most commonly fibers. [1][2][3][4][5] At a sufficiently high concentration, these fibers entangle or otherwise form cross-links, leading to the network that is able to immobilize the solvent through surface tension and capillary forces. 1,2 These gels differ from permanently covalently cross-linked polymer gels because the cross-linking can be reversed by the input of energy, for example, by heating. 6 LMWGs have been around for many years but are receiving considerable current interest. 4 They are also used in industrial products, 7 although this seems rarely discussed in the academic literature.In addition to the industrial applications, many recent advances and uses are being described. [8][9][10][11][12] The specific self-assembly leading to gel formation can be exploited. For example, the fiber formation is a result of molecular stacking, meaning that the self-assembly leads to aggregates that can be suitable for optoelectronic applications. 13,14 The ready reversibility of gelation can be exploited, for example, to release cells from gels on demand in a manner that does not lead to cell death. 15 Ready gel formation by a simple trigger can also be used to allow easy and efficient gel loading. [16][17][18] Unsurprisingly, therefore, there is significant interest in these materials ( Figure 1). This is a fascinating area and in many ways holds attention because of the difficulties in probing and understanding the gels. The gels arise from assembly across many length scales, and understanding all of these is difficult. At the molecular level, the molecules must interact in a manner that leads to the formation of suitable aggregates that can eventually entangle. Thus, one-dimensional growth must be favored. From this perspective, it is very frustrating that it is often extremely difficult to predict whether a molecule will form a gel or not; indeed, gelation has been described as an empirical science. 4 Structurally similar small molecules can exhibitThe Bigger Pict...

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“…[2][3][4][5][6][7] Several approaches have addressed the inclusion of photonic functionalities into supramolecular gels. 8 For example, gels with chromophore units have been used as photocatalysts 9,10 and excitation energy transfer has been studied in supramolecular gels formed by photoactive fibers which contained entrapped dyes. [11][12][13][14][15] Recently, we reported orthogonal fibrillization of two fluorescent supramolecular gelators.…”

Section: Introductionmentioning

confidence: 99%

“…8 For example, gels with chromophore units have been used as photocatalysts 9,10 and excitation energy transfer has been studied in supramolecular gels formed by photoactive fibers which contained entrapped dyes. [11][12][13][14][15] Recently, we reported orthogonal fibrillization of two fluorescent supramolecular gelators. 16 Additionally, supramolecular gels have been used as photon upconversion matrixes based on the triplet-triplet-annihilation mechanism via organic molecules.…”

Section: Introductionmentioning

confidence: 99%

Multimodal Light-Harvesting Soft Hybrid Materials: Assisted Energy Transfer upon Thermally Reversible Gelation

et al. 2017

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Multimodal light-harvesting soft systems able to absorb UV-to-NIR radiations and convert into visible emissions have drawn much attention in the last years in order to explore new areas of application in energy, photonics, photocatalysis, sensors and so forth. Here, we present a new hybrid system combining a supramolecular photonic gel of naphthalimide-derived molecules self-assembled into fibers and upconverting NaYF 4 :Yb/Tm nanoparticles (UCNPs). The hybrid system presented here manipulates light reversibly as a result of an optical communication between the UCNPs and the photoactive gel network. Upon UV irradiation, the system shows the characteristic emission at 410 nm from the photoactive organomolecule. This emission is also activated upon 980 nm excitation thanks to an efficient energy transfer from the UCNPs to the fibrillary network. Interestingly, the intensity of this emission is thermally regulated during the reversible assembly or disassembly of the organogelator molecules, in such a way that gelator emission is only observed in the aggregated state. Additionally, the adsorption of the UCNPs with the supramolecular gel fibers enhance their emissive properties, a behavior ascribed to the isolation from solvent quenchers and surface defects, as well as an increased IR light scattering promoted by the fibrillary network. The reported system constitutes a unique case of a thermally regulated, reversible, dual UV and IR light harvesting hybrid soft material.3

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Functional π-Gelators and Their Applications

Cited by 1,599 publications

References 1,579 publications

Tailoring Colors by O Annulation of Polycyclic Aromatic Hydrocarbons

Tailoring Colors by O Annulation of Polycyclic Aromatic Hydrocarbons

Low-Molecular-Weight Gels: The State of the Art

Multimodal Light-Harvesting Soft Hybrid Materials: Assisted Energy Transfer upon Thermally Reversible Gelation

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