Molecular assembly of dithiaparacyclophanes mediated by non-covalent X…X, X…Y and C–H…X (X, Y=Br, S, N) interactions

Xu, Jianwei; Wang, Weiling; Lin, Tingting; Sun, Zhe; Lai, Yongqing

doi:10.1080/10610270701787723

Cited by 313 publications

(433 citation statements)

References 55 publications

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“…Nevertheless, the fluorescence longer lifetimes especially for MEH-PPV films cast are longer than usually expected. Monkman et al 74 generated triplet states in MEH-PPV of 1.5 eV via pulse radiolysis, while Sinclair et al 75 accessed the triples states with photons of high energy with adequate "pump intensity" and Xu et al 70 accessed high energy vibronic states of MEH-PPV by high voltage bias application, and observed fluorescence at 390-430 nm, corroborating with our measurements. The fact that triplet excited states can be accessed in MEH-PPV allows for the occurrence of several unimolecular processes, for instance, singlet exciton fission.…”

Section: Fluorescence Of Thin Films and Blendssupporting

confidence: 77%

“…55 Indeed, several works have proved the existence of triplet excitons in conjugated polymers and, to our interest, in MEH-PPV. 18,69,70 In a previous work of Hale et al, 18 triplet states of PPV conjugated polymers were accessed by two-photon emission experiments and insights into the nature of triplet exciton relaxation processes were achieved by a rate equation approach developed by Halas and co-workers. 71 The significantly distinct emission spectra obtained for films and solutions produced in acetonitrile and ethanol can be understood as the thermally activated delayed fluorescence (TADF), which is expected to provide fluorescence (hot excitons emission) from the triplet-triplet annihilation (TTA) of two colliding triplets.…”

Section: Fluorescence Of Thin Films and Blendsmentioning

confidence: 99%

mentioning

confidence: 99%

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Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Ribeiro¹,

Camargo²,

Pereira³

et al. 2017

J. Braz. Chem. Soc.

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In this work, we examined how photoluminescence in poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is affected by morphology, dictated by the mode of preparation. For that, MEH-PPV dilute solutions in good and non-solvents, thick cast films with poly[methylmethacrylate] (PMMA) as inert matrix and spin-coated thin films were prepared. These systems were studied by steady-state and time-dependent fluorescence spectroscopy and electronic microscopy. Unexpected photoluminescent behavior was detected in solutions and films and it was related to different excitons modulated by MEH-PPV conformation. By semi empirical calculations we obtained the singlet and triplet state energies of an MEH-PPV model system and, from time-resolved fluorescence spectroscopy, the existence of short-lived excited states was revealed, enabling us to infer on possible singlet fission in MEH-PPV-based systems.Keywords: photoluminescence, morphology, thin films, time-resolved fluorescence, computational calculations IntroductionSince poly(phenylene-vinylene) (PPV) derivatives were found to be electroluminescent, 1 the search for a systematic method to determine their applications has been of great interest. Their mechanical, morphological and optical properties have been widely discussed and findings related these properties to preparation methods. Although there are many aspects regarding the effects of preparation methods on optical response, authors seem to agree that preparation method influences molecular conformation, enabling or inhibiting aggregation and, consequently, affecting inter and intrachain interactions. Processing parameters are believed to modify the conformation and assembling mechanisms of polymeric materials, resulting in a memory effect of the structural information that is replicated from solutions to solid films. Therefore, to understand the role of chain conformation in solution is of major importance for applications such as device fabrication, since properties can be tuned, enhancing the desired characteristics and suppressing the undesired ones. 2,3 For instance, it is well known that photoluminescence of PPV derivatives show prominent red-shift due to the enhancement of energy transfer as the π-electron delocalization increases. 4 As pointed out in an earlier work, 5 this red-shift indicates aggregation driven by π-π interactions as the conjugation length increases.In polymeric systems, several occurrences are responsible for chain torsions that impose limits to the length of conjugated segments, affecting the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps. They are interpreted as stabilization and/or destabilization of HOMO and LUMO levels. 6 These occurrences may be related to the presence of impurities, molecules of solvent that strongly interact with the polymer chains and a distribution of torsion angles promoted by molecular interactions of any nature. 6 In this situation, the densities of excited states (DOS) available for electronic chan...

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Section: Fluorescence Of Thin Films and Blendssupporting

confidence: 77%

Section: Fluorescence Of Thin Films and Blendsmentioning

confidence: 99%

mentioning

confidence: 99%

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Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Ribeiro¹,

Camargo²,

Pereira³

et al. 2017

J. Braz. Chem. Soc.

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“…118 The Taiwanese soft coral S. manaarensis contained four cembrane-type diterpenoids, manaarenolides A 209 and B 210 and manaarenolides E 211 and F 212, which were discovered for the first time as the hydroperoxycembranolides possessing a δ-lactone ring. 123 The same source, S. crassocaule, provided three further cembranoid sarcocrassocolides F 227, G 228, and J 229, all of which inhibited LPS-induced upregulation of the pro-inammatory protein iNOS. 124 A chemical investigation of another species of the same genus, S. Glaucum, has led to the isolation of two peroxide diterpenes 230 and 231, the absolute configuration of which were confirmed by X-ray diffraction and circular dichroism (CD) analyses.…”

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confidence: 99%

Peroxy natural products

Liu

2013

Nat. Prod. Bioprospect.

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“…The same trend is found at other wavelengths. Substitution of deuterium to hydrogen has changed the lattice parameter 17 and space composition especially along the (100) axis, which attribute to that the orientation of hydrogen bond is along (100) axis (perpendicular to the optical axis). In our opinion that is the reason why refractive index changes.…”

Section: B Sellmeier Equationsmentioning

confidence: 99%

Refractive indices in the whole transmission range of partially deuterated KDP crystals

Zhu

Zhang

et al. 2013

AIP Advances

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Refractive indices of partially deuterated potassium dihydrogen phosphate (DKDP) crystals with 55%, 70% and 80% deuterium contents were measured by auto-collimation method at 293 K between 0.254 to 1.529 μm. Dependence of refractive indices of DKDP on deuterium content show different trend in the infrared region as in uv-visible region. Dependence of n2 (the square of refractive index) on the mole fraction of deuterium shows a difference between pure KDP and partially deuterated KDP. The Sellmeier equations were obtained by the least square method. The non-critical phase matching angles calculated from the fitted formula were in good agreement with laser experiment results, by which the reliability of these Sellmeier equations was confirmed.

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Molecular assembly of dithiaparacyclophanes mediated by non-covalent X…X, X…Y and C–H…X (X, Y=Br, S, N) interactions

Cited by 313 publications

References 55 publications

Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Peroxy natural products

Refractive indices in the whole transmission range of partially deuterated KDP crystals

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