D-π-D chromophores based on dithieno[3,2-b:2',3'-d]thiophene (DTT): Potential application in the fabrication of solar cell

© 2016 Elsevier LtdIn this work, four stable dithieno[3,2-b:2',3'-d]thiophene-based π-extended molecules were designed and synthesized via a Pd-catalysed Sonogashira coupling reaction. The structures of these symmetrical compounds, including dithieno[3,2-b:2',3'-d]thiophene (DTT) as the π-center and various donor (D) groups, were determined on the basis of NMR spectral data, elemental analysis, and X-ray crystallography. The photo-physical properties of the DTT-based derivatives 2 were fully investigated in both solution and the solid state. The notable optical features of their solid-state powders showed significant red-shifts in comparison with the luminescence of their dilute dichloromethane solutions. These results combined with the theoretical calculations indicate that they are promising candidates for several applications in electronic and optoelectronic devices, as well as organic dyes for solar cells

Extended [pi]-conjugated pyrene derivatives: structural, photophysical and electrochemical properties

This article presents a set of extended [pi]-conjugated pyrene derivatives, namely 1,3-di(arylethynyl)-7-tert-butylpyrenes, which were synthesized by a Pd-catalyzed Sonogashira coupling reaction of 1,3-dibromo-7-tert-butylpyrenes with the corresponding arylethynyl group in good yields. Despite the presence of the tert-butyl group located at the 7-position of pyrene, X-ray crystallographic analyses show that the planarity of the Y-shaped molecules still exhibits strong face-to-face [pi]-[pi] stacking in the solid state; all of the compounds exhibit blue or green emission with high quantum yields (QYs) in dichloromethane. DFT calculations and electrochemistry revealed that this category of compound possesses hole-transporting characteristics. In addition, with strong electron-donating (-N(CH3)2) or electron-withdrawing (-CHO) groups in 2 d or 2 f, these molecules displayed efficient intramolecular charge-transfer (ICT) emissions with solvatochromic shifts from blue to yellow (green) on increasing the solvent polarity. Furthermore, the compounds 2 d and 2 f possess strong CT characteristics

Multiple photoluminescence from pyrene-fused hexaarylbenzenes with aggregation enhanced emission features

Multiple photoluminescence, involved in monomer emission, excimer emission and charge transfer emission origin from new pyrene-fused hexaarylbenzenes (HAB) compounds were observed, which were designed and synthesized (in high yield) via the Diels-Alder reaction of bis(2-tert-butylpyren-6-yl)acetylene and tetraphenylcyclopentadienone. Although the distinction of between two molecules arises only from the geometrical position of one of the pyrenes, the NMR spectra, the crystal packing and the physicochemical properties of these pyrene-based HAB hybrids are distinctly different both in their solution state and in aggregation-state. The X-ray diffraction analysis clearly indicated that the pyrene moieties in this system would form different crystal packing in crystal state that can induce a fantastic multiple photoluminescence phenomenon

Le Naturaliste Vendéen, Numéro 2 (2002)

The development of functionalized, luminescent, pyrene-based monomers has been and continues to be an area of great interest in terms of the design and fabrication of optical and electronic devices. Herein, a facile strategy to tune the emission color of pyrene-based chromophores has been established by simple functional group modification at the <i>para</i> position to the diphenylamino on the donor building block. Intriguing photophysical properties were obtained and are described both in different solutions and in the solid state. The results obtained could be explained by the Hammett method and by density functional theory (DFT) calculations. A good correlation was observed between the Hammett σ_para constants of the functional groups <i>para</i> to the phenyl and the wavenumber (cm^–1) of the emission profile. This positive correlation, namely between the σ constants of the functional groups and the emission properties of the monomers, can be used to develop a predictive method for these types of systems

Pyrene-based asymmetric hexaarylbenzene derivatives: Synthesis, crystal structures, and photophysical properties

Hexaarylbenzenes (HAB) and their derivatives have attracted considerable attention due to their fantastic molecular geometry and various applications in materials science. Herein, a set of novel, pyrene-based, asymmetric hexaarylbenzene molecules 3a–c and 10 were synthesized and fully characterized by using 1H/13C NMR, single crystal X-ray diffraction, high-resolution mass spectra (HRMS), UV–Vis and fluorescence spectroscopy, as well as density functional theory (DFT) calculations. The compounds show tunable-emission color from violet (366 nm) to deep blue emission (407 nm) following the order of 10 3b > 3a > 10 > hexaphenylbenzene (HPB), the asymmetric hexaarylbenzenes exhibited clearer aggregation-induced emission characterestics. In addition, DFT calculations indicated that there is strong electronic communication between the pyrene unit and the neighboring phenyl rings by a through-space charge-transfer process, which would play a curial role in lowering the quantum yield in the molecular aggregation state. Thus, this article provides an efficient synthetic strategy on how to design and synthesise high-performance pyrene-based hexaarylbenzene derivatives with narrow FWHM bands for potential applications in organic electronics

Allosteric binding properties of a 1,3-alternate thiacalix[4]arene-based receptor having phenylthiourea and 2-pyridylmethyl moieties on opposite faces

The synthesis of three new heteroditopic receptors (5a–c) which are based on thiacalix[4]arenes in the 1,3-alternate conformation are reported herein. These new receptors each have two thiourea moieties linking phenyl groups two of which are substituted with electron-withdrawing groups at their para-positions, and at the opposite side of the thiacalix[4]arene cavity, with two 2-pyridylmethyl groups. One example (5a) was also characterized by X-ray crystallography. A limited 1H-NMR and Uv-vis anion complexation study was conducted. DFT computational determinations indicated that 5c which has the strong electron–withdrawing NO2 groups had the most effective recognition ability towards the selected anions. The binding of Ag + at the 2-pyridyl moieties and the binding of the anions at the two thiourea NH groups of the p-substituted phenylthioureido moieties, respectively, was also investigated. The appearance of a positive allosteric effect with receptor 5b was also found using 1H-NMR titration experiments.</div

Direct syntheses of a series of cucurbit[<i>n</i>]uril-anchored polyacrylamides

<div><p>Using the one-pot, direct strategy reported by Su and co-workers, we have synthesised a series of cucurbit[<i>n</i>]urils (Q[<i>n</i>], <i>n</i> = 5–8) and alkyl-substituted cucurbit[6]urils (SQ[6]s) anchored on polymers. Acrylamide, as a typical monomer, was used to synthesise a series of Q[<i>n</i>]s (<i>n</i> = 5–8) and SQ[6]-anchored polyacrylamides (PAMs) using a persulfate salt as initiator and oxidant. The Q[<i>n</i>]s (<i>n</i> = 5–8) and SQ[6]-anchored PAM samples have been characterised by ¹H NMR, ¹H NMR titrations of probe guests, Fourier-transform infrared and thermogravimetric analyser. The results confirmed that PAM chains had been successfully grafted on the back of the Q[<i>n</i>]s (<i>n</i> = 5–8) and SQ[6]s through an <i>in situ</i> radical polymerisation approach. It was further confirmed that the hydrophobic cavities of the Q[<i>n</i>]s on the polymers were still freely accessible. This synthetic approach may be extended to a variety of Q[<i>n</i>]s that are difficult to functionalise.</p></div

Crystallization-induced emission enhancement of alkyl chain-dependent pyrene-based luminogens: Visual detection of nitro-explosives

In view of the widespread applications and urgent need for efficient blue emitting materials, the synthesis of such materials has seen renewed interest. In the present work, three alkyl chain-dependent blue emitting pyrene-based luminogens were synthesized and characterized. The experimental results show that these luminogens exhibited high photoluminescence efficiency both in solution (> 86%) and in the solid state (> 35%). Interestingly, 1,3,6,8-tetrakis(pentylphenyl)pyrene (TPPy), as a photoelectric functional material, was endowed with higher quantum yield (72%) and competitiveness due to a remarkable crystallization-induced emission enhancement (CIEE) property. More importantly, TPPy exhibits high sensitivity and selectivity for ortho-nitroaniline (o-NA) with low limit of detection (9.99 × 10–8 M), which is mainly due to the distinctive odd-even effects of the terminal alkyl chain. The results demonstrate that this type of luminogen can potentially be utilized for practical applications in the field of contaminant or explosive detection as a sensitive and portable fluorimeter.</p

Pyrene-fused hexaarylbenzene luminogens: Synthesis, characterization, and aggregation-induced emission enhancement

Six novel pyrene-fused hexaarylbenzene derivatives (3a-f) were designed, synthesized, and characterized, which exhibited aggregation-induced emission enhancement (AIEE) in the aggregated state by means of THF/H2O mixtures. Techniques such as theoretical calculations, single crystal X-ray diffraction, and photophysical measurements in solution and in the solid state were employed to illustrate the tunable, variable, and sensitive AIEE features in this system. Both theoretical and experimental results revealed that the nature of the multiple photoluminescence should be taken into account when elucidating and designing the multiple photoluminescence phenomenon and molecules

A Hemimethyl-Substituted Cucurbit[7]uril Derived from 3α-Methyl-glycoluril

A novel hemimethyl-substituted cucurbit[7]­uril (HMeQ[7]) derived from 3α-methyl-glycoluril has been prepared. HMeQ[7] is readily soluble in both water and dimethyl sulfoxide (DMSO) and displays not only host–guest interaction properties similar to those of the normal cucurbit[7]­uril but also unusual properties in DMSO