Effect of Alkyl Groups in Pyrene Chromophore on the Mechanical Response of Pyrene‐Octafluoronaphthalene Co‐Crystals

Changes in the photophysical properties of pyrene ( Py )‐octafluoronaphthalene ( OFN ) co‐crystals ( Py ? OFN ) upon mechanical stimuli are described herein. The Py ? OFN co‐crystal showed a mechano‐induced bathochromic shift in emission, and a similar tendency was observed for the 1,3,6,8‐tetramethylpyrene‐ OFN co‐crystal. These shifts are due to disruption of the microscopic molecular orientation in the co‐crystal, which allows for excimer formation. In sharp contrast to the parent Py ? OFN and methyl‐substituted Py ‐ OFN co‐crystals, no mechano‐induced bathochromic shift was observed when longer alkyl chains were introduced to the 1‐, 3‐, 6‐, and 8‐positions of the Py chromophore. This photophysical opposability against mechanical stimuli could be explained by the orthogonally oriented alkyl groups on the Py ring, which existed between two Py cores like pillars. This fixed OFN to maintain the face‐to‐face alternatively stacked structure of the co‐crystal and thus prevented the formation of the Py excimer. The pillar effect demonstrated herein provides a rational design for co‐crystalline systems that are photophysically stable against mechanical stresses.     

N-Acenoacenes: Synthesis and Solid-State Properties

Four N-acenoacenes were synthesized and analyzed for their optoelectronic properties and solid-state packings. Two of the regioisomeric acridinoacridines are TIPS-ethynylated, whereas the other pair are Boc- and triflate substituted derivatives. The two TIPS-ethynyldiazaacenoacenes were processed into organic thin-film transistors with saturation hole mobilities reaching 2.9×10⁻² cm²(Vs)⁻¹.     

Synthesis,Crystal Structure and Photophysical Properties of Pyrene–Helicene Hybrids

Synthesis of helically chiral aromatics resulting from fusion of pyrene and [4]‐ or [5]helicene has been accomplished using photoredox catalysis employing a Cu‐based sensitizer as the key step. Photocyclisation experiments for the synthesis of the target compounds were carried out in batch and using continuous flow strategies. The solid‐state structures, UV/Vis absorption spectra and fluorescence spectra of the pyrene–helicene hybrids were investigated and compared to that of the parent [5]helicene to discern the effects of merging a pyrene moiety within a helicene skeleton. The studies demonstrated that pyrene–helicene hybrids adopt co‐planar or stacked arrangements in the solid state, in contrast to the solid‐state structure of the parent [5]helicene. The UV/Vis and fluorescence spectra of the pyrene–helicene hybrids exhibited strong red‐shifts when compared to the parent [5]helicene. DFT calculations suggest that the strategy of extending the π surface in the y axis of the helicenes increased their HOMO levels while also decreasing their LUMO levels, resulting in significantly reduced band gaps.     

Systematic Investigation of Molecular Arrangements and Solid‐State Fluorescence Properties on Salts of Anthracene‐2,6‐disulfonic Acid with Aliphatic Primary Amines

Organic salts of anthracene‐2,6‐disulfonic acid (ADS) with a wide variety of primary amines have been fabricated, and their arrangements of anthracene molecules and solid‐state fluorescence properties investigated. Single‐crystal X‐ray studies reveal that the salts show seven types of crystal forms and corresponding molecular arrangements of anthracene moieties depending on the amine, while anthracene shows only one form and arrangement in the solid state. Depending on the molecular arrangements, the ADS salts exhibit various solid‐state fluorescence properties: spectral shift (30 nm) and suppression and enhancement of the fluorescence intensity. Especially the ADS salt with n‐heptylamine (nHepA), which shows discrete anthracene moieties in the crystal, exhibits the highest quantum yield (Φ_F=46.1±0.2 %) in the series of ADS salts, which exceeds that of anthracene crystal (Φ_F=42.9±0.2 %). From these systematic investigations on the arrangements and the solid‐state properties, the following factors are essential for high fluorescence quantum yield in the solid state: prevention of contact between π planes of anthracene moieties and immobilization of anthracene rings. In addition, such organic salts have potential as a system for modulating the molecular arrangements of fluorophores and the concomitant solid‐state properties. Thus, systematic investigation of this system constructs a library of arrangements and properties, and the library leads to remarkable strategies for the development of organic solid materials.     

Micro‐Scale Device—An Alternative Route for Studying the Intrinsic Properties of Solid‐State Materials: The Case of Semiconducting TaGeIr

An efficient application of a material is only possible if we know its physical and chemical properties, which is frequently obstructed by the presence of micro‐ or macroscopic inclusions of secondary phases. While sometimes a sophisticated synthesis route can address this issue, often obtaining pure material is not possible. One example is TaGeIr, which has highly sample‐dependent properties resulting from the presence of several impurity phases, which influence electronic transport in the material. The effect of these minority phases was avoided by manufacturing, with the help of focused‐ion‐beam, a μm‐scale device containing only one phase—TaGeIr. This work provides evidence for intrinsic semiconducting behavior of TaGeIr and serves as an example of selective single‐domain device manufacturing. This approach gives a unique access to the properties of compounds that cannot be synthesized in single‐phase form, sparing costly and time‐consuming synthesis efforts.     

基于1,8-萘啶双硼核化合物的合成、结构及光谱性质研究

设计合成了基于萘啶类衍生物1,2-二(7-氯-1,8-萘啶-2)-肼(H₂L)及其双硼核化合物 C1. H₂L的光谱性质具有明显的溶剂效应,它的发光很弱,而 C1的发光很强,荧光量子产率超过90%. H₂L在甲醇中不稳定,其相应的光谱特征蓝移到萘啶的特征峰,但金属离子Hg²⁺和Zn²⁺的引入能够恢复 H₂L的特征峰.通过溶剂挥发的方法得到了 C1的单晶.结构研究表明,在其晶胞中分子间通过C3-H3…F1和C3-H3…F2氢键作用形成三维网格结构.     

2- and 2,7-Substituted para-N-Methylpyridinium Pyrenes: Syntheses,Molecular and Electronic Structures,Photophysical, Electrochemical,and Spectroelectrochemical Properties and Binding to Double-Stranded (ds) DNA

Two N-methylpyridinium compounds and analogous N-protonated salts of 2- and 2,7-substituted 4-pyridyl-pyrene compounds were synthesised and their crystal structures, photophysical properties both in solution and in the solid state, electrochemical and spectroelectrochemical properties were studied. Upon methylation or protonation, the emission maxima are significantly bathochromically shifted compared to the neutral compounds, although the absorption maxima remain almost unchanged. As a result, the cationic compounds show very large apparent Stokes shifts of up to 7200 cm⁻¹. The N-methylpyridinium compounds have a single reduction at ca. −1.5 V vs. Fc/Fc⁺ in MeCN. While the reduction process was reversible for the 2,7-disubstituted compound, it was irreversible for the mono-substituted one. Experimental findings are complemented by DFT and TD-DFT calculations. Furthermore, the N-methylpyridinium compounds show strong interactions with calf thymus (ct)-DNA, presumably by intercalation, which paves the way for further applications of these multi-functional compounds as potential DNA-bioactive agents.     

固态荧光碳点的制备

荧光碳点由于其具有无毒、制备成本低以及独特的光致发光性能而引起人们极大的研究兴趣,但是通常碳点的制备和使用均是在溶液中,而且随着碳点浓度的增加其荧光强度可能会降低甚至猝灭,通过简单干燥后得到的固态粉末则常常缺少荧光性质。因此,固态荧光碳点制备及其相关应用的研究相对较少。本文综述了固态荧光碳点的制备方法,包括后处理法(基质分散法、表面工程法)和前驱体直接合成法;对比了各种调控手段处理前后碳点荧光性能的变化情况,总结了各种固态碳点在制备过程中和使用过程中存在的主要问题。最后,针对固态发光碳点的制备方法、性能调控及发展方向进行了展望。开发具有聚集诱导发射增强的碳点是至关重要的,也为固态碳点的发展提供了新思路。     

Hydrothermal Synthesis,Crystal Structure,Thermal Stability and Photophysical Property of a Novel Zinc Complex with Mixed Ligands

A novel metal-organic coordination complex [Zn(CHIP)(AIC)]n(1, CHIP = 2-(4-chlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, AIC = 5-amino-isophthalic acid) has been synthesized by hydrothermal reactions and characterized by elemental analysis, thermogravimetric(TG) analysis, infrared spectrum(IR) and single-crystal X-ray diffraction. Complex 1 crystallizes in monoclinic, space group C2/c with a = 18.259(5), b = 17.191(4), c = 16.371(4) A, V = 4717(2) A3,C27H-116 ClN 5O4Zn, Mr = 575.29, Dc = 1.620 g/cm3, μ(Mo Kα) = 1.202 mm, F(000) = 2335, Z = 8, the final R = 0.032 and w R = 0.074 for 4723 observed reflections(I 2σ(I)). Single-crystal X-ray diffraction reveals that 1 exhibits one-dimensional(1D) double chains, which are linked by H-bond intersections into a 2D structure. TG analysis shows clear weight loss due to the decomposition of different ligands. The luminescent properties for the ligand and complex 1 were also studied.     

Thermotropic Properties and Molecular Packing of Discotic Tristriazolotriazines with Rigid Substituents

Tristriazolotriazines with a threefold dialkoxyaryl substitution have been prepared by Huisgen reaction of cyanuric chloride and the corresponding tetrazoles. Although these dyes show a negative or inverted solvatochromism of the UV/Vis absorption, their fluorescence is strongly positive solvatochromic. These discotic fluorophores are also emissive in their solid state and in their broad liquid‐crystalline mesophase. The structural study indicates that the thermotropic properties and organization of these systems can be well tuned by the steric demand of the aryl groups. Depending on the substituents, the compounds showed either a pure crystalline phase or a highly complex helical superstructure with a characteristic liquid‐crystalline phase at elevated temperatures. Changing the steric demand of the attached aryls allowed controlling the discs arrangement within the columnar helix, which is of great importance for the molecular orbital overlap.     

1,3,6,8-Tetraethynylpyrene and 1,3,6,8-tetrakis (trimethylsilylethynyl) pyrene: Photophysical properties in homogeneous media

The photophysical properties of two new tetra substituted derivatives of pyrene: 1,3,6,8-tetraethynylpyrene (TEP) and 1,3,6,8-tetrakis(trimethylsilylethynyl)pyrene (TEP-TMS) have been studied. Studies were done with respect to mirror image symmetry in the absorption and emission spectra and permissive or forbidden nature of S₀–S₁ transition, solvent sensitivity of the first and third vibronic bands and fluorescence anisotropy. Both the derivatives exhibited a strongly allowed S₀–S₁ transition, high fluorescence quantum yield, shorter fluorescence lifetime compared to pyrene and invariance of the vibronic band intensity ratio to solvent polarity. The behavior of the two pyrene derivatives validates the hypothesis “solvent polarity mediates vibronic coupling and therefore the emission band intensities, for forbidden S₀–S₁ transitions”. The trimethylsilyl derivative (TEP-TMS) was characterized by a strong fluorescence in solid state. The tetraethynyl derivative (TEP) showed high fluorescence anisotropy comparable to the well-known anisotropy probe DPH in glycerol at 0 °C. The fluorescence intensities of TEP and TEP-TMS did not show any significant change in the temperature ranger 0–40 °C for a low viscous solvent like ethanol and in the range 0–60 °C in glycerol. Unlike pyrene, no excimer emission was observed even up to 10⁻³ M for TEP and TEP-TMS.     

Double Chalcogen Bonds: Crystal Engineering Stratagems via Diffraction and Multinuclear Solid-State Magnetic Resonance Spectroscopy

Group 16 chalcogens potentially provide Lewis-acidic σ-holes, which are able to form attractive supramolecular interactions with electron rich partners through chalcogen bonds. Here, a multifaceted experimental and computational study of a large series of novel chalcogen-bonded cocrystals, prepared using the principles of crystal engineering, is presented. Single-crystal X-ray diffraction studies reveal that dicyanoselenadiazole and dicyanotelluradiazole derivatives work as promising supramolecular synthons with the ability to form double chalcogen bonds with a wide range of electron donors including halides and oxygen- and nitrogen-containing heterocycles. Extensive ⁷⁷Se and ¹²⁵Te solid-state nuclear magnetic resonance spectroscopic investigations of cocrystals establish correlations between the NMR parameters of selenium and tellurium and the local chalcogen bonding geometry. The relationships between the electronic environment of the chalcogen bond and the ⁷⁷Se and ¹²⁵Te chemical shift tensors were elucidated through a natural localized molecular orbital density functional theory analysis. This systematic study of chalcogen-bond-based crystal engineering lays the foundations for the preparation of the various multicomponent systems and establishes solid-state NMR protocols to detect these interactions in powdered materials.     

A Novel Pyrene‐Based Fluorescing Amphiphile with Unusual Bulk and Interfacial Properties

We have synthesised a new, pyrene‐based, low‐molecular‐mass, amphiphilic molecule that displays a wealth of properties of potential interest for aggregation and interfacial applications. In order to elucidate some of the key properties of this molecule, which consists of a pyrene‐containing hydrophobic head and a short PEG‐based hydrophilic tail, we investigate herein some aspects of its concentration‐dependent behaviour in aqueous solutions. We show that the inclusion of the hydrophobic pyrene group not only provides the molecule with intriguing bulk and interfacial properties down to low concentrations, but also with various means of assessing its aggregation behaviour by means of its well‐characterised fluorescence properties. Combining a range of fluorescence techniques with microscopic imaging (optical and Cryo‐TEM), interfacial tension measurements and foaming studies, we have been able to identify and characterise three concentration‐dependant regimes. At low concentrations, the molecule is dissolved in monomeric form. At intermediate concentrations, labile aggregates are formed, which, at higher concentrations, give way to aggregates containing pre‐associated pyrenes. Our measurements strongly imply that the latter aggregates are hexagonally close‐packed tubular micelles. In this latter regime we also find a range of micron‐sized precipitates. Additionally, the molecule displays strong interfacial activity, yet a surprisingly slow dynamics of interfacial adsorption. Finally, we demonstrate the possibility of using it to visualize interfaces and also create reasonably stable (1 hour) and fluorescing foams.     

化合物[2，6-bis(benzo[1，2-d：4，5-d′]diimidazole-2′-yl)pyridine]的合成、晶体结构和光物理性质(英)

A new tridentate benzimidazole derivative, 2,6-bis (benzo[1,2-d:4,5-d′]diimidazole-2′-yl) -pyridine (Bzdiimpy), was prepared from o-phenylenediamine in five steps with improved methods according to the literature in good yield. The crystal structure was determined by X-ray diffraction analysis. It crystallized in monoclinic, space group P2₁/c, with a=1.170 8(4) nm, b=2.479 6(9) nm, c=1.215 9(4) nm, β=114.641(7)°, Z=1, R=0.035 0, wR₂=0.089 0. The bzdiimp molecule displayed an almost planar structure and formed a zig-zag chain through weak interactions between imidazole-N and [SnCl₆]^2--Cl. Its electronic absorption and emission spectra were measured and compared with the reported analogue 2,6-bis (benz[1,2-d:4,5-d′]imidazole-2′-yl)-pyridine (Bzp). CCDC: 239203.     

Base-Assisted Imidization: A Synthetic Method for the Introduction of Bulky Imide Substituents to Control Packing and Optical Properties of Naphthalene and Perylene Imides

We report the direct imidization of naphthalene and perylene dicarboxylic anhydrides/esters with bulky ortho,ortho-diaryl- and ortho,ortho-dialkynylaniline derivatives. This imidization method uses n-butyllithium as a strong base to increase the reactivity of bulky amine derivatives, proceeds under mild reaction conditions, requires only stoichiometric amounts of reactants and gives straightforward access to new sterically crowded rylene dicarboximides. Mechanistic investigations suggest an isoimide as intermediary product, which was converted to the corresponding imide upon addition of an aqueous base. Single-crystal X-ray diffraction analyses reveal dimeric packing motifs for monoimides, while two-side shielded bisimides crystallize in isolated molecules without close π–π-interactions. Spectroscopic investigations disclose the influence of the bulky substituents on the optical properties in the solid state.     

化合物[2,6-bis(benzo[1,2-d:4,5-d′]diimidazole-2′-yl)pyridine] 的合成、晶体结构和光物理性质

A new tridentate benzimidazole derivative, 2,6-bis (benzo[1,2-d:4,5-d′]diimidazole-2′-yl) -pyridine (Bzdiimpy),was prepared from o-phenylenediamine in five steps with improved methods according to the literature in good yield.The crystal structure was determined by X-ray diffraction analysis. It crystallized in monoclinic, space group P21/c,with a=1.1708(4) nm, b=2.4796(9) nm, c=1.215 9(4) nm,β=114.641(7)°, Z=1, R=0.035 0, wR2=0.0890. The bzdiimp molecule displayed an almost planar structure and formed a zig-zag chain through weak interactions between imidazole-N and [SnCl6]2--Cl. Its electronic absorption and emission spectra were measured and compared with the reported analogue 2,6-bis (benz[1,2-d:4,5-d′]imidazole-2′-yl)-pyridine (Bzp).