Molecular Rotors of Coronene in Charge‐Transfer Solids

Ten types of neutral charge transfer (CT) complexes of coronene (electron donor; D) were obtained with various electron acceptors (A). In addition to the reported 7,7,8,8‐tetracyanoquinodimethane (TCNQ) complex of 1:1 stoichiometry with a DA‐type alternating π column, TCNQ also afforded a 3:1 complex, in which a face‐to‐face dimer of parallel coronenes ( Cor‐A s) is sandwiched between TCNQs to construct a DDA‐type alternating π column flanked by another coronene ( Cor‐B ). Whereas solid‐state ²H NMR spectra of the 1:1 TCNQ complex formed with deuterated coronene confirmed the single in‐plane 6‐fold flipping motion of the coronenes, two unsynchronized motions were confirmed for the 3:1 TCNQ complex, which is consistent with a crystallographic study. Neutral [Ni(mnt)₂] (mnt: maleonitriledithiolate) as an electron acceptor afforded a 5:2 complex with a DDA‐type alternating π column flanked by another coronene, similar to the 3:1 TCNQ complex. The fact that the Cor‐A s in the [Ni(mnt)₂] complex arrange in a non‐parallel fashion must cause the fast in‐plane rotation of Cor‐A relative to that of Cor‐B . This is in sharp contrast to the 3:1 TCNQ complex, in which the dimer of parallel Cor‐A s shows inter‐column interactions with neighboring Cor‐A s. The solid‐state ¹H NMR signal of the [Ni(mnt)₂] complex suddenly broadens at temperatures below approximately 60 K, indicating that the in‐plane rotation of the coronenes undergoes down to approximately 60 K; the rotational rate reaches the gigahertz regime at room temperature. Rotational barriers of these CT complexes, as estimated from variable‐temperature spin–lattice relaxation time (T₁) experiments, are significantly lower than that of pristine coronene. The investigated structure–property relationships indicate that the complexation not only facilitates the molecular rotation of coronenes but also provides a new solid‐state rotor system that involves unsynchronized plural rotators.     

Solid-State Emission and Aggregate Emission of Aroyl- S,N-Ketene Acetals Are Controlled and Tuned by Their Substitution Pattern

Aroyl-S,N-ketene acetals are a novel highly diverse class of aggregation-induced emission fluorogens (AIEgens) with a plethora of interesting properties. An expanded compound library of more than 110 dyes set the stage for the first qualitative control and tuneability of all aspects of their photophysical properties. The interplay of substituents not only allows tuning and prediction of the emission color, but also of the intensity, and quantum yields both in solids and in the aggregated state; these can be rationalized by scrutinizing intermolecular interactions in the crystalline solid state.     

Spiroconjugated Intramolecular Charge‐Transfer Emission in Non‐Typical Spiroconjugated Molecules: The Effect of Molecular Structure upon the Excited‐State Configuration

A set of terfluorenes and terfluorene‐like molecules with different pendant substitutions or side groups were designed and synthesized, their photophysical properties and the excited‐state geometries were studied. Dual fluorescence emissions were observed in compounds with rigid pendant groups bearing electron‐donating N atoms. According to our earlier studies, in this set of terfluorenes, the blue emission is from the local π–π* transition, while the long‐wavelength emission is attributed to a spiroconjugation‐like through‐space charge‐transfer process. Herein, we probe further into how the molecular structures (referring to the side groups, the type of linkage between central fluorene and the 2,2′‐azanediyldiethanol units, and—most importantly—the amount of pendant groups), as well as the excited‐state geometries, affect the charge‐transfer process of these terfluorenes or terfluorene‐like compounds. 9‐(9,9,9′′,9′′‐tetrahexyl‐9H,9′H,9′′H‐[2,2′:7′,2′′‐terfluoren]‐9′‐yl)‐1,2,3,5,6,7‐hexahydropyrido[3,2,1‐ij]quinolone (TFPJH), with only one julolidine pendant group, was particularly synthesized, which exhibits complete “perpendicular” conformation between julolidine and the central fluorene unit in the excited state, thus typical spiroconjugation could be achieved. Notably, its photophysical behaviors resemble those of TFPJ with two pendant julolidines. This study proves that spiroconjugation does happen in these terfluorene derivatives, although their structures are not in line with the typical orthogonal π fragments. The spiroconjugation charge‐transfer emission closely relates to the electron‐donating N atoms on the pendant groups, and to the rigid connection between the central fluorene and the N atoms, whereas the amount of pendant groups and the nature of the side chromophores have little effect. These findings may shed light on the understanding of the through‐space charge‐transfer properties and the emission color tuning of fluorene derivatives.     

固体核磁共振在介孔分子筛研究中的应用

介绍了强功率质子去耦、交叉极化、魔角旋转等同体高分辨核磁共振技术的原理,综述了固体高分辨核磁共振技术在介孔分子筛结构与形态研究中的应用及近年来的发展情况.     

Molecular Basis for the Mechanical Response of Sulfa Drug Crystals

Comprehension of the nanomechanical response of crystalline materials requires the understanding of the elastic and plastic deformation mechanisms in terms of the underlying crystal structures. Nanoindentation data were combined with structural and computational inputs to derive a molecular-level understanding of the nanomechanical response in eight prototypical sulfa drug molecular crystals. The magnitude of the modulus, E, was strongly connected to the non-covalent bond features, that is, the bond strength, the relative orientation with the measured crystal facet and their disposition in the crystal lattice. Additional features derived from the current study are the following. Firstly, robust synthons well isolated by weak and dispersive interactions reduce the material stiffness; in contrast, the interweaving of interactions with diverse energetics fortifies the crystal packing. Secondly, mere observation of layered structures with orthogonal distribution of strong and weak interactions is a prerequisite, but inadequate, to attain higher plasticity. Thirdly, interlocked molecular arrangements prevent long-range sliding of molecular planes and, hence, lead to enhanced E values. In a broader perspective, the observations are remarkable in deriving a molecular basis of the mechanical properties of crystalline solids, which can be exploited through crystal engineering for the purposeful design of materials with specific properties.     

The Rise of Dye-Sensitized Solar Cells: From Molecular Photovoltaics to Emerging Solid-State Photovoltaic Technologies

Over the past three decades, dye-sensitized solar cells (i. e. Grätzel cells) have evolved from a pioneering concept of molecular photovoltaics to large-scale industrial deployment. In this review article, we provide a historical overview of the developments with a focus on the scientific advancements that have set the stage for this technology to emerge and thrive. This involves insights into the (photo)electrochemistry of the underlying processes, molecular engineering of dyes, redox shuttles, and hole-transporting materials, as well as their implementation into solar cells. We further outline applications and future perspectives, involving the long-lasting objective to develop efficient solid-state alternatives to conventional dye-sensitized solar cells.     

Molecular Complexes of Fullerenes C60 and C70 with Saturated Amines

New molecular complexes of fullerenes C₆₀ and C₇₀ with leuco crystal violet (LCV, 1-3); leucomalachite green (LMG, 4-6); crystal violet lactone (CVL, 7); N,N,N′,N′-tetrabenzyl-p-phenylenediamine (TBPDA, 8, and 9); N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPDA, 10, and 11); triphenylamine (TPA, 12, and 13); and substituted phenotellurazines (EPTA and TMPTA, 14, and 15) have been synthesized. Crystal structures have been solved for C₆₀ complexes with LMG (5, 6) TBPDA (8), TMPDA (10), and TPA (12). The C₆₀ molecules form closely packed double layers in 5 and 6, hexagonal layers in 10 and quasi-three-dimensional layers in 8 and 12. The substitution of disordered solvent molecules in the complexes with LMG (4, 5) by naphthalene ones results in the ordering of the C₆₀ molecules. According to IR-, UV-visible-NIR and ESR-spectroscopy the complexes have a neutral ground state. The spectra of 1-8, and 10 show intense charge transfer bands in the visible and NIR-range. On photoexcitation by white light (light-induced ESR (LESR) spectroscopy), 1 and 10 were shown to have an excited ionic state. The LESR signals were generated at light energies <2.25 eV indicating that the excited states in the complexes are realized mainly by direct charge transfer from donor to the C₆₀ molecule.     

分子基材料聚集态结构的场发射性质研究

场发射在扫描电子显微镜、平面显示器、压力传感器、加速度传感器以及电子束可寻址记忆器件等许多领域中得到了广泛的应用,分子基材料由于其结构和能带可设计,性质可调和柔性易加工等显著特点,被认为是新一代的场发射材料。本文综述了近年来分子基材料聚集态结构的场发射性质研究的新进展,特别是分子基材料的结构和聚集态形貌和尺寸对场发射性质的影响以及通过对分子基材料的杂化优化其场发射的性质,展望了分子基材料聚集态结构场发射的应用前景和发展趋势。     

Photophysics of 9,9-Dimethylacridan-Substituted Phenylstyrylpyrimidines Exhibiting Long-Lived Intramolecular Charge-Transfer Fluorescence and Aggregation-Induced Emission Characteristics

Six pyrimidine-based push–pull systems substituted at positions C2 and C4/6 with phenylacridan and styryl moieties, employing methoxy or N,N-diphenylamino donors, have been designed and synthesized through cross-coupling and Knoevenagel reactions. X-ray analysis confirmed that the molecular structure featured the acridan moiety arranged perpendicularly to the residual π system. Photophysical studies revealed significant differences between the methoxy and N,N-diphenylamino chromophores. Solvatochromic studies revealed that the methoxy derivatives showed dual emission in polar solvents. Time-resolved spectroscopy revealed that the higher energy band involved very fast (<80 ps) fluorescence, whereas the lower energy one included long components (≈30 ns) due to long-lived intramolecular charge-transfer fluorescence. In contrast to N,N-diphenylamino chromophores, the methoxy derivatives also showed aggregation-induced emission in mixtures of THF/water, as well as dual emission in thin films, covering almost the whole visible spectrum with corresponding chromaticity coordinates not far from that of pure white light. These properties render the methoxy derivatives as very promising organic materials for white organic light-emitting diodes.     

2，4，6－三苯基氧鎓盐分子内旋转受阻对其发光行为的影响

研究了４－位苯基取代基旋转受阻和旋转自由的２，４，６－三苯基氧盐的光物理性质。实验结果表明，当４－位苯基取代基旋转受阻时，氧盐化合物在激发态时引起的分子内极化程度比４－位取代基旋转自由的氧盐化合物大，即在激发态时旋转受阻氧盐化合物发生的分子内电荷转移能力较强；４－位取代基旋转自由的化合物的荧光量子产率随溶剂粘度的增大而有所增大，但旋转受阻化合物在相同的条件下则出现相反的结果。实验结果还表明，４－位取代苯基旋转受阻对化合物的荧光发射不利。     

Molecular structures and reactivities of 1,3-diphthalimidobenzene derivatives

X-ray diffraction analysis of 4,6-di(morpholin-4-yl) and 4,6-di(2,2,2-trifluoroethoxy) derivatives of 1,3-diphthalimidobenzene, which are potent reagents in the synthesis of heterocyclic polymers, was carried out. The conjugation between the π-systems of the benzene ring and of the phthalimide and morpholine substituents is distorted due to the rotation of the substituents about the C(Ar)−N bonds. The AMI calculations demonstrated that the hydrogen atoms of the methylene groups are “acidic”, which is favorable for condensation reactions. Steric hindrances to intramolecular condensation were estimated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1155–1161, June, 1998.     

血红素蛋白的分子设计新趋向

综述了近年来有关血红素蛋白分子设计所出现的新趋向, 包括氨基酸选择突变与血红素修饰相结合,非天然辅基的引入,非天然氨基酸的引入,辅基与蛋白肽链的共价结合,以及全新血红素蛋白的设计与构建5个方面。这些新发展趋向对研究金属蛋白的结构-功能关系提供了重要的信息,同时也为这些理性设计的新颖金属蛋白分子拓宽了其在生物化学、生物工程和药学上的应用。     

Pressure-Induced Conversion of a Paramagnetic FeCo Complex into a Molecular Magnetic Switch with Tuneable Hysteresis

A key challenge in the design of magnetic molecular switches is to obtain bistability at room temperature. Here, we show that application of moderate pressure makes it possible to convert a paramagnetic Fe^III₂Co^II₂ square complex into a molecular switch exhibiting a full dia- to paramagnetic transition: Fe^IICo^III ⇔ Fe^IIICo^II. Moreover, the complex follows a rare behavior: the higher the pressure, the broader the magnetic hysteresis. Thus, the application of an adequate pressure allows inducing a magnetic bistability at room temperature with predictable hysteresis width. The structural studies at different pressures suggest that the pressure-enhanced bistability is due to the strengthening of intermolecular interactions upon pressure increase. An original microscopic Ising-like model including pressure effects is developed to simulate this unprecedented behavior. Overall, this study shows that FeCo complexes could be very sensitive piezo switches with potential use as sensors.