Stability of Nanoporous Materials

Summary: The stability of nanoporous materials as a result of surface interaction forces has been considered in this paper. We show that cylindrical pores in linear elastic materials will collapse if α = γ/μA > 2. As one would expect physically, smaller cavities tend to be more unstable for the same surface energy and material properties as a result of the high internal Laplace pressure. Extensions to account for large deformation and strain‐hardening effects and for viscoelastic materials are discussed.

Normalized potential energy versus cavity stretch for the well‐known Neo–Hookean material model. The equilibrium solution shifts to the left as the parameter α increases, implying a greater cavity shrinkage.     

4,10‐Dibromoanthanthrone as a New Building Block for p‐Type,n‐Type,and Ambipolar π‐Conjugated Materials

New p‐type, n‐type, and ambipolar molecules were synthesized from commercially available 4,10‐dibromoanthanthrone dye. Substitution at the 4,10‐ and 6,12‐positions with different electron‐rich and electron‐poor units allowed the modulation of the optoelectronic properties of the molecules. A bis(dicyanovinylene)‐functionalized compound was also prepared with a reduction potential as low as ?50 mV versus Ag⁺ with a crystalline two‐dimensional lamellar packing arrangement. These characteristics are important prerequisites for air‐stable n‐type organic field‐effect transistor applications.     

Synthesis,Characterization, and Catalytic Activity of Metallo Octamethylcalix (4) Pyridino Complexes Encapsulated in MCM-41

The synthesis and encapsulation of M⁺ⁿ-octamethylcalix(4)pyridino complexes using acetone and pyridine in H-MCM-41 have been achieved and presented. These hybrid catalysts are characterized by x-ray diffraction, infrared, thermal analysis, Brunauer–Emmett–Teller (BET) surface area, and scanning electron microscopy and tested for catalytic activity. They are active in the liquid-phase oxidation of p-xylene using H₂O₂ as oxidant and acetic acid as solvent in the temperature range of 30–100 °C. The variation of central transition-metal cation and the heterocyclic ring in the metallomacrocycle influence the catalytic activity.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Impact of Ion-Pairing Effects on Linear and Nonlinear Photophysical Properties of Polymethine Dyes**

The two-photon absorption (2PA) and photophysics of heptamethine dyes featuring cyanine or dipolar electronic structures have been compared for the first time. The perfectly delocalized cyanine system is classically characterized by a two-photon transition matching the vibronic component of its lower energy absorption band. The dipolar species is generated by ion-pairing with a hard counterion in a non-dissociating solvent and displays significant modifications oft he optical properties, including a significant hypochromic shift of absorption, weaker emission and 2PA matching the lower energy transition, thus revealing symmetry breaking within the polymethine electronic structure.     

催化新材料——钛硅分子筛合成及应用研究*

评述了钛硅分子筛新催化材料的合成及其催化应用的研究进展, 包括钛硅分子筛(TS21) 的水热合成方法、原料、模板剂、影响因素、TS21 同晶取代法合成、表征、活性中心、钛硅分子筛双氧水体系的应用研究及近年中孔钛硅分子筛的进展。对未来的研究提出了建议。     

New Soluble Near‐Infrared Dyes Based on Terrylene Diimides with Four Aromatic Heterocycles

Terrylene diimides with four aromatic heterocycles (AHTDIs) were synthesized under Stille Cross‐coupling conditions and fully characterized by NMR and mass spectrometry. The aggregation of the terrylene diimide (TDI) was suppressed by four heterocycles substituents on the bay region, and these AHTDIs exhibited good solubility in common organic solvents. The effects of the substituted groups on the optical and electrochemical properties were also investigated. The introduction of four aromatic heterocycles on the bay of TDI resulted in significant red‐shifts of the absorption peak (100 nm), corresponding to a decrease in the band gap from 1.82 to 1.50 eV. Furthermore, with four rich electron aromatic heterocycles, the AHTDIs showed 280 mV negative‐shifts of first oxidation potentials and a new oxidation wave, corresponding to an increase in the HOMO levels from??5.60 to??5.28 eV.     

Physical,Thermal and Biological Properties of Yellow Dyes with Two Azodiphenylether Groups of Anthracene

Two yellow bis-azo dyes containing anthracene and two azodiphenylether groups (BPA and BTA) were prepared, and an extensive investigation of their physical, thermal and biological properties was carried out. The chemical structure was confirmed by the FTIR spectra, while from the UV–Vis spectra, the quantum efficiency of the laser fluorescence at the 476.5 nm was determined to be 0.33 (BPA) and 0.50 (BTA). The possible transitions between the energy levels of the electrons of the chemical elements were established, identifying the energies and the electronic configurations of the levels of transition. Both crystals are anisotropic, the optical phenomenon of double refraction of polarized light (birefringence) taking place. Images of maximum illumination and extinction were recorded when the crystals of the bis-azo compounds rotated by 90° each, which confirms their birefringence. A morphologic study of the thin films deposited onto glass surfaces was performed, proving the good adhesion of both dyes. By thermal analysis and calorimetry, the melting temperatures were determined (~224–225 °C for both of them), as well as their decomposition pathways and thermal effects (enthalpy variations during undergoing processes); thus, good thermal stability was exhibited. The interaction of the two compounds with collagen in the suede was studied, as well as their antioxidant activity, advocating for good chemical stability and potential to be safely used as coloring agents in the food industry.     

聚合物光学体材料与膜材料的分子设计,合成与性能

总结了有关含砜、硫、溴、金属离子、有机硅、环状化合物、半导体纳米微粒等的聚合物光学体材料与膜材料的功能化及高性能化的设计合成思想,对这些材体材料与膜材料相关的折射率、色散、透光性等光学性质,表面硬度、冲击强度、耐磨性等机械性质及玻璃化转变温度、热稳定性、膨胀系数等热性能进行了研究,讨论了一些透明膜层及复合物的功能性质。     

New Routes to the Synthesis of Mesoporous Materials and Their Properties

The factors that influence the hydrothermal synthesis of MCM-41 were investigated, and it was found that compared with those from high H₂O/SiO₂ systems(designated MCM-41-A), the products from low H₂O/SiO₂ systems(designated MCM-41-B) exhibited a less-defined X-ray powder diffraction (XRD) pattern with a broader main reflection peak at a lower 2θ diffraction angle. MCM-41-B possesses a smaller surface area but a larger pore size than MCM-41-A. New routes including direct thermal treatment, room-temperature crystallization and microwave heating were developed for the formation of MCM-41, and the properties of the products prepared from these new routes were compared with those of the MCM-41 hydrothermally synthesized. The pore sizes of MCM-41 materials are uniformly distributed with an effective pore diameter that falls into the range of 2-4 nm, where as the products from wet-gel thermal treatment possess two kinds of mesopores:the well-defined smaller pores distributed at 3 nm and the larger one within 8-20 nm. The MAS NMR spectroscopy revealed that after calcination to remove the organic template in Al-containing MCM-41, a small part of the tetrahedrally-coordinated framework aluminum atoms became octahedrally-coordinated and a considerable amount of Si-OH species were generated.     

多烯和花菁染料分子设计及其非线性光学性质研究进展

根据一种新的增强分子非线性光学性质的设计思想 ,讨论了多烯和花菁染料的结构和性质关系 ,综述了这类染料的非线性光学性质及其应用进展 ,并对有机非线性光学材料的发展前景进行了预测。     

Oxidation of Organosilanes with Nanoporous Copper as a Sustainable Non‐Noble‐Metal Catalyst

Although many noble‐metal catalysts have been used for the oxidation of organosilanes, there has been less success with non‐noble‐metal catalysts. Here, unsupported nanoporous copper (np‐Cu) is used to catalyze the oxidation of organosilanes under mild conditions. It is the first time that this reaction has been achieved with a heterogeneous copper catalyst with high activity and selectivity. Both water and alcohols are used as oxidants and the corresponding organosilanols and organosilyl ethers are obtained in high yield. The possible mechanism was obtained by kinetic studies. The catalyst could be reused at least five times without evident loss of activity. As a novel green catalyst np‐Cu should play a unique role in organic synthesis.     

Conformational effects of bay substituents on optical, electrochemical and dynamic properties of perylene bisimides: macrocyclic derivatives as effective probes

A series of diagonally and laterally bridged regioisomeric macrocycles based on 1,6,7,12-tetraaryloxy-substituted perylene bisimides (APBIs) have been synthesized and characterized. The different orientations of the aryloxy residues, that is, horizontal or perpendicular to the perylene core, in the regioisomeric macrocycles have been elucidated by NMR spectroscopy, and the dynamic properties of the laterally bridged regioisomers have been investigated by temperature-dependent NMR measurements. The influence of the different orientations of the aryloxy substituents on the electrochemical properties of APBIs is demonstrated by cyclic voltammetry, which reveals that a perpendicular orientation of the aryloxy residues relative to the perylene core leads to a substantial decrease of the LUMO energy level of the perylene bisimide electrophore. The optical properties of the regioisomeric macrocycles have been determined by UV/Vis and fluorescence spectroscopy. It has been shown that the diagonally bridged macrocycles exhibit optical properties that differ significantly from those of an open-chain reference compound, whereas the optical properties of the laterally bridged isomers resemble those of the reference system. This demonstrates that unrestricted aryloxy substituents prefer the lateral conformation in solution. Solvent-dependent fluorescent properties have been exemplified for one diagonally bridged derivative, suggesting a photoinduced electron transfer process as fluorescence quenching mechanism for APBIs. From these investigations, guidelines toward highly fluorescent APBI dyes in polar media could be derived.     

萘酰氨基修饰β-环糊精对几种荧光染料的分子识别

用光谱滴定技术分别测定了β-环糊精(1)、单-[6-(1-萘酰氨基)-乙基氨基-6-脱氧]-β-环糊精(2)、单-[6-(1-萘酰氨基)-二乙基二氨基-6-脱氧]-β-环糊精(3)在25℃时,pH为7.2、2.0和10.1的缓冲溶液中与几种染料分子形成超分子配合物的稳定常数Ks,并考察了pH=7.2时识别过程的热力学参数ΔH0和TΔS0。结果表明,pH为2.0和10.1时,静电、疏水和氢键作用协同贡献于超分子配合物的形成,如主体2与AR在pH=10.1时形成的Ks=7085;而pH=2.0时的Ks=1034。当pH=7.2时主-客体的尺寸/形状匹配、疏水作用和范德华力决定配合物的稳定性。主体2、3对AR、TNS和ANS的包结配位是放热过程,并给出较大的焓变(-ΔH0),对RhB主要表现为熵驱动过程。     

Thiourea- and Amino-Substituted Benzoxadiazole Dyes with Large Stokes Shifts as Red-Emitting Probe Monomers for Imprinted Polymer Layers Targeting Carboxylate-Containing Antibiotics

Bifunctional fluorescent molecular oxoanion probes based on the benzoxadiazole (BD) chromophore are described which integrate a thiourea binding motif and a polymerizable 2-aminoethyl methacrylate unit in the 4,7-positions of the BD core. Concerted charge transfer in this electron donor-acceptor-donor architecture endows the dyes with strongly Stokes shifted (up to >250 nm) absorption and fluorescence. Binding of electron-rich carboxylate guests at the thiourea receptor leads to further analyte-induced red-shifts of the emission, shifting the fluorescence maximum of the complexes to ≥700 nm. Association constants for acetate are ranging from 1–5×10⁵ M⁻¹ in acetonitrile. Integration of one of the fluorescent probes through its polymerizable moiety into molecularly imprinted polymers (MIPs) grafted from the surface of submicron silica cores yielded fluorescent MIP-coated particle probes for the selective detection of antibiotics containing aliphatic carboxylate groups such as enoxacin (ENOX) at micromolar concentrations in highly polar solvents like acetonitrile.     

Optical Properties of New Third-Order Nonlinear Materials Modified by Click Chemistry

A high-yielding click reaction was used to synthesize a series of highly conjugated, symmetrical, as well as asymmetrical compounds with a benzene core. Cyclic voltammetry and ultraviolet/visible absorption spectroscopy were carried out, and proved that the side groups of the benzene derivatives played an important role in the energy gaps, and affected the third-order non-linear optical response. The maximum absorption wavelength of the series of benzene derivatives showed an obvious red-shift. Moreover, the addition of resilient electron-withdrawing groups significantly narrowed the energy levels as compared with precursors. The third-order nonlinear properties of this benzene derivative were tested by the Z-scan technique. The expected properties of this series of molecules were obtained, and it was found that the series of molecules undergoes a transition from reverse saturable absorption to saturable absorption, which has certain reference significance for a nonlinear optical field.     

Mechanism and Nature of the Different Viscosity Sensitivities of Hemicyanine Dyes with Various Heterocycles

A series of hemicyanine derivatives are excellent fluorescent viscosity sensors in live cells and in imaging of living tissues due to their low quantum yields in solution but large fluorescence enhancements in viscous environments. Herein, three carbazole‐based hemicyanine dyes with different heterocycles are studied. They have different background quantum yields, and hence different sensitivities to viscosity detection, large Stokes shifts, and high sensitivity. Better understanding of the structure–property relationships for viscosity sensitivity could benefit the design of improved dyes. Computational studies on these dyes reveal the mechanism of viscosity sensitivity of fluorescent molecular rotors and the nature of the difference in viscosity sensitivity of the three dyes. The results show that the greatly raised HOMO and greatly lowered LUMO in the S₁ state compared with the S₀ state are responsible for the large Stokes shift of the three dyes. The heterocyclic moieties have the primary influence on the LUMO levels of the three hemicyanine dyes. Rotation about the C? C bond adjacent to the carbazole moiety of the three dyes drives the molecule toward a small energy gap between the ground state and the first excited state, which causes mainly nonradiative deactivation. The oscillator strengths in the lowest singlet excited state drop rapidly with increasing rotation between 0 and 95°, which leads to a dark state for these dyes when fully twisted at 95°. We draw a mechanistic picture at the molecular level to illustrate how these dyes work as viscosity‐sensitive fluorescent probes. The activation barriers and energy gaps of C? C bond rotation strongly depend on the choice of heterocycle, which plays a major role in reducing fluorescence quantum yield in the free state and provides high sensitivity to viscosity detection in viscous environments for the carbazole‐based hemicyanine dyes.     

Rh(III)-Catalyzed One-Step Synthesis of ortho-Alkynylated Perylene Imide Dyes: Optical and Electrochemical Properties of New Derivatives

A one-step Rh-catalyzed site-selective ortho-C−H alkynylation of perylene as well as naphthalene mono- and diimides is reported. A single step regioselective access to ortho-C−H alkynylated derivatives of these ryleneimides not only increases the step economy of the ortho-functionalization on these dyes but also provides a quick access route towards highly functionalized dyes that have potential optoelectronic applications. Increased solubility of tetra(triisopropylsilyl)acetylenyl PDIs in organic solvents greatly enhances their utility for further derivatization.     

新型沸石分子筛主体-纳米客体复合材料研究进展

This paper mainly elaborated the recent developments of the studies on the new type zeolite molecular sieve host-nanoguest composite materials composing of molecular sieve channels or cages encapsulated nanoscale materials from the point of nanochemistry and material science, and the trends of development in this field. As the research of the properties of this kind of materials are going on, it is possible that this kind of host-guest nanocomposite materials will be usd in some fields. such as science and high technology fields. as the new type of optical, electrical and magnetic materials in the level of molecular assembly. This paper contains the following contents: hosts and guests; the sizes and shapes of guests; the optical, electrical and magnetic properties of the materials; the syntheses and characterizations of the materials; the applications of the materials and forecast.     

Fused Perylene–Phthalocyanine Macrocycles: A New Family of NIR‐Dyes with Pronounced Basicity

The synthesis and characterization of a new type of chromophore, namely PePc consisting of a central phthalocyanine core and four fused perylene–bisimide (PBI) units is described for the first time. The entire architecture represents a highly extended conjugated heterocyclic π‐system with C_4h symmetry. In order to guarantee pronounced solubility in organic solvents the corresponding PBI units were bay‐functionalized with tert‐butylphenoxy substituents. Next to the metal‐free macrocycle, PePcH₂, also metallated macrocycles PePcM (M=Zn, Ni, Pb, Ru, Fe) were synthesized. The extensive fusion of the corresponding aromatic building blocks to the very large extended π‐system leads to a very narrow HOMO–LUMO gap and as a consequence to transparency in the visible but light absorption in the NIR region. Significantly, the azomethine N‐atoms N1?N4 of PePcM and PePcH₂ are highly basic. The corresponding tetraprotonated systems can only be deprotonated with very strong non‐nucleophilic bases such as phosphazene bases. In the protonated forms PePcMH₄⁴⁺ and PePcMH₆⁴⁺ the absorption maximum is shifted back to the visible region due to the loss of conjugation. The experimental findings were corroborated with quantum mechanical calculations.