The unusual physicochemical properties of azulene and azulene-based compounds

Azulene, an isomer of naphthalene, has become one of hot chemical structures in the research field of functional materials, due to its anti-Kasha’s rule emissions and unusual physicochemical properties (e.g., photophysical, electrochemical, and photoelectrochemical properties). In the past, the synthesis of azulene-based compounds is relatively inconvenient. Recently, there have been more and more reports about the synthesis strategies of the azulene-based compounds for finely tuning the physicochemical properties. In this article, we introduce several synthetic methods for kinds of azulene-based compounds which has unusual physicochemical properties. With these convenient methods and unique physicochemical properties, azulene-based compounds can be applied into many fields such as specific bioimaging, advanced molecular switches, organic field-effect transistor (OFET), organic light emitting diode (OLED), solar cells, and so forth. And these properties are also summarized here.     

Synthesis and liquid crystalline behavior of azulene-based liquid crystals with 6-hexadecyl substituents on each azulene ring

Hexakis(6-hexadecyl-2-azulenyl)benzene (1b) has been synthesized by Co₂(CO)₈-catalyzed cyclotrimerization reaction of bis(6-hexadecyl-2-azulenyl)acetylene (2b). The mesomorphic behaviors of 1b, 2b, and 6-hexadecyl-2-phenylazulene (3b) were studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction (XRD) techniques and their mesomorphic properties were compared with those of their 6-octyl derivatives 1a, 2a, and 3a. Increase of the number of carbon atoms in the peripheral side chains drops the isotropization temperatures of 1b, 2b, and 3b by 56.9 °C, 33 °C, and 23.6 °C, respectively. Additionally, the phase-transition behavior varied with increase of the number of the peripheral chains, as well as decrease of the crystalline-mesophase transition temperatures, except for compound 3b. As the results, spontaneous monodomain homeotropic molecular alignment was revealed by compound 1b in its Col_hd mesophase on non-treated glass substrate, which would be attracted to the application for the device fabrication of molecular materials.     

The physicochemical properties of some imidazolium-based ionic liquids and their binary mixtures

The density, viscosity and conductivity of ionic liquids (ILs), 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF4]), 1-octyl-3-methylimidazolium chloride ([omim][Cl]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim] BF4]), 1-hexyl- 3-methylimidazolium chloride ([hmim][Cl]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF6]), and the [omim][BF4] + [omim][Cl], [hmim][BF4] + [hmim][Cl], and [hmim][PF6] + [hmim][Cl] binary mixtures were studied at dif- ferent temperatures. It was demonstrated that the densities of both the neat ILs and their mixtures varied linearly with temper- ature. The density sensitivity of a binary mixture is between those of the two components. The excess molar volumes (VE) of [hmim][BF4] + [hmim][Cl] and [hmim][PF6] + [hmim][Cl] mixtures are positive in the whole composition range. For [omim][BF4] + [omim][Cl], the VE is also positive in the [omim][Cl]-rich region, but is negative in the [omim][BF4]-rich re- gion. The viscosity or conductivity of a mixture is in the intermediate of those of the two neat ILs. For all the neat ILs and the binary mixtures studied, the order of conductivity is opposite to that of the viscosity. The Vogel-Tammann-Fulcher (VTF) equations can be used to fit the viscosity and conductivity of all the neat ILs and the binary mixtures. The neat ILs and their mixtures obey the Fractional Walden Rule very well, and the values of the Walden slopes are all smaller than unit, indicating obvious ion associations in the neat ILs and the binary mixtures.     

有机同系物性质的递变规律研究

以有机同系物结构重复单元数值连续变化为模型,得到同系物行质递变的两个基本规律：P=a+bn和P=c+kln(n+a/n+b),a,b,c,k均为常数,n为结构重复单元数值,P为同系物的物性。一般地,加和型性能遵守直线变化规律,而结构型和凝聚型性能遵守同系对数线性规律。     

Synthesis, structure and properties of intercalation compounds containing perfluoroalkyl groups

Synthesis, structure and properties of various layered materials containing perfluoroalkyl groups in their interlayer space were summarized. They were obtained by ion exchange method for layered materials with ion exchange capacity and by silylation technique for those possessing acidic hydroxyl groups. The orientation of perfluoroalkyl groups greatly changed depending on their contents in the layered materials. The nature of the interlayer space of them changed from hydrophilic to hydrophobic and they were well dispersed in appropriate organic solvents. Some of them formed so called nanosheet solution and film samples were prepared from it. Organic molecules were introduced into the intercalation compounds by co-adsorption or exfoliation-restacking methods. The empty space surrounded by perfluoroalky chains where organic molecules are included showed unique properties. The weak interaction between perfluoroalkyl chains and included organic molecules lead the easy diffusion of them in the interlayer space, which caused the aggregation of them or affected the distribution of isomers obtained by photochemical reaction. The low vibrational C-F bonding in perfluoroalky groups reduced radiational quenching, accordingly enhanced the fluorescence from included organic dyes.     

Synthesis and photophysical properties of metal anthraquinone phthalocyanine

A novel anthraquinone phthalocyanine Al(Ⅲ) 4 and Co(Ⅱ) 5 were synthesized and characterized by elemental analysis, IR, UV/ vis, 1H NMR, HPLC and MS. The photophysical properties of the two metal complexes were studied and compared by ?uorescence spectrum method.     

Synthesis and structure of polyunsaturated [10]paracyclophane annulated by two azulene rings

The polyunsaturated [10]cyclophane 4 was synthesized from 1,4-diacetylbenzene by a four-step sequence involving the modified Yasunami azulene synthesis, introduction of two butenone units, and a subsequent McMurry coupling reaction. The crystal structures of 4 and the synthetic intermediate 8 was determined by X-ray crystallographic analysis and the results reveal that (1) the benzene ring of 4 is distorted as a boat form with relatively small bending angles and (2) the azulene rings of 8 show large out-of-plane deformation along the short azulene molecular axis.     

The formation and physicochemical properties of magnesium manganates

The effects of calcination temperature, molar ratio and the doping by CeO₂ on the solid–solid interactions, surface and catalytic properties of Mn/Mg mixed oxide system have been studied by XRD, nitrogen adsorption at −196 °C and the catalytic decomposition of hydrogen peroxide at 20, 30, and 40 °C.

The results revealed that the manganese oxides interacted with magnesium oxide to yield well crystallized magnesium manganates at temperatures starting from 600 °C, this reaction found to be affected by the molar ratio of the reacted oxides present and also by the dopant content. However, the treatment of the Mn/Mg mixed oxide system with increasing amounts of manganese and cerium oxides followed by calcination at 400–800 °C brought about an increase in the catalytic activity of the resulting solids, whilst the opposite effect was observed in the surface area of the investigated solids. These treatments resulted in an increase in the particle size of MgO and a decrease in both the activation energy of sintering of the investigated system and that necessary for hydrogen peroxide decomposition reaction.     

Self-assembling and photophysical properties of the organogelators based on cyanostyryl-substituted carbazoles

Four cyanostyryl-substituted carbazole derivatives (CN-ODEC1, CN-ODEC2, CN-DDEC1, and CN-DDEC) were synthesized and their self-assembly properties have been studied. It was found that they could form organogels especially in aromatic solvents. Scanning electron microscopy and light microscopy images show that the xerogels formed from monosubstituted derivatives (CN-O/DDEC1) gave well-organized tapes, and those from disubstituted derivatives (CN-O/DDEC2) exhibited heavy entangled three-dimensional structures. The UV–vis absorption and fluorescence emission spectra, as well as X-ray diffraction patterns, suggest that carbazole derivatives underwent J-type π-stacking. Meanwhile, we suggested that strong H-bonding and moderate π–π interactions were the key driving force for the gelation of the monosubstituted derivatives, and head-to-tail “ladder-type” J-aggregates were formed in the gel state. On the other hand, strong π–π interaction might be considered as the main driving force for the gelation of disubstituted derivatives, and J-aggregates with no well-organized packing mode of molecules were obtained in the gel phase. It should be noticed that aggregation-induced emission was observed during the gelation processes.     

Azo compounds with different sized fluorophores and characterization of their photophysical properties based on trans to cis conformational change

We synthesized fluorophores of different sizes attached to azo derivatives, such as thiophene-, naphthalene-, anthracene-, and pyrene-based azo compounds, and studied their photophysical properties. The compounds exhibited strong color and intensity changes in absorption and emission during the structural change from trans to cis, which also resulted in a large Stokes shift and a difference in quantum yield. Depending on their size, the compounds had different rates of transformation from the trans to cis structure: less conjugated (smaller) fluorophore azo compounds showed higher transition rates than more conjugated (larger) ones.     

Photophysical and electrochemical properties of heteroleptic tris-cyclometallated Ir(III) complexes

Some new heteroleptic tris-cyclometallated iridium(III) complexes have been synthesized and fully characterized. Among these iridium(III) complexes, bis(1-phenylpyrazolato-N,C^2′)iridium(III)[5-(2′-pyridyl)tetrazolate] (3) and bis(3-methyl-1-phenylpyrazolato-N,C^2′)iridium(III)[5-(2′-pyridyl)tetrazolate] (4) show excellent quantum yields at room temperature, the electron density being perturbed by introducing the pyridyltetrazole ligand, making k_r > k_nr. This destroys the concept of phenylpyrazole based iridium complexes.     

Thorium compounds with non-metals: Electronic structure, chemical bond, and physicochemical properties

The current state of research on the nature of the chemical bond and the physicochemical properties of binary Th-X (X = H, B, C, N, O, P, S, As, Se, Sb) and ternary (carbonitrides, thorates, and silicates) thorium compounds by modern ab initio methods of the band structure theory is reviewed. The possibilities of the ab initio band structure methods in describing the structural states, phase stability, elasticity characteristics, X-ray emission, absorption, and photoelectron spectra of thorium-containing systems are discussed.     

Syntheses and spectroscopic properties of substituted diazaborepins with large stokes shift

The substituted diazaborepins (DABs) with halogen (Cl, Br), methoxyl and ethyl ester group on the fifth position of indole unit have large stokes shift, high fluorescence quantum yields and would be used in biomedicine. Their absorption and emission properties were studied in different solvents. Electron-withdrawing group tended to a bathochromic shift of the absorption and fluorescence probably due to its D-π-A structure. Solvatochromic effects were also studied based on Lippert-Mataga equation. DAB-5 with ethyl ester group exhibits more pronounced fluorescence solvatochromic effects than DAB-3 with Br group. The energy gap and simulated stick spectra of DABs based on Density Functional Theory (DFT) and Time-dependent Density Functional Theory (TD-DFT) calculation was obtained.     

Synthesis and properties of tribranched chromophores with triazine and fluorene units

Two tribranched chromophores,1,3,5-triazine as electron deficient core,9,9-dimethylfluorene asπ-conjugated bridge, diphenylamino(4a) and naphthylamino(4b) as electron-donating end-groups,were successfully prepared via Buchwald-Hartwig coupling reaction.Their linear photophysical and two-photon absorption(TPA) properties were investigated by absorption, fluorescence and nonlinear transmission method,respectively.The absorption cut-offs of the chromophores are below 550 nm and both chromophores have strong fluorescence emission.The compound 4a(206.3 GM) exhibits larger TPA cross-section than 4b (57.8 GM) in the femtosecond regime at 800 nm.     

Reaction of azulene with 1,2-bis[4-(dimethylamino)phenyl]-1,2-ethanediol in a mixed solvent of methanol and acetonitrile in the presence of hydrochloric acid: a facile one-pot synthesis and properties of new triarylethylenes possessing an azulen-1-yl group

Reaction of azulene (1) with 1,2-bis[4-(dimethylamino)phenyl]-1,2-ethanediol (2) in a mixed solvent of methanol and acetonitrile in the presence of 36% hydrochloric acid at 60 °C for 3 h gives 2-(azulen-1-yl)-1,1-bis[4-(dimethylamino)phenyl]ethylene (3) (8% yield), 1-(azulen-1-yl)-(E)-1,2-bis[4-(dimethylamino)phenyl]ethylene (4) (28% yield), and 1,3-bis{2,2-bis[4-(dimethylamino)phenyl]ethenyl}azulene (5) (9% yield). Besides the above products, this reaction affords 1,1-di(azulen-1-yl)-2,2-bis[4-(dimethylamino)phenyl]ethane (6) (15% yield), a meso form (1R,2S)-1,2-di(azulen-1-yl)-1,2-bis[4-(dimethylamino)phenyl]ethane (7) (6% yield), and the two enantiomeric forms (1R,2R)- and (1S,2S)-1,2-di(azulen-1-yl)-1,2-bis[4-(dimethylamino)phenyl]ethanes (8) (6% yield). Furthermore, addition reaction of 3 with 1 under the same reaction conditions as the above provides 6, in 46% yield, which upon oxidation with DDQ (=2,3-dichloro-5,6-dicyano-1,4-benzoquinone) in dichloromethane at 25 °C for 24 h yields 1,1-di(azulen-1-yl)-2,2-bis[4-(dimethylamino)phenyl]ethylene (9) in 48% yield. Interestingly, reaction of 1,1-bis[4-(dimethylamino)phenyl]-2-(3-guaiazulenyl)ethylene (11) with 1 in a mixed solvent of methanol and acetonitrile in the presence of 36% hydrochloric acid at 60 °C for 3 h gives guaiazulene (10) and 3, owing to the replacement of a guaiazulen-3-yl group by an azulen-1-yl group, in 91 and 46% yields together with 5 (19% yield) and 6 (13% yield). Similarly, reactions of 2-(3-guaiazulenyl)-1,1-bis(4-methoxyphenyl)ethylene (12) and 1,1-bis{4-[2-(dimethylamino)ethoxy]phenyl}-2-(3-guaiazulenyl)ethylene (13) with 1 under the same reaction conditions as the above provide 10, 2-(azulen-1-yl)-1,1-bis(4-methoxyphenyl)ethylene (16), and 1,3-bis[2,2-bis(4-methoxyphenyl)ethenyl]azulene (17) (93, 34, and 19% yields) from 12 and 10 and 2-(azulen-1-yl)-1,1-bis{4-[2-(dimethylamino)ethoxy]phenyl}ethylene (18) (97 and 58% yields) from 13.     

The synthesis and physicochemical and catalytic properties of SHS zeolites

Superhigh-silica ZSM-type zeolites with silica moduli of 100–220 were synthesized using hexamethylenediamine as a structure-forming additive. Physicochemical methods were used to identify them as ZSM-5-type zeolites, determine their degree of crystallinity, specific surface areas, and morphology of crystals, and study the phase and elemental composition. The strength and concentration of acid centers were found to decrease as the silica modulus grew. The zeolites obtained can be used as the main component of catalysts for refining low-octane gasoline fractions and methanol conversion into hydrocarbons.     

The effect of complexing agent on crystal growth,structure and properties of nanostructured Cu_（2-x）S thin films

Thin films of Cu2 x S（x = 0, 1） were deposited on self-assembled, monolayer modified substrates in the copper–thiosulfate system with various concentrations of ethylene diamine tetraacetic acid（EDTA） at a low temperature of 70 8C. The thin films were characterized by means of X-ray diffraction（XRD）, X-ray photoelectron spectroscope（XPS）, field emission scanning electron microscopy（FESEM）, transmission electron microscopy（TEM）. The optical and photoelectrochemical（PEC） properties of the Cu2 x S semiconductor films were investigated by ultraviolet–visible（UV–vis） absorption spectroscopy and a three-electrode system. It is found that EDTA plays a key role in the process of Cu2 x S nanocrystals formation and growth. The compositions of the Cu2 x S nanocrystals varied from Cu2S（chalcocide） to Cu S（covellite） through adjusting the concentration of EDTA, which is used as a complexing agent to yield high-quality Cu2 x S films. The growth mechanisms of Cu2 x S nanocrystals with different EDTA concentrations are proposed and discussed in detail.