Conformational analysis of some ortho-hydroxyazoic dyes by the PCILO method

The quantum mechanical MO method PCILO is used to perform a detailed conformational analysis of ortho-hydroxyazobenzene and 1-phenyl azo 2-napthol. Several energy minima are obtained for each compound, after a simultaneous optimization of the main geometric parameters. Comparison is made with the corresponding para compounds. The calculated results are discussed in relation to the available experimental data.     

Conformational analysis of oxazolidines by molecular and quantum mechanics and NMR spectroscopy

A combined experimental (¹HNMR) and theoretical (molecular mechanics and PCILO) study of (4S,5S,6R)-4-carbome-thoxyethylenyl-N-carbobenzyloxy-5-methyl-6-phenyl oxazolidine has been carried out with the purpose of contributing to a better understanding of the steric and electronic factors responsible for the observed diastereoisomeric selectivity in the dihydroxylation of oxazolidines leading to optically active α, β dialkoxyaldehydes.     

Anti-configuration of the N = N bond in azobilirubin pigments

The conformational and internal energy barriers for rotation of the phenylazo group in azobilirubin pigments were determined by the PCILO method. The calculations showed a restricted rotation of the azo group at 180–300° dihedral angle.     

3-取代酚酮5位偶联产物的溴氧化成环反应

报道了采用溴氧化3-异丙烯基(艹卓)酚酮和3-肉桂酰基(艹卓)酚酮合成杂环并(艹卓)酮化合物的新方法。3-异丙烯基(艹卓)酚酮5位偶联产物1a～1f和3-肉桂酰基(艹卓)酚酮5位偶联产物3a～3d分别在吡啶介质中与过量溴作用生成5-取代苯偶氮基-7-溴-3-甲基-8-氢环庚并呋喃-8-酮2a～2f和6-取代苯偶氮基-2-苯基-8-溴-4,9-二氢环庚并吡喃-4,9-二酮4a～4d。     

Research on imidazoles

The reactivity of the methylene group of 5-phenyl and a, G-diphenylimidazo [2, 1-b]thiazolid-3-ones is investigated. The corresponding alkylidene, arylidene, and azomethine derivatives are prepared by reaction with, respectively, aldehydes, isatin, and nitro compounds. Diazonium salts give azo coupling products whose IR spectra show then to be 2-arylhydrazines of imidazo[2, 1-b]thiazolid-2, 3diones.For Part XXXIII see [18]     

Copper(II) complexes of thiazolylazo dye with triphenylphosphine and or NCS− as coligands: synthesis,spectral characterization,electrochemistry and luminescence properties

A series of copper(II) complexes [Cu(L₁ or L₂ or L₃)(PPh₃)₂(N₃)₂] (1a–3a) and [Cu(L₁ or L₂ or L₃)(PPh₃)₂(NCS)₂] (1b–3b) (where L₁ = 4-(4′-phenyl,2′-thiazolylazo)chlorobenzene, L₂ = 4-(4′-phenyl,2′-thiazolylazo)bromobenzene, and L₃ = 4-(4′-phenyl,2′-thiazolylazo)iodobenzene) have been prepared and characterized on the basis of microanalytical data, molar conductances, magnetic moments, UV-Vis, infrared, and ESR spectra. On the basis of electronic spectra and magnetic susceptibility octahedral geometry has been proposed for the complexes. The ESR spectral data provide information about their structures on the basis of Hamiltonian parameters and degree of covalancy. The electrochemical behavior of the complexes showed that the redox responses of Cu(II) complexes shifted to more negative potential with decrease in electron-withdrawing substituents on the azo ligands. Complexes exhibit blue-green emission with high-quantum yield.     

Study of the nucleophilic behaviour of N-phenylbenzamidine towards 1,2-diaza-1,3-dienes: domino reactions for imidazole scaffolds

Depending on the nature of the solvent, alcohol or DMF, N-phenylbenzamidine shows different nucleophilic behaviour towards the conjugated azo–ene system of 1,2-diaza-1,3-dienes. In alcohol it reacts as a nucleophile through the N-phenyl imino nitrogen affording spiro pyrroloimidazoles and 1,3-diphenyl-1H-imidazoles. In DMF, by contrast, it behaves as nucleophile mainly by means of the imino amidino nitrogen providing 2-phenylimidazole derivatives by loss of the aniline molecule.     

A modified PCILO framework using the CNDO/Boyd–Whitehead parametrization

The CNDO /BW modification of the CNDO /2 approximation was used within the PCILO framework. It was shown on some significant examples that all the good results of the original PCILO -CNDO /2 method can be reproduced by the modified version PCILO -CNDO /BW at least. Thus, preserving the quality of its results a computer-expense-reduced PCILO method is proposed for calculations on large molecular systems.     

Etude théorique de la conformation des complexes moléculaires de type donneur accepteur d'électrons

The stabilisation energy of donor acceptor molecular complexes given by tetracyanoethylene with thiazole and phenylthiazoles have been calculated by several semiempirical approaches. The results obtained with the Extended Hückel theory, the CNDO/2 method and the PCILO method, the latter a perturbative one, are compared and this comparison shows that the PCILO method is well adapted to the study of molecular complexes. The different contributions to the stabilisation energy and the origin of the intermolecular forces have been discussed in relation to the geometry of the complex. For all the studied complexes, the calculated results obtained by the PCILO method agree very well with experiments.

     

Synthesis and study of azo dye compounds: variation of mesogenic behaviour with length of alkyl chains

The mesogenic behaviours of two azo dye liquid crystals, 1 and 4, differ because of the different length of terminal alkyl chains; azo dye 1 shows a SmB phase, azo dye 4 shows nematic and SmA phases during thermal processing. The molecular stackings of these two azo dye liquid crystals are compared on the basis of crystallographic studies to explain such unexpected mesogenic behaviour.     

Conformation analysis of small molecules with PCILO methods

The conformational potential of n-butane, ethyl methyl ether, n-propanol, methyl propyl ether, and 1,2-dimethoxyethane was calculated with different PCILO algorithms as well as with ab-initio SCF –LCAO –MO computations. Compared with ab-initio calculations, the conformational potentials obtained by PCILO methods on the same geometries are too flat. In particular, the barrier at 0? (synperiplanar conformation) is much too low at the second- and third-order level. This is mainly a consequence of the second-order delocalization corrections. Since the PCILO algorithms are not capable of reproducing conformational potentials obtained from ab-initio calculations, only qualitative predictions are possible.     

Optimization of molecular geometries in the PCILO and CNDO/2 formalism. The barrier to internal rotation in thioacetaldehyde

The barrier to internal rotation in thioacetaldehyde was investigated within the PCILO and CNDO/2 framework using standard and optimized geometries. The optimized geometries give for the barrier of PCILO a value closer to the experimental one (1.06 kcal mol^?1) whereas the CNDO/2 results yield a qualitatively wrong conformational behavior.     

PCILO Calculations on “true” van der Waals complexes

The PCILO method was applied to complexes where dispersion energy forms the dominant attractive contribution of the intermolecular interaction energy. With alkane dimers, especially with dimers of higher alkanes (C₄H₁₀)₂, (C₅H₁₂)₂, etc., and the ethylene dimer PCILO was successful as to stabilization energy, equilibrium distance, optimal dimer structure, and energy composition. The dispersion energy part is always underestimated, however. With (X₂)₂ dimers (X = N, F, Cl) PCILO failed, which might be explained by the presence of lone pairs in the subsystems.     

偶氮聚电解质的合成及其pH敏感行为和热光性能研究

利用偶氮聚电解质上的羧基和偶氮生色基团的特性,研究了侧链偶氮聚电解质的pH值敏感性和热光性能.采用重氮-偶合反应方法合成了偶氮苯生色分子4-(4′-硝基苯基偶氮)苯酚,将生色分子、环氧氯丙烷和α-甲基丙烯酸通过自由基聚合法,合成了侧链偶氮聚电解质.利用傅里叶红外光谱(FTIR)、紫外-可见光谱(UV-V is)和核磁共振(1H-NMR)等分析手段对所合成的侧链偶氮聚电解质进行了结构表征.采用差示扫描量热分析仪(DSC)对偶氮聚电解质进行了热稳定性表征,其玻璃化转变温度(Tg)为189.8℃,表明具有较高的热稳定性.研究了不同pH值的偶氮聚电解质溶液的紫外-可见光谱,结果表明,偶氮聚电解质对pH值具有高度敏感性.采用衰减全反射(ATR)原理测量聚合物波导薄膜在650 nm和TM偏振下的折射率和热光系数dn/dT,其值为-1.92479×10-4℃-1,是无机材料如硅酸锌玻璃(5.5×10-6℃-1)和硼硅酸盐玻璃(4.1×10-6℃-1)的10倍以上,较有机材料聚苯乙烯(-1.23×10-4℃-1)和PMMA(-1.20×10-4℃-1)大.     

Synthesis and study of azo dye compounds: variation of mesogenic behaviour with length of alkyl chains

The mesogenic behaviours of two azo dye liquid crystals, 1 and 4, differ because of the different length of terminal alkyl chains; azo dye 1 shows a SmB phase, azo dye 4 shows nematic and SmA phases during thermal processing. The molecular stackings of these two azo dye liquid crystals are compared on the basis of crystallographic studies to explain such unexpected mesogenic behaviour.     

含噻唑偶氮苯生色团环氧树脂类聚合物的合成与表征

合成了2-氨基-4-氯-5-甲酰基噻唑和2-氨基-4-氯-5-二氰乙烯基噻唑.分别将其与亚硝酰硫酸反应配制成重氮盐,通过在极性溶剂中与含苯胺残基的环氧树脂类前体聚合物BP-AN进行重氮偶合反应,得到了两种含噻唑偶氮苯生色团的环氧树脂类聚合物BP-1A-T-F和BP-1A-T-2CN.利用仪器分析手段对其结构、光谱特性和热性能进行了表征,BP-1A-T-F和BP-1A-T-2CN的最大吸收波长分别为579nm和650nm;玻璃化转变温度152℃和149℃.     

The reaction of imidazole with 2-phenyl,4-chloromethylene-oxazol-5-one

The displacement of chlorine from 2-phenyl,4-chloromethylene-oxazol-5-one by imidazole does not lead to carbon-carbon bond formation as previously reported, but involves attack by nitrogen leading to 2-phenyl,4-(imidazol-1-yl)methylene-oxazol-5-one.     

Analytical Azo Coupling Reactions: A Quantum-Chemical Consideration

Azo coupling reactions of 1-aminonaphthalene with naphthalene-1-diazonium and 4-sulfobenzene-diazonium cations are studied by quantum chemistry. It is found that the reactions are orbital controlled and their regioselectivity is unambiguously governed by the thermodynamic properties of the intermediate σ-complexes and by the effect of the aqueous medium. The latter causes high site selectivity, providing the choice of one of the two possible reaction channels predicted on the basis of quantum-chemical calculations of the isolated molecular systems. As a result, azo coupling occurs at the 4-position of the 1-aminonaphthalene molecule. Additionally, the aqueous medium provides the selection of analytical forms, namely, the protonated azo coupling products that have the quinone-hydrazone structure. On the basis of the quantum-chemical study, the analytical performances of the two azo coupling reactions mentioned above are discussed.     

Epoxy-based azo polymers with high chromophore density: Synthesis,characterization and photoinduced birefringence

Three epoxy-based azo polymers(PEP-AZ-Cl,PEP-AZ-CN and PEP-AZ-NT) with high chromophore density were synthesized by using post-polymerization azo-coupling reactions between epoxy-based precursor polymer(PEP-AN) and diazonium salts of 4-chloroaniline,4-aminobenzonitrile and 4-nitroaniline,respectively.The structures and properties of the azo polymers were characterized by using ~1H-NMR,FT-IR,UV-Vis and thermal analyses.The photoinduced birefringence of the azo polymers was studied by irradiating spin-coated films of the polymers with laser beam at three different wavelengths(488,532,and 589 nm).The results indicate that the photoinduced birefringence of the azo polymers is related with the electron-withdrawing group on azo chromophores and the excitation wavelength.The excitation wavelength that can cause the efficient responses is determined by the absorption band positions of the azo chromophores,which are mainly affected by the electron-withdrawing group on the chromophores.Therefore,the azo polymers containing chromophores with different electron-withdrawing groups show different responsive behavior to the irradiation light at different wavelengths.When irradiated with 488 nm light,PEP-AZ-Cl shows the shortest time to reach the saturated birefringence but with the lowest saturation birefringence level compared with the other two azo polymers.When irradiated with 532 nm light,PEP-AZ-CN shows the shortest time to reach the saturated birefringence.When irradiated with 532 and 589 nm light,PEP-AZ-NT shows the highest saturation birefringence level.