Wide-line 1H NMR and DSC study of mesomorphic transformations of p-(alkoxybenzylidene)-p′-toluidines

p-(Alkoxybenzylidene)-p′-toluidines (ABTs) with 7, 8, and 10 carbon atoms in the alkyl moiety have been studied by wide-line ¹H NMR and DSC. The thermotropic properties of these compounds have been studied in the temperature range 20–80°C, including main mesomorphic transformations of ABTs. The 1H NMR line shapes, widths, and second moments, as well as specific features of their temperature-induced changes, are discussed. The DSC data are compared with the character of mesomorphic transformations and ¹H NMR data. The formation limits and ranges and stabilities of liquid-crystalline states of the ABT structure emerging on heating are determined.     

Anisotropy of reflection spectrum and band structure of SbSI

Anisotropy of the SbSI reflection spectra at various temperatures (300, 273, and 90 °K) is studied. Selection rules are examined for matrix transition elements at extreme points for crystals with symmetry D _2h ¹⁶ , C _2v ⁹ , and C ₂ ² corresponding to different states of SbSI during phase transitions. A comparison of experimental data with theoretical and group-theoretical analysis results made possible a conclusion on the character of the band spectrum.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 13–19, August, 1971.     

Exciton spectra, valence band splitting, and energy band structure of CuGaXIn1−XS2 and CuGaXIn1−XSe2 crystals

Exciton spectra are studied in CuGa_XIn_1−XS₂ solid solutions by means of photoreflectivity and wavelength modulation spectroscopy at liquid nitrogen temperature. The exciton parameters, dielectric constants, and free carrier effective masses are deduced from experimental spectra by calculations in the framework of a model taking into account the spatial dispersion and the presence of a dead-layer. The crystal field and spin orbit valence band splitting is calculated as a function of X taking into account the energy position of excitonic lines. The energy band structure of CuGa_XIn_1−XS₂ and CuGa_XIn_1−XSe₂ compounds is derived from optical spectra at photon energies higher than the fundamental band gap. The energies of optical transitions are tabulated for X values from 0 to 1.     

Coordination properties of trimeric porphyrin in acetic acid

Trimeric porphyrin H₆TP as well as its binuclear Cu₂H₂TP and trinuclear Cu₃TP copper complexes have been prepared. Kinetic features of H₆TP and Cu₂H₂TP complexes formation with copper(II) acetate in acetic acid as well as dissociation kinetics of Cu₂H₂TP and Cu₃TP in acetic acid medium in the presence of sulfuric acid have been studied.     

Energy Band Structure of CuInS2 Crystals

In this work the reflectivity spectra and wave-length derivative reflectivity (WDR) spectra of CuInS₂ crystals have been investigated in the region E ≥ E_g. The n = 1, n = 2 and n = 3 excitonic states are determined and contours of exciton lines n = 1 are calculated. The parameters of excitons and bands have been determined for the region of band gap minimum. The main band gaps are determined for Γ-, N- and T-points of the Brillouin zone.     

Wide-Line 1H NMR and DSC study of phase states of mesomorphic states of 4′-n-alkoxy-4-biphenylcarbonitrile mesogens (n = 3 and 7)

4′-(Propyloxy)-4-cyanobiphenyl (3OCB) and 4′-(heptyloxy)-4-cyanobiphenyl (7OCB) have been studied in the temperature range 20–80°C by wide-line ¹H NMR and DSC. The ¹H NMR line shapes, half-widths, and second moments, as well as the relaxation characteristics of separate lines, are discussed. The DSC data are compared with the specific features of mesogenic transformations of these homologues and ¹H NMR data. At certain temperatures depending on the composition of alkyl moieties, a dynamically disordered fraction of molecules appear in solid crystals. These molecules are involved in the thermotropic transitions of 3OCB to isotropic liquid and of 7OCB to nematic liquid crystal. The temperature ranges, stabilities, and other characteristics of the transitions of 3OCB to isotropic liquid and of 7OCB to nematic liquid crystal were determined.     

Structure and Physicochemical Properties of Substituted Porphyrins

Reactions of substituted porphyrins: 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraphenylporphine, 2,3,7,8,12,13,17,18-octamethyl-5,10,15,20-tetraphenylporphine, and dodecaphenylporphine with organic bases (pyridine, piperidine, dimethylformamide, dimethyl sulfoxide) and acetic acid were studied by spectrophotometry. Acid-base interaction between porphyrins and organic bases and formation of ionic species in toluene solution containing an organic base were revealed for the first time. The effect of electronic and structural factors on the acid-base interactions of porphyrin ligands with organic bases is discussed. The stability constants were calculated for complexes of 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraphenylporphine with organic bases, and electronic absorption spectra of substituted porphyrins in basic organic solvents were recorded.     

Formation of phthalocyanines deprotonated forms and their interaction with Zn Ions in the system 1,8-diazabicyclo[5.4.0]undec-7-ene-acetonitrile at 298 K

The formation of deprotonated forms of tetra(t-butyl)phthalocyanine ((H₂ tButPc) and octa(pentoxy)-phthalocyanine (H₂OAmPc) in the system acetonitrile-1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) at 298 K was studied by the method of spectrophotometric titration. With increasing DBU concentration sequential formation occurs of both mono- and douby deprotonated forms. The introduction of pentoxy groups into the fused benzene rings leads to a significant decrease in the acidity of the tetrapyrrole macrocycle compared with the tert-butyl substitution. The interaction of douby deprotonated forms of the phthalocyanines with zinc diacetate leads to the formation of metal complexes, the chelation constant of the latter is shown to correlate with the acidity of NH-protons in the nucleus of the macrocycle. For the chelation of more acidic tetra(t-butyl)-phthalocyanine an equimolar concentrations of zinc diacetate is sufficient, while the less acidic octa(pentoxy)-phthalocyanine requires almost 6-fold excess.     

P-Vm-x Properties of Water-Dimethylformamide Mixtures at 278.15 K and Pressures of up to 100 MPa

The compressibility coefficients k = (v ₀ - v)/v ₀ of water-dimethylformamide (DMF) binary mixtures in the entire composition range at 278.15 K and pressures of up to 100 MPa were measured with a constant-volume piesometer. From the measured densities at atmospheric pressure and the coefficients k, the following quantities were calculated: specific and molar volumes of water-DMF mixtures at the examined parameters of state, excess molar volumes, partial molar volumes of the components, and variation with external pressure of the excess Gibbs energy of the water-DMF system. At all the pressures, the dependence k = f(x) (where x is the mole fraction of DMF in the mixture) passes through a minimum at x 0.2. The composition dependence of the specific volume of water-DMF mixtures also shows extrema, and its shape depends on the pressure. The partial molar volume of water at infinite dilution in DMF slightly depends on pressure.     

Synthesis of tetraphenylporphines with active groups in the phenyl rings. 5. Tetra(carboxymethylenoxyphenyl)porphines and their ethyl esters

Tetra(carboxymethylenoxyphenyl)porphines which are soluble in bases are prepared by hydrolysis of the ethyl esters of tetra(carboxymethylenoxyphenyl)porphines. The starting ethyl esters of the tetra(carboxymethylenoxyphenyl)porphines were synthesized by alkylation of tetra(oxyphenyl)porphines with ethylchloroacetate, as well as by condensation of pyrrole with ethyl esters of formylphenoxyacetic acids.See [1] for Communication 4.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1373–1377, October, 1989.