Excitation-wavelength Dependent Fluorescence of Ethyl 5-(4-aminophenyl)-3-amino-2,4-dicyanobenzoate

The excitation wavelength dependence of the steady-state and time-resolved emission spectra of ethyl 5-(4-aminophenyl)-3-amino-2,4-dicyanobenzoate (EAADCy) in tetrahydrofuran (THF) at room temperature has been examined. It is found that the ratio of the fluorescence intensity of the long-wavelength and short-wavelength fluorescence bands strongly depends on the excitation wavelength, whereas the wavelengths of the fluorescence excitation and fluorescence bands maxima are independent on the observation/excitation wavelengths. The dynamic Stokes shift of fluorophore in locally excited (LE) and intramolecular charge transfer (ICT) states has been studied with a time resolution about 30 ps. The difference between Stokes shift in the LE and ICT states was attributed to the solvent response to the large photoinduced dipole moment of EAADCy in the fluorescent charge transfer state. On this base we can state that, the relaxation of the polar solvent molecules around the fluorophore was observed

2,5-Bis[4-(dimethyl­amino)­phen­yl]-3,6-dimethyl­pyrazine

The title compound, C22H26N4, was prepared from p-dimethyl­amino­propiophenone in six steps. The mol­ecule has no crystallographic symmetry. The dihedral angles between the pyrazine ring and the phenyl rings are 35.81 (6) and 37.11 (8)°. The dimethyl­amino groups are essentially planar (sum of the bond angles at N = 359.3 and 359.9°) and nearly coplanar with the adjacent aromatic ring [dihedral angles = 5.54 (11) and 7.40 (3)°]. This effect and the short aniline C—N bonds can be rationalised in terms of charge transfer from the amino groups to the central pyrazine ring

2,7-Bis(2-nitro­phen­yl)-9-octyl-9H-carbazole

The title compound, C32H31N3O4, was obtained in a Suzuki coupling of carbazole diboronic acid and bromo­nitro­benzene. In the crystal, the mol­ecule adopts a non-symmetric conformation. The carbazole ring system is approximately planar [maximum deviation from the least-squares plane = 0.039 (2) Å]. The planes of the carbazole unit and the benzene rings subtend dihedral angles of 48.42 (7) and 41.81 (6)°. The dihedral angles between the planes of the nitro­phenyl rings and the nitro groups are 44.34 (19) and 61.64 (15)°. The crystal is built from two strands of parallel mol­ecules with inter­digitated octyl chains. These strands are symmetry related by a twofold screw axis

3-(9H-Carbazol-9-yl)-2H-chromen-2-one

The title compound, C21H13NO2, was prepared as an example of a new synthesis of carbazoles from a cyclic dibenzo-iodo­lium salt via a twofold Pd-catalysed aryl­ation of a primary amine. The two essentially planar π-subsystems [maximum deviations from the mean square plane of 0.038 (2) Å in the carbazole and 0.059 (2) Å in the coumarine unit] open a dihedral angle of 63.05 (4)°. Two mol­ecules form a centrosymmetrical pair connected via π–π inter­actions between the pyrrole and pyrone rings [centroid–centroid distance = 3.882 (1) Å] and one benzene of the carbazole and the pyrone unit [centroid–centroid distance 3.824 (1) Å]. The lattice is stabilized by C—H⋯O bridging to both coumarin O atoms

N,N-Dihexyl-4-[2-(4-nitro­phen­yl)vin­yl]aniline

The title compound, C26H36N2O2, was prepared by Horner olefination of p-dihexyl­amino­benzaldehyde and diethyl p-nitro­benzyl­phospho­nate. It crystallizes with two independent mol­ecules in the asymmetric unit. Both have similar geometries of the π-systems but the conformations of all hexyl chains are different. Whereas one hexyl chain of the first mol­ecule shows the typical all-anti conformation, the second is arranged in a gauche-anti-gauche-anti conformation with N—C—C—C, C—C—C—C, C—C—C—C and C—C—C—C torsion angles of −65.1 (4), 167.3 (3), 63.3 (4), and 179.4 (3)°. One of the hexyl chains in the other mol­ecule has an anti-anti-gauche-anti conformation [N—C—C—C, C—C—C—C, C—C—C—C and C—C—C—C torsion angles = 179.6 (3), −179.8 (3), −68.7 (5) and −178.8 (4)°], the other starts with an anti-gauche-gauche sequence. Molecules A and B are composed of five planar subunits. The angle sums around the N atoms are in the range 356 (2)–360.0 (2)°. Torsion angles between these segments do not exceed 4.9 (4)°, except for one of the alkyl chains each [molecule A = 26.2 (4)°; molecule B = −6.0 (4)°]. The high planarity of the molecules and the short aniline C—N bonds [1.385 (3) Å in molecule A and 1.378 (3) Å in molecule B] indicate a strong electronic coupling through the stilbene unit. One methylene group is disordered over two positions with an occupancy ratio of 0.72:0.28

Достоверность дублированных измерений энергетических переменных

In this article the control methods of reliability of measurements of power variables on Bayes’ criterion and multi-identification method of inexact measurements are developed.Разработаны методы контроля достоверности измерений энергетических переменных по критерию Байеса и многопризнаковый способ идентификации недостоверных измерений

(E,E,E,E)-2,3,5,6-Tetra­kis{2-[4-(dimethyl­amino)­phen­yl]ethen­yl}pyrazine

In the title compound, C44H48N6, the essentially planar mol­ecule [maximum deviation from the mean plane of the π system of 0.271 (3) Å] is located on a crystallographic centre of inversion. The almost planar (angle sums at N atoms = 357.6 and 357.1°) dimethyl­amino groups and short C—N bonds of the aniline groups [both 1.379 (4) Å] indicate strong electronic coupling between these groups and the central pyrazine ring

Directed energy transfer due to orientational broadenning of energy levels in photosynthetic pigment solutions

The directed non-radiative energy transfer through monomeric molecules of chlorophyll “a” and pheophytin “a” at high concentrations (c ~ 10⁻²) in a rigid matrix of polyvinylbutyral has been found by using the nanosecond laser spectrofluorimeter. The phenomenon is caused by orientational broadening of pigment molecular spectra owing to its interaction with a solvent. The observed temporal shift of the luminescence spectrum to the red region in a nanosecond time scale as well as the red shift of the time integrated spectrum at a high concentration of pigment molecules and the monotonic growth of the luminescence lifetime with a shift to the red region of the spectrum served as indications of the directed energy transfer in the sample. The non-radiative energy transfer from monomeric molecules towards aggregates is also directly demonstrated by the deformation of instantaneous luminescence spectra in the long-wavelength range (λ > 700 nm). The role and the possibility of the directed energy transfer between molecules with orientationally broadened spectra in the biological systems are discussed