Electret Materials Based on Fluoropolymers Modified with Vanadium- and Phosphorus-Containing Structures

Russian Journal of Applied Chemistry - Organo-inorganic composite materials based on films of polytetrafluoroethylene and tetrafluoroethylene–hexafluoropropylene copolymer, modified with...     

Photo- and thermochromic mannich bases. 1. Mannich bases from 3,5-di-tert-butyl-4-hydroxybenzaldehyde and 2-naphthols

Mannich bases exhibiting photo- and thermochromic properties in solutions were synthesized from 3,5-di-tert-butyl-4-hydroxybenzaldehyde and 2-naphthols. An investigation of an acetyl derivative of methylenequinone, modeling a product of photo- and thermochromic transformations, proved that the color change of solutions of the Mannich bases is due to reversible dissociation into colored methylenequinones and morpholine. On the basis of data of x-ray diffraction analysis of one of the Mannich bases, characteristics of their molecular structure were determined, and reasons were stated for their effect on the dissociation mechanism.     

Unusual synthesis,structure, and thermochromic properties of novel sterically hindered cyclohexadienes

Oxidation of 4-[-morpholino--(2-hydroxyphenyl)]methyl-2,6-di-(tert-butyl)-phenol (I) follows an unusual course, with formal loss of the benzyl carbon atom, to give 2,6-di(tert-butyl)-4-morpholino-4-(2-hydroxyphenyl)cyclohexa-2,5-dienone (II), which is thermochromic in solution. This property is due to the dissociation of (II) into morpholine and 3,5-di(tert-butyl)-2,4-diphenoxyquinone. The structure of (II) was established directly by x-ray diffraction, which enabled its conformational features to be related to its thermochromic properties. An x-ray examination of 3,3,5,5-tetra(tertbutyl)-2,4-diphenoquinone (X), together with the direct synthesis of the thermochromic analog of (II) (2,6-di(tert-butyl)-4-morpholino-4-[2-hydroxy-3,5-di(tert-butyl)phenyl]cyclohexa-2,5-dienone) (XI) from (X) and morpholine, confirmed the proposed mechanism of thermochromic dissociation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1121–1129, May, 1991.The authors thank V. I. Minkin and A. S. Morkovnik for participating in discussions of this work.     

Geometry changes of a Cu(I) phenanthroline complex on photoexcitation in a confining medium by time-resolved X-ray diffraction

Using a stroboscopic technique, in which the molecule is repeatedly excited and the structural change is probed more than 5000 times per second immediately after excitation, we performed a 16 K time-resolved single-crystal study of the microsecond lifetime triplet state of the Cu(I)phenanthroline derivative[Cu(I)(dmp)(dppe)][PF6] (dppe = 1,2-bis(diphenylphosphino)ethane). The geometry changes on excitation differ for the two symmetry-independent molecules, but are in the same direction as calculated for an isolated reference molecule, although the flattening distortion in the crystal is significantly smaller, implying that the reorganization energy is greatly affected by the confining medium.     

Shedding light on the structure of a photoinduced transient excimer by time-resolved diffraction

Time-resolved single-crystal diffraction performed with synchrotron radiation shows that the 53(1) micros phosphorescent state, generated in the crystalline phase of trimeric {[3,5-(CF3)(2)Pyrazolate]Cu}(3) molecules by exposure to 355 nm of light at 17 K, is due to the formation of an excimer rather than the shortening of the intramolecular Cu...Cu distances within the trimeric units, or the formation of a continuous chain of interacting molecules. One of the intermolecular Cu...Cu distances contracts by 0.56 Angstroms from 4.018(1) to 3.46(1) Angstroms;, whereas the interplanar spacing of the trimers is reduced by 0.65 Angstroms; from 3.952(1) to 3.33(1) Angstroms. Density-functional theory calculations support the formation of a Cu...Cu bond through the intermetallic transfer of a Cu 3d electron to a molecular orbital with a large 4p contribution on the reacting Cu atoms.     

Nonstationary processes in a diffraction-output orotron

The nonlinear dynamics of an orotron with diffraction output is studied. The evolution of the longitudinal field distribution is described by means of a parabolic equation subject to the condition of zero reflection at the collector end of the interaction space. For stationary regimes, the regions of high efficiency are delineated on the parameter plane, with the parameters being the departure from the critical frequency and the reduced length of the interaction space. From numerical results, the parameter plane is divided into the regions of stationary operation, periodic self-modulation, and stochastic self-modulation. It is demonstrated that self-modulation oscillating modes can be obtained most easily if the effective bounce frequency slightly exceeds the cutoff frequency, with the former being the blinking frequency of the dipole comprising an electron and its reflection in the regularly corrugated slow-wave guide.     

Response of a gyrotron to small-amplitude low-frequency-modulated microwaves reflected from a plasma

Experiments in the L-2M stellarator revealed the intense noise modulation of the gyrotron power and the change in its mean value under the action of the noise modulation of radiation reflected from the plasma column. The effect observed is explained in terms of the resonant locking of the gyrotron self-oscillations due to wave reflection from the fluctuating plasma load.     

Classification of soliton solutions in an infinite-dimensional phase space on the basis of the theory of dynamical systems

Theoretical and Mathematical Physics -