Results 1 - 10 of 68174
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[en] The presently known approaches to the synthesis of non-symmetrically substituted phthalocyanines of the A3B and A2B2 types are surveyed. The prospects for the use of these compounds for the synthesis of binuclear and heteronuclear complexes and phthalocyanine oligomers and polymers are demonstrated.
[en] To gain insight into how the electronic properties of discotic organic materials may be modified through substitution, the reorganization energy and the charge mobility of metal free phthalocyanine, and of several mono-substituted derivatives, are studied by electronic structure methods. It is found that the reorganization energy of phthalocyanine is not significantly changed by substitution on an outer phenyl ring, but is more strongly influenced when the inner crown amine ring is substituted. The relationship between reorganization energy and substituent is studied through the use of; substituent constant, HOMO energy, and geometry relaxation. The computed charge mobility shows stronger relationship to coupling matrix element than reorganization energy. A hybrid computational screening method in which the reorganization energy is calculated at the DFT level and the coupling matrix element is calculated at the AM1 level shows good predicting power for trends in charge mobility at reduced computational expense.
[en] Highlights: • Amine and carboxyl plasma modification of PCL nanofibers is compared. • The cell adhesion and proliferation on modified PCL nanofibers are studied. • The influence of surface chemistry and wettability of plasma coated PCL nanofibers is described. The plasma modification of biodegradable nanofibers is of great interest for improvement of their biocompatibility. However, there are no systematic studies regarding the influence of plasma polymer deposition onto the surface of nanofibers to improve cell adhesion. In the present study, homogenous and reproducible modification of polycaprolactone (PCL) nanofibers by amine and carboxyl/anhydride groups was achieved. The concentration of amines NH2/C and C(O)O contribution were up to 2.9 and 14.1%, respectively. Regardless the plasma conditions, the deposition of amine and carboxyl-anhydride plasma coatings onto the PCL nanofibers sufficiently improved the cell adhesion and viability, as was evidenced by microscopy observations and ATP assay results. It should be emphasized that the deposition of negatively charged carboxyl-anhydride coatings resulted in slightly better cell adhesion compared to the positively charged amine plasma coatings, unlike the widespread opinion that COOH modification has less effect on myoblasts adhesion.
[en] The nuclear spin-lattice relaxation of methyl-protons in (TMTSF)2ClO4 is measured versus temperature between 330 and 40 K. The relaxation from the hyperfine coupling to the itinerant electrons is found to be dominant above 200 K. Similar conclusions apply to (TMTSF)2PF6. At 300 K two regimes of relaxation are identified versus magnetic field: (i) a low-field regime (2-25) kOe where l/T1 is field independent and (ii) a field regime above 25 kOe where fitting the data with a l-D diffusion law leads to consistent values of hopping rates along a and b directions. By comparison with earlier measurements on TTF-TCNQ and HMTSF-TCNQ it is concluded that the transverse coupling of (TMTSF)2X is intermediate between that of the two-chain conductors
[en] The model of the nanoobject electron structure (piles with packaging defects) from the lead phthalocyanine molecules (PbPc) is proposed. The calculation by the molecular orbital method shows the 0.6e charge transport from the Pb atom onto the molecule macrocyclic ring and makes it possible to represent the nanostructure in form of a nanotube filled with metal. The earlier observed effect of the electrical change over in the PbPc films is quantitatively interpreted for the first time
[ru]Предлагается модель электронной структуры нанообъекта (стопки с дефектом упаковки) из молекул фталоцианина свинца (PbPc). Расчет методом молекулярных орбиталей показывает перенос заряда 0,6е с атома Pb на макроциклическое кольцо молекулы и позволяет представить наноструктуру в виде заполненной металлом нанотрубки. Впервые количественно интерпретирован наблюдавшийся ранее эффект электрического переключения в пленках PbPc
[en] The multi-instability of the electronic structure of (EDO-TTF)2PF6, where EDO-TTF means ethylene-dioxytetrathiafulvalene, is reviewed. This complex showed the metal-insulator transition at 280 K associated with distinct molecular deformations. The mechanism is interpreted as the cooperation of Peierls transition, charge ordering, and the order-disorder transition of the countercomponent. The charge ordering pattern in the low-temperature phase is of the novel [0, 0, 1, 1] type. The sensitivity of the electronic state to external perturbations is demonstrated applying not only static but also instantaneous stimuli. In the latter case, the photo-induced phase transition is ultrafast and highly efficient. One photon causes the transition of several hundreds of donor molecules in the low-temperature phase to relax into a highly conducting metastable state within about 1.5 ps. In the early stage of the transient state, the charge ordering of the [1, 0, 1, 0] type occurs. As for the chemical modifications of this material, the partial deuteration of this complex increases the metal-insulator transition temperature. The introduction of a methyl group greatly modulates the electronic structure of the complex, i.e. (methyl-EDO-TTF)2X (X=BF4, ClO4) shows a two-dimensional electronic structure. The working hypotheses for developing the systems with multi-instability are described. (topical review)