Effect of molecular structure and hydrogen bonding on the fluorescence of hydroxy-substituted naphthalimides

Fluorescence properties of hydroxy-naphthalimides were studied in methylene chloride in the absence and the presence of hydrogen-bonding additives. The position of the HO-substituent only slightly affects the radiative rate, however, the triplet yield and the rate of the radiationless processes are considerably higher for the 3-hydroxy derivative. Addition of nitrogen-heterocyclic compounds leads not only to hydrogen-bonding in the ground state but also Ñuorescence quenching. The parallel change throughout the series of the hydrogen-bond acceptors between the proton affinity and the rate constants of dynamic quenching indicates that proton displacement plays a crucial role in the excited hydrogen-bonded complexes. Interaction of hydroxy-naphthalimides with pyridine and benzoxazole results in rapid radiationless deactivation from the singlet excited state, whereas intense emission as well as long Ñuorescence lifetime characterize imidazole and pyrazole complexes. The dual emission of the imidazole complexes observed in solvents of medium polarity is assigned to two conformers which differ in the extent of the proton shift along the hydrogen-bond

Ion pair formation via photoinduced proton transfer in excited hydroxynaphthalimide-N-methylimidazole hydrogen bonded complex: effect of temperature and viscosity on dual fluorescence

The kinetics of photoinduced processes in the hydrogen bonded complex between N-methyl-3- hydroxynaphthalimide and 1-methylimidazole was studied in a wide temperature range in ethyl acetate and glycerol triacetate. The proton transfer within the excited complex was found to be very fast because of its negligible activation energy. The fairly intense dual Ñuorescence was assigned to hydrogen bonded and solvent separated ion pairs. Kinetic parameters for the various deactivation pathways of these excited species were derived from the combined analysis of the steady-state and the time-resolved Ñuorescence results. The Arrhenius pre-exponential factor of the transition from the solvent separated into the hydrogen bonded ion pair proved to be more than two orders of magnitude larger in glycerol triacetate compared with that in ethyl acetate, whereas the other processes showed less viscosity dependence. The radiationless energy dissipation rate of the hydrogen bonded ion pair was insensitive to the experimental conditions. However, thermal enhanced internal conversion was observed for the solvent separated ion pair

Development of power conversion devices for complexes of automation and stabilization of electric power supply systems for spacecraft

В статье рассматривается развитие силовых преобразовательных устройств для комплексов автоматики и стабилизации систем электропитания космических аппаратов. Приведены примеры построения различных комплексов автоматики и стабилизации. Проведен их сравнительный анализ. Определены основные современные принципы построения КАС и СЭП КА.The article deals with the development of power conversion devices for automation and stabilization systems for electrical power supply systems for space vehicles. Examples of the construction of various automation and stabilization complexes are given. Their comparative analysis is carried out. The main modern principles of construction of ASC and EPS SPACECRAFT are determined

Nanoparticle formation of chitosan induced by 4-sulfonatocalixarenes: utilization for alkaloid encapsulation

Spontaneous formation of positively charged nanoparticles was observed upon mixing more than stoichiometric amount of chitosan with 4-sulfonatocalix[8]arene (SCX8) in acidic solution. The particle size did not change with SCX8 concentration, polymer chain length, and the degree of deacetylation at 0.002 ≤ SCX8/chitosan ≤0.043 molar ratios in 0.01 M HCl. However, larger aggregates were produced when chitosan concentration was increased. The most stable nanoparticles with 160 nm diameter and narrow size distribution were obtained at pH 4 using low molecular weight chitosan. These particles encapsulated coralyne with more than 90 % entrapment efficiency and 15 % loading capacity. A loading ratio of [coralyne]/[SCX8] = 1.7 was achieved without any stability loss. 4-Sulfonatocalix[4]arene induced the formation of slightly smaller nanoparticles than its homologs comprising 6 or 8 phenol units. © 2016, Springer-Verlag Berlin Heidelberg

4-Sulfonatocalixarene-induced nanoparticle formation of methylimidazolium-conjugated dextrans: Utilization for drug encapsulation

Methylimidazolium side groups were grafted via ether linkage to dextran and the self-assembly of these polymers with 4-sulfonato-calix[n]arenes (SCXn) was studied in aqueous solutions. Dynamic light scattering and zeta potential measurements revealed the mixing ratio ranges of the constituents where stable nanoparticles could be created. The macrocycle size of SCXn and the molecular mass of the polymer barely affected the nanoparticle diameter, but the lowering of the imidazolium degree of substitution substantially diminished the stability of the associates. The pH change from neutral to acidic also unfavourably influenced the self-organization owing mainly to the decrease of the SCXn charge. Cryogenic transmission electron microscopy images proved the spherical morphology of the nanoproducts in which the stoichiometry of the constituents was always close to the one corresponding to charge compensation. The flexible and positively charged dextran-chains are compacted by the polyanionic SCXn. Coralyne, a pharmacologically important alkaloid was efficiently embedded by self-assembly in the produced nanoparticles reaching 99% association efficiency. © 2019 Elsevier Lt

Crystal and molecular structure ofN-phenyl substituted 1,2-, 2,3- and 1,8-naphthalimides

The three structures were solved by direct methods and refined by full-matrix least-squares procedure. 2-phenyl-1 H-benz[f]isoindole-1,3(2 H)-dione, (compound 1): orthorhombic, space group Pcab, a = 7.618(1) Angstrom, b = 11.717(2) Angstrom, c = 28.540(4) Angstrom, V = 2547.4(7) Angstrom(3), Z = 8 and d = 1.425 Mg m(-3), R = 0.038 (Rw = 0.038) for 190 parameters and 820 observations with I > 2.5 sigma(I). 2-phenyl-1 H-benz[e]isoindole-1,3 (2 H)-dione (compound 2): orthorhombic, space group Pc2(1)b, a = 6.7042(9) Angstrom, b = 7.4589(9) Angstrom, c = 26.441(7) Angstrom, V = 1322.4(4) Angstrom(3), Z = 4 and d = 1.373 Mg m(-3), R = 0.037 (Rw = 0.032) for 190 parameters and 1186 observations with I > 3 sigma(I). 2-phenyl-1 H-benz[de]isoquinoline-1,3(2 H)-dione (compound 3): monoclinic, space group C2/c, a = 13.501(3) Angstrom, b = 13.212(4) Angstrom, c = 8.305(2) Angstrom, beta = 116.24(2 degrees, V = 1329(9) Angstrom(3), Z = 4, and d = 1.366 Mg m(-3), R = 0.038 (Rw = 0.033) for 71 parameters and 754 observations with I > 3 sigma(I). The plane of the N-phenyl substituent has an axis which lies in the plane of the naphthalimide part and passes by the carbon atom bound to the nitrogen atom and by the carbon in para position. It makes a dihedral angle with the plane of the naphthalimide moiety of 59.2 degrees, 46.5 degrees and 69.4 degrees for the compounds 1, 2 and 3 respectively. This difference in geometry between the three molecules brings new insights into their spectroscopic properties

Reversible Nanoparticle–Micelle Transformation of Ionic Liquid–Sulfonatocalix[6]arene Aggregates

The effect of temperature and NaCl concentration variations on the self-assembly of 1-methyl-3- tetradecylimidazolium (C14mim+) and 4-sulfonatocalix[6]- arene (SCX6) was studied by dynamic light scattering and isothermal calorimetric methods at pH 7. Inclusion complex formation promoted the self-assembly to spherical nanoparticles (NP), which transformed to supramolecular micelles (SM) in the presence of NaCl. Highly reversible, temperature-responsive behavior was observed, and the conditions of the NP−SM transition could be tuned by the alteration of C14mim+:SCX6 mixing ratio and NaCl concentration. The association to SM was always exothermic with enthalpy independent of the amount of NaCl. In contrast, NPs were produced in endothermic process at low temperature, and the enthalpy change became less favorable upon increase in NaCl concentration. The NP formation was accompanied by negative molar heat capacity change, which further diminished when NaCl concentration was raised

Thoracoscopic vs. catheter ablation for atrial fibrillation: long-term follow-up of the FAST randomized trial

Aims: Our objectives were to compare effectiveness and long-term prognosis after epicardial thoracoscopic atrial fibrillation (AF) ablation vs. endocardial catheter ablation, in patients with prior failed catheter ablation or high risk of failure. Methods and results: Patients were randomized to thoracoscopic or catheter ablation, consisting of pulmonary vein isolation with optional additional lines (2007–2010). Patients were reassessed in 2016/2017, and those without documented AF recurrence underwent 7-day ambulatory electrocardiography. The primary rhythm outcome was recurrence of any atrial arrhythmia lasting >30 s. The primary clinical endpoint was a composite of death, myocardial infarction, or cerebrovascular event, analysed with adjusted Cox proportional hazard ratios (HRs). One hundred and 24 patients were randomized with 34% persistent AF and mean age 56 years. Arrhythmia recurrence was common at mean follow-up of 7.0 years, but substantially lower with thoracoscopic ablation: 34/61 (56%) compared with 55/63 (87%) with catheter ablation [adjusted HR 0.40, 95% confidence interval (CI) 0.25–0.64; P < 0.001]. Additional ablation procedures were performed in 8 patients (13%) compared with 31 (49%), respectively (P < 0.001). Eleven patients (19%) were on anti-arrhythmic drugs at end of follow-up with thoracoscopy vs. 24 (39%) with catheter ablation (P = 0.012). There was no difference in the composite clinical outcome: 9 patients (15%) in the thoracoscopy arm vs. 10 patients (16%) with catheter ablation (HR 1.11, 95% CI 0.40–3.10; P = 0.84). Pacemaker implantation was required in 6 patients (10%) undergoing thoracoscopy and 3 (5%) in the catheter group (P = 0.27). Conclusion: Thoracoscopic AF ablation demonstrated more consistent maintenance of sinus rhythm than catheter ablation, with similar long-term clinical event rates