Persistent oxidation dications from twisted fluoranthenes, benzo[k]fluoranthene and dimethyldibenzo[j.l]fluoranthene: charge delocalization mode, tropicity, and formation of novel 8,8'-bifluoranthenyls. An NMR and theoretical study.

First examples of persistent oxidation dications from fluoranthene-PAHs namely 1,3,4,6,7,10-hexamethyl- 2 and 3,4-dichloro-1,6,7,10-tetramethylfluoranthene 3, benzo[k]fluoranthene 6, and 3,6-dimethyldibenzo[j,l]fluoranthene 9 are reported. Charge delocalization mode and tropicity in the resulting nonalternant dications are examined. Quenching of the superacid solutions of the dications resulted in the formation of novel 8,8'-bifluoranthenyls 2a-4a. AM1 was used as an initial guide for dication generation (DeltaDeltaH(f) degrees and ionization potentials) and for probing the structures of the crowded fluoranthene substrates and their bifluoranthenyls. In selected cases, the dications and their neutral precursors were calculated at the B3LYP/6-31G(d,p) level. Charge delocalization mode (difference in NPA charges) and DFT/GIAO-derived NMR chemical shifts were obtained for comparison with experiment; aromaticity was assessed via nucleus independent chemical shift (NICS) calculations.     

Energy conversion process from the photoexcited electronic states studied by the temperature lens and acoustic peak delay methods in solution

Ultrafast temperature rise after the deactivation of the electronically excited state of 2-hydroxybenzophenone in various solvents is investigated by two photothermal techniques; temperature lens and acoustic peak delay methods, and by the population grating technique. The results from these methods show that the thermalization process takes place by two phases; fast (<1 ps) and rather slow (30 ps) processes. From the solvent dependence of the thermalization rate, we suggest that these processes are related with the intermolecular interaction and the solvation structure around the photoexcited molecules.     

Modulated differential scanning calorimetry in the glass transition region. V. Activation energies and relaxation times of poly(ethylene terephthalate)s

Temperature-modulated differential scanning calorimetry is used to evaluate the kinetics of the glass transition from measurement of the first harmonic of the apparent, reversing heat capacity. The data are taken from quasi-isothermal experiments with negligible instrument lag, extrapolated to zero modulation amplitude. Equations based on irreversible thermodynamics that can be understood in terms of the hole theory of liquids are applied to measurements on amorphous, semicrystalline, and biaxially drawn poly(ethylene terephthalate)s (PET). The activation energy of amorphous PET decreases from 328 to 153 kJ/mol on crystallization and to 111 kJ/mol on orientation, and is correlated with an increase in the preexponential factor. After annealing of the crystallized samples below the glass transition temperature, the activation energy of the semicrystalline PET can recover beyond the level of amorphous PET, to 387 kJ/mol. The earlier observed decrease in enthalpy relaxation on crystallization is linked to this sharp decrease in activation energy. © 1996 John Wiley & Sons, Inc.     

Development of a new density functional program for all-electron calculation of proteins

In this article, we propose a new molecular orbital program for all-electron calculation of proteins which is based on density functional theory. To carry it out in a fully analytical way, we adopted the (pure-) analytical Xα method and modified it for saving a lot of memories for large-scale calculations. The recent software technology sophisticated in information science is inevitably applied to achieve calculations of large molecular systems. The program is coded by the object-oriented language C + +, its output is shown graphically, and the most of the procedures in this program are controlled through an efficient graphical user interface developed by ourselves. Such technology supports the safe construction of the huge software, the tidy representation of enormous data, and the ready control of complex calculations. Test calculations with various sizes of glycine polypeptides indicate that the computation time is proportional to the 1.7 powers of the number of residues. This result suggests that the all-electron calculations of proteins consisting of over 1000 atoms could be performed with distributed and/or massively parallel computers. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 245–256, 1997     

Radical ring-opening polyaddition of a bifunctional vinylcyclopropane bearing a spiroacetal moiety with dithiols

Radical polyadditions of vinylcyclopropane having spiroacetal moiety, 1,10-divinyl-4,8,12,15-tetraoxatrispiro[2.2.2.2.2.2] pentadecane ( 1 ), and various dithiols were examined. 1 was prepared by the reaction of 1,1-dichloro-2-vinylcyclopropane and pentaerythritol, and radical polyadditions of 1 and dithiols were carried out at 60 and 120°C for 20 h in the presence of an appropriate initiator (3 mol % vs. 1 ) in degassed sealed ampoules or at 20°C under photo irradiation by using a 400 W high-pressure mercury lamp. Poly( 1 ), pale yellow transparent viscous polymers was isolated by reprecipitation with ether containing a small amount of triethylamine to avoid hydrolysis of the polymer. The obtained polymers were soluble in chlorobenzene, DMF, and chloroform but insoluble in ether and n-hexane. The molecular weights of the polymers obtained from aliphatic dithiols were smaller than those from aromatic ones. The structure of the polymer was determined by comparing the NMR spectra with those of the model compounds, which were obtained by radical addition of 1 and benzyl mercaptan. The reaction proceeded through radical polyaddition of dithiol to 1 via radical ring-opening polymerization of the cyclopropane ring. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2487–2492, 1997     

近红外吸收菁染料光氧化反应机理的研究

本文选择了三种分子结构相同而母核杂原子不同的近红外吸收菁染料,对它们的光谱性能特征及光氧化稳定性能进行了研究。结果表明,具有三种不同母核杂原子的菁染料,其光氧化稳定性顺序为:苯并 唑>苯并噻唑>苯并硒唑。通过猝灭实验给出,在三种菁染料的光氧化反应机制中,具有反应活性的单线态氧和超氧负离子同时存在,其中单线态氧是导致菁染料褪色的主要因素。     

Thermolysis,photolysis, and oxidation of an overcrowded 1,3,2-dithiastannetane derivative

Reactions of a sterically crowded 1,3,2-dithiastannetane derivative bearing 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (=Tbt) and 2,4,6-triisopropylphenyl (=Tip) groups on the tin atom are described. Both thermolysis and photolysis of the 1,3,2-dithiastannetane [Tbt(Tip)SnS₂CPh₂] resulted in the formation of products derived from the corresponding stannanethione [Tbt(Tip)Sn=S], while the oxidation reaction by m -chloroperbenzoic acid gave a novel tincontaining heterocyclic system, an 1,2,4,5-oxadithiastannolane derivative.     

Cover Picture: Electrochemical Lossy Mode Resonance-based Fiber Optic Sensing for Electroactive Species (Electroanalysis 3/2023)

We present an electrochemical-lossy mode resonance (LMR) sensing method that detects refractive indices and electroactive species. The LMR peaks of indium-tin-oxide in the transmittance-wavelength spectra were significantly shifted as the applied potential between 1.0 and −0.5 V at 209 nm/V. The modulation was exploited for sensing the refractive index and electroactive species (ferrocyanide and methylene blue) in two ways: peak-wavelength tracking and potential scanning. The potential-scanning technique produced clear potential LMR peaks in the transmittance-potential spectra for the first time, which were corresponded to the external refractive index. Meanwhile, the limits of detection of ferrocyanide and methylene blue were 7.5 and 25.3 μM, respectively, in peak-wavelength tracking and 18.2 and 20.8 μM, respectively, in the potential scanning technique.