In this paper we review dynamics and roughness of bonds in proteins on example of albumin, that is important from the physiological point of view. We have performed computer simulations of albumin chain. Statistics were collected by performing many simulations realizations for each experimental setting. We concentrate on hydrogen bonds, cation-π and π- π interactions and NP contacts. Histograms of hydrogen bonds length are positively skewed in contrary to histograms of interactions and HP contacts that are negatively skewed. Scaling exponents of power spectra of energies of bonds / interactions /contacts are in range -0.2 to -0.5 and significantly differ between various hydrogen bonds or interactions. Varying scaling of such spectra can be used to classify between distinct bonds or contacts. Concerning particular amino-acids, largest amount of HBO H20 bonds are between Glutamate (GLU) amino-acids and water particle, while large amount of HBO bonds are formed with Lysine (LYS). For HP contacts the mayor role plays Phenylalanine (PHE) and Leucine (LEU) amino-acids. From decay curves HBO H2O bonds decays in fastest rate, while HBO bonds and HP contacts at slowest rate. We present as well decay curves of bonds formed by particular amino-acids, that gives interesting results.

Gibbs free energies, based on DFT (Density Functional Theory) calculations, prove that enaminone (2-(anilinemethylidene)cyclohexane-1,3-dione) and ketamine (2-[(phenylimino)-methyl]cyclohexane-1,3-dione) are the most and least stable tautomeric forms of the studied systems, respectively. 1H and 13C NMR spectra prove that 2-(anilinemethylidene)cyclohexane-1,3-diones are the only tautomeric species present in dimethylsulfoxide solution (a very weak signal can be seen only for the p-methoxy derivatives). The zwitterionic character of these enaminones is strengthened by naphthoannulation and by the insertion of the electron-withdrawing substituent into the benzene ring (the latter weakens the intramolecular hydrogen bond in the compound). Substituent and naphtoannulation have no effect on the stability of the studied tautomers. Slight twisting of the benzene ring, with respect to the CArNC plane (seen in the crystalline state), was proven to also take place in vacuum and in solution.

The article presents applications of systems with power electronic converters, high voltage transformers, and discharge chambers used for nonthermal, dielectric barrier discharge plasma treatment of a plastic surface and decontamination of organic loose products. In these installations, the inductance of the high voltage transformers and the capacitances of the electrode sets form resonant circuits that are excited by inverters. The article presents characteristic features of the installations and basic mathematical relationships as well as the impact of individual parameters of system components. These converters with their output installations were designed, built, and tested by the authors. Some of the converters developed by the authors are manufactured and used in the industry.

2-Ethyl-2-(hydroxymethyl)-1,3-propanediol triacrylate was polymerized in the presence of squarylium dye and various onium salts. The onium salts under study are commercially available or may be easily synthesized and are characterized by light absorption properties below 300 nm and generate phenyl radicals upon blue light exposure. Due to these interesting properties the triacrylate polymerization can be efficiently carried out with or without the presence of any additional photoinitiator. The chemical mechanisms are investigated by steady state photolysis and nanosecond laser flash photolysis experiments. The new photoinitiators yielded a higher visible light photoinitiating polymerization effect than the commercial photoinitiator: camphorquinone/ethyl p-(dimethylamino) benzoate and camphorquinone/ N-methyldiethanolamine under experimental conditions.

ABSTRACTA few N‐alkoxypyridinium salts are developed as photoinitiators for efficient polymerization reactions. They are characterized by absorption properties below 300 nm, and generate alkoxy radicals on UV‐Vis light exposure. The squarylium dye was used as a blue‐light photosensitizer. Polymerization results are correlated with the photochemistry of N‐alkoxypyridinium salts. The quenching of the excited singlet state of squarylium dye by pyridinium salt and the formation of the semioxidized species of squaraine suggests an electron transfer from an excited dye to a coinitiator, and that the resulting oxygen‐centered radical initiates the polymerization process. The chemical mechanism was investigated by steady state photolysis and nanosecond laser flash photolysis experiments. Photoinitiating activity of new photoinitiators for initiation of polymerization of trimethylolpropane triacrylate in the UV‐blue light region was compared with photoinitiating ability of selected commercially available initiators. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2840–2850

Six N-alkoxypyridinium salts were synthesized, identified and used together with 1,3-bis(4-bromophenylamino) squarine as coinitiators in 2-component photoinitiating systems for radical polymerization of HOCH2CHEt(CH2OH)(2) triacrylate at 25 degrees C and light intensity 30 mW/cm(2) (wave length 300-500 nm) to det. the kinetics of photopolymerization. The 2-component systems squarine dye/N-alkoxypyridnium salts were found very efficient for initiation of the radical polymerization.

A novel squarylium dye possessing donor-pi-acceptor structure that features a fixed imine phenyl ring as an electron donor and 3,4-dihydroxycyclobut-3-ene-1,2-dione moiety as an electron acceptor was synthesized. The structure of the dye was elucidated by means of NMR and IR spectroscopy and elemental analysis. The compound was studied using steady-state absorption and emission spectroscopy, as well as the time-resolved spectroscopy. The measurements were carried out in solvents of different polarity. The dye absorbs in the visible light region about 400 nm and emits light with low fluorescence quantum yield, below 1 x 10(-3) M. An increases polarity of solvent results in a blue-shift of absorption band and red-shift of emission band, respectively.The rate constants of radiative and non-radiative deactivation of excited state depend on the viscosity of solvent used. The bimolecular quenching of excited singlet state of squaraine depends on the rate of diffusion process. (C) 2016 Elsevier Ltd. All rights reserved.

Three new hemicyanine dyes possessing donor-π-acceptor structure that features a fixed p-substituted phenyl ring as an electron donor and benzothiazolium moiety as an electron acceptor were synthesized. The structure of dyes was elucidated by using NMR and IR spectroscopy and elemental analysis. The spectroscopic properties have been investigated by spectroscopic experiments and time-dependent density functional theory (TD-DFT) calculations at the B3LYP/6-311++G(d,p) level of theory. The measurements and calculations were performed in five different polarity solvents. The strong absorption of all dyes in the range from 450 to 600nm is observed. The relationship between electronic absorption spectra of hemicyanine dyes and their molecular structure is also discussed. The molecular structure does not have large change during the intramolecular charge-transfer (ICT) process, which is confirmed by the quantum chemical calculations.

B3LYP/maug-cc-pVTZ and MP2/maug-cc-pVTZ calculations show that 3,4-dihydro-quinazoline and its 2- and/or 4-methyl and -phenyl substituted derivatives in solution (chloroform, DMSO, methanol) are only by 0.3 kcal/mol–2.2 kcal/mol more stable than the respective tautomeric 1,4-dihydroquinazolines (the available literature experimental stability data are not coherent). In the gas phase, 2- and/or 4-substituted tautomers of 3,4-dihydroquinazoline are also energetically preferred (B3LYP/maug-cc-pVTZ, MP2/maug-cc-pVTZ and CCSD/cc-pVDZ calculations lead to the same conclusion). In vacuum, 1,4-dihydro tautomer is by 0.1 kcal/mol–0.2 kcal/mol more stable only for unsubstituted dihydro-quinazoline. The observed tautomeric preference was found almost independent on substitution and solvent used. The optimization procedure used shows that the pyrimidine ring in dihydropyrimidines studied is not planar. Noncoplanarity of the 2-phenyl ring and C = N bond in the respective compounds studied is responsible for the weakened conjugation of these two moieties.

Density functional theory (DFT) calculations at the B3LYP/6-311+G(d,p) level show that 4,6-di(pyridin-2-yl)cyclohexane-1,3-dione is a labile compound. On the other hand, its dienolimine tautomer (4,6-di(pyridin-2-yl)cyclohaxa-1,3-diene-1,3-diol) seems stable enough to be present in vacuum. Alternatively the equilibriated species are (i) dienolimine and enolimine-enaminone ((6Z)-3-hydroxy-6-(pyridin-2(1H)-ylidene)-4-(pyridine-2-yl)cyclohex-3-enone) or (ii) dienolimine, enolimine-enaminone and dienaminone ((4Z,6Z)-4,6-di(pyridin-2(1H)-ylidene)cyclohexane-1,3-dione). Benzoannulation of the pyridine ring at position 5,6 was found to increase the contribution of the tautomers which contain the enaminone moiety. Energies of the transition states between the stable tautomers were also calculated in order to estimate activation energy of the proton transfer. Values of the geometry based harmonic oscillator model of aromaticity (HOMA) index and Laplacian of the electron density in the hydrogen bond critical point (based on quantum theory of atom in molecules) shows that the enaminone moiety in the tautomers studied are stabilized by stronger intramolecular hydrogen bond than this present in the enolimine moiety.

1 H, 13 C, 15 N and 17 O NMR chemical shifts are used for the characterization of the intramolecular interactions in several nitramines of the Me 2 N-G-NO 2 type. The charge of lone electron pair of the amino group in N , N -dimethylnitramine, N , N -dimethyl-2-nitroethenamine, N , N -dimethyl- p -nitroaniline, 4-nitro-β-dimethylaminostyrene, 4- N , N -dimethylamino-β-nitrostyrene, 4-( N , N -dimethylamino)-4′-nitrobiphenyl, and 4-( N , N -dimethylamino)-4′-nitrostilbene is transferred not only to the nitro oxygens, but also to the vinylene and benzene carbons of the G spacer and to N -methyl carbons as well. Decreased nuclear shielding is found to be qualitatively related to the decreased atomic charge around a nucleus. This finding was further verified and quantified by comparison of the NMR data with those obtained by ab initio quantum chemical calculations. 17 O NMR chemical shift changes seem to be more significant when the interacting NMe 2 and NO 2 groups are separated by a short spacer. On the other hand, 15 N NMR chemical shifts suggest that a decrease of the charge at the amino nitrogen is not related to the length of the spacer alone. A lack of the linear dependence between the 17 O nitro and 15 N amino chemical shifts suggests that the charge lost by the amino nitrogen was only partially gained by the oxygens in the nitro group. The increased shieldings of the aryl carbons in 4-( N , N -dimethylamino)-4′-nitrobiphenyl indicate that atoms of the p , p -biphenylene spacer also gain some charge originating from the amino nitrogen. 3 J H,H spin–spin coupling constant shows that among different vinylene compounds, the charge transfer to the nitro group is practically effective only in N , N -dimethyl-2-nitroethenamine where the bond between the vinylene carbons is significantly of low order by character. The calculated Natural Population Analysis (NPA) data confirms that except the nitro oxygens, other atoms that receive the negative charge lost by NMe 2 in the compounds studied are the aryl and N -methyl carbons.

Structural data for five nitroamines of general formula Me2N–G–NO2 show effectiveness of the ground-state charge transfer to be most and least efficient in N,N-dimethylnitramine and in 4-N,N-dimethylamino-β-nitrostyrene, respectively. Electron-donor power of the amino nitrogen atom in the latter compound is less than that in 4-nitro-β-N,N-dimethylaminostyrene (these two compounds are isomers). Natural population analysis shows that the charge transfer from the amino to the nitro oxygen atoms is most effective in N,N-dimethylnitramine, Me2N–NO2. The nitro oxygen atoms are not the only acceptors of the negative charge lost by the amino nitrogen atom. The nitro group in two substituted nitrobenzenes studied was found to be independent on substituent (nitro group attached to the benzene ring withdraws a constant electron density regardless the substitution).

The 2-[1H]-pyridone/2-hydroxypyridine tautomeric pair and its 6-substituted complexes have been studied with the use of DFT(M05) method. The intermolecular interaction energy has been calculated and discussed in the light of secondary interaction concept. The attractive secondary interactions of O/NH and O/OH type and OH/NH and OH/OH repulsions have been analyzed in terms of stabilizing or destabilizing influence on intermolecular behavior. The transition states of the double proton transfer reaction have been found and the energy of activation has been determined. The activation energy of the proton transfer reaction, geometry of the complexes and transition states show NH(2) and/or OH groups influence the properties of complexes and transition states. The HOMA index of aromaticity was applied to describe the π-electron delocalization in the heterocyclic rings.

2011 Elsevier B.V. All rights reserved. Although simple b-diketones equilibriate only with their ketoenol tautomers, instable pyridin-2-yl-b-diketones may compete with more than three different prototropic forms [1,2]. There are many interesting compounds carrying the methylcarbonylpyridin-2-yl moiety in their molecules. In this note we report the results of quantum-chemical calculations concerning of 2,7di(pyridin-2-yl)hexahydronaphthalene-1,8-dione (1PKKP, Scheme 1) and 2,7-di(quinolin-2-yl)hexahydronaphthalene-1,8-dione (2PKKP). Multiple basic (nitrogen and oxygen atoms) and acidic (methylene hydrogen atoms) centers present in these molecules enable these compounds to exist in 12 tautomeric forms (Scheme 1). Full geometry optimizations for all studied systems have been carried out using Gaussian software package [3]. Computations for the isolated molecules were performed using B3LYP functional and 6-31+G(d,p) basic set. The frequencies were calculated at the same level (no imaginary frequencies). The DFT calculated energies (Table 1) show that the most stable tautomers of 1 are the enaminone 1EKOP2 and dienol 1POOP2. It was found that the benzene ring in derivates 2 completely changes tautomeric preferences (2EKKE is the most stable tautomer). Comparison with 1,5-bis(pyridin-2-yl)and 1,5-bis(quinolin-2yl)pentane-2,4-diones (1POOP1, 1EOKP and 2EKKE, 2EKOP2, respectively were their most stable tautomers [1]) shows that although stiffening of the molecule affects the studied tautomeric preferences, the same forms are still among the most stable. The studied tautomers can be stabilized by three different hydrogen bonds, i.e. by N–H O, O–H N and O–H O. The HOMA (Harmonic Oscillator Model of Aromaticity) [4] values (Table S1 in Supplementary Materials) show that N–H O interaction in 1EKOP2 and 2EKKE is of RAHB (Resonance Assisted Hydrogen Bond) type [5–8]. The Gaussian procedure of geometry optimization precludes calculations to be done for such labile forms as 1EOKP, 2EOKP and 2EOOP. Spontaneous proton transfer in these extremely unstable species transforms them automatically into more stable systems. Thus, 1EOKP was converted to 1EKOP2, 2EOKP to 2EKOP2 and 2EOOP to 2EOKE.

The spectroscopic properties of series homodimmeric hemicyanine dyes based on (p-N,N-dimethylaminostyryl)benzothiazolium, (p-N,N-dimethylaminostyryl)benzoxazolium, (p-N,N-dimethylaminostyryl)-2,3,3-trimethyl-3H-indolium residues were determined. The absorption and fluorescence spectra of the dyes under study were measured in different polarity solvents at room temperature. On the basis of the solvatochromic behavior the ground state (mu(g)) and excited state (mu(e)) dipole moments of bis-(N,N-dimethylaminostyryl) derivatives were evaluated. The dipole moments (mu(g) and mu(e)) were estimated from solvatochromic shifts of absorption and fluorescence spectra as function of dielectric constant (epsilon) and refractive index (n) of applied solvents. The absorption and fluorescence spectra are only slightly affected by the solvent polarity. The analysis of solvatochromic behavior of the fluorescence spectra as a function of Delta f(epsilon, n) revealed that the emission occurs from a high polarity excited state. The large dipole moment changes along with the red-shifted fluorescence, as the solvent polarity is increased, demonstrates the formation of an intramolecular charge transfer state (ICT). Six bichromophoric hemicyanine dyes, possessing benzothiazole, benzoxazole or indolinium group linked by 5 or 10 methylene groups were evaluated as fluorescence probes applied for monitoring of the polymerization process. The study on the changes in fluorescence intensity and spectroscopic shift of studied compounds were carried out during photochemically initiated polymerization of 2-ethyl-2-(hydroxymethyl)-propane-1,3-diol triacrylate (TMPTA). (C) 2010 Elsevier B.V. All rights reserved.

Aggregation of 2-acylaminopyridines and their 6-methyl derivatives in chloroform solution was studied by (1)H, (13)C, and (15)N NMR spectroscopies. The results were compared with (13)C and (15)N CPMAS NMR and IR spectral as well as with X-ray structural data. Intermolecular interactions in solution and in solid state were found to have a similar nature. Relatively strong N(amide)-H···N(pyridine) intermolecular hydrogen bonds enable dimerization to take place. Steric interactions in N-pivaloyl- and N-1-adamantylcarbonyl as well as that caused by the 6-methyl group hinder formation of the dimeric aggregates stabilized by the N(amide)-H···N(pyridine) intermolecular hydrogen bonds. In general, the DFT optimized geometries of the aggregates in chloroform solution are in agreement with the X-ray crystal structures. Wavenumbers of the stretching vibration band of the C═O group were also found indicative of the type of hydrogen bond present in the solid state.

8-Acetyl- and 8-benzoyl-2-(quinolin-2-yl) derivatives of 1,3-diketones were studied from point of view of their tautomeric preferences. Effective electron delocalization and strong hydrogen bonds were found to be responsible for high stability of the enaminone form (the most stable tautomer). Density functional theory (DFT) calculations prove that enolimine and ketimine species are less favored. Contribution of the zwitterionic resonance structures to the enaminone form is most significant in 2-(quinolin-2(1H)-ylidene)-2H-indene-1,3-dione derivatives. Formation of the bifurcated hydrogen bonds was found to take place only in 8-acetyl derivatives. One of these bonds is of the RAHB (Resonance Assisted Hydrogen Bond) type. There is a steric interaction of the pyridine β-hydrogen and carbonyl oxygen atoms in the enaminone tautomers.