(μ‐Tri‐tert‐butoxysilanethiol­ato)­bis[(tetra­hydro­furan)lithium(I)] and catena‐poly[[bis­(μ‐tri‐tert‐butoxy­silanethiol­ato)dilithium(I)]‐μ‐dimethoxy­ethane]: solvent coordination as the structure‐forming factor

The title compounds, μ‐(tri‐tert‐butoxy­silanethiol­ato‐κ²S:S)‐bis[(tetra­hydro­furan‐κO)lithium(I)], [Li₂(C₁₂H₂₇O₃SSi)₂(C₄H₈O)₂], (I), and catena‐poly[[bis­(μ‐tri‐tert‐butoxysilanethiol­ato)‐1:2κ²S;1κS:2κS,O‐dilithium(I)]‐μ‐dimethoxy­ethane‐κ²O:O′], [Li₂(C₁₂H₂₇O₃SSi)₂(C₄H₁₀O₂)]_n, (II), were obtained by the reaction of tri‐tert‐butoxy­silanethiol with metallic lithium. The crude product, when recrystallized from tetra­hydro­furan (THF) yields (I), and when recrystallized from 1,2‐dimethoxy­ethane (DME) gives (II). Compound (I) forms centrosymmetric dimers in the solid state with an Li₂S₂ central core, whereas (II) forms infinitely long chains, in which the centrosymmetric dimeric units are linked together by the bidentate DME ligand (also residing on an inversion centre), thus forming a coordination polymer. The formation of a one‐dimensional structure in (II) is a consequence of replacement of a monodentate THF solvent mol­ecule with a bidentate DME mol­ecule.     

Kinetics of Interfacial Polycondensation of Bisphenols with Isophthaloyl Chloride

Reaction rates of interfacial polycondensation of bisphenol A and chlorobisphenol II with isophthaloyl chloride were investigated. Rate constants and activation energies were determined The reaction rate was found to depend on stirring speed, catalyst, type of bisphenol, and temperature.     

Influence of chloroform on crystalline products yielded in reactions of 5,10,15,20‐tetraphenylporphyrin with HCl and copper(II) salts

Chloroform was found to occupy the lattice of the protonated porphyrin and to promote crystallization of a different polymorphic form of a metalloporphyrin. The structure of 5,10,15,20‐tetraphenylporphyrin‐21,23‐diium dichloride chloroform octasolvate, C₄₄H₃₂N₄²⁺·2Cl⁻·8CHCl₃, (I), in the solid state is described and compared with related solvates. The porphyrin macrocycle displays a distorted saddle shape, with chloride anions above and below the ring. Seven chloroform molecules are bound via C—H...Cl hydrogen bonds, while the link with the eighth solvent molecule is weaker. A new monoclinic polymorph of (5,10,15,20‐tetraphenylporphyrinato)copper(II), [Cu(C₄₄H₂₈N₄)], (II), crystallized from chloroform, is also presented.     

Surface relief grating formation in luminescent dye doped photochromic polymer containing azobenzene side groups

We study the formation of a surface relief grating and photoluminescence in a thin layers of a photochromic polymer doped with the luminescent dyes 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole and Rhodamine 6G. Surface topography measurements via Atomic Force Microscopy confirmed the existence of a surface relief grating with amplitudes as high as 650 nm both for doped and undoped photochromic polymers. Spectroscopic measurements carried out for polymers containing luminescent dyes have shown efficient photoluminescence and amplified spontaneous emission which is characteristic for gain media.     

Preparation of 1-[ω-(1,4,5,6-Tetrahydropyrimidin-2-Yl)Alkyl]Thymines

One-stage preparation of 1-[ω-(1,4,5,6-tetrahydropyrimidin-2-yl)alkyl]-thymines from 1-(ω-cyanoalkyl)thymines and a 1:1-mixture of 1,3-diaminopropane and ethanol saturated with hydrogen sulfide is described. 1-(2-Cyanoethyl)-thymine gave a facile reversal of the Michael reaction to thymine under the conditions used. The reaction of 1,3-bis(3-cyanobenzyl)thymine with the above reagent produced 1,3-bis[3-(1,4,5,6-tetrahydropyrimidin-2-yl)benzyl]thymine.     

4-(Cyclic Amidino)phenols - Preparation and Use In A Diamidine Synthesis

The Pinner synthesis was applied to the preparation of 4-(cyclic amidino)phenols in high yields from readily available 4-hydroxybenzimidic acid methyl ester hydrochloride and diaminoalkanes. An alternative attempt was made to convert 4-(hydroxy)thiobenzamide to 4-(1,4,5,6-tetrahydro-5-hydroxy-2-pyrimidiyl)phenol. A procedure for the preparation of 3,6-bis(4-hydroxyphenyl)- 1,2,4,5-tetrazine is reported here. The syntheses of 2,4-bis[4-(4,5-dihydro-lH-imidazol-2-yl)phenoxy]pyrimidine and 2-chloro-4-[4-(4,5-dihydro-lH-imidazol-2-yl)- phenoxylpyrimidine exemplify the use of the title synthetic intermediates.     

Synthesis of aza-aromatic hydroxylamine-O-sulfonates and their application to tandem nucleophilic addition-electrophilic 5-endo-trig cyclization

Hydroxylamine-O-sulfonic acid (HOSA) was used as an efficient nucleophilic amination reagent for 2-chloropyrimidines, 2-chloroquinolines, and 1-chloroisoquinoline. The newly obtained heteroaromatic hydroxylamine-O-sulfonates subjected to the reaction with acyl isothiocyanates underwent tandem nucleophilic addition-electrophilic 5-endo-trig cyclization. The mechanism of the cyclization was investigated with use of the long-range corrected hybrid density functional ωB97X-D/6-31+G^∗ and SM8 (DMF) solvation model. The structures of the heteroaromatic hydroxylamine-O-sulfonates and N-(5-methoxy-2H-[1,2,4]thiadiazolo[2,3-a]pyrimidin-2-ylidene)benzamide were confirmed by single crystal X-ray analysis. N-(2H-[1,2,4]thiadiazolo[3,2-a]isoquinolin-2-ylidene)benzamide exhibited a pronounced in vitro cytostatic activity against human tumor cell lines SISO, LCLC, A-427, DAN-G, and RT-4 (IC₅₀ in the range 1.47-2.97 μM).     

Amides and esters of phenylpropenoic acids from the aerial parts of Trifolium pallidum

Two new derivatives of phenylpropenoic acids, N-trans-feruloyl-L-DOPA and O-trans-caffeoyl-malic acid dimethyl ester, along with four known N-trans-caffeoyl-L-DOPA (clovamide), N-trans-caffeoyl-L-DOPA-methyl ester, O-trans-caffeoyl-malic acid, O-trans-feruloyl-malic acid and quercetin 3-O-beta-D-glucopyranoside were isolated from the aerial parts of Trifolium pallidum. Their structures were elucidated by extensive spectroscopic methods including 1D- (1H, 13C) and 2D-NMR (DQF-COSY, HSQC, HMBC) experiments as well as mass spectrometry analysis.     

Nonadiabatic dynamics of uracil: population split among different decay mechanisms

Nonadiabatic dynamics simulations performed at the state-averaged CASSCF method are reported for uracil. Supporting calculations on stationary points and minima on the crossing seams have been performed at the MR-CISD and CASPT2 levels. The dominant mechanism is characterized by relaxation into the S(2) minimum of ππ* character followed by the relaxation to the S(1) minimum of nπ* character. This mechanism contributes to the slower relaxation with a decay constant larger than 1.5 ps, in good agreement with the long time constants experimentally observed. A minor fraction of trajectories decay to the ground state with a time constant of about 0.7 ps, which should be compared to the experimentally observed short constant. The major part of trajectories decaying with this time constant follows the ππ* channel and hops to the ground state via an ethylenic conical intersection. A contribution of the relaxation proceeding via a ring-opening conical intersection was also observed. The existence of these two latter channels together with a reduced long time constant is responsible for a significantly shorter lifetime of uracil compared to that of thymine.     

On convergence of solutions of a second order nonlinear difference equations

The object of the present paper is to establish some criteria of the convergence of all bounded solutions of (1), (1').