Lioudmila Fomina

The Glaser reaction mechanism. A DFT study

Abstract A detailed mechanism for the Hey modification of the Glaser oxidative coupling of terminal acetylenes has been formulated based on DFT calculations. The mechanism includes Cu(I)/Cu(III)/Cu(II)/Cu(I) catalytic cycle and explains the dioxygen molecule activation mechanism by Cu(I) species to give water molecule as final product of dioxygen reduction. The key step of the reaction mechanism is the oxidation of Cu acetylide by molecular oxygen to form dicopper-dioxo complex with [Cu2(μ-O2)]2+ core. Relatively low activation energies found for the reaction steps support the viability of the formulated mechanism.

Polymers from coumarines: 4. Design and synthesis of novel hyperbranched and comb-like coumarin-containing polymers

Abstract Novel monomers containing coumarin groups [2-(7-Cumarinyloxy)Oethoxy]dimethyl terephthalate and [6-(3-carboxy)coumarinyl] diacetylhydroquinone were synthesized and polymerized by high temperature polycondensation to give hyperbranched and comb-like coumarin-containing polymers. All polymers were completely soluble in chlorinated aliphatic hydrocarbons and showed M n in the range of 2000–50000 and gave film of good optical quality on casting from solution. All polymers except one were amorphous with T g in the range of 100–230°C and thermostability of 370–415°C. All polymers were found to be blue emitters emitting light in the range 450–492 nm.

Synthesis and polymerization of β,β-dibromo-4-ethynylstyrene ; preparation of a new polyconjugated, hyperbranched polymer

The new monomer β,β-dibromo-4-ethynylstyrene was synthesized and polymerized by the Heck reaction to give a partially soluble, conjugated hyperbranched polymer. The polymer structure was elucidated using standard spectroscopic techniques and with the aid of model compound synthesis. Theoretical calculations using the AM1 method were carried out and they showed that conjugation in the polymer is partially disrupted by twisting of the benzene rings. Both the model compound and the polymer showed luminescence.

Synthesis and characterization of well-defined fully conjugated hyperbranched oligomers of β, β-dibromo-4-ethynylstyrene

Abstract Well-defined dendritic oligomers of poly(β,β-dibromo-4-ethynylstyrene) of the first and second generation havebeen synthesized by a stepwise synthesis, and characterized. It was found from n.m.r. analysis and by theoretical calculations that free rotation around formal single bonds is hampered by conjugation. All oligomers were found to be blue emitters with their emission maxima correlating with the number of repeating units. All dendrimers except dendrimer 12 (β,β-bis[β′,β′-di(β″,β″-dibromostyryl-4″-ethynyl)styryl-4′-ethynyl]-4-ethynylstyrene) showed two maxima in the excitation spectra.

Charge transfer complexes of fullerene[60] with porphyrins as molecular rectifiers. A theoretical study

Molecular diodes based on charge transfer complexes of fullerene[60] with different metalloporphyrins have been modeled. Their current–voltage characteristics and the rectification ratios (RR) were calculated using direct ab initio method at PBE/def2-SVP level of theory with D3 dispersion correction, for voltages ranging from −2 to +2 V. The highest RR of 32.5 was determined for the complex of fullerene[60] with zinc tetraphenylporphyrin at 0.8 V. Other molecular diodes possessed lower RR, however, all complexes showed RR higher than 1 at all bias voltages. The asymmetric evolutions and alignment of the molecular orbitals with the applied bias were found to be essential for generating the molecular diode rectification behavior. Metal nature of metalloporphyrins and the interaction porphyrin–electrode significantly affect RR of molecular diode. Large metal ions like Cd2+ and Ag2+ in metalloporphyrins disfavor rectification creating conducting channels in two directions, while smaller ions Zn2+ and Cu2+ favor rectification increasing the interaction between gold electrode and porphyrin macrocycle.

Charge transfer complexes between 4,4′-disubstituted diphenyldiacetylenes: experimental and theoretical study

Abstract Novel charge transfer (CT) complexes containing donor and acceptor derivatives of diphenyldiacetylene have been synthesised and characterised. The structure of CT complexes was modelled at the B3LYP/6-31G(d)//B3LYP/6-31G(d) level of theory. It was found that the complex formation is mainly due to dipole–dipole interaction between side groups of diacetylene molecules and there was no significant charge transfer between donor and acceptor in the ground state. On the other hand, optical excitation of CT complexes leads to strong charge transfer from donor to acceptor molecule as followed from the modelling using time-dependent density functional theory (DFT) method. Diacetylene molecules adopt strongly bent configuration in CT complexes which is prohibitive for solid-state topochemical polymerisation of diacetylenes

Studies on diacetylenic vinyl compounds

SummaryThree alka-3,5-diynylmethacrylate and 1,8-Bis(methacryloxy)octa-3-5-dyine were synthesized and their polymerization in the molten state was studied. 3,5-Octadiynylene-1,8-dimethacrylate, which was the only one that was solid at room temperature, was not light sensitive in the solid state. All the monomers underwent rapid polymerization at 140 °C. The DSC and IR-spectra indicated that the polymerization of the vinyl and diacetylenic groups takes place simultaneously. An optically highly transparent, yellow-orange glass was obtained.

Reactions of ketones with aromatics in acid media. The effect of trifluoromethyl groups and the acidity media. A theoretical study

AbstractThe reactions of acetone, 2,2,2-trifluoroacetone and hexafluoroacetone in methanesulfonic (MSA) and triflic acids (TFSA) with benzene have been studied at M06-2X/6-311+G(d,p) level using cluster-continuum model, where the carbonyl group is explicitly solvated by acid molecules. The introduction of a trifluoromethyl group into the ketone structure reduces the activation energy of the tetrahedral intermediates formation due to an increase of the electrophilicity of the carbonyl group and raises the activation and the reaction energies of the C-O bond cleavage in formed carbinol due to the destabilization of the corresponding carbocation. The introduction of the second trifluoromethyl group inhibits the hydroxyalkylation reaction due to a very strong increase of the reaction and activation energies of the C-O bond cleavage which becomes the rate determining step. The most important catalytic effect of TFSA compared to MSA is not the protonation of the ketone carbonyl, but the reduction of the activation and reaction energies of the carbinol C-O bond cleavage due to better protosolvation properties. Even for TFSA no complete proton transfer to carbonyl oxygen has been observed for free ketones. Therefore, the protonation energies of free ketones cannot be considered as a measure of ketone reactivity in the hydroxyalkylation reaction. FigureReactions of ketones with aromatics in acid media 

Halogenated Olefins as Chain Transfer Agents in the Synthesis of Telechelic Polynorbornenes Using Ruthenium Alkylidene Catalysts. Computational and Experimental Studies

Ring-opening metathesis polymerization (ROMP) of norbornene (NB) and its derivatives N-adamantyl-exo- endo-norbornene-5,6-dicarboximide (AdNDI) and N-cyclohexyl-exo-endo-norbornene-5,6-dicarboximide (CyNDI) in the presence of cis-1,4-dichloro-2-butene (2a) and cis-1,2-dichloro-ethylene (2b) as chain transfer agents (CTAs) using a (1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazolilydene) (PCy3)Cl2Ru=CHPh (I) has been studied. � Halogenated ole- fin 2b shows no activity as a CTA whenhalogenated olefin 2a is readily cross-metathesized with NB and norbornene dicarboximides. The chain transfer reaction pathways during the ROMP of NB to 2b using a (1,3-diphenyl-4,5- dihydroimidazol-2-ylidene) (PCy3)Cl2Ru=CHPh (1) have been studied at B3LYP/LACVP* level of theory. The calcula- tions show that 2b is a poor substrate for the metathesis reaction due to the steric effect produced by chlorine atoms di- rectly linked to the double bond. The calculated Gibbs free activation energy of a chain transfer reaction from ring-opened NB to 2b was 25.1 kcal/mol.

Novel substituted 1‐amino‐4,5,8‐naphthalenetricarboxylic acid‐1,8‐lactam‐4,5‐imides: experimental and theoretical study

The electronic structure of the ground and the first singlet excited state of a novel class of fluorescent dyes, substituted 1-amino-4,5,8-naphthalenetricarboxylic acid-1,8-lactam-4,5-imides, was studied using both time-dependent density functional theory and semi-empirical approaches. It was found that the S0–S1 transition in lactamimides involves presumably HOMO–LUMO electron promotion. Strong intramolecular charge transfer from lactam nitrogen, C-2 and C-4 atoms to C-6 and C-7 atoms of the naphthalene ring occurs on S0–S1 transition. As a result, donor and acceptor side groups dramatically affect the long-wave absorption maximum, allowing control of its position over a range of more than 100 nm. Positions 2 and 7 are most sensitive to the electronic effects of the side groups owing to the combination of electronic and steric factors. Three novel derivatives of lactamimides bearing donor and acceptor side groups were synthesized and characterized. Their UV–visible spectra confirmed the results of calculation. Copyright