Wyniki wyszukiwania - BazTech

1

Static quenching of ruthenium(II)-polypyridyl complexes by gallic acid and quercetin in aqueous and micellar media

Sheeba D, Gnana Raj G. A.

International Letters of Chemistry, Physics and Astronomy

|

2014

|

Vol. 13, iss. 1

21-31

EN

The reactions of gallic acid and quercetin with the excited state Ru(II) complexes proceed through photoinduced electron transfer reaction in sodium dodecyl sulfate (SDS) and aqueous media at pH 11 and has been studied by luminescence quenching technique. The static nature of quenching is confirmed from the ground state absorption studies in both the media. The observed quenching rate constant (kq) values are sensitive to the nature of the ligand, medium and the structure of the quenchers. The electrostatic interaction of the cationic complexes with the anionic micelle reduces the kq values in SDS compared to that in aqueous medium.

2

Wpływ kompozycji układów fotoinicjujących na szybkość inicjowania polimeryzacji wolnorodnikowej monomerów wielofunkcyjnych w zakresie światła widzialnego

Kabatc J., Jurek K.

Przemysł Chemiczny

|

2013

|

T. 92, nr 11

1987-1993

PL

Opisano wpływ czynników kinetycznych i termodynamicznych procesu przeniesienia elektronu oraz struktury pary donor-akceptor (wpływ budowy barwnika oraz drugiego koinicjatora) na szybkość inicjowania polimeryzacji wolnorodnikowej triakrylanu 2-etylo-(2hydroksymetylo)-1,3-propanodiolu (TMPTA). Przedstawiono również mechanizmy procesów pierwotnych i wtórnych w trójskładnikowych układach fotoinicjujących. Chemiczna modyfikacja struktury sensybilizatora, składu chemicznego i optymalizacja stężeń składników układów fotoinicjujących prowadzą do otrzymania efektywnych i porównywalnych z fotoinicjatorami tworzącymi wzbudzony stan trypletowy barwnikowych, singletowych układów fotoinicjujących, mogących znaleźć zastosowanie w procesie polimeryzacji wolnorodnikowej monomerów wielofunkcyjnych w zakresie światła widzialnego.

EN

A review of 23 refs., mainly of authors’ own papers (18 refs.).

3

Aryl and N-arylamide carbon nanotubes for electrical coupling of laccase to electrodes in biofuel cells and biobatteries

Żelechowska K., Stolarczyk K., Łyp D., Rogalski J., Roberts K. P., Bilewicz R., Biernat J. F.

Biocybernetics and Biomedical Engineering

|

2013

|

Vol. 33, no. 4

235--245

EN

Single walled carbon nanotubes (SWCNTs) were equipped with aryl residues by chemical reactions. These insoluble materials were used to substitute classical soluble mediators, which help to transfer electrical charge between the conducting electrode and the redox active center of enzyme molecules. The effect of different aryl residues on the efficiency of the catalytic reduction of dioxygen in the presence of laccase was systematically studied using voltammetry and measuring the power output of a biofuel cell.

4

Wykorzystanie cienkich warstw polielektrolitowych zawierających polimery przewodzące do otrzymania ultracienkich ogniw słonecznych

Kruk T.

LAB Laboratoria, Aparatura, Badania

|

2012

|

R. 17, nr 3

6-13

5

Kinetics and mechanism of electron transfer to pyridinium chlorochromate (VI) from sulfur containing amino acid, L-cysteine in aqueous and micellar media

Senapati S., Das S., Mohanty P., Patnaik A.K.

Polish Journal of Chemical Technology

|

2011

|

Vol. 13, nr 2

6-10

EN

The electron transfer reaction of L-cysteine (RSH) with pyridinium chlorochromate (PCC) has been studied spectrophotometrically over the range 2.0 ≤ 10^3 [RSH] ≤ 6.0; 0.01 ≤ [H+] ≤ 0.2; 298 ≤ T ≤ 318 K and I = 0.3 mol dm-3 (NaClO4). The electron transfer reaction has also been carried out in the presence of anionic, cationic and neutral micelle. The reaction in acid medium is strongly catalyzed by changing [SDS]T (sodium dodecyl sulfate) up to 3 × 10-2 mol dm-3, beyond this concentration of SDS, the rate is retarded. The cationic and neutral micelle has a small effect on the rate. ΔH≠ (kJ mol-1) and ΔS≠ (JK-1 mol-1) values for the k1 and k2 paths are 30.20 ± 0.25, -159.65 ± 0.83 and 29.60 ± 0.62, -127.09 ± 2.17, respectively. The negative activation entropy is indicative of the ordered transition state for the electron transfer reaction. Formation of 2-amino-3-(2-amino-2-carboxy-ethyl) disulfanyl-propanoic acid as product is strongly supported by IR spectra.

6

Zastosowanie teorii funkcjonałów gęstości do modelowania właściwości elektronowych skorpionianowych kompleksów oksodimolibdenowych

Romańczyk P., Brocławik E.

Chemik

|

2011

|

Vol. 65, nr 10

1093-1100

PL

W artykule, na przykładzie skorpionianowych kompleksów oksodimolibdenowych o mieszanej walencyjności, przedstawiono zastosowanie modelowania DFT do określenia i interpretacji fizycznej wpływu wzajemnej orientacji grup [MoII,INO]3+,2+ (par donorowo- akceptorowych, D-A) na przepływ gęstości elektronowej we fragmencie Mo-O-Mo. Zależność struktury elektronowej, tj. lokalizacji/ delokalizacji niesparowanego elektronu od wzajemnego położenia lokalnych układów współrzędnych D i A, może nadawać kompleksom właściwości molekularnych przełączników i reostatów.

EN

This paper presents the application of DFT modelling in the determination and physical interpretation of the effect of mutual orientation of [MoII, INO] 3+,2+ groups (donor-acceptor pairs, D-A) on the electron density flow in the Mo-O-Mo moiety, exemplified by oxodimolybdenum scorpionate complexes of mixed valence. The relationship between the electron structure, i.e. localization/ delocalization of unpaired electron and mutual position of D and A coordinate systems, may bestow the properties of molecular switches and rheostats on complexes.

7

Polimeryzacja anionowa inicjowana reagentami przenoszącymi elektrony

Grobelny Z., Stolarzewicz A., Szczepański M., Piekarnik B.

Wiadomości Chemiczne

|

2008

|

[Z] 62, 9-10

849-873

EN

This work describes the polymerization processes with electron-transfer reagents. Alkali metals, salts of aromatic hydrocarbons radical anions, and solutions of alkalides, i.e. salts containing alkali metal anions and complexed alkali metal cations, belong to such species [33-39]. The alkali metals transfer one electron to vinyl and diene monomers in the heterogeneous systems [54-73]. The radical anions are also able to transfer one electron [74, 77-82], however, in some cases they behave as nucleophiles [82-85] or bases [86]. These initiators are applied for the polymerization of vinyl and oxacyclic monomers in homogeneous systems. Both of them are named single-electron-transfer (SET) reagents. The alkalides are two-electron-transfer (TET) reagents. Among them potassium potassides K-, K+(18-crown-6) and K-, K+(15-crown-5)2 in tetrahydrofuran solution are mostly used for the polymerization of various monomers [53]. The initiation with these salts is usually a multistage process. An organopotassium compound is formed as the intermediate product which after the protonation by crown ether becomes the real initiator of the polymerization of vinyl monomers [92, 93, 97, 100]. The organometallic intermediate can be also protonated by the monomer or can decompose with the elimination in the systems containing oxiranes [107, 110-113] or lactones [127]. Potassium alkoxides or potassium salts of carboxylic acids, respectively, are the genuine initiators in this case. Crown ethers, known as the stable activators of chemical reactions, can participate in these processes as the reagents [107, 110, 116]. In the ring-opening reaction they form unsaturated potassium alkoxides which serve as the additional initiating agents [53, 97].

8

The Excited State Relaxation Path of N,N-Diethyl-5-cyanopyridine and N,N-Diethylbenzaldehyde

Dobkowski J., Sazanovich I.

Polish Journal of Chemistry

|

2008

|

Vol. 82, nr 4

831-845

EN

The molecules which possess, as electron donors, dialkylamino groups linked by a single bond with the acceptor subunits undergo fast excited state intramolecular charge transfer (ICT), emitting dual fluorescence in polar solvents. The short and the long-wave length fluorescence bands are traditionally assigned as Fb and Fa, respectively. The nature of the excited state from which the Fa emission originates, as well as the mechanism of energy degradation have been the subject of many controversies. As the objects of this study, 2-(N,N-di ethyl)-5-cyanopyridine (PEC) and p-N,N-diethylaminoacetophenone (DEABA) were selected. For these molecules different sequence of the two low-lying pi pi* La and Lb states was postulated, which can help to verify the excited state mechanisms of the charge separation. The experimental results obtained by stationary and time-resolved spectroscopy show that the anomalous Fa emission originates from the ICT state generated by the mutual twist of the donor and acceptor group (TICT model).

9

Effect of excitation migration on the decay of excited states via electron transfer to acceptors

Gutman M., Hilczer M., Tachiya M.

Nukleonika

|

2005

|

Vol. 50,suppl.2

39-43

EN

Simulation of fluorescence quenching due to electron transfer from a photoexcited donor to an acceptor, in a rigid matrix has been performed. The model assumes competition between processes of the electron transfer and the resonant excitation energy transfer among donors. Electron and energy transfers are described in terms of the Marcus and the Förster theories, respectively. Dependence of the fluorescence quenching on the donor concentration and on the parameters of the Marcus and Förster equations has been investigated at a fixed acceptor concentration. Fluorescence decay curves calculated for various concentrations of donors have been compared with experimental decays.

10

Intramolecular electron transfer on the vibrational timescale in mixed valence ruthenium clusters

Imai N., Hamaguchi T., Yamaguchi T., Ito T.

Materials Science

|

2003

|

Vol. 21, No. 2

207-214

EN

The thermodynamic stability of the mixed valence (one electron reduced) state between linked Ru3 units was studied by means of electrochemistry for the series of the ligand bridged triruthenium cluster dimers, [Ru3(ž3-O)(ž-CH3CO2)6(CO)(L)(ž-BL)Ru3(ž3-O)-(ž-CH3CO2)6(CO)(L)] (BL = pyrazine: L = 4-dimethyl-aminopyridine (dmap) (1a), pyridine (py) (1b), 4-cyanopyridine (cpy) (1c), 1-azabicyclo[2.2.2]octane (1d); BL = 4,4'-bipyridine: L = dmap (2a), py (2b), cpy (2c); BL = 2,7-diazapyrene: L = dmap (3a); BL = 1,4-diazabicyclo-[2.2.2]octane: L = dmap (4a), py (4b), cpy (4c)). The mixed valence states undergoing rapid intramolecular electron transfers were observed by IR spectroelectrochemistry. By simulating dynamical effects on the observed ?(CO) absorption bandshapes, the rate constants, ke, for electron transfer in the mixed valence states of 1a, 1b, 1c and 1d were estimated to be 9 x 1011 s-1 (at room temperature (rt)), 5 x 1011 s-1 (at rt), ca. 1 x 1011 s-1 (at rt), and 1 x 1012 s-1 (at -18°C), respectively. Possible applications of this approach to asymmetric mixed valence systems were discussed.

11

pH effects on the photooxidation of methionine derivatives by the 4-carboxybenzophenone triplet state

Hug G., Bobrowski K., Kozubek H., Marciniak B.

Nukleonika

|

2000

|

Vol. 45, nr 1

63-71

EN

Reduction of the triplet state of 4-carboxybenzophenone (CB) by a series of five substituted methionines was monitored under laser flash photolysis conditions in aqueous solution. Spectral resolution techniques were employed to determine initial quantum yields of the photoproducts. Branching ratios were evaluated for the decay of the charge-transfer complex by the competing processes of back electron transfer, proton transfer, and escape of radical ions. The relative prominence of these processes was discussed in terms of the proton-transfer tendencies of the nominal sulfur-radical-cationic species. A scheme was proposed to account for the pH effects observed. The kinetic equations were solved with a minimum of assumptions, and simulations were performed that qualitatively support the proposed scheme.

12

Spectroscopic study of hydroxymethyl radicals produced on MoOx/SiO2 catalysts by interaction of methanol with UV-induced [Mo5+--O-] triplet state

Sojka Z., Che M.

Bulletin of the Polish Academy of Sciences. Chemistry

|

2000

|

Vol. 48, No. 4

313-324

EN

EPR along with MAS-NMR and QM spectroscopy have been used to investigate the structure and reactivity of hydroxymethyl radicals formed upon UV -irradiation of methanol adsorbed on MoOx /Si0(2) catalysts. The use of natural and 13C-enriched methanol allowed the authors to ascertain the 1 H superhyperfine and 13C hyperfine tensors. Based on the analysis of the magnetic parameters the structure of .CH2OH radical interacting with the catalysts has been determined: it is non-planar and the c- H bonds are stretched. The hydroxymethyl intermediates were found to reduce surface Mo(6+) centers and adsorbed O2 via an electroprotic mechanism involving electron transfer and release of the hydroxyl proton.

13

Fotoinicjatory polimeryzacji rodnikowej: fotodysocjujące i z przeniesieniem elektronu

Linden A. E., Pączkowski J., Rabek J. F., Wrzyczyński A.

Polimery

|

1999

|

T. 44, nr 3

161-176

PL

Na podstawie wyników prac własnych oraz licznych źródeł z literatury scharakteryzowano obecny stan wiedzy w dziedzinie fotoinicjowania polimeryzacji, uwzględniając przy tym zarówno czynniki warunkujące fotoinicjowanie (absorpcja promieniowania, energia wiązania, efekt rozpuszczalnika, fotosensybilizacja), jak i klasyfikację fotoinicjatorów w ramach dwóch podstawowych grup: inicjatorów alfa lub beta-dysocjujących (odpowiednio związków, w których następuje rozszczepienie wiązania w położeniu alfa lub beta w stosunku do grupy np. karbonylowej). Przedstawiono także ogólny opis kinetyczny fotoindukowanej polimeryzacji rodnikowej oraz szczegółowo omówiono mechanizmy i kinetykę fotoindukowanego międzycząsteczkowego przeniesienia elektronu w procesach fotoinicjowania polimeryzacji rodnikowej.

EN

Photoinitiation of polymerization is reviewed, including Author's own data, covering factors like absorption of radiation, bond energy, solvent effect, and photosensibilization. Photoinitiators are classified into two principal groups, a and B, which dissociate to yield compounds that split the bond in position a or B with respect, e.g., to the carbonyl group. A general kinetic description of photoinduced radical polymerization is given and the mechanisms and the kinetics of photoinduced intermolecular electron transfer in the process of photoinitiation of radical polymerization are discussed.

14

Preparation of cis-[Cr(N3)(bpy)2(H2O)]2(+) complex and studies on a composite mechanism of its aquation stimulated by Cr(2+)(aq)-ions

Katafias A., Kita P., Madej E.

Polish Journal of Chemistry

|

1998

|

Vol. 72, nr 3

595-606

EN

Anation of cis-[Cr(bpy)2(H2O)2](3+) ion (bpy=2,2'-bipyridine) in NH3/N3(-) media gives a novel very inert monoazidocomplex whose formula and structure can be proposed as cis-[Cr(N3)(bpy)2(H2O)](2+). This complex decomposes rapidly by addition of Cr(2+)(aq) into a dereated acidic solution. Analysis of the reaction products and the kinetics suggests an electron transfer Cr(II)-Cr(III) via competitive reaction pathways: inner-sphere through Cr(III)-N3-Cr(II) intermediate, outer-sphere and/or perhaps also via a more direct interaction of Cr(II) with pi-ring of the coordinated bipyridine.