Search results for "Donor"
showing 10 items of 436 documents
Phenothiazine-based dyes with bilateral extension of π-conjugation for efficient dye-sensitized solar cells
2013
Four novel organic photo-sensitizers based on phenothiazine were designed, synthesized and characterized for efficient dye-sensitized solar cells. Anisole, octyloxybenzene and dodecyloxybenzene were incorporated into the phenothiazine by an Ullmann reaction. An additional octyloxybenzene was incorporated into one dye unit through a Suzuki coupling reaction. The modified phenothiazine moiety acts as an electron donor and cyanoacrylic acid acts as an electron acceptor and anchoring unit. The photophysical, electrochemical and sensitizing characteristics of the new dyes were evaluated. The bis(octyloxybenzene) substituted dye delivered the best performance with its sensitized solar cell displa…
Photoinduced electron transfer in molecular organizates at the gas-water interface
1994
Abstract The influence of the molecular geometry is of fundamental importance for a better understanding of the photoinduced electron transfer mechanism. Because of their typical molecular structures, cyclophane rings have proved to be suitable for this purpose as electron acceptor molecules adsorbed under an amphiphile monolayer. We used a pyrene-labelled phospholipid derivative both as molecular anchor for the cyclophane ring and electron donor molecule. The co-spreading technique was used to prepare the complex monolayers. Surface pressure and surface potential measurements have indicated similar monolayer behaviour as with dimyristoylphosphatidic acid as anchor molecule, leading to the …
The Aerobic and Anaerobic Respiratory Chain of Escherichia coli and Salmonella enterica: Enzymes and Energetics.
2014
Escherichia coli contains a versatile respiratory chain that oxidizes 10 different electron donor substrates and transfers the electrons to terminal reductases or oxidases for the reduction of six different electron acceptors. Salmonella is able to use two more electron acceptors. The variation is further increased by the presence of isoenzymes for some substrates. A large number of respiratory pathways can be established by combining different electron donors and acceptors. The respiratory dehydrogenases use quinones as the electron acceptors that are oxidized by the terminal reductase and oxidases. The enzymes vary largely with respect to their composition, architecture, membrane topolog…
A Comparison of Shuttling Mechanisms in Two Constitutionally Isomeric Bistable Rotaxane-Based Sunlight-Powered Nanomotors
2006
To find out how best to optimize shuttling of the macrocycle in a particular class of photochemically driven molecular abacus, which has the molecular structure of BR-I6+ in its Mark I prototype (Ashton et al., Chem. Eur. J. 2000, 6, 3558), we have synthesized and characterized a Mark II version of this kind of two-station rotaxane comprised of six molecular modules, namely (a) a bisparaphenylene[34]crown-10 electron donor macrocycle M and its dumbbell-shaped component which contains (b) a Ru(ii)-polypyridine photoactive unit P2+ as one of its stoppers, (c) a p-terphenyl-type ring system as a rigid spacer S, (d) 4,4′-bipyridinium (A12+) and (e) 3,3′-dimethyl-4,4′-bipyridinium (A22+) electr…
Molecular “Floppyness” and the Lewis Acidity of Silanes: A Density Functional Theory Study
2001
A comprehensive set of Lewis acid-base adducts of silanes was investigated by means of the density functional theory geometry optimization [B3LYP/6−31G(d)], and thermochemical calculations, [B3LYP/6−311+G(2d,p)//B3LYP/6−31G(d)]. Complex formation was found to weaken Si−Cl and Si−Br bonds more than Si−F or Si−H bonds. Comparable distances between Si and a Lewis base L (L = NH3, OH2, F−) are shorter in hexa- than in pentacoordinated complexes. The molecular structures of the pentacoordinated Si complexes allowed for a mapping of an SN2 reaction pathway by correlating the lengths of the Si−X and Si−L bonds. Complex formation was found to be exothermic for most of the coordination compounds, an…
ChemInform Abstract: Conjugated Compounds Based on Vinylthiazole Units.
2008
Conjugated oligomers attract increasing attention because of their interesting properties in materials science [1]. Moreover, they are model compounds for conjugated polymers. Molecules polarized by electronic effects, in particular push-pull systems having terminal donor-acceptor substitution represent a special class of such oligomers [2]. Their major applications are in the field of nonlinear optics (NLO), twophoton absorption (TPA), two-photon induced fluorescence (TPIF), and photorefractive materials (PR). Fig. 1 illustrates known 2,5-thienylenevinylenes with zwitterionic resonance structures 1 (D = NR2; A = NO2, CHO, SO2R; n = 1, 2) [3, 4]. The corresponding compounds 2 with thiazole …
Star-Shaped Push-Pull Compounds Having 1,3,5-Triazine Cores
2006
The 1,3,5-triazines 9–11 having OPV chains in the 2-, 4- and 6-position represent star-shaped compounds which exhibit strong push-pull effects. Their long-wavelength absorption S0 S1 is characterized by an intramolecular charge transfer (ICT) from the dialkylamino group as electron donor D via the conjugated chain to the 1,3,5-triazine core as electron acceptor A. Protonation of the dialkylamino group removes the donor capability, whereas protonation of the 1,3,5-triazine ring enhances the acceptor strength. Thus, the prevailing protonation site has a crucial influence on the push-pull effect and the ICT. The transition energies ΔE (S0 S1) pass through a minimum for the second generation 10…
Conjugated Oligomers with Terminal Donor–Acceptor Substitution
2005
Conjugated oligomers represent a prominent class of compounds from a viewpoint of their theory, synthesis, and applications in materials science. Push-pull substitution with an electron donor D at one end of the conjugation and an electron acceptor A at the other end results in them having outstanding optical and electronical properties. This Review highlights fundamental synthetic strategies for the preparation of such oligomers with n repeat units (n=1, 2, 3, 4, ..) and the rules that govern their linear and nonlinear optical properties (absorption, frequency doubling and tripling). The unification of chemical, physical, and theoretical aspects with an interdisciplinary image of this clas…
NLO Polymers Containing as Active Chromophore in Dandionylpyridinium, Betaine Units: Synthesis, Modeling and Characterization
2000
In present article we report about synthesis, quantum chemical model calculations, non-linear optical characterization and dependencies of the surface potential changes on irradiation with light of novel polyurethane based polymers, namely a bipolar organic compound N-(indan-1,3-dion-2-y1)-4-N’,N’dialkylaminopyridinium betaine (IPB) containing charged electron donor and electron acceptor groups covalently bonded to polyurethane polymer backbone. These newly synthesized IPB containing polymers could be regarded as a promising thermally stable organic non-linear optical materials with long time performance for photonic applications.
Conjugated Compounds Based on Vinylthiazole Units
2007
Conjugated oligomers attract increasing attention because of their interesting properties in materials science [1]. Moreover, they are model compounds for conjugated polymers. Molecules polarized by electronic effects, in particular push-pull systems having terminal donor-acceptor substitution represent a special class of such oligomers [2]. Their major applications are in the field of nonlinear optics (NLO), twophoton absorption (TPA), two-photon induced fluorescence (TPIF), and photorefractive materials (PR). Fig. 1 illustrates known 2,5-thienylenevinylenes with zwitterionic resonance structures 1 (D = NR2; A = NO2, CHO, SO2R; n = 1, 2) [3, 4]. The corresponding compounds 2 with thiazole …