Charge transfer complex CTC

Interaction of PCSs with electron acceptors and donors results in molecular complexes with partial or complete charge transfer. In particular, detailed investigations involved charge transfer complexes (CTC) of poly (schiff base), polyazines, products of thermal transformations of PAN and a number of other PCSs129, 238, 241 243, 267. ... 

First of all, the reaction pathways shown in Scheme 1 involve the formation of charge transfer complexes (CTC) between olefin and Br2- The formation of molecular complexes during olefin bromination had been hypothesized often (ref. 2), but until 1985, when we published a work on this subject (ref. 3), complexes of this type had been observed only in a very limited number of circumstances, all of which have in common a highly reduced reactivity of the olefm-halogen system, i.e. strongly deactivated olefins (ref. 4), or completely apolar solvents (ref. 5) or very low temperatures (ref 6). 

EPR techniques were used to show (Polyakov et al. 2001a) that one-electron transfer reactions occur between carotenoids and the quinones, 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ), and tetrachlorobenzoquinone (CA). A charge-transfer complex (CTC) is formed with a -values of 2.0066 and exists in equilibrium with an ion-radical pair (Car Q ). Increasing the temperature from 77 K gave rise to a new five-line signal with g=2.0052 and hyperfine couplings of 0.6 G due to the DDQ radical anions. At room temperature a stable radical with y=2.0049 was detected, its... 

Significant recent modifications of the mechanism in Scheme 1 concern the demonstration that bromine-olefin charge transfer complexes (CTCs) are active intermediates on the reaction pathway and the possibility that ionic intermediates are formed reversibly. 

The charge transfer complex (CTC) of dioxygen with the monomer is very probable as a precursor of this reaction [48],... 

Amines possess a pair of p-electrons on the nitrogen atom. The nitrogen atom has a low electron affinity in comparison with oxygen. Therefore, amine can be the electron donor reactant in a charge-transfer complex (CTC) in association with oxygen-containing molecules and radicals. It will be shown that the formation of CTC complexes of amines with peroxyl radicals is important in the low-temperature oxidation of amines. 

Photoexcitation of a charge transfer complex (CTC) formed between the nucleophile and the substrate, followed by ET. 

Electron donor-acceptor monomer pairs form charge-transfer complexes (CTC), which collapse to the tetramethylene intermediates through the bond-formation between the p-carbons ... 

The situation may however be more complicated if charge transfer complexes (CTC) between the substrate and the anion are formed. This was suggested [104] in the case of the SRN1 reaction between ethyl-, phenyl- and diethyl phosphite anion in DMF where the UV spectrum of the mixture shows an enhanced absorption attributed to a CTC, the last one being the possible mediator for the photochemical activation of the reaction. 

The analysis of the registrated spectra and the comparison them with the literature data concerning the spectral characteristic of naphthalene in different media proved that there are several species of adsorbed naphthalene. Besides absorption and emission of weakly bonded "molecular species" of naphthalene, there are well-resolved additional new bands which should be considered as the evidence of the "chemisorbed species" presence. Careful analysis of these new bands - intensive, broad and red-shifted from the "molecular naphthalene" - lead us to the conclusion that the charge-transfer complexation (CTC) is responsible for these bands. 

This definition is analogous to that used for a electronic substituent constants and accounts for the formation ability of a charge-transfer complex (CTC), such as the n -complex formation ability of aromatic systems. 

In the presence of styrene as a comonomer, the grafting reaction seems to be predominant and therefore, the chain degradation by B -scission is reduced. This was confirmed by GPC analysis. Cross-propagation of styrene and maleic anhydride, both in solvent or in bulk, is well known. This behaviour is attributed to a charge-transfer complex (CTC) between maleic anhydride and styrene and can lead, in solution, to spontaneous copolymerisation (34,35). 

This fluorescence arises as a result of excitation in either of two spectral bands. Emission from a single chromophore is observed and the two excitation bands are described in terms of both an intra- and an inter-molecular charge transfer complex (CTC). The intra-CTC is ascribed to rotation around the imide nitrogen-phenyl bond. The inter-CTC arises as a result of the increase in aggregation associated with a more ordered phase. The emission intensity from excitation of the inter-CTC band increases linearly with reciprocal intermolecuar spacing. 

In contrast to other poly (olefin sulfone) s, little isomerization of the olefin occurs during cationic depropagation. The degradation of PMPS is extremely rapid and it is possible that the lifetime of the cationic intermediates may be too short for appreciable isomerization to occur. However, isomerization of the 2-methyl-l-pentene product to 2-methyl-2-pentene did occur during the postexposure period. The isomerization proceeded both in solution and in the solid state. It seems unlikely that the reactive intermediates (e.g. cations and free radicals) produced by irradiation catalyse the isomerization reaction since they would be expected to be destroyed during dissolution. However sulfur dioxide is well known to form charge transfer complexes (CTC) with olefins (1) and we propose that the isomerization occurs via such an intermediate ... 

Rate constants in Eq. (2) are 10-5 dm3 mol-1 s-1 for monoamines 9 and 10 and 10-2 dm3 mol-1 s l for PD 11 [50]. At a proper substitution, the amount of amines oxidized according to Eq. (2) is negligible in comparison with the process in Eq. (1). A considerable charge separation was observed in the transition state of Eq. (1) [51], Charge-transfer-complexes (CTC) have been envisaged for aromatic monoamines (40) and diamines (41) as the primary step preceding formation of the aminyl ... 

MAH is one of the monomers most often used for polyolefins functionalization. It is characterized by an extremely low capacity to homopolymerization, and this fact is explained by the steric features of its structure. The reactivity of MAH to macroradicals, however, is comparatively low. From the chemistry viewpoint, a steric hindrance and a lack of electron density in the double bond explain the low reactivity of MAH, which in MAH is symmetrical owing to the presence of two carbonyl groups. Attempts have repeatedly been made to work out procedures for increasing the chemical activity of MAH. Three methods have been proposed to activate the double bonds in MAH (i) to perform a grafting reaction for MAH in presence of an electron-donating monomer, for example, styrene, which is capable of forming a charge transfer complex (CTC) with MAH (ii) substitution... 

Comparison of the PES spectral dependence with the absorption spectrum of the ms evidences that PES in the visible region is due to the formation of weak electronic Donor Acceptor (DA) Charge Transfer Complexes (CTC) with absorption maxima in the region of 400600 nm [44]. The maxima and band absorption edge of the CTC... 

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