Electron donors charge transfer interactions

Recently, the quaternized poly-4-vinylpyridine, 50-54 (QPVP) was found to be an electron acceptor in the charge-transfer interactions 104 Ishiwatari et al.105) studied alkaline hydrolyses of p-nitrophenyl-3-indoleacetate 58 (p-NPIA) and N-(indole-3-acryloyl) imidazole 59 (IAI) (electron donor) in the presence of QPVP. The fcobs vs. polyelectrolyte concentration plots are shown in Fig. 12. As is seen in... 

More recently, Kim et al. synthesized dendritic [n] pseudorotaxane based on the stable charge-transfer complex formation inside cucurbit[8]uril (CB[8j) (Fig. 17) [59]. Reaction of triply branched molecule 47 containing an electron deficient bipyridinium unit on each branch, and three equiv of CB[8] forms branched [4] pseudorotaxane 48 which has been characterized by NMR and ESI mass spectrometry. Addition of three equivalents of electron-rich dihydrox-ynaphthalene 49 produces branched [4]rotaxane 50, which is stabilized by charge-transfer interactions between the bipyridinium unit and dihydroxy-naphthalene inside CB[8]. No dethreading of CB[8] is observed in solution. Reaction of [4] pseudorotaxane 48 with three equiv of triply branched molecule 51 having an electron donor unit on one arm and CB[6] threaded on a diaminobutane unit on each of two remaining arms produced dendritic [ 10] pseudorotaxane 52 which may be considered to be a second generation dendritic pseudorotaxane. 

It has not yet been clarified whether the ring substituents interact directly with the binding site or affect the molecular characteristics of the DHP molecules in common. A recently used atomistic pseudoreceptor model for a series of DHP indicated a putative charge-transfer interaction was stabilizing the DHP-binding site complex [19]. To prove this hypothesis qualitative and quantitative analysis of the molecular orbitals of nine DHP derivatives (Fig. 9.11) was performed [18]. Charge-transfer (or electron-donor-acceptor) interactions are indicative of electronic... 

Fig. 9.12 Schematic representation of a charge-transfer interaction. The solid arrow illustrates n-electron transfer between the HOMO of the donor molecule (HOMOD) and the LUMO of the acceptor molecule (LUMOA). Dashed arrows indicate interactions between corresponding HOMO and LUMO of one molecule [18].

Mechanical movements in supramolecular structures rely on modulation of noncovalent-bonding interactions. Such changes occur when charge-transfer interactions between electron-donor and electron-acceptor groups are weakened. 

Specific donor-acceptor charge transfer interactions can lead to a relatively large numerical value of the electronic matrix element, possibly attributable to an increase in V, and, thus, to larger rate constants than those predicted by distance variations alone. 

Attack on the aromatic ring and formation a n-complex or electron donor-acceptor complex N02 + ArH —> ArH N02. This complex involves high electrostatic and charge-transfer interactions between the n-aromatics and nitroninm ion. 

The term charge tranter refers to a succession of interactions between two molecules, ranging from very weak donor-acceptor dipolar interactions to interactions that result in the formation of an ion pair, depending on the extent of electron delocalization. Charge transfer (CT) complexes are formed between electron-rich donor molecules and electron-deficient acceptors. Typically, donor molecules are p-electron-rich heterocycles (e.g., furan, pyrrole, thiophene), aromatics with electron-donating substiments, or compounds... 

Bulk crystalline radical ion salts and electron donor-electron acceptor charge transfer complexes have been shown to have room temperature d.c. conductivities up to 500 Scm-1 [457, 720, 721]. Tetrathiafiilvalene (TTF), tetraselenoful-valene (TST), and bis-ethyldithiotetrathiafulvalene (BEDT-TTF) have been the most commonly used electron donors, while tetracyano p-quinodimethane (TCNQ) and nickel 4,5-dimercapto-l,3-dithiol-2-thione Ni(dmit)2 have been the most commonly utilized electron acceptors (see Table 8). Metallic behavior in charge transfer complexes is believed to originate in the facile electron movements in the partially filled bands and in the interaction of the electrons with the vibrations of the atomic lattice (phonons). Lowering the temperature causes fewer lattice vibrations and increases the intermolecular orbital overlap and, hence, the conductivity. The good correlation obtained between the position of the maximum of the charge transfer absorption band (proportional to... 

In n symmetry, there is a stabilizing donor-acceptor interaction involving four electrons between the doubly degenerate nHOMO and itLUMo causing two partial n bonds (8). They are opposed by the Pauli repulsive iHomo - homo two-center four-electron (2c-4e) interaction. Note the difference in nature between c and the n bonds the former is an electron pair bond between singly occupied orbitals, whereas the latter evolves from a donor-acceptor or charge transfer interaction between occupied and unoccupied orbitals. 

For now, it has been shown, that the presence of attractive interactions as they are present between the two redox-active moieties, exTTF and leads to aggregation phenomena in the high concentrations regime (i.e. FT 4 M 1). In turn, the photophysical response of the resulting intracomplex hybrids differs substantially from that found in the low concentrations regime, where only the monomeric form is present. In particular, the ground-state charge-transfer interactions result from a shift of electron density from exTTF to C o due to the short distance between donor and acceptor. 

Next, a strong solvent dependence emerges. When varying the solvent polarity from, for example, toluene to benzonitrile, the Cemission quenching increases (Fig. 9.44). In summary, such observations imply charge-transfer interactions between the Ceo electron acceptor and exTTF electron donor. Obviously, the charge transfer pathway passes the transiently formed C,l0 singlet excited state. 

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