Donor-acceptor molecular complexes

The first example of a donor-acceptor molecular complex was noted in 1949 by Bensei and Hildebrand [137] in their studies involving charge transfer complexes between benzene and molecular iodine. Subsequently such complexes were studied by Mulliken [138] and now more recently have been used by Stoddart et al. [16,139] in designing novel self-assembling systems. 

Donor-Acceptor Molecular Complexes in Alternating Copolymerization and in the Polymerization of Metal Halide-Complexed Vinyl Monomers... 

Mayoh, B, and Prout, C. K. Molecular complexes. Part 13.-Influence of charge transfer interactions on the structure of tt-tt electron donor-acceptor molecular complexes. J. Chem. Soc., Faraday Trans. 1072-1082 (1972). 

The electron donor-acceptor molecular complexes between iodine and thiazole, benzothiazole, and some derivatives have been studied in several organic solvents by UV spectroscopy <87CJC468>. In all cases, the presence of the thiazole ring produces a displacement of the Amax iodine band at 512 nm towards shorter wavelengths and a decrease of its absorbance. Moreover, a sharp isosbestic point near 470 nm was observed for all iodine-thiazole complexes. 2-Aryl and 2-hetarylbenzothiazoles showed fluorescence, the maxima of emission being between 350 nm and 395 nm. Both substituent and solvent effects on the spectra were observed <93MI 306-02>. The photophysical properties of bis(benzothiazolylidene)squaraine dyes have also been studied <93JPC13625>. 

Ni(salen)SnCl4 R ] (R = Ph, Me n = 1, 2) (324)Similar complexes were also reported with PbCl2Ph2 and TlCl2Ph, SbXs (X = C1, Br) and Mn(CO)3X. Di- and tri-nuclear complexes of nickel(II) were obtained by reacting Ni(N03)2 hydrate with Schiff b e complexes of nickel(Il). The donor-acceptor molecular complexes between 1,3,5-trinitrobenzene and bidentate Schiff base complexes were also investigated. ... 

By employing IGC, it is possible to test donor-acceptor molecular complexes and the stability of hydrogen bonds. 

The stabilization energies of the donor-acceptor molecular complexes of thiazoles and phenylthiazoles with tetracyanoethylene have been estimated... 

Herbstein FH (2005) Crystalline molecular complexes and compounds structures and principles, vol 2. Donor-acceptor molecular compounds (essentially localized interactions), Chap 11. Oxford University Press, London... 

The nitrosonium cation bears a formal relationship to the well-studied halogens (i.e. X2 = I2, Br2, and Cl2), with both classes of structurally simple diatomic electron acceptors forming an extensive series of intermolecular electron donor-acceptor (EDA) complexes that show well-defined charge-transfer absorption bands in the UV-visible spectral region. Mulliken (1952a,b 1964 Mulliken and Person, 1969) originally identified the three possible nonbonded structures of the halogen complexes as in Chart 7, and the subsequent X-ray studies established the axial form II to be extant in the crystals of the benzene complexes with Cl2 and Br2 (Hassel and Stromme, 1958, 1959). In these 1 1 molecular complexes, the closest approach of the... 

Aromatic substrates are by far the most commonly used substrates in the rapidly expanding area of photoinduced electron transfer [1,2]. This is obviously due to the favourable location of the frontier molecular orbitals in such compounds. The same factor facilitates the formation of electron transfer donor-acceptor (EDA) complexes both in the ground state (these possibly are intermediates in some thermal reactions, e.g. selected electrophilic substitutions), and in the excited state (exciplexes). 

Synonyms for EPDjEPA complex are electron donor acceptor (EDA) complex [50], molecular complex [57, 58], and charge-transfer (CT) complex [51]. Since normally the term molecular complex is only used for weak complexes between neutral molecules, and the appearance of a charge-transfer absorption band does not necessarily prove the existence of a stable complex, the more general expression EPDjEPA complex, proposed by Gutmann [53], will be used here. This will comprise all complexes whose formation is due to an interaction between electron-pair donors (Lewis bases) and electron-pair acceptors (Lewis acids), irrespective of the stabilities of the complexes or the charges of the components. 

Relevant studies concern proton donor/proton acceptor molecular complexes with different stoichiometries of 2 1, 1 1 and 1 2, as depicted in Scheme 14. The 1 2 complexes of pentafluoroaniline, 4-nitrotetrafluoroaniline and 4-aminotetrafluoropyridine in 1 2 complexes with THF and HMPA were investigated. The 1 1 complexes display a different stability129,137 from that of 1 2 complexes. As expected, the AH values for the 1 1 complexes were higher137,138 than for the 1 2 complexes, when calculated for a single ArNH2-PA bond134. 

The synthesis andncharacterization of PANi-SWNT composites has also been investigated previously [12-15]. Direct dissolution of pristine nanotubes (without chemical fictionalization) in aniline can occur via formation of a donor/acceptor charge complex [16] Using this approach SWNT/PANi composite films have been produced by chemical [17] or electrochemical [18] polymerization of aniline containing dispersed SWNTs. Alternatively, the SWNTs have been blended with preformed PAne in solvents such as N-methylpyrrohdone (NMP) [13]. The enhanced electroactivity and conductivity of SWNT/PANi composite films has been attributed to the strong molecular level interactions that occur between SWNTs and PANi. 

The intermolecular resonance can also be accounted for by simple molecular orbital theory [17, 18, 19] the linear combination of donor-acceptor molecular orbitals (LCDA-MO) theory. It is supposed that the wave function of the complex is the linear combination of the molecular orbitals implied, in first approximation, in the charge-transfer the highest occupied molecular orbital of the donor and the lowest vacant orbital of the acceptor ( a)-... 

The charge-tranter concept of Mulliken was introduced to account for a type of molecular complex formation in which a new electronic absorption band, attributable to neither of the isolated interactants, is observed. The iodine (solute)— benzene (solvent) system studied by Benesi and Hildebrand shows such behavior. Let D represent an interactant capable of functioning as an electron donor and A an interactant that can serve as an electron acceptor. The ground state of the 1 1 complex of D and A is described by the wave function i [Pg.394]

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. ... 

Since the energy of the transfer band is determined by the difference between the donor ionization potential and the acceptor electron affinity, this fact points to the increase of the PCS ionization potential with decreasing conjugation efficiency. Therefore, the location of the transfer band of the molecular complexes of an acceptor and various PCSs can serve as a criterion for the conjugation efficiency in the latter. In Refs.267 - 272) the data for a number of molecular complexes are given, and the comparison with the electrical properties of the complexes is made. 

Since the beginning of the 1980s, two different approaches to quantify the H-bond contribution to properties at the 2D and 3D levels developed independently. The carefully parameterized methodology of HYBOT allows one to take into account the influence of substituents on H-bond acceptor and donor strengths. Modern procedures based on X-ray data of ligand-macro molecular complexes consider the... 

Prout CK, Kamenar B (1973) Crystal structures of electron-donor-acceptor complexes. In Foster R (ed) Molecular complexes. Elek, London, pp 151-207... 

---