Chaige-transfer complex

Examples of stable complexes are reactions of sulfur dioxide with styrene, or vinyl ethers with maleic anhydride,also a-olefins with maleic anhydride.Also, a reaction of /ran -stilbene with maleic anhydride. In these reactions chaige-transfer complexes form. They are stable and their existence can be detected by spectroscopic means. Additional energy, such as heat or a free-radical attack, converts them to diradicals and polymerizes them into alternating copolymers.i 1 1 ... 

HIZ 94] Hizal G., Yagci Y., Schnabel W., Chaige-transfer complexes of pyridinium ions and methyl- and methoxy-substituted benzenes as photoinitiators for the cationic polymerization of cyclohexene oxide and related compounds , Polymer, vol. 35, pp. 2428-2431,1994. 

Benesi HA, Hildebrand JH (1949) A spectrophotometric investigation of the interaction of iodine with momatic hydrocarbons. J Am Chem Soc 71 2703-2707 Foster R, Fyfe CA (1965) Interaction of electron acceptors with bases Pent 15. Determination of association constants of organic chaige-transfer complexes by NMR... 

The molecular systems in which the individual parts are held together by forces other than covalent bonds. These include ionic complexes (where the dominant attractive force is of electrostatic origin), complexes with hydrogen bonds, chaige transfer complexes, and true van der Waals molecules for which the dominant attractive contribution is the dispersion energy. 

An example of the cationic polymerization initiated by a chaige transfer complex is the reaction of Yamada, which can be illustrated by the polymerization of isobutylene with vanadium oxychloride complex with naphthalene in the heptane environment. The resulting complex decays with the formation of radical ions, which then react with isobutylene according to the following reactions ... 

The macrocydic polyether BPP34C10 and 1,1 -dimethyl-4,4-bipyridiniumbis(hexafluorophosphate) give rise to colorless solutions when they are dissolved by them-sdves in MeCN. The sudden appearance of a color, upon mixing the two compounds in MeCN, is indicative of complex formation and is a result of chaige transfer interadions between the complementaiy aromatic units of the host and guest. 

Some metal-tofigand chaige transfer bands in molecules with unsaturated ligands Acentric complexes with ligands such as acac or those having P. As, etc. as donor atoms... 

An absorption tIOSO min) found in the near-uifrared spectrum of this complex arises from a mixed valence transition. Li -induced metal-to-nietal chaige transfer was predicted by Hush for systems of this type before it was obaerved experimentally. Further, his theory relates the energy of absoqjtion to that required for thenral electron transfer ftv = 4 x E ) and from this it is possible to calculate the therma] electron transfer rale constant (5 x (0 s ).i ... 

The spin selection rule breaks down somewhat in complexes that exKbit spin-orbit coupling. This behavior is particularly common for complexes of the heavier transition elements with the result that bands associated with formally spin forbidden transitions (generally limited toLS = si) gain enough intensity to be observed. Table 11.16 summarizes band intensities for various types of electronic transitions, including fully allowed chaige transfer absorptions, which will be discussed later in the chapter. 

The magnetic moment arising from the ground A term is expected to be close to the spin-only value of 3.87 BM and independent of temperature. In practice, providing the compounds are mononuclear, these expectations are realized remarkably well apart from the fact that, as was noted for octahedral complexes of vanadium(lll), the third high-energy band in the spectrum is usually wholly or panially obscured by more intense chaige-transfer absorption. 

FIGURE 2.31 Complex plane analysis of cell impedance for a chaige-transfer process with both kinetic and diffusion control at a planar electrode. 

Table 3 Chaiges on HzXPsiPtCX PH2X, changes in the charges on the P atoms (5e, au), and charge-transfer energies (kJ/mol) for conformation A complexes ...

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