Phenol-water complexes

Figure 16. Spectrum of the phenol-water complex (a) total ion signal [23] (b) total ion signal [22] (c) ZEKE spectrum [22],...

Figure 18. Phenol-water complex intermolecular normal modes.

We also mention that the ionized phenol-water complex has been observed and examined in depth" . Complexes of phenol radical cation with ammonia" and molecular nitrogen have also been produced. The existence of an intramolecular hydrogen bond in orf/zo-substituted phenol radical cations has also been demonstrated . 

The infrared (IR) and Raman UV double-resonance spectroscopy of Ph0H(H20) 4 in the OH-stretching vibration region was also smdied . These smdies led to the conclusion that, on the one hand, the symmetric water vj and phenolic OH-stretching (voe) vibrations are downshifted considerably upon the formation of phenol-water complexes (compared with those inherent for bare water and phenol molecules). On the other hand, the antisymmetric V3 vibration of the water molecule is only weakly affected. This results in the appearance of a transparent window region ° in the IR spectrum... 

FIGURE 50. Six lower-energy structures of the phenol-waters complex. Bond lengths are in A. The geometrical parameters are paired for some particular stmctures the former value corresponds to the HF/A level while the MP2/A value is presented in parentheses. The HF/A [MP2(sp)/A] relative energy with respect to the global-minimum stmcture PhOH-iUs-l is given in kJ mol. Adapted from Reference 731 with permission... 

TABLE 38. The OH-stretch frequencies (in cm ) of phenol-waters complexes calculated at the HF/A and MP2/A (in parentheses) computational levels. Infrared intensity is in kmmol Raman (R) activity in A amu. Partial contributions are evaluated as the ratio of total displacements. The contribution of the first reported mode is referred to 100%... 

By analogy with the earlier studies (Reference 729), the PES search of the phenol-(water) complexes was initially performed by using a spht-valence double-zeta 6-31G(d) basis set via a GAUSSIAN 98 suit of packages. 

Phenol trimethylsilyl ether, fluorination of 647 Phenol-water complexes 145-169 Ph0H(H20)i 149-156 Ph0H(H20)2 149, 150, 152-155 Ph0H(H20)3 156-160 Ph0H(H20)4 160-169 Phenones—see Acenaphthoquinones, Acetophenones, Acrylophenones,... 

Y. Dimitrova, Theoretical study of structures and stabilities of hydrogen-bonded phenol-water complexes, J. Mol. Struct. (Theochem) 455, 9-21 (1998). 

The starting material is an 18 electron nickel zero complex which is protonated forming a divalent nickel hydride. This can react further with alkenes to give alkyl groups, but it also reacts as an acid with hard bases to regenerate the nickel zero complex. Similar oxidative addition reactions have been recorded for phenols, water, amines, carboxylic acids, mineral acids (HCN), etc. 

To understand the fundamental photochemical processes in biologically relevant molecular systems, prototype molecules like phenol or indole - the chromophores of the amino acids tyrosine respective trypthophan - embedded in clusters of ammonia or water molecules are an important object of research. Numerous studies have been performed concerning the dynamics of photoinduced processes in phenol-ammonia or phenol-water clusters (see e. g. [1,2]). As a main result a hydrogen transfer reaction has been clearly indicated in phenol(NH3)n clusters [2], whereas for phenol(H20)n complexes no signature for such a reaction has been found. According to a general theoretical model [3] a similar behavior is expected for the indole molecule surrounded by ammonia or water clusters. As the primary step an internal conversion from the initially excited nn state to a dark 7ta state is predicted which may be followed by the H-transfer process on the 7ia potential energy surface. 

In contrast to indole-ammonia clusters, for which the different steps of the photoinduced H-transfer reaction have been analyzed in detail, we have found no hints for such a reaction in indole(H20) clusters. Probably, like for phenol(H20) complexes the endoenergetic character of the reaction H+H2O—>H30 is responsible for the missing H-transfer process in the indole(H20) clusters. Ab initio calculations of the indole-water potential energy surfaces are under way now, to elucidate this process in the heterocluster and to understand the difference with respect to the indole-ammonia complex. 

The performance of calixarenes as cation carriers through H20-organic solvent H20 liquid membranes has also been studied.137 In basic metal hydroxide solutions, the monodeprotonated phenolate anions complex and transport the cations, while [18]crown-6 does not, under the same conditions. Low water solubility, neutral complex formation and potential coupling of cation transport to reverse proton flux have been cited as desirable transport features inherent in these molecules.137... 

Phenol-water clusters are good models for the investigation of the photoinduced elementary processes occurring in living matter. Intracluster hydrogen transfer processes in phenol-water (Ph-W) complexes have extensively been studied in recent years, see refs [11-14] for reviews. Phenol-ammonia (Ph-A) clusters also have served as easily accessible and versatile models of intracluster hydrogen transfer dynamics [14,16]. It has been inferred by several authors that intracluster proton transfer occurs more readily in Ph-A clusters than in Ph-W clusters, but it has been a matter of debate whether the hydrogen or proton transfer occurs in the S excited state, or in the cluster cation, or in both [12,14],... 

W.-H. Fang, Theoretical characterization of the excited-state structures and properties of phenol and its one-water complex, J. Chem. Phys., 112 (2000) 1204—1211. 

Xo-type interactions and analyzed their energy components (electrostatic, induction, dispersion, and exchange repulsion energies). In addition, by studying the corresponding water-Y complexes, we compared them with phenol-Y complexes. 

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