Water dimer anion

Fig. 7.5 Time-dependent behavior of the adiabatic state populations during the collision of a water dimer anion and a water monomer as shown in Fig. 7.4. Black solid line, gray dashed line, and thin gray dotted line represent that of the ground, first excited, and second excited states, respectively. Changes in the populations of these states indicate nonadiabatic transitions. (Reprinted with permission from T. Yonehara et of., Chem. Rev. 112, 499 (2012)).

Fig. 7.9 Selected snapshots of the spatial distribution of SOMO (upper row), LUMO (middle row), and the real part of SONO (bottom row) for the collision of fully deuterized molecules (water dimer anion and water monomer). Green and red smfaces indicate...

Y. Bouteiller, C. Desfran9ois, H. Abdoul-Carime, and J. P. Schermann,/. Chem. Phys., 105, 6420-6425 (1996). Structure and Intermolecular Motions of the Water Dimer Anions. 

H. Tachikawa and M. Ogasawura,/. Phys. Chem., 94, 1746-1750 (1990). Ab Initio Molecular Orbital Study on Water Dimer Anions. 

F, the anion is bound to a water dimer, but occupying two different binding sites. Structures D and E are both stable against dissociation, whereas F is not. Because of the polarizing effect of F , the hydrogen bond to the second water molecule is no longer efficient and complex F is found to dissociate spontaneously into H2O and H2O-F-. The corresponding structural data can be found in Table 23. 

An ab initio study on the structure and splitting of the uracil dimer anion radical (see Scheme 3-66 and keep R = H) gives preference to the one-step mechanism (Voityuk Roesch 1997). Anion radical anions of the pyrimidine dimers cleave with rate constants in excess of 106 sec 1 (Yeh Falvey 1991). However, the cyclobutyl dimer of a quinone, dithymoquinone, also cleaves upon single-electron reduction but much more slowly than the pyrimidine dimers (Robbins Falvey 1993). It is truly an unresolved issue as to why the anion radical cleavage depicted in Scheme 3-66 is so facile. Water participation can probably decrease the barrier of the cycloreversion on physiological conditions (Saettel Wiest 2001). 

Studying the ESPT of hydroxy aromatic sulfonates, Huppert and co-workers [40-44] suggested an alternative model based on the geminate proton-anion recombination, governed by diffusive motion. The analysis was carried out by using Debye-Smoluchowskii-type diffusion equations. Their ESPT studies in water-methanol mixtures showed that solvent effects in the dissociation rate coefficient are equal to the effects in the dissociation equilibrium constant [45], 4-Hydroxy-1-naphthalenesulphonate in a water-propanol mixture as the solvent system has been found to behave somewhat differently than water-methanol or water-ethanol media, with a possible role of a water dimer [46,47],... 

Meot-Ner, M.(Mautner), Sieck, L.W. Relative acidities of water and methanol and the stabilities of the dimer anions. J. Phys. Chem. 1986, 90, 6687-90. 

Figure 19 (see color section). Orbital diagram of the interaction between two OH anions with their O - -O contact at the same geometry than the O H- -O bond in the water dimer. See text for details. 

From a historical perspective, the first unambiguous observation of dipole states came from the group of Kit Bowen (Johns Hopkins) in 1990, who studied the important water dimer dipole anion. The Bowen group has also studied ground state dipole-bound anions produced by electron attachment under high-pressure nozzle-jet expansion condition. They have also used photodetachment photoelectron spectroscopy to determine electron affinities for a number of the molecules shown in Figure 4. 

An important general reaction of enolate ions involves nucleophilic addition to the electrophilic carbonyl carbon atom of the aldehyde or ketone from which the enolate is derived. A dimeric anion 18 results, which may then be neutralized by abstraction of a proton to produce a p-hydroxycarbonyl compound, 19 (Eq. 18.10). If the reaction is performed in hydroxylic solvents such as water or an alcohol, the source of the proton may be the solvent, whose deprotonation will regenerate the base required for forming the enolate ion. Thus, the overall process is catalytic in the base that is used. 

The initial conditions for SET dynamics were chosen as follows. Let us consider a system with three water monomers with an excess electron one dimer anion plus one neutral molecule at the beginning. The first two monomers (ml and m2) are placed in the configuration of the planar anion dimer. The other monomer (m3) is set to approach the dimer from a... 

Fig. 7.4 Configuration of collision between the planar dimer anion consisting of ml and m2 and a water monomer m3. (Reprinted with permission from T. Yonehara et al., Chem. Rev. 112, 499 (2012)).

Fig. 24.16 Structure of the tetrakis(guanosine)calix[4]arene (39) and the schematic representation of the G-quartet self-assembled dimer. Anion binding by the amide protons and cation complexation by the G-quartet are presented separately. Water molecules in the complex core necessary for the self-assembly are omitted for clarity [45]...

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