Hydrogen bonded molecular complexes

In solution, although solute contributions can generally be singled out, difficulties arise sometimes solvent-solute interactions may induce a shift of the solute absorption and consequently of its susceptibility or hydrogen bonded molecular complexes may modify the liquid structure. This situation has been studied both theoretically and experimentally by Zyss and Berthier (10) and by Ledoux and Zyss (13) in the case of urea derivatives in various solvents and in crystal showing the importance of environment considerations and thus the limitations of an oriented gas model for crystals. 

Barnes, A. J., Kuzniarski, J. N, S., and Mielke, Z., Strongly hydrogen-bonded molecular complexes studied by matrix-isolation vibrational spectroscopy. Part 2. Amine-hydrogen chloride complexes, J. Chem. Soc., Faraday Trans. 2 80,465-476 (1984). 

A theoretical analysis of the reaction kinetics was given in the study by Jodkowski et a/.31 A hydrogen-bonded molecular complex was found for the hydroxymethyl reaction channel. The formation of this complex may be a ratedetermining process in the two-step reaction mechanism of the H-abstraction from methyl group. On the other hand, the reaction channel which produces methoxy radicals is a simple metathesis reaction. The profile of the potential energy surface obtained by Jodkowski et al at the G2 level is shown in Fig. 14. 

A. J. Barnes and M. P. Wright, J. Chem. Soc. Faraday Trans. 2, 82, 153 (1986). Strongly Hydrogen-Bonded Molecular Complexes Studied by Matrix Isolation Vibrational Spectroscopy, Part 3. Ammonia-Hydrogen Bromide and Amine-Hydrogen Bromide Complexes. 

A) Structure of the drug sulfadimidine 9 and (B) hydrogen-bonded molecular complex between sulfadimidine and acetylsalicylic acid (aspirin) in the co-crystal. 

THE VIBRATIONAL DYNAMICS OF HYDROGEN BONDED MOLECULAR COMPLEXES AT THE STATE-TO-STATE LEVEL... 

Concluding this paragraph, we can confirm that although the complex of cytosine with water seems to be stable with respect to any thermal- or photo-induced PT reaction, the 2PMD H20 complex may indeed be the candidate of choice for an experimental detection of ESIPT reaction in a hydrogen bonded molecular complex. The possibility of generation of rare tautomeric forms of cytosine in photoinduced bimolecular secondary processes has been theoretically considered in Ref. [35]. 

The equilibrium of Eq.(2) between a hydrogen bonded molecular complex (MC) and a hydrogen bonded ion pair (IP) may be regarded as one kind of molecular complex - ion pair tautomerism. The formation of contact ion pairs is favoured under the influence of a medium but even the question of their occurrence already without medium influence is of fundamental chemical interest and has become a subject of intense theoretical and experimental investigation. 

We illustrate the occurrence of hydrogen-bonded molecular complexes and ion pairs as well as of equilibria between them by results first obtained by Barrow and Bell (1956/59) on pyridine and halogenated acetic acids. The study was carried out in solvents of low polarity using infrared spectroscopy. The reactions are highly sensitive to the... 

The system belongs to the normal type of hydrogen bonded molecular complexes forming a SM potential in the gas phase. In water, NH -HF is most stable as ionic complex NH +f7 However, most of the calculations using different levels of quantiim theory as well as different kinds of solvation models find a SM potential representing a molecular complex. An exception forms the application of the... 

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