Hydrogen-bonded dimers, intermolecular

The carboxyl functions in the new structures are buried within the clefts in a manner that discourages the formation of the intermolecular hydrogen bonded dimers which are usually observed in the solution and solid phases. Unusual acid-base behavior is one consequence. In the smallest system 11 (represented by the benzene spacer) a tremendous difference in pKa s (6 units) can be observed for the two ionizations 14). 

N. Borho, M. A. Suhm, K. Le Barbu Debus, and A. Zehnacker, Intra vs. intermolecular hydrogen bonding Dimers of alpha hydroxyesters with methanol. Phys. Chem. Chem. Phys. 8, 4449 4460 (2006). 

L.F. Pacios, Change with the intermolecular distance of electron properties of hydrogen bond dimers at equilibrium and non-equilibrium geometries. Struct. Chem. 16, 223-241 (2005)... 

Figure 5.6 Hydrogen-bonded dimer of a tetra-tolylurea calix[4] arene. Stick models based on molecular modeling (a) and X-ray structures (b), illustrating possible intra- and intermolecular connections (a- and p-connections).

Soper, P.D., Fegon, A.C., and Flygare, W.H. (1981) Microwave rotational spectrum, molecular geometry, and intermolecular interaction potential of the hydrogen-bonded dimer OC-HC1. ). Chem. Phys., 74, 2138-2142. 

Many carboxylic acids in gases and condensed states form dimers connected by a couple of hydrogen bonds (Fig. 2). The said acids are often treated as model systems for the study of spectra of hydrogen bonds [66], intermolecular... 

In this study, we have chosen the supermolecule approach and have used the semi-empirical quantum mechanical method called PCILO (Perturbative Configuration Interaction using Localized Orbitals) (16) to calculate intermolecular interactions. This method has recently been used successfully to calculate the intermolecular energies and geometries of hydrogen-bonded dimers of hydrocarbons and water (17,18). H-bonded complexes are particularly well characterized by this method (19). 

O. Galvez, P. C. Gomez, and L. F. Pacios, Variation with the intermolecular distance of properties dependent on the electron density in hydrogen bond dimers, J. Chem. Phys. 115, 11166-11184(2001). 

Hence, the double-proton transfer was assumed to proceed via a concerted mechanism, with the one-dimensional kinetic-energy matrix appropriate to one particle of twice the proton mass. A similar model is widely used to analyze the vibrations of cyclic hydrogen-bonded dimers (for example, see Ref. [59]). The O -O coordinate in this case symbolizes the intermolecular stretching of a doubly H-bonded system. The problem of the double-proton transfer for the benzoic acid dimer is thereby reduced to a problem conceptually similar to that for a single O -H -O entity except for the denoted light atom mass and consequences of the asymmetric 2D PES. 

R. Czerminski, Int. J. Quantum Chem., 31,649 (1987). Intermolecular Interactions Reliability of Results Obtained for Small Hydrogen Bonded Dimers by Claverie s Method. 

With the combination of the covalent bond forming capability of the metal ion and the inherent capability of the ligand for formation of complementary hydrogen bonds, a diversity of H-bonded structures has been obtained, including intramolecular hydrogen-bonded monomers (148), intermolecular hydrogen-bonded dimers, tetramers (149-151) and polymers having one-dimensional chain (152), two-... 

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