Hydrogen bonding cationic

The noncovalent interactions or van der Waals forces involved in supramolecular entities may be a combination of several interactions, e.g., ion-pairing, hydrophobic, hydrogen bonding, cation-Tr, tt-tt interactions, etc. They comprise interactions between permanent multipoles, between a permanent multipole and an induced multipole, and between a time-variable multipole and an induced multipole. 

In the dihydrochloride (602), the second molecule of acid is not firmly bound because of protonation of the second basic site by internal hydrogen bond formation. This would suggest that in the dipicrate, one mole of picric acid participates in salt formation, and that the second mole of picric acid is added to the hydrogen-bonded cation (LXI) forming a molecular complex. The existence of a monopicrate might thus serve to point out structures with steric inhibition of hydrogen bonding. 

Often hydrogen atoms cannot be located crystullogruphically if there are heavy atoms present. In u study of HiFjSbjFfi, the hydrogen bonded cation was found to have a structure of either ... 

Structural Data for Intermolecular Hydrogen-Bonded Cation Pairs... 

Evidence for the formation of such hydrogen-bonded cation pairs in solution has been obtained by three-phase vapor tensiometry studies on solutions of cis-Cr(bipy)2(H20)(0H)2+ in a saturated solution of barium nitrate (the total molality of chromium species was 0.1-0.2 m) (326, 330). It was shown that the equilibrium of Eq. (29) in concentrated solutions lies considerably to the right, and it was estimated that Kip-IM-1. 

It is noted that the formation of such hydrogen-bonded cation pairs corresponds well to results obtained in a study of the behavior of freshly precipitated chromic hydroxide (199). 

Only a few thermodynamic studies have been made of intermolecu-lar condensation reactions between mononuclear and relatively simple oligomeric species, and kinetic studies of such reactions have first been reported only quite recently. Charge effects seem to play a dominant role, although another important factor may be the formation of intermolecular hydrogen-bonded cation pairs. 

Mills, M.S., E.M. Thurman, and M.J. Pedersen (1993). Application of mixed-mode, sohd-phase extraction in environmental and clinical chemistry. Combining hydrogen-bonding, cation-exchange and Van der Waals interactions. J. Chromatogr., 629 11-21. 

Having introduced the major principles of complexation, association, and organization, it is important to review the physicochemical forces that lead to supramolecular ensemble formation. As mentioned above, supramolecular interactions are by definition noncovalent. In the order of the polarity of the partners involved, they comprise ionic or electrostatic interactions,17 18 ion-dipole interactions,19 dipole-dipole interactions, (ionic) hydrogen bonding, cation-tt and anion-tt interactions,... 

Nonbonded Repulsion van der Waals Radii Common Groups Ordered by Size Dipole Attractions Hydrogen Bonding Cation Pi-Complexes Donor-Acceptor... 

Mills, M. S. Thurman, E. M. and Pedersen, M. J. 1993. Mixed-mode solid-phase extraction Combining mechanisms of interaction hydrogen bonding, cation exchange, and reverse phase, J. Chromatog., 629 11-21. 

Figure 18 View down the hydrogen-bonded cationic chains in crystaiiine [DABCO][Co(CO)4]-THF the anions occupy the channeis and are iinked to the cations via C-H- -O hydrogen bonds. Reprinted with permission from Rivas, J. C. M. Brammer, L. Coord. Chem. Rev. 1999, 183, 143. 1999, Eisevier.

Dubois, R.H., Zaworotko, M.J. and White, P.S., Complex hydrogen-bonded cations - X-ray crystal-structure of [(CeH5CH2)NH3)4Cl][AlCl4]3 and its relevance to the structure of basic chloroaluminate room-tenperature melts, Inorg. Chem. 28 (11), 2019-2020 (1989). 

Fig. 11.15 Af-Alkyl ammonium resorcinarene halides (NARXs) with a strong circular hydrogen bond cation-anion seam [38]...

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