Bistable hydrogen bonds

It can be observed in Fig. 1 that the molecular orientation within a hydrogen-bonded aggregate formed by a bistable hydrogen bond can favour one of the H-sites. Naturally, this coupling also works in the opposite direction— the H-site modifies the arrangement of the H-bonded molecules or ions. This interdependence can be used for determining which of the H-sites is... 

Szafrahski, M., Katrusiak, A. and McIntyre, G.J. (2002). Ferroelectric order of parallel bistable hydrogen bonds. Phys. Rev. Lett. 89, 215507-1-4. 

The molecular or ionic orientation within a hydrogen-bonded aggregate formed by a bistable hydrogen bond can favour one H site this interdependence is illustrated... 

Szafrahski, M. and Katrusiak, A. (2000). Thermodynamic behaviour of bistable NH -N hydrogen bonds in monosalts of l,4-diazabicyclo[2.2.2]octane. Chem. Phys. Lett. 318,427-432. Katrusiak, A. and Szafrahski, M. (1999). Ferroelectricity in NH-N hydrogen-bonded crystals. Phys. Rev. Lett. 82, 576-579. 

Below, the interdependence of macroscopic properties on these microscopic features is described briefly for 0H---0 hydrogen-bonded crystals. The bistable homonuclear hydrogen bonds are convenient examples to explain the structure-property relations, because the H atom is readily locatable in the structure in this way the mechanism of microscopic transformations can be followed. At the same time, H-bonded systems are important for understanding transformations of molecular and biological systems, or for prospective practical applications. At present there appear to exist no practical applications of electronic devices based on hydrogen-bonded materials. 

Altieri, A., Bottari, G., Dehez, F., Leigh, D. A., Wong, J. K. Y. and Zerbetto, F., Remarkable positional discrimination in bistable light- and heat-switchable hydrogen bonded molecular shuttles, Angew. Chem., Int. Ed. Engl, 2003, 42, 2296-2300. 

One of the most widely used supramolecular interactions in the field of mechanically interlocked molecules, so-called mechanostereochemistry, is that of the strong hydrogen bonds between ammonium ions and crown ethers, which were first reported by Stoddart and coworkers in the mid-1990s. This versatile interaction has fonnd nse in the construction of a myriad of interlocked systems and bistable molecules. 

A bistable porphyrin-containing [2]rotaxane R3 is synthesized with a shuttling benzylic-amide macrocycle mechanically locked onto the thread subunit via hydrogen bonding with two potential stations, as shown in Figure 5. This macrocycle consists of two pyridine groups, which would be easily coordinated with zinc porphyrin. The Zn(n) coordination of porphyrin moiety on the thread... 

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