Hydrogen bonding directionality

Figure 9. Distribution of hydrogen bond directionality with 4 -OH as acceptor (A) and donor(Q). Plot is of hydrogen bond torsion angle C3 -C4 -04 l. . . X.

Miscellaneous Soft-Template Methods Novel Y-junction PANI-NTs, accompanied with nanorods, have been selectively prepared using in situ self-assembly of water-soluble Fe304 nanoparticles coated with PEG(5)-nonylphenylether and cyclodextrin as templates and pH control in an aqueous medium [373]. A chemical oxidative route to synthesize oriented arrays of conducting PANI-NTs in HCl solution by hydrogen-bonding directionality in the presence of a crown ether derivative (CE-SO3K) has also been reported [374]. 

Figure 21 Hydrogen bonding directionality of bis-urea compounds with a...

D. The hydrogen bond directionality (or lone-pair directionality), which refers to the direction of approach of the proton donor A-H to proton acceptor B, is governed by the strength of charge transfer. Electrostatic energy is not the component that shows the largest angular dependence. 

Each of the pharmacophore queries consisted of one donor, one acceptor and one of the two hydrophobic points indicated in Figure 1.16. The directionality of hydrogen bonds was inferred from the X-ray structure and reasonably loose tolerances of 1.5 A were used for donor-acceptor distances and 2-2.5 A to the hydrophobe were chosen to allow for the flexibility seen across kinase structures and to maximise the diversity amongst the identified fragments. Four pharmacophore queries were completed and the results were combined. The chosen fragments were further filtered by molecular weight (between 150 and 250), 51og P (between 2.5 and —2.5) and the presence of... 

Both species exhibit the expected linear geometry that maximizes the dominant n- - a interaction. However, these isomers are rather perplexing from a dipole-dipole viewpoint. The dipole moment of CO is known to be rather small (calculated Fco = 0.072 D), with relative polarity C- 0+. 40 While the linear equilibrium struc-ture(s) may appear to suggest a dipole-dipole complex, robust H-bonds are formed regardless of which end of the CO dipole moment points toward HF This isomeric indifference to dipole directionality shows clearly that classical dipole-dipole interactions have at most a secondary influence on the formation of a hydrogen bond. 

The principal non-covalent interaction in molecule-based crystal engineering is the hydrogen bond. The reason for this preference is simple, the hydrogen bond is the strongest of the non-covalent interactions and possesses a high degree of directionality. Strength and directionality (namely transferability and repro-... 

In this context, the classical hydrogen bonds provide the best combination of strength and directionality, permitting rapid self-organization of molecular building blocks into extended regnlar structnres. This process is very efficient with respect to conventional snpramolecular synthesis nsing covalent bonds. 

In contrast to the TREN template, 75 with the NTA template preferred the h-cis configuration . This could be caused either due to the inverse directionality of the hydroxamate group, or, more plausibly, because the tripeptide is connected through the amino end, leading to opposite orientation of the hydrogen-bonding network. ... 

Leahy, D.E., Morris, J.J., Taylor, P.J. and Wait, A.R. (1992) Model solvent systems for QSAR. Part 3. An LSER analysis of the critical quartef . New light on hydrogen bond strength and directionality Journal of the Chemical Society-Perkin Transactions 2, 705-722. 

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