Using the freon mixture CDF(3)/CDClF(2) as solvent we have been able to measure the (1)H and (15)N NMR spectra of the doubly (15)N labeled 2,2'-bipyridinium cation (BpyH(+)) at temperatures down to 115 K. The obtained NMR parameters strongly depend on the type of counteranions indicating the formation of ion pairs. In the case of the bulky poorly coordinating tetrakis[3,5-bis(trifluoromethyl)ph...

Control of intermolecular interactions is integral to harnessing self-assembly in nature. Here we demonstrate that control of the competition between hydrogen bonds and halogen bonds, the two most highly studied directional intermolecular interactions, can be exerted by choice of solvent (polarity) to direct the self-assembly of co-crystals. Competitive co-crystal formation has been investigate...

New Schiff-base compound (E)-4-methoxy-N-(4-hydroxybenzylidene) aniline has been synthesized from the reaction of 4-hydroxybenzaldehyde with 4-methoxyaniline in methanol at 50ºC, and has been characterized by using elemental analysis and FT-IR spectroscopy. The crystal structure of the title compound has been determined by single crystal X-ray diffraction study. The title compound crystallizes ...

Colorless crystals of l-alanine hydrochloride monohydrate, C(3)H(8)NO(2) (+)·Cl(-)·H(2)O, were obtained from a powder sample that had been left standing in a refrigerator for a few years. The structure displays several inter-molecular hydrogen bonds: the hydroxyl O atom is involved in a single hydrogen bond to the chloride anion, while the ammonium group forms one hydrogen bond to the chloride ...

The effect of pressure on the crystal structure of salicylaldoxime has been investigated. The ambient-pressure phase (salicylaldoxime-I) consists of pairs of molecules interacting through oximic OH...O hydrogen bonds; taken with phenolic OH...N intramolecular hydrogen bonds, these dimers form a pseudo-macrocycle bounded by an R4 4(10) motif. The dimers interact principally via pi...pi stacking ...

The PM3 semiempirical quantum-mechanical method was found to systematically describe intermolecular hydrogen bonding in small polar molecules. PM3 shows charge transfer from the donor to acceptor molecules on the order of 0.02-0.06 units of charge when strong hydrogen bonds are formed. The PM3 method is predictive; calculated hydrogen bond energies with an absolute magnitude greater than 2 kcal...

The PACHA (Partial Atomic Charges and Hardnesses Analysis) formalism is applied to various supramolecular assemblies of water molecules. After a detailed study of all available crystal structures for ice polymorphs, we shown that the hydrogen bond strength is roughly constant below 1 GPa and considerably weakened above that value. New hydrogen bond patterns are proposed for ice IV, V, and VI af...

Hydrogen bonding underpins the properties of a vast array of systems spanning a wide variety of scientific fields. From the elegance of base pair interactions in DNA to the symmetry of extended supramolecular assemblies, hydrogen bonds play an essential role in directing intermolecular forces. Yet fundamental aspects of the hydrogen bond continue to be vigorously debated. Here we use dynamic fo...

Terahertz time-domain spectroscopy (THz-TDS) is used to study the intra- and intermolecular vibrational modes of aromatic carboxylic acids, for example, o-phthalic acid, benzoic acid, and salicylic acid, which form either intra- or intermolecular hydrogen bond(s) in different ways. Incorporating the target molecules in nano-sized spaces in mesoporous silicate (SBA-16) is found to be effective f...