The nearly linear relationship between hydrogen-bond strength at the CCSD(T)/Aug-cc-pVTZ level and the electron density at the bond critical point in the atoms-in-molecules theory provides a practical means of calculating the hydrogen-bond strength in liquid water. A statistical analysis of the hydrogen-bonds obtained from Car-Parrinello molecular dynamics simulations shows that the strengths of hydrogen bonds in liquid water conform to a Gaussian distribution. Considering supercooled (250 K) water to have a fully coordinated (icelike) local tetrahedral configuration, we show that the local structure of liquid water is partly distorted tetrahedral in normal liquid water and even in superheated water.

Key indicatorsSingle-crystal X-ray study T = 293 K Mean '(C±C) = 0.006 A Ê R factor = 0.057 wR factor = 0.102 Data-to-parameter ratio = 12.4For details of how these key indicators were automatically derived from the article, see

Supramolecular assemblies of 2,2′‐biimidazole with 5‐sulfosalicylic acid and 3,4,5‐trihydroxybenzoic acid, have been synthesized and characterized by single‐crystal X‐ray diffraction methods. Both the two proton‐transfer compounds of 2,2′‐biimidazole with 3‐carboxy‐4‐hydroxybenzenesulfonic acid (5‐sulfosalicylic acid, 5‐SSA) [namely bis(2‐(2‐1H‐imidazolyl)‐1H‐imidazolium) 4‐hydroxybenzene‐3‐carboxylate‐1‐sulfonate monohydrate, 2(C6H7N4)+· C7H4O6S2−·H2O, (I)] and 3,4,5‐trihydroxybenzoic acid [namely 2,2′‐bi‐1H‐imidazolium bis(3,4,5‐trihydroxybenzoate) tetrahydrate, C6H8N42+·2(C7H5O5)−·4(H2O), (II)] feature extensively hydrogen‐bonded three‐dimensional network structures having significant interlayer π‐ π interactions between the cation and anion species. In I, a 5‐SSA2− dianionic species results from deprotonation of both the sulfonic and the carboxylic acid groups, all available O‐atom acceptors interact with all cation and water molecule donors by hydrogen bonds. In II, the formula unit displays a crystallographic inversion symmetry. The structural information about the two complexes between 2,2′‐biimidazole compound and benzenecarboxylic acids obtained in this work will be particularly important for the rational design of supramolecular organic functional materials.

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