ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEvidence for resonance-assisted hydrogen bonding. 4. Covalent nature of the strong homonuclear bond. Study O-H--O system by crystal structure correlation methodsPaola Gilli, Valerio Bertolasi, Valeria Ferretti, and Gastone GilliCite this: J. Am. Chem. Soc. 1994, 116, 3, 909–915Publication Date (Print):February 1, 1994Publication History Published online1 May 2002Published inissue 1 February...

Unlike normal chemical bonds, hydrogen bonds (H-bonds) characteristically feature binding energies and contact distances that do not simply depend on the donor (D) acceptor (:A) nature. Instead, their context can lead to large variations even for a same donor−acceptor couple. As striking example, weak HO−H···OH2 bond in neutral water changes, acidic or basic medium, 6-fold stronger 15% shorter [H2O···H···OH2]+ [HO···H···OH]− bonds. This surprising behavior, sometimes called H-bond puzzle,...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEvidence for resonance-assisted hydrogen bonding. 2. Intercorrelation between crystal structure and spectroscopic parameters in eight intramolecularly bonded 1,3-diaryl-1,3-propanedione enolsValerio Bertolasi, Paola Gilli, Valeria Ferretti, Gastone GilliCite this: J. Am. Chem. Soc. 1991, 113, 13, 4917–4925Publication Date (Print):June 1, 1991Publication History Published online1 May 2002Published inissue 1 June...

The resonance-assisted hydrogen bond (RAHB) is a model of synergistic interplay between π-delocalization and hydrogen-bond (H-bond) strengthening originally introduced (Gilli, G.; Bellucci, F.; Ferretti, V.; Bertolasi, V. J. Am. Chem. Soc. 1989, 111, 1023; Gilli, P.; G. 1991, 113, 4917) for explaining the abnormally strong intramolecular O−H···O bonds formed by ···OC−CC−OH··· β-enolone fragment I which are typical β-diketone enols. applicability this to N−H···O number heteroconjugated...

The tautomeric.O=C-C=N-NH triplebond --> <-- HO-C=C-N=N ketohydrazone-azoenol system may form strong N-H O/O-H N intramolecular resonance-assisted H-bonds (RAHBs) which are sometimes of the low-barrier H-bond type (LBHB) with dynamic exchange proton in solid state. problem competition these compounds is studied here through variable-temperature (100, 150, 200, and 295 K) crystal-structure determination pF = 1-(4-F-phenylazo)2-naphthol oF 1-(2-F-phenylazo)2-naphthol, two molecules that, on...

Beta-diketone enols are known to form intramolecular...O=C-C=C-OH... resonance-assisted hydrogen bonds (RAHBs) with O...O distances as short 2.39-2.44 A. However, even the most accurate diffraction studies have not been able assess certainty whether these very strong (H-bonds) be described proton-centered O...H...O in a single-well (SW) potential or dynamic static mixing of two O-H...O <= => O...H-O tautomers double-well (DW) one. This contribution reexamines problem and shows that methods...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEnthalpy-entropy compensation in drug-receptor bindingPaola Gilli, Valeria Ferretti, Gastone and Pier Andrea BoreaCite this: J. Phys. Chem. 1994, 98, 5, 1515–1518Publication Date (Print):February 1, 1994Publication History Published online1 May 2002Published inissue 1 February 1994https://pubs.acs.org/doi/10.1021/j100056a024https://doi.org/10.1021/j100056a024research-articleACS PublicationsRequest reuse permissionsArticle...

Abstract The fact that hydrogen bonding is normally stronger than other nonbonding attractive forces can be exploited for the rational design of molecular crystals with known packing features and specific physical properties (crystal engineering). In present paper problem obtaining homodromous chains controlled by strong O–H ⃛ O interactions investigated, particular attention being paid to β‐ , is, infinite hydrogen‐bonded β‐diketone enol fragments OCCCOH ⃛, which are linked...

Phenyl-substituted 1-arylazo-2-naphthols (AAN) display ···HNNCCO··· ⇌ ···NNCCOH··· ketohydrazone−azoenol tautomerism and can form intramolecular resonance-assisted H-bonds from pure NH···O to N···HO through tautomeric dynamically disordered bonds according the electronic properties of their substituents. Three compounds this series (m-OCH3-AAN = mOM; p-Cl-AAN pCl; p-NMe2-AAN pNM2) have been studied by X-ray crystallography at four temperatures (100−295 K), showing that remarkably short...

The crystal structures of seven compounds forming intermolecular N--H..-O hydrogen bonds connected by 7r-conjugated systems are reported: (1) 2-methyl-Nphenylprop-2-enamide; (2) 2-methyl-N-benzylprop-2-enamide; (3) p-methoxyacetoacetanilide; (4) dibenzamide; (5) 3-methyl-4-(3'-methyl- l'-phenylpyrazol-5'-yl)- 1 phenyl-4-pyrazolin-5-one; (6) 3-anilino-2-chloro-l,4naphthoquinone; (7) 3-phenethyl-7-methyl-5H-pyrazolo[4,3-d]-l,2,3-triazin-4(3H)-one. 32 other related surveyed in order to...

The structures of picric acid and 14 its adducts with N-bases were determined by X-ray diffraction. All intermolecular contacts shorter than the sum van der Waals radii retrieved, classified as 81 conventional X−H···:Y (X,Y = N,O) 108 weaker C−H···:O H-bonds 49 C/N←:O π*←n or π*(k)←n four C←:C π*←π electron donor−acceptor (EDA) interactions, carefully scrutinized to single out general rules (if any) 242 are conforming to. X···Y distances related EHB energies bonds found correlate ΔpKa...

The β-diketone enol (or enolone) HO-C=C-C=O fragment produced by enolization of β-diketones is known to form strong intramolecular O-H...O hydrogen bonds where the decrease O...O contact distance (up 2.40 A) correlated with increased π-delocalization O-C=C-C=O heteroconjugated system; phenomenon has been interpreted resonance-assisted hydrogen-bonding (RAHB) model [Gilli, Bellucci, Ferretti & Bertolasi (1989). J. Am. Chem. Soc. 111, 1023-1028; Bertolasi, Gilli, Gilli (1991). 113, 4917-1925]

The crystal structures of six β-ketoarylhydrazones are reported: 1,(Z)-2-(2-bromophenylhydrazono)-3-oxobutanenitrile; 2, (Z)-2-(2-methylphenylhydrazono)-3-oxobutanenitrile; 3, (E)-methyl-2-(2-methoxyphenylhydrazono)-3-oxobutanoate; 4, E, methyl-2-(2-cyanophenylhydrazono)-3-oxobutanoate; 5, (Z)-methyl-2-(4-cyanophenylhydrazono)-3-oxobutanoate; 6, pentane-2,3,4-trione-3-(2-carboxyphenylhydrazone). All them form intramolecular hydrogen bonds assisted by resonance (RAHB), with N···O distances in...

A number of crystal structures molecules where the π-conjugated · O C–CC–OH β-diketone enol group is found to form intramolecular O–H hydrogen bonds and for which 1H NMR spectroscopic data were known are discussed. Five these structures, determined by X-ray diffraction techniques, reported other 42 retrieved from Cambridge Structural Database. It shown that all descriptors hydrogen-bond strength [d(O O) shortening, increased enolic chemical shift, δ(OH), π-delocalization hydrogen-bonded...

The crystal structures of five propane-1,2,3-trione arylhydrazones are reported. All molecules chelated to form a six-membered π-conjugated ring via strong intramolecular N–H ⋯ O hydrogen bonding. N bond distances correlated with the resonance entity within and spectroscopic data such as ν(NH)IR frequencies δ(NH)1H NMR chemical shifts λmax UV absorption bands charge transfer from hydrazone carbonyl group. structural variations parameters modulated by electronic properties substituents on...

Preparation and single-crystal X-ray structure determination of three co-crystals hydrogen squarate, HSQ(-), with 2-aminopyrimidine, 3-aminopyridine 4-aminopyridine, one SQ(2-), 8-aminoquinoline are reported. Their crystal packings analyzed discussed in terms the intermolecular O--H...O, N--H...O/N C--H...O bonds formed. Although fine details supramolecular architecture barely rationalizable, comparative analysis data makes it possible to suggest some simple rules that may be general...