Interplay between steric and electronic factors in determining the strength of intramolecular resonance-assisted NH···O hydrogen bond in a series of β-ketoarylhydrazones

Linear‐to‐Turn Conformational Switching Induced by Deprotonation of Unsymmetrically Linked Phenolic Oligoamides

“…The bifurcated hydrogen bond is stronger and shifts the signal for NH more downfield than a single hydrogen bond would do. [21] No NOE correlations were observed for any of the NH protons in CDCl 3 or CD 3 CN. The results also show that the amide NH protons do not direct to aromatic protons but rather to phenolate oxygen anions.…”

Structural stability of diclofenac vs. inhibition activity from ab initio molecular dynamics simulations. Comparative study with ibuprofen and ketoprofen

“…N-H· · · O attractive interaction is known as strong (resonance-assisted) hydrogen bond [13]. The structural parameters of intramolecular N-H· · · O H-bond for β-ketoarylhydrazones are in the range of 1.76-2.32Å and 99-140°for the H· · · O distance and NHO angle, respectively [14]. Simultaneously, the energy of this H-bond can equal even 60 kJ/mol.…”

Quantum chemical simulations of solvent influence on UV–vis spectra and orbital shapes of azoderivatives of diphenylpropane-1,3-dione

“…Theoretically ADB can exist in three tautomeric forms (enol-azo, keto-azo and hydrazo) [8][9][10][11][12][13] with conjugated donor--acceptor motif, which already made them promising candidates for such applications as bistate molecular switches [14][15][16][17][18][19][20][21], optical recording media and spin-coating films [22,23] or photoluminescent [24] materials. In our recent work [11] we have found that ADB containing a hydroxyl group in ortho-position to the hydrazo group and formed from the unsymmetrical ␤-diketones, exist in solution in two distinct tautomeric forms namely enol-azo and hydrazo-, and that a ratio between these forms depends on the solvent used as well as on temperature.…”

“…On the other hand, it was shown that in the solid state these ADB compounds are stabilized only in hydrazo form [11]. It was assumed that the tautomers in solution are stabilized by a strong intramolecular resonance assisted hydrogen bond (RAHB), and that the tautomeric balance can play an important role for many applications involving subtle transitions [14][15][16][17][18][19][20][21].…”