Naslov
Strong intramolecular hydrogen bonds. Part I. Vibrational frequencies of the OH group in some picolinic acid N-oxides predicted from DFT calculated potentials and located in the infrared spectra

Autori
Stare, Jernej ; Mavri, Janez ; Ambrožić, Gabriela ; Hadži, Dušan

Izvornik
Journal of Molecular Structure: THEOCHEM (0166-1280) 500 (2000); 429-440

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
hydrogen bonding ; DFT calculations ; potential functions ; infrared spectra

Sažetak
Hydrogen bonding in picolinic acid N-oxide (I), its 4-nitro (III), 4-methoxy (IV), 4-amino (V) derivatives and in quinaldic acid N-oxide (II) was characterized by calculations (B3LYP/6-31G(d)) of metric parameters, H-bond energies and one-dimensional proton potential functions with vibrational energy levels. Solvent effects were estimated by the SCRF PCM method of Tomasi and coworkers (J. Tomasi, M. Persico, Chem. Rev. 94 (1994) 2027). The potential functions an strongly asymmetric with the energy minimum placed near the carboxylic oxygen. The inflection near the NO oxygen develops into a second, shallower minimum under the SCRF. Empirical assignments of the OH stretching and bending modes were made for (I)-(IV). The stretchings of (I, II) and (IV) in various solvents are observed in the region 1600-1300 cm(-1), but near 2600 cm(-1) for (III). The calculated and observed frequencies are in fairly good agreement with theoretical predictions reflecting the electronic effects of the substituents upon the H-bond strength. The observed trends in the solvent effects upon various parameters characterizing the H-bonding also correspond to predictions.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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