Zilberg, Shmuel and Dick, Bernhard (2016) Finding structural principles for strong hydrogen-bonds: Less stable tautomers form dimers with stronger hydrogen bonds. CHEMISTRYSELECT, 1 (2). pp. 195-200. ISSN 2365-6549,
Full text not available from this repository. (Request a copy)Abstract
Two tautomeric forms of a heterocyclic monomer -the preferable M-0 and the one at higher energy, M*, can form three different kinds of hydrogen-bonded dimers: (MM0)-M-0, (MM)-M-0* and M* M*. The lowest-energy dimer (MM0)-M-0 and the highest one M* M* are transformed into each other by double proton transfer (DPT). By the corresponding concerted process, the mixed complex (MM)-M-0* is converted to the equivalent isomer M*M-0. It cannot return to the low-energy form (MM0)-M-0 without breaking the hydrogen bonds. A quantum-chemical study of dimers of tautomeric monomers (7-azaindole, 1-azacarbazole, formamide) and non-symmetric complexes including the DNA adenine-thymine pair shows increasing hydrogen bond stabilization with increasing energy of the dimer or complex, respectively. The least stable dimer M*M* has a small barrier for reverse DPT (< 2 kcal mol(-1)), rendering an experimental observation difficult. This should not be the case for the mixed complex (MM)-M-0* which is kinetically stable (Delta E-/- 6 > 8 kcal mol(-1)). Hence the mixed dimer is a perspective candidate for the experimental verification of hydrogen bond-stabilization in less stable tautomers. Theory predicts softening of the OH/NH bonds and a strong down shift of the OH/NH frequencies by > 200 cm(-1) in the less stable complexes.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | DOUBLE-PROTON-TRANSFER; LASER EXCITATION FLUORESCENCE; MODEL BASE-PAIRS; EXCITED-STATE; ENZYMATIC CATALYSIS; 7-AZAINDOLE DIMER; 1-AZACARBAZOLE; DYNAMICS; 3-METHYLPENTANE; TEMPERATURE; Hydrogen Bond; Strong Hydrogen Bonding; Double Proton Transfer; Tautomers |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry III - Physical Chemistry (Molecular Spectroscopy and Photochemistry) > Prof. Dr. Bernhard Dick |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 14 Mar 2019 11:19 |
| Last Modified: | 14 Mar 2019 11:19 |
| URI: | https://pred.uni-regensburg.de/id/eprint/2504 |
Actions (login required)
 |
View Item |
