Quantum-chemical study of energy surface and the minimum-energy reaction path of the proton transfer along O-H...N hydrogen bond in acetic acid-imidazole x 2 H2O system

1982 ◽  
Vol 47 (7) ◽  
pp. 1893-1896 ◽  
Author(s):  
Milan Remko
Keyword(s):  
Hydrogen Bond ◽  
Acetic Acid ◽  
Proton Transfer ◽  
Quantum Chemical ◽  
Energy Surface ◽  
Reaction Path ◽  
Minimum Energy ◽  
Quantum Chemical Study ◽  
Energy Minimum ◽  
Energy Reaction

The semi-empirical quantum-chemical PCILO method has been used for calculation of the energy surface of the proton transfer along the O-H...N hydrogen bond in acetic acid-imidazole . 2 H2O system. The PCILO calculations gave the energy surface with two minima. The most stable minimum corresponds to the O-H...N hydrogen bond and has been found at the distances RH...N = 0.149 nm and RO...N = 0.107 nm. According to the PCILO calculations the proton transfer is accompanied by significant changes in the O...N distance. The second energy minimum corresponding to the proton transfer O-...NH+ complex has been found at RH...N = 0.10 nm and RO...N = 0.30 nm. The approximative minimum energy reaction path for the proton transfer has been calculated by the procedure developed by Muller and Brown. The calculated energy barrier represents a value 376.15 kJ/mol. The second energy minimum lies higher by 246 kJ/mol.

PCILO study of hydrogen bond and proton transfer in systems 1-methylthymine-acetamide and 1-methylthymine-acetic acid

1981 ◽  
Vol 46 (4) ◽  
pp. 957-962 ◽  
Author(s):  
Milan Remko
Keyword(s):  
Hydrogen Bond ◽  
Acetic Acid ◽  
Hydrogen Bonds ◽  
Proton Transfer ◽  
Quantum Chemical ◽  
Potential Functions ◽  
Double Proton Transfer ◽  
Proton Potential ◽  
Pcilo Method

Complexes containing two hydrogen bonds of the systems 1-methylthymine-acetamide and 1-methylthymine-acetic acid have been studied by the quantum-chemical PCILO method. In accordance with experiment our PCILO calculations have shown that acetic acid forms stronger hydrogen bonds than acetamide with 1-methylthymine. Further the PCILO method has been used to study of double proton transfer in O-H...O and N-H...O bonds of the complexes 1-methylthymine-acetamide and 1-methylthymine-acetic acid. Using equilibrium O...O and N...O distances, the PCILO calculations have given one-minimum proton potential functions. The proton transfer has not been observed. At somewhat longer N...O and O...O distances (0.30 nm) the PCILO calculations indicate a second minimum as a shoulder.

scholarly journals Complexation of Cu(BF4)2 with 3-hydroxyflavone in acetonitrile: quantum chemical calculation

2018 ◽  
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Atom ◽  
Intramolecular Hydrogen Bond ◽  
Quantum Chemical ◽  
Phenyl Ring ◽  
Fluorine Atom ◽  
Quantum Chemical Study ◽  
Hydroxyl Group ◽  
Chemical Calculation ◽  
Intramolecular Hydrogen

In the article the results of the quantum chemical study of copper (II) solvato-complexes with acetonitrile (AN), tetrafluoroborate anion (BF4–) and 3-hydroxyflavone (flv) of the composition [Cu(AN)6]2+, [Cu(BF4)(AN)5]+, [Cu(flv)(AN)5]2+, [Cu(flv)(BF4)(AN)4]+ are presented. Calculations were done using density function theory (DFT) on the M06-2X/6-311++G(d,p) level of theory. Obtained results were interpreted in terms of complexes geometry and topology of electron density distribution using non-covalent interactions (NCI) approach. It was shown that flv molecule is a monodentate ligand in copper (II) complexes and coordinates central atom via carbonyl oxygen. Intramolecular hydrogen bond that exists in an isolated flv molecule was found to be broken upon [Cu(flv)(AN)5]2+ complex formation. In [Cu(flv)(AN)5]2+ complex, a significant rotation of phenyl ring over the planar chromone fragment was spotted as a consequence of intramolecular hydrogen bond breaking. Upon inclusion of BF4– anion to the first solvation shell of Cu2+, an intracomplex hydrogen bond was formed between hydrogen atom of hydroxyl group of flv molecule and the closest fluorine atom of BF4– anion. NCI analysis had shown that a hydrogen bond between hydrogen atom of hydroxyl group of flv molecule and the closest fluorine atom of BF4– anion is significantly stronger than intramolecular hydrogen bond in an isolated flv molecule. In addition, flexible phenyl ring of flv molecule in [Cu(flv)(BF4)(AN)4]+ complex was found to be internally stabilized by the weak van der Waals attraction between oxygen atoms of chromone ring and phenyl hydrogens. These evidences led to a conclusion that [Cu(flv)(BF4)(AN)4]+ complex is more stable, comparing to the in [Cu(flv)(AN)5]2+ complex.

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