Relative stability of keto-enol tautomers in 5,6-substituted uracils: Ab initio, DFT and PCM study

被引:31
作者
Lukmanov, Timur [1 ,2 ]
Ivanov, Sergey P. [2 ]
Khamitov, Edward M. [1 ]
Khursan, Sergey L. [2 ]
机构
[1] Bashkir State Univ, Ufa 450076, Russia
[2] Russian Acad Sci, Inst Organ Chem, Ufa Sci Ctr, Ufa 450054, Russia
关键词
Uracil; Tautomerism; Solvation; Ab initio; Solvation shell; NBO analysis; DENSITY-FUNCTIONAL THEORY; NUCLEIC-ACID BASES; MOLECULAR-STRUCTURE; GAS-PHASE; CONTINUUM; THYMINE; 5-FLUOROURACIL; DERIVATIVES; EQUILIBRIA;
D O I
10.1016/j.comptc.2013.09.005
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The relative stability orders in the tautomers of uracil and its derivatives (5-fluorouracil, 5-chlorouracil, 5-aminouracil, 5-hydroxyuracil, 5-methyluracil, 6-methyluracil, 5-hydroxy-6-methyluracil and 5-amino-6-methyluracil) were established using composite (G3MP2B3) and DFT (TPSS) methods. The stability orders were determined both in the gas phase and water solutions, taking into account specific and non-specific hydration. The primary solvation shell of uracils was modeled as a complex of a tautomer with 5 water molecules. An analysis of the factors which determine the stability of the enol forms of uracils was performed. The most important factor was found to be changes in the intramolecular conjugation at tautomerization. As was shown by the NBO analysis, the stabilization energy due to the n(N) -> pi* (or sigma*) interaction in the diketo tautomer is lost in the enol forms, but is partially compensated by an increase in the conjugation length. The effect of the substituent in the fifth position of the pyrimidine ring on the energy of tautomers is less prominent. It was shown that the hydration energy considerably differs for tautomers, and leads to substantial redistribution in the stability series of uracil tautomers. Both specific and non-specific solvation are of vital importance for stabilization of tautomers. (C) 2013 Elsevier B.V. All rights reserved.
引用
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页码:38 / 45
页数:8
相关论文
共 38 条
[1]   Toward reliable density functional methods without adjustable parameters: The PBE0 model [J].
Adamo, C ;
Barone, V .
JOURNAL OF CHEMICAL PHYSICS, 1999, 110 (13) :6158-6170
[2]   Gaussian-3 theory using density functional geometries and zero-point energies [J].
Baboul, AG ;
Curtiss, LA ;
Redfern, PC ;
Raghavachari, K .
JOURNAL OF CHEMICAL PHYSICS, 1999, 110 (16) :7650-7657
[3]   Microsolvation of Uracil and Its Conjugate Bases: A DFT Study of the Role of Solvation on Acidity [J].
Bachrach, Steven M. ;
Dzierlenga, Michael W. .
JOURNAL OF PHYSICAL CHEMISTRY A, 2011, 115 (22) :5674-5683
[4]   A QUANTUM-THEORY OF MOLECULAR-STRUCTURE AND ITS APPLICATIONS [J].
BADER, RFW .
CHEMICAL REVIEWS, 1991, 91 (05) :893-928
[6]   DENSITY-FUNCTIONAL THERMOCHEMISTRY .3. THE ROLE OF EXACT EXCHANGE [J].
BECKE, AD .
JOURNAL OF CHEMICAL PHYSICS, 1993, 98 (07) :5648-5652
[7]   MICROWAVE-SPECTRUM OF URACIL [J].
BROWN, RD ;
GODFREY, PD ;
MCNAUGHTON, D ;
PIERLOT, AP .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1988, 110 (07) :2329-2330
[8]   Hydration structure of uracil as studied by 1D and 2D heteronuclear Overhauser spectroscopy: evidence for the formation of a trihydrate in the first solvation shell [J].
Chahinian, M ;
Seba, HB ;
Ancian, B .
CHEMICAL PHYSICS LETTERS, 1998, 285 (5-6) :337-345
[9]   Ab initio study of solvated molecules: A new implementation of the polarizable continuum model [J].
Cossi, M ;
Barone, V ;
Cammi, R ;
Tomasi, J .
CHEMICAL PHYSICS LETTERS, 1996, 255 (4-6) :327-335
[10]   Hydration effect on the stability of the keto-enol tautomers of 5-hydroxy-6-methyluracil [J].
Dautova, I. F. ;
Ivanov, S. P. ;
Khursan, S. L. .
JOURNAL OF STRUCTURAL CHEMISTRY, 2009, 50 (06) :1104-1113