Reaction Force Analysis of the Effect of Mg(II) on the 1,3 Intramolecular Hydrogen Transfer in Thymine

Abstract

The 1,3 intramolecular hydrogen transfer reaction in free thymine and in Mg(II)-thymine have been studied at the density functional theory level. The mechanism of intramolecular proton transfer in these systems emerges from the analysis of the reaction force profile along the reaction path; it is rationalized in terms of structural and electronic reorganizations that take place during the chemical transformation. Results show that the presence of Mg(II) monocoordinated to thymine activates the hydrogenic motion by inducing structural and electronic changes in the molecular backbone. In the metallic complex, it is found that the hydrogen transfer is followed by a relaxation process that facilitates the metal cation migration to form a bicoordinated complex.

The performance of methallyl nickel complexes and boron adducts in the catalytic activation of ethylene: a conceptual DFT perspective

“…Chemical potential characterizes the tendency of electrons to escape from the equilibrium distribution and is related to Mulliken's [39] electronegativity (χ) [36,[39][40][41][42][43]. Molecular hardness can be understood as a resistance to change the equilibrium electronic distribution [36,[39][40][41][42][43].…”

“…Molecular hardness can be understood as a resistance to change the equilibrium electronic distribution [36,[39][40][41][42][43]. Through the finite difference approximation and Koopman's [44] theorem working formulae for μ and η in terms of ionization potential (IP) and electron affinity (EA) [36,45], energies of the frontier molecular orbitals (FMOs) HOMO and LUMO (ε H and ε L ) are obtained:…”

The mechanism of double proton transfer in dimers of uracil and 2‐thiouracil—The reaction force perspective

“…In the product region (n 2 n n P ) the system relaxes and the driving force begins to diminish becoming zero at n P . 14,15 The main consequence of partitioning the reaction coordinate in reaction regions is that it provides a rational partition of the activation energy 8,12,[15][16][17][18] :…”

“…(8). To determine numerically the chemical potential along the reaction coordinate, the finite difference approximation and the Koopmans theorem are used to obtain the following approximate expressions for l [23][24][25] :…”

“…The existence of these molecules in many tautomeric forms has been revealed to be crucial to explain the mutation occurring during DNA duplication. 6 These tautomeric structures can be obtained through intramolecular hydrogen transfer in the monomeric structure [6][7][8] or by intermolecular hydrogen transfer in the dimer system formation. 9 Recently it has been shown that the intramolecular tautomerization of the monomeric structures of 2,4-diketo and 2-thio,4-keto uracil present quite high energy barriers of about 40 kcal/mol, so we explore in this article the way to obtain the enol or thiol tautomers from the intermolecular proton transfer reactions of dimeric structures of uracil and 2-thiouracil.…”