Theoretical Study of the Double Proton Transfer in the CHX−XH···CHX−XH (X = O, S) Complexes

Abstract

A theoretical study of double-proton-transfer processes in bimolecular complexes formed by combinations of molecules of the type CHX−XH (X = O, S) is reported. The reactions are rationalized in terms of the energy, chemical potential, and hardness of hydrogen-bonded and isolated species. Sanderson's rule to determine molecular chemical potential and hardness from the values of the constituent fragments is used to characterize the relaxation effects due to hydrogen bonding. In ten formation and seven double-proton transfer processes studied here, the principles of maximum hardness and minimum polarizability are verified. The mechanism for double proton transfer has been analyzed through the force acting on the system to bring reactants into products and the corresponding energy barriers have been qualitatively classified according to its through bond or through space nature.

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:…”

Caracterización de la reactividad intrínseca de los halobencenos en el modelo conceptual de la teoría de funcionales de la densidad (TFD)

“…Esta herramienta ha sido usada para probar varios sistemas moleculares. [5][6][7][8] El estudio teórico en el modelo de la Teoría de Funcionales de la Densidad, puede ayudar como una guía en la reactividad de los halobencenos. La Teoría de Funcionales de la Densidad es un modelo conceptual para relacionar los cálculos con conceptos tales como potencial químico electrónico (μ), 9-12 dureza química (η) 9-13 y electrofilicidad (ω), 14 conceptos que nos ayudan a entender el comportamiento electrónico de los sistemas.…”

Are the maximum hardness and minimum polarizability principles always obeyed in nontotally symmetric vibrations?

“…Both principles have been applied successfully to the study of molecular vibrations, 9,15-18 internal rotations, 6͑b͒,19 excited states, 20,21 aromaticity, 22 and different types of chemical reactions. 12,[23][24][25][26][27][28][29][30][31][32][33] It has been found in most of these cases that the conditions of maximum hardness and minimum polarizability complement the minimum energy criterion for molecular stability.…”

“…However, relaxation of these constraints seems to be permissible, and in particular, it has been found that in most cases the MHP still holds even though the chemical and external potentials vary during the molecular vibration, internal rotation or along the reaction coordinate. 12,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] Hereafter, we will refer to the generalized MHP ͑GMHP͒ or MPP ͑GMPP͒ as the maximum hardness or minimum polarizability principles that do not require the constancy of chemical and external potentials during molecular change. It is worth emphasizing that the generalized versions of these principles have not been proven.…”