α-methylation and α-fluorination electronic effect on the regioselectivity of carbonyl groups of uracil by H and triel bonds in the interaction of U, T and 5FU with HCl and TrH3 (Tr = B, Al)

Publication date: Available online 10 February 2019Source: Journal of Molecular Graphics and ModellingAuthor(s): Aristote Matondo, Renjith Thomas, Philippe Vuka Tsalu, Christian Tshikala Mukeba, Virima MudogoAbstractQuantum chemical calculations at the ωB97XD/6–311++G(d,p) level of theory have been executed to investigate the effect of substituents via hydrogen-bonded and triel-bonded complexes between uracil (U), thymine (T) and 5-fluorouracil (5FU) with HCl for the former complexes, and with BH3 and AlH3 for the latter complexes. These calculations are supported by single-point energy calculations at MP2/6–311++G(d,p) and CCSD/6-31 + G(d,p) levels of theory, Natural Bond Orbital (NBO) and Molecular Electrostatic Potentials (MEPs) analyses, and global/local reactivity descriptors. The results reveal that triel-bonded complexes are strongly bounded than hydrogen-bonded ones, and Al-containing dimers stronger than B-containing ones. In addition, as the central triel atom grows in size, B-containing dimers (B–O triel bond) are accompanied by weak B–H⋯O unconventional H-bonds. According to local reactivity descriptors, the B–O triel bond is hard-hard interaction that indicates that the association is primarily charge controlled, while the Al–O triel bond is soft-soft interaction that is primarily orbital controlled. In both Hydrogen-as well as triel-bonded complexes, the α-methylation slightly overestimates the binding strength of U, while the α-fluorination e...
Source: Journal of Molecular Graphics and Modelling - Category: Molecular Biology Source Type: research