Ferrocenyl hetaryl thioketones: A computational study of their conformational stability

Abstract

AbstractIn this work, the conformational behavior of ferrocenyl‐ and hetaryl‐functionalized thioketones was studied by means of computational quantum chemical methods. Four hetaryl substituents (furan‐2‐yl, thiophen‐2‐yl, selenophen‐2‐yl, and N‐methylpyrrol‐2‐yl) were taken into account. The conformational space of the four ferrocenyl hetaryl thioketones was explored, and all found conformers were characterized using density functional (B3LYP) and wave function (SCS‐MP2) theories. Their stability was explained in terms of intramolecular interactions. Such interactions were described using the methods of natural bond orbitals, “atoms in molecules,” noncovalent interaction index, and localized molecular orbital energy decomposition analysis. The identified conformations essentially differ in the arrangement of hetaryl heteroatom relative to the thiocarbonyl sulfur atom. The furan‐2‐yl substituent favors an s‐trans‐like arrangement of its heteroatom, while the remaining hetaryl substituents tend to adopt an s‐cis‐like arrangement. Such a conformational preference mainly results from the π → π* stabilization between the CS group and the hetaryl ring. Weak intramolecular hydrogen bonding of CH⋯O type was detected in the preferred conformer of ferrocenyl furan‐2‐yl thioketone. Low‐polarity solvents, such as toluene, chloroform, and tetrahydrofuran, have a small effect on the preferred conformers of the four thioketones.