Nature of the Te⋯N intramolecular interaction in organotellurium compounds. A theoretical investigation by NBO and AIM methods

The nature and the strength of intramolecular Te⋯N interactions in three series of o-substituted organotellurium compounds [2-(di-methyl)C6H4TeX (1a–f), 2-(oxa)C6H4TeX (2a–f), 2-(py)C6H4TeX (3a–f); X = Cl, Br, Me, CN, SPh and TePh; Me: Methyl, Ph: Phenyl] have been studied using density functional theory. The effect of substituents (X) and different nitrogen donors are predicted using B3LYP/LanL2DZ method. The Natural Bond Orbital (NBO) analysis demonstrated that the n N → σ TeX ∗ electron delocalization is the key contributing factor for Te⋯N non-bonding interactions. The NBO second-order perturbation energy ETe⋯N (as well as NBO deletion energy Edel) correlates with Te⋯N distance on a single curve irrespective of the donor nitrogen atom. The values of ETe⋯N (as well as Edel) approximately follow the trend Br > Cl > TePh > SPh > CN > Me for a given nitrogen donor, and 3 > 2 > 1 for a given X. Both NBO and Atoms-in-Molecule (AIM) methods suggest that the Te⋯N interactions in these compounds have a dominant covalent character. Studies on the effect of solvent on the Te⋯N interaction show that polar solvent stabilizes the Te⋯N interactions by shortening the Te⋯N atomic distance. Comparison with the corresponding Se counterpart shows that the strength of Te⋯N interactions is stronger than those of Se⋯N interactions.