Unveiling the Noncovalent Interaction of Thiazol-2-ylidene and Its Derivatives as N-heterocyclic Carbene with Different Proton Donor Molecules.

Abstract

The importance of noncovalent interaction has gained attention in various domains covering drug and novel catalyst design. The present study mainly characterizes the role of hydrogen bond (H-bond) and other intermolecular interactions in different (1 : 1) complex analogues formed between the N-aryl-thiazol-2-ylidene (YR) and five proton donor (HX) molecules. The analysis of the singlet-triplet energy gap ( ) confirmed the stability of the singlet state for this class of N-aryl-thiazol-2-ylidenes than the triplet state. The interaction energy values of the YR-HX complexes follow the order: YR-NH3 <YR-HCN<YR-H2 O<YR-MeOH<YR-HF. In addition, substituting the H-atom of the N-H bond with bulky groups (-R) leads to an increase in the interaction energy of the YR-HX complexes. Hence, it was found that the replacement of N-atom in N-heterocyclic carbene (NHC) by S-atom forming N-aryl-thiazol-2-ylidene results in comparable intermolecular interactions with proton donor molecules similar to imidazole-2-ylidene (NHC). The current study enlightened the role of noncovalent interactions in carbene complexes with proton donor molecules. We hope that our work on carbene chemistry will pave the way for its application in the designing and synthesis of efficient catalysts.