A DFT Computational and Synthetic Study of New Curcuminoidpropargyl Adducts with Pseudo-Cofacial Aryl Rings

With the aim to utilize transannular pi-pi interactions as a driving force to assemble cofacial pi-decks, a DFT computational study was performed on the adducts resulting from coupling of curcuminoids (CURs), bearing electron-withdrawing groups (F, CF3, SCF3, OCF3) in the aryl rings, with 1,3-diphenylpropargyl moiety and its p-OMe-substituted derivatives. Detailed analysis of the structural and electronic properties of the resulting assemblies revealed the existence of intermolecular aromatic pi-pi stacking interactions between one pair, and in some cases two pairs, of aryl rings. Structural/ electronic changes resulting from pi-complexation to Ag+ (mono and bis adducts), and to Cr(CO)(3) acting as pi-electron sink, were also examined. Motivated by the DFT computations outcomes, the feasibility to access these adducts via a simple one-pot reaction using bismuth nitrate as catalyst was shown in representative cases, along with complexation to AgOTf via an NMR study.