A comparative DFT study on the π-π stacking interaction of some N-based organic fused heterocycles with eclipsed and staggered conformations

As most of the antimicrobial, anticancer, antibacterial or antiviral agents are made of nitrogen(N)-based organic fused heterocyclic system; therefore, the study of such system has a great impact on pharmacology and medicinal chemistry research. Quantum mechanical study on the non-covalent or π-π stacking interaction of any organic system always plays a significant role to analyze the proper conformation of such stacked models. It has been observed that some bioactive N-based fused heterocycles; viz. quinoline, isoquinoline, cinnoline, quinazoline, phthalazine, quinoxaline and petridine; shows favored stacked homo dimer and results in effective π-π stacking interaction that occurs within themselves. Usually, non-covalent interaction follows intercalation mechanism via π-stacking which results in very strong interaction within heterocyclic systems. Herein, some of the stacked dimers of N-based fused heterocyclic systems have been investigated using DFT method, as it is the most accurate and appropriate tool for the prediction of molecular interaction. We also carried out the stacking interaction of such system with different molecular conformations i.e., eclipsed and staggered models. In our investigation, it has revealed that for most of the N-based stacked heterocyles, staggered conformation (with intermolecular rotation 120° and 180°) shows favored stacked conformation than that of eclipsed conformation (with intermolecular rotation 0°).