Role of hydrogen bonding interactions within of the conformational preferences of calix[n = 4,6,8]arene: DFT and QTAIM analysis. 
Understanding the interactions of the cage molecules with a variety of invited molecules is getting very important.  But, the hydrogen bonds can also play a crucial role in the interaction phenomenon.  In this work, natural population analysis (NPA), chemical shifts, and atom in molecules (AIM) analysis have been used to identify the role of hydrogen bonds in the stability of CX[n] molecules.  According to our calculation, the 13C NMR spectra are also sensitive to the nature of hydrogen bonds.  We note that the DFT calculations have reproduced with a very good agreement, the experimentally observed chemical shifts of CX[4].