A computational investigation of the interactions between harmane and the functional monomers commonly used in molecular imprinting

In this study, the density functional (DFT) method with the hybrid B3LYP exchange-correlation functional has been applied to investigate the intermolecular interactions between harmane and the selected functional monomers: methacrylic acid (MAA) and 2-hydroxyethyl methacrylate (HEMA), most commonly used in the preparation of molecularly imprinted polymers (MIPs). For this purpose possible conformations of 1:n (n ⩽ 4) harmane/functional monomer systems have been optimized with the use of the DFT(B3LYP)/6-31G(d,p) method. The most stable configurations of harmane/functional monomer 1:n (n ⩽ 4) complexes have been selected. The positions and the geometrical parameters of hydrogen bonding sites in the optimized 1:n harmane/functional monomer systems have been determined. The binding energies ΔEbind of the optimized systems have been calculated taking into account the basis set superposition error (BSSE) and the zero-point vibrational energies (ΔZPVE) corrections. Based on the conformational analysis and the calculated binding energies of harmane/monomer molecular systems, we have concluded that the interactions between harmane and MAA are more specific and stronger in comparison to the interactions between harmane and HEMA.