Experimental and Theoretical Studies on the Interaction of Dopamine Hydrochloride with Nicotinic Acid

Cyclic voltammetry (CV), 1H nuclear magnetic resonance (1H NMR), density functional theory (DFT), quantum theory of atoms in molecules (QTAIM) and reduced density gradient (RDG) were used to study the interactions of dopamine hydrochloride (DH) with nicotinic acid (NAC) in aqueous solution. The results revealed that there existed three weak interactions in the DH–NAC system, C–H···π, π···π stacking and hydrogen bonds. These interactions showed different effects on the DH electrooxidation and its chemical environment. Moreover, the CV and 1H NMR results indicated that C–H···π interaction between the H atoms on the benzene ring of DH and the pyridine ring of NAC, and π···π stacking between the benzene ring of DH and the pyridine ring of NAC are the main interactions in the system.