Charge transfer and electron transfer processes in biologically significant systems. 1. Charge transfer complex formation between 1,3,5-trinitrobenzene and N,N-dimethyl-3,4-di-O-methyldopamine, a dopamine analogue

The interactions of N,N-dimethyl-3,4-di-O-methyldopamine, 1, a structural analogue of the important neurochemical, dopamine, with 1,3,5-trinitrobenzene (TNB) were studied primarily by 1H nuclear magnetic resonance (nmr). The dopamine analogue, a donor, forms a charge transfer complex with TNB, a model acceptor, in CDCl3 and CD3CN. Equilibrium constants were determined from the 1H nmr charge transfer induced chemical shift changes. The results are discussed in terms of the probable type of donation from the amine, 1, to TNB (n → π* versus π → π*), comparison with dopamine, and with regard to possible charge transfer interactions in molecular receptors. Keywords: N,N-dimethyl-3,4-di-O-methyldopamine, charge transfer complex, equilibrium constant.