Why naturally occurring quinone redox systems lack amino groups: consideration using 1,4-naphthoquinone derivatives

Four representatives of amino derivatives of 1,4-naphtho-quinone were examined by combination of cyclic voltammetry, ESR spectroscopy and quantum chemical calculations. The results obtained help to rationalize why natural quinonoid redox systems do not contain amino groups so common in proteins, nucleobases, numerous signal and other biologically important molecules.