Scheme 2

Synthesis of the intercalator mixture 4 and 5. (a) Paraformaldehyde, dimethylamine hydrochloride, isopropanol, reflux, 24 h; (b) 4-methylthiophenol, isopropanol/H₂O, RT, 24 h; (c) H₂O₂, AcOH, 30 °C, 24 h; (d) EDC·HCl, HOBt, CH₂Cl₂/N-methylmorpholine, 0 °C, 0.5 h; (e) 4-amino-TEMPO, CH₂Cl₂/N-methylmorpholine, 0 °C, 24 h.