DNA–lipid complexes carrying carbazole and triphenylamine moieties: Synthesis, and chiroptical and photoelectronic properties

Novel DNA–lipid complexes carrying carbazole and triphenylamine moieties were prepared by substituting the sodium counter cation with cationic amphiphilic lipids, namely lipid(Cz) and lipid(TPA), in which the actual mole ratios of phosphate to lipid were 1:1.10 and 1:0.83, respectively. The DNA–lipid(Cz) and DNA–lipid(TPA) complexes were soluble in common organic solvents including CHCl3, CH2Cl2, methanol and ethanol, while insoluble in THF, toluene, and aqueous solutions. CD spectroscopy revealed that the DNA–lipid complexes took a predominantly double helical structure in CHCl3 and methanol and that the helical structure was fairly stable against heating. Solutions of DNA–lipid(Cz) and DNA–lipid(TPA) complexes emitted fluorescence in 5.7 and 76.4% quantum yields, which were higher than those of the corresponding lipid(Cz) and lipid(TPA) (4.4 and 55.3%). The cyclic voltammograms of the complexes indicated that the oxidation potentials of DNA–lipid(Cz) and DNA–lipid(TPA) were 0.95 and 0.85 V, respectively. The onset temperatures of weight loss of the DNA–lipid complexes were both 220 °C according to TGA in air.