Fluorescence emission and enhanced photochemical stability of ZnII-5-triethyl ammonium methyl salicylidene ortho-phenylendiiminate interacting with native DNA

A Theoretical and Experimental Investigation of the Spectroscopic Properties of a DNA‐Intercalator Salphen‐Type ZnII Complex

“…where D and PD denote the free and bound ZnL 2 + complex respectively, and P indicates a free site on the DNA polymer. In agreement with previous findings, [10] the ZnL 2 + /DNA solutions are stable to light.…”

“…The zinc(II) complex was synthesized by a recently reported procedure, [10,15,16] by mixing 5-(triethylammoniummethyl) salicylaldehyde chloride, 1,2 phenylendiamine, and zinc(II) perchlorate in a 2:1.1:1 molar ratio. A basic solution (NaOH) of salicylaldehyde in EtOH/H 2 O was added dropwise to a previously prepared ethanolic solution of the diamine and the metal perchlorate.…”

“…Recent studies indicate that exposure to a tungsten lamp causes oxidation of ZnL 2 + in aqueous solution, whereas this process is inhibited when the metal complex is intercalated in DNA. [10,17] To clarify such behavior, we performed a QM/PCM study considering the mono-oxidized (ZnL 3 + , doublet) and dioxidized (ZnL 4 + , singlet and triplet) forms of ZnL 2 + (see Table S2 of the Supporting Information for a list of the main geometrical parameters). The calculations showed that the oxidation is mainly located on the aromatic rings of the ligand ( Figure S5 of the Supporting Information).…”

“…[8] Several studies on other salen-type metal complexes have been also reported in the literature, [9] including their interaction with DNA. [7,[10][11][12] The interest in DNA binding by transition metal complexes is due to the potential discovery of novel metallodrugs. [13] For example, it is well known that DNA is the target of the most common clinically used platinumbased drugs.…”

“…Biancardi cence intensity when its aqueous solutions are exposed to the visible light from a tungsten source; interestingly, this is inhibited when the complex is intercalated into native calf thymus (ct) DNA. [10] By studying frozen solutions of a Zn II salphen complex in organic solvents at 77 K, Germain et al [17] first recognized that 5 min exposure to visible light causes a photoinduced oxidation process giving rise to an EPR signal corresponding to the formation of an S = 1 = 2 radical. The effect of light on complexes of d-block metals and the subsequent effects on biomolecules like DNA is well-documented, for instance, as concerns photodynamic therapy.…”