Bis(2,2′-bipyridine)cobalt(III) complexes containing asymmetric ligands: Synthesis, DNA-binding and photocleavage studies

Abstract

Three new Co III complexes: [Co(bpy) 2 (pdtb)] 3+ (1), [Co(bpy) 2 (pdta)] 3+ (2) and [Co(bpy) 2 (pdtp)] 3+ (3) have been synthesized and characterized. The DNA binding behavior of the Co III complexes has been investigated by spectroscopic methods and viscosity measurements. The results indicate that the size and shape of the intercalated ligand have a marked effect on the binding affinity of complexes involving CT-DNA. Complexes (2) and (3) have been found to promote cleavage of plasmid pBR 322 DNA from the supercoiled form I to the open circular form II upon irradiation. Photocleavage mechanisms are proposed.

Synthesis, spectral, X-ray diffraction, antimicrobial studies, and DNA binding properties of binary and ternary complexes of pentadentate N2O3 carbohydrazone ligands

“…Electronic absorption spectroscopy has been widely employed to determine the binding ability of metal complexes with DNA [87][88][89][90]. The binding ability of the synthesized oxovanadium(IV) complexes [(L 1 )VO]Á 4H 2 O (1) and [(L 2 )VO]Á 3H 2 O (9) with HS-DNA was investigated by measuring the spectral changes of their electronic spectra during the interaction with DNA.…”

“…To compare quantitatively the affinity of the two complexes toward DNA, the binding constants K b of the two complexes to HS-DNA were determined by monitoring the changes of absorbance at 221 nm for the complexes, with increasing concentration of DNA. The appreciable decrease in absorption intensity and red shift of the k max band suggest that the complexes bind to DNA strongly [87][88][89][90]95]. From the absorption titration data, the binding constant (K b ) was determined using the following equation [96]: [97,98] and revealed that complex 9 shows a stronger binding ability toward DNA which may be due to the presence of an appending aromatic moiety in H 2 L 2 ligand and thus the larger binding affinity of the corresponding complex 9 in comparison with complex 1 incorporating H 2 L 1 ligand [35,[99][100][101].…”

Synthesis, DNA-binding and photocleavage studies of cobalt(III) complexes [Co(bpy)2(dpta)]3+ and [Co(bpy)2(amtp)]3+

“…Even at the concentration of 120 lM, it can promote only 60% conversion of DNA from form I to II. The different DNA-cleavage efficiency of the two complexes may be considered due to the different binding affinity of the complexes to DNA [14][15][16][17]. In order to establish the reactive species responsible for the photoactivated cleavage of the plasmid DNA, the following experiments were carried out.…”

“…Varying the substitutive group or substituent position in the intercalative ligand can create some interesting differences in the space configuration and the electron density distribution of transition metal complexes, which will result in some differences in spectral properties and the DNA-binding behavior of the complexes, and will be helpful to more clearly understand the binding mechanism of transition metal complexes to DNA [6][7][8]. However, such studies mainly focus on the interaction of Ru II complexes with DNA, and the reports on the other metal complexes are relatively limited [9][10][11][12][13][14][15][16][17]. In fact, some of the Co III complexes also exhibit interesting properties upon binding to DNA [14][15][16][17].…”

“…However, such studies mainly focus on the interaction of Ru II complexes with DNA, and the reports on the other metal complexes are relatively limited [9][10][11][12][13][14][15][16][17]. In fact, some of the Co III complexes also exhibit interesting properties upon binding to DNA [14][15][16][17]. In order to more clearly evaluate and understand the factors on the DNA binding and cleavage mechanism, two novel cobalt(III) mixedpolypyridyl complexes with functionalized ligands, [Co(bpy) 2 dpta] 3+ and [Co(bpy) 2 amtp] 3+ (bpy = 2,2¢-bipyridine, dpta = dipyrido-[3,2-a;2¢,3¢-c]-thien- [3,4-c]azine, amtp = 3-amino-1,2,4-triazino[5,6-f]-1,10-phenanthroline), were synthesized and characterizated (Scheme 1).…”