Four (mu-oxo)diiron(iii) complexes [Fe(2)(mu-O)(H(2)O)(2)B(4)](ClO(4))(4) ( and ) and [Fe(2)(mu-O... more Four (mu-oxo)diiron(iii) complexes [Fe(2)(mu-O)(H(2)O)(2)B(4)](ClO(4))(4) ( and ) and [Fe(2)(mu-O)(mu-O(2)CMe)B(4)](ClO(4))(3) ( and ), where B = 1,10-phenanthroline (phen) and dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), are prepared and their DNA binding and cleavage activity studied. The complexes show DNA binding propensity giving K(b) values of 3.6-9.3 x 10(4) M(-1). The viscosity and DNA melting data suggest a surface and/or groove binding nature of the complexes to calf thymus (CT) DNA. The DNA binding data obtained from isothermal calorimetric study indicate two binding modes involving surface aggregation and/or partial intercalation of the phenanthroline bases to CT DNA. All the complexes show chemical nuclease activity in the presence of 3-mercaptopropionic acid as a reducing agent following a mechanistic pathway that involves formation of superoxide and hydroxyl radicals. Photoirradiation of pUC19 DNA at 365 nm in the presence of 1-4 show that the complexes, barring 1 , are efficient photocleavers of supercoiled DNA to its nicked circular form. Complexes 2-4 display photocleavage activity in visible light of different wavelengths. Complexes 3 and 4 exhibit significant DNA cleavage activity in red light of 633 nm, the wavelength known for the activity of the photodynamic therapeutic drug Photofrin. The mechanistic study using various additives suggests a minor groove binding nature of the complexes with the formation of singlet oxygen from the quinoxaline moiety of dpq and hydroxyl radical from photodecarboxylation of the acetate ligand as the reactive oxygen species.
Ferrocene-conjugated ternary copper (II) complexes having phenanthroline bases show DNA, protein ... more Ferrocene-conjugated ternary copper (II) complexes having phenanthroline bases show DNA, protein binding, and photoinduced DNA cleavage activity. The dipyridophenazine complex shows DNA and protein photocleavage in red and UV-A light, respectively.
Four new ternary copper (II) complexes of α-amino acid having polypyridyl bases of general formul... more Four new ternary copper (II) complexes of α-amino acid having polypyridyl bases of general formulation [Cu (l-ala)(B)(H2O)](X)(1–4), where l-ala is l-alanine, B is an N, N-donor heterocyclic base, viz. 2, 2′-bipyridine (bpy, 1), 1, 10-phenanthroline (phen, 2) and 5, 6-...
Ferrocene-conjugated L-tryptophan (L-Trp) reduced Schiff base (Fc-TrpH) copper(II) complexes [Cu(... more Ferrocene-conjugated L-tryptophan (L-Trp) reduced Schiff base (Fc-TrpH) copper(II) complexes [Cu(Fc-Trp)(L)](ClO(4)) of phenanthroline bases (L), viz. 2,2'-bipyridine (bpy in 1), 1,10-phenanthroline (phen in 2), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 3), and dipyrido[3,2-a:2',3'-c]phenazine (dppz in 4), were prepared and characterized and their photocytotoxicity studied. Cationic reduced Schiff base (Ph-TrpH) complexes [Cu(Ph-Trp)(L)(H(2)O)](ClO(4)) (L = phen in 5; dppz in 6) having the ferrocenyl moiety replaced by a phenyl group and the Zn(II) analogue (7) of complex 4 were prepared and used as control species. The crystal structures of 1 and 5 with respective square-planar CuN(3)O and square-pyramidal CuN(3)O(2) coordination geometry show significantly different core structures. Complexes 1-4 exhibit a Cu(II)-Cu(I) redox couple near -0.1 V and the Fc(+)-Fc couple at ~0.5 V vs SCE in DMF-0.1 M [Bu(n)(4)N](ClO(4)) (Fc = ferrocenyl moiety). The complexes display a copper(II)-based d-d band near 600 nm and a Fc-centered band at ~450 nm in DMF-Tris-HCl buffer. The complexes are efficient binders to calf thymus DNA. They are synthetic chemical nucleases in the presence of thiol or H(2)O(2), forming hydroxyl radicals. The photoactive complexes are cleavers of pUC19 DNA in visible light, forming hydroxyl radicals. Complexes 2-6 show photocytotoxicity in HeLa cancer cells, giving IC(50) values of 4.7, 10.2, 1.3, 4.8, and 4.3 μM, respectively, in visible light with the appearance of apoptotic bodies. The complexes also show photocytotoxicity in MCF-7 cancer cells. Nuclear chromatin cleavage has been observed with acridine orange/ethidium bromide (AO/EB) dual staining with complex 4 in visible light. The complexes induce caspase-independent apoptosis in the HeLa cells.
Iron(III) complexes [FeL(B)] (1-5) of a tetradentate trianionic phenolate-based ligand (L) and mo... more Iron(III) complexes [FeL(B)] (1-5) of a tetradentate trianionic phenolate-based ligand (L) and modified dipyridophenazine bases (B), namely, dipyrido-6,7,8,9-tetrahydrophenazine (dpqC in 1), dipyrido[3,2-a:2',3'-c]phenazine-2-carboxylic acid (dppzc in 2), dipyrido[3,2-a:2',3'-c]phenazine-11-sulfonic acid (dppzs in 3), 7-aminodipyrido[3,2-a:2',3'-c]phenazine (dppza in 4) and benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (dppn in 5), have been synthesized and their photocytotoxic properties studied along with their dipyridophenazine analogue (6). The complexes have a five electron paramagnetic iron(III) center, and the Fe(III)/Fe(II) redox couple appears at about -0.69 V versus SCE in DMF-0.1 M TBAP. The physicochemical data also suggest that the complexes possess similar structural features as that of its parent complex [FeL(dppz)] with FeO3N3 coordination in a distorted octahedral geometry. The DNA-complex and protein-complex interaction studies have revealed that the complexes interact favorably with the biomolecules, the degree of which depends on the nature of the substituents present on the dipyridophenazine ring. Photocleavage of pUC19 DNA by the complexes has been studied using visible light of 476, 530, and 647 nm wavelengths. Mechanistic investigations with inhibitors show formation of HO(•) radicals via a photoredox pathway. Photocytotoxicity study of the complexes in HeLa cells has shown that the dppn complex (5) is highly active in causing cell death in visible light with sub micromolar IC(50) value. The effect of substitutions and the planarity of the phenazine moiety on the cellular uptake are quantified by determining the total cellular iron content using the inductively coupled plasma-optical emission spectrometry (ICP-OES) technique. The cellular uptake increases marginally with an increase in the hydrophobicity of the dipyridophenazine ligands whereas complex 3 with dppzs shows very high uptake. Insights into the cell death mechanism by the dppn complex 5, obtained through DAPI nuclear staining in HeLa cells, reveal a rapid programmed cell death mechanism following photoactivation of complex 5 with visible light. The effect of substituent on the DNA photocleavage activity of the complexes has been rationalized from the theoretical studies.
A new ternary iron(III) complex [FeL(dpq)] containing dipyridoquinoxaline (dpq) and 2,2-bis(3,5-d... more A new ternary iron(III) complex [FeL(dpq)] containing dipyridoquinoxaline (dpq) and 2,2-bis(3,5-di-tert-butyl-2-hydroxybenzyl)aminoacetic acid (H3L) is prepared and structurally characterized by X-ray crystallography. The high-spin complex with a FeN3O3 core shows a quasi-reversible iron(III)/iron(II) redox couple at -0.62 V (vs SCE) in DMF/0.1 M TBAP and a broad visible band at 470 nm in DMF/Tris buffer. Laser photoexcitation of this phenolate (L)-to-iron(III) charge-transfer band at visible wavelengths including red light of >or=630 nm leads to cleavage of supercoiled pUC19 DNA to its nicked circular form via a photoredox pathway forming hydroxyl radicals.
Four (mu-oxo)diiron(iii) complexes [Fe(2)(mu-O)(H(2)O)(2)B(4)](ClO(4))(4) ( and ) and [Fe(2)(mu-O... more Four (mu-oxo)diiron(iii) complexes [Fe(2)(mu-O)(H(2)O)(2)B(4)](ClO(4))(4) ( and ) and [Fe(2)(mu-O)(mu-O(2)CMe)B(4)](ClO(4))(3) ( and ), where B = 1,10-phenanthroline (phen) and dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), are prepared and their DNA binding and cleavage activity studied. The complexes show DNA binding propensity giving K(b) values of 3.6-9.3 x 10(4) M(-1). The viscosity and DNA melting data suggest a surface and/or groove binding nature of the complexes to calf thymus (CT) DNA. The DNA binding data obtained from isothermal calorimetric study indicate two binding modes involving surface aggregation and/or partial intercalation of the phenanthroline bases to CT DNA. All the complexes show chemical nuclease activity in the presence of 3-mercaptopropionic acid as a reducing agent following a mechanistic pathway that involves formation of superoxide and hydroxyl radicals. Photoirradiation of pUC19 DNA at 365 nm in the presence of 1-4 show that the complexes, barring 1 , are efficient photocleavers of supercoiled DNA to its nicked circular form. Complexes 2-4 display photocleavage activity in visible light of different wavelengths. Complexes 3 and 4 exhibit significant DNA cleavage activity in red light of 633 nm, the wavelength known for the activity of the photodynamic therapeutic drug Photofrin. The mechanistic study using various additives suggests a minor groove binding nature of the complexes with the formation of singlet oxygen from the quinoxaline moiety of dpq and hydroxyl radical from photodecarboxylation of the acetate ligand as the reactive oxygen species.
Ferrocene-conjugated ternary copper (II) complexes having phenanthroline bases show DNA, protein ... more Ferrocene-conjugated ternary copper (II) complexes having phenanthroline bases show DNA, protein binding, and photoinduced DNA cleavage activity. The dipyridophenazine complex shows DNA and protein photocleavage in red and UV-A light, respectively.
Four new ternary copper (II) complexes of α-amino acid having polypyridyl bases of general formul... more Four new ternary copper (II) complexes of α-amino acid having polypyridyl bases of general formulation [Cu (l-ala)(B)(H2O)](X)(1–4), where l-ala is l-alanine, B is an N, N-donor heterocyclic base, viz. 2, 2′-bipyridine (bpy, 1), 1, 10-phenanthroline (phen, 2) and 5, 6-...
Ferrocene-conjugated L-tryptophan (L-Trp) reduced Schiff base (Fc-TrpH) copper(II) complexes [Cu(... more Ferrocene-conjugated L-tryptophan (L-Trp) reduced Schiff base (Fc-TrpH) copper(II) complexes [Cu(Fc-Trp)(L)](ClO(4)) of phenanthroline bases (L), viz. 2,2'-bipyridine (bpy in 1), 1,10-phenanthroline (phen in 2), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 3), and dipyrido[3,2-a:2',3'-c]phenazine (dppz in 4), were prepared and characterized and their photocytotoxicity studied. Cationic reduced Schiff base (Ph-TrpH) complexes [Cu(Ph-Trp)(L)(H(2)O)](ClO(4)) (L = phen in 5; dppz in 6) having the ferrocenyl moiety replaced by a phenyl group and the Zn(II) analogue (7) of complex 4 were prepared and used as control species. The crystal structures of 1 and 5 with respective square-planar CuN(3)O and square-pyramidal CuN(3)O(2) coordination geometry show significantly different core structures. Complexes 1-4 exhibit a Cu(II)-Cu(I) redox couple near -0.1 V and the Fc(+)-Fc couple at ~0.5 V vs SCE in DMF-0.1 M [Bu(n)(4)N](ClO(4)) (Fc = ferrocenyl moiety). The complexes display a copper(II)-based d-d band near 600 nm and a Fc-centered band at ~450 nm in DMF-Tris-HCl buffer. The complexes are efficient binders to calf thymus DNA. They are synthetic chemical nucleases in the presence of thiol or H(2)O(2), forming hydroxyl radicals. The photoactive complexes are cleavers of pUC19 DNA in visible light, forming hydroxyl radicals. Complexes 2-6 show photocytotoxicity in HeLa cancer cells, giving IC(50) values of 4.7, 10.2, 1.3, 4.8, and 4.3 μM, respectively, in visible light with the appearance of apoptotic bodies. The complexes also show photocytotoxicity in MCF-7 cancer cells. Nuclear chromatin cleavage has been observed with acridine orange/ethidium bromide (AO/EB) dual staining with complex 4 in visible light. The complexes induce caspase-independent apoptosis in the HeLa cells.
Iron(III) complexes [FeL(B)] (1-5) of a tetradentate trianionic phenolate-based ligand (L) and mo... more Iron(III) complexes [FeL(B)] (1-5) of a tetradentate trianionic phenolate-based ligand (L) and modified dipyridophenazine bases (B), namely, dipyrido-6,7,8,9-tetrahydrophenazine (dpqC in 1), dipyrido[3,2-a:2',3'-c]phenazine-2-carboxylic acid (dppzc in 2), dipyrido[3,2-a:2',3'-c]phenazine-11-sulfonic acid (dppzs in 3), 7-aminodipyrido[3,2-a:2',3'-c]phenazine (dppza in 4) and benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (dppn in 5), have been synthesized and their photocytotoxic properties studied along with their dipyridophenazine analogue (6). The complexes have a five electron paramagnetic iron(III) center, and the Fe(III)/Fe(II) redox couple appears at about -0.69 V versus SCE in DMF-0.1 M TBAP. The physicochemical data also suggest that the complexes possess similar structural features as that of its parent complex [FeL(dppz)] with FeO3N3 coordination in a distorted octahedral geometry. The DNA-complex and protein-complex interaction studies have revealed that the complexes interact favorably with the biomolecules, the degree of which depends on the nature of the substituents present on the dipyridophenazine ring. Photocleavage of pUC19 DNA by the complexes has been studied using visible light of 476, 530, and 647 nm wavelengths. Mechanistic investigations with inhibitors show formation of HO(•) radicals via a photoredox pathway. Photocytotoxicity study of the complexes in HeLa cells has shown that the dppn complex (5) is highly active in causing cell death in visible light with sub micromolar IC(50) value. The effect of substitutions and the planarity of the phenazine moiety on the cellular uptake are quantified by determining the total cellular iron content using the inductively coupled plasma-optical emission spectrometry (ICP-OES) technique. The cellular uptake increases marginally with an increase in the hydrophobicity of the dipyridophenazine ligands whereas complex 3 with dppzs shows very high uptake. Insights into the cell death mechanism by the dppn complex 5, obtained through DAPI nuclear staining in HeLa cells, reveal a rapid programmed cell death mechanism following photoactivation of complex 5 with visible light. The effect of substituent on the DNA photocleavage activity of the complexes has been rationalized from the theoretical studies.
A new ternary iron(III) complex [FeL(dpq)] containing dipyridoquinoxaline (dpq) and 2,2-bis(3,5-d... more A new ternary iron(III) complex [FeL(dpq)] containing dipyridoquinoxaline (dpq) and 2,2-bis(3,5-di-tert-butyl-2-hydroxybenzyl)aminoacetic acid (H3L) is prepared and structurally characterized by X-ray crystallography. The high-spin complex with a FeN3O3 core shows a quasi-reversible iron(III)/iron(II) redox couple at -0.62 V (vs SCE) in DMF/0.1 M TBAP and a broad visible band at 470 nm in DMF/Tris buffer. Laser photoexcitation of this phenolate (L)-to-iron(III) charge-transfer band at visible wavelengths including red light of >or=630 nm leads to cleavage of supercoiled pUC19 DNA to its nicked circular form via a photoredox pathway forming hydroxyl radicals.
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