Dipyridophenazine Complexes of Cobalt(III): DNA Photocleavage and Photobiology

The UV-visible spectroscopy and photochemistry of [Co(en)2(DPPZ)](ClO4)3 (DPPZ = dipyrido[3,2-a:2´,3´-c]-phenazine) in the presence of plasmid DNA and the nucleoside 2´-deoxygaunosine have been investigated. Evidence for the intercalation of the complex with DNA and photoinduced DNA strand breakage is found. The structurally related complexes [Co(en)2(DPPN)]Cl3 and [Co(en)2(DPPA)]Cl2, where DPPN = benzo[i]dipyrido[3,2-a:2´,3´-c]phenazine and DPPA = dipyrido[3,2-a:2´,3´-c] phenazine-11-carboxylic acid, have also been synthesized and characterized. In vitro cytotoxicity studies and photocytotoxicity studies of the complexes using the C6 rat glioma cell line are reported and indicate significant increases in toxicity following irradation.

The Preparation of a Mixed-Ligand Cobalt(III) Complex of DPPZ and Ethylenediamine: Crystal Structures of [Co(en)2(DPPZ)] (ClO4)3.0·5H2O, [Co(en)2(bpy)]Br(ClO4)2 and [Co(en)2(phen)] Br3

The complex [Co(en)2(DPPZ)] (ClO4)3 (3) has been synthesized, and the crystal structures of this complex and those of [Co(en)2(bpy)] Br(ClO4)2 (1) and [Co(en)2(phen)] Br3 (2) have been determined. Crystal data for (1): M 614 . 13, monoclinic, space group C2/c (No. 15), a 16 . 7834(16), b 16 . 308(3), c 8 . 3167(15) Å, β 104 . 932(11)°, V 2199 . 4(6) Å, F(000) 1240, Z 4, Dc 1 . 855 g cm−3, µ 2 . 895 cm−1 , Mo Kα (graphite monochromatized) radiation, γ 0 . 71073 Å, T 293(1) K. Crystal data for (2): M 599 . 07, triclinic, space group P1 (No. 2), a 7 . 7113(11), b 10 . 633(2), c 12 . 9884(18) Å, α 85 . 745(15), b 78 . 258(11), γ 74 . 967(16)°, V 1006 . 7(3) Å, F(000) 588, Z 2, Dc 1 . 976 g cm−3, µ6 . 819 cm−1 , MoKα (graphite monochromatized) radiation, γ 0 . 71073 Å, T 293(1) K. Crystal data for (3): M 773 . 44, monoclinic, space group P 21/c (No. 14), a 20 . 296(2), b 9 . 6197(11), c 15 . 725(2) Å, β 92 . 850(10)°, V 3066 . 4(6) Å, F(000) 1579, Z 4, Dc 1 . 675 g cm−3 , µ 0 . 898 cm−1 , MoKα(graphite monochromatized) radiation, γ 0 . 71073 Å, T 293(1) K. In all three complexes the cobalt is in the usual octahedral environment, with the cations being linked by hydrogen bonds between the amine hydrogens and the anions into extended structures.