Photolysis and thermolysis of platinum(IV) 2,2'-bipyridine complexes lead to identical platinum(II)-DNA adducts.

Two Pt(IV) and two Pt(II) complexes containing a 2,2'-bipyridine ligand were treated with a short DNA oligonucleotide under light irradiation at 37°C or in the dark at 37 and 50°C. Photolysis and thermolysis of the Pt(IV) complexes led to spontaneous reduction of the Pt(IV) to the corresponding Pt(II) complexes and to binding of Pt(II) 2,2'-bipyridine complexes to N7 of guanine. When the reduction product was [Pt(bpy)Cl(2)], formation of bis-oligonucleotide adducts was observed, whereas [Pt(bpy)(MeNH(2))Cl](+) gave monoadducts, with chloride ligands substituted in both cases. Neither in the dark nor under light irradiation was the reductive elimination process of these Pt(IV) complexes accompanied by oxidative DNA damage. This work raises the question of the stability of photoactivatable Pt(IV) complexes toward moderate heating conditions.

Crystal structures and Hirshfeld surface analyses of two new tetra-kis-substituted pyrazines and a degredation product.

The two new tetra-kis-substituted pyrazines, 1,1',1'',1'''-(pyrazine-2,3,5,6-tetra-yl) tetra-kis-(N,N-di-methyl-methanamine), C16H32N6, (I) and N,N',N'',N'''-[pyrazine-2,3,5,6-tetra-yltetra-kis-(methyl-ene)]tetra-kis-(N-methyl-aniline), C36H40N6, (II), both crystallize with half a mol-ecule in the asymmetric unit; the whole mol-ecules are generated by inversion symmetry. There are weak intra-molecular C-H⋯N hydrogen bonds present in both mol-ecules and in (II) the pendant N-methyl-aniline rings are linked by a C-H⋯π inter-action. The degredation product, N,N'-[(6-phenyl-6,7-di-hydro-5H-pyrrolo-[3,4-b]pyrazine-2,3-di-yl)bis(methyl-ene)]bis-(N-methyl-aniline), C28H29N5, (III), was obtained several times by reacting (II) with different metal salts. Here, the 6-phenyl ring is almost coplanar with the planar pyrrolo-[3,4-b]pyrazine unit (r.m.s. deviation = 0.029 Å), with a dihedral angle of 4.41 (10)° between them. The two N-meth-yl-aniline rings are inclined to the planar pyrrolo-[3,4-b]pyrazine unit by 88.26 (10) and 89.71 (10)°, and to each other by 72.56 (13)°. There are also weak intra-molecular C-H⋯N hydrogen bonds present involving the pyrazine ring and the two N-methyl-aniline groups. In the crystal of (I), there are no significant inter-molecular contacts present, while in (II) mol-ecules are linked by a pair of C-H⋯π inter-actions, forming chains along the c-axis direction. In the crystal of (III), mol-ecules are linked by two pairs of C-H⋯π inter-actions, forming inversion dimers, which in turn are linked by offset π-π inter-actions [inter-centroid distance = 3.8492 (19) Å], forming ribbons along the b-axis direction.

The crystal structures and Hirshfeld surface analyses of a cadmium(II) and a zinc(II) mononuclear complex of the new tetrakis-substituted pyrazine ligand N,N',N'',N'''-[pyrazine-2,3,5,6-tetra-yltetra-kis-(methyl-ene)]tetra-kis-(N-methyl-aniline).

The whole mol-ecule of the cadmium(II) complex, di-iodido-{N,N',N'',N'''-[pyrazine-2,3,5,6-tetra-yltetra-kis-(methyl-ene)]tetra-kis-(N-methyl-aniline)-κ3 N 2,N 1,N 6}cadmium(II), [CdI2(C36H40N6)], (I), of the ligand N,N',N'',N'''-[pyrazine-2,3,5,6-tetra-yltetra-kis-(methyl-ene)]tetra-kis-(N-methyl-aniline) (L), is generated by a twofold rotation symmetry; the twofold axis bis-ects the cadmium atom and the nitro-gen atoms of the pyrazine ring. The ligand coordinates in a mono-tridentate manner and the cadmium atom has a fivefold CdN3I2 coordination environment with a distorted shape. In the zinc(II) complex, dichlorido{N,N',N'',N'''-[pyrazine-2,3,5,6-tetra-yltetra-kis-(methyl-ene)]tetra-kis-(N-methyl-aniline)-κ3 N 2,N 1,N 6}zinc(II) di-chloro-methane 0.6-solvate, [ZnCl2(C36H40N6)]·0.6CH2Cl2, (II), ligand L also coordinates in a mono-tridentate manner and the zinc atom has a fivefold ZnN3Cl2 coordination environment with a distorted shape. It crystallized as a partial di-chloro-methane solvate. In the crystal of I, the complex mol-ecules are linked by weak C-H⋯I contacts, forming ribbons propagating along [100]. In the crystal of II, the complex mol-ecules are linked by a series of C-H⋯π inter-actions, forming layers lying parallel to the (11) plane. In the crystals of both compounds there are metal-halide⋯π(pyrazine) contacts present. The Hirshfeld analyses confirm the importance of the C-H⋯halide contacts in the crystal packing of both compounds.

Structure and properties of dinuclear manganese(III) complexes with pentaanionic pentadentate ligands including alkoxo, amido, and phenoxo donors.

Doubly bridged mu-alkoxo-mu-X (X = pyrazolato or acetato) dinuclear MnIII complexes of 2-hydroxy-N-{2-hydroxy-3-[(2-hydroxybenzoyl)amino]propyl}benzamide) (H5L1) and 2-hydroxy-N-{2-hydroxy-4-[(2-hydroxybenzoyl)amino]butyl}benzamide (H5L2), [Mn2(L)(pz)(MeOH)4].xMeOH (1, L = L1, x = 0.5; 2, L = L2, x = 0; Hpz = pyrazole) and [Mn2(L1)(OAc)(MeOH)4] (3), have been prepared, and their structure and magnetic properties have been studied. The X-ray diffraction analysis of 1 (C24.5H34Mn2N4O9.5, triclinic, P, a = 12.2050(7) A, b = 12.7360(8) A, c = 19.2780(10) A, alpha = 99.735(5) degrees , beta = 96.003(4) degrees , gamma = 101.221(5) degrees , V = 2867.6(3) A3, Z = 4), 2 (C25H34Mn2N4O9, triclinic, P, a = 9.4560(5) A, b = 11.0112(5) A, c = 13.8831(6) A, alpha = 90.821(4) degrees , beta = 92.597(4) degrees , gamma = 93.403(4) degrees , V = 1441.29(12) A3, Z = 2), and 3 (C23H32Mn2N2O11, triclinic, P, a = 10.511(5) A, b = 11.713(5) A, c = 13.135(5) A, alpha = 64.401(5) degrees , beta = 74.000(5) degrees , gamma = 66.774(5) degrees , V = 1329.3(10) A3, Z = 2) revealed that all complexes consist of dinuclear units which are further extended into 1D (1 and 3) and 2D (2) supramolecular networks via hydrogen-bonding interactions. Magnetic susceptibility data evidence antiferromagnetic interactions for all three complexes: J = -3.6 cm-1, D approximately 0 cm-1, g = 1.93 (1); J = -2.7 cm-1, D = 0.8 cm-1, g = 1.93 (2); J = -4.9 cm-1, D = 3.8 cm-1, g = 1.95 (3).