(6,6'-Dimethyl-2,2'-bipyridine-κN,N')diiodidomercury(II).

In the title complex, [HgI(2)(C(12)H(12)N(2))], the Hg(II) atom has a distorted tetra-hedral coordination formed by two N atoms of the 6,6'-dimethyl-2,2'-bipyridine ligand and two terminal I atoms [N-Hg-N = 70.1 (2) and I-Hg-I = 130.59 (3)°]. The crystal packing features π-π contacts between the pyridine rings of adjacent mol-ecules [centroid-centroid distance = 3.773 (5) Å] and also between a pyridine ring of one mol-ecule and the five-membered chelate ring of an adjacent mol-ecule [centroid-centroid distance = 3.668 (4) Å].

DNA Interaction Studies of a New Platinum(II) Complex Containing Different Aromatic Dinitrogen Ligands.

A new mononuclear Pt(II) complex, [Pt(DMP)(DIP)]Cl(2).H(2)O, in which DMP is 4,4-dimethyl-2,2-bipyridine and DIP is 4,7-diphenyl-1,10-phenantroline, has been synthesized and characterized by physicochemical and spectroscopic methods. The binding interaction of this complex with calf thymus DNA (CT-DNA) was investigated using fluorimetry, spectrophotometry, circular dichroism, viscosimetry and cyclic voltametry (CV). UV-VIS spectrum showed 4 nm bathochromic shift of the absorption band at 280 nm along with significant hypochromicity for the absorption band of the complex. The intrnisic binding constant (K(b) = 2 × 10(4) M(-1)) is more in keeping with intercalators and suggests this binding mode. The viscosity measurements showed that the complex-DNA interaction can be hydrophobic and confirm intercalation. Moreover, the complex induced detectable changes in the CD spectrum of CT-DNA. The fluorescence studies revealed that the probable quenching mechanism of fluorescence of the complex by CT-DNA is static quenching. The thermodynamic parameters (ΔH > 0 and ΔS > 0) showed that main interaction with hydrogenic forces occurred that is intercalation mode. Also, CV results confirm this mode because, with increasing the CT-DNA concentration, shift to higher potential was observed.

Dichlorido(6,6'-dimethyl-2,2'-bipyridine-κN,N')cadmium(II).

In the title compound, [CdCl(2)(C(12)H(12)N(2))], the Cd(II) atom is four-coordinated in a distorted tetra-hedral geometry by two N atoms from a 6,6'-dimethyl-2,2'-bipyridine ligand and two terminal Cl atoms. Inter-molecular C-H⋯Cl hydrogen bonds and π-π stacking inter-actions between the pyridyl rings [centroid-centroid distance = 3.7337 (18) Å] are present in the crystal structure.

Dibromido(4,4'-dimethyl-2,2'-bipyridine-κN,N')zinc(II).

The asymmetric unit of the title compound, [ZnBr(2)(C(12)H(12)N(2))], contains two half-mol-ecules; both are completed by crystallographic twofold axes running through the Zn(II) atoms which are coordinated by an N,N'-bidentate 4,4'-dimethyl-2,2'-bipyridine ligand and two Br(-) ions, resulting in distorted ZnN(2)Br(2) tetra-hedral coordination geometries. In the crystal, C-H⋯Br inter-actions link the mol-ecules.

(2,9-Dimethyl-4,7-diphenyl-1,10-phen-anthroline-κN,N')bis-(thio-cyanato-κS)mercury(II).

In the mol-ecule of the title compound, [Hg(NCS)(2)(C(26)H(20)N(2))], the Hg(II) atom is four-coordinated in a distorted tetra-hedral configuration by two N atoms from a chelating 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline ligand and by two S atoms from two thio-cyanate anions. The ligand ring system is not planar. The dihedral angle between the phenyl rings is 53.20 (3)° . In the crystal structure, π-π contacts between phenanthroline rings [centroid-centroid distance = 3.981 (1) Å] may stabilize the structure.

Tetra-kis(6-methyl-2,2'-bipyridine)-1κN,N';2κN,N';3κN,N';4κN,N'-tetra-µ-nitrato-1:2κO:O';2:3κO:O',O'';2:3κO,O':O'';3:4κO:O'-tetra-nitrato-1κO,O';4κO,O'-tetra-lead(II).

In the tetranuclear centrosymmetric title compound, [Pb(4)(NO(3))(8)(C(11)H(10)N(2))(4)], irregular PbN(2)O(5) and PbN(2)O(4) coordination polyhedra occur. The hepta-coordinated lead(II) ion is bonded to two bidentate and one monodentate nitrate ion and one bidentate 6-methyl-2,2'-bipyridine (mbpy) ligand. The six-coordinate lead(II) ion is bonded to one bidentate and two monodentate nitrate anions and one mbpy ligand. In the crystal, bridging nitrate anions lead to infinite chains propagating in [111]. A number of C-H⋯O hydrogen bonds may stabilize the structure.

Dichlorido(6,6'-dimethyl-2,2'-bipyridine-κN,N')zinc(II).

In the title compound, [ZnCl(2)(C(12)H(12)N(2))], the complete mol-ecule is generated by crystallographic mirror symmetry, with the Zn atom and both chloride ions lying on the reflecting plane, yielding a distorted ZnN(2)Cl(2) tetra-hedral coordination for the metal ion. In the crystal, there are π-π contacts between the pyridine rings [centroid-centroid distance = 3.7857 (17) Å].

Dibromido(6,6'-dimethyl-2,2'-bipyridine-κN,N')zinc(II).

In the title compound, [ZnBr(2)(C(12)H(12)N(2))], the Zn(II) atom is four-coordinated in a distorted tetra-hedral arrangement by an N,N'-bidentate 6,6'-dimethyl-2,2'-bipyridine ligand and two bromide ions. In the crystal, there are aromatic π-π contacts between the pyridine rings [centroid-centroid distances = 3.818 (3) and 3.728 (4) Å].

(6,6'-Dimethyl-2,2'-bipyridine-κN,N')diiodidozinc(II).

The complete mol-ecule of the title compound, [ZnI(2)(C(12)H(12)N(2))], is generated by crystallograpic twofold symmetry, with the Zn(II) atom lying on the rotation axis. The Zn(II) atom is coordinated by the N,N-bidentate 6,6'-dimethyl-2,2'-bipyridine ligand and two iodide ions, resulting in a distorted ZnN(2)I(2) tetra-hedral geometry for the metal. In the crystal, there are weak π-π contacts between the pyridine rings [centroid-centroid distance = 3.978 (3) Å].

Dichloridobis(phenanthridine-κN)zinc(II).

In the mol-ecule of the title compound, [ZnCl(2)(C(13)H(9)N)(2)], the Zn(II) atom is four-coordinated in a distorted tetra-hedral configuration by two N atoms from two phenanthridine ligands and by two terminal Cl atoms. The dihedral angle between the planes of the phenanthridine ring systems is 69.92 (3)°. An intra-molecular C-H⋯Cl inter-action results in the formation of a planar five-membered ring, which is oriented at a dihedral angle of 8.32 (3)° with respect to the adjacent phenanthridine ring system. In the crystal structure, π-π contacts between the phenanthridine systems [centroid-centroid distances = 3.839 (2), 3.617 (1) and 3.682 (1) Å] may stabilize the structure. Two weak C-H⋯π inter-actions are also found.

5,5'-Dimethyl-2,2'-bipyridine.

The asymmetric unit of the title compound, C(12)H(12)N(2), contains two half-mol-ecules related by an inversion center, the planes of their pyridine rings being oriented at a dihedral angle of 69.62 (4)°. In the crystal structure, a π-π contact between the pyridine rings [centroid-centroid distance = 3.895 (3) Å] may stabilize the structure. A weak C-H⋯π inter-action is also found.

Dichlorido(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline-κN,N')mercury(II) acetonitrile hemisolvate.

The asymmetric unit of the title compound, [HgCl(2)(C(26)H(20)N(2))]·0.5CH(3)CN, contains two crystallographic-ally independent [HgCl(2)(C(26)H(20)N(2))] mol-ecules and one acetonitrile solvent mol-ecule. The Hg(II) atoms are four-coordin-ated in distorted tetra-hedral configurations by two N atoms from 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline ligands and two Cl atoms. The ligand ring systems are not planar. The phenyl rings are oriented at dihedral angles of 74.61 (3) and 66.00 (3)° in the two molecules. In the crystal structure, π-π contacts between phenanthroline rings [centroid-centroid distances = 3.809 (1), 3.686 (1), 3.986 (1), 3.877 (1), 3.697 (1), 3.789 (1), 3.745 (1), 3.797 (1) and 3.638 (1) Å] may stabilize the structure.

Dibromido(2,9-dimethyl-1,10-phenanthroline-κN,N')mercury(II).

In the mol-ecule of the title compound, [HgBr(2)(C(14)H(12)N(2))], the Hg(II) atom is four-coordinated in a distorted tetra-hedral configuration by two N atoms from a 2,9-dimethyl-1,10-phenanthroline ligand and by two Br atoms. In the crystal structure, weak inter-molecular C-H⋯Br hydrogen bonds link the mol-ecules into chains along the b axis. There are π-π contacts between the phenanthroline rings [centroid-centroid distances = 3.806 (4), 3.819 (4), 3.739 (3), 3.690 (3), 3.619 (4) and 3.674 (3) Å].

Hydrogen bond controlled adduct formation of meso-tetra(4-sulfonatophenyl)porphyrin with protic acids: a UV-vis spectroscopic study.

Interaction of meso-tetra(4-sulfonatophenyl)porphyrin (H2tppS4) with weak and strong protic acid have been studied by UV-vis spectroscopy in water, dichloromethane and methanol. Different shifts of the Soret and Q(0,0) bands in the three solvents, the aggregation of diprotonated species and the stability of porphyrin-acid adducts in the solution, may be explained by the inter- and intramolecular hydrogen bonds. Whilst, the addition of excess amounts of tetra-n-butylammonium chloride to H2tppS4(Cl)2 in dichloromethane has little to no effect on the UV-vis spectrum of the dication, gradual addition of tetra-n-butylammonium hydrogen sulfate to the dichloromethane solution of H2tppS4(H2SO4)2 leads to the degradation of adducts and the release of porphryin. The results of this study clearly show the crucial role played by hydrogen bonds between the porphyrin diprotonated species and the counter ion in the stability of porphyrin diacids in solution.