Crystal and Molecular Structure of a Potential DNA Groove-Spanning Chelate: [MV][Pt(2)(hdta)Cl(2)].4H(2)O (MV(2+) = 1,1'-Dimethyl-4,4'-bipyridinium, hdta(4)(-) = 1,6-Hexanediamine-N,N,N',N'-tetraacetate)

[N,N’-diethyl-4,4′-bipyridinium][CdX4] (X = Cl or Br) with N,N’-diethyl-4,4′-bipyridinium generated in situ: An Effective Route to Viologen Compounds

Two viologen (4,4‘-bipyridinium) compounds, [MQ2+][CdX4] (X = Cl or Br; MQ2+=N,N’-diethyl-4,4′-bipyridinium) with the MQ2+ generated in situ, have been synthesised via solvothermal reactions and structurally characterised by single-crystal X-ray diffraction. The MQ2+ moieties and [CdX4]2– anions are interconnected by hydrogen bonding to form a supramolecular framework. Both compounds exhibit broad and strong emission in the yellow region which, following theoretical investigation, is ascribed to ligand-to-ligand charge transfer.

Interaction of N-acetylmethionine with a non-C2-symmetrical platinum diamine complex

The reaction of N-acetylmethionine (N-AcMet) with the complex [Pt(Et(2)en)(D(2)O)(2)](2+) (Et(2)en=N,N-diethylethylenediamine) was studied by NMR spectroscopy and molecular mechanics calculations. Complexes containing two methionine residues coordinated to the platinum atom were calculated to be relatively high in energy unless the bulk of the methionine residues was directed away from the diethyl group of the Et(2)en ligand. In contrast, sulfur-oxygen chelates were found to be relatively free of steric clashes. Experimentally, two sets of NMR resonances were observed when [Pt(Et(2)en)(D(2)O)(2)](2+) was reacted with N-AcMet; variable temperature experiments indicated intermediate chemical exchange between the two sets of resonances. NMR studies indicated that the resonances corresponded to [Pt(Et(2)en)(N-AcMet-S,O)](+) complexes with the sulfur atom trans to the diethyl group of the Et(2)en ligand. No product with the sulfur atom cis to the diethyl group was observed experimentally even though molecular mechanics calculations suggested that such forms have few steric clashes. The NMR results suggested that the chemical exchange was a result of sulfur chirality inversion. In early stages of the reaction, a [Pt(Et(2)en)(N-AcMet-S)(D(2)O)](+) complex was observed, indicating that coordination of the oxygen to form the chelate is relatively slow.