Nickel(II) and copper(II) – l-cysteine,l-methionine,l-tryptophan-nucleotide ternary complexes

Four new ternary complexes of Cu^II with l-methionine and the nucleotides 5AMP (adenosine 5-phosphate), 5GMP (guanosine 5-phosphate) and 5IMP (inosine 5-phosphate), and with l-tryptophan and 5AMP, were synthesized and characterized by elemental analysis and i.r. spectroscopy. One ternary complex of N^II with l-cysteine and 5IMP was also prepared and characterized. The study of the three ternary compounds of Cu^II, of general formulae Cu-5NMP-l-methionine, indicates coordination of the phosphate group and of N(7) of the purinic ring. l-Methionine is bound by the carboxylic and amino groups. The ternary complex obtained from a mixture of Cu-5AMP and l-tryptophan is a dimer in which the nucleotide bridges the two copper atoms. In the complex of Ni-5IMP and l-cysteine, the nucleotide seems to bind the metal through the N(7) of the heterocyclic ring, and the l-cysteine is coordinated as a bidentate chelate by the carboxyl and thiol groups. E.s.r. spectra of the copper complexes are in good agreement with the low symmetry structure proposed. The one-electron reduction potentials E_c(Fc⁺/Fc) (V) of Cu^II to Cu^I were established for the four copper complexes from cyclic voltammetry studies. The one-electron oxidation potential E_a(Fc⁺/Fc⁺) (V) of Ni^II to Ni^III was also measured for the nickel complex.     

Phonon-assisted excitonic recombination channels observed in DNA-wrapped carbon nanotubes using photoluminescence spectroscopy

By using a sample of DNA-wrapped single-wall carbon nanotubes strongly enriched in the (6,5) nanotube, photoluminescence emissions observed at special excitation energy values were identified with specific mechanisms of phonon-assisted excitonic absorption and recombination processes associated with (6,5) nanotubes, including one-phonon, two-phonon, and some continuous-luminescence processes. Such detailed processes are not separately identified in three-dimensional semiconducting materials. A general theoretical framework is presented to interpret the experimentally observed phonon-assisted processes in terms of excitonic states.     

Platinum(II) substituted pyrrolidine complexes. Crystal structure of dichloride 1,2 diethyl 3 aminopyrrolidine Pt. Reactions with DNA and dinucleotides

The effect of five derivatives of Pt^II, cis dichloro-(1,2-dimethyl-3-aminopyrrolidine)platinum(II), cis dichloro-(1-methyl, 2-ethyl-3-aminopyrrolidine)platinum(II), cis dichloro-(1-ethyl, 2-methyl-3-aminopyrrolidine)platinum(II), cis dichloro-(1,2-diethyl-3-aminopyrrolidine)platinum(II), and cis dichloro-(1-propyl, 2 methyl-3 aminopyrrolidine)platinum(II) on platination of DNA was studied by CD and melting temperature determination. Reactions with the nucleotides d(ApG) and d(ApA) were also followed by ¹H NMR and CD, indicating binding via N(7) and formation mainly of bifunctional, in the case of d(ApG), or monofunctional adducts, in the case of d(ApA). The crystal structure of cis dichloro-(1 ethyl, 2 methyl-3 aminopyrrolidine)platinum(II) shows the analogues cisplatin structure of these active antitumour complexes. This compound is racemic.