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The [(COD)M(R)] 14 VE complex fragments (COD = 1,5-cyclooctadiene, R = methyl or neopentyl (2,2-dimethylpropyl), M = Pd or Pt) bind to the nucleobases cytosine (Cyt) or uracil (Ura), to the methylated nucleobase derivatives 1-methylcytosine (1MeCyt) or 1-methyluracil (1MeUra), and to the related ligand caffeine (Caf) (1,3,7-trimethylxanthine). From the potentially bridging cytosinate ligand a binuclear platinum complex [(COD)(Me)Pt(N3-cytosinate-N1)Pt(Me)-(COD)] + was obtained. The solubility of the corresponding complexes in organic solvents allowed their characterization by multiple ( 1 H, 13 C, and 195 Pt) NMR spectroscopy and in some cases by crystal structure analysis. Relative ligand-metal bond strength were discussed in view of 1 H-195 Pt NMR coupling constants. Further focus lies on the observation of binding isomers, the formation of binuclear species, multiple substitution, and the observed differences between Pt and Pd derivatives. Cytotoxicity experiments on HT-29 colon carcinoma and MCF-7 breast cancer cell lines revealed promising activities for selected platinum COD complexes.

New organometallic palladium complexes of the general type [(RR'dppz)Pd(Me)L](n+) (RR'dppz = derivatives of dipyrido[3,2-a:2',3'-c]phenazine with RR' = 11-Cl, 11,12-Cl(2), 11-CF(3), 11-NO(2), 11-NH(2); L = Cl, 1-methyluracilate (n = 0), pyridine, cytosine, caffeine, or 1-methylcytosine, (all n = 1) were characterised and studied in detail by electrochemical and spectroscopic (NMR, UV/Vis- absorption and emission) methods. EPR spectroscopy and density functional calculations reveal markedly tuneable lowest unoccupied molecular orbitals (LUMO) located at the dppz ligands. Cytotoxicity experiments on HT-29 colon carcinoma and MCF-7 breast cancer cell lines show promising activities for selected compounds.

Coordination of the 2,6-bis(hydroxymethyl)pyridine-based oxido pincer ligands RRЈpydimH 2 [R = RЈ = H (pydimH 2 ); R = RЈ = Me (pydipH 2 ); R = 2-tolyl, RЈ = Me (pydotH 2 )

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