Tuning the electronic properties of dppz-ligands and their palladium(II) 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.