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The homoleptic [Ru(trpyCO-TrpCONH2)2](PF6)2 (1), [Ru(trpyCO-Gly-TrpCONH2)2](PF6)2 (2) and the heteroleptic complexes [Ru(trpy)(trpyCO-TrpCONH2)](PF6)2 (3), [Ru(trpy)(trpyCO-Gly-TrpCONH2)](PF6)2 (4), where trpyCO-TrpCONH2 and trpyCO-Gly-TrpCONH2 are 2,2′:6′,2″-terpyridine-4-carboxylic acid-tryptophanamide and 2,2′:6′,2″-terpyridine-4-carboxylic acid-glycyl-tryptophanamide respectively, were synthesized and characterized by various spectroscopic and analytical techniques. The interactions of complexes (1) and (4) with the oligonucleotide d(5′-CGCGAATTCGCG-3′)2 were studied by means of NMR spectroscopy. Both complexes bound very weakly to the oligonucleotide, perturbing slightly the helix from B-form, probably through electrostatic interactions between the positive charge of the complexes and the DNA phosphates. In the case of complex (1), the conjugated tryptophane did not approach the oligonucleotide helix, as in the case of complex (4), the unsubstituted trpy of which was clearly orientated towards the oligonucleotide helix. These observations indicate that the bulky substitute on the ligand trpy reduces the binding affinity of the complexes to DNA, allowing only electrostatic interactions. However, complex (4) shows high cytotoxicity against LMS, MCF-7, U2OS and K562 cancer cell lines, with IC50 values ranging 0.464–0.925 μM, which can be attributed to a non classical mechanism for metal based anticancer agents.

The employment of pyridine-2-amidoxime (ampaoH), 2,6-diacetylpyridine dioxime (dapdoH 2 ) and pyridine-2,6-diamidoxime (dampdoH 2 ) in zinc(II) chemistry is reported. The syntheses, crystal structures, spectroscopic and physicochemical characterization, and biological evaluation are described of [Zn(O 2 CMe) 2 (ampaoH) 2 ] ( 1 ), [Zn(O 2 CPh) 2 (ampaoH) 2 ] ( 2 ), [Zn(dapdoH 2 ) 2 ](NO 3 ) 2 ( 3 ) and [Zn(dampdoH 2 ) 2 ](NO 3 ) 2 ( 4 ). The reactions between Zn(NO 3 ) 2 ·4H 2 O and two equivalents of either dapdoH 2 or dampdoH 2 in MeOH led to the mononuclear, cationic complexes 3 or 4 , respectively. The Zn II center in 3 and 4 is coordinated by two N , N ′, N ″-tridentate chelating ( η 3 ) dapdoH 2 or dampdoH 2 ligands, and it thus possesses a distorted octahedral coordination geometry. Strong intermolecular hydrogen bonding interactions provide appreciable thermodynamic stability and interesting supramolecular chemistry for compounds 1 – 4 . The characterization of all four complexes with 1 H and 13 C NMR, and positive ion electrospray mass spectroscopies confirmed their integrity in DMSO solutions. The biological evaluation of complex 3 showed the highest cytotoxic activity against LMS and MCF-7 cells, among the other three complexes ( 1 , 2 and 4 ). Flow cytometry analysis revealed that all four complexes cause apoptosis to LMS cells, at a dose-dependent manner. The combined work demonstrates the ability of pyridyl monoxime and pyridyl dioxime chelates not only to lead to polynuclear 3d-metal complexes with impressive structural motifs and interesting magnetic and optical properties, but also to yield new, mononuclear transition metal complexes with biological implications.