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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. |
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