A new mixed ligand-silver(I) complex of formula [Ag(tpp)(2)(p-Hbza)] (1) (p-HbzaH = 4-hydroxybenzoic acid and tpp = triphenylphosphine) has been synthesized and characterized by elemental analysis, mp, vibrational spectroscopy (mid- and far-FT-IR), (1)H-NMR, UV-vis, ESI-MS spectroscopic techniques and X-ray crystallography. Complex 1 and the already known mixed ligand-silver(I) complexes of formulae [Ag(tpp)(2)(salH)] (2) (salH(2) = salicylic acid or 2-hydroxy-benzoic acid) and {[Ag(tpp)(3)(asp)](dmf)} (3) (aspH = o-acetylsalicylic acid) were used for the clarification of the cytostatic activity mechanism. Thus, 1-3 were tested for their in vitro cytotoxic activity against leiomyosarcoma (LMS) and human breast adenocarcinoma (MCF-7) cells with trypan blue and Thiazolyl Blue Tetrazolium Bromide (MTT) assays. For both cell lines, complexes 1-3 were found to be more active than cisplatin. Due to the morphology of the LMS cells after incubation with 1-3, the type of cell death was evaluated by flow cytometry assay and DNA fragmentation. The results show that LMS cells undergo programmed cell death (apoptosis). DNA binding tests indicate the ability of complexes 1-3 to modify the activity of the cells. The binding constants of 1-3 towards calf-thymus DNA (CT-DNA) ((27.7 ± 7.9) × 10(4) (1), (13.3 ± 6.5) × 10(4) (2) and (11 ± 2.8) × 10(4) (3) M(-1)) indicate strong interaction. Moreover, the influence of complexes 1-3 on the catalytic peroxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase (LOX) was kinetically studied. Finally, docking studies on DNA binding interactions were performed.

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Crystal structures are reported for the following complexes [Fe 3 O(OOCCMe 3 ) 6 (py) 3 ]ClO 4 ‚0.5py, 1; [Mn 3 O-(OOCCMe 3 ) 6 (py) 3 ]ClO 4 ‚MeCN, 2; [Mn 3 O(OOCCMe 3 ) 6 (py) 3 ], 4; [Fe 3 O(OOCCMe 3 ) 6 (py) 3 ], 5. Crystal data are as follows: 1, system monoclinic, space group P2 1 /n, a ) 11.658(5) Å, b ) 35.450(5) Å, c ) 14.084(5) Å, β )In 1 and 2, the triangular metal ion clusters are close to equilateral geometry, but the coordination polyhedra of the metal ions are significantly different. Those of the fully oxidized triiron(III) cluster are close to the ideal tetragonal symmetry. Those of the trimanganese(III) cluster show strong Jahn-Teller distortions, the four Mn-carboxylate bonds defining a long and a short O-Mn-O axis and these axes around the three Mn centers being correlated so as to define an approximate 3-fold screw axis for the whole cluster. In the mixed-valence trimanganese complex 4 the coordination implies localized valence states close to (2Mn 3+ + Mn 2+ ) but in the triiron complex 5 the bond distances are close to those expected for a partially averaged state (2Fe 2.5+ + Fe 3+ ). Mo ¨ssbauer spectra of the mixed-valence iron complex indicate a phase transition to a localized (2Fe 3+ + Fe 2+ ) state below T ) 96 K. In the high-temperature phase, IR spectra support a model in which the electron transfer takes place between two adjacent iron centers at a rate which remains lower than that of the infrared time scale up to room temperature.