Sunlight-driven formation and dissociation of a dynamic mixed-valence thallium(III)/thallium(I) porphyrin complex

Novel Tl(III) complexes containing pyridine-2,6-dicarboxylate derivatives with selective anticancer activity through inducing mitochondria-mediated apoptosis in A375 cells

Three novel Tl(III) complexes (C1), (C2) and (C3) were synthesized using the one-pot reactions of pyridine dicarboxylic acid derivatives, 2-aminobenzimidazole and/or 4-aminopyridine, and also thallium(III) nitrate trihydrate metal salt. The structure of all three complexes was determined by the single-crystal X-ray diffraction. C1 and C2 were realized to be isostructural with disordered square anti-prismatic geometry and for C3 arrangement of the distorted tricapped triangular prism was proposed. Cyclic voltammetry measurements on the complexes exhibited that formal potential values are more positive for C1 (E⁰' 0.109 V) and C3 (E⁰' 0.244 V) compared to C2 (E⁰' -0.051 V), versus Ag/AgCl under argon. Moreover, cytotoxicity of the compounds was evaluated in vitro against two cancer cell lines including a human melanoma (A375), a human colon adenocarcinoma (HT29), and also one normal cell human foreskin fibroblast (HFF). The selective and potent cytotoxicity effect was exhibited by C1 and C3 on cancer cell lines. The apoptosis through a caspase-dependent mitochondrion pathway was confirmed by ROS production, MMP reduction, p53 activation, Bax up-regulation, and Bcl-2 down-regulation, cytochrome c release, procaspase-9, and 3 expression, for A375 cells treated to C1 and C3. According to similar cellular uptake of the complexes in A375 cell line, the generation of ROS was considered as an effective agent to justify the inhibition effect C1 and C3 on mentioned cells. Furthermore, arresting the cell cycle in the G2-M phase and inducing apoptosis were indicated by these two complexes.

HgII -Mediated TlI -to-TlIII Oxidation in Dynamic PbII /Tl Porphyrin Complexes

Compared with their purely organic counterparts, molecular switches that are based on metal ion translocations have been underexplored, and more particularly, it remains challenging to control the translocation of several particles in multisite receptors. Recently, bimetallic complexes that undergo double translocation processes have been developed with bis-strapped porphyrin ligands. To implement a redox control for these systems, we have investigated the formation of heterobimetallic lead/thallium complexes, with thallium in the +I and +III oxidation states. Two different complexes were characterized: 1) a Pb^II /Tl^I complex, in which both metal ions interact with the N-core on its different sides, and 2) a Pb^II /Tl^III complex with Tl^III selectively bound to the N-core and Pb^II selectively bound to the strap opposite to Tl^III . These two complexes undergo interconversion between their two degenerate forms (same coordination of the metal ions but on opposite sides) by different intra or intermolecular translocation pathways. In addition, conversion of the Pb^II /Tl^I complex into its Pb^II /Tl^III counterpart was achieved by addition of a stoichiometric amount of Hg^II salt as a sacrificial electron acceptor. These results further contribute to the elaboration of devices that feature redox-controlled compartmentalized double translocations.

Structural analysis of a dimeric trinuclear zinc(II) complex based on a preorganized yet flexible strap porphyrin

We report the solid-state structure of an unexpected trinuclear zinc dimeric porphyrin complex resulting of zinc insertion into a single strap porphyrin. The latter bears an overhanging carboxylic acid which usually interacts with metal cations either in out-of-plane (OOP) or in hanging-atop (HAT) coordination mode by changing its location above the porphyrin coordination site. However, in the present studies, the overhanging carboxylic group acts as a bidentate ligand and binds the OOP-bound zinc cation together with another zinc cation bridging two porphyrin units.

Structurally characterized bimetallic porphyrin complexes of Pb, Bi, Hg and Tl based on unusual coordination modes

This minireview highlights the unusual coordination geometries observed in bimetallic complexes of mercury, thallium, lead and bismuth. These bimetallic complexes remain scarce and through an analysis of their X-ray structures, the various structural features that favorise them will be underlined.

Spontaneous Tl(i)-to-Tl(iii) oxidation in dynamic heterobimetallic Hg(ii)/Tl(i) porphyrin complexes

Strapped heterobimetallic Hg(ii)/Tl(i) porphyrin complexes undergo spontaneous Tl(i)-to-Tl(iii) oxidation, providing a new opportunity to tune metal ion translocations in bimetallic porphyrin systems.

Compartmentalized vs. non-compartmentalized translocations in metal porphyrin complexes

Strapped porphyrin ligands exhibit instantaneous and easy-to-control formation of various bimetallic species featuring new coordination modes and dynamics.