Novel Complexes of Gallium(III), Indium(III), and Thallium(III) with Pyridine-Containing Proton Transfer Ion Pairs Obtained from Dipicolinic Acid - Synthesis, Characterization and X-ray Crystal Structure

Ga(III) pyridinecarboxylate complexes: potential analogues of the second generation of therapeutic Ga(III) complexes?

A series of novel Ga(III)-pyridine carboxylates ([Ga(Pic)3]·H2O (GaPic; HPic = picolinic acid), H3O[Ga(Dpic)2]·H2O (GaDpic; H2Dpic = dipicolinic acid), [Ga(Chel)(H2O)(OH)]2·4H2O (GaChel; H2Chel = chelidamic acid) and [Ga(Cldpic)(H2O)(OH)]2 (GaCldpic; H2Cldpic = 4-chlorodipicolinic acid)) have been synthesized by simple one-step procedure. Vibrational spectroscopy (mid-IR), elemental analysis, thermogravimetric analysis and X-ray diffraction confirmed complexes molecular structure, inter and intramolecular interactions and their influence to spectral and thermal properties. Moreover, complex species speciation was described in Ga(III)-HPic and Ga(III)-H2Dpic systems by potentiometry and 1H NMR spectroscopy and mononuclear complex species were determined; [Ga(Pic)2]+ (logβ021 = 16.23(6)), [Ga(Pic)3] (logβ031 = 20.86(2)), [Ga(Dpic)2]- (logβ021 = 15.42(9)) and [Ga(Dpic)2(OH)]2- (logβ-121 = 11.08(4)). To confirm the complexes stability in 1% DMSO (primary solvent for biological testing), timescale 1H NMR spectra were measured (immediately after dissolution up to 96 h). Antimicrobial activity evaluated by IC50 (0.05 mM) is significant for GaDpic and GaCldpic against difficult to treat and multi-resistant P. aeruginosa. On the other hand, the GaPic complex is most effective against Jurkat, MDA-MB-231 and A2058 cancer cell lines and significantly also decreases the HepG2 cancer cells viability at 75 and 100 μM concentrations in a relatively short time (up to 48 h). In addition, fluorescence measurements have been used to elucidate bovine serum albumin binding activity between ligands, Ga(III) complexes and bovine serum albumin.

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.

Bis-(μ-pyridine-2,3-dicarboxyl-ato)bis-[aqua-(3-carb-oxy-pyridine-2-carboxyl-ato)indium(III)] tetra-hydrate

In the binuclear centrosymmetric title compound, [In(2)(C(7)H(3)NO(4))(2)(C(7)H(4)NO(4))(2)(H(2)O)(2)]·4H(2)O, which contains both pyridine-2,3-dicarboxyl-ate and 3-carb-oxy-pyridine-2-carboxyl-ate ligands, the In(III) atom is six-coordinated in a distorted octa-hedral geometry. One pyridine ligand is N,O-chelated while the other is N,O-chelated and at the same time bridging to the other via the second carboxyl group. In the crystal, an extensive O-H⋯O hydrogen-bonding network, involving the coordinated and lattice water mol-ecules and the carboxyl groups of the ligands, together with C-H⋯O and π-π inter-actions [centroid-centroid distance = 3.793 (1) Å], leads to the formation of a three-dimensional structure.

Hexa-kis-(dimethyl sulfoxide-κO)thallium(III) trinitrate

The title compound, [Tl(C₂H₆OS)₆](NO₃)₃, consists of six dimethyl sulfoxide (DMSO) mol­ecules coordinated to a Tl^III atom, which lies on a axis, and three nitrate anions (3. symmetry) to neutralize the charge. The coordination polyhedron around the Tl^III atom is octa­hedral, defined by six O atoms of the DMSO mol­ecules. In the crystal structure, C—H⋯O hydrogen bonds are observed. One of the nitrate groups exhibits half-occupation.

Synthesis, characterisation, DFT and biomedical investigation of new Ga(III) complex with imidazole

A new Ga(III) complex with imidazole (IMZ) in 1:2 Ga:IMZ stoichiometric ratio has been synthesised. The complex has been characterised by spectroscopic (IR, NMR, UV-Vis.,), thermogravimetric (TG, DTG, DTA), electrophoresis and microanalytical techniques and shown to be [GaCl(IMZ)2(H2O)]. The geometry of [GaCl(IMZ)2(H2O)] was optimised in a singlet state by the DFT method with B3LYP functional. Theoretical analysis of vibration modes of this complex has been undertaken and the results were compared with the experimental data for this compound. The complex was subjected to radiolabelling with 67Ga via the nuclear reaction 68Zn (p, 2n) 67Ga. The radiochemical yield was greater than 80%. HPLC analysis in isotonic systems revealed that this complex is highly unstable in an isotonic system where it readily dissociated. The investigated complex showed relatively high anti-bacterial activities compared with the free ligand.