João Madureira

Synthesis and structural characterisation of new RuII[12]aneS4 complexes with polypyridylic and related ligands

The reaction between cis-[Ru(dmso)Cl2] (dmso=dimethylsulfoxide) and the macrocycle 1,4,7,10-tetrathiacyclododecane ([12]aneS4) gives the complex cation [Ru([12]aneS4)(dmso)Cl]+. A new series of RuII([12]aneS4) complexes were obtained by replacing the dmso and the chlorine ligands with polypyridylic or related monodentate ligands. Complexes with the general formula [Ru([12]aneS4)(L)]2+, where L=bidentate ligand: dipyridylamine (dipa); 5-phenyl-1,10-phenanthroline (5-phen); 1,10-phenanthroline-5,6-dione (5,6-dione); o-phenylenediamine (pda) or 4,4′-diphenyl-2,2′-dipyridyl (dbp) have been synthesised. Related complexes containing monodentate ligands, [Ru([12]aneS4)(CH3CN)Cl]+, [Ru([12]aneS4)(CH3CN)2]2+ and [Ru([12]aneS4)(ind)Cl)]+ (ind=indazole) were also prepared. The complexes were characterised by NMR, UV/Vis and IR spectroscopy and their electrochemical behaviour was studied by cyclic voltammetry. The X-ray single crystal diffraction structures of the complexes [Ru([12]aneS4)(dmso)Cl]Cl, [Ru([12]aneS4)(CH3CN)2][PF6]2, [Ru([12]aneS4)(CH3CN)Cl]PF6, [Ru([12]aneS4)(5,6-dione)][PF6]2·2CH3CN, [Ru([12]aneS4)(5-phen)][PF6]2 and [Ru([12]aneS4)(ind)Cl]PF6·CH3CN were determined. All complexes exhibit a distorted cis-octahedral environment with the macrocycle adopting a folded conformation.

Bimetallic transition metal–ruthenium(II) complexes containing bridging bipyrimidine ligands

Abstract The ruthenium(II) complex [Ru([14]aneS4)(bpym)](BF4)2 ([14]aneS4=1,4,8,11-tetrathiacyclotetradecane, bpym=2,2′-bipyrimidine) has been prepared by substitution of the labile acetonitrile ligands in the complex [Ru([14]aneS4)(CH3CN)2](BF4)2 by bpym. Both the precursor acetonitrile complex and the polypyridyl complex were characterised by Ru K-edge EXAFS spectroscopy. In addition, the crystal structures of [Ru([14]aneS4)(bpym)](X)2 (X=BF4, PF6) were determined by X-ray diffraction. The bpym-bridged bimetallic complexes [{Ru([14]aneS4)}2(bpym)](BF4)4 and [{([14]aneS4)Ru}(bpym){ReO3Me}](BF4)2 were prepared using the ruthenium(II) monomeric bpym complex as starting material. In the case of the complex containing methyltrioxorhenium(VII) coordination of both metal centres to the bidentate bridging ligand was supported by a combination of Ru K-edge and Re L-edge XAFS spectroscopy, in addition to 1H NMR.

Structural characterisation and DFT studies of (Cr(cyclam)(O-dmso)Cl) 2 : a new precursor complex towards potential DNA intercalators

The synthesis and structural characterisation of the complex [Cr([14]aneN4)(O -dmso)Cl](PF6)2/dmso is reported. The structural studies were carried out in gas-phase by electrospray mass spectrometry (ESMS) and in the solid state by single crystal X-ray diffraction. The metal complex shows a distorted octahedral coordination environment with the macrocycle adopting a folded cis -V conformation. The angle Naxial � /Cr� /Naxial deviates by only 128 from the ideal value of 1808 for a perfect octahedron indicating that there is a good match between the size of the macrocyclic cavity and the size of Cr(III) ion. The ESMS shows that the complex loses a proton with concomitant opening of the [14]aneN4 ring to give the [Cr([14]aneN4-H)(dmso)Cl] � ion with a CH2� /CH� / pendant chain. This group interacts with dmso leading to the loss of this ligand and to the formation of the [Cr([14]aneN4-H)Cl] � ion, which has the highest relative abundance (100%). DFT calculations reproduce the geometry of the paramagnetic complex and are consistent with its electronic spectrum. # 2003 Elsevier Science B.V. All rights reserved.

Synthesis and characterisation of ruthenium(II) complexes containing ferrocenyl-derived ligands

Ruthenium(II) complexes containing the macrocycle [14]aneS4 and pyridyl ligands with an end-capping ferrocene were prepared using [Ru([14]aneS4)(DMSO)Cl]Cl as the starting material. Substitution of the DMSO ligand by 4-ferrocenylpyridine (4-FP), ferrocenyl-4-pyridylacetylene (FPA) and pyridine (py) gave the complexes [Ru([14]aneS4)(L)Cl]Cl (L=4-FP, FPA, py). The acetonitrile complex [Ru([14]aneS4)(NCMe)2](BF4)2 was also prepared starting from [Ru([14]aneS4)(DMSO)Cl]Cl. UV/Vis absorption spectroscopy and cyclic voltammetry indicate low electronic communication between the metal centres in the heterobimetallic complexes. The crystal structure of [Ru([14]aneS4)(4-FP)Cl]Cl was determined by X-ray diffraction. Crystal data: C25.780H37.134Cl2FeNO1.288S4Ru, M=737.82, monoclinic, space group P2/n, a=13.192(1), b=7.6662(6), c=28.549(2) A, β=100.341(2)°, V=2840.4(4) A3, Z=4.

Nonclassic Metallointercalators with Dipyridophenazine: DNA Interaction Studies and Leishmanicidal Activity

Complexes [Cu(CH3COO)(dppz)2]CH3COO (1) and [Zn(dppz)2](BF4)2 (2) with the intercalator dipyridophenazine (dppz) were prepared to obtain metallointercalators with increased geometrical flexibility compared to octahedral ones. Biophysical results (thermal denaturation, circular dichroism, rheometry, atomic force microscopy) indicate a strong interaction with DNA by intercalation and the existence of a positive cooperative effect with groove binding being preferred at low concentration of complexes. Induced circular dichroism (ICD) studies with DNA show that compounds 1 and 2 have a preferred orientation when binding to DNA. Since the compounds lack functional groups to permit hydrogen bonds, a combined intercalation/covalent binding mode is plausible. Further studies by QTof-ESI-MS and tandem experiments with GC oligonucleotides strongly support this dual-binding mode, since binding requires loss of one dppz unit with the copper center remaining attached to DNA even after another dppz loss. DNA saturation by the copper compound occurs at about one-half the concentration required for the zinc complex. Molecular modeling results suggest that it is caused by the increased ability of Cu(II) to distort to a more planar structure during interaction with DNA. Compounds 1 and 2 are active against a viscerotropic Leishmania infantum strain at submicromolar concentrations (IC50 = 0.57 and 0.46 μM, respectively), being more active than the reference drug miltefosine (M) (15.97 μM). They are also more cytotoxic than the control on human macrophages (MTD25 = 0.41 (1), 0.63 (2)). Besides miltefosine, the zinc compound is the only one with a MTD25/IC50 ratio above 1 on the promastigote phase (1.39) and was further studied on the amastigote form with a significant improvement in the therapeutic index (2.51). Combined analysis of DNA biophysical studies, parasite activity, and cytotoxicity measurements suggests that intercalation correlates with leishmanicidal activity, while cytotoxicity results are justified by a combination of DNA intercalation and possible radical formation in the case of Cu(II), most probably hydroxyl and/or singlet oxygen radicals.

Solution and solid-state spectroscopic characterization of chloro dimethylsulfoxide polythioether ruthenium(II) complexes, complemented with DFT calculations in the gas phase

Several ruthenium(II)-chloro-dimethylsulfoxide complexes with formulae [RuCl2(DMSO)(k 3-L1)] or [RuCl(DMSO)(k 4-L2)]+, where L1 = [9]aneS3 (2) or ttbt (5) and L2 = [12]aneS4 (3), [14]aneS4 (4) or [14]aneN4 (6), have been synthesized from cis,fac-[RuCl2(S-DMSO)3(O-DMSO)] (1) and the respective macrocycle. They were spectroscopically characterized by FT-IR, FT-Raman, NMR, and UV/Vis. Particular attention was given to fac-[RuCl2(DMSO)(k 3-ttbt)] (5), the first octahedral complex of ttbt, which was also studied by DFT calculations. The behavior of the complexes in coordinating solvents water, acetonitrile, and dimethylsulfoxide was studied to understand their reactivity and predict the resulting ions formed in solution. The role of the counter ion (Cl− vs. ) was also evaluated. The results indicate that the chosen macrocycle, the counter-ion, and the solvent have a direct impact on the chemical species formed in solution.