Pedro Florindo

Inhibition of cancer cell growth by ruthenium(II) cyclopentadienyl derivative complexes with heteroaromatic ligands

Inhibition of the growth of LoVo human colon adenocarcinoma and MiaPaCa pancreatic cancer cell lines by two new organometallic ruthenium(II) complexes of general formula [Ru(eta(5)-C(5)H(5))(PP) L][CF(3)SO(3)], where PP is 1,2-bis(diphenylphosphino)ethane and L is 1,3,5-triazine (Tzn) 1 or PP is 2x triphenylphosphine and L is pyridazine (Pyd) 2 has been investigated. Crystal structures of compounds 1 and 2 were determined by X-ray diffraction studies. Atomic force microscopy (AFM) images suggest different mechanisms of interaction with the plasmid pBR322 DNA; while the mode of binding of compound 1 could be intercalation between base pairs of DNA, compound 2 might be involved in a covalent bond formation with N from the purine base.

Cyclopentadienyl–Ruthenium(II) and Iron(II) Organometallic Compounds with Carbohydrate Derivative Ligands as Good Colorectal Anticancer Agents

New ruthenium(II) and iron(II) organometallic compounds of general formula [(η(5)-C5H5)M(PP)Lc][PF6], bearing carbohydrate derivative ligands (Lc), were prepared and fully characterized and the crystal structures of five of those compounds were determined by X-ray diffraction studies. Cell viability of colon cancer HCT116 cell line was determined for a total of 23 organometallic compounds and SARs data analysis within this library showed an interesting dependency of the cytotoxic activity on the carbohydrate moiety, linker, phosphane coligands, and metal center. More importantly, two compounds, 14Ru and 18Ru, matched oxaliplatin IC50 (0.45 μM), the standard metallodrug used in CC chemotherapeutics, and our leading compound 14Ru was shown to be significantly more cytotoxic than oxaliplatin to HCT116 cells, triggering higher levels of caspase-3 and -7 activity and apoptosis in a dose-dependent manner.

Studies of the Antiproliferative Activity of Ruthenium (II) Cyclopentadienyl-Derived Complexes with Nitrogen Coordinated Ligands

Four cationic ruthenium(II) complexes with the formula [Ru(η 5-C5H5)(PPh3)2]+, with L = 5-phenyl-1H-tetrazole (TzH) 1, imidazole (ImH) 2, benzo[1,2-b;4,3-b′] dithio-phen-2-carbonitrile (Bzt) 3, and [5-(2-thiophen-2-yl)-vinyl]-thiophene-2-carbonitrile] (Tvt) 4 were prepared and characterized in view to evaluate their potentialities as antitumor agents. Studies by Circular Dichroism indicated changes in the secondary structure of ct-DNA. Changes in the tertiary structure of pBR322 plasmid DNA were also observed in gel electrophoresis experiment and the images obtained by atomic force microscopy (AFM) suggest strong interaction with pBR322 plasmid DNA; the observed decreasing of the viscosity with time indicates that the complexes do not intercalate between DNA base pairs. Compounds 1, 2, and 3 showed much higher cytotoxicity than the cisplatin against human leukaemia cancer cells (HL-60 cells).

Gas‐phase behaviour of Ru(II) cyclopentadienyl‐derived complexes with N‐coordinated ligands by electrospray ionization mass spectrometry: fragmentation pathways and energetics

RATIONALE The gas-phase behaviour of six Ru(II) cyclopentadienyl-derived complexes with N-coordinated ligands, compounds with antitumor activities against several cancer lines, was studied. This was performed with the intent of establishing fragmentation pathways and to determine the Ru-L(N) and Ru-L(P) ligand bond dissociation energies. Such knowledge can be an important tool for the postulation of the mechanisms of action of these anticancer drugs. METHODS Two types of instruments equipped with electrospray ionisation were used (ion trap and a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer). The dissociation energies were determined using energy-variable collision-induced dissociation measurements in the ion trap. The FTICR instrument was used to perform MS(n) experiments on one of the compounds and to obtain accurate mass measurements. Theoretical calculations were performed at the density functional theory (DFT) level using two different functionals (B3LYP and M06L) to estimate the dissociation energies of the complexes under study. RESULTS The influence of the L(N) on the bond dissociation energy (D) of RuCp compounds with different nitrogen ligands was studied. The lability order of L(N) was: imidazole<1-butylimidazole<5-phenyl-1H-tetrazole<1-benzylimidazole. Both the functionals used gave the following ligand lability order: imidazole<1-benzylimidazole<5-phenyl-1H-tetrazole<1-butylimidazole. It is clear that there is an inversion between 1-benzylimidazole and 1-butylimidazole for the experimental and theoretical lability orders. The M06L functional afforded values of D closer to the experimental values. The type of phosphane (L(P) ) influenced the dissociation energies, with values of D being higher for Ru-L(N) with 1-butylimidazole when the phosphane was 1,2-bis(diphenylphosphino)ethane. The Ru-L(P) bond dissociation energy for triphenylphosphane was independent of the type of complex. CONCLUSIONS The D values of Ru-L(N) and Ru-L(P) were determined for all six compounds and compared with the values calculated by the DFT method. For the imidazole-derived ligands the energy trend was rationalized in terms of the increasing extension of the σ-donation/π-backdonation effect. The bond dissociation energy of Ru-PPh(3) was independent of the fragmentations.

pH-Switchability and Second-Order Nonlinear Optical Properties of Monocyclopentadienylruthenium(II)/iron(II) Tetrazoles/Tetrazolates: Synthesis, Characterization, and Time-Dependent Density Functional Theory Calculations

Tetrazole/tetrazolate monocyclopentadienyliron(II) and ruthenium(II) compounds of general formulas [(η5-C5H5)M(dppe)(N4(H)CC6H4NO2)][PF6]/[(η5-C5H5)M(dppe)(N4CC6H4NO2)] were investigated for their pH-switching second-order nonlinear optical (SONLO) properties. Compounds [(η5-C5H5)M(dppe)(N4CC6H4NO2)] (M = Fe, Ru) and compound [(η5-C5H5)Ru(dppe)(N4(H)CC6H4NO2)][PF6] were fully characterized by (1H-, 13C-, 31P-) NMR, cyclic voltammetry, and elemental analysis, and compounds [(η5-C5H5)Fe(dppe)(N4CC6H4NO2)] and [(η5-C5H5)Ru(dppe)(N4(H)CC6H4NO2)][PF6] were further characterized by single-crystal X-ray diffraction; the synthesis of [(η5-C5H5)Fe(dppe)(N4(H)CC6H4NO2)][PF6] was unsuccessful. Time-dependent density functional theory calculations were performed using PBE0 and CAM-B3LYP functionals to evaluate the first hyperpolarizability (βtot) of the tetrazole/tetrazolate complexes and for a detailed analysis of the experimental data. Both functionals predict (i) high first hyperpolarizabilities for the tetrazolate complexes [(η5-C5H5)M(dppe)(N4CC6H4NO2)], with βtot[Ru] ≈ 1.2βtot[Fe], and (ii) a 3-fold reduction in βtot[Ru] upon protonation, in complex [(η5-C5H5)Ru(dppe)(N4(H)CC6H4NO2)]+, forecasting [(η5-C5H5)Ru(dppe)(N4CC6H4NO2)]/[(η5-C5H5)Ru(dppe)(N4(H)CC6H4NO2)]+ complexes as on/off, pH-switchable SONLO forms.

Design and synthesis of NLO efficient organometallic molecules

Second-order nonlinear optical (SO-NLO) properties of group 8 half-sandwich organometallic complexes have been intensively studied throughout the last 15 years, making this class of compounds relevant for the continuous search of NLO materials. This contribution surveys the ongoing efforts to design, characterize and optimize the NLO properties of this class of compounds. Computational studies, namely DFT calculations, were performed for several model molecules in order to predict the first hyperpolarizabilities and to support experimental evidences.