M. Helena Garcia

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.

Hyper-Rayleigh scattering study of η5-monocyclopentadienyl–metal complexes for second order non-linear optical materials

A series of ionic η5-monocyclopentadienyl–metal compounds possessing p-substituted benzonitrile ligands has been studied by hyper-Rayleigh scattering at the fundamental wavelength of 1.064 µm. Upon systematic variation of the metal ion, the first hyperpolarizability β was found to increase along the sequence Co, Ni, Ru, Fe, with about a three-fold increase from Ru to Fe. This yields very high values for the iron complexes, e.g., β=410×10–30 esu for [Fe(η5-C5H5)(dppe)( p-NCC6H4NO2)]+ [PF6 ]– dissolved in methanol. The high β values are attributed to π back-donation resulting in an extension of the conjugated π-system from the FeII organometallic fragment, acting as a good donor group, via the nitrile to the acceptor group NO2 . Complexes with single phenyl rings as conjugated chains perform better than their biphenyl analogues, which is explained in terms of non-planarity of the coordinated biphenyl ligands in solution. By comparing complexes with electron donor and acceptor substituted ligands it is demonstrated that the organometallic moiety can be used as an extremely effective donor group but not as a good acceptor group.

Synthesis and characterization of η5-monocyclopentadienyl (p-nitrobenzonitrile)ruthenium(II) salts: Second harmonic generation powder efficiencies

Abstract A new family of salts [Ru(η 5 -C 5 H 5 ((+)-(DIOP)( p -NCC 6 H 4 NO 2 )][X] (X = p -CH 3 C 6 H 4 SO 3 − , Cl − , NO 3 − , BF 4 − , PF 6 − , ClO 4 − and CF 3 SO 3 − ), has been synthesized. Variation of the counterion shows that [Ru(η 5 -C 5 H 5 ((+)-(DIOP)( p -NCC 6 H 4 NO 2 )]+ can improve by a factor of 25 the value of second harmonic generation powder efficiency. The relation between 1 H and 13 C NMR spectroscopic data and second harmonic generation values accounts for an electronic interaction between the counterions and π delocalized electronic system on the chromophore.

Organometallic compounds for non-linear optics: Synthesis, reactivity and electrochemistry of chiral η5-monocyclopentadienyl(nitrile)iron complexes

Abstract A new family of compounds of general formula [FeCp ((+)-DIOP)(p-NCC6H4R′)][PF6] (R′ = donor or acceptor group) was synthesized and characterized for non-linear optical properties. Spectroscopic (IR and 1H 13C and 31P NMR) and electrochemical (cyclic voltammetry) studies are consistent with charge-transfer from FeII to coordinated benzonitrile via d-π* back donation. One compound of this family, [FeCp((+)-DIOP)(p-NCC6H4NO2)][PF6] has an SHG value 38 times greater than that of urea.

A novel VIVO–pyrimidinone complex: synthesis, solution speciation and human serum protein binding

The pyrimidinones mhcpe, 2-methyl-3H-5-hydroxy-6-carboxy-4-pyrimidinone ethyl ester (mhcpe, 1), 2,3-dimethyl-5-benzyloxy-6-carboxy-4-pyrimidinone ethyl ester (dbcpe, 2) and N-methyl-2,3-dimethyl-5-hydroxy-6-carboxyamido-4-pyrimidinone (N-MeHOPY, 3), are synthesized and their structures determined by single crystal X-ray diffraction. The acid-base properties of 1 are studied by potentiometric and spectrophotometric methods, the pK(a) values being 1.14 and 6.35. DFT calculations were carried out to determine the most stable structure for each of the H2L(+), HL and L(-) forms (HL = mhcpe) and assign the groups involved in the protonation-deprotonation processes. The mhcpe(-) ligand forms stable complexes with V(IV)O(2+) in the pH range 2 to 10, and potentiometry, EPR and UV-Vis techniques are used to identify and characterize the V(IV)O-mhcpe species formed. The results are consistent with the formation of V(IV)O, (V(IV)O)L, (V(IV)O)L2, (V(IV)O)2L2H(-2), (V(IV)O)L2H(-1), (V(IV)O)2L2H(-3), (V(IV)O)LH(-2) species and V(IV)O-hydrolysis products. Calculations indicate that the global binding ability of mhcpe towards V(IV)O(2+) is similar to that of maltol (Hmaltol = 3-hydroxy-2-methyl-4H-pyran-4-one) and lower than that of 1,2-dimethyl-3-hydroxy-4-pyridinone (Hdhp). The interaction of V(IV)O-complexes with human plasma proteins (transferrin and albumin) is studied by circular dichroism (CD), EPR and (51)V NMR spectroscopy. V(IV)O-mhcpe-protein ternary complexes are formed in both cases. The binding of V(IV)O(2+) to transferrin (hTF) in the presence of mhcpe involves mainly (V(IV)O)1(hTF)(mhcpe)1, (V(IV)O)2(hTF)(mhcpe)1 and (V(IV)O)2(hTF)(mhcpe)2 species, bound at the Fe(III) binding sites, and the corresponding conditional formation constants are determined. Under the conditions expected to prevail in human blood serum, CD data indicate that the V(IV)O-mhcpe complexes mainly bind to hTF; the formation of V(IV)O-hTF-mhcpe complexes occurs in the presence of Fe(III) as well, distinct EPR signals being clearly obtained for Fe(III)-hTF and to V(IV)O-hTF-mhcpe species. Thus this study indicates that transferrin plays the major role in the transport of V(IV)O-mhcpe complexes under blood plasma conditions in the form of ternary V(IV)-ligand-protein complexes.

Second harmonic generation of η5-monocyclopentadienyl ruthenium p-benzonitrile derivatives by Kurtz powder technique. Crystal and molecular structure determinations of [Ru(η5-C5H5)((+)-DIOP)(p-NCC6H4NO2)][X], X=PF6−, CF3SO3− and [Ru(η5-C5H5)((+)-DIOP)(NCCH3)][PF6]

Abstract A new series of salts [RuCp(PP)( p -NC(CHCH) n C 6 H 4 R)][X] (PP=((+)-DIOP, DPPE; n =0, 1; R=CH 3 , Br, OCH 3 , NH 2 , N(CH 3 ) 2 , C 6 H 5 and NO 2 ; X=PF 6 − , CF 3 SO 3 − ) were synthesised and the second harmonic generation (SHG) efficiencies were measured by Kurtz powder technique in order to better understand the relationship between structural features and solid state packing with SHG properties. A structural study of [RuCp((+)-DIOP)( p -NCC 6 H 4 NO 2 )][X], X=PF 6 − , CF 3 SO 3 − by X-ray diffraction showed crystallisation on accentric groups. The PF 6 − salt crystallised in a triclinic space group P 1 showing perfect parallel alignment of the molecular dipoles. The CF 3 SO 3 − salt crystallised in a monoclinic space group P 2 1 and shows an angle of 73.8° between the molecular dipoles in the unit cell. Complex [RuCp((+)-DIOP)( p -NCCH 3 )][PF 6 ], studied for comparison, crystallises in the C 222 1 space group and shows eight molecules per unit cell randomly orientated. Comparison of the RuN and NC distances between the three compounds are in agreement with metal–nitrile bonding suggested by the spectroscopic data.

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).

High first hyperpolarizability and perfectly aligned crystal packing for an organometallic compound [Fe(η5-C5H5)((R)–PROPHOS)(p-NCC6H4NO2)][PF6]·CH2Cl2

Abstract The molecular first hyperpolarizability, β, and the X-ray crystal structure of the complex [Fe(η5-C5H5)((R)–PROPHOS)(p-NCC6H4NO2)][PF6] ((R)–PROPHOS=(R)–(+)-bis-(1,2-diphenylphosphino)propane) were determined. A near-resonant enhanced β value as high as 545×10−30 esu was obtained from hyper-Rayleigh scattering measurements. In addition, the compound crystallizes in the space group P1 with a perfect alignment of the dipolar molecules (only a single chromophore per unit cell), thus maximizing the macroscopic nonlinearity for electro-optic or parametric frequency conversion applications. The molecular packing in the crystal is analyzed in order to understand the factors leading to the perfect alignment.

Design and characterization of organic and organometallic molecules for second order nonlinear optics

Publisher Summary This chapter focuses on how to design, characterize, and optimize the first hyperpolarizability β of organic and organometallic molecules for nonlinear optics (NLO) applications. The chapter also presents NLO effects and examines the relation between molecular and macroscopic NLO properties. The theoretical methods which have been employed to calculate these properties are discussed. The chapter presents a description of methods for the experimental determination of molecular second-order (SO) NLO parameters with emphasis on the recently widely used hyper-Rayleigh scattering (HRS) technique. The different types of compounds which have been synthesized and characterized for SO NLO are discussed for organic and organometallic molecules, respectively, up to the recent developments in this field. A number of criteria which these compounds have to meet for applications and some materials aspects are also considered in the chapter.

Amplification of the linear and nonlinear optical response of a chiral molecular crystal

We have observed large second-order nonlinear optical and vibrational circular dichroism (VCD) responses in a charge-transfer-type L-Histidinium salt. Using X-ray Diffraction, VCD spectroscopy, and time-dependent density functional theory to characterize the compound, we employ a two-level model to explain and quantify the strongly enhanced optical signals. We find that both linear and nonlinear optical responses are greatly enhanced by a single low-lying charge-transfer state.