Mononuclear, oligonuclear and polynuclear metal coordination compounds with 1,2,4-triazole derivatives as ligands

Complexes of heterocyclic thione donors

The secular determinants obtained in the previous paper are solved for the energy levels which are important in the absorption spectra of the normal complex ions, leaving the crystalline field strength as a parameter. The values of B and C (Racah's parameters) there needed are determined from the observed spectra of free ions or in some cases by extrapolation. The f -values of the transitions which connect the energy levels calculated are estimated and compared with the observed intensities. The difference of the spectral width among absorption bands and lines is also considered using the energy diagram obtained. Following the assignments determined by the above considerations, the calculated positions of lines and bands are rather in good agreement with the experimental data in divalent ions [MX 6 ] 2+ (M=Cr, Mn, Fe, Co, Ni), when we adjust the crystalline field parameter D q suitably. In trivalent ions [MX 6 ] 3+ (M=Ti, V, Cr, Mn, Fe), it is necessary besides the adjustment of D q to use smaller values ...

On the absorption spectra of complex ions. II

Coordination compounds of copper, nickel and iron with Schiff bases derived from hydroxynaphthaldehydes and salicylaldehydes

At present, cisplatin (cis-diamminodichloroplatinum(II)) is one of the most largely employed anticancer drugs as it is effective in the treatment of 70-90% of testicular and, in combination with other drugs, of ovarian, small cell lung, bladder, brain, and breast tumors. Anyway, despite its high effectiveness, it exhibits some clinical problems related to its use in the curative therapy, such as a severe normal tissue toxicity (in particular, nephrotoxicity) and the frequent occurrence of initial and acquired resistance to the treatment. To obtain compounds with superior chemotherapeutic index in terms of increased bioavailability, higher cytotoxicity, and lower side effects than cisplatin, we report here on some gold(I) and gold(III) complexes with dithiocarbamate ligands (DMDT = N,N-dimethyldithiocarbamate; DMDTM = S-methyl-N,N-dimethyldithiocarbamate; ESDT = ethylsarcosinedithiocarbamate), which have been synthesized, purified, and characterized by means of elemental analyses, conductivity measurements, mono- and bidimensional NMR, FT-IR, and UV-vis spectroscopy, and thermal analyses. Moreover, the electrochemical properties of the designed compounds have been studied through cyclic voltammetry. All the synthesized gold complexes have been tested for their in vitro cytotoxic activity. Remarkably, most of them, in particular gold(III) derivatives of N,N-dimethyldithiocarbamate and ethylsarcosinedithiocarbamate, have been proved to be much more cytotoxic in vitro than cisplatin, with IC50 values about 1- to 4-fold lower than that of the reference drug, even toward human tumor cell lines intrinsically resistant to cisplatin itself. Moreover, they appeared to be much more cytotoxic also on the cisplatin-resistant cell lines, with activity levels comparable to those on the corresponding cisplatin-sensitive cell lines, ruling out the occurrence of cross-resistance phenomena and supporting the hypothesis of a different antitumor activity mechanism of action.

Gold dithiocarbamate derivatives as potential antineoplastic agents: design, spectroscopic properties, and in vitro antitumor activity.

The complexing behaviour towards palladium(II) and platinum(II) halides of some 1,4-benzodiazepines is reported. The ligands used in this study are 7-chloro-2-methylamino-5-phenyl-3H-1,4-benzodiazepin-4-oxide, 1,3-dihydro-7-nitro-5-phenyl-2H-1,4-benzodiazepin-2-one and 7-chloro-1-methyl-5-phenyl-3H-1,4-benzodiazepin-2-one. The complexes have been studied by means of magnetic susceptibility measurements, infrared and far infrared spectra, electronic spectra and conductivity measurements. The most convincing structural evidence for these complexes is a square planar stereochemistry with bridging ligands joining two metal ions and terminal halides in the 1:1 complexes and terminal ligands and terminal halides in the 1:2 derivatives. Assignments for the metal-ligand and metal-halide bands have also been made.

A novel series of palladium(ii) and platinum(ii) complexes with 1,4-benzodiazepines as ligands

Isotopic infrared study of some nickel(II) and copper(II) complexes containing heterocyclic dithiocarbamate ligands

The preparation of some complexes of N,N′-bis(phenylaminomethyl)parabanic acid with halides of cobalt(II), nickel(II), and copper(II) is reported. The complexes of the type MLX2 seem to have pseudo-tetrahedral and pseudo-octahedral symmetry. The complexes have been studied by means of magnetic susceptibility measurements, infrared and far infrared spectra, electronic and nmr spectra, and conductivity measurements. The ligand behaves as bidentate N-bonded. The various ligand field parameters, Dq, B', and β have been evaluated. The B' values suggest a strong covalency in the metal–ligand σ bond and Dq values show a medium strong ligand field. The presence of metal–nitrogen bonds is suggested. The possible stereochemistries of the complexes are discussed in the light of the experimental results.

N,N′-Bis(phenylaminomethyl)parabanic add as a complexing agent. Complexes of some bivalent first row transition metals

Some benzoxazole-2-thione (bot) complexes of manganese(II), iron(III), iron(II), ruthenium(III) and osmium(III) have been prepared and their conductivities, electronic spectra, magnetic susceptibility data and i.r. spectra are reported and discussed. The metal–halogen stretching modes in the far i.r. region resulted particularly useful in distinguishing between the mer- and fac-isomers in the ruthenium and osmium compounds of the type ML3 X3. From the magnetic properties it was concluded that the above ligand forms low-spin complexes with ruthenium(III) and osmium(III) and high-spin complexes with manganese(II), iron(II) and iron(III). The wavelengths of the principal absorption peaks have been accounted for quantitatively in terms of the crystal field theory for manganese(II), tetrahedral iron(III), ruthenium(III) and osmium(III) derivatives. The values of B and C in the iron(III) derivatives are less than in the corresponding manganese(II) complexes. The charge-transfer observed in the rutheniu...

The coordinating behaviour of benzoxazole-2-thione towards some transition metal halides in the light of spectroscopic investigations

Dosage par conductimetrie de l'acide oxalique, l'acide malonique, l'acide succinique, l'acide citrique et l'acide phtalique dans le methoxy-2 ethanol et l'ethanediol-1,2 en utilisant la diphenyl-1,3 guanidine comme titrant

Carlo Preti

Papers

A novel series of palladium(ii) and platinum(ii) complexes with 1,4-benzodiazepines as ligands

Isotopic infrared study of some nickel(II) and copper(II) complexes containing heterocyclic dithiocarbamate ligands

N,N′-Bis(phenylaminomethyl)parabanic add as a complexing agent. Complexes of some bivalent first row transition metals

The coordinating behaviour of benzoxazole-2-thione towards some transition metal halides in the light of spectroscopic investigations

Conductometric titrations of polyprotic acids in nonaqueous mixed solvents. Effects of temperature and composition of the solvent mixture