Umberto Russo

Heteropolymetallic complexes of 1,1′-Bis(diphenylphosphino)ferrocene (dppf). III. Comparative physicochemical properties of (dppf)MCl2 (M = Co, Ni, Pd, Pt, Zn, Cd, Hg)

Abstract 1,1′-Bis(diphenylphosphino)ferrocene (dppf) metal dichlorides (metal = Co, Ni, Pd, Pt, Zn, Cd, and Hg) are examined as a class of related complexes. Their electronic, infrared, mass, 31P NMR, and Mossbauer spectra as well as the HeI and HeII photoelectron spectra of dppf are presented and discussed. Cyclovoltammetric tests in dichloroethane indicate that the ferrocene moiety undergoes a strong stabilization towards oxidation, and the ferricinium derivatives are well characterized in the case of Pd(II) and Pt(II). Differential scanning calorimetric tests reveal that all the complexes are thermally very stable, particularly the Zn(II) and Cd(II) derivatives, which melt without previous decomposition in the temperature range 300–305 °C. Cyclovoltammetric and field desorption mass spectral tests reveal that the [(dppf)MCl2]+ species are stable only when M = Pd, Pt.

Hydrogen deficiency in Ti-rich biotite from anatectic metapelites (El Joyazo, SE Spain): Crystal-chemical aspects and implications for high-temperature petrogenesis

Abstract Titanium-rich biotites from graphite-bearing metapelitic xenoliths, equilibrated at ca. 850 °C and 7 kbar in the presence of a granitic melt, have been studied through complete chemical analysis and single-crystal XRD refinements. The chemical study combines EMP analyses, hydrogen determination by both SIMS and C-H-N elemental analysis, and Mössbauer spectroscopy. Biotites in the analyzed xenoliths have TiO2 contents ranging from 4.5 to 4.9 wt% and an XFe of 0.67. Their F and Cl contents are negligible, and Fe3+/Fetot ranges from 10 to 16%. The H2O content of the biotites ranges from 2.4 to 2.8 wt%, and a small fraction of H is accommodated in the lattice as NH4. Based on these full chemical analyses, the calculated OH occupancy is 1.26 to 1.30 groups per formula unit, more than one third less than the stoichiometric value. The entrance of Ti in the octahedral site of biotite is consistent with the Ti-oxy exchange, whereas Ti-Tschermak or Ti-vacancy substitutions play a very minor role. The Fe3+-oxy exchange cannot account for the observed OH deficiency. From single-crystal XRD, biotites belong to the 1M polytype and contain variable amounts of stacking faults. The c cell parameter, K-O4 and outer distances provide an independent estimate of the OH content, which agrees with SIMS determinations. The linear relationship between VITi4+ and the bond-length distortion of the cis-M2 octahedron reveals the partitioning of Ti4+ in M2, and the Ti4+ off-center shift toward O4 supports the occurrence of the Ti-oxy exchange. The ordering of Ti4+ over two non-equivalent M2 sites, which would be favored energetically, is in agreement with the evidence for a third octahedral site suggested by Mössbauer spectroscopy. The biotite dehydrogenation combined with the partitioning of Ti4+ in M2 and the low thermal expansion of Ti4+- containing octahedra, are the keys to understanding the thermal stabilization of Ti substitution in biotites.

Adducts of organotin(IV), tin(IV) and tin(II) halides with 1-methyl-imidazoline-2(3H)-thione (Hmimt) and imidazoline-2(1,3H)-thione (Himt). Synthesis, spectroscopic (IR, Mössbauer and 1H, 13C, 119Sn NMR) studies and in vitro antitumour activity

Abstract The reactions of 1-methyl-imidazoline-2(3 H )-thione (Hmimt) and imidazoline-2(1,3 H )-thione (Himt) with organotin(IV), tin(IV) and tin(II) halides were studied. Ten novel adducts were prepared and characterised by elemental analysis, conductivity measurements, IR, far-IR, 1 H NMR, 13 C NMR, 119 Sn NMR and Mossbauer spectroscopy. The ligands behave as monodentate and exhibit sulfur coordination. The structure of the complexes, in the solid state, is discussed in terms of the Mossbauer quadrupole splitting and the tin-ligand stretching vibrations in the IR and far-IR spectra. The behaviour of the adducts upon dissolution to D 2 O and CDCl 3 is also discussed. Octahedral dimeric and monomeric stereochemistries are assigned for organotin(IV) and tin(IV) adducts in the solid state. The in vitro antitumour activity against six human cell lines, MCF-7, EVSA (two breast cancers), WiDr (a colon cancer), IGROV (an ovarian cancer), M19MEL (a melanoma) and A498 (a renal cancer) for the adducts [SnBuCl 3 (Hmimt)] 2 , [SnMeCl 3 (Himt)] 2 and SnMe 2 Cl 2 (Himt) 2 is reported.

Cation Distribution in Some Natural Spinels from X-ray Diffraction and Mössbauer Spectroscopy

Abstract Three natural spinels of different places of occurrence and compositions were investigated by means of microprobe chemical analysis, single crystal X-ray diffraction and Mössbauer spectroscopy. All cation distributions between T and M sites were calculated from microprobe and XRD experimental data, by means of a mathematical model with appropriate assumptions. Fe2+ and Fe3+ assignments calculated in this way were compared with those observed in Mössbauer spectra. The satisfactory agreement found proves, at least in the samples studied, the reliability of the model and the assumptions used. In the spinels examined, such results show Fe2+ and Fe3+ virtually ordered in T and M sites respectively. Mössbauer data also revealed Fe2+ in different tetrahedral sites due to the next-nearest neighbour effect, probably as a consequence of spinel genetic conditions.

Diorganotin(IV) derivatives of salicylaldehydethiosemicarbazone. The crystal structure of dimethyl- and diphenyl- (salicylaldehydethiosemicarbazonato)tin(IV)

Abstract The title compounds have been prepared by reacting the corresponding diorganotin(IV) oxide with salicylaldehyde thiosemicarbazone (H2L). [SnMe2(L)] crystallizes in the monoclinic space group P21/n with a=9.480(3), b=13.532(7), c=10.541(3) A, β=100.33(2)° and Z=4 (R=0.0230, R′=0.0258). [SnPh2(L)] crystallizes in the space group P21/a with a=13.483(8), b=10.078(1), c=15.622(4) A, β=113.66(4)° and Z=4 (R=0.030, R′=0.031). Both complexes consist of molecules in which the bisdeprotonated ligand is O,N,S-bonded and the tin atom exhibits distorted pentacoordination, with small differences between the methyl and phenyl derivatives in bond distances, bond angles and intermolecular hydrogen bonds. The spectral properties of the complexes (IR, Mossbauer and 1H, 13C and 119Sn NMR spectra) are discussed in the light of this structural information.

Organotin meclofenamic complexes: Synthesis, crystal structures and antiproliferative activity of the first complexes of meclofenamic acid - novel anti-tuberculosis agents.

The complexes [Me(2)(Meclo)SnOSn(Meclo)Me(2)](2) (2) and [Ph(3)Sn(Meclo)] (3) where HMeclo is meclofenamic acid, N-(2,6-dichloro-m-tolylanthranilic acid)], have been prepared and structurally characterized by means of vibrational, (1)H and (13)C NMR spectroscopies. The crystal structure of complexes (2) and (3) have been determined by X-ray crystallography. Three distannoxane rings are present to the dimeric tetraorganodistannoxane of planar ladder arrangement of (2). The structure is centro symmetric and features a central rhombus Sn(2)O(2) unit two additional tin atoms linked at the oxygen atoms. Five- and six-coordinated tin centers are present in the dimer distannoxane. X-ray analysis of (3) revealed a penta-coordinated structure containing Ph(3)Sn coordinated to the chelated carboxylato group. The polar imino hydrogen atom participates in intra-molecular hydrogen bonds. Complexes (2) and (3) are self-assembled via pi-->pi, C-H-pi, stacking interactions and intra-molecular hydrogen bonds. Meclofenamic acid and [Ph(3)Sn(Meclo)] have been evaluated for antiproliferative activity in vitro against three human cancer cell lines: MCF-7 (human breast cancer cell line), T24 (bladder cancer cell line), A-549 (non-small cell lung carcinoma) and a mouse L-929 (a fibroblast-like cell line cloned from strain L). The [Ph(3)Sn(Meclo)] complex exhibited high cytotoxic activity against all the cancer cell lines. Meclofenamic and [Ph(3)Sn(Meclo)] were tested for anti-mycobacterial activity against Mycobacterium tuberculosis H37Rv. The [Ph(3)Sn(Meclo)] complex was found to be a promising anti-mycobacterial lead compound, displaying high activity against M. tuberculosis H37Rv.

Charge binding of rhodamine derivative to OH− stabilized nanomaghemite: Universal nanocarrier for construction of magnetofluorescent biosensors

Superparamagnetic nanoparticles (20-40 nm) of maghemite, γ-Fe(2)O(3), with well-defined stoichiometric structure, are synthesized by the borohydride reduction of ferric chloride at an elevated temperature (100°C) followed by thermal treatment of the reaction product. Prepared maghemite nanoparticles reveal excellent colloidal stability for a long time without the necessity for any additional surface modification. These colloidal features are due to surface stabilizing OH(-) groups, which act as charge barriers preventing a particle aggregation and enabling a reversible binding of various oppositely charged organic substances. Such binding with rhodamine B isothiocyanate results in the fluorescent magnetic nanocarrier providing, at the same time, a spacer arm for covalent immobilization of other biosubstances including enzymes. In this work, we exploit this general applicability of the developed nanocarrier for covalent immobilization of glucose oxidase. This is the first reported example of magnetically drivable fluorescent nanocatalyst. The immobilized enzyme creates a 3-5 nm thick layer on the nanoparticle surface as proved by high-resolution transmission electron microscopy. This layer corresponds to 10 enzyme molecules, which are bound to the nanoparticle surface as found by the fluorimetric determination of flavin adenine dinucleotide. The developed magnetic fluorescent nanocatalyst, showing a rate constant of 32.7s(-1) toward glucose oxidation, can be used as a biosensor in various biochemical, biotechnological, and food chemistry applications. The presence of the nanocatalyst can be simply monitored by its fluorescence; moreover, it can be easily separated from the solution by an external magnetic field and repeatedly used without a loss of catalytic efficiency.

Diorganotin(IV)-promoted deamination of amino acids by pyridoxal: SnR2+2 complexes of pyridoxal 5'-phosphate and of the Schiff base pyridoxal-pyridoxamine (PLPM), and antibacterial activities of PLPM and [SnR2(PLPM-2H)] (R = Me, Et, Bu, Ph)

Pyridoxal 5′-phosphate (PLP) and pyridoxal (PL) itself were reacted with diorganotin(IV) derivatives in the presence and absence of aminoacids. With PLP the complexes [SnR 2 (PLP-2H)] (R=Me, Et, Bu) were isolated and characterized by EI and FAB mass spectrometry and by IR, Raman and Mossbauer spectroscopy. Reaction mixtures containing PL, valine or glycine and SnR 2 (OAc) 2 (R=Me, Et) afforded complexes of the form [SnR 2 (PLPM-2H)], where PLPM is the Schiff base formed by condensation of PL and pyridoxamine (PM). PM was presumably formed by transamination between valine or glycine and PL. The PLPM complexes, and their butyl and phenyl analogues, were also synthesized directly by reacting SnR 2 O and PLPM, and were characterized by EI and FAB MS, by IR, Raman, Mossbauer and NMR spectroscopy, and in the case of the methyl and ethyl compounds by single-crystal X-ray diffractometry. Crystals of [SnMe 2 (PLPM-2H)]·H 2 O and [SnEt 2 (PLPM-2H)] consist of molecules in which the ligand is bound to the metal through the O atoms of the two deprotonated phenolic hydroxyl groups and the iminic N atom, and the metal exhibits distorted square pyramidal coordination. Both PLPM and its complexes show intense antibacterial activity against Pseudomonas aeruginosa (ATCC27853), but only the complexes exhibit significant activity against the other four bacterial strains assayed, Staphylococcus aureus , Bacillus subtilis , Escherichia coli and a carbapenem-resistant P. aeruginosa strain.

Synthesis and spectroscopic properties of diorganotin(IV) derivatives of 2,6-diacetylpyridine bis(thiosemicarbazone). Crystal structure of diphenyl{2,6-diacetylpyridine bis(thiosemicarbazonato)}tin(IV) bis(dimethylformamide) solvate

The reaction of the title ligand (H2DAPTSC) with SnR2O (R=Me, Ph) in DMF afforded the complexes [SnR2(DAPTSC)]. The phenyl derivative crystallizes as [SnPh2(DAPTSC)]·2DMF in the P21/n space group, with lattice constants: a=9.753(1), b=18.962(1), c=17.923(3) A, β=97.93(1), Z=4 and R=0.035. The molecular complex is pentagonal bipyramidal, with the five donor atoms of the ligand in the pentagonal plane and the two phenyl groups in the axial positions. A comparative study based on the spectral properties (IR, Mossbauer and 1H, 13C and 119Sn NMR spectroscopy) of the two complexes suggests a similar structure for [SnMe2(DAPTSC)].

DIORGANOTIN(IV) COMPLEXES OF PYRIDOXAL THIOSEMICARBAZONE : SYNTHESIS, SPECTROSCOPIC PROPERTIES AND BIOLOGICAL ACTIVITY

The complexes [SnR2(L)] (R = Me, Et, Bu, Ph; H2L = pyridoxal thiosemicarbazone) have been prepared and characterized. In the light of the spectral properties of the complexes in the solid state (IR, mass, Mössbauer) the bideprotonated thiosemicarbazonato anion is O(phenolic)-, N(3)-, S-bonded to the tin atom which probably has trigonal bipyramidal coordination with N(3) atom and R groups occupying equatorial positions. NMR ( 1H, 13C and 119Sn) data in CDCl3 or DMSO-d6 suggest that this coordinative picture remains in these solutions. The ethyl, butyl and phenyl derivatives suppress proliferation of Friend erithroleukaemia cells (FLC). Of the pyridoxal thiosemicarbazone complexes so far evaluated. [SnBu2(L)] and [SnPh2(L)] showed the lowest thresholds for inhibition of FLC proliferation. The effects of these compounds on DMSO-induced differentiation of FLC, DNA synthesis and reverse transcriptase were also assayed.