John R. Miller

Platinum(II) complexes with 2-acetyl pyridine thiosemicarbazone: Synthesis, crystal structure, spectral properties, antimicrobial and antitumour activity

An interesting series of new platinum complexes has been synthesized by the reaction of Na(2)PtCl(4) with 2-acetyl pyridine thiosemicarbazone, HAcTsc. The new complexes, [Pt(AcTsc)Cl], [Pt(HAcTsc)(2)]Cl(2) and [Pt(AcTsc)(2)], have been characterized by elemental analyses and spectroscopic studies. The crystal structure of the complex [Pt(AcTsc)Cl] has been solved by single-crystal X-ray diffraction. The anion of HAcTsc coordinates in a planar conformation to the central platinum(II) through the pyridyl N, azomethine N and thiolato S atoms. Double intermolecular hydrogen bonds (NH-Cl), pi-pi and weak Pt-Pt and Pt-pi contacts lead to aggregation and to a two-dimensional supramolecular assembly. The antibacterial and antifungal effect of the novel platinum(II) complexes and the related palladium(II) complexes, [Pd(AcTsc)Cl], [Pd(HAcTsc)(2)]Cl(2) and [Pd(AcTsc)(2)], were studied in vitro. The complexes were found to have a completely lethal effect on Gram+ bacteria, while the same complexes showed no bactericidal effect on Gram- bacteria. Additionally, the complexes [Pt(AcTsc)(2)] and [Pd(AcTsc)(2)] showed effective antifungal activity towards yeast. Among these compounds [33], the most effective in inducing antitumour and cytogenetic effects are the complexes [Pt(AcTsc)(2)] and [Pd(AcTsc)(2)] while the rest, display marginal cytogenetic and antitumour effects.

Palladium(II) and platinum(II) complexes of pyridine-2-carbaldehyde thiosemicarbazone with potential biological activity. Synthesis, structure and spectral properties. Extended network via hydrogen bond linkages of [Pd(PyTsc)Cl]

Abstract The reactions of Li2PdCl4 and Na2PtCl4 with pyridine-2-carbaldehyde thiosemicarbazone, HPyTsc, afforded the complexes [Pd(PyTsc)Cl], [Pd(PyTsc)2] and [Pt(PyTsc)Cl], [Pt(PyTsc)2]. The new complexes have been characterized by elemental analyses and spectroscopic studies. A crystal structure of [Pd(PyTsc)Cl] shows that the anion of PyTsc coordinates in a planar conformation to the central palladium(II) through the pyridyl N, azomethine N and thiolato S atoms. The planar molecules are linked into polymeric chains by N–H··N and N–H··S hydrogen bonding. The protonation constants of the ligand, Ka1 and Ka2, were determined by spectrophotometry and the logarithms of their values were found to be equal to 11.58±0.05 and 3.94±0.02 respectively. Correlation of the antitumor activity of these complexes to the structure and to reduction potential is reported. The compounds [Pt(PyTsc)2] and [Pd(PyTsc)2] were found to exhibit the higher in vivo antitumor activity and the lower cytotoxicity.

In vitro and in vivo antitumor activity of platinum(II) complexes with thiosemicarbazones derived from 2-formyl and 2-acetyl pyridine and containing ring incorporated at N(4)-position: Synthesis, spectroscopic study and crystal structure of platinum(II) complexes with thiosemicarbazones, potential anticancer agents

Reactions of thiosemicarbazones of 2-formyl and 2-acetyl pyridine and containing an azepane ring (hexamethyleneiminyl ring) incorporated at N(4)-position, HL(1) (1) and HL(2) (2) with platinum(II) afforded the complexes, [Pt(L(1))Cl] (3) and [Pt(L(2))Cl] (4). Characterization of the compounds was accomplished by means of elemental analysis and spectroscopic techniques NMR, UV-vis and IR spectroscopy. The single-crystal X-ray structure of complex [Pt(L(2))Cl] (4) shows that the ligand monoanion coordinates in a planar conformation to the metal via the pyridyl N atom, the imine-N atom, and thiolato S-atom. Compounds 1-4 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). Ligand 2 exhibited high activity as anticancer agent against all four cancer cell lines, while ligand 1 exhibited selectivity against MCF-7, L-929 cell lines and complex 4 against A-549, T-24 cancer cell lines. Also, the acute toxicity and antitumor activity were evaluated on leukemia P388-bearing mice. Complex 3 afforded five to six cures against leukemia P388. The in vivo results of the antitumor activity show the two platinum complexes as very effective chemotherapeutic antileukemic agents.

SILVER(I)-SILVER(I) INTERACTIONS IN THE TETRAMERIC SILVER THIOLATE PHOSPHINE COMPLEX AG4(SPH)4(PPH3)4

Reaction of arenethiolate anions with [Ag(PPh 3 ) 4 ] yields novel silver(1) thiolate phosphine complexes, which are very soluble in common solvents. The crystal structure of [{Ag(SPh)(PPh 3 )} 4 ] has been solved: C 90 H 80 Ag 4 P 4 S 4 , triclinic, space group P 1. a = 12.263(2) b = 13.124(2), c = 15.063(2)A, α=69.596(9), β = 81.074(11), γ=68.944(12)°, U = 2119.2(6)A 3 , Z = 1. The complex has a highly-distorted chair structure in the solid state, with short silver-silver contacts of 3.1300(3)A. [{Ag(SPh)(PPh 3 )} 4 ] is a rare example of a complex containing only non-chelating ligands showing indications of solid-state silver(1)-silver(1) interactions.

Structure of bis(2-acetylpyridine 3-hexamethyleneiminylthiosemicarbazonato) palladium II, a potential antitumor complex.

The crystal structure of the potential antitumor complex bis(2-acetyppyridine 3-hexamethyleneiminylthiosemicarbazonato)palladium(II) has been solved. The palladium(II) atom is in a square planar environment surrounded by two cis nitrogen atoms and two cis sulfur atoms. The ligands are not equivalent, one being tridentate with (N,N,S) donation, the other being monodentate using only the sulfur atom to coordinate to the metal. The tridentate ligand shows a Z, E, Z configuration while the monodentate ligand shows an E, E, Z. Intermolecular hydrogen bonds stabilize the structure, while the crystal packing is determined by Pd-C, Pd-pi, C-H-pi and pi-pi interactions.

Molecular materials for non-linear optics. Second harmonic generation and the crystal and molecular structure of the 4-nitrophenylimine of ferrocenecarboxaldehyde

Abstract Ferrocenyl derivatives of the form [(η-C 5 H 5 )Fe(η-C 5 H 4 )CHN-( p -C 6 H 4 X)], where XNO 2 , F, Br, were tested for second harmonic generation (s.h.g.). Only when XNO 2 was such activity observed. This was not large, however, at 1/3 times that of the urea standard. X-ray analysis confirms that the material is non-centrosymmetric, crystallizing in the space group P 2 1 2 1 2 1 . This dictates that despite being acentric the crystal arrangement essentially ensures a cancelling of the dipolar nature of the molecule. The residual s.h.g. must arise from intermolecular effects . This is only the second structural report of such a metallocene derivative to display s.h.g. The possible influence of the molecular shape of 1 and of related compounds is also discussed.

Complexes of functionalised phosphine ligands. Part 1. Complexes of FeIII, CoIII, NiII and ReV with tridentate Schiff bases having PNO, NNO and NNS donor sets. Crystal structures of 2-(Ph2PC6H4NCH)C6H4OH and [Co{2-(Ph2PC6H4CHN)C6H4O}2][PF6]

The Schiff bases 2-[Ph2P(CH2)nNCH]C6H4OH (n= 3, HL1 or 2 HL2), 2-(RCHN)C6H3(OH)X-4 (R = 2-Ph2PC6H4, X = H HL3; R = 2-C5H4N, X = H HL4; R = 2-C5H4N, X = Cl HL5) were synthesised from the appropriate amine and aldehyde. On deprotonation these all functioned as tridentate monoanionic ligands to give complexes [FeL2]+ and [CoL2]+ with FeIII and CoIII and neutral complexes of stoichiometry NiL2 with NiII. The iron complexes were examined by Mossbauer spectroscopy which indicated the presence of two iron sites in [FeL12]+ with a spin-state equilibrium dependent on both temperature and the counter ion. The complex [FeL32]+ showed a single iron site, again with a spin state dependent on counter ion and temperature. The crystal structures of HL3 and [CoL32]+ have been determined. The distortions in free HL3 predispose it for co-ordination in a fac geometry to the Co with cis-PPh2 groups, and the changes occurring on co-ordination are discussed in detail. Reaction of RCHO (R = 2-Ph2PC6H4 or 2-C5H4N) with 2-aminobenzenethiol gave stable thiazoles R[graphic omitted]-2 which did not ring open to give tridentate ligands even on reaction with base and/or metal ions.

Trinuclear Palladium(II) Complexes with 2-Hydroxy-4-methoxyacetophenone N4-Dimethylthiosemicarbazone: Synthesis, Spectral Studies and Crystal Structure of a Tripalladium Complex

The synthesis and spectral characterization of a new triangular, trinuclear palladium(II) complex with the dianion of 2-hydroxy-4-methoxyacetophenone N4-dimethylthiosemicarbazone, 4MeOAp4Me is reported. The X-ray crystal structure determination of [Pd(4MeOAp4Me2)]3·DMSO shows it to contain a chair-type hexagon of alternating Pd and S atoms which form a molecular bowl. The crystal structure of H24MeOAp4Me2 shows that it is the E isomer with respect to the imine bond of the thiosemicarbazone moiety.

Mössbauer and spectroscopic studies on substituted tetraphenylporphyrinato iron(III) complexes in aqueous solutions and the formation of the μ-oxo-bridged species

Electronic and 57Fe Mossbauer spectra are reported for two new water-soluble porphyrinato iron(III) complexes. Equilibrium constants for μ-oxo bishaem formation are calculated assuming two protons are released. Comparisons are made of the data with other porphyrinato iron(III) systems and it is shown that, in the absence of well-defined fifth ligands, the mononuclear species in acidic solution probably contain two axial water ligands. The μ-oxo bishaems do not contain water or hydroxide coordinated to iron but may hold water by hydrogen-bonding to the oxygen bridge or possibly by aquation of the porphyrin ligands. μ-Oxo bridge formation is controlled by the acid strength of the water coordinated to the iron in the mononuclear species, low pKa values assisting oxo-bridge formation. Such low pKa values are assisted by electron-attracting substituents on the porphyrin periphery. It is noted that this same property assists the stabilisation of iron(II) complexes. Steric inhibition of oxo-bridge formation requires large substituents, unsubstituted phenyl groups being apparently not large enough.

The cleavage of the NN bond of N,N-disubstituted hydrazines on rhenium. The preparation, reactions and x-ray crystal structures of [ReCl2(NH3)(NNCOC6H4-4-R)(PPh3)2] (R = H, OMe, NO2), [ReCl3(NNPh2)(PPh3)2], [ReCl2(N)(NNPh2)(PPH3)] and [ReCl(N)(Me2CNNCOPh)(PPh3)2] ☆

Abstract Reaction of the N,O-chelated complexes [ReCl2(N2COC6H4-4-R)(PPh3)2] (R = H, Me, NO2) with N,N- and certain N-substituted hydrazines gave the ammine complexes [ReCl2(NH3)(NNCOC6H4-4-R)(PPh3)2][R = H (1), R = Me (2), R = NO2 (3). The mechanism is believed to involve intermolecular homolytic cleavage of the NN bond. The x-ray structure of 1 revealed a pseudo-octahedral geometry with trans-phosphines. The ammine ligand is cis to the benzoyldiazenido group and the ammine hydrogens are hydrogen-bonded to the carbonyl oxygen. Reaction of [ReOCl3(PPh3)2] with excess Ph2NNH2 · HCl in ethanol gave both [ReCl3(NNPh2)(PPh3)2] (6) and [ReCl2(N)(NNPh2)(PPh3)] (7). In the presence of base the rhenium(VII) cation [ReCl2(NNPh2)2(PPh3)+ was formed. The geometry of 7 was shown by X-ray structural determination to be a distorted square-based pyramid, with the nitride in the apical position. Attempted derivatization of 7 led to NN bond cleavage and the generation of nitrido complexes. The nitrido complex [ReCl(N)(Me2CNNCOPh)(PPh3)2] (8) was unexpectedly formed in the reaction of [ReOCl3(PPh3)2] with Me2CNNHCOPh in ethanol in the presence of HCl. The X-ray crystal structure of 8 showed a pseudo-octahedral geometry with the nitride ligand trans to the oxygen of the N,O-chelated hydrazonato(1-) ligand. The possible mechanisms of NN bond cleavage are discussed.