J.G. Małecki

Synthesis, molecular, crystal and electronic structure of [ RuCl 2 ( PPh 3 ) 2 ( C 3 N 2 H 4 ) 2 ]

The reaction of ½RuCl2ðPPh3Þ3� complex with pyrazole has been examined. A new ruthenium complex – ½RuCl2 ðPPh3Þ2ðC3N2H4Þ2� has been obtained and characterised by IR and UV–Vis measurements. Crystal and molecular structure of the complex has been determined. 2003 Elsevier Science B.V. All rights reserved.

Ruthenium(II) complexes containing a phosphine-functionalized thiosemicarbazone ligand: synthesis, structures and catalytic C–N bond formation reactions via N-alkylation

A series of ruthenium(II) complexes incorporating a thiosemicarbazone chelate tethered with a diphenylphosphine pendant have been studied. Thus, [(PNS-Et)RuCl(CO)(PPh3)] (1), [N,S-(PNS-Et)RuH(CO)(PPh3)2] (2) and [(PNS-Et)RuCl(PPh3)] (3) were synthesized by reactions of various RuII precursors with 2-(2-(diphenylphosphino)benzylidene)-N-ethylthiosemicarbazone (PNS-Et). However, complexation of PNS-Et with an equimolar amount of [RuCl2(dmso)4] resulted in two different entities [(PNS-Et)RuCl(dmso)2] (4) and [(PNS-Et)2Ru] (5) with different structural features in a single reaction. All the RuII complexes have been characterized by analytical and various spectroscopic techniques. Compounds 1–5 were recrystallized, and the X-ray crystal structures have been reported for 1, 2 and 5. In the complexes 1 and 3–5 the ligand coordinated in a tridentate monobasic fashion by forming PNS five- and six-membered rings, whereas in 2, the ligand coordinated in a bidentate monobasic fashion by forming a strained NS four-membered ring. Furthermore, compounds 1–5 showed catalytic activity in N-alkylation of heteroaromatic amines. Notably, complexes 1–3 were found to be very efficient catalysts toward N-alkylation of a wide range of heterocyclic amines with alcohols. In the presence of a catalytic amount of 2 with 50 mol% of KOH, N1,C5-dialkylation of 4-phenylthiazol-2-amine has been investigated. Reaction of in situ generated aldehyde with amine yields the N1,C5-dialkylated products through the hydride ion transformation from alcohol. Complexes 1–3 also catalyzed a variety of coupling reactions of benzyl alcohols and sulfonamides, which were realized often with 99% isolated yields. Advantageously, only one equivalent of the primary alcohol was consumed in the process.

Half-sandwich ruthenium(II) complexes with N- and N,(N,O)- donor ligands: molecular, electronic structures, and computational study

Four η6-p-cymene ruthenium(II) complexes with 2-(2-aminophenyl)-1H-benzimidazole (BImPhNH), 2-aminobenzimidazole (BImNH), 2-aminobenzothiazole (BTzNH), and 2-(2-hydroxyphenyl)benzoxazole (HBO) ligands have been prepared and studied by IR, 1H-NMR, UV–Vis spectroscopy, and X-ray crystallography; its luminescent properties were examined. The experimental studies on the complexes have been accompanied computationally by the density functional theory (DFT) calculations.

Exploring the Anti-Cancer Activity of Novel Thiosemicarbazones Generated through the Combination of Retro-Fragments: Dissection of Critical Structure-Activity Relationships

Thiosemicarbazones (TSCs) are an interesting class of ligands that show a diverse range of biological activity, including anti-fungal, anti-viral and anti-cancer effects. Our previous studies have demonstrated the potent in vivo anti-tumor activity of novel TSCs and their ability to overcome resistance to clinically used chemotherapeutics. In the current study, 35 novel TSCs of 6 different classes were designed using a combination of retro-fragments that appear in other TSCs. Additionally, di-substitution at the terminal N4 atom, which was previously identified to be critical for potent anti-cancer activity, was preserved through the incorporation of an N4-based piperazine or morpholine ring. The anti-proliferative activity of the novel TSCs were examined in a variety of cancer and normal cell-types. In particular, compounds 1d and 3c demonstrated the greatest promise as anti-cancer agents with potent and selective anti-proliferative activity. Structure-activity relationship studies revealed that the chelators that utilized “soft” donor atoms, such as nitrogen and sulfur, resulted in potent anti-cancer activity. Indeed, the N,N,S donor atom set was crucial for the formation of redox active iron complexes that were able to mediate the oxidation of ascorbate. This further highlights the important role of reactive oxygen species generation in mediating potent anti-cancer activity. Significantly, this study identified the potent and selective anti-cancer activity of 1d and 3c that warrants further examination.

A ruthenium(II) hydride carbonyl complex with 4-phenylpyrimidine as co-ligand

The reaction of [RuHCl(CO)(PPh3)3] with 4-phenylpyrimidine gave a new ruthenium(II) complex, namely [RuHCl(CO)(PPh3)2(pyrim-4-Ph)]. The complex has been studied by IR and UV–vis spectroscopy and by X-ray crystallography. The molecular orbitals of the complex have been calculated by density functional theory. The spin-allowed singlet–singlet electronic transitions of the complex have been calculated by time-dependent DFT, and the UV–vis spectrum of the compound has been discussed on this basis. The emission properties of the complex were also studied.

Radiation induced conversion of N2 to amines in the presence of [WH4(dppe)2] and [WH5(dppe)2]+ in solution

Abstract The complexes [WH4(dppe)2] and [WH5(dppe)2][HSO4] were applied in the fixation and reduction of molecular nitrogen in a γ-radiation field. The mechanism of the process involving the reactions with the solvent molecules was presented. Dependences of the yields of the amines formed on the dose and concentrations of the catalyst were shown.

Copper-d-penicillamine complex as potential contrast agent for MRI

In vitro and in vivo proton T1 data are reported that demonstrate that the paramagnetic copper-D-penicillamine complex can be applied as a potential contrast agent to magnetic resonance imaging.

Radiation-catalytic reduction of molecular nitrogen with application of the tungsten(IV) hydride complexes

Abstract A radiation-catalytic experiment of the fixation and reduction of molecular nitrogen has been carried out. The [WH 4 (dtpe) 2 ] complex was applied to fix molecular nitrogen in a γ-radiation field. Plots of the dependence of either the number of molecules of ammonia or hydrazine vs dose are presented. A mechanism for the radiation-catalytic fixation and reduction of molecular nitrogen using the [WH 4 (dtpe) 2 ] complex is suggested. The unusually high radiation yields of ammonia and hydrazine are explained as due to a cyclic process.

Nickel(II) and copper(II) complexes constructed with N2S2 hybrid benzamidine–thiosemicarbazone ligand: synthesis, X-ray crystal structure, DFT, kinetico-catalytic and in vitro biological applications

With the aim of assessing whether transition metal complexes might be utilized as efficient biocatalysts and biological drugs, new monofunctional nickel(II) and copper(II) complexes of types NiL (1) and CuL (2) [H2L = N-(N′,N′-diethylaminothiocarbonyl)benzimidoyl chloride-2-aminoacetophenone-N-methylthiosemicarbazone] were synthesized. The compounds are remarkably stable and were obtained in good yields. Structural elucidation was carried out thoroughly in solid and solution-states by elemental analysis and various spectroscopy techniques (IR, UV-vis, 1H NMR, and EPR) as well as ESI mass spectrometry. The molecular structure of the compounds was investigated by single-crystal X-ray diffraction. The analyses showed tetradentate coordination of the ligand in nickel(II) and copper(II) complexes, in which the metal atom exhibits a square planar geometry with N2S2 in a donor fashion. Structural optimization, HOMO–LUMO energy calculations and Natural Bond Orbital (NBO) analysis of H2L and its complexes (1 and 2) were investigated by Density Functional Theory (DFT). The trend in binding affinities of the compounds with biomolecules, such as calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) protein, were investigated by different spectrophotometric methods, which revealed an intercalative mode of interaction. Furthermore, enzyme kinetic studies reflected that the square planar complexes (1 and 2) are also effective in mimicking catecholase (3,5-DTBC) and phosphatase (4-NPP) activities over the parent H2L. The high kcat values suggested that the selected compounds displayed a high rate of catalytic efficiency. In vitro cytotoxicity of the complexes on human skin cancer melanoma (A375), human cervical cancer (HeLa) and human hepatocellular carcinoma (Hep3B) cancer cell lines demonstrated that the complexes had a broad-spectrum of anti-cancer activity with low IC50 values. The morphological assessment data obtained by acridine orange/ethidium bromide (AO/EB) and diamidino-2-phenylindole (DAPI) staining revealed that complex 2 induces apoptosis much more effectively than 1.

Chloride and pseudohalide hydride-carbonyl ruthenium(II) complexes with 4-pyrrolidinopyridine as co-ligand

Chloride and pseudohalide (N3−, NCS−) hydride-carbonyl ruthenium(II) complexes with 4-pyrrolidinopyridine as co-ligand were synthesized and characterized by IR, 1H, and 31P NMR, electronic absorption and emission spectroscopy and X-ray crystallography. The electronic structures of the complexes were calculated by density functional theory (DFT) on their crystal structures. The spin-allowed singlet–singlet electronic transitions of the complexes were calculated by time-dependent DFT, and the UV–Vis spectra have been discussed on these basis. The emission properties of the complexes were also studied.