Novel benzyl-substituted molybdocene anticancer drugs

From the reaction of 6-(p-methoxyphenyl) fulvene (1a), 6-(3,4-dimethoxyphenyl) fulvene (1b) and 6-(3,4,5-trimethoxyphenyl) fulvene (1c) with LiBEt₃H, lithiated cyclopentadienide intermediates (2a-c) were synthesised. These intermediates were then transmetallated to molybdocene using MoCl₄ (synthesized in situ) to yield the benzyl-substituted molybdocenes bis-[(p-methoxybenzyl)cyclopentadienyl] molybdenum (IV) dichloride (3a), bis-[(3,4-dimethoxybenzyl)cyclopentadienyl] molybdenum (IV) dichloride (3b), and bis-[(3,4,5-trimethoxybenzyl)cyclopentadienyl] molybdenum (IV) dichloride (3c). The molybdocene 3a was characterised by single crystal X-ray diffraction. All three molybdocenes had their cytotoxicity investigated through MTT based preliminary in vitro testing on the human renal cell line Caki-1 in order to determine their IC50 values and compare them with the corresponding titanocene and vanadocene dichloride derivatives. Molybdocenes 3b-c were found to have the same IC50 values of 290 μM, while 3a yielded a value of 84 μM, respectively     

Coordination compounds of Cd(II) with several bidentate-NN′ and tridentate-NN′N nitrogen donor ligands. Cd NMR studies of monomeric compounds containing nitrogen donor atoms

Reaction of CdCl₂ with N-alkylaminopyrazole ligands 1-[(2-ethylamino)ethyl]-3,5-dimethylpyrazole (deae), 1-[(2-(tert-butylamino)ethyl)]-3,5-dimethylpyrazole (deat), bis-[(3,5-dimethylpyrazolyl)methyl]ethylamine (bdmae), and bis-[(3,5-dimethylpyrazolyl)ethyl]ethylamine (ddae) in absolute ethanol yields [CdCl₂(NN′)] (NN′ = deae (1), deat (2)), [CdCl₂(bdmae)] (3), and [CdCl(ddae)]₂[CdCl₄] (4). The Cd(II) complexes have been characterised by elemental analyses, conductivity measurements, IR, ¹H, ¹³C{¹H} and ¹¹³Cd NMR spectroscopies, and X-ray diffraction methods. ¹H and ¹¹³Cd NMR experiments at variable temperature for 3 and 4 show that dynamic processes are taking place in solution. We report the measurements of ¹¹³Cd NMR chemical shift data for complexes 1-4 in solution. X-ray crystal structures for complexes 2 and 3 have been determined. The Cd(II) is coordinated to the deat ligand, in 2, by one nitrogen atom of the pyrazolyl group and one nitrogen atom of the amine. It finishes a tetrahedral geometry with two chlorine atoms. The bdmae ligand is linked to Cd(II), in 3, by two nitrogens atoms of the pyrazolyl groups and one amine nitrogen, along with two chlorine atoms, in a distorted trigonal bipyramidal geometry.     

Pseudo-halide derivatives of titanocene: synthesis and cytotoxicity studies

The well-known anticancer drug candidate bis-[(p-methoxybenzyl)cyclopentadienyl] titanium(IV) dichloride (Titanocene ) was reacted with sodium azide or potassium cyanate, thiocyanate or selenocyanate in order to give pseudo-halide analogues of Titanocene . and were characterised by single crystal X-ray diffraction, which confirmed the expected nitrogen binding of the cyanate and thiocyanate to the titanium centre. All four titanocenes had their cytotoxicity investigated through preliminary in vitro testing on the LLC-PK (pig kidney epithelial) cell line in an MTT based assay in order to determine their IC50 values. Titanocenes were found to have IC50 values of 24 (± 8) μM, 101 (± 14) μM, 54 (± 21) μM and 27 (± 4) μM respectively. All four titanocene derivatives show significant cytotoxicity improvement when compared to unsubstituted titanocene dichloride and and showed similiar cytotoxic behaviour to Titanocene in vitro.     

Cytotoxic studies of substituted titanocene and ansa-titanocene anticancer drugs

A variety of substituted titanocene and ansa-titanocene complexes have been synthesized and characterized using traditional methods. The cytotoxic activity of the different titanocene complexes was tested against tumour cell lines human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x and normal immunocompetent cells, peripheral blood mononuclear cells PBMC. Alkenyl substitution, either on the cyclopentadienyl ring or on the silicon-atom ansa-bridge of the titanocene compounds [Ti{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃{CMe₂CH₂CH₂CHCH₂})}Cl₂] (8), [Ti{Me(CH₂CH)Si(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (9) and [Ti(η⁵-C₅H₄{CMe₂CH₂CH₂CHCH₂})₂Cl₂] (12) showed higher cytotoxic activities (IC₅₀ values from 24 ± 3 to 151 ± 10 μM) relative to complexes bearing an additional alkenyl-substituted silyl substituent on the silicon bridge [Ti{Me{(CH₂CH)Me₂SiCH₂CH₂}Si(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (10) and [Ti{Me{(CH₂CH)₃SiCH₂CH₂}Si(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (11) which causes a dramatic decrease of the cytotoxicity (IC₅₀ values from 155 ± 9 to >200 μM). In addition, the synthesis of the analogous niobocene complex [Nb(η⁵-C₅H₄{CMe₂CH₂CH₂CH=CH₂})₂Cl₂] (13), is described. Structural studies based on DFT calculations of the most active complexes 8, 9 and 12 and the X-ray crystal structure of 13 are reported.     

Template synthesis of N2S and N3S chelates via alkylation of bis(2-aminoethanethiolato)Ni: sulfur- and nitrogen-centered alkylations

Alkylation of bis(2-aminoethanethiolato)nickel(II) (1) with alkylating agents containing pendant donor groups has been investigated. Reaction with 2-bromoethylamine is strictly sulfur-centered yielding (2-[(2-aminoethyl)thio]ethaneamine)nickel(II)bromide, [(DAES)₂Ni]Br₂ (2), which was isolated as a lilac solid. Addition of chloroacetamide yields the sulfur- and nitrogen-alkylated product (2-[(2-aminoethyl)thio]acetamide)nickel(II)chloride, (AETA)NiCl₂ (3a), as a green solid. Recrystallization from water/acetone yields 3a as single crystals along with single crystals of [(AETA)NiCl(OH₂)]Cl (3b). The strictly S-alkylated product (2-[(2-amino-2-oxoethyl)thio]acetamide)nickel(II)iodide, [(AOTA)₂Ni]I₂ (4), is obtained upon reaction of 1 with iodoacetamide. A pathway is proposed consistent with the observed leaving group effect on the site of alkylation. The X-ray structures of 3a, 3b, and 4 are reported and the hydrogen-bonding network is described.     

Structural comparison of alkylated derivatives of (bmmp-dmed)Ni and (bmmp-dmed)Zn

The sulfur-alkylation of the nickel (1) and zinc (2) complexes of the dithiolate N₂S₂ ligand N,N′-bis-2-methyl-mercaptopropyl-N,N′-dimethylethylenediamine, H₂(bmmp-dmed), have been investigated. Reactions with iodomethane yield [(Me-bmmp-dmed)Ni]PF₆ (3), [(Me₂-bmmp-dmed)NiI₂] (4), and [(Me₂-bmmp-dmed)ZnI]₂[ZnI₄] (5). Addition of iodoacetamide yields [(AA₂-bmmp-dmed)Ni]I₂ (6) and [(AA₂-bmmp-dmed)Zn]I₂ (7). Each of the metal-thioether products (3-7) have been characterized spectroscopically and by X-ray crystallography. Structural data is compared with that of the previously reported thiolato precursors 1 and 2. Sulfur-alkylation of 1 results in small relative changes in the nickel-sulfur bond distance, whereas for 2, the zinc-sulfur bond distance increases significantly, but is not cleaved. The difference between nickel and zinc is attributed to the release of a π*-bonding interaction between the metal and sulfur upon alkylation that compensates for the decreased σ-donor ability of the thioether in the case of nickel, but not for zinc.     

Preparation, spectroscopy, X-ray analysis, and water-solubility studies of the first bis-PTA (PTA = 1,3,5-triaza-7-phosphaadamantane) derivatives

The bis-phosphines, 1,1′-[1,2-phenylenebis(methylene)]bis-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1]decane dibromide (1), 1,1′-[1,3-arenebis(methylene)]bis-[3,5-diaza-1-azonia-7-phosphatricyclo [3.3.1.1]decane dibromide (arene = phenyl (2), tolyl (3), anisolyl (4)), and 1,1′-[1,4-phenylenebis(methylene)]bis-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1]decane dibromide (5) were prepared in over 90% yield by refluxing 1,2-bis(bromomethyl)benzene, 1,3-bis(bromomethyl)benzene, 1,3-bis(bromomethyl)-5-methyl-benzene, 1,3-bis(bromomethyl)-5-methoxy-benzene, and 1,4-bis(bromomethyl)benzene with 1,3,5-triaza-7-phosphaadamantane (PTA) in acetone or chloroform. Compounds 1-5 are the first phosphines reported that contain two PTA moieties. All five compounds were characterized by ESI-MS, elemental analysis, ¹H, ¹³C, and ³¹P NMR spectroscopy, while 3 and 4 were additionally analyzed via single crystal X-ray diffraction. The relative positions of the PTA units on the aromatic ring as well as the substituents of the ring had a pronounced effect on the water-solubilities of the systems. The ortho compound (1, 2000 mg/mL) was more than two orders of magnitude more soluble than the para compound (5, 12.5 mg/mL). The meta substituted phenyl (2) and tolyl (3) compounds had solubilities (810 mg/mL) that were more than triple that of PTA (235 mg/mL) while the anisolyl analog (4) was half as soluble (121 mg/mL).     

Synthesis, photophysical and photochemical properties of novel soluble tetra[4-(thiophen-3yl)-phenoxy]phthalocyaninato zinc(II) and Ti(IV)O complexes

The synthesis, photophysical and photochemical properties of zinc and oxo-titanium phthalocyanine derivatives 4-(tetra[4-(thiophen-3yl)-phenoxy]phthalocyaninato)zinc(II), (2); and 4-(tetra[4-(thiophen-3yl)-phenoxy]phthalocyaninato)oxo-titanium(IV), (3), are described for the first time. These peripherally substituted complexes (2 and 3) have been synthesized and characterized by elemental analysis, IR, ¹H NMR and electronic spectroscopy. The compounds (2 and 3) have good solubility in organic solvents such as CHCl₃, DCM, DMSO, DMF, THF and toluene and are not aggregated within a wide concentration range. General trends are described for singlet oxygen, photodegradation, fluorescence quantum yields, triplet quantum yields and triplet life times of these complexes in DMSO, DMF and THF. Compound 2 has higher fluorescence quantum yields, triplet quantum yields and triplet life times than 3, however, the former has lower singlet oxygen quantum yields and photodegradation quantum yields than the latter.     

X-ray structural characterization of some sterically bulky N-donor and N-alkyl Grignard reagents

[MgBr₂(thf)₃] (1) and [FisoMg(thf)Cl]₂ (2), (Fiso⁻ = [ArNC(H)NAr]⁻, ), [2-PyC(SiMe₃)₂Mg(thf)Cl]₂ (3), [2-PyC(SiMe₃)₂Mg(thf)Br]₂ (4), and [(2-PyC(SiMe₃)₂Mg(thf))₂(OEt)Cl] · Et₂O (5). (2-Py(SiMe₃)₂CH = 2-{bis-(trimethylsilyl)methyl}2-pyridine) were isolated as by-products from reactions involving organometallic species and magnesium or diethylmagnesium. All compounds were characterized by single crystal X-ray crystallography. Compounds (1) and (5) have trigonal bipyramidal magnesium centres, while compounds (2)-(4) have square pyramidal structures. Compound (1) is monomeric, while compounds (2)-(5) are dinuclear with magnesium centres bridged by two halides for (2)-(4), and a chloride and an ethoxy ligand in (5).     

A series of mononuclear Co(III) complexes using tridentate N,O-donor ligands: chemical properties and cytotoxicity activity

Continuing our interest in tridentate ligands to develop new prototypes of cobalt-based metallodrugs for combating cancer, modifications in the backbone of HL1, [(2-hydroxybenzyl)(2-(pyridil-2-yl)ethyl]amine) were proposed in order to modulate the redox potential of new Co(III) complexes. Three ligands with electron withdrawing groups were synthesized: HL2: [(2-hydroxy-5-nitrobenzyl)(2-(pyridil-2-yl)ethyl]amine); HL3: [(2-hydroxybenzyl)(2-(pyridil-2-yl)ethyl]imine) and HL4: [(2-hydroxy-5-nitrobenzyl)(2-(pyridil-2-yl)ethyl]imine). They were used to obtain the respective mononuclear complexes 2, 3 and 4, which are discussed compared to the previous reported complex 1 (obtained from HL1). The new complexes were characterized and studied by several techniques including X-ray crystallography, elemental and conductimetric analysis, IR, UV-vis and ¹H NMR spectroscopies, and electrochemistry. The substitutions of the group in the para position of the phenol (HL1 and HL2) and the imine instead of the amine (HL3 and HL4), promote anodic shifts in the complexes reduction potentials. The influence of these substitutions in the biological activities of the Co(III) complexes against the murine melanoma cell line (B16F10) was also evaluated. Little effect was observed on cellular viability decrease for all free ligands, however the coordination to Co(III) enhances their activities in the following range: 1 > 4 ≈ 2 > 3. The data suggest that no straight correlation can be addressed between the reduction potential of the Co(III) center and the cell viability.     

Copper and manganese complexes with C2-multitopic ligands. X-ray crystal structure of [Cu(N,N′-bis[(S)-prolyl]phenylenediamine)H2O]. Catalytic properties

Eight mononuclear complexes with multitopic C₂-symmetry ligands, [Cu(L)]ClO₄, [Mn(L)Cl(H₂O)]PF₆, (L=N,N′-bis[(S)-prolyl]phenylenediamine (1), N,N′-bis[(S)-N-benzylprolyl]phenylenediamine (2), N,N′-bis{[(S)-pyrrolidin-2-yl]methyl}phenylenediamine (3), N,N′-bis-{[(S)-N-benzyl-pyrrolidin-2-yl]methyl}phenylenediamine (4)) have been prepared and characterised by analytical (elemental analysis, and mass spectroscopy) and FT IR, NMR and electronic spectroscopies. The data show that the ligands are neutral and coordinate to the metal in a tetradentate manner. The N,N′-bis[(S)-prolyl]phenylenediamine ligand also appears as an anionic species, (LH-2), and the single crystal structure determination of the respective complex, [Cu(1)]H₂O, is reported. This new family of Cu-complexes catalyse the cyclopropanation of styrene with ethyl and t-butyl diazoacetate to afford cis/trans 2-phenylcyclopropan-1-carboxylates with good yields and selectivity against dimerisation and low ee (<10%). On the other hand, the manganese and copper complexes also catalyse the oxidation of organic sulfides to sulfoxides with high selectivity, and moderate to low enantioselectivity. If an excess of oxidant were used the reaction yields sulfone as only product with excellent yield.     

Structural variety and stereochemical features of bis(diphenylphosphinyl)[3]ferrocenophane gold(I) complexes

The P,N-[3]ferrocenophane ligand 3 forms a (κP-ligand)AuCl complex (5) upon treatment with (Me₂S)AuCl. The corresponding P,P-[3]ferrocenophane system 4 yields a binuclear (κP,κP-chelate ligand)(AuCl)₂ complex (6) when reacted with 2 equivalents of the (Me₂S)AuCl reagent. Complex 6 features an intramolecular aurophilic Au?Au interaction. Treatment of the P,P-[3]ferrocenophane 4 with 1.0 equiv. of (PPh₃)AuCl gives the tetra-coordinated mono-gold(I) complex (P,P-ligand)(PPh₃)AuCl (7), whereas the cationic [(P,P-ligand)₂Au]⁺[Cl⁻] system is obtained from 4 and 0.5 equivalents of (Me₂S)AuCl. The [(P,P-ligand)₂Au]⁺ system is obtained in different diastereoisomeric forms (8 and 9) depending on the stereochemistry of the pair of P,P-[3]ferrocenophane chelate ligand used. Examples of the complexes 5, 6, 7 and 8 were characterized by X-ray diffraction.     

Preparation, characterization, and catalytic properties of (triphenylphosphine)ruthenium complexes bearing N,O,N′-tridentate ligands

Preparation and characterization of (triphenylphosphine)ruthenium complexes bearing N,O,N′-tridentate ligands, [(L₁)RuCl(PPh₃)₂](BF₄) (L₁ = 2-[(2-pyridylmethoxy)methyl]pyridine), 1), [(L₂)RuCl(PPh₃)₂](BF₄) (L₂ = 8-(2-pyridylmethoxy)quinoline, 2) and [(L₃)RuCl₂(PPh₃)] (L₃ = 2-[(2-pyridylmethoxy)methyl]quinoline, 3) are described. Complexes 1-3 have been characterized by NMR and elemental analyses. Molecular structures of 2 and 3 have been determined by X-ray crystallography. Both compounds exhibit the octahedral geometry. L₂ adopts the facial configuration in 2 while L₃ is in a mer-arrangement in 3. Complexes 1-3 have proven to be able to catalyze the transfer hydrogenation of several ketones to alcohols in the presence of KOH and 2-propanol at refluxing, among which complex 3 was found to be the most active.     

Studies of rheniumtricarbonyl complexes of tripodal pyridyl-based ligands

The reaction of N-benzoyl and N-acetyl tris(pyridin-2-yl)methylamine 1b and 1c (LH = tpmbaH and tpmaaH) with [Re(CO)₅Br] has been investigated and shown to proceed via the initial formation of a cationic rheniumtricarbonyl complex [(LH)Re(CO)₃]Br in which coordination of the ligand occurs via the three pyridine rings. For tpmbaH 1b, but not tpmaaH 1c, this initial complex 2b readily undergoes the loss of HBr to give a neutral octahedral complex 4b [(L)Re(CO)₃] where coordination occurs via two of the pyridine rings and the deprotonated amide nitrogen. The ¹H NMR spectrum of the latter complex 4b is very unusual in that at room temperature the signals for the 3-H protons on the coordinated pyridine rings are not visible due to extreme broadening of these resonances. Comparison with the analogous complex 7 from N-benzoyl bis(pyridin-2-yl)methylamine 6b (bpmbaH) confirms that this is due to rotation of the uncoordinated pyridine ring. The structure of the cationic complex 3d [(LH)Re(CO)₃]Br formed from N-benzyl tris(pyridin-2-yl)methylamine 1d (bz-tpmaH) is also discussed. The crystal structures of complexes [(tpmba)Re(CO)₃] 4b, [(bz-tpmaH)Re(CO)₃]Br 3d and [(bpmba)Re(CO)₃] 7 have been determined. In all complexes the coordination geometry around Re is distorted octahedral with a fac-{Re(CO)₃}⁺ core.     

Syntheses, characterization and crystal structure of diorganotin and triorganotin heterocyclicdicarboxylates with monomeric, 2D network and 3D framework structures

A series of new diorganotin and triorganotin(IV) heterocyclicdicarboxylates [(ⁿBu₃Sn)₂(2,5-pdc)]_∞ (1), {[(2-FC₆H₄CH₂)₃Sn]₂(2,5-pdc)}_∞ (2), {[(2-ClC₆H₄CH₂)₃Sn]₂(2,5-pdc)}_∞ (3), {[(4-CNC₆H₄CH₂)₃Sn]₂(2,5-pdc)}_∞ (4), {[(4-ClC₆H₄CH₂)₃Sn]₂(2,5-pdc)}_∞ (5), [(Ph)₂Sn(2,6-pdc)(H₂O)]_∞ (6), {[ⁿBu₃Sn(2,6-pdc)SnⁿBu₃]₂(H₂O)₂} · C₂H₃N (7) and {[Ph₃Sn(2,3-pdz)SnPh₃]₂(H₂O)} (8) have been obtained by reactions of diorganotin(IV) and triorganotin (IV) oxide with 2,6 or 2,5-H₂pdc (pdc = pyridinedicarboxylate) or 2,3-H₂pdz (pdz = pyrazinedicarboxylate). Complexes 1-8 were characterized by elemental, IR and NMR spectra analyses. The crystal and molecular structures of compounds 1, 6, 7 and 8 have been determined by X-ray single crystal diffraction. Compound 1 has 2D network structures. Compound 6 has 1D polymeric chain and 3D framework supramolecular structures due to the coordinated water molecules. Compound 7 has a monomeric structure, but the supramolecular structures are network.     

Bimetallic complexes of porphyrinphenanthroline: Preparation and catalytic activities

Condensation of tetraphenylporphyrin-2,3-dione with 1,10-phenanthroline-5,6-diamine provided porphyrinphenanthroline (2) as the desired ligand. Metallation of the porphyrinic site of 2 with CoCl₂, NiCl₂, ZnCl₂ and CuCl₂ afforded the corresponding metal complexes [Co(2)] (8a), [Ni(2)] (8b), [Zn(2)] (8c) and [Cu(2)] (8d), respectively. Subsequent reactions of these metalloporphyrins with [(COD)PdCl₂] yielded the corresponding bimetallic complexes [Co/Pd (9a), Ni/Pd (9b), Zn/Pd (9c) and Cu/Pd (9d)] in high yields. The bimetallic complex 9e (Mg/Pd) was prepared directly by complexation of 2 with MgBr₂ and [(COD)PdCl₂]. All complexes were characterized by both spectroscopic and elemental analyses. In addition, crystal structure of 9c was determined to confirm its formulation. The use of these bimetallic complexes as pre-catalysts for Mizoroki-Heck coupling reaction has been examined.     

Synthesis and high ranked NLT properties of new sulfonamide-substituted indium phthalocyanines

The synthesis and characterization of three new indium phthalocyanines bearing eight N-alkyl- or N-arylsulfonamide groups is described. The new compounds are {2,3,9,10,16,17,23,24-octakis[4-(4-methoxyphenylaminosulfonyl]phenoxy]phthalocyaninato}indium(III) chloride (7), {2,3,9,10,16,17,23,24-octakis[4-diethylaminosulfonyl)phenoxy]phthalocyaninato}indium(III) chloride (8) and {2,3,9,10,16,17,23,24-octakis[4-didodecylaminosulfonyl)phenoxy]phthalocyaninato}indium(III) chloride (9), and were obtained in 23-49% yields. The precursors of phthalocyanines 7-9 are sulfonamide-substituted phthalonitriles that can be prepared by reacting 4,5-bis(4-chlorosulfonylphenoxy)phthalonitrile (3) with amines. The nonlinear transmission (NLT) of complexes 7-9 was determined at 532 nm using ns pulses. All three phthalocyanines behave as reverse saturable absorbers with increasing efficiency of optical limiting in the order 7 < 8 < 9. A comparative analysis of the NLT results is attempted in terms of the structural differences in 7-9.     

Cytotoxicity of new polyfluorinated 1,4-naphtoquinones with diverse substituents in the quinone moiety

Fluorinated derivatives of 1,4-naphthoquinones are highly potent inhibitors of Cdc25A and Cdc25B phosphatases and growth of tumor cells. Eight new derivatives of polyfluoro-1,4-naphthoquinone were synthesized and their cytotoxicity in human myeloma, human mammary adenocarcinoma, mouse fibroblasts and primary mouse fibroblast cells as well as their mutagenic and antioxidant properties in a Salmonella tester strain were studied. The efficiency of suppressing the growth of two lines of tumor cells decreased in the order: 2-(2-hydroxy-ethylamino)-3,5,6,7,8-pentafluoro-1,4-naphthoquinone (1), 2,3-dimethoxy-5,6,7,8-tetrafluoro-1,4-naphthoquinone (2), 2-[2-hydroxyethyl(methyl)amino]-3,5,6,7,8-pentafluoro-1,4-naphthoquinone (3), 2-morpholino-3,5,6,7,8-pentafluoro-1,4-naphthoquinone (4), 2-[bis-(2-hydroxyethyl)amino]-3,5,6,7,8-pentafluoro-1,4-naphthoquinone (5), 2-[(2-hydroxy)ethylsulfanyl)]-5,6,7,8-tetrafluoro-1,4-naphthoquinone (6), 2-methoxy-3,5,6,7,8-pentafluoro-1,4-naphthoquinone (7), and 1,4-dioxo-3-(1-pyridinio)-1,4-dihydro-5,6,7,8-tetrafluoronaphthalene-2-olate (8). Taking into account these data together with the better cytotoxic effect against cancer cells as compared with normal mammalian cells, protecting of bacterial cells from spontaneous and H₂O₂-dependent mutagenesis, and lower general toxicity of the compounds towards different cells, one can propose that compounds 3-5 may be considered as useful potential inhibitors of growth of tumor cells.     

Spectroscopic characterization of mononuclear, binuclear, and insoluble polynuclear oxovanadium(IV)-Schiff base complexes and their oxidation catalysis

The objective was to prepare mononuclear, binuclear, and insoluble polynuclear oxovanadium(IV)-Schiff base complexes and to use them for sulfoxidation and epoxidation of organic substrates. [VO(salen)] (complex 1) with tetradentate salen(salicylideneethylenediamine) being coordinated in the equatorial plane of oxovanadium(IV), [VO(salap)] (complex 2), and [(VO)₂(sal₂-dhdabp)] (complex 3) with tridentate salap(salicylideneorthoaminophenol) and sal₂-dhdabp(salicylidene-3,3^′-dihydroxy-4,4^′-diaminobiphenyl) being bound, respectively, in the equatorial plane, of which polynuclear complexes were constituted as monomer units, were prepared and spectroscopically characterized. A sulfide and olefins were oxidized by use of complexes 1 and 2 (mononuclear), complex 3 (binuclear), and the polynuclear complexes (poly-1 and poly-3) synthesized with 1 and 3, respectively. The reaction rates for poly-1 and -3 were a little lower than those of the corresponding 1 and 3. On oxidation of sulfides, poly-3 exhibited lowering of activity by about 15% in three cycles, while poly-1 showed significant lose of activity with each use. Poly-3 was efficient for the oxidation of the olefins only in the first cycle. It was suggested that the loss of activity depends not only on the coordination geometry of the oxovanadium complex, but also on the kind of the substrate.     

First synthesis of a dihydrido functionalized double-cored oligosilane dendrimer

The reaction of (R₂MeSi)₂SiHCl (2) [R=SiMe₃] with Na-K-alloy yields the double-cored dendritic oligosilane [(R₂MeSi)₂SiH]₂ (4). The structure of 4 was obtained from X-ray diffraction data, which verify a total of 14 silicon atoms and a longest chain of six silicon atoms. The UV-Vis spectra of 4 and the structurally analogous [(R₂MeSi)₂SiMe]₂ (5) exhibit absorption maxima (shoulders) at 269 nm (ε=2.0×10⁴) and 276 nm (ε=2.3×10⁴), respectively, which are the longest so far observed for alkyl substituted oligosilanes with hexasilane chains.