Triaryl (Z)-olefins suitable for radiolabeling with iodine-124 or fluorine-18 radionuclides for positron emission tomography imaging of estrogen positive breast tumors

A group of (Z)-1,2-diphenyl-1-[4-[2-(4-methylpiperazin-1-yl)ethoxy]phenyl]but-1-enes were synthesized using methodologies that will allow incorporation of a [¹²⁴I]iodine substituent at the para-position of either the C-1 phenyl ring or the C-2 phenyl ring, or a [¹⁸F]OCH₂CH₂F substituent at the para-position of the C-2 phenyl ring. These [¹²⁴I] and [¹⁸F] radiotracers are designed as potential radiopharmaceuticals to image estrogen positive breast tumors using positron emission tomography (PET).     

Synthesis and spectroscopic and X-ray structural characterisation of some para-substituted triaryltin(pentacarbonyl)manganese(I) complexes

A series of para-substituted triaryltin(pentacarbonyl)manganese(I) compounds [(p-XC₆H₄)₃SnMn(CO)₅: II, X=CH₃; III, X=CH₃O; IV, X=CH₃S; V, X=F; VI, X=Cl; VII, X=CH₃S(O₂)] is reported for comparison with the known phenyl analogue I. IR data [ν(CO)] as well as complete ¹¹⁹Sn/⁵⁵Mn/¹³C solution NMR results are given for I-VII. Chemical shifts, ¹¹⁹Sn versus ⁵⁵Mn, except I, correlate well, but have differing single parameter (SP) correlations, ¹¹⁹Sn versus σ_I and ⁵⁵Mn versus σ°_p. These results are compared with previous SP studies of the ¹¹⁹Sn solution NMR spectra of the series, (p-XC₆H₄)₄Sn and (p-XC₆H₄)₃SnY (Y=Cl, Br, I). Full crystal structures are reported for compounds II-VI. All are similar to that of I, with the Mn(CO)₅ moiety being a distorted tetragonal pyramid, and having a quasi-mirror plane through the central C₄MnSnC₃ skeleton. The Ar₃Sn are distorted trigonal propellers with ring torsion angles in the range 30-80°, the exception being IV with one torsion angle of 22°.     

Synthesis, spectroscopical characterization and the biological activity in vitro of new platinum(II) complexes with imidazo[1,5-a]-1,3,5-triazine derivatives and dimethylsulfoxide

A series of platinum(II) complexes with 6,8-dimethylimidazo[1,5-a]-1,3,5-triazin-4(3H)-one (6,8-DiMe-4-O-IMT) (I) and 6,8-dimethyl-2-thioxo-2,3-dihydroimidazo[1,5-a]-1,3,5-triazin-4(1H)-one (6,8-DiMe-4-O-2-S-IMT) (II) of formula trans-[PtCl₂(dmso)(6,8-DiMe-4-O-IMT)] (1a) and trans-[PtCl₂(dmso)(6,8-DiMe-4-O-2-S-IMT)] (2a) have been prepared and characterized with ¹H, ¹³C, ¹⁵N, ¹⁹⁵Pt NMR and IR. Significant ¹⁵N NMR upfield coordination shifts (81-96 ppm) of N(7) atom indicate this nitrogen atom as a coordination site. The multinuclear NMR and IR spectra indicate the square planar geometry with N(7) bonded heterocycles, S-bonded dimethylsulfoxide and two trans chloride anions. The platinum(II) complexes were tested for their antiproliferative activity in vitro against the cells of four human cell lines: SW707 rectal adenocarcinoma, A549 non-small cell lung carcinoma, T47D breast cancer and HCV29T bladder cancer. The activity of (1a, 2a) was lower than that of cisplatin.     

Silver(I) derivatives with new functionalised acylpyrazolonates

Silver(I) acylpyrazolonate derivatives of formula [Ag(Q)(R₃P)]₂ and [Ag(Q)(R₃P)₂], (QH=1-phenyl-3-methyl-4-R′(CO)-pyrazol-5-one; Q^OH, R′=furane; Q^SH, R′=thiophene; R=Ph, Cy, o-tol), have been synthesised and characterised, both in the solid state and in solution. The derivatives [Ag(Q)(R₃P)]₂ contain dinuclear AgO₂NP units with the acylpyrazolonate coordinating in a bridging O,O′-Q-N fashion. The [Ag(Q)(R₃P)₂] are tetrahedral species, with the distortion from ideal geometry increasing with the bulk of the phosphine. The [Ag(Q)(R₃P)₂] derivatives are fluxional in chloroform solution when R₃P is sterically hindered (R=Cy or o-tol), dissociating partially to the [Ag(Q)(R₃P)] fragment and free R₃P. [Ag(Q^S)(Ph₃P)]₂ reacts with 1-methyl-2-mercaptoimidazole (Hmimt) affording the compound [Ag(Hmimt)(Ph₃P)(Q^S)] and [Ag(Q^O)(Ph₃P)]₂ reacts with 1-methyl-imidazole (Meim) affording the compound [Ag(Meim)(Ph₃P)(Q^O)], whereas [Ag(Q^S)(Ph₃P)]₂ reacts with 1,10-phenanthroline (phen), affording the compound [Ag(phen)(Ph₃P)](Q^S). Finally [Ag(Q^S)(Ph₃P)₂] reacts with phen producing the ionic species [Ag(phen)(Ph₃P)₂](Q^S).     

Preparation and structural organisation of heteroleptic tetraphenylantimony(V) complexes comprising unidentately and bidentately coordinated O,O′-dialkyldithiophosphate groups: Multinuclear (C, P) CP/MAS NMR and single-crystal X-ray diffraction studies

O,O′-dipropyldithiophosphate and O,O′-di-iso-butyldithiophosphate (Dtph) tetraphenylantimony(V) complexes of the general formula [Sb(C₆H₅)₄{S₂P(OR)₂}] (R = C₃H₇, i-C₄H₉) were prepared and studied by means of ¹³C, ³¹P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. Distorted octahedral and trigonal bipyramidal molecular structures have been established for prepared complexes. These unexpected structural distinctions between chemically related compounds are defined by the principally different coordination modes of O,O′-dipropyldithiophosphate and O,O′-di-iso-butyldithiophosphate ligands in their molecular structures (i.e., S,S′-bidentate chelating and S-unidentately coordinated, respectively). To characterise quantitatively phosphorus sites in both species of dithiophosphate ligands, ³¹P chemical shift anisotropy parameters (δ_aniso and η) were calculated from spinning sideband manifolds in MAS NMR spectra. The ³¹P chemical shift tensors for the bidentate chelating and unidentately coordinated dithiophosphate ligands display a profoundly rhombic and nearly axially symmetric characters, respectively.     

Synthesis and characterization of silver(I) derivatives containing acylpyrazolonate and phosphino ligands: X-ray crystal structures of monomeric [Ag(Q)(PPh3)2] and of dimeric [{Ag(Q)(PiBu3)}2] (Q = 1-phenyl-3-methyl-4-tert-butylacetylpyrazolon-5-ato)

New silver(I) acylpyrazolonate derivatives [Ag(Q)], [Ag(Q)(PR₃)]₂ and [Ag(Q)(PR₃)₂] (HQ = 1-R¹-3-methyl-4-R²(CO)pyrazol-5-one, HQ^Bn = R¹ = C₆H₅, R² = CH₂C₆H₅; HQ^CHPh2 = R¹ = C₆H₅, R² = CH(C₆H₅)₂; HQ^nPe = R¹ = C₆H₅, R² = CH₂C(CH₃)₃; HQ^tBu = R¹ = C₆H₅, R² = C(CH₃)₃; HQ^fMe = R¹ = C₆H₄-p-CF₃, R² = CF₃; HQ^fEt = R¹ = C₆H₅, R² = CF₂CF₃; R = Ph or iBu) have been synthesized and characterized in the solid state and solution. The crystal structure of 1-(4-trifluoromethylphenyl)-3-methyl-5-pyrazolone, the precursor of proligand HQ^fMe and of derivatives [Ag(Q^nPe)(PPh₃)₂] and [Ag(Q^nPe)(PiBu₃)]₂ have been investigated. [Ag(Q^nPe)(PPh₃)₂] is a mononuclear compound with a silver atom in a tetrahedrally distorted AgO₂P₂ environment, whereas [Ag(Q^nPe)(PiBu₃)]₂ is a dinuclear compound with two O₂N-exotridentate bridging acylpyrazolonate ligands connecting both silver atoms, their coordination environment being completed by a phosphine ligand.     

Isolation and structure of d-xylans from pericarp seeds of Opuntia ficus-indica prickly pear fruits

Xylans were isolated from the pericarp of prickly pear seeds of Opuntia ficus-indica (OFI) by alkaline extraction, fractionated by precipitation and purified. Six fractions were obtained and characterized by sugar analysis and NMR spectroscopy. They were assumed to be (4-O-methyl-d-glucurono)-d-xylans, with 4-O-α-d-glucopyranosyluronic acid groups linked at C-2 of a (1→4)-β-d-xylan. The sugar composition and the ¹H and ¹³C NMR spectra showed that their chemical structures were very similar, but with different proportions of d-Xyl and 4-O-Me-d-GlcA. Our results showed that, on average, the water soluble xylans have one nonreducing terminal residue of 4-O-methyl-d-glucuronic acid for every 11 to 14 xylose units, whereas in the water non-soluble xylans, xylose units can varied from 18 to 65 residues for one nonreducing terminal residue of 4-O-methyl-d-glucuronic acid.     

Chromones from the tubers of Eranthis cilicica and their antioxidant activity

Chemical studies on the constituents of Eranthis cilicica led to isolation of ten chromone derivatives, two of which were previously known. Comprehensive spectroscopic analysis, including extensive 1D and 2D NMR data, and the results of enzymatic hydrolysis allowed the chemical structures of the compounds to be assigned as 8,11-dihydro-5-hydroxy-2,9-dihydroxymethyl-4H-pyrano[2,3-g][1]benzoxepin-4-one, 5,7-dihydroxy-8-[(2E)-4-hydroxy-3-methylbut-2-enyl]-2-methyl-4H-1-benzopyran-4-one, 5,7-dihydroxy-2-hydroxymethyl-8-[(2E)-4-hydroxy-3-methylbut-2-enyl]-4H-1-benzopyran-4-one, 7-[(β-d-glucopyranosyl)oxy]-5-hydroxy-8-[(2E)-4-hydroxy-3-methylbut-2-enyl]-2-methyl-4H-1-benzopyran-4-one, 7-[(β-d-glucopyranosyl)oxy]-5-hydroxy-2-hydroxymethyl-8-[(2E)-4-hydroxy-3-methylbut-2-enyl]-4H-1-benzopyran-4-one, 9-[(O-β-d-glucopyranosyl-(1→6)-β-d-glucopyranosyl)oxy]methyl-8,11-dihydro-5,9-dihydroxy-2-methyl-4H-pyrano[2,3-g][1]benzoxepin-4-one, 8,11-dihydro-5,9-dihydroxy-9-hydroxymethyl-2-methyl-4H-pyrano[2,3-g][1]benzoxepin-4-one, and 7-[(O-β-d-glucopyranosyl-(1→6)-β-d-glucopyranosyl)oxy]methyl-4-hydroxy-5H-furo[3,2-g][1]benzopyran-5-one, respectively. The isolated compounds were evaluated for their antioxidant activity.     

The synthesis and characterisation of Rh(III) complexes with pyridyl triazole ligands

A series of Rh(III) mixed ligand polypyridine type complexes have been prepared. Complexes of the form [Rh(L)₂(L^′)]ⁿ⁺, where n=2/3, L=2,2^′-bipyridine (bpy)/1,10-phenanthroline (phen) and L^′=3-(pyridin-2-yl)-1,2,4-triazole (Hpytr), 1-methyl-3-(pyridin-2-yl)-1,2,4-triazole (1M3pytr), 4-methyl-3-(pyridin-2-yl)-1,2,4-triazole (4Mpytr), 3,5-bis(pyridin-2-yl)-1,2,4-triazole (Hbpt), 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (NH₂bpt) and 3-(pyridin-2-yl)-5-phenyl-1,2,4-triazole (HPhpytr), have been prepared and their synthesis and characterisation are reported. Crystals of [Rh(bpy)₂(Phpytr)](PF₆)₂ and [Rh(phen)₂(NHbpt)](PF₆)₂ were obtained and their structures determined. Analysis of X-ray crystallographic data showed that coordination of the metal centre in [Rh(phen)₂(NHbpt)](PF₆)₂ occurs via the amine moiety and a nitrogen of the pyridine ring. NMR studies illustrated that coordination to the NH₂bpt ligand was also possible via a nitrogen of the triazole ring and the pyridine ring forming the complex [Rh(phen)₂(NH₂bpt)](PF₆)₃. The absorption and emission properties of the complexes studied were found to be π-π^* in nature and preliminary evidence suggests that all complexes with the exception of [Rh(phen)₂(NHbpt)](PF₆)₂ and [Rh(bpy)₂(NHbpt)](PF₆)₂ are dual emitting at 77 K.     

Synthesis, characterization and X-ray crystal structure of [Re(L4)(CO)3]Br · 2CH3OH (L4 = N,N-bis[(2-diphenylphosphino)ethyl]methoxyethylamine): A model compound for novel cationic Tc(I)-tricarbonyl radiotracers useful for heart imaging

This report describes synthesis and evaluation of cationic complexes, [^99mTc(CO)₃(L)]⁺ (L = N-methoxyethyl-N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]amine (L1), N-[(15-crown-5)-2-yl]-N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]amine (L2) and N-[(18-crown-6)-2-yl]-N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]amine (L3)) as potential radiotracers for heart imaging. Preliminary results from biodistribution studies in female adult BALB-c mice indicated that the cationic ^99mTc(I)-tricarbonyl complex, [^99mTc(CO)₃(L2)]⁺, has a significant localization in the heart at 60 min post-injection. To understand the coordination chemistry of these bisphosphine ligands with the ^99mTc(I)-tricarbonyl core, we prepared [Re(CO)₃(L4)]Br (L4: N,N-bis[(2-diphenylphosphino)ethyl]methoxyethylamine) as a model compound. [Re(CO)₃(L4)]Br has been characterized by elemental analysis, IR, ESI-MS, NMR (¹H, ¹³C, ¹H-¹H COSY, and ¹H-¹³C HMQC) methods, and X-ray crystallography. In solid state, [Re(CO)₃(L4)]⁺ has a distorted octahedron coordination geometry with PNP occupying one facial plane. The chelator backbone adopts a “chair” conformation with phosphine-P atoms at equatorial positions and the amine-N at the apical site. In solution, [Re(CO)₃(L4)]⁺ is able to maintain its cationic nature with no dissociation of carbonyl ligands or any of the three PNP donors.     

A nearly symmetric trinuclear chromium(III) oxo carboxylate assembly: preparation, molecular and crystal structure, and magnetic properties of [Cr3O(O2CPh)6(MeOH)3](NO3) · 2MeOH

Complex [Cr₃O(O₂CPh)₆(MeOH)₃](NO₃) · 2MeOH (1 · 2MeOH) has been synthesized from the one-pot reaction between Cr(NO₃)₃ · 9H₂O and NaO₂CPh in MeOH. The structure of the complex has been solved by single-crystal X-ray crystallography. It crystallizes in the monoclinic space group P2₁/n with a=14.716(6) Å, b=22.569(8) Å, c=15.755(6) Å, β=95.02(1)°, V=5212.5(4) ų and Z=4. Although the cation does not possess any crystallographically imposed symmetry element, its {Cr₃(μ₃-O)} core is nearly symmetric. Each Cr^III…Cr^III vector is further bridged by two η¹:η¹:μ₂ benzoates, with a terminal MeOH molecule completing octahedral coordination at each metal ion. The crystal structure consists of layers that are parallel to (0 1 0) crystallographic plane and are formed through π-π stacking interactions and hydrogen bonds. Variable-temperature magnetic susceptibility and solid-state ¹H NMR studies indicate that the total spin value of the ground state is 1/2. EPR experiments reveal the existence of a distribution of trimers with axial anisotropy in the g tensor.     

Regioselective synthesis of a glycomimetic trisaccharide of Sialyl Lewis (sLe)

Sialyl Lewis (sLe^x) is the smallest naturally occurring carbohydrate ligand that binds to E-Selectin on the activated endothelium. We report here the total synthesis of acetic acid-sLe^x analog (12), for testing as a therapeutic agent. Methoxyethyl 4-O-(3,4-O-isopropylidene-β-d-galactopyranosyl)-β-d-glucopyranoside (3) was prepared starting from the methoxyethyl-β-d-lactoside (2), which was selectively benzoylated to give the methoxyethyl 2,6-di-O-benzoyl-4-O-(2,6-di-O-benzoyl-3,4-O-isopropylidene-β-d-galactopyranosyl)-β-d-glucopyranoside (4). Glycosylation of acceptor 4 with methyl 2,3,4-tri-O-benzyl-1-thio-β-l-fucopyranoside (5) in the presence of cupric bromide and tetrabutylammonium bromide afforded the corresponding methoxyethyl 2,6-di-O-benzyl-3-O-(2,3,4-tri-O-benzyl-α-l-fucopyranosyl)-4-O-(2,6-di-O-benzyl-3,4-O-isopropylidene-β-d-galactopyranosyl)-β-d-glucopyranoside (6). Selective removal of the 4″,6″-O-isopropylidene group from 6 gave the deprotected trisaccharide 7. The regioselective esterification of O-3″ of trisaccharide 8 (obtained from the dibutylstannylene derivative of 7) with benzyl-2-bromoacetate and tetrabutylammonium bromide afforded the 3″-O-carbobenzyloxymethyl trisaccharide derivative 9, which on saponification and hydrogenolysis with palladium-charcoal afforded the target trisaccharide 12 glycomimetic of Sialyl Lewis (sLe^x) trisaccharide omitting the sialic acid moiety.     

The structural definition of adducts of stoichiometry AgX:dppf (1:1)(n), X = simple anion, dppf = bis(diphenylphosphino)ferrocene

Single crystal X-ray structural characterizations are recorded for an array of adducts of the form AgX:dppf (1:1)_(n), X = simple (pseudo-)halide or oxy-anion, ‘dppf’ = bis(diphenyl phosphino)ferrocene, for adducts X = Cl (new phase), Br, I, SCN, OCN, CN, NO₃ (new phase), O₂CCH₃, n = 2, the form being dimeric [(dppf-P,P′)Ag(μ-X)₂Ag(P,P′-dppf)], for X = I, SCN, [Ag(μ-X)₂(P-dppf-P′)₂Ag′]; for X = O₂CCF₃, n = ∞, the form is an extended polymer: ?Ag(O · CO · CF₃)(P-dppf-P′)Ag′(O?. A dichloromethane solvate phase of CuI:dppf (1:1)₂ (also centrosymmetric) is also recorded. Synthetic procedures for all adducts have been reported. All compounds have been characterized both in solution (¹H, ¹³C, ³¹P NMR, ESI MS) and in the solid state (IR). The topology of the structures in the solid state was found to depend on the nature of the counterion.     

Carrageenan from Sarconema scinaioides (Gigartinales, Rhodophyta) of Indian waters

Carrageenan was extracted from the red seaweed Sarconema scinaioides of Indian waters and was characterized. The crude carrageenan as well as its alkali modified derivative was composed of 3,6-anhydro galactose, 6-O-methyl galactose as well as galactose moieties in various proportions. Linkage analysis exhibited that these two carrageenan samples consisted of 4-linked 3,6-anhydrogalactose residue sulphated at position 2, and 3-linked galactose residue sulphated at position 4. The physicochemical and rheological data along with molecular weight data, FT-IR, 1D and 2D NMR (¹H, ¹³C, COSY and HSQC) spectrometry suggested that the polysaccharide was composed predominantly of iota- along with a small amount of its precursor nu (ν)-carrageenan, unlike the hybrid carrageenans (iota-, pyruvated- and kappa-carrageenans) from this seaweed reported in the literature. This Indian seaweed species would be a potentially important source of iota-carrageenan.     

Convenient and Efficient Syntheses of Oligodeoxyribonucleotides Containing O 6-(Carboxymethyl)Guanine and O 6-(4-Oxo-4-(3-Pyridyl)Butyl)Guanine

O ⁶-(carboxymethyl)guanine (O ⁶-CMG) and O ⁶-(4-oxo-4-(3-pyridyl)butyl)guanine (O ⁶-pobG) are toxic lesions formed in DNA following exposure to alkylating agents. O ⁶-CMG results from exposure to nitrosated glycine or nitrosated bile acid conjugates and may be associated with diets rich in red meat. O ⁶-pobG lesions are derived from alkylating agents found in tobacco smoke. Efficient syntheses of oligodeoxyribonucleotides (ODNs) containing O ⁶-CMG and O ⁶-pobG are described that involve nucleophilic displacement by the appropriate alcohol on a common synthetic ODN containing the reactive base 2-amino-6-methylsulfonylpurine. ODNs containing O ⁶-pobG and O ⁶-CMG were found to be good substrates for the S. pombe alkyltransferase-like protein Atl1.

[Supplemental materials are available for this article. Go to the publisher's online edition of Nucleosides, Nucleotides & Nucleic Acids to view the free supplemental file.]     

Selective formation of glycosidic linkages of N-unsubstituted 4-hydroxyquinolin-2-(1H)-ones

A comparative study for selective glucosylation of N-unsubstituted 4-hydroxyquinolin-2(1H)-ones into 4-(tetra-O-acetyl-β-d-glucopyranosyloxy)quinolin-2(1H)-ones is reported. Four glycosyl donors including tetra-O-acetyl-α-d-glucopyranosyl bromide, β-d-glucose pentaacetate, glucose tetraacetate and tetra-O-acetyl-α-d-glucopyranosyl trichloroacetimidate were tested, along with different promoters and reaction conditions. The best results were obtained with tetra-O-acetyl-α-d-glucopyranosyl bromide with Cs₂CO₃ in CH₃CN. In some cases the 4-O-glucosylation of the quinolinone ring was accompanied by 2-O-glucosylation yielding the corresponding 2,4-bis(tetra-O-acetyl-β-d-glucopyranosyloxy)quinoline. Next, 4-(tetra-O-acetyl-β-d-glucopyranosyloxy)quinolin-2(1H)-ones were deacetylated into 4-(β-d-glucopyranosyloxy)quinolin-2(1H)-ones with Et₃N in MeOH. In some instances the deacetylation was accompanied by the sugar-aglycone bond cleavage. Structure elucidation, complete assignment of proton and carbon resonances as well as assignment of anomeric configuration for all the products under investigation were performed by 1D and 2D NMR spectroscopy.     

The structural definition of adducts of stoichiometry MX:dpex (2:3)(∞), M = Cu, Ag, X = simple anion, dpex = Ph2E(CH2)xEPh2, E = P, As

Single crystal X-ray structural characterizations are recorded for a number of adducts of MX:dpex (2:3) stoichiometry (MX = simple univalent copper or silver salt; dpex = Ph₂E(CH₂)_xEPh₂ (E = P, As)). CuX:dppe (2:3) (X = Cl, Br, I, CN) are binuclear [(dppe-P,P′)CuX(P-dppe-P′)CuX(P,P′-dppe)], all centrosymmetric. AgX:dpex (2:3) (dpex = ‘dpae’ (Ph₂As(CH₂)₂AsPh₂), X = Br, F₃CCO₂ (= ‘tfa’), F₃CSO₃ (≡ ‘tfs’); dpex = ‘dpape’ (Ph₂As(CH₂)₂PPh₂), X = CN, SCN, OClO₃) are one-dimensional polymers ?-E′)₁AgX(E-dpex-E′)₂-AgX(E-dpex-E′)₁AgX?, P, As sites scrambled in the latter. AgNO₃:dpam (2:3) is also a one-dimensional polymer, ?AgO·NO·OAg(As-dpam-As)AgO·NO·OAg? (‘dpam’ ≡ Ph₂As(CH₂)₂AsPh₂). AgX:dpae (2:3) (X = I, CN, ClO₄, NO₃) and AgX:dpape (2:3) (X = Br, I, NO₃) are two-dimensional polymers with large 30-membered macrocyclic rings; similar webs are found for dppx ligands in AgOH:dppb (2:3) and AgNCO, Agtfa:dpph (2:3) with 42- and 54-membered rings. Complexes AgX:dpape (1:3) (X = Cl, Br) are defined as mono-nuclear [XAg(Ph₂P(CH₂)₂AsPh₂)₃] arrays, the unidentate ligands predominantly P-bound. Synthetic procedures for the adducts are reported, selected compounds being characterized both in solution (¹H, ³¹P NMR, ESI MS) and in the solid state (IR).     

The unique alternation of conformationally different (‘chair’-‘saddle’) eight-membered metallocycles [Cd2S4P2] in the chains of cadmium dialkyldithiophosphates: C, P, Cd CP/MAS NMR and single-crystal X-ray diffraction studies

O,O′-Dipropyldithiophosphate and O,O′-dibutyldithiophosphate (Dtph) cadmium(II) complexes were prepared and studied by means of heteronuclear ³¹P, ¹¹³Cd, ³¹C CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. Linear-chain polynuclear structures have been established for both cadmium(II) complexes, in which each pair of equivalent dithiophosphate groups, playing the same bridging structural function, asymmetrically links the neighbouring cadmium atoms. One remarkable structural feature of the synthesised cadmium(II) compounds is defined by the alternation of two types of conformationally different (‘chair’-‘saddle’) eight-membered rings [Cd₂S₄P₂] in the polymeric chains. Therefore, in both ³¹P NMR and XRD data, the bridging dithiophosphate ligands exhibit structural inequivalence in pairs. The structural states of both Dtph ligands and cadmium atoms have been characterised by the ³¹P and ¹¹³Cd chemical shift tensors, which display a profound axially symmetric and mainly rhombic characters, respectively. All experimental ³¹P resonances were assigned to the phosphorus structural sites in both resolved structures.     

Conformational isomerism of the binuclear N,N-pentamethylenedithiocarbamate cadmium(II) complex, [Cd2{S2CN(CH2)5}4] on multinuclear (N, Cd) CP/MAS NMR and single-crystal X-ray diffraction data

Crystalline N,N-cyclo-pentamethylenedithiocarbamate (PmDtc) cadmium(II) complex was prepared and studied by means of ¹⁵N, ¹¹³Cd CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. The unit cell of the cadmium(II) compound comprises two centrosymmetric isomeric binuclear molecules [Cd₂{S₂CN(CH₂)₅}₄], which display structural inequivalence in both ¹⁵N and ¹¹³Cd NMR and XRD data. There are pairs of the dithiocarbamate ligands exhibiting different structural functions in both isomeric molecules. Each of the terminal ligands is bidentately coordinated to the cadmium atom and forms a planar four-membered chelate ring [CdS₂C]; whereas pairs of the tridentate bridging ligands combine two neighbouring cadmium atoms forming an extended eight-membered tricyclic moieties [Cd₂S₄C₂], whose geometry can be approximated by a ‘chair’ conformation. The structural states of cadmium atoms were characterised by almost axially symmetric ¹¹³Cd chemical shift tensors. All experimental ¹⁵N resonance lines were assigned to the nitrogen structural sites in both isomeric binuclear molecules.     

Synthesis of thiazole-based substituted piperidinone oximes: Profiling of antioxidant and antimicrobial activity

The synthesis of novel thiazole-based piperidinone oximes and screening of their antioxidant and antimicrobial activity are described. The obtained results revealed that the electronic effects of active substituents at C-4 terminals of phenyl rings on either side of piperidinone skeleton, as well as at 2-hydrazinyl thiazole, played a major role in development of antioxidant and antimicrobial activity. Antioxidant activity seems to be based also on radical dissipating ability of the thiazole ring. The nucleophilic character of sulfur in thiazole and lipophilic nature of piperidinone skeleton substantially influenced the observed antimicrobial activity of thiazole-based piperidinone oximes. Among the synthesized compounds, 2,6-bis(4-hydroxy-3-methoxyphenyl)-1-methylpiperidin-4-one O-(2-(2-(4-hydroxy-3-methoxybenzylidene)hydrazinyl)thiazol-4-yl) oxime exhibited excellent antioxidant activity whereas compound 2,6-bis(4-chloro phenyl)-1-methylpiperidin-4-one O-(2-(2-(4-nitrobenzylidene)hydrazinyl)thiazol-4-yl)oxime emerged as an outstanding antimicrobial agent.