Inert Transition Metal Ion Complexes in Organic Synthesis: Protection and Activation.

Single-crystal X-ray diffraction studies for a variety of metal ion complexes of functionalised sarcophagines (sarcophagine=sar=3,6,10,13,16,19-hexa-azabicyclo[6.6.6]icosane) have further confirmed not only that the form of the metal ion/sar unit is unique for each metal, albeit with a sensitivity of the conformation to the associated counter anions, but also that for any given metal and ligand substituent, the dimensions (bond lengths and angles) of the complex and the substituent at the secondary nitrogen centres do not differ significantly from those of the isolated components. Despite this, where the substituent contains reactive sites, the reactivity differs markedly from that of their form in an uncoordinated substrate. Rationalisations are offered for these differences, in part through the use of Hirshfeld surface analysis of the intermolecular interactions. The kinetic inertness of the complexes means that the metal ions can be considered to act as regioselective protecting groups.

Correction: Self-assembly of arene ruthenium acylpyrazolone fragments to tetranuclear metallacycles. Molecular structures and solid-state (15)N CPMAS NMR correlations.

Correction for 'Self-assembly of arene ruthenium acylpyrazolone fragments to tetranuclear metallacycles. Molecular structures and solid-state (15)N CPMAS NMR correlations' by Riccardo Pettinari et al., Dalton Trans., 2016, 45, 3974-3982.

Self-assembly of arene ruthenium acylpyrazolone fragments to tetranuclear metallacycles. Molecular structures and solid-state (15)N CPMAS NMR correlations.

Reactions of [(η(6)-cymene)Ru(µ-Cl)Cl]2 with acylpyrazolone ligands HQ' (HQ' in general; in detail, HQ(CH2Cl) = 2-chloro-1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)ethanone), HQ(hex) = 1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)heptan-1-one), HQ(nPe) = 1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-3,3-dimethylbutan-1-one)), in the presence of base, gave the corresponding [(η(6)-cymene)Ru(Q')Cl] mononuclear complexes. They react with AgX (where X = O3SCF3 or BF4) in dry acetone affording cationic metalla-cycles [(η(6)-cymene)Ru(Q')]4(X)4. The complexes were fully characterized by analytical and spectroscopic methods and the solid-state structures of mononuclear and tetranuclear complexes have been determined by single-crystal X-ray diffraction. The hapticity of the acylpyrazolone ligands to the Ru metal centre has also been established by (13)C and (15)N CPMAS NMR spectroscopy for the complexes where the lack of crystallinity prevented the elucidation of the crystal structure by SCXRD data.

Arene-ruthenium(II) acylpyrazolonato complexes: apoptosis-promoting effects on human cancer cells.

A series of ruthenium(II) arene complexes with the 4-(biphenyl-4-carbonyl)-3-methyl-1-phenyl-5-pyrazolonate ligand, and related 1,3,5-triaza-7-phosphaadamantane (PTA) derivatives, has been synthesized. The compounds have been characterized by NMR and IR spectroscopy, ESI mass spectrometry, elemental analysis, and X-ray crystallography. Antiproliferative activity in four human cancer cell lines was determined by MTT assay, yielding dose- and cancer cell line-dependent IC50 values of 9-34 µM for three hexamethylbenzene-ruthenium complexes, whereas the other metal complexes were much less active. Apoptosis was the mechanism involved in the anticancer activity of such compounds. In fact, the hexamethylbenzene-ruthenium complexes activated caspase activity, with consequent DNA fragmentation, accumulation of pro-apoptotic proteins (p27, p53, p89 PARP fragments), and the concomitant down-regulation of antiapoptotic protein Bcl-2. Biosensor-based binding studies indicated that the ancillary ligands were critical in determining the DNA binding affinities, and competition binding experiments further characterized the nature of the interaction.

New RuII (arene) complexes with halogen-substituted bis- and tris(pyrazol-1-yl)borate ligands.

[RuCl(arene)(µ-Cl)]2 dimers were treated in a 1:2 molar ratio with sodium or thallium salts of bis- and tris(pyrazolyl)borate ligands [Na(Bp(Br3))], [Tl(Tp(Br3))], and [Tl(Tp(iPr, 4Br))]. Mononuclear neutral complexes [RuCl(arene)(κ(2)-Bp(Br3))] (1: arene=p-cymene (cym); 2: arene=hexamethylbenzene (hmb); 3: arene=benzene (bz)), [RuCl(arene)(κ(2)-Tp(Br3))] (4: arene=cym; 6: arene=bz), and [RuCl(arene)(κ(2)-Tp(iPr, 4Br))] (7: arene=cym, 8: arene=hmb, 9: arene=bz) have been always obtained with the exception of the ionic [Ru2 (hmb)2-(µ-Cl)3][Tp(Br3)] (5'), which formed independently of the ratio of reactants and reaction conditions employed. The ionic [Ru-(CH3OH)(cym)(κ(2)-Bp(Br3))][X] (10: X=PF6, 12: X=O3SCF3) and the neutral [Ru(O2CCF3)(cym)(κ(2)-Bp(Br3))] (11) have been obtained by a metathesis reaction with corresponding silver salts. All complexes 1-12 have been characterized by analytical and spectroscopic data (IR, ESI-MS, (1)H and (13)C NMR spectroscopy). The structures of the thallium and calcium derivatives of ligand Tp(Br3), [Tl(Tp(Br3))] and [Ca(dmso)6][Tp(Br3)]2 ⋅2 DMSO, of the complexes 1, 4, 5', 6, 11, and of the decomposition product [RuCl(cym)(Hpz(iPr, 4Br))2][Cl] (7') have been confirmed by using single-crystal X-ray diffraction. Electrochemical studies showed that 1-9 and 11 undergo a single-electron Ru(II) →Ru(III) oxidation at a potential, measured by cyclic voltammetry, which allows comparison of the electron-donor characters of the bis- and tris(pyrazol-1-yl)borate and arene ligands, and to estimate, for the first time, the values of the Lever EL ligand parameter for Bp(Br3), Tp(Br3), and Tp(iPr, 4Br). Theoretical calculations at the DFT level indicated that both oxidation and reduction of the Ru complexes under study are mostly metal-centered with some involvement of the chloride ligand in the former case, and also demonstrated that the experimental isolation of the µ(3)-binuclear complex 5' (instead of the mononuclear 5) is accounted for by the low thermodynamic stability of the latter species due to steric reasons.

Synthesis and X-ray structural studies of a substituted 2,3,4,5-tetrahydro-1H-3-benzazonine and a 1,2,3,5-tetrahydro-4,3-benzoxazonine.

Using a common 1-(1-phenylethenyl)-1,2,3,4-tetrahydroisoquinoline precursor to the required ylide or N-oxide intermediate, the Stevens [2,3] and analogous Meisenheimer [2,3] sigmatropic rearrangements have been applied to afford concise syntheses of phenyl -substituted representatives of each of the reduced 1H-3-benzazonine and 4,3-benzoxazonine systems, respectively. Single crystal X-ray structure determinations were employed to define the conformational characteristics for each ring type.

Oligo-nuclear silver thiocyanate complexes with monodentate tertiary phosphine ligands, including novel 'cubane' and 'step' tetramer forms of AgSCN : PR3 (1:1)4.

Adducts of a number of tertiary pnicogen ligands ER(3) (triphenyl-phosphine and -arsine (PPh(3),AsPh(3)), diphenyl,2-pyridylphosphine (PPh(2)py), tris(4-fluorophenyl)phosphine (P(C(6)H(4)-4F)(3)), tris(2-tolyl)phosphine (P(o-tol)(3)), tris(cyclohexyl)phosphine (PCy(3))), with silver(I) thiocyanate, AgSCN are structurally and spectroscopically characterized. The 1:3 AgSCN : ER(3) complexes structurally defined (for PPh(3),AsPh(3) (diversely solvated)) take the form [(R(3)E)(3)AgX], the thiocyanate X = NCS being N-bound, thus [(Ph(3)E)Ag(NCS)]. A 1:2 complex with PPh(2)py, takes the binuclear form [(pyPh(2)P)(2)Ag()Ag(PPh(2)py)(2)] with an eight-membered cyclic core. 1:1 complexes are defined with PPh(2)py, P(o-tol)(3) and PCy(3); binuclear forms [(R(3)P)Ag()Ag(PR(3))] are obtained with P(o-tol)(3) (two polymorphs), while novel isomeric tetranuclear forms, which may be envisaged as dimers of dimers, are obtained with PPh(2)py, and, as further polymorphs, with PCy(3); these latter may be considered as extensions of the 'cubane' and 'step' forms previously described for [(R(3)E)AgX](4) (X = halide) complexes. Solvent-assisted mechanochemical or solvent-assisted solid-state synthesis methods were employed in some cases, where complexes could not be obtained by conventional solution methods, or where such methods yielded a mixture of polymorphs unsuitable for solid-state spectroscopy. The wavenumbers of the ν(CN) bands in the IR spectra are in broad agreement with the empirical rule that distinguishes bridging from terminal bonding, but exceptions occur for compounds that have a double SCN bridged dimeric structure, and replacement of PPh(3) with PPh(2)py apparently causes a significant decrease in ν(CN) to well below the range expected for bridging SCN in these structures. (31)P CP MAS NMR spectra yield additional parameters that allow a correlation between the structures and spectra.

Mechanochemical and solution synthesis, X-ray structure and IR and 31P solid state NMR spectroscopic studies of copper(I) thiocyanate adducts with bulky monodentate tertiary phosphine ligands.

A number of adducts of copper(I) thiocyanate with bulky tertiary phosphine ligands, and some nitrogen-base solvates, were synthesized and structurally and spectroscopically characterised. CuSCN:PCy3 (1:2), as crystallized from pyridine, is shown by a single crystal X-ray study to be a one-dimensional polymer ...(Cy3P)2CuSCN(Cy3P)2CuSCN... (1) with the four-coordinate copper atoms linked end-on by S-SCN-N bridging thiocyanate groups. A second form (2), obtained from acetonitrile, was also identified and shown by IR and 31P CPMAS NMR spectroscopy to be mononuclear, with the magnitude of the dν(Cu) parameter measured from the 31P CPMAS and the ν(CN) value from the IR clearly establishing this compound as three-coordinate [(Cy3P)2CuNCS]. Two further CuSCN/PCy3 compounds CuSCN:PCy3 (1:1) (3), and CuSCN:PCy3:py (1:1:1) (4) were also characterized spectroscopically, with the dν(Cu) parameters indicating three- and four-coordinate copper sites, respectively. Attempts to obtain a 1:2 adduct with tri-t-butylphosphine have yielded, from pyridine, the 1:1 adduct as a dimer [(Bu(t)3P)((SCN)(NCS))Cu(PBu(t)3)] (5), while similar attempts with tri-o-tolylphosphine (from acetonitrile and pyridine (= L)) resulted in solvated 1:1:1 CuSCN:P(o-tol)3:L forms as dimeric [{(o-tol)3P}LCu((SCN)(NCS))CuL{P(o-tol)3}] (6 and 8). The solvent-free 1:1 CuSCN:P(o-tol)3 adduct (7), obtained by desolvation of 6, was characterized spectroscopically and dν(Cu) measurements from the 31P CPMAS NMR data are consistent with the decrease in coordination number of the copper atom from four (for 6) (P,N(MeCN)Cu,S,N) to three (for 7) (PCuS,N) upon loss of the acetonitrile of solvation. These results are compared with those previously reported for mononuclear and binuclear PPh3 adducts which demonstrate a clear tendency for the copper centre to remain four-coordinate. The IR spectroscopic measurements on these compounds show that bands in the far-IR spectra provide a much more definitive criterion for distinguishing between bridging and terminal bonding than does an often-used empirical rule based on ν(CN) in the mid-IR, which leads to the wrong conclusion in some cases.

Mechanochemical and solution synthesis, and crystal structures and IR and solid-state (CPMAS) NMR spectroscopy of some bis(triphenylphosphine)silver(I) mono- and di-hydrogencitrate systems.

The complex [(Ph(3)P)(2)Ag(H(2)cit)]·EtOH (1; H(2)cit(-) = dihydrogencitrate = C(6)H(7)O(7)(-)) contains [(Ph(3)P)(2)Ag(H(2)cit)] molecules in which the silver atom is coordinated to two PPh(3) molecules and the two oxygen atoms of one of the 'terminal'/1-carboxylate groups of the dihydrogencitrate group. The molecules form centrosymmetric hydrogen-bonded dimers in the solid. In [{(Ph(3)P)(2)Ag}(2)(Hcit)], (2), unsymmetrical deprotonation of the citrate grouping is found, from the 1- and 3- (i.e. terminal and central) carboxylates: [(Ph(3)P)(2)Ag(O(2)CCH(2)C(OH) (CH(2)COOH)CO(2))Ag(PPh(3))(2)]. The above complexes, as well as [(Ph(3)P)(3)Ag(H(2)cit)] (3) were prepared via conventional solution methods, involving the reaction of trisilver(I) citrate, citric acid and triphenylphosphine, and by a mechanochemical method involving the reaction of silver(I) oxide, citric acid and triphenylphosphine. IR studies of 1-3 show the presence of coordinated carboxylate and free carboxylic acid groups in the mono- and di-hydrogencitrate ligands, and the formation of 2 from 1 shows that dihydrogencitrate deprotonation can occur upon dissolution of 1 in protic solvents. High-field (9.40 T) (31)P CPMAS NMR spectra were recorded and analysed, yielding heteronuclear (1)J((107/109)Ag,(31)P) and homonuclear (2)J((31)P,(31)P) spin-spin coupling constants.

Synthesis and structural characterization of 1-[2-(5-nitro-1H-indol-2-yl)phenyl]methylpyridinium chloride.

In the course of studies on hybrid antibacterials incorporating 2-aryl-5-nitro-1H-indole moieties as potential bacterial NorA efflux pump inhibitors, the compound 1-[2-(5-nitro-1H-indol-2-yl)phenyl]methylpyridinium chloride (2) was synthesized and structurally characterized. This pyridinium chloride salt crystallized in the monoclinic space group P2(1)/c with the following unit cell dimensions: a 10.274(3) Å, b 13.101(4) Å, c 13.439(4) Å, b 107.702(7)°, V 1723.2(9) ų, Z (f.u.) = 4; R1 = 0.048, and wR2 = 0.13. Of interest in the single crystal X-ray structure is the (intramolecular) disposition of the pyridinium plane over the indole heterocyclic residue [interplanar dihedral angle 17.91(4)°].

Solution and mechanochemical syntheses, and spectroscopic and structural studies in the silver(I) (bi-)carbonate: triphenylphosphine system.

Syntheses of a number of adducts of silver(I) (bi-)carbonate with triphenylphosphine, both mechanochemically, and from solution, are described, together with their infra-red spectra, (31)P CP MAS NMR and crystal structures. Ag(HCO(3)):PPh(3) (1:4) has been isolated in the ionic form [Ag(PPh(3))(4)](HCO(3))·2EtOH·3H(2)O. Ag(2)CO(3):PPh(3) (1:4) forms a binuclear neutral molecule [(Ph(3)P)(2)Ag(O,µ-O'·CO)Ag(PPh(3))(2)](·2H(2)O), while Ag(HCO(3)):PPh(3) (1:2) has been isolated in both mononuclear and binuclear forms: [(Ph(3)P)(2)Ag(O(2)COH)] and [(Ph(3)P)(2)Ag(µ-O·CO·OH)(2)Ag(PPh(3))(2)] (both unsolvated). A more convenient method for the preparation of the previously reported copper(I) complex [(Ph(3)P)(2)Cu(HCO(3))] is also reported.

Highly fluorous complexes of nickel, palladium and platinum: solubility and catalysis in high pressure CO2.

A variety of Group 10 metal complexes [MXY(dfppp)], M = Ni, X, Y = Cl, Br, M = Pd, Pt, X, Y = Cl or CH(3), containing the recently reported highly fluorous diphosphine ligand, dfppp, 1,3-bis[di(fluoroponytail)phosphino]propane, {(p-F(13)C(6)C(6)H(4))(2)P}(2)(CH(2))(3) have been synthesised. They have been characterised by NMR, mass spectrometry and microanalysis, with two platinum complexes, [PtCl(2)(dfppp)] and [PtClMe(dfppp)], structurally characterised by single crystal X-ray diffraction studies. The highly fluorous nature of the ligands affords the complexes good supercritical CO(2) solubility as measured by supercritical fluid extraction (SFE), and has allowed for the copolymerisation of CO and ethylene using [PdClMe(dfppp)] as the catalyst precursor and CO(2) as the solvent. Additionally, PtCl(2) complexes of the new ligands dfppb, {(p-F(13)C(6)C(6)H(4))(2)P}(2)(CH(2))(4), and dfpop, {(p-F(13)C(6)C(6)H(4)O)(2)P}(2)(CH(2))(3), have also been prepared and characterised.

Mechanochemical synthesis in copper(II) halide/pyridine systems: single crystal X-ray diffraction and IR spectroscopic studies.

Whereas complexes of divalent metal halides (X = Cl, Br, I) with/from pyridine commonly crystallise as trans-[M(py)(4)X(2)]·2py, M on a site of 222 symmetry in space group Ccca, true for CuCl(2) and CuBr(2) in particular, the copper(II) iodide adduct is of the form [Cu(py)(4)I]I·2py, Cu on a site of mm2 symmetry in space group Cmcm, and five-coordinate (square-pyramidal), the same cationic species also being found in 2[Cu(py)(4)I](I(3))·[(py)(2)Cu(µ-I)(2)Cu(py)(2)] (structurally defined). Bromide or N-thiocyanate may be substituted for the unbound iodide ion in the solvated salt, resulting in complexes which crystallize in space group Ccca, but with both anions and the metal atom disordered. In [Cu(py)(4)(I(3))(2)], a pair of long Cu···I contacts approach a square-planar Cu(py)(4) array. Assignments of the ν(CuN) and ν(CuX) (X = Br, I, SCN) bands in the far-IR spectra are made, the latter with the aid of analogous assignments for [Cu(py)(2)X(2)] (X = Cl, Br), which show a dependence of ν(CuX) on the Cu-X bond length that is very similar to that determined previously for copper(i) halide complexes. The structure of the adventitious complex [(trans-)(H(2)O)(py)(4)CuClCu(py)(4)](I(3))(3)·H(2)O is also recorded, with six- and five-coordinate copper atoms; rational synthesis provides [{Cu(py)(4)}(2)(µ-Cl)](I(3))(3)·H(2)O with one water molecule less. In [{Cu(py)(4)Cl}((∞|∞))](I(3))·3py, square pyramidal [Cu(py)(4)Cl](+) cations, assisted by Cl···Cu interactions, stack to give rise to infinite polymeric strings. Several of these compounds were prepared mechanochemically, illustrating the applicability of this method to syntheses involving redox reactions as well as to complex syntheses involving up to five components. The totality of results demonstrates that the [Cu(II)(py)(4)] entity can be stabilized in an unexpectedly diverse range of mononuclear and multinuclear complexes through the presence of lattice pyridine molecules, the bulky triiodide ion, or a combination of both.

Solid-state (15)N CPMAS NMR and computational analysis of ligand hapticity in rhodium(η-diene) poly(pyrazolyl)borate complexes.

Novel [Rh(η-diene)Tp(x)] complexes of sterically encumbered Tp(x) ligands (Tp(x) = Tp(4Bo), diene = cod, 1; nbd, 2; Tp(x) = Tp(4Bo,5Me), diene = cod, 3; nbd, 4; Tp(x) = Tp(a,3Me), diene = cod, 5; nbd, 6; Tp(x) = Tp(a*,3Me), diene = cod, 7; nbd, 8) have been prepared by treatment of [Rh(η-diene)(µ-Cl)](2) with TlTp(x) (Tp(x) in general, in detail: Tp(4Bo) = hydrotris(indazol-1-yl)borate, Tp(4Bo,5Me) = hydrotris(5-methyl-indazol-1-yl)borate, Tp(a,3Me) = hydrotris(3-methyl-2H-benz[g]-4,5-dihydroindazol-2-y1)borate, Tp(a*,3Me) = hydrotris(3-methyl-2H-benz[g]indazol-2-yl)borate), and characterized by analytical and spectral data (IR, (1)H, (11)B, and (13)C NMR solution). The structures adopted by [Rh(nbd)Tp(4Bo)] 2, [Rh(cod)Tp(4Bo,5Me)] 3, [Rh(nbd)Tp(a,3Me)] 6, [Rh(nbd)Tp(a*,3Me)] 8, and [Rh(nbd)Tp(a*,3Me*)] 8* (incorporating a borotropomeric ligand), have been investigated. Low steric hindrance between the ligands in 2 and 3 permits κ(3) coordination of the pyrazolylborate while the high steric encumbrance present in 6, 8, and 8* results in κ(2) ligands. The coordination modes of the ligands to the metal have also been established by (15)N CPMAS studies of selected ligands and their corresponding Rh complexes. These spectroscopic data are in agreement with the (15)N chemical shifts obtained by using quantum-chemical methods to assist reliable assignments of the experimental values, affording new insights into the extraction of structural information concerning the hapticity (κ(2) or κ(3)) of the poly(pyrazolyl)borate ligands to the Rh metal.

Conversion of C[triple bond]C to CO in alkynyl-metal complexes: oxidation of carbon chains capped by carbon-tricobalt clusters.

Treatment of Co(3)(mu(3)-CC[triple bond]CR)(mu-dppm)(CO)(7) with O(2) (air) in the presence of [FcH]PF(6) afforded Co(3){mu(3)-CC(O)R}(mu-dppm)(CO)(7) by the formal conversion -C[triple bond]C- + O-O --> >C-O + C[triple bond]O. In this way, complexes with R = Ph, Fc, and W(CO)(3)Cp, bis-clusters {Co(3)(mu-dppm)(CO)(7)}(2){mu(3):mu(3)-[[triple bond]C(O)(C[triple bond]C)C[triple bond]]}, {Co(3)(mu-dppm)(CO)(7)}(2){mu(3):mu(3)-[[triple bond]C(O)(C[triple bond]C)(x)C(O)C[triple bond, length as m-dash]]} (x = 1, 2), and {Co(3)(mu-dppm)(CO)(7)}(2){mu(3):mu(3)-[[triple bond]CC(O)C[triple bond, length as m-dash]CC(6)H(4)C[triple bond]CC(O)C[triple bond]]}, and heterometallic bis-clusters {Co(3)(mu-dppm)(CO)(7)}{mu(3):mu(3)-[[triple bond]CC(O)C[triple bond]CC[triple bond]]}{M(3)(mu-H)(3)(CO)(9)} (M = Ru, Os) have been prepared. Single-crystal XRD structure determinations of several products are reported together with that of precursor {Co(3)(mu-dppm)(CO)(7)}(2){mu(3):mu(3)-[[triple bond]C(C[triple bond]C)(2)C(6)H(4)(C[triple bond]C)(2)C[triple bond]]}.

Cluster control in oligouranyl complexes of p-t-butylcalix[8]arene.

Formation of uranyl ion complexes of p-t-butylcalix[8]arene by reaction of the calixarene with [UO(2)(dmso)(5)](2+) in the presence of various bases leads to the crystallisation of solids with interestingly different stoichiometry, involving both di- and tri-uranate oligomers bound to the calixarene in anionic species. In all, the calixarene hexa-anion is present in a virtually identical conformation, suggesting that conformational preferences of the ligand must be a major factor controlling the form of the bound oxo-metal complex. Hydrogen bonding to the anions does not appear to be prominent even in the presence of protonated amines and this may explain the formation of some remarkable cation/solvent/simple anion clusters found within the lattices.

Antiplasmodial activity of atisinium chloride from the Bhutanese medicinal plant, Aconitum orochryseum.

ETHNOPHARMACOLOGICAL RELEVANCE: The plant Aconitum orochryseum Stapf. (Ranunculaceae) is employed together with other plants in Bhutanese traditional medicine and is indicated for malaria-associated fever. AIM OF THE STUDY: To study the in vitro antiplasmodial activity of atisinium chloride, the major alkaloid from Aconitum orochryseum. MATERIALS AND METHODS: Atisinium chloride was extracted and purified from aerial parts of Aconitum orochryseum and its structure and absolute configuration confirmed by single crystal X-ray crystallography. The crude methanol extract, crude alkaloid fraction, and atisinium chloride were tested for in vitro antiplasmodial activity against the malarial Plasmodium falciparum strains TM4/8.2 (TM4; wild type) and K1CB1 (K1; chloroquine and antifolate resistant). RESULTS: The diterpenoid alkaloid atisinium chloride was shown to have moderate antiplasmodial activities with IC(50) values of 4 microM and 3.6 microM, respectively against the TM4 strain and the K1 strain of Plasmodium falciparum. CONCLUSIONS: Our studies provide the first evidence in support of one of the indicated treatments with Aconitum orochryseum in Bhutanese traditional medicine. This alkaloid also represents a potential new antimalarial structural lead.

Novel complexes of silver(I) sulfate with 1-methylimidazole-2-thione: structures and vibrational spectroscopy.

Crystallization of silver(I) sulfate with the ligand 1-methylimidazole-2-thione ('Hmimt') from aqueous solution, instead of yielding the expected 1:6 Ag(2)SO(4):Hmimt complex analogous to numerous other Ag(2)SO(4):thiourea-based ligand (1:6) complexes, has resulted in novel polymeric forms, one of unusual stoichiometry. Ag(2)SO(4):Hmimt (1:4) (x H(2)O) is of the form [...(mu-Hmimt)(2)Ag(mu-Hmimt)(2)Ag...](infinity|infinity)(SO(4)), with a one-dimensional polymeric cation. Ag(2)SO(4):Hmimt (3:8) (x 9 1/2 H(2)O) is a polymeric sheet structure containing Ag(12)(SO(4))(6)(Hmimt)(15) kernels linked by Hmimt ligands. The IR spectra of these compounds show unusually large shifts of the nu(NH) band due to the presence of N-H...O hydrogen bonding involving the N-H group of the ligand and the sulfate oxygen atoms. The complexes were also readily prepared by the solvent-assisted mechanochemical method, and the utility of this method for the preparation of deuterium-exchanged products for assistance in the assignment of the IR spectra is illustrated.

Structural and spectroscopic studies of some adducts of silver(I) halides with thiourea and N-ethyl substituted thioureas.

Syntheses, single crystal X-ray structural and spectroscopic characterizations are described for a variety of adducts of silver halides with thiourea ('tu'), N-ethylthiourea ('ettu' = EtNH.CS.NH(2)) and N,N'-diethylthiourea ('detu' = EtNH.CS.EtNH). This study greatly extends our knowledge of the complex chemistry of silver(i) halides with tu. The unexpected diversity of composition of such complexes was initially revealed by the powerful mechanochemical/IR method and the structures of several of the new complexes were determined by X-ray crystallographic studies of samples subsequently prepared from aqueous solution. Structural characterizations provide extensive geometrical data for (mononuclear 1 : 3) [XAg(xtu)(3)] arrays (xtu = ettu, detu; X = Cl, Br, I), assisting vibrational spectroscopic assignments. With the parent tu ligand, binuclear ionic forms are obtained: [tu(2)Ag(mu-tu)(2)Agtu(2)]X(2), the chloride as the dihydrate and the bromide as a di(thiourea) dihydrate adduct. With tu 1 : 2 complexes are defined for X = Cl, Br, as isomorphous one-dimensional polymers; AgCl:tu (1 : 1) is a two-dimensional net with six-membered Ag(3)S(3) rings and terminal chloride. Intermediate stoichiometries are defined in AgBr:tu (2 : 3), a one-dimensional polymer of Ag(2)S(2) rhombs linked at the silver atoms, while [Cl(2)Ag(3)(tu)(4)](NO(3)).H(2)O is also a one-dimensional polymer in which chloride and thiourea sulfur atoms link six-membered Ag(3)S(3) rings. Diagnostic bands in the IR and far-IR spectra of all of the synthesized complexes are assigned and interpreted in relation to the structures.

Structural and electrochemical studies of Co(III) cage amine complexes with pendent thienylmethylamino groups.

Various 2- and 3-thienylmethylamino-substituted cobalt(III) cage amine complexes, prepared with the objective of obtaining cage-functionalized polythienyls, have been found to be resistant to oxidative polymerization by both electrochemical and chemical procedures. X-ray structure determinations indicate that there is negligible perturbation of the physical dimensions of the thiophene moieties by the cage substituents and thus that the resistance to polymerization must be associated with the high positive charge carried by these substituents.