Georgina M. Rosair

Copper(II) Complexes of Salicylic Acid Combining Superoxide Dismutase Mimetic Properties with DNA Binding and Cleaving Capabilities Display Promising Chemotherapeutic Potential with Fast Acting in Vitro Cytotoxicity against Cisplatin Sensitive and Resistant Cancer Cell Lines

The complexes [Cu(salH)(2)(H(2)O)] (1), [Cu(dipsH)(2)(H(2)O)] (2), {Cu(3-MeOsal)(H(2)O)(0.75)}(n) (3), [Cu(dipsH)(2)(BZDH)(2)] (4), [Cu(dipsH)(2)(2-MeOHBZDH)(2)]·EtOH (5), [Cu(sal)(phen)] (6), [Cu(dips)(phen)]·H(2)O (7), and [Cu(3-MeOsal)(phen)]·H(2)O (8) (salH(2) = salicylic acid; dipsH(2) = 3,5-diisopropylsalicylic acid; 3-MeOsalH(2) = 3-methoxysalicylic acid; BZDH = benzimidazole; 2-MeOHBZDH = 2 methanolbenzimidazole and phen =1,10-phenanthroline) were prepared and characterized. Structures of 4, 5, and 8 were determined by X-ray crystallography. Compounds 1-8 are potent superoxide dismutase mimetics, and they are inactive as inhibitors of COX-2 activity. Compounds 1, 4, and 5 exhibit moderate inhibition of COX-1. Complexes 6-8 display rapid micromolar cytotoxicity against cisplatin sensitive (breast (MCF-7), prostate (DU145), and colon (HT29)) and cisplatin resistant (ovarian (SK-OV-3)) cell lines compared to 1-5, and they exhibit potent in vitro DNA binding and cleavage capabilities.

Synthesis and characterization of diorganotin(IV) complexes of tetradentate Schiff bases: Crystal structure of n-Bu2Sn(Vanophen)

Abstract Diorganotin(IV) complexes of the general formula R2SnL (R=Ph, n-Bu and Me) have been prepared from diorganotin(IV) dichlorides (R2SnCl2) and tetradentate Schiff bases (H2L) containing N2O2 donor atoms in the presence of triethylamine in benzene. The Schiff bases, H2L, were derived from salicylaldehyde, 3-methoxysalicylaldehyde (o-vanillin), 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and diamines such as o-phenylenediamine and 1,3-propylenediamine. The complexes were characterized by IR, NMR (1H, 13C, 119Sn) and elemental analysis. The structure of the complex, n-Bu2Sn(Vanophen), was determined using single crystal X-ray diffraction. The tin atom has a distorted octahedral coordination, with the Vanophen ligand occupying the four equatorial positions and the n-butyl groups in the trans axial positions. Six-coordinated distorted octahedral structures have been proposed for all diorganotin(IV) complexes studied here, as they possess similar spectroscopic data.

Self-assembly of carborane molecules via C–H⋯I hydrogen bonding: the molecular and crystal structures of 3-I-1,2-closo-C2B10H11

The crystal structure of 3-I-1,2-closo-C2B10H11 reveals that molecules are arranged as infinite head-to-tail zig-zag double chains held together by C–H⋯I hydrogen bonding.

Room-temperature C-C bond cleavage of an arene by a metallacarborane.

The activation and cleavage of C C bonds by transition-metal species is an area of intense current interest, and, although they are still relatively rare, a number of systems that afford the breaking of C C single bonds are known. In contrast, the cleavage of aromatic C C bonds is considered to be extraordinarily difficult. Six-carbon aromatic rings can be cleaved in the gas phase at high temperatures, whereas under less extreme conditions such rings are cleaved by enzymes, an important part of the global carbon cycle. However, there are very few reports of low-temperature cleavage reactions of aromatic rings in nonbiological systems. Of the examples that are known, (biomimetic) oxidative cleavage is the more common process but is generally regarded as difficult to control, whereas reductive cleavage is much more rare. However, both oxidative and reductive cleavage reactions typically involve significant initial chemical modification of the aromatic ring. Sattler and Parkin recently described the cleavage of a C C bond in an aromatic heterocycle (a quinoxaline) at 90 8C. We report herein the unprecedented cleavage of an aromatic C C bond in a simple arene at room temperature by a metallacarborane without other chemical modification to the arene. Treatment of 1,1’-bis(o-carborane), 1-(1’,2’-closoC2B10H11)-2-closo-C2B10H11 (Figure 1), with an excess of Li in THF in the presence of naphthalene and subsequent reaction with [{Ru(p-cymene)Cl2}2] (p-cymene = 1-iPr,4MeC6H4), affords the dark red metallacarborane 1-(1’,2’closo-C2B10H11)-4-{C10H14Ru(p-cymene)}-4,1,6-closoRuC2B10H11 as the only isolable product (in ca. 20% yield) after workup (involves TLC methods). The product was characterized by mass spectroscopy, H and B{H} NMR spectroscopy, and ultimately by single-crystal X-ray diffraction. In the H spectrum there are, in addition to broad CcageH resonances at approximately d = 4.7 and 2.2 ppm, the normal resonances assigned to the CH3C6H4CHMe2 protons of a h -pcymene ligand in an asymmetric complex (four dd between d = 6.5 and 5.5 ppm with J and J couplings of ca. 6 Hz and 1.5 Hz, respectively). However, the signals normally assigned to the CH3C6H4CHMe2, CH3C6H4CHMe2, and CH3C6H4CHMe2 protons all appear doubled. In addition there are two high-frequency doublet resonances (d = 9.6, 9.4 ppm) and two additional resonances (d = 4.5, 4.1 ppm) which appear as apparent triplets. Collectively these data suggest that there are two different C10H14 units in the product; one is a regular h-p-cymene ligand but the other appears to have been subjected to a major structural change. The B{H} spectrum is relatively uninformative with nine resonances between d = 6 and 25 ppm, including a multiple signal at d = 10.6 ppm that accounts for ten boron atoms. The mass spectrum confirms the molecular formula as C25H50B20Ru2 (envelope centered on m/z 757) which implies bis(carborane) plus two {RuC10H14} units, but, as is evident from the NMR spectra, the molecule is asymmetric and one of the p-cymene ligands has been substantially altered. A crystallographic study resulted in the molecular structure shown in Figure 2. Figure 3 shows an alternative view of the central part of the molecule. The molecule consists of a 13-vertex docosahedral ruthenacarborane (cage A) with a 4,1,6-RuC2B10 architecture, the

Isolation of four new CoII/CoIII and NiII complexes with a pentadentate Schiff base ligand: syntheses, structural descriptions and magnetic studies

In this paper we report the temperature and pH dependent syntheses and systematic characterization of four new Co(II)/Co(III) and Ni(II) complexes with a pentadentate Schiff base ligand H(3)L obtained by condensing 1,3,-diaminopropan-2-ol with 2-hydroxyacetophenone in 1:2 molar ratio. The room temperature syntheses involving Co(II) and Ni(II) nitrates and the ligand H(3)L lead to the isolation of the dinuclear species [Co(2)L(2)(H(2)O)] (1), and the mononuclear complex [Ni(LH)] (3), respectively, whereas refluxing at basic pH leads to the tetranuclear complexes, [Co(II)(2)Co(III)(2)L(2)(μ(3)-OMe)(2)(NO(3))(H(2)O)(2)]NO(3)·2(H(2)O) (2), and [Ni(4)L(2)(μ(3)-OMe)(2)(H(2)O)(2)]·2H(2)O (4). 1 is found to be a simple mono alkoxo-bridged Co(III) dinuclear species, whereas 2 and 4 are both rhomb-like tetrameric complexes with double oxo bridges and μ(3)-methoxo bridges, derived from the methanol solvent, in an open dicubane arrangement. Moreover 2 shows six coordinate ordered Co(II) and Co(III) ions and 4 has both six- and five-coordinate Ni(II) centers. Compound 3 is assigned a tentative mononuclear structure based on IR, UV-Vis spectroscopic, (1)H-NMR and ESI mass study results and is supposed to have one Ni(II) center coordinated with a ligand fragment in square planar geometry. The variable temperature magnetic susceptibility study for 2 and 4 is performed which indicate for both 2 and 4 the presence of intracluster dominant ferromagnetic interactions.

Weak Interactions Modulating the Dimensionality in Supramolecular Architectures in Three New Nickel(II)-Hydrazone Complexes, Magnetostructural Correlation, and Catalytic Potential for Epoxidation of Alkenes under Phase Transfer Conditions

Three different ONO donor acetyl hydrazone Schiff bases have been synthesized from the condensation of acetic hydrazide with three different carbonyl compounds: salicylaldehyde (HL(1)), 2-hydroxyacetophenone (HL(2)), and 2, 3-dihydroxybenzaldehyde (HL(3)). These tridentate ligands are reacted with Ni(OOCCF(3))(2)·xH(2)O to yield three new Ni(II) complexes having distorted octahedral geometry at each Ni center: [Ni(L(1))(OOCCF(3))(CH(3)OH)](2) (1), [Ni(L(2))(OOCCF(3))(H(2)O)](2) (2), and [Ni(L(3))(L(3)H)](OOCCF(3))(H(2)O)(1.65)(CH(3)OH)(0.35) (3). The ligands and the complexes have been characterized by elemental analysis and IR and UV-vis spectroscopy, and the structures of the complexes have been established by single crystal X-ray diffraction (XRD) study. 1 and 2 are centrosymmetric dinuclear complexes and are structural isomers whereas 3 is a bis chelated cationic monomer coordinated by one neutral and one monoanionic ligand. O-H···O hydrogen bonds in 3 lead to the formation of a dimer. Slight steric and electronic modifications in the ligand backbone provoke differences in the supramolecular architectures of the complexes, leading to a variety of one, two, and three-dimensional hydrogen bonded networks in complexes 1-3 respectively. Variable temperature magnetic susceptibility measurements reveal that moderate antiferromagnetic interactions operate between phenoxo bridged Ni(II) dimers in 1 and 2 whereas very weak antiferromagnetic exchange occurs through hydrogen bonding and π-π stacking interactions in 3. All complexes are proved to be efficient catalysts for the epoxidation of alkenes by NaOCl under phase transfer condition. The efficiency of alkene epoxidation is dramatically enhanced by lowering the pH, and the reactions are supposed to involve high valent Ni(III)-OCl or Ni(III)-O· intermediates. 3 is the best epoxidation catalyst among the three complexes with 99% conversion and very high turnover number (TON, 396).

Synthesis, characterisation and structural studies of [Cu(dach)(μ-NCS)(NCS)]n and [Cu(dach)2(N3)]ClO4 (dach = 1,4-diazacycloheptane)

Abstract A new singly bridging complex [Cu(dach)(μ-NCS)(NCS)] n (dach=1,4-diazacycloheptane) has been synthesised and its crystal structure determined. There are many examples of double NCS bridged polymeric chains, but fewer singly bridged ones. IR, ESR and temperature variable magnetic studies are described but no magnetic interaction was found between the copper centres. [Cu(dach) 2 (N 3 )]ClO 4 has also been characterised by IR, ESR spectra and magnetic studies. The crystal structure determination shows that it is a penta-coordinated monomeric species with an axially coordinated azide linked to the perchlorate counterion by hydrogen bonding.

The ‘1,2 to 1,2’ cage carbon isomerisation in bisphosphine carbanickelaboranes: synthesis and spectroscopic and crystallographic characterisation of 1,2-Ph2-4,4-(PMe2Ph)2-4,1,2-closo-NiC2B9H9, 1,2-Ph2-4,4-(PEt3)2-4,1,2-closo-NiC2B9H9 and 1,2-Ph2-4-(dppe)-4,1,2-closo-NiC2B9H9 ☆

Abstract Reaction between Tl 2 [7,8-Ph 2 -7,8- nido -C 2 B 9 H 9 ] and NiCl 2 (PR 3 ) 2 in CH 2 Cl 2 affords three new carbanickelaboranes; 1, R 3 =Me 2 Ph; 2 , R=Et; 3 , (PR 3 ) 2 =dppe. The molecular structures of all these compounds were established as 1,2-Ph 2 -4,4-(PR 3 ) 2 -4,1,2- closo -NiC 2 B 9 H 9 by spectroscopic and crystallographic techniques. It is presumed that the first (transient) products of the reactions are the compounds 1,2-Ph 2 -3,3-(PR 3 ) 2 -3,1,2- closo -NiC 2 B 9 H 9 which rearrange to the observed species by a ‘1,2 to 1,2’ C cage atom isomerisation to relieve intramolecular overcrowding.

Gold(I)-Catalyzed Addition of Thiols and Thioacids to 3,3-Disubstituted Cyclopropenes

Gold(I)-catalyzed reactions of thiols, thiophenols, and thioacids with 3,3-disubstituted cyclopropenes occur in a regioselective and chemoselective manner to produce either vinyl thioethers or primary allylic thioesters in good yields. A survey of commonly used gold(I) catalysts shows Echavarrens cationic gold(I) catalyst to be most tolerant of deactivation by sulfur. A novel digold with bridging thiolate complex is characterized by X-ray crystallography, shedding light on a possible deactivation pathway.

Concise routes to pyrazolo[1,5-a]pyridin-3-yl pyridazin-3-ones

Cycloaddition of pyridine N-imine with 6-alkyl-4-oxohex-5-ynoates followed by condensation with hydrazine provides concise access to pharmacologically active 6-(pyrazolo[1,5-a]pyridin-3-yl)pyridazinones. For the first time alkynyl heterocycles are also shown to be effective dipolarophiles for pyridine N-imine, and analogous compounds can be accessed directly in modest yields through the reaction of 6-(alkyn-1-yl)pyridazin-3-one derivatives.