Pramesh N. Kapoor

High surface area homogeneous nanocrystalline bimetallic oxides obtained by hydrolysis of bimetallic µ-oxo alkoxides

Homogeneously dispersed bimetallic oxides in nanocrystalline or amorphous forms, of the type MAl2O4 (where M = Mg, Ca, Mn, Co, Fe, and Zn) were prepared from bimetallic oxo-bridged alkoxides [(RO)2Al–O–M–O–Al(OR)2], where the Al–O–M–O–Al bonds were not hydrolytically cleaved. This approach yields hydroxides [(HO)2Al–O–M–O–Al(OH)2] which, upon thermal dehydration, yield oxides [OAl–O–M–O–AlO], such that M is homogeneously dispersed with an empirical formula of MAl2O4. These materials were obtained in high surface area forms and were characterized by X-ray diffraction, electron microscopy, surface area analyses, and solid-state 27Al NMR. Comparative studies of the hydrolysis of alkoxo-bridged alkoxides yielded mixed metal oxide phases with lower surface areas.

Peptidyl Prolyl Isomerase, Pin1 is a Potential Target for Enhancing the Therapeutic Efficacy of Etoposide

The peptidyl prolyl isomerase (Pin1) that induces cis-trans isomerization of the peptide bond involving serine/threonine-proline has recently been shown to regulate the activity of many phosphoproteins including the ones involved in damage response pathways. We investigated Pin1 as a potential target for enhancing the efficacy of anticancer therapy by studying the effects of juglone, a Pin1 inhibitor on the cytotoxicity of etoposide (a widely used anticancer drug that targets topoisomerase IIα) in human tumor cell lines. Treatment of cells with juglone synergistically enhanced the cytotoxicity of etoposide (loss of clonogenicity) with a tenfold increase when etoposide treatment preceded juglone exposure. On the other hand, the toxicity was than additive when the treatment protocol was reversed (i.e exposure to juglone followed by etoposide treatment). This suggests that Pin1 inhibition possibly reduces the induction of initial DNA damage by etoposide, which was supported by a decrease in the levels of chromatin bound topoIIα. Increase in the etoposide induced toxicity by juglone appeared to be mainly due to enhanced mitotic cell death linked to cytogenetic damage, although a moderate increase in interphase (apoptotic) death was also evident as revealed by DNA degradation (hypodiploid population and TUNEL assay). Since the level of Pin1 is found to be higher in cancer cells, this enzyme could be a potential target for developing an adjuvant to enhance the efficacy of anticancer therapies.

Synthesis of new bimetallic [Al(III), Mg(II)]-μ-oxoisopropoxide and its β-diketone derivatives

A new bimetallic-μ-oxoisopropoxide [MgO2Al2(OPri)4] has been synthesized by thermal condensation of magnesium acetate (1 mol) and aluminium isopropoxide (2 mol) in refluxing decalin. The isopropoxy substitution reaction of this bimetallic [Al(III), Mg(II)]-μ-oxoisopropoxide with various β-diketones in molar ratios 1 : 1, 1 : 2 and 1 : 3 yielded compounds of the type [MgO2Al2(OPri)3(L)], [MgO2Al2(OPri)2(L)2] and [MgO2Al2(OPri)(L)3], respectively; where HL = HAcAc (acetyl acetone), HBzAc (benzoyl acetone) and HThTFA(2-thenoyl trifluoroacetone). The μ-oxo compound and its derivatives were characterized on the basis of elemental analysis, IR, 1H NMR 27Al NMR and molecular weight measurements.

Molecular interaction of diaryl and dicyclohexyl phosphine oxides with some lanthanide(III) chlorides

Abstract Lanthanide chlorides form six-coordinate octahedral adducts of the type [LnCl 3 (R 2 P(O)H) 3 ] (where Ln = La, Pf, Nd, Sm, Eu, Gd, Tb, Dy or Yb and R = C 6 H 11 , p -CH 3 C 6 H 4 , p - or m -CF 3 C 6 H 4 ) when interacted with diaryl and dicyclohexyl phosphine oxides in dry ethanol. Complexes were re-crystallised from n-hexane and on the basis of elemental analysis, infrared, and 31 p NMR spectral studies, it is concluded that these phosphine oxides coordinate to the lanthanide metal atom through the oxygen atom which shows the greatest affinity for lanthanides in these adducts.

1,2-Bis(di-p-tolylphosphino)ethane complexes of Group VI metal carbonyls

Abstract New complexes of the type [M(CO) 4 (dptpe)] (M = Cr, Mo, W) have been isolated from the reaction of the ligand, 1, 2-bis(di- p -tolylphosphino)ethane (dptpe) with Group VI metal hexacarbonyls in a suitable solvent such as methylcyclohexane. The resulting [M(CO) 4 (dptpe)] complexes on treatment with an excess of pyridine produces the mixed ligand complexes [M(CO) 3 (py)(dptpe)], whereas the reaction of [XMo(CO) 2 (η 3 -allyl)(MeCN 2 )] (X = Cl, Br) with dptpe gives [XMo(CO) 2 (η 3 -allyl)(dptpe)]. The formulation of the structures of these complexes follows from elemental analyses and 1 H NMR, 31 P{ 1 H} NMR and IR spectral studies. Carbonyl force constants have been calculated from the ν(CO) stretching frequencies by the Cotton and Kraihanzel method.

Nickel(II), palladium(II) and platinum(II) complexes of trans spanning ditertiary phosphine 3,3′-oxybis- [(di-meta-tolylphosphino)methyl]benzene

Abstract The synthesis of the trans -spanning bidentate diphosphine ligand, 3,3′-oxybis-(di- meta -tolylphosphino)methyl]benzene (I) and its complexes with Ni II , Pd II and Pt II are described. The ligand I forms monomeric trans square planar complexes [MX 2 (I)] (M = Ni, Pd or Pt, X = Cl or X = NCS in case of Ni). 31 P and 1 H NMR parameters are reported.

Synthesis of phenylmagnesium carboxylates

Abstract The first phenylmagnesium carboxylates, C6H5MgOOCR·THF, have been made by reaction of phenylmagnesium bromide with the sodium salt of carboxylic acids [RCOONa {where R = CH3, ClCH2, Cl2CH, Cl3C, CH3CH2, (CH3)2CH, C6H5CH2 and CH3(CH2)3CH2}]. All these derivatives are white or pale yellow solids, soluble in polar solvents. The carboxylates have been characterized by elemental analysis, conductance measurements, and spectral studies (1H NMR and IR). The IR data suggest that carboxylate group acts as a bridging bidentate ligand.

η3-allyl)dicarbonylmolybdenum(II) complexes of the unsymmetrical ditertiary phosphines Ph2PCH2CH2P(C6H4X)2 (X = m-F, p-F or m-CF3)

Abstract Complexes of the type [XMo(CO) 2 (η 3 -C 3 H 5 )(PP′)] (X  Cl or Br; PP′  R 2 PCH 2 CH 2 PPh 2 ; R = m -FC 6 H 4 ( 1a ), p -FC 6 H 4 ( 1b ), m -CF 3 C 6 H 4 ( 1c )) have been prepared from the reaction of [XMo(CO) 2 (η 3 -C 3 H 5 )(MeCN) 2 ] with the relevant ditertiary phosphines in acetone. From their 1 H NMR and IR data these complexes have been assigned essentially octahedral structures in which the allyl moiety is trans to be unidentate anion, and the two cis -carbonyl groups and two phosphorus donor atoms of the bidentate ligand are approximately coplanar. CO force constants have been calculated.

Preparation and Characterisation of Tantalum(V) β-Diketonates (Part II)

Abstract Reactions of tantalum pentaethoxide with p-haloarylsubstituted β-diketones as well as 2-thenoyltrifluoroacetone were carried out using different molar ratios. Compounds of the type [Ta(OEt)5-n(L)n], (where L = p-fluoro-, p-chloro-, p-bromobenzoylacetone and 2-thenoyltrifluoroacetone; n = 1, 2 or 3), have been isolated and characterised by elemental analysis, molecular weight determinations and spectral studies like i.r., and 1H n.m.r. Alcoholysis reactions with tertiary butanol were also carried out.

SOME TRANSITION METAL COMPLEXES OF NOVEL DITERTIARY PHOSPHINE: [2-{Di(p-TOLYL)PHOSPHINO}-ETHYL] DIPHENYLPHOSPHINE

Abstract The new chelating ditertiary phosphine (pptpf) forms low spin, diamagnetic, square-planar complexes of the type [M(pptpf)X2] (where M=Ni(II), Pd(II) or Pt(II); X=Cl, Br, I or NCS) when treated with corresponding metal salts. Group VI metal hexacarbonyls also react with the ligand (pptpf) to yield diamagnetic, octahedral complexes of type [M(CO)4(pptpf)] (where M=Cr, Mo or W). These complexes have been characterised on the basis of their elemental analysis, 1H n.m.r., electronic, infrared spectral measurements, electrical conductance and magnetic susceptibilities data. In all the complexes the ligand (pptpf) acts as a chelating ditertiary phosphine.