Meena Nagar

SYNTHESIS, CHARACTERIZATION AND ANTIOXIDANT ACTIVITY OF SOME TRANSITION METAL COMPLEXES WITH TERPENOID DERIVATIVES

A series of transition metal complexes of Fe(III), Co(II) and Cu(II) containing the bidentate N,O and N,S donor ligand, camphor semicarbazone (1,7,7-trimethylbicyclo [2,2,1]heptanesemicarbazone, TBHSC) and camphor thiosemicarbazone (1,7,7- trimethylbicyclo [2,2,1]heptanethiosemicarbazone, TBHTSC) have been synthesized and characterized by elemental analysis, molar conductance measurement and various spectral studies (IR, electronic and FAB Mass) and thermogravimetric analysis (TGA). All the metal complexes (1-8) are [M(LH)Cl 2 ] and [M(LH) 2 Cl 2 ] type, where M = Fe(III), Co(II) and Cu(II); LH = TBHSC and TBHTSC. TBHSC and TBHTSC act as neutral bidentate ligands in all the complexes. FAB mass spectroscopic studies of the three representative complexes (1), (2), (4), (5) and (8) suggest their monomeric nature. The proposed geometries of the complexes were octahedral geometry for 1:2 complexes, square planar for 1:1 complexes and distorted octahedral for Cu(II) complexes (1:2). The free radical scavenging activity of newly synthesized ligands (TBHSC, TBHTSC) and their metal complexes have been determined at the concentration range of 50-1000 µg/ml by means of their interaction with the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). All the compounds have shown encouraging antioxidant activities. The least IC 50 value (111.0 µg/ml) for compound (5) showed the potent scavenging property compared to other test compounds.

Molecular precursors for the preparation of homogenous zirconia-silica materials by hydrolytic sol-gel process in organic media. Crystal structures of [Zr{OSi(O(t)Bu)3}4(H2O)2]·2H2O and [Ti(O(t)Bu){OSi(O(t)Bu)3}3].

[Zr(OPr(i))(4)·Pr(i)OH] reacts with [HOSi(O(t)Bu)(3)] in anhydrous benzene in 1:1 and 1:2 molar ratios to afford alkoxy zirconosiloxane precursors of the types [Zr(OPr(i))(3){OSi(O(t)Bu)(3)}] (A) and [Zr(OPr(i))(2){OSi(O(t)Bu)(3)}(2)] (B), respectively. Further reactions of A or B with glycols in 1:1 molar ratio afforded six chemically modified precursors of the types [Zr(OPr(i))(OGO){OSi(O(t)Bu)(3)}] (1A-3A) and [Zr(OGO){OSi(O(t)Bu)(3)}(2)] (1B-3B), respectively [where G = (-CH(2)-)(2) (1A, 1B); (-CH(2)-)(3) (2A, 2B) and (-CH(2)CH(2)CH(CH(3)-)} (3A, 3B)]. The precursors A and B are viscous liquids, which solidify on ageing whereas the other products are all solids, soluble in common organic solvents. These were characterized by elemental analyses, molecular weight measurements, FAB mass, FTIR, (1)H, (13)C and (29)Si-NMR studies. Cryoscopic molecular weight measurements of all the products, as well as the FAB mass studies of 3A and 3B, indicate their monomeric nature. However, FAB mass spectrum of the solidified B suggests that it exists in dimeric form. Single crystal structure analysis of [Zr{OSi(O(t)Bu)(3)}(4)(H(2)O)(2)]·2H(2)O (3b) (R(fac) = 11.9%) as well as that of corresponding better quality crystals of [Ti(O(t)Bu){OSi(O(t)Bu)(3)}(3)] (4) (R(fac) = 5.97%) indicate the presence of a M-O-Si bond. TG analyses of 3A, B, and 3B indicate the formation of zirconia-silica materials of the type ZrO(2)·SiO(2) from 3A and ZrO(2)·2SiO(2) from B or 3B at low decomposition temperatures (≤200 °C). The desired homogenous nano-sized zirconia-silica materials [ZrO(2)·nSiO(2)] have been obtained easily from the precursors A and B as well as from the glycol modified precursors 3A and 3B by hydrolytic sol-gel process in organic media without using any acid or base catalyst, and these were characterized by powder XRD patterns, SEM images, EDX analyses and IR spectroscopy.

Sol–gel synthesis of highly pure α-Al2O3 nano-rods from a new class of precursors of salicylaldehyde-modified aluminum(III) isopropoxide. Crystal and molecular structure of [Al(OC6H4CHO)3]

Reactions of aluminum isopropoxide with salicylaldehyde in 1 : 1, 1 : 2 and 1 : 3 molar ratios in anhydrous benzene yield complexes of the type [(OPri)3−nAl(OC6H4CHO)n] {where n = 1(1); n = 2 (2); n = 3 (3)}. All the products are yellow solids and are soluble in common organic solvents. They were characterized by elemental analysis, ESI-mass spectrometry, FT-IR and 1H, 13C and 27Al NMR studies. The ESI-mass spectral studies indicate dimeric nature for (1) and (2) and monomeric nature for compound (3). Crystal and molecular structures of [Al(OC6H4CHO)3] (3) suggest that salicylaldehyde ligands bind to the metal in a side-on dihapto η2-(O,O) manner, leading to the formation of a hexa-coordinated environment around the aluminum atom. Powder XRD, SEM image, and EDX analysis appear to indicate formation of nano-sized rods for precursor (3). Sol–gel hydrolysis of all the precursors Al(OPri)3, (1), (2) and (3) followed by sintering at 1100 °C yielded α-Al2O3 (a), (b), (c) and (d), respectively. The powder X-ray diffraction patterns and the SEM images of all the oxides exhibit nano-sized microcrystalline morphology for (a) and mixed platelike nano-rod morphology for (b), (c) and (d). The EDX and TEM studies of (d) also corroborate the formation of α-Al2O3. The IR spectral studies of all the oxides indicate the formation of pure α-alumina, a versatile ceramic oxide known for exhibiting a wide variety of applications in engineering and biomedical areas.

Glycol modified cis -diisopropoxy- bis ( N -phenylsalicylideneiminato)zirconium(IV): syntheses, characterization and low temperature transformation to nanocrystalline zirconia

Zr(OPri)4·PriOH reacts with N-phenylsalicylideneimine in anhydrous benzene in 1 : 2 molar ratio to afford [Zr{O(C6H4)CH=NPh}2{OPri}2] (1). Further reactions of 1 with various glycols yield heteroleptic complexes of the type [Zr{O(C6H4)CH=NPh}2{O–G–O}] [where–G–= (CH2)2 (2), (CH2CHCH3) (3), (CH3CHCHCH3) (4), (CH2CHC2H5) (5), (CH2)3 (6), (CH2CH2CHCH3) (7), and (CH2)6 (8)]. All new derivatives have been characterized by elemental analyses, FTIR and NMR (1H and 13C{1H}) studies. FAB mass spectra of 1 and 7 revealed the monomeric nature of these complexes. Complete hydrolyses and low temperature transformations of 1 and 7 using Sol-Gel technique formed tetragonal phase of ZrO2 at 700°C, whereas transformation of tetragonal to monoclinic phase occurred at 900°C. SEM observations of these samples indicate formation of agglomerates of nanocrystalline zirconia (Scherer analysis).

Transition metal complexes with N, S donor ligands as synthetic antioxidants: synthesis, characterization and antioxidant activity.

Transition metal complexes containing bidentate N, S donor ligands i.e., carvone thiosemicarbazone [(RS)-5-isopropenyl-2-methylcyclohex-2-en-1-one thiosemicarbazone (IPMCHTSC)] and carvone N1-phenylthiosemicarbazone [(RS)-5-isopropenyl-2-methylcyclohex-2-en-1-one phenylthiosemicarbazone (IPMCHPhTSC)] have been synthesized. All the metal complexes (1–8) have been characterized by elemental analysis, molar conductance measurement and various spectral studies [infrared (IR), electronic, fast-atom bombardment (FAB) mass and NMR (for ligands)] and thermogravimetric analysis. FAB mass spectroscopic studies of (1), (3), (4), (5), (6) (7), and (8) suggest their monomeric nature. Metal complexes are [M(LH)Cl2] and [M(LH)2Cl2] type, where M = Fe(III), Co(II), and Cu(II) and LH = IPMCHTSC and IPMCHPhTSC. The proposed geometries of the complexes were octahedral for 1:2 complexes, square planar for 1:1 complexes and distorted octahedral for Cu(II) complexes (1:2). The free radical scavenging activity of ligands (IPMCHTSC and IPMCHPhTSC) and their metal complexes have been determined at the concentration range of 10–400 μg/mL by means of their interaction with the stable free radical 2,2′-diphenyl-1-picrylhydrazyl and 5–200 μg/mL by 2,2′-Azinobis-3-ethylbenzothiazoline-6-sulphonic acid. All the compounds have shown encouraging antioxidant activities.

Synthesis, characterization and antimicrobial activities of some mixed ligand complexes of Co(II) with thiosemicarbazones and N-protected amino acids

The reaction of cobalt(II) chloride with a new class of thiosemicarbazones viz; cis-3,7-dimethyl-2,6-octadienthiosemicarbazone(CDOTSC; L1H) and 3,7-dimethyl-6-octenethiosemicarbazone (DOTSC; L2H) and N-phthaloyl derivative of DL-glycine(A1H), L-alanine(A2H) or L-valine(A3H) in 1:1:1 molar ratio in dry refluxing ethanol have been studied. All the isolated complexes have the general composition [Co(L)(A)]. Tentative structures are proposed for these complexes based upon elemental analysis, electrical conductances, magnetic moment, molecular weight determination and spectral (IR, electronic) studies.The ligands and Co(II) complexes have been tested for their antibacterial and antifungal activities against three bacterial strains S. aureus, B. subtilis, E. coli and two fungal strains F. moniliformae and M. phaseolina. Attempts have been made to establish a correlation between the antibacterial and antifungal activity and the structures of products.

Synthesis, Structural, and Antibacterial Studies of Some Mixed Ligand Complexes of Zn(II), Cd(II), and Hg(II) Derived From Citral Thiosemicarbazone and N-Phthaloyl Amino Acids

A series of new mixed ligand complexes of Zn(II), Cd(II), and Hg(II) with cis-3,7-dimethyl-2,6-octadienthiosemicarbazone (CDOTSC; LH) and N-phthaloyl amino acids (AH) have been synthesized by the reaction of metal dichloride with ligands CDOTSC and N-phthaloyl derivative of DL-glycine (A1H), L-alanine (A2H), or L-valine (A3H) in a 1:1:1 molar ratio in dry refluxing ethanol. All the isolated complexes have the general composition [M(L)(A)]. The plausible structure of these newly synthesized complexes has been proposed on the basis of elemental analyses, molar conductances, molecular weight measurement, and various spectral (IR, 1H NMR, and 13C NMR) studies, and four coordinated geometries have been assigned to these complexes. All the complexes and ligands have been screened for their antibacterial activity.

Synthesis and structural characterization of some binuclear acetylacetone and Schiff’s base complexes containing aluminum(III) atoms in different coordination states

Abstract Some Schiff’s base complexes of aluminum(III) of the type (CH3COCHCOCH3)2Al(µ-OPri)2AlLn(OPri)2-n [where LH=OHC(R)=CHC(R′)=NC6H5; R=R′=CH3,C6H5; R=CH3, R′=C6H5; LH=C6H4(OH)CH=NC6H5 and n=1 or 2] were prepared and characterized by various spectroscopic techniques. The molecular weight measurements indicated their binuclear nature. The 27Al nuclear magnetic resonance spectra of representative compounds [(CH3COCHCOCH3)2Al(µ-OPri)2Al{OC(C6H5)=CHC(C6H5)=NC6H5}(OPri)] [3] and [(CH3COCHCOCH3)2 Al(µ-OPri)2Al{OC(CH3)=CHC(CH3)=NC6H5}2] [6] suggest the presence of aluminum(III) atoms in different coordination states.

Dialkyl (Alkylene) Dithiophosphate Adducts of Anhydrous Stannous Chloride: Synthesis, Characterization, and Biological Activities

Abstract Dialkyl (alkylene) dithiophosphate adducts of stannous chloride were synthesized by the reaction of anhydrous tin(II) chloride (SnCl2) and dialkyl (alkylene) dithiophosphoric acid in a 1:1 molar ratio, under anhydrous reaction conditions, below 5 °C in a closed vessel. The newly synthesized adducts were characterized by physicochemical and spectroscopic techniques [FT-IR, NMR (1H, 31P, and 119Sn), and mass spectrometry]. Coordination modalities have indicated a donor–acceptor interaction between sulfur and tin(II) moieties, where tin(II) acts as a Lewis acid. The adducts were found to have significant antibacterial activity against Escherichia coli and Pseudomonas aeruginosa, and antifungal activity against Aspergillus niger and Candida albicans. Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT

Synthesis and characterization of a new class of single-phase AlVO4 precursors

Reactions of [Al(OPri)3] with [VO(OPri)3] in presence of halo-acetic acid, CX3COOH in anhydrous benzene yielded complexes of the type, [AlVO(OOCCX3)2(OPri)4], where X = F (1) or Cl (2). The compounds were characterised by elemental analyses, FT-IR and NMR (1H, 27Al & 51V) spectral studies. The desired single-phase aluminium vanadate, AlVO4, (a & b) have been obtained easily from the precursors, (1) and (2), respectively, by the sol-gel process. Formation of triclinic phase in both of the AlVO4 (a & b) samples was confirmed by powder XRD patterns. SEM image of (b) exhibits formation of nano-grains with agglomers like surface morphologies. Composition of AlVO4 sample (b) was investigated by EDX analysis, which shows presence of aluminium and vanadium in 1:1 atomic ratio. Absorption spectra of (a) and (b) samples indicate an energy band gap of 3.60 and 3.75 eV, respectively.