Balram P. Baranwal

Substitution reactions of thorium(IV) acetate to synthesize nano-sized carboxylate complexes

Some mixed-ligand thorium(IV) complexes with the general formula [Th(OOCCH(3))(4-n)L(n)] (L=anions of myristic, palmitic or stearic acid and n=1-4) have been synthesized by the stepwise substitution of acetate ions of thorium(IV) acetate with straight chain carboxylic acids in toluene under reflux. The complexes were characterized by elemental analyses, spectral (electronic, infrared, NMR and powder XRD) studies, electrical conductance and magnetic susceptibility measurements. Doubly and triply bridged coordination modes of the ligands were established by their infrared spectra and nano-size of the complexes by powder XRD. Room temperature magnetic susceptibility measurements revealed diamagnetic nature of the complexes. Electronic absorption spectra of the complexes showed pi-->pi*, n-->pi* and charge transfer transitions. Molar conductance values indicated the complex to be non-electrolytes. These are a new type of mixed-ligand thorium(IV) complexes for which a nano-sized, oxygen bridged polymeric structure has been established on the basis of physico-chemical studies.

Synthesis and Physico‐Chemical Studies on Iron(II,III,III) and Cobalt(II) Thiocarboxylates

Abstract A series of iron(II,III,III) and cobalt(II) complexes of thiocarboxylic acids of the general formulas [FeIIFe2 IIIO(SOCR)6(L)3] and [Co(SOCR)2(L)2] (R = C2H5 or C(CH3)3 and L = EtOH or py) have been synthesized and characterized by elemental and thermogravimetric analyses, spectral (infrared, electronic, and Mössbauer) studies, molar conductance, magnetic susceptibility, and molecular weight determinations. The electronic spectral data suggested an octahedral environment around the metal ion in both the iron as well as the cobalt complexes. A band around 13,800 cm−1 in the electronic spectra of the iron complexes indicated intervalence‐transfer between Fe(II) and Fe(III) moieties. A bridging mode of coordination could be assigned for the thiocarboxylate anions in the iron complexes and a chelating mode of coordination for the cobalt complexes have been suggested by infrared spectral data along with a new band at 540 cm−1, which may be ascribed owing to νasy(Fe3O) vibrations. Mössbauer studies revealed two resolved quadrupole doublets at 120–315 K confirming the presence of Fe(II) and Fe(III) moities in the iron complexes. Thermoanalytical data indicated the iron complexes were thermally stable up to 135 °C, whereas the cobalt complexes were stable up to 160 °C, above which temperature decomposition started and continued to ∼400 °C at which temperature the formation of metal sulfide and/or oxide was noticed. An attempt has been made to establish the structures based on these studies.

Synthesis and spectral characterization of ternary mixed-vanadyl β-diketonate complexes with Schiff bases.

A new method to synthesize some mononuclear ternary oxovanadium(IV) complexes of the general formula [VO(β-dike)(SB)] (where Hβ-dike=acetylacetone; benzoylacetone or dibenzoylmethane, HSB=Schiff bases) has been explored by stepwise substitutions of acetylacetonate ion of VO(acac)(2) with Schiff bases. The substituted acetylacetone could be fractionated out with p-xylene as an azeotrope. The complexes were characterized by elemental analyses, molecular weight determinations, spectral (electronic, infrared, (1)H NMR, EPR and powder XRD) studies, magnetic susceptibility measurements and cyclic voltammetry. Molar conductance measurements indicated the complexes to be non-electrolytes in nitrobenzene. Bidentate chelating nature of β-diketones and Schiff base anions in the complexes was established by infrared and NMR spectra. Molecular weight determinations confirmed mononuclear nature of the complexes. The EPR spectra illustrated coupling of the unpaired electron with (51)V nucleus (I=7/2). Cyclic voltammograms of all the complexes displayed two-step oxidation processes. The oxidation peak potential corresponded to the quasireversible one-electron oxidation process of the metal center, yielding V(V) species. Transmission electron microscopy (TEM) indicated spherical particles of ∼200 nm diameter. The synthesized complexes are mixed-ligand complexes showing a considerable hydrolytic stability in which vanadium is having coordination number 5. A square pyramidal geometry around vanadium has been assigned in all the complexes.

Hydroxycarboxylato Complexes of Copper(II): Synthesis and Characterization

Abstract Substitution reactions of anhydrous copper(II) acetate with some higher carboxylic acids and hydroxycarboxylic acids were carried out in toluene under reflux. The isolated products; Cu(OOCR)(OOCR′), Cu(OOCR)(OOCR″) and Cu(OOCR)(OOCR″′) [where R = C13H27, C17H35 or C21H43 and R′ = C6H4OH, R″ = C6H5CH(OH) and R″′ = (C6H5)2C(OH)] were characterized by elemental analyses, spectral (infrared and electronic) analyses and conductivity measurements. IR spectra suggest the presence of bidentate-bridging coordination of carboxylate anions in the complexes. Magnetic moment measurement and electron spin resonance spectral data suggest antiferromagnetic coupling between two copper atoms. The dinuclear nature of the complexes was confirmed by molecular weight determinations.

Nano-sized, quaternary titanium(IV) metal-organic frameworks with multidentate ligands

Some mononuclear nano-sized, quaternary titanium(IV) complexes having the general formula [Ti(acac)(OOCR)2(SB)] (where Hacac=acetylacetone, R=C15H31 or C17H35, HSB=Schiff bases) have been synthesized using different multidentate ligands. These were characterized by elemental analyses, molecular weight determinations and spectral (FTIR, 1H NMR and powder XRD) studies. Conductance measurement indicated their non-conducting nature which may behave like insulators. Structural parameters like the values of limiting indices h, k, l, cell constants a, b, c, angles α, β, γ and particle size are calculated from powder XRD data for complex 1 which indicated nano-sized triclinic system in them. Bidentate chelating nature of acetylacetone, carboxylate and Schiff base anions in the complexes was established by their infrared spectra. Molecular weight determinations confirmed mononuclear nature of the complexes. On the basis of physico-chemical studies, coordination number 8 was assigned for titanium(IV) in the complexes. Transmission electron microscopy (TEM) and the selected area electron diffraction (SAED) studies indicated spherical particles with poor crystallinity.

SYNTHESIS AND CHARACTERIZATION OF SOME TRINUCLEAR COBALT(II) THIOCARBO XYLATES

ABSTRACT Some cobalt(II) complexes of thiocarboxylic acids with the general composition Co(SOCR′)2 and Co(SOCR′)(OOCR) [where R= C13 H27, C15H31 or C17H35 and R′=CH3 or C6H5] have been synthesized by substitution reactions and characterized by elemental analyses, spectral studies and magnetic moment measurements. The electrical conductance data indicate that (Co(SOCCH3)2 is a 1:2 electrolyte while the other complexes are non-electrolytes. IR spectra show the presence of bidentate and bridging modes of coordination for carboxylate and thiocarboxylate anions, respectively. Electronic spectral data and magnetic moment values indicate an octahedral environment around cobalt(II). The plausible structure for the trimeric species has been proposed on the basis of the physico-chemical studies. Thermoanalytical data indicate the complexes are stable upto 175 °C, above which decomposition starts.

Shape Controlled Synthesis of Nano-Sized Titanium(IV) Metal-Organic Frameworks

A convenient method to synthesize shape controlled nano-sized metal-organic frameworks (MOFs) has been explored to prepare some novel mixed–ligand complexes of titanium(IV) with the general formula [Ti(acac)Cl2−n(OOCC15H31)(SB)n] (where Hacac = acetylacetone, HSB = Schiff bases and n = 1 or 2). They have been synthesized by stepwise substitutions of chloride ions from titanium(IV) chloride. The complexes were characterized by elemental analyses, molecular weight determinations, spectral, and TEM studies. Coordination number 7 and 8 was assigned for titanium(IV) in the complexes. The powder XRD, TEM, and SAED studies indicates that these complexes are nano-sized having poor crystalline nature.

Spectroscopic studies on some fluorescent mixed-ligand titanium(IV) complexes.

A novel route to synthesize some titanium(IV) complexes containing acetylacetone, straight chain carboxylic acid and hydroxycarboxylic acid ligands has been investigated. Complexes with the general formula [Ti(acac)Cl(2-n)(OOCR*)(n)(OOCC(15)H(31))] (where Hacac=acetylacetone, R*COOH=hydroxycarboxylic acids and n=1 or 2) have been isolated and characterized. Molecular weight determinations indicated mononuclear nature of the complexes. LMCT bands were observed in the electronic spectra. Infrared spectra suggested bidentate nature of the ligands. Fluorescent behaviour of the complexes was noticed on the basis of fluorescence spectra. Powder XRD indicated them to be semi-crystalline having the crystallite size in 136-185 nm range. Transmission electron microscopy (TEM) indicated spherical particles of ~ 200 nm diameter. On the basis of physico-chemical studies, it is suggested that titanium is having coordination number 7 or 8 in these complexes.

Substitutions of copper(II) carboxylates with Schiff bases

Substitutions of anhydrous copper(II) acetate with higher carboxylic acids in an equimolar ratio in refluxing toluene yield monosubstituted soluble derivatives, which undergo substitutions with Schiff bases (derived from salicylaldehyde and aniline or p-chloroaniline) to give mixed complexes of the general formula [Cu(OOCR)- (SB)] (HSB = Schiff base and R = C13H27, C15H31, C17H35 and C21H43). The products have been characterized by elemental analyses, electrical conductance, magnetic moment and spectral (i.r. and electronic) data. Cryoscopic molecular weight determinations indicate that the derivatives are dimers. The complexes are e.p.r. silent.

Spectroscopic investigations of nano-sized titanium(IV) complexes containing electron-rich oxygen-based ligands

A convenient method has been explored to synthesize some nano-sized, mixed-ligand complexes of titanium(IV) with the general formula [Ti(acac)Cl(2-n)(L)(n)(OOCC(15)H(31))] (where Hacac=acetylacetone, HL=dibenzoylmethane or benzoylacetone and n=1 or 2). They have been synthesized by stepwise substitutions of chloride ions from titanium(IV) chloride with straight chain carboxylic acid and β-diketones. These were characterized by elemental analyses, molecular weight determinations, spectral (electronic, FTIR, (1)H NMR and powder XRD) and TEM studies. Conductance measurements indicated their non-conducting nature which may behave like insulators. Bidentate chelating nature of carboxylate and β-diketones anions in the complexes was established by their infrared spectra. LMCT bands were observed in the electronic spectra. Molecular weight determinations indicated mononuclear nature of the complexes. Powder XRD and transmission electron microscopy (TEM) studies indicated the particles of these were lying in the nano-size range. The complexes exhibited high resistance to hydrolysis. On the basis of these studies, coordination number 7 or 8 is assigned for titanium in the synthesized complexes.