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  • Author or Editor: Neeraj Sharma x
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Abstract

The thermal decomposition behaviours of oxovanadium(IV)hydroxamate complexes of composition [VO(Q)2−n(HL1,2)n]: [VO(C9H6ON)(C6H4(OH)(CO)NHO)] (I), [VO(C6H4(OH)(CO)NHO)2] (II), [VO(C9H6ON)(C6H4(OH)(5-Cl)(CO)NHO)] (III), and [VO(C6H4(OH)(5-Cl)(CO)NHO)2] (IV) (where Q = C9H6NO 8-hydroxyquinolinate ion; HL1 = [C6H4(OH)CONHO] salicylhydroxamate ion; HL2 = [C6H3(OH)(5-Cl)CONHO] 5-chlorosalicylhydroxamate ion; n = 1 and 2), which are synthesised by the reactions of [VO(Q)2] with predetermined molar ratios of potassium salicylhydroxamate and potassium 5-chlorosalicylhydroxamate in THF + MeOH solvent medium, have been studied by TG and DTA techniques. Thermograms indicate that complexes (I) and (III) undergo single-step decomposition, while complexes (II) and (IV) decompose in two steps to yield VO(HL1,2) as the likely intermediate and VO2 as the ultimate product of decomposition. The formation of VO2 has been authenticated by IR and XRD studies. From the initial decomposition temperatures, the order of thermal stabilities for the complexes has been inferred as III > I > II > IV.

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Abstract

Thermal behaviour of newly synthesized niobium(V) aryloxides of composition [NbCl5−n (OC6H4CH(CH3)2-4) n ] (where n = 1 → 5) synthesized by the reactions of niobium pentachloride with 4-isopropylphenol in predetermined molar ratios in carbon tetrachloride has been studied by thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The results showed that thermal decomposition of complex of composition [NbCl4(OC6H4CH(CH3)2-4)] resulted in the formation of NbOCl3 as the ultimate decompositional product while all other complexes yielded Nb2O5 as the final product of thermal decomposition. From the mathematical analysis of TG data, the kinetic and thermodynamic parameters viz. energy of activation, frequency factor, entropy of activation, etc. have been evaluated using Coats–Redfern equation.

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Abstract

The thermal decomposition behavior of oxovanadium(IV)hydroxamate complexes of composition [VO(acac)(C6H5C(O)NHO)] (I), [VO(C6H5C(O)NHO)2] (II), [VO(acac)(4-ClC6H4C(O)NHO)] (III), [VO(4-ClC6H4C(O)NHO)2] (IV) (where acac = (CH3COCHCOCH3 ) synthesized from the reactions of VO(acac)2 with equi- and bimolar amounts of potassium benzohydroxamate and potassium 4-chlorobenzohydroxamate in THF + MeOH solvent medium has been studied by TG and DTA techniques. TG curves indicated that complexes I, II, and IV undergo decomposition in single step to yield VO2 as the final residue, while complex III decomposes in two steps to yield VO(acac) as the likely intermediate and VO2 as the ultimate product of decomposition. The formation of VO2 has been authenticated by IR and XRD studies. From the initial decomposition temperatures, the order of thermal stability for the complexes has been inferred as IV > I > III > II.

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