• Prasanta Kumar Santra

      Articles written in Journal of Chemical Sciences

    • Studies on the chemistry of copper(I) with arylazoimidazoles

      Tarun Kumar Misra Prasanta Kumar Santra Chittaranjan Sinha

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      N(1)-alkyl-2-(arylazo)imidazoles (RC6H4N=NC3H2N N(1)X; X=Me (a), Et (b); R=7-Me(L1), 7-OMe(L2), 7-Cl(L3), 7-NO2(L4) and 8-Me(L5)) yield perchlorate salts ofbis-chelated complexes with copper(I). The complexes are 1:1 electrolyte and the composition in supported by Jobs method of continuous variation. The N=N stretching is red shifted by 60–70 cm−1 compared to free ligand values suggesting efficient charge delocalization from Cu(I) to ligand centre. This is supported by high intense MLCT transitions in the visible region. The complexes show highly resolved symmetrical1H NMR spectra exhibiting C2-symmetry at least in the NMR time scale. In MeOH the complexes exhibit quasi-reversible CuL22+/CuL2+ couple at 0.4–0.5 Vvs SCE at 298 K. The high positive potential may be due to the distortion in the geometry of CuL2+.

    • Chemistry of azopyrimidines. Part IV. Aromatic hydroxylation in palladium(II)-arylazopyrimidines

      Prasanta Kumar Santra Ramkrishna Roy Chittaranjan Sinha

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      2-(Arylazo)pyrimidines (aapm) are N,N′-chelating ligands and synthesise orange-red complexes of composition [Pd(aapm)Cl2],1, with Pd(MeCN)2Cl2 in MeCN. The complex hascis-PdCl2 configuration [v(Pd-Cl): 340, 360 cm−1]. The treatment of Tollen’s reagent (‘AgOH’) leads to chelatative hydroxylation in the pendant aryl ring, affording a green phenolato complex, Pd(aapmO)Cl,5 (aapmO is deprotonated 2-((8-hydroxo)arylazo)pyrimidine). The reaction is also carried out by controlled addition of dilute sodium hydroxide in air or by the addition of PhIO/m-chloroperbenzoic acid to a MeCN suspension of the complex. A single Pd-Cl stretch at 360 cm−1 supports the composition of phenolato complex. Unlike Pd(aapm)Cl2 the hydroxylated product, Pd(aapmO)Cl, has a structured intense absorption in the visible region near 670 nm. The Pd-Cl bond in Pd(aapmO)Cl is highly sensitive to nucleophilic substitution and slowly hydrolyses in aqueous medium.

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