Spectroscopic approach in characterization of chromium(III), manganese(II), iron(III) and copper(II) complexes with a nitrogen donor tetradentate, 14-membered azamacrocyclic ligand

The complexes of Cr(III), Mn(II), Fe(III) and Cu(II) were synthesized with the macrocyclic ligand i.e. 2,3,9,10-tetraketo-1,4,8,11-tetraazacyclotetradecane. The ligand was prepared by the [2 + 2] condensation reaction of diethyloxalate and 1,3-diamino propane. These complexes were found to have the general composition M(L)X3 and M'(L)X2 [where M = Mn(II) and Cu(II), M' = Cr(III) and Fe(III), L = ligand (N4) and X = Cl-, NO3-, 1/2SO4(2-) and [CH3COO-]. The ligand and its transition metal complexes were characterized by the elemental analyses, molar conductance, magnetic susceptibility, mass, IR, electronic, and EPR spectral studies. On the basis of IR, electronic and EPR spectral studies an octahedral geometry has been assigned for Cr(III), Mn(II) and Fe(III) and a tetragonal geometry for Cu(II) complexes.     

Use of diphenylamine reagent for high-performance thin-layer chromatographic detection of organochloro insecticide endosulfan in biological samples

JPC – Journal of Planar Chromatography – Modern TLC -     

Elusive Zintl Ions [μ‐HSi4]3− and [Si5]2− in Liquid Ammonia: Protonation States,Sites, and Bonding Situation Evaluated by NMR and Theory

The existence of [μ‐HSi₄]^3? in liquid ammonia solutions is confirmed by ¹H and ²⁹Si NMR experiments. Both NMR and quantum chemical calculations reveal that the H atom bridges two Si atoms of the [Si₄]^4? cluster, contrary to the expectation that it is located at one vertex Si of the tetrahedron. The calculations also indicate that in the formation of [μ‐HSi₄]^3?, protonation is driven by a high charge density and an increase of electron delocalization compared to [Si₄]^4?. Additionally, [Si₅]^2? was detected for the first time and characterized by NMR. Calculations show that it is resistant to protonation, owing to a strong charge delocalization, which is significantly reduced upon protonation. Thus, our methods reveal three silicides in liquid ammonia: unprotonated [Si₅]^2?, terminally protonated [HSi₉]^3?, and bridge‐protonated [μ‐HSi₄]^3?. The protonation trend can be roughly predicted by the difference in charge delocalization between the parent compound and the product, which can be finely tuned by the presence of counter ions in solution.