Abstract
Abstract 2-hydroxy-1,4-naphthoquinone; Lawsone ( Lw ) is a natural compound found in henna leaves. The reaction of lawsone with ‘Na’ metal ( Lw - 1 ), CH 3 COONa ( Lw - 2 ), NaOH ( Lw - 3 ), KOH ( Lw - 4 ), K 2 CO 3 ( Lw - 5 ) and Tris(hydroxymethyl)aminomethane ( Lw - 6 ) were studied. Red orange solids obtained for Lw - 1 to Lw - 6 are characterized by Elemental Analysis, FTIR, 1 HNMR and EPR studies. The results reveal the coordination of alkali metals ‘Na’ and ‘K’ to lawsone anion. The single crystal X-ray structure of Lw - 6 was solved and it crystallizes in triclinic space group P-1 with extensive hydrogen bonding network of C H⋯O, N H⋯O and O H⋯O between cations and anions. Polycrystalline powder X-band EPR spectra of Lw - 1 to Lw - 5 shows signals ∼2.004 at 133 K, while Lw - 6 is EPR silent. The naphthosemiquinone ( NSQ − ) radical formed in Lw - 2 to Lw - 5 , is due to disproportion reaction of catechol and naphthoquinone.
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