Abstract:
Molecular structures and their molecular association of 2-(n-alkylamino)-1,4-naphthoquinone, viz., LH3; propyl, LH-4; butyl and LH-8; octyl derivatives were studied by single crystal X-ray diffraction studies.
Synthesis and characterization of 2-octylamino-1,4-naphthoquinone; LH-8 was discussed. The molecule
of LH-3 crystallizes in orthorhombic space group P21/c, while the LH-4 and LH-8 molecule crystallizes in
triclinic space group P-1. LH-3, LH-4 and LH-8 showed intermolecular N-H/O and C-H/O interactions,
LH-3 showed unique C(3)-H(3)/O(1) interaction. Interchain p-p stacking, slipped p-p stacking and
C/O close contacts was respectively observed in LH-3, LH-4 and LH-8. Electrochemical studies were
performed on first eight members of homologous series of 2-(n-alkylamino)-1,4-naphthoquinone (LH-1
to LH-8) by cyclic voltammetry. Naphthoquinone to naphthosemiquinone reversible redox couple was
observed in all compounds ~ E1/2 ¼ 0.657 ± 0.05 V. HOMO-LUMO band gap was determined for the
neutral form as well as the monoanionic radical form viz. naphthosemiquinone form of selected derivatives by DFT studies. It has been observed that the electron density is delocalized in the naphthoquinone ring in both neutral as well as one electron reduced form of compounds. Antiproliferative
activity of LH-1 to LH-8 was evaluated against two cancer cell lines, THP1(acute monocytic leukemia) and
K562(human immortalized myelogenous leukemia cell line) cells. It was observed that, in THP1 cells,
compounds LH-2 and LH-3 are very active while LH-1, LH-4 and LH-6 were moderately active and LH-5,
LH-7 and LH-8 were totally inactive. Contrastingly, in K562 cells all of the compounds were moderately
active.
