Metal complexes of hydroxynaphthoquinones: Lawsone, bis-lawsone, lapachol, plumbagin and juglone

Coordination chemistry of hydroxynaphthoquinones viz. lawsone (2-hydroxy-1,4-napthoquinone; Lw) derivatives, bis-lawsone (2,2´-bi(3-hydroxy-1,4-naphthoquinone; H2bhnq), lapachol (2-hydroxy-3-(3-methylbut-2-enyl)naphthalene-1,4-dione; Lap), plumbagin (5-hydroxy-2-methyl-naphthlene-1,4-dione; PLN) and juglone (5-hydroxy-1,4-naphthalenedione) have been reviewed in brief with respect to structural and spectroscopic properties. We aimed to gather most of the potential information of the known metal complexes of hydroxynapthoquinone derivatives obtained by various chemical and physical methods which are reported till date. A brief description of the synthetic and structural studies of hydroxynaphthoquinone ligands and their metal complexes are presented. The majority of the complexes are mononuclear with distorted octahedral geometry, however dimers, trimers, tetramers and polymers also have been reported. In most of the cases various ancillary ligands are present due to solvent or counterion binding, depending on the synthetic procedures. Several “cis, cis” and “trans, trans” isomeric structures were also reported. The review is a complete information guide for hydroxynapthoquinone and its derivative metal complexes.