Molecular structures of 2-hydroxy-1,4-naphthoqinone derivatives and their zinc(II) complexes: Combining experiment and density functional theory

• Molecular structures of lawsone and its halogen derivatives are derived.
• ZnLw complex trans–trans conformer was found to be 8 kJ mol−1 lower in energy than the cis, cis conformer.
• Three molecules of BrLw in asymmetric unit cell differing H-bonding interactions.
• Polymeric chains of ZnBrLw complex were mediated via water molecules.
• Molecular association of ligand in solution, revealed by electrochemical studies.

Molecular structures of 2-hydroxy-1,4-naphthoquinone (Lw), its chloro (ClLw; 2-chloro-3-hydroxy-1,4-naphthoquinone) and bromo (BrLw; 2-bromo-3-hydroxy-1,4-naphthoquinone) derivatives and their Zn(II) complexes are derived from the wB97x based density functional theory. The calculations predicted that the trans, trans conformer of the Zn(II) complex of 2-hydroxy-1,4-naphthoquinone (ZnLw) turns out to be of the lowest energy. A comparison of C(2) substituted chloro and bromo derivatives has been presented. Single X-ray crystal structure revealed that the BrLw belongs to monoclinic Cc space group with three independent molecules in its asymmetric unit cell with the crystal network extending through π–π stacking whilst the ZnBrLw complex possesses monoclinic P21/n space group and facilitate hydrogen bonding interactions. Electrochemical characterization describing the redox behavior of BrLw and Zn(II) complex in DMSO has been carried out through cyclic voltammetry experiments.

2-Bromo-3-hydroxy-1,4-naphthoquinone (BrLw) and its Zn(II) complex: synthesis characterization, DFT and electrochemical studies.Figure optionsDownload as PowerPoint slide