title: Ab initio and semiempirical study of structure and electronic spectra of hydroxy substituted naphthoquinones.
abstract: The geometries of hydroxy derivatives of 1,4-naphthoquinone (NQ), viz., 2-hydroxy-1,4-naphthoquinone (2HNQ), 5-hydroxy-1,4-naphthoquinone (5HNQ), and 5,8-dihydroxy-1,4-naphthoquinone (DHNQ), have been optimized using the semiempirical and ab initio theoretical methods. Semiempirical methods used for the optimization are Austin Model 1 (AM1) and Zerner's Intermediate Neglect of Differential Overlap/1(ZINDO/1). For ab initio calculations the 6-31G* basis set is used. The electronic spectra of 1,4-naphthoquinone and its hydroxy derivatives are calculated using the semiempirical Zerner's Intermediate Neglect of Differential Overlap/Spectroscopy (ZINDO/S) method employing the geometries optimized at AM1, ZINDO/1 and ab initio levels and compared with their electronic absorption spectra measured by us. For hydroxy substituted systems, such calculations for spectral assignments are made for the first time. It is found that though the predictions of the three theoretical methods for the geometries are similar, the predictions of the ZINDO/S method using the ZINDO/1 optimized geometries, are better for the transition wavelengths in the visible region of the hydroxy substituted naphthoquinones, especially for 5HNQ and DHNQ.
authors.affiliation: Laser Spectroscopy Laboratory, Department of Physics, Jamia Millia Islamia (Central University), Jamia Nagar, New Delhi 110025, India. shahidkhan_m@yahoo.com
authors.forename: Mohd Shahid
authors.initials: MS
authors.lastname: Khan
authors.forename: Zahid H
authors.initials: ZH
authors.lastname: Khan
mesh_terms: D003510:Cyclohexanes / Q000737:chemistry; D004583:Electrons; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008962:Models, Theoretical; D008968:Molecular Conformation; D015394:Molecular Structure; D009285:Naphthoquinones / Q000737:chemistry*; D012984:Software; D013053:Spectrophotometry / Q000379:methods*; D014466:Ultraviolet Rays; D014961:X-Ray Diffraction
chemical_list: D003510:Cyclohexanes; D009285:Naphthoquinones; C035342:1,4-naphthoquinone