Ab initio study on the photoisomers of a nitro-substituted spiropyran

Structural and spectroscopic properties of the photoisomers of a nitro-subs tituted spiropyran have been investigated by performing ab initio molecular orbital (MO) calculations both in vacuo and in hexafluoro-2-propanol solut ion. Full geometry optimisation of the closed form and of the transoid conf ormations of the open form has been carried out. Dipole moments of both pho toisomers have been determined, the ratio of which agrees with recent exper imental results. Net atomic charges have also been determined according to three different approaches. (C) 2000 Elsevier Science B.V. All rights reser ved.