Ground- and Excited-state Dipole Moments of Magnesium Phthalocyanine from Solvatochromic Shifts and Solvent Polarity Functions

Abstract

The ground- (ï­g)  and excited-state (ï­e) dipole moments of magnesium phthalocyanine (MgPc) were determined via a semi-empirical approach involving the solvatochromic shift method, which is derived from the Onsager’s reaction field theory. The ( ô€€€) ratio has been determined by combining the Bakshiev and the Kawski-Chamma-Viallet’s equations; whereas the dipole moment difference (ï­ï„) between the ground state and the excited state was estimated by means of the molecular-microscopic solvent polarity parameters (ô€€‚ô€€ƒô€€), together with ï„á¿¡, the Stokes’ shifts in the respective solvents. MgPc’s dipole moment is appreciably higher in the excited singlet state than in the ground state. The values are 3.57 and 2.58 in the excited and ground state respectively. These results suggest a sizeable rearrangement of Ï€-electron densit;ies and higher charge separation in the excited-state. Keywords: Dipole moment; Ground state; Excited state; Zinc phthalocyanine; Solvatochromism.