Solvatochromic correlations and ground- and excited-state dipole moments of curcuminoid dyes

Abstract Experimental dipole moments of curcumin ( 1 ) and of its parent compound dicinnamoylmethane ( 2 ) were determined in dioxane and benzene, respectively. Theoretical dipole moments were calculated using a combination of the PPP method (π-moment) and a vector sum of the σ-bond moments (σ-moment) as well as by the ZINDO/1 method. Solvatochromic correlations were used to obtain the experimental first excited singlet-state dipole moments. The experimental electronic absorption spectra were compared with the calculated transitions.