Synthesis and complexation properties of two new curcuminoid molecules bearing a diphenylmethane linkage

Abstract Bis-curcuminoids 3 and 4 , bearing a diphenylmethane bridge for both compounds and a crown ether chain adapted to complex Li + for compound 4 , were synthesized and characterized by mass and NMR spectroscopies. By their preorganized geometry, they represent a new class of curcuminoids able to complex transition metal cations. Their absorption spectra in DMF by comparison with those of curcumin 1 and dimethylcurcumin 2 have shown that the phenolate forms in the two halves are in interaction in compound 3 and are independent in compound 4 . Complexation studies have revealed a poor selectivity of curcuminoids for transition metals. Nevertheless complexation of Cu (II), studied by UV–visible absorption spectroscopy, has shown subtle differences between curcumin 1 and bis-curcuminoid 3 . These observations were supported by quantum mechanic calculations to establish the most probable structures of non- and complexed compounds.