Crystal structures, syntheses, and spectroscopic and electrochemical measurements of two push–pull chromophores: 2-[4-(dimethylamino)benzylidene]-1<i>H</i>-indene-1,3(2<i>H</i>)-dione and (<i>E</i>)-2-{3-[4-(dimethylamino)phenyl]allylidene}-1<i>H</i>-indene-1,3(2<i>H</i>)-dione
Acta crystallographica. Section E, Crystallographic communications