The solid-state structures of a series of seven substituted 3-methylidene-1H-indol-2 (3H)- one derivatives have been determined by single-crystal X-ray diffraction and are compared in detail. Six of the structures {(3Z)-3-(1H-pyrrol-2-ylmethylidene)-1H-indol-2 (3H)-one, C13H10N2O,(2a);(3Z)-3-(2-thienylmethylidene)-1H-indol-2 (3H)-one, C13H9NOS,(2b);(3E)- 3-(2-furylmethylidene)-1H-indol-2 (3H)-one monohydrate, C13H9NO2· H2O,(3a); 3-(1- ...