An organic/inorganic hybrid system, (benzo[1,2-d:4,5-d ' ]bis[1,3,2]dithiazole (=BBDTA)).FeCl 4 .CH 3 COCH 3 , is shown to exhibit a drastic change in magnetism after evaporation of the volatile crystal solvent, acetone. The solvated material, with a crystal structure consisting of ladder-like BBDTA and a honeycomb network of Fe(III)Cl 4 , exhibits antiferromagnetic ordering at 6.3 K. Magnetic measurements and Mossbauer spectra suggest that the desolvated material includes a ferrimagnetic phase with T N =44.0K.