cyclopentadienone noun1 •Am unsaturated alicyclic ketone derived from cyclopentadiene; any derivative of this compoundAldrichimica Acta Volume 30 No 4 (pdf) from Sigma-Aldrich The availability of diazaphencyclone (DAPC) has allowed the cyclopentadienone methodology to be used for attaching the 1,10-phenanthroline ligand onto molracs. formscyclopentadienones