Pentadienyl anion C 5 H 7   charge = -1   Real ion. Gram formula weight (molecular mass) = 67.109 Pentadienyl anion is defined with respect to the entities below: The entities below are defined with respect to: Pentadienyl anion Pentadieny FMO (generic) pi-HOMO Lewis base (generic) Real complex ion (generic) chemical compound molecule metal molecular science reaction mechanism ionic material acid base geometry reactivity synthesis science knowledge chemistry Lewis