Disclosed are methods of decreasing the concentration of a metal in a monomer composition including a bis(benzoyl)benzene, bis(benzoyl)benzene monomer compositions having a low total metal concentration, di-ketone polymers made from low metal bis(benzoyl)benzene monomers, and polymer compositions and shaped articles including the di-ketone polymers. It was surprisingly found that di-ketone polymers made by nucleophilic substitution of low metal bis(benzoyl)benzene monomers exhibit greater crystallinity, as compared with di-ketone polymers made with conventional monomers.