Sensing of Lead Ions by a Carboxylate-Substituted PPE: Multivalency Effects Ik-Bum Kim, Anna Dunkhorst, James Gilbert, and Uwe H. F. Bunz* School of Chemistry and Biochemistry, Georgia Institute of Technology, 770 State St., Atlanta, GA 30332, USA. Fax: 01(404)385-1795; Tel: 01(404)385-1795; E-mail: uwe.bunz@chemistry.gatech.edu Electronic Supplementary Information (ESI) Synthesis of Polymer 4 and Model Compound 5 O O I I O O O O O O O O O O + O O O O O O n (Ph 3 P) 2 PdCl 2 / CuI TEA / CH 2 Cl 2 O O + Na - O O O - Na + O n NaOH CH 3 OH 1 2 3 4 Synthesis of 1: 1,4-Diiodo-2,5-dihydroquinone (3.62 g, 10.0 mmol), 1 2-butanone (50 mL), potassium carbonate (13.8 g, 100 mmol), and ethyl bromoacetate (6.68 g, 40.0 mmol, commercially available, Aldrich) were placed in a 250 mL round bottom flask and heated to reflux for 24 h. The mixture was allowed to cool to room temperature and the solvent was removed. The crude solid was crystallized from a mixture of ethyl acetate and hexane to yield pure 1 as a colorless solid (3.61 g, 68%). 1 H NMR (CDCl 3 ): δ 7.12 (s, 2H), 4.58 (s, 4H), 4.24 (q, 1