Ester deprotection (Step C) The 2,6,-dicarboethoxy-3,7-diheptadecylthieno[3,2-b]thieno[2′,3′:4,5]thieno[2,3-d]thiophene (5.00 g, 7.39 mmol) product of Example 6, was dissolved in tetrahydrofuran (THF) (280 mL) then methanol (40 mL) was added. Lithium hydroxide (707 mg, 29.5 mmol) was dissolved in water (7 mL) and added to the stirred methanol and THF solution. A condenser was fitted and the reaction mixture was heated in an oil bath at 90° C. for 16 hr. The THF and methanol were removed under reduced pressure. 60 mL of methanol and 10 mL of conc. hydrochloric acid were added then stirred for 4 h. Next 50 mL of water was added and the solid was filtered off. The product was dried under vacuum to give the 3,7-didecanyl thieno[3,2-b]thieno[2′,3′:4,5]thieno[2,3-d]thiophene-2,6-dicarboxylic acid (4.50 g, 98% yield). 1H NMR (D8-THF)(of the di-lithium salt) δ 0.88 (6H, t, J=6.9 Hz), 1.20-1.47 (28H, m), 1.70-1.86 (4H, m), and 3.24 (4H, t, J=7.5 Hz).
