Fig. 2: Mechanism studies.
From: Low-cost synthesis of small molecule acceptors makes polymer solar cells commercially viable
a The reaction subsequently shows starting materials (ITIC-CHO, IC), the diacetate intermediate and pre-product, as well as the ITIC product. b In situ 1H NMR (600 MHz) experiments in toluene-d8 with an expanded view in the fields of 9.5-7.8 ppm. During the experiment, a mixture of ITIC-CHO (5.0 mg) and IC (1.8 mg) in a molar ratio of 1: 2 in toluene-d8 (1 ml) was added into the NMR tube along with GaCl3 (about 1 mg) and acetic anhydride (0.02 ml). c Plausible reaction pathways for the Lewis acid-catalyzed Knoevenagel condensation. d Computed free-energy profiles for comparison of the Lewis acid-catalyzed pathway and the traditional pathway. The calculation was conducted with B3LYP-6-31G (d, p). Relative Gibbs free energies of the reaction system at 298 K are given in kcal/mol, whereas the energy of the starting material is arbitrarily set to zero. In the molecules, the bule color represents D unit and the red color represents the A unit.
