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Updated: Jun 12, 2025

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The GaCl3-Catalyzed Knoevenagel Condensation To Achieve Acceptor-Donor-Acceptor Small-Molecule Acceptors: A DFT
Xiaofan Shi1, Yaqi Zhao1,2, Ying Zhou1,3
1State Key Laboratory of Chemical Resource Engineering, Institute of Computational Chemistry, College of Chemistry, Beijing University of Chemical Technology, Beijing 100029, China.
Abstract:
Herein, the reaction mechanism for the GaCl3-catalyzed Knoevenagel condensation of 2-formylindacenodithieno[3,2-b]thiophene (ITIC-CHO) and active methylene compound 1,1-dicyanomethylene-3-indanone (IC) to synthesize ITIC in the presence of acetic anhydride was investigated using the density functional theory (DFT) method. The calculated results indicate that this reaction follows a bimolecular GaCl3 catalytic mechanism. The free energy span for the monomolecular GaCl3 catalytic mechanism is the highest (31.8 kcal/mol), followed by the trimolecular GaCl3 catalytic mechanism (26.4 kcal/mol) and the bimolecular GaCl3 catalytic mechanism (26.3 kcal/mol). The trimolecular GaCl3 path and bimolecular GaCl3 path are competitive, but the former path is limited by the concentration of GaCl3. The inclusion of GaCl3 could stabilize the transition states of C-H activation. Compared to the GaCl3-catalyzed Knoevenagel condensation, that catalyzed by pyridine is not advantageous, owning a high energy span of 31.7 kcal/mol. These agree well with experimental results. This work could provide a novel theoretical understanding of the Knoevenagel condensation, which could inspire the development of a synthesis strategy for electron acceptor materials.
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