Highly Selective On-Surface Reactions of Aryl Propiolic Acids via Decarboxylative Coupling.

Aryl propiolic acids are introduced as a new class of monomers in the field of on-surface chemistry to build up poly(arylenebutadiynylenes) through decarboxylative Glaser coupling. As compared to arylalkynes that are routinely used in the on-surface Glaser coupling, it was found that the decarboxylative coupling occurs at slightly lower temperature and with excellent selectivity. Activation occurs through decarboxylation for the propiolic acids whereas the classical Glaser coupling is achieved through alkyne C-H activation and this process shows poor selectivity. The efficiency of the decarboxylative coupling was documented by successful polymerization of bis(alkynylpropiolic acids) as monomers. It was also found that the new activation mode is compatible with aryl bromide functionalities which allows the formation of unsymmetric metal-organic polymers on surface by chemoselective sequential reactions. All transformations were analyzed by a scanning tunneling microscope (STM) and were further studied by density functional theory (DFT) calculations. This article is protected by copyright. All rights reserved.