Pyridine and Pyrimidine Functionalized Benzene Sulfonic and Disulfonic Acids as New Linker Compounds for Coordination Polymers

Sulfonic acids serve as interesting, yet not intensively studied alternatives to carboxylic acids as linker units in coordination polymers. In this study, we present the synthesis of hybrid sulfonic acids with pyridine and pyrimidine units as additional nitrogen donor moieties. Four biaryl compounds consisting of a 4-mono- or 3,5-disulfophenyl ring and a 4-pyridyl or 5-pyrimidyl residue were prepared by Suzuki coupling reaction. In these cases, tert-butylthio groups were utilized as precursor functions for the sulfonic acid residues. The tert-butyl residues were cleaved with BBr3, the intermediate thiols trapped with acetyl chloride and then oxidized with H2O2. Furthermore, two pyrimidine derivatives with 5-ethynyl linkers and 4-mono- and 3,5-disulfophenyl moieties were prepared by Sonogashira coupling. In these cases, the sulfonic acids were applied as neopentyl esters. Finally, the neopentyl groups were simply cleaved by thermolysis.