Synthesis of phosphonosulfonic acid building blocks as linkers for coordination polymers†
Ten aromatic building blocks (8–11, 23–28) containing phosphonic and sulfonic acid groups within one molecule were synthesized. Twofold nucleophilic substitution starting from 1,2,4,5-tetrakis(bromomethyl)benzene (1) followed by hydrolysis gave building blocks 8–11. To obtain building blocks 23–28, the respective bromobenzenesulfonic acids 13, 16, 18–20 and 22 had to be synthesized first. Palladium-catalysed cross coupling with triethylphosphite followed by hydrolysis gave the desired building blocks with phosphonic and sulfonic acid groups. Building block 9 was successfully used as a linker for the synthesis of a new La-based CP with the composition [La2(H2L)1.5(H2O)4].