An efficient method for the synthesis of copillar[5]arenes was developed with FeCl(3) as catalyst and different 1,4-dialkoxybenzenes and paraformaldehyde as reactants (yields: 50-85%). The host-guest property of (co)pillar[5]arenes and terminal dibromoalkanes was investigated by (1)H NMR measurements and an X-ray study. The complexation behavior of the copillar[5]arenes can be tuned by changing the substituents on the host. A complete complexation selectivity was found between pillar[5]- and pillar[6]arenes, which is an interesting aspect for sensor techniques.