Isomerism in double-pillared-layer coordination polymers – structures and photoreactivity

The existence of isomerism in coordination polymeric structures offers opportunities to understand structure–function relationships. Herein the serendipitous isolation is reported of two isomeric double-pillared-layer coordination polymeric structures arising from two different types of carboxyl­ate bonding of benzene-1,4-di­carboxyl­ate ligands to zinc(II), which constitutes a new type of structural isomerism. The different bonding modes not only alter the shape and size of the pores, but also the nature of interpenetration and photoreactivity. Although two trans,cis,trans-bpeb ligands with conjugated olefin bonds are aligned in close proximity in both of the structures, one isomer undergoes a double [2 + 2] cyclo­addition reaction and the second isomer only offers an incomplete single cyclo­addition product. This work demonstrates how small changes in the structural connectivity can have an impact on the overall structural, physical and chemical properties of such materials.