Controlled formation of chiral networks and their reversible chiroptical switching behaviour by UV/microwave irradiation

A 3D coordination polymer {[Cd(L(1))(L(2))]2}n (1) spontaneously resolves into enantiomorphic crystals of 1P and 1M without any chiral source. Bulk quantities of 1P and 1M can be predictably and reliably obtained by using chiral cyclohexane-1,2-diamine. 1 can be transformed into {[Cd(L(1))(L(3))0.5]2}n (2) by highly selective [2+2] photodimerization of L(2) ligands. The reverse process can be achieved by microwave irradiation. The cycloreversion/cycloaddition cycles result in chiroptical switching behavior.