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

A 3Dcoordination 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.