Crystal-to-crystal interconversion of open and closed dicopper(ii) paddle wheels in a heterotrimetallic coordination polymer.

Treatment of [Au2Pd(dppm)(d-pen)2] ([1]) with Cu(NO3)2 gave a 1D (AuI2PdIICuII2)n coordination polymer, [Cu2(1)2(H2O)4](NO3)4 ([2](NO3)4), which was reversibly converted to its dehydrated species, [Cu2(1)2(H2O)2](NO3)4 ([3](NO3)4), with retention of crystallinity. The magnetic feature of [2](NO3)4 differs dramatically from that of [3](NO3)4, showing an unusual loop in the course of the magnetic susceptibility measurements due to the reversible opening and closing motions of dicopper(ii) paddle wheels in the solid state.