[(C2H5)3NH]2Cu2(C2O4)3: a three-dimensional metal-oxalato framework showing structurally related dielectric and magnetic transitions at around 165 K.

An achiral (10,3) net three-dimensional metal-oxalato framework [Cu(2)(C(2)O(4))(3)(2-)](n) was formed by cation-templating. At around 165 K, the disorder-order transition of cation (C(2)H(5))(3)NH(+) hosted in the channel resulted in dielectric transition, and the antiferromagnetic interactions between the Jahn-Teller distorted Cu(ii) through the oxalato-bridge below 165 K was enhanced.