Host-guest interaction in a thiourea-dimethyl oxalate (2/1) complex at 300 and 100 K

The title complex, 2CH4N2S.C4H6O4, is a host-guest system. The asymmetric unit consists of one complete thiourea molecule and one-half of a dimethyl oxalate molecule lying on an inversion centre. The host thiourea molecules are connected to form zigzag chains by N-H...S hydrogen bonds. The guest dimethyl oxalate molecules provide O-atom acceptors for N-H...O hydrogen bonds, thus interconnecting the chains of thiourea molecules to form completely connected sheets. The reduction in temperature from 300 to 100 K leaves the structure unchanged and still isostructural with that previously determined for the analogous thiourea-diethyl oxalate (2/1) complex. It does, however, induce closer packing of the molecules, general shrinkage of the unit cell and shortening of the hydrogen bonds, these last two to the extent of 1-2%.