Complex thermal expansion properties in a molecular honeycomb lattice

摘要

[FeL_3][BF_4]_2·xH_2O (L = 3-(pyrazinyl)-1H-pyrazole) shows negative thermal expansion between 150-240 K but positive thermal expansion at 240-300 K, linked to rearrangement of anions and water molecules within pores in the lattice. Eleven years ago, we reported that [FeL_3][BF_4]2·xH_2O (1; L = 3-(pyrazinyl)-1H-pyrazole) contains C_3-symmetric fac-[FeL_3](2+) centres, associated into a chiral 3D honeycomb array through intermolecular N-H…N hydrogen bonding (Fig. 1 and 2).