New sarcosine-metal halide complexes related to the ferroelectric TSCC

Abstract

There are relatively few sarcosine metal halide complexes. Of these, tris sarcosine calcium chloride (TSCC) ((C3NO2H7)3CaCl2) stands out as an unusual example of a molecular ferroelectric. Here we report the syntheses of eight new related sarcosine-metal halide complexes by slow evaporation. The newly reported materials can be categorised into four different structure types, viz. 3:1 complexes such as (C3NO2H7)3CaBr2, hydrated 3:1 complexes such as (C3NO2H7)3MnI2.2H2O, hydrated 2:1 complexes such as (C3NO2H7)2MgCl2.2H2O, and a 4:1 complex (C3NO2H7)4CaI2.2H2O. The crystal structures of all examples have been determined at multiple temperatures but no evidence is found for any structural transitions to polar phases, either by single crystal X-ray diffraction or by differential scanning calorimetry. The specific compositional reasons behind the apparently unique ferroelectric behaviour of TSCC therefore remain to be ascertained.