New sarcosine–metal halide complexes related to 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.