Deuteration-Enhanced Negative Thermal Expansion and Negative Area Compressibility in a Three-Dimensional Hydrogen Bonded Network

High Resolution Image Download MS PowerPoint Slide Negative area compressibility (NAC) and negative thermal expansion (NTE) are material behaviors raising high hope for applications such as ultrasensitive manometry and thermometry. However, the group of NAC materials is primarily limited to two-dimensional (2D) coordination compounds whose layered structure is prone to bidirectional compression when pressurized. Here, we report an alternative strategy that does not employ the formation of metal–organic systems but takes advantage of the pliability of hydrogen-bonded networks for searching materials with very rare NLC and NAC behaviors. Indeed, a strong NAC property, coupled with large NTE, has been identified for the hydrogen-bonded hydrochloride salt of L-arginine homologue ( S )-2-amino-3-guanidinopropanoic acid monochloride – (HAmGP)Cl and its deuterated analogue – (DAmGP)Cl. While both structures feature isostructural phase transition at ca. 0.88 GPa, it is discovered that the replacement of protium with deuterium significantly boosts NAC magnitudes: phase II of (DAmGP)Cl features over two-fold higher negative area compressibility coefficient than that of the nondeuterated analogue (β 2,3 = −17.6(27) TPa –1 for (DAmGP)Cl vs −7.9(38) TPa –1 for HAmGP)Cl. Remarkably, the obtained value is the second largest area compressibility coefficient known for any material. What is more, deuteration enhances also the NTE property (α 2 = −23.4(22) vs −16.1(31) MK –1 for (DAmGP)Cl and (HAmGP)Cl, respectively) of the investigated supramolecular network. Our research opens new paths to the preparation of organic hydrogen-bonded materials with unique mechanical responsiveness to temperature and pressure stimuli.