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

Negative area compressibility (NAC) and negative thermalexpansion(NTE) are material behaviors raising high hope for applications suchas ultrasensitive manometry and thermometry. However, the group ofNAC materials is primarily limited to two-dimensional (2D) coordinationcompounds whose layered structure is prone to bidirectional compressionwhen pressurized. Here, we report an alternative strategy that doesnot employ the formation of metal-organic systems but takesadvantage of the pliability of hydrogen-bonded networks for searchingmaterials with very rare NLC and NAC behaviors. Indeed, a strong NACproperty, coupled with large NTE, has been identified for the hydrogen-bondedhydrochloride salt of L-arginine homologue (S)-2-amino-3-guanidinopropanoicacid monochloride - (HAmGP)Cl and its deuterated analogue -(DAmGP)Cl. While both structures feature isostructural phase transitionat ca. 0.88 GPa, it is discovered that the replacement of protiumwith deuterium significantly boosts NAC magnitudes: phase II of (DAmGP)Clfeatures over two-fold higher negative area compressibility coefficientthan that of the nondeuterated analogue (& beta;(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 largestarea compressibility coefficient known for any material. What is more,deuteration enhances also the NTE property (& alpha;(2) =-23.4(22) vs -16.1(31) MK-1 for (DAmGP)Cland (HAmGP)Cl, respectively) of the investigated supramolecular network.Our research opens new paths to the preparation of organic hydrogen-bondedmaterials with unique mechanical responsiveness to temperature andpressure stimuli.