Browsing by Author "Ma, Liulei (TTU)"
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Item Colossal Anisotropic Thermal Expansion in a Diazo-Functionalized Compound with Switchable Solid-State Behavior(2023) Ding, Xiaodan (TTU); Unruh, Daniel K. (TTU); Ma, Liulei (TTU); van Aalst, Evan J. (TTU); Reinheimer, Eric W.; Wylie, Benjamin J. (TTU); Hutchins, Kristin M. (TTU)Achieving substantial anisotropic thermal expansion (TE) in solid-state materials is challenging as most materials undergo volumetric expansion upon heating. Here, we describe colossal, anisotropic TE in crystals of an organic compound functionalized with two azo groups. Interestingly, the material exhibits distinct and switchable TE behaviors within different temperature regions. At high temperature, two-dimensional, area zero TE and colossal, positive linear TE (α=211 MK−1) are attained due to dynamic motion, while at low temperature, moderate positive TE occurs in all directions. Investigation of the solid-state motion showed the change in enthalpy and entropy are quite different in the two temperature regions and solid-state NMR experiments support motion in the solid. Cycling experiments demonstrate that the solid-state motions and TE behaviors are completely reversible. These results reveal strategies for designing significant anisotropic and switchable behaviors in solid-state materials.Item Enantioselective assembly of multi-layer 3D chirality(2020) Wu, Guanzhao (TTU); Liu, Yangxue (TTU); Yang, Zhen; Jiang, Tao; Katakam, Nandakumar (TTU); Rouh, Hossein (TTU); Ma, Liulei (TTU); Tang, Yao (TTU); Ahmed, Sultan (TTU); Rahman, Anis U.; Huang, Hongen; Unruh, Daniel (TTU); Li, Guigen (TTU)The first enantioselective assembly of sandwich-shaped organo molecules has been achieved by conducting dual asymmetric Suzuki-Miyaura couplings and nine other reactions. This work also presents the first fully C-C anchored multi-layer 3D chirality with optically pure enantiomers. As confirmed by X-ray diffraction analysis that this chiral framework is featured by a unique C2-symmetry in which a nearly parallel fashion consisting of three layers: top, middle and bottom aromatic rings. Unlike the documented planar or axial chirality, the present chirality shows its top and bottom layers restrict each other from free rotation, i.e., this multi-layer 3D chirality would not exist if either top or bottom layer is removed. Nearly all multi-layered compounds showed strong luminescence of different colors under UV irradiation, and several randomly selected samples displayed aggregation-induced emission (AIE) properties. This work is believed to have broad impacts on chemical, medicinal and material sciences including optoelectronic materials in future.Item Reversible interconversion of pharmaceutical salt polymorphs facilitated by mechanical methods(2023) Ma, Liulei (TTU); Zheng, Qixuan (TTU); Unruh, Daniel K. (TTU); Hutchins, Kristin M. (TTU)Salification of the drug trimethoprim with enantiopure D- or L-lactic acid afforded salts with up to five times improved solubility. Both salts are polymorphic and we demonstrate fully reversible interconversion (cycling) between the drug polymorphs using mechanochemistry and slurry methods. We show drug polymorph interconversion requires both solvent contact and mechanical force, revealing strategies for cycling between solid material forms.