Synthesis and Structural Anisotropy of Single-Crystalline\n2D AgEPh (E = S, Se, Te)

Silver\nphenylchalcogenides (AgEPh; E = S, Se, Te) are emerging\ntwo-dimensional (2D) semiconductors belonging to a broader class of\nhybrid organic–inorganic materials, known as metal organochalcogenolates\n(MOCs). However, it has been challenging to synthesize crystals of\nAgSPh and AgTePh that are sufficient for fundamental and applied research.\nMoreover, assignment of the crystal structure of AgSePh is debated\n(<i>C</i>2/<i>c</i> vs <i>P</i>2<sub>1</sub>/<i>c</i>). Here, we report the growth of up to\nmillimeter-sized single-crystalline 2D AgEPh (E = S, Se, or Te) having\na macroscopic parallelogram shape. Transmission electron microscopy\nand electron diffraction studies reveal the relationship between their\nmacroscopic morphology and microscopic crystal structure, which is\nessential for understanding in-plane anisotropic properties. We report\nthree new crystal structures through single-crystal X-ray diffraction:\n2D AgSPh in P2<sub>1</sub> and 2D AgTePh in <i>P</i>2<sub>1</sub>/<i>c</i>, as well as 1D AgTeC<sub>6.27</sub>H<sub>5.62</sub>N<sub>0.09</sub> (1D AgTePh + 0.089C<sub>3</sub>H<sub>7</sub>N) in P1̅. Significantly, our space group assignment of all\nthree 2D AgEPh compounds in primitive lattices is different from that\nof the previously reported C-centered lattices. Using temperature-dependent\npowder X-ray diffraction and temperature-dependent absorption and\nphotoluminescence spectroscopy of 2D AgEPh prepared by different synthetic\nmethods, we reconcile discrepancies in their structural assignment,\nwhich is needed for the accurate theoretical prediction of electronic\nand vibrational properties.