Synthesis and Structural Anisotropy of Single-Crystalline 2D AgEPh (E = S, Se, Te)

Silver phenylchalcogenides (AgEPh; E = S, Se, Te) are emerging two-dimensional (2D) semiconductors belonging to a broader class of hybrid organic–inorganic materials, known as metal organochalcogenolates (MOCs). However, it has been challenging to synthesize crystals of AgSPh and AgTePh that are sufficient for fundamental and applied research. Moreover, assignment of the crystal structure of AgSePh is debated (C2/c vs P21/c). Here, we report the growth of up to millimeter-sized single-crystalline 2D AgEPh (E = S, Se, or Te) having a macroscopic parallelogram shape. Transmission electron microscopy and electron diffraction studies reveal the relationship between their macroscopic morphology and microscopic crystal structure, which is essential for understanding in-plane anisotropic properties. We report three new crystal structures through single-crystal X-ray diffraction: 2D AgSPh in P21 and 2D AgTePh in P21/c, as well as 1D AgTeC6.27H5.62N0.09 (1D AgTePh + 0.089C3H7N) in P1̅. Significantly, our space group assignment of all three 2D AgEPh compounds in primitive lattices is different from that of the previously reported C-centered lattices. Using temperature-dependent powder X-ray diffraction and temperature-dependent absorption and photoluminescence spectroscopy of 2D AgEPh prepared by different synthetic methods, we reconcile discrepancies in their structural assignment, which is needed for the accurate theoretical prediction of electronic and vibrational properties.