Polymorphism and optical properties in [NH4][InSe2]

• Published in: Journal of solid state chemistry 2013-08, Vol.204, p.159-165
• Main Authors: Ewing, Sarah J., Woodward, David I., Powell, Anthony V., Vaqueiro, Paz
• Format: Article
• Language: English
• Subjects: AMMONIA; AQUEOUS SOLUTIONS; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Corners; Cross-disciplinary physics: materials science; rheology; Crystal structure; Crystalline state (including molecular motions in solids); Crystallization; Crystallographic aspects of phase transformations; pressure effects; CYCLOALKANES; Exact sciences and technology; Growth from solutions; HARMONIC GENERATION; INDIUM SELENIDES; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; LAYERS; Materials science; Methods of crystal growth; physics of crystal growth; OPTICAL PROPERTIES; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Physics; Polymorphism; Solvents; Solvothermal synthesis; SPACE GROUPS; Stoichiometry; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; SYNTHESIS; TETRAGONAL LATTICES
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2013.05.033

The solvothermal synthesis and characterization of two indium selenides with stoichiometry [NH4][InSe2] is described. Yellow [NH4][InSe2] (1), which exhibits a layered structure, was initially prepared in an aqueous solution of trans-1,4-diaminocyclohexane, and subsequently using a concentrated ammonia solution. A red polymorph of one-dimensional character, [NH4][InSe2] (2), was obtained using 3,5-dimethylpyridine as solvent. [NH4][InSe2] (1) crystallizes in the non-centrosymmetric space group Cc (a=11.5147(6), b=11.3242(6), c=15.9969(9)Å and β=100.354(3)°). The structural motif of the layers is the In4Se10 adamantane unit, composed of four corner-linked InSe4 tetrahedra. These units are linked by their corners, forming [InSe2]− layers which are stacked back to back along the c-direction, and interspaced by [NH4]+cations. The one-dimensional polymorph, (2), crystallizes in the tetragonal space group, I4/mcm (a=8.2519(16), c=6.9059 (14)Å). This structure contains infinite chains of edge-sharing InSe4 tetrahedra separated by [NH4]+ cations. Two polymorphic forms of [NH4][InSe2], which are yellow and red, have been prepared and their optical properties investigated. [Display omitted] •Two new indium selenides prepared by a solvothermal method.•Depending on synthesis conditions, two polymorphic forms of [NH4][InSe2] prepared.•Layered polymorph contains In4Se10 adamantane clusters, linked by their corners.•One-dimensional polymorph contains [InSe2]− chains of edge-sharing tetrahedra.•Non-centrosymmetric layered polymorph shows a second harmonic generation response.