CS2PDSE8 - A UNIQUE OPEN FRAMEWORK STRUCTURE WITH DOUBLE-HELICAL ASSEMBLIES OF [PD(SE-4)(2)](2-)

Cs2PdSe8(1), a novel palladium polyselenide with a three-dimensional o pen framework structure, has been synthesized via a solvothermal react ion using ethylenediamine as solvent. Its crystal structure has been d etermined by single crystal X-ray diffraction. The structure belongs t o the tetragonal space group I4(1)/acd (No. 142), a=14.935(2), c=12.90 7(3) Angstrom, V=2897.0(8) Angstrom(3), Z=8, R-1=0.044, and wR(2)=0.06 3, for 640 unique reflections. The unique three-dimensional network is composed of two (3)(infinity)[Pd(Se-4)(2)](2-) frameworks that are to pologically identical and mutually insertional. Each framework is buil t upon by connecting the neighboring square-planar [Pd(Se-4)(2)](2-) u nits to generate an infinite assembly resembling alternating right- an d left-handed helices running along the c-axis. Thermal analysis (TGA) showed that compound 1 is stable up to 320 degrees C. Optical studies performed on the powder sample of 1 suggested that the compound is a semiconductor and a band gap of 1.5 eV was estimated from the diffuse reflectance data. (C) 1998 Academic Press.