Synthesis and crystal structure of Fe[(Te1.5Se0.5)O5]Cl, the first iron compound with selenate(IV) and tellurate(IV) groups

During the search for selenium analogues of FeTe2O5Cl, the new iron (III) tellurate(IV) selenate(IV) chloride with the composition Fe[(Te1.5Se0.5)O-5]Cl was synthesized by chemical vapor transport (CVT) reaction and characterized by TGA-, EDX-, SCXRD-analysis, as well as IR and Raman spectroscopy. It was found that Fe[(Te1.5Se0.5) O5] Cl crystallizes in the monoclinic space group P2(1)/c with unitcell parameters a = 5.183(3) angstrom, b = 15.521(9) angstrom, c = 7.128(5) angstrom and b = 107.16(1)degrees. The crystal structure of Fe[(Te1.5Se0.5)O-5]Cl represents a new structure type and contains electroneutral heteropolyhedral layers formed by dimers of the [FeO5Cl](8-) octahedra, linked via common O-O edges, and mixed [Te3SeO10](4-) tetramers. Adjacent layers are stacked along the b axis and linked by weak residual bonds. The new compound is stable up to 420 degrees C. DFT calculations predict Fe[(Te1.5Se0.5)O-5] Cl to be a wide-gap semiconductor with the band gap of ca. 2.7 eV. (C) 2017 Elsevier Masson SAS. All rights reserved.