ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Effect of the partial substitution of sulfur by selenium on the atomic arrangement in sulfate- and selenate-based compounds

Ines Kadri, Marwa Abid Derbel, Houcine Naïli, Thierry Roisnel, and Walid Rekik

Laboratoire Physico-Chimie de l’Etat Solide, Faculté des Sciences de Sfax, Université de Sfax, Sfax, Tunisia

E-mail: walidrekik@lycos.com

Abstract: Two new co-based hybrid materials, (C₄H₁₂N₂)[Co(H₂O)₆](S_0.689Se_0.311O₄)₂ (1) and (C₄H₁₂N₂)[Co(H₂O)₆](S_0.80Se_0.20O₄)₂ (2), have been synthesized by slow evaporation method at room temperature and crystallographically characterized. They crystallizes isotypically in the monoclinic system, space group C2/c, with the following unit-cell parameters: a = 14.2559(19), b = 9.5066(13), c = 13.6759(19) Å, β = 114.930(4)°, V = 1680.7(4) ų, and Z = 4 for (1) and a = 14.2235(19), b = 9.4901(14), c = 13.666(2) Å, β = 114.863(4)°, V = 1673.7(4) ų, and Z = 4 for (2). Their crystal structure consist of metallic cations octahedrally coordinated by six water molecules [Co(H₂O)₆]²⁺, piperazinediium cations (C₄H₁₂N₂)²⁺, and sulfate/selenate anions (S_xSe_1-xO₄)²⁻ linked together via two types of hydrogen bonds, Ow–H···O and N–H···O. The IR spectroscopic study confirms not only the substitution of the sulfur by the selenium but also the piperazine protonation. Through this work, it is demonstrated that the substitution of sulfur by selenium atom can lead to strong modification in the space group and atomic arrangement. Indeed the mixed selenate/sulfate compounds adopt a crystal structure different from those of the pure sulfate or selenate phases. The thermogravimetric measurement indicates that the dehydration occurs in two steps by the departure of six water molecules giving rise to an anhydrous phase. The final product of the decomposition is cobalt oxide, CoO, in both cases.

Keywords: Partial substitution; Supramolecular; Thermal decomposition; IR spectroscopy

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-017-0199-3

Chemical Papers 71 (11) 2063–2073 (2017)