Ca(SCN)₂ and Ca(SCN)₂ · 2 H₂O: Crystal Structure, Thermal Behavior and Vibrational Spectroscopy

Abstract

The dehydration of Ca(SCN)2∙4H2O yields single crystals of Ca(SCN)2 ∙ 2 H2O as well as of Ca(SCN)2. Ca(SCN)2 ∙ 2 H2O crystallizes with a hitherto unknown structure (orthorhombic, Pnma, Z = 4, a = 1280.1(2), b = 790.3(1), c = 726.9(1) pm, Rall = 0.0430). The Ca2+ ions are surrounded by four SCN− ions and four water molecules. The polyhedra are connected to chains along [010] via common oxygen atoms. The SCN− ions connect these chains to a three-dimensional network so that each thiocyanate group is linked to two Ca2+ ions. Hydrogen bonding with sulfur atoms as acceptors is observed. The crystal structure of Ca(SCN)2 (monoclinic, C2/c, Z = 4, a = 961.7(2), b = 642.4(2), c = 787.2(2) pm, Rall = 0.0673) consists of alternating layers of Ca2+ and SCN− ions. The cations are surrounded by four sulfur and four nitrogen atoms in form of a square antiprism. According to 3∞[Ca(SCN)8/4] each SCN− ion connects four Ca2+ ions with each other. Thermal investigations show a phase transition of Ca(SCN)2 ∙ 4 H2O followed by dehydration to Ca(SCN)2 which finally decomposes yielding CaS. IR and Raman measurements have been performed and the resulting frequencies assigned and discussed.

Photoluminescence of Ba(SCN)2:Eu2+

“…The ligands are identical in both cases but the degree of covalency is lower for the thiocyanates compared to these of nitrides and sulfides. This forced us to synthesise the respective alkaline earth and europium compounds M(SCN) 2 (M = Ca, Sr, Ba, Eu) and determine the crystal structures [3,4]. Fortunately, all compounds except of Ca(SCN) 2 can be prepared as single phase samples.…”

Synthesis and luminescence properties of novel NaSCN: xCe3+ phosphor

“…In 2004 Michel Fleck [9] reported more than 80 inorganic thiocyanate hosts. Eu 2+ luminescence in some of these hosts such as strontium thiocyanate (Sr (SCN) 2 ) [10], barium thiocyanate (Ba (SCN) 2 ) [11] and in Ca (SCN) 2 • 2H 2 O [12] was reported by C. Wickleder et al The green-emitting CsSCN: Eu 2+ phosphor was reported by Bertha Abdu Danja et al [13]. But there are no studies on Ce 3+ luminescence in these hosts.…”

Photoluminescent properties of Eu3+‐Eu2+ activated MAl2SixO2x + 4 (M = Mg, Ca, Sr, Ba) phosphors prepared in air

“…But the 5d orbitals of Eu 2+ are exposed to crystal field, which are easily influenced by the host lattice. The strong interactions with the lattice lead to the splitting of 4f5d, and make excitation bands range from 250 to 420 nm, which means that Eu 2+ ‐doped phosphors can excellently match the emission wavelength of near‐ultraviolet light‐emitting diode (LED) chips. In addition, Eu 2+ has been demonstrated to be an efficient sensitizer for many activators through energy transfer .…”