Search Results (2)

This paper reports for the first time on the new laminar quaternary orthorhombic heterometallic quaternary tellurides SrLnCuTe₃, the fabrication of which has been a challenge until this work. Data on the crystal structure of tellurides complete the series of quaternary strontium chalcogenides SrLnCuCh₃ (Ch = S, Se, Te). Single crystals of the compounds were synthesized from the elements by the halogenide-flux method at 1070 K. The compounds are crystallizing in two space groups Pnma (Ln = Sm, Gd and Tb) and Cmcm (Ln = Dy–Tm and Lu). For SrSmCuTe₃ (a = 11.4592(7), b = 4.3706(3), c = 14.4425(9) Å, space group: Pnma) with the largest lanthanoid cation, Sr²⁺ shows C.N. = 7, whereas Sm³⁺ reveals a diminished coordination number C.N. = 6. For SrLuCuTe₃ (a = 4.3064(3), b = 14.3879(9), c = 11.1408(7) Å, space group: Cmcm) with the smallest lanthanoid cation, coordination numbers of six are realized for both high-charged cations (Sr²⁺ and Lu³⁺: C.N. = 6). The cations Sr²⁺, Ln³⁺, Cu⁺ each take independent positions. The structures are built by distorted [CuTe₄]^7– tetrahedra, forming the infinite chains $\{_{\infty }^1{[\mathrm{Cu}{\left(\mathrm{Te}1\right)}_{1/1}^{\mathrm{t}}{\left(\mathrm{Te}2\right)}_{1/1}^{\mathrm{t}}{\left(\mathrm{Te}3\right)}_{2/2}^{\mathrm{e}}]}^{5-}\}$ along [010] in SrLnCuTe₃ (Ln = Sm, Gd and Tb) and [100] in SrLnCuTe₃ (Ln = Dy–Tm and Lu). The distortion of the polyhedra [CuTe₄]^7– was compared for the whole series SrLnCuTe₃ by means of τ₄-descriptor for the four coordinating Te^2– anions, which revealed a decrease in the degree of distortion with a decreasing radius at Ln³⁺. The distorted octahedra [LnTe₆]^9– form layers $\{_{\infty }^2{[Ln{\left(\mathrm{Te}1\right)}_{2/2}{\left(\mathrm{Te}2\right)}_{2/2}{\left(\mathrm{Te}3\right)}_{2/2}]}^{3-}\}$. The distorted octahedra and tetrahedra fuse to form parallel layers $\{_{\infty }^2{[\mathrm{Cu}Ln{\mathrm{Te}}_3]}^{2-}\}$ and between them, the Sr²⁺ cations providing three-dimensionality of the structure are located. In the SrLnCuTe₃ (Ln = Sm, Gd and Tb) structures, the Sr²⁺ cations center capped the trigonal prisms [SrTe₆₊₁]¹²⁻, united in infinite chains $\{_{\infty }^1{[\mathrm{Sr}{\left(\mathrm{Te}1\right)}_{2/2}{\left(\mathrm{Te}2\right)}_{3/3}{\left(\mathrm{Te}3\right)}_{2/2}]}^{4-}\}$ along the [100] direction. The domains of existence of the Ba₂MnS₃, BaLaCuS₃, Eu₂CuS₃ and KZrCuS₃ structure types are defined in the series of orthorhombic chalcogenides SrLnCuCh₃ (Ch = S, Se and Te). The tellurides SrLnCuTe₃ (Ln = Tb–Er) of both structure types in the temperature range from 2 up to 300 K are paramagnetic, without showing clear signs of a magnetic phase transition. Full article

We performed a structural study of N-alkylated halogenopyridinium cations to examine whether choice of the N-substituent has any considerable effect on the halogen bonding capability of the cations. For that purpose, we prepared a series of N-ethyl-3-halopyridinium iodides and compared them with their N-methyl-3-halopyridinium analogues. Structural analysis revealed that N-ethylated halogenopyridinium cations form slightly shorter C−X⋯I⁻ halogen bonds with iodide anion. We have also attempted synthesis of ditopic symmetric bis-(3-iodopyridinium) dications. Although successful in only one case, the syntheses have afforded two novel ditopic asymmetric monocations with an iodine atom bonded to the pyridine ring and another on the aliphatic N-substituent. Here, the C−I⋯I⁻ halogen bond lengths involving pyridine iodine atom were notably shorter than those involving an aliphatic iodine atom as a halogen bond donor. This trend in halogen bond lengths is in line with the charge distribution on the Hirshfeld surfaces of the cations—the positive charge is predominantly located in the pyridine ring making the pyridine iodine atom σ-hole more positive than the one on the alkyl chan. Full article