Drei Alkalimetall-Erbium-Thiophosphate: Von der Schichtstruktur bei KEr[P2S7] zur dreidimensionalen Vernetzung in NaEr[P2S6] und Cs3Er5[PS4]6

Li9Yb2[PS4]5 and Li6Yb3[PS4]5: two lithium-containing ytterbium(III) thiophosphates(V) revisited

The lithium ytterbium ortho-thiophosphates Li9Yb2[PS4]5 and Li6Yb3[PS4]5 were prepared through the reaction of stoichiometric amounts of ytterbium metal, elemental sulfur, red phosphorus and lithium hemisulfide at elevated temperatures in sealed silica tubes. The compounds occur as dark red single crystals which crystallize monoclinically in space group C2/c with the lattice parameters a = 1487.98(9), b = 978.63(6), c = 2046.75(12) pm and β = 96.142(3)° for Li9Yb2[PS4]5 (Z = 4) and a = 2814.83(16), b = 997.34(6), c = 3338.52(19) pm and β = 113.685(3)° for Li6Yb3[PS4]5 (Z = 12). Li9Yb2[PS4]5 can be assigned to the structure type of Li9Nd2[PS4]5, whereas the structure of Li6Yb3[PS4]5 the structure is similar to that of the prototypic Li6Gd3[PS4]5. Both structures feature discrete [PS4]3– tetrahedra (d(P–S) = 202–207 pm) and strands of [YbS8]13− polyhedra (d(Yb–S) = 271–319 pm) propagating along [010]. When attributed to the general formula (Li3[PS4]) x (Yb[PS4]) y , ideas of the dimensionality of both structures can be derived. Whilst the lithium-richer Li9Yb2[PS4]5 (x/y = 1.5) develops planes with the composition   ∞ 2 { [ Y b [ P S 4 ] 3 ] 6 − } ${}_{\infty }^{2}\left\{{\left[\mathrm{Y}\mathrm{b}{\left[\mathrm{P}{\mathrm{S}}_{4}\right]}_{3}\right]}^{6-}\right\}$ , Li6Yb3[PS4]5 (x/y = 0.667) exhibits a rather complex three-dimensional network of ytterbium-centered polyhedra connected via [PS4]3– tetrahedra with lithium cations in the framework structure   ∞ 3 { [ Y b 3 [ P S 4 ] 5 ] 6 − } ${}_{\infty }^{3}\left\{{\left[\mathrm{Y}{\mathrm{b}}_{\mathrm{3}}{\left[\mathrm{P}{\mathrm{S}}_{4}\right]}_{5}\right]}^{6-}\right\}$ . These Li+ cations are hard to locate in both compounds, but reside in four- to sixfold sulfur coordination (d(Li–S) = 235–304 pm). Some Li+ positions are underoccupied and some Li+ cations share sites with Yb3+ cations in Li6Yb3[PS4]5, and even in Li9Yb2[PS4]5 their high displacement values suggest Li+ cation mobility. According to the empirical formulae, three Li+ cations have to be replaced with one Yb3+ cation to reach the lithium-poorer compound and structure (Li6Yb3[PS4]5) starting from the lithium-richer one (Li9Yb2[PS4]5).

A series of Rb4Ln2(P2S6)(PS4)2 (Ln = La, Ce, Pr, Nd, Sm, Gd) rare earth thiophosphates with two distinct thiophosphate units [PVS4]3- and [PIV2S6]4

A series of rubidium rare earth thiophosphates with the formula Rb4Ln2(P2S6)(PS4)2 (Ln = La, Ce, Pr, Nd, Sm, and Gd) were synthesized using the high temperature molten flux crystal growth method utilizing a RbBr flux. Single crystals of all title compounds, as well as phase pure powders of the La-, Ce-, and Sm-containing compositions, were obtained. Single crystals of the title compounds were characterized by single crystal and powder X-ray diffraction for structure and phase identification. Rb4Ln2(P2S6)(PS4)2 crystallizes in the monoclinic crystal system adopting the P21/n space group for the large rare earths (Ln = La, Ce, Pr) and the C2/c space group for the smaller rare earths (Ln = Nd, Sm, Gd). This Rb4Ln2(P2S6)(PS4)2 series is a rare example of thiophosphates containing both tetrahedral [PVS4]3- and dimeric [PIV2S6]4- thiophosphate units that, in this structural family, link corrugated rare earth sulfide chains into sheets. The band gaps of the materials were determined from UV-Vis data and the fluorescence spectrum of Rb4Ce2(P2S6)(PS4)2 was collected. Optical band gaps were estimated to be 2.9 and 2.4 for the Nd and Sm analogues, respectively.

Trends in rare earth thiophosphate syntheses: Rb3Ln(PS4)2 (Ln = La, Ce, Pr), Rb3−xNaxLn(PS4)2 (Ln = Ce, Pr; x = 0.50, 0.55), and RbEuPS4 obtained by molten flux crystal growth

Crystal structures of new rubidium rare earth thiophosphates with the formulas Rb₃Ln(PS₄)₂ (Ln = La, Ce, Pr), Rb_3−xNa_xLn(PS₄)₂ (Ln = Ce, Pr; x = 0.50, 0.55), and RbEuPS₄ crystallized out of a molten RbCl flux.

Three of a kind? The non-isotypic triple CsCe[P2Se6], CsSm[P2Se6] and CsEr[P2Se6]

Three new compounds of the CsLn[P2Se6] family with Ln = Ce, Sm and Er have been prepared and structurally characterized. Plate-shaped, amber-colored single crystals of these cesium lanthanoid(III) hexaselenodiphosphates(IV) were obtained by heating stoichiometric amounts of Ln, P and Se with CsCl as a reactive flux in fused silica ampoules at 800 °C for four days. CsCe[P2Se6] crystallizes monoclinically in space group P21/c with a = 1297.86(9), b = 776.24(5), c = 1198.43(8) pm, β = 106.589(3)° and Z = 4. The structure is isotypic with that of KLa[P2Se6], the Cs+ cations being ten-fold coordinated by selenium atoms to form double layers of condensed [CsSe10]19− polyhedra. Ce3+ resides in a nine-fold coordination and the [CeSe9]15− polyhedra also form double layers parallel to (100). CsSm[P2Se6] crystallizes in the orthorhombic space group P212121 with a = 688.67(5), b = 754.48(5), c = 2215.21(15) pm and Z = 4. Its structure is isotypic with that of KY[P2Se6] and the Cs+ cations reside in an eleven-fold coordination of selenium atoms constituting monolayers of condensed [CsSe11]21− polyhedra within the (001) plane. Sm3+ exhibits an eight-fold coordination sphere of selenium atoms and the [SmSe8]13− polyhedra are also linked to build up parallel monolayers. CsEr[P2Se6] crystallizes in the monoclinic space group P21/c again, but forms its own structure type with the lattice parameters a = 753.81(5), b = 1281.92(9), c = 1276.47(9) pm and β = 106.898(3)° and Z = 4. The Cs+ cations are twelve-fold coordinated by selenium atoms and erects a three-dimensional framework of condensed [CsSe12]23− polyhedra. The Er3+ cations show seven selenium atoms as neighbors and the [ErSe7]11− polyhedra are edge-connected to form discrete dimers [Er2Se12]18−. All three structures have similar ethane-like [P2Se6]4– anions in staggered conformation with bond lengths of 219–226 pm for d(P1–P2) and 213–222 pm for d(P–Se), which connect the Cs+ and Ln 3+ coordination polyhedra into three-dimensional crystal structures.

Nearly Identical but Not Isotypic: Influence of Lanthanide Contraction on Cs2NaLn(PS4)2 (Ln = La-Nd, Sm, and Gd-Ho)

The effect of lanthanide contraction often results in topological and symmetry changes in compounds with the same compositions as a function of lanthanide cation size. Here we report on the first example of a lanthanide thiophosphate exhibiting a change in the lanthanide cation environment without any topological or symmetry change. A series of new lanthanide thiophosphates with mixed alkali cations were obtained via a flux crystal growth technique using a CsI flux. The obtained compounds Cs₂NaLn(PS₄)₂ (Ln = La-Nd, Sm, and Gd-Ho) were grown as large single crystals (∼0.1-1 mm³) and characterized using single-crystal X-ray diffraction and magnetic susceptibility measurements. As we moved across the series, the structural studies revealed a change in the lanthanide coordination environment depending on the identity of the lanthanide. Although all compounds in the Cs₂NaLn(PS₄)₂ series crystallize in the same space group and have the same Wyckoff atom positions, a slight change in size between Sm³⁺ and Gd³⁺ causes a subtle change in coordination number from 9 (for Ln = La-Sm) to 8 (for Ln = Gd-Ho), resulting in two distinct but virtually identical structure types. Ab initio calculations were performed, and the observed experimental trend was corroborated computationally. Magnetic measurements performed on the Cs₂NaLn(PS₄)₂ (Ln = Ce, Pr, Nd, Gd, and Tb) compounds revealed paramagnetic behavior.

Size-Driven Stability of Lanthanide Thiophosphates Grown from an Iodide Flux

To determine the influence of the lanthanide size on the structures and properties of thiophosphates, a thiophosphate series containing different lanthanides was synthesized via high temperature flux crystal growth and their structures and physical properties analyzed and compared. Layered thiohypophosphates NaLnP₂S₆ (Ln = La, Ce, Pr) and thiopyrophosphates CsLnP₂S₇ (Ln = Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Yb, Y) were grown out of an iodide flux using consistent reaction conditions across both series. Under the mildly reducing iodide flux reaction conditions, a rather rare example of phosphorus reduction from the +5 to the +4 oxidation state was observed. Both resultant structure types are based on lanthanide thiophosphate sheets with the alkali cations located between them. Magnetic susceptibility measurements were conducted and revealed Curie-Weiss behavior of the samples, with a Van Vleck contribution in the CsSmP₂S₇ sample. UV-vis data was found to be in good agreement with the literature, indicating little influence of the sulfide environment on the localized 4f orbitals.

Scandium Selenophosphates: Structure and Properties of K4Sc2(PSe4)2(P2Se6)

The new compound K4Sc2P4Se14 was synthesized via the polychalcogenide flux method. It crystallizes in the space group C2/c, and the structure is composed of (1)/∞[Sc2P4Se14(4-)] chains that are separated by K(+) cations. The structural motif features two [PSe4](3-) units and one [P2Se6](4-) unit bridging the Sc centers and has not been reported for any other compound. The (1)/∞[Sc2P4Se14(4-)] chains pack in a crosshatched pattern perpendicular to the c axis of the crystal, forming channels for half of the K(+) atoms while the other half occupy empty space between the chains. The orange-yellow crystals of K4Sc2P4Se14 are air-sensitive and gradually turn red over the course of a couple hours. The band gap of the phase is 2.25(2) eV, and Raman spectroscopy shows the symmetric stretches of the selenophosphate groups to be at 231 and 216 cm(-1) for the [PSe4](3-) and [P2Se6](4-) units, respectively. Solid-state (31)P MAS NMR of K4Sc2P4Se14 shows two prominent peaks at 11.31 and -23.07 ppm and one minor peak at -106.36 ppm, most likely due to degradation of the product or an unknown second phase.

A recipe for new organometallic polymers and oligomers? Synthesis and structure of an oligo- and a polymeric arrangement of P–S anions

A route to organometallic polymers and oligomers is described using metal complexes with P/S-ligands as examples.

KCaEr2CuS5: A New Pentanary Rare-Earth Layered Chalcogenide without Substitutional Disorder

A new pentanary rare-earth chalcogenide without substitutional disorder, KCaEr2CuS5, was obtained from reaction of the Er-Ca-Cu-S precursor with KBr flux by either a two-step flux method or a direct reaction of the mixture of the binary components (1Cu2S:2Er2S3:3CaS) with excess KBr as flux. KCaEr2CuS5 crystallizes in the orthorhombic space group Cmcm (No. 63) with a = 3.9327(5) A, b = 13.410(2) A, c = 17.042(2) A, V = 898.8(3) A(3), Z = 4, R = 0.0632, and Rw = 0.0627. The KCaEr2CuS5 structure consists of four different building units: ErS6 octahedra, CaS6 octahedra, CuS4 tetrahedra, and KS6 trigonal prisms; it is characterized by [Er2CuS5]3- layers that are formed by the interconnection of double ErS6 octahedral chains with CuS4 tetrahedral chains in the a-c plane. K+ and Ca2+ cations are located in the cavities defined by S2- anions between the [Er2CuS5]3- layers. KCaEr2CuS5 is a semiconductor with an estimated band gap of 2.4 eV and shows a Curie-Weiss paramagnetic behavior in the 5-300 K range.