2p 2s Research Articles

Intercalation of ferrocene into Cd 2P 2S 6(CoCp 2) 0.8

We report the intercalation of ferrocene into Cd 2P 2S 6(CoCp 2) 0.8. The Cd 2P 2S 6 was first intercalated with cobaltocene, and then this intercalated material was reacted with ferrocene. Mass spectroscopy provides direct evidence for the presence of ferrocene in the Cd 2P 2S 6 host lattice. ESR measurements suggest that after the insertion of ferrocene into Cd 2P 2S 6(CoCp 2) 0.8, the concentration of neutral cobaltocene within Cd 2P 2S 6 is significantly reduced. X-ray diffraction and chemical analysis provide additional characterization.

ESR studies of inter- and intra-lamellar cation exchange processes in Cd 2P 2S 6

The transition metal chalcogenides, M 2P 2S 6 (M = divalent transition metal cation), are lamellar materials that undergo an unusual cation exchange process when their crystals are placed in contact with a solution of a transition metal salt. EPR spectroscopy has been used to examine the exchange of paramagnetic Co 2+ for Cd 2+ in diamagnetic Cd 2P 2S 6. It has been possible to study the uptake of ions by the lamellar lattice and to examine the cation coordination environment through its effect on the parameters of the spin-Hamiltonian. In order to extract details of the Co 2+ coordination from the observed EPR spectra, theoretical values of the g-value have been computed as a function of several crystal field parameters. The results for Co 2+ are compared with previous results for the insertion of Mn 2+ into Cd 2P 2S 6 by cation exchange. The relative occupancy of the inter- and intra-lamellar sites is a function of the cation type and the solvent employed.

Investigations of Mn(pyr)(aq) +2 and pyridine intercalated Cd 2P 2S 6 lattices: mechanism of intercalation and perturbation of the host lattice

The lamellar transition metal Chalocogeno-Phosphates (M 2P 2S 6) form an important family of two-dimensional semiconducting materials. The lamellar structure is formed by stacking S-M 2 3 -(P-P) 1 3 -S units along a unique crystallographic axis. Under appropriate conditions, guest species can enter the space between the layers to form intercalation compounds. Two main mechanisms are presently proposed for the intercalation reaction: electron transfer from guest to host lattice and cation exchange between cationic intercalated species and lattice metal ions. Both mechanisms create structural and electronic perturbations which often result in a dramatic modification of the chemical and physical properties of the host lattice. This paper describes the experimental evidence for the mechanisms of intercalation and creation of perturbation in the host lattices. Electron Spin Resonance spectroscopy has revealed cation migration between inter- and intralamellar cationic sites, supporting the cation exchange mechanism for the intercalation of solvated cationic species. Photoluminescence studies of Lewis base molecules intercalated into M 2P 2S 6 have shown a broadening of the conduction band due to the insertion of defects level near the band edges. Complementary measurements utilizing Optically detected Magnetic Resonance Spectroscopy demonstrated the presence of a strongly coupled donor-acceptor pair created upon intercalation via charge transfer mechanism.

FTIR electronic spectra of Fe 2P 2S 6 and Co 2P 2S 2: Trigonal field splitting and lithium intercalation effects

The FTIR electronic absorption spectra of single crystals of Fe 2P 2S 6, Co 2P 2S 6 and their lithium intercalation compounds have been obtained. The spectrum of Fe 2P 2S 6 exhibits a broad, weak absorption feature at 1885 cm −1 and a second, stronger band at 8870 cm −1. These are assigned to transitions between the 5 E g (ground state) and the 5 A 1 g and 5 E g trigonal crystal-field components of the Fe 2+ free-ion 5 D ground term. The broad absorption bands in the spectrum of Co 2P 2S 6 are assigned to the transitions between the 4 A 2 g (ground state) and the 4 E g (1224cm −1) and 4 A 1 g (7124 cm −1) trigonal crystal-field components of the Co 2+ free-ion 4 F ground term. A point-charge crystal-field model was used to relate the crystal-field splitting parameters ( Dq and Cp) to the trigonal lattice distortion. Lithium intercalation completely suppresses the trigonal field transition in Co 2P 2S 6 and causes a dramatic shift of the absorption edge to lower frequencies. However, lithium intercalation has little effect upon the spectrum of Fe 2P 2S 6.

Observation of an intensity anomaly in the 3s23p 2P1/2,3/2-3s3p2 2S1/2 and 2P1/2 resonance transitions in the Al I isoelectronic sequence

The intensity ratio of the two fine structure components in the 3s23p 2PJ–3s3p 2S1/2 and 2P1/2 resonance transitions has been measured in Al-like S IV, Cl V, Ar VI and Ti X, using the beam-foil technique. Unexpectedly large deviations from the LS ratios are found, particularly in the 2P–2S case. Although these deviations can be understood qualitatively from theoretical calculations (also reported), large quantitative discrepancies are observed in the beginning of the sequence.

ESR studies of metallocene intercalated Cd 2P 2S 6

Cd 2P 2S 6 exhibits a layered crystal structure that may be intercalated with metallocenes. The ESR spectra of Cd 2P 2S 6 single crystals intercalated with cobaltocene, nickelocene and chromocene have been examined over the temperature range 280–4.2 K. The spectra indicate that both oxidized and unoxidized metallocene is present in the van der Waals gap of the layered host lattice. Examination of the angle dependence of the ESR spectra establishes the orientation of neutral cobaltocene and nickelocenium cation with the C 5 molecular symmetry axis parallel to the C * axis of the host lattice. The orientation of chromocenium cation is rotated 90° to place C 5 perpendicular to C *.

Neuartige Phosphor/Schwefel-Liganden in aus Cp★ 2 Mo 2(CO) 4 (Cp★ = η 5-C 5Me 5) und P 4S 3 erzeugten Cp★ 2Mo 2P xS y- Komplexen (× = 2, 4; y = 5 - ×)

The reaction of Cp★ 2Mo 2(CO) 4( Mo Mo) (Cp★ = η 5-C 5Me 5) with P 4S 3 in boiling toluene gives the complexes Cp★(CO) 2MoP 3 (I), Cp★ 2(CO) 4Mo 2P 2 (II), Cp★ 2Mo 2P 2S 3 (III), and Cp★ 2Mo 2P 4S (IV). The structures of III and IV follow from their 31P NMR spectra as well as from an X-ray diffraction analysis of their corresponding Cr(CO) 5 monoadducts (VII and VIII). Characteristic features of the structure of VII are an η 2-PS and an η 3-P 3 ligand in a plane perpendicular to the MoMo axis, which is bisecting. A similar geometry is found for VIII, which, however, contains an η 2-S 2 and an η 3-P 2S ligand. Coordination of the Cr(CO) 5 fragment to the P 2S ligand in III may either occur at an S atom, which then acts as a μ 5-bridge (VIII) or at a P atom as manifested by the presence of a PW coupling in the W(CO) 5 adduct (VI).

Multiple empty tunnels in a new TaPS phase: Synthesis and structure determination of Ta 2P 2S 11

Ta 2P 2S 11 is a new phase of the TaPS system obtained by high-temperature synthesis from the elements. Single-crystal diffraction analysis showed the phase to crystallize in the P2 1 c space group with the following cell parameters: a = 6.876(3), Å, b = 24.109(8)Å, c = 26.411(8), Å, β = 106.04(3)°, V = 4208(6), Å 3, and Z = 10. Low-temperature ( T = 140 K) structure study has been performed and 3104 independent diffractometer data have been refined, with 328 variables, to R = 8.9%. The structure is made of two types of polyhedra, a tetrahedral group (PS 4) (mean d PS = 2.030, Å) and a bipolyhedral group (Ta 2S 11) (mean d TaS = 2.494, Å) in which tantalum is heptacoordinated. These (Ta 2S 11) units are formed of two distorted (TaS 7) groups sharing a triangular face made of mono- and disulfide anions ((S 2) −IIS −II). Of the three kinds of (Ta 2S 11) bipolyhedra, two of them show disorder of the common triangular sulfur face. The way the coordination groups are bonded to one another determines the occurrence of three kinds of tunnels in the structure. Their characteristics and the reason of their emptiness are related to their size and to the special linking arrangement taking place between the (PS 4) and (Ta 2S 11) groups. With the formulation Ta V 2P V 2(S 2) −II(S −II) 9 the phase is expected to be diamagnetic and semiconducting or insulator.

Spectroscopic and ESR studies of Cd 2P 2S 6 intercalated with pyridine complexes of ferric ion

Cd 2P 2S 6 crystallizes in a layered structure which is readily intercalated with a variety of Lewis bases. We have studied the intercalation reactions of this lattice with pyridine complexes of several transition metal ions and Ce 4+. In some instances (e.g. Mn 2+) the metal ion could be co-intercalated with pyridine with little or no effect on the distribution of reaction products formed within the van der Waals gap. However, certain transition metal ions had a dramatic effect on the product distribution obtained. Co-intercalation of Fe 3+, for example, results in the production of a highly colored polysulfide species within the van der Waals gap. The intercalated species were identified by mass spectroscopic analysis during thermal de-intercalation. The co-intercalated paramagnetic transition metal ions are useful as ESR spin-probes for the study of the structure and dynamics of the intercalate layer. Analysis of the ESR spectra indicate that co-intercalated Mn 2+ can enter Cd 2+ lattice vacancies at elevated temperatures.

Analysis of the ESR spectrum of manganese (II) in the layered compound Cd 2P 2Se 6

The Q-band and X-band ESR spectra of Mn 2+ in the layered compound Cd 2P 2Se 6 are reported. The Mn 2+ is in a trigonal environment coordinated to six selenium atoms. The parameters of the spin hamiltonian have been determined and reasonable agreement is obtained between theory and experiment with g | = 2.01, g ⊥ = 2.05, ¦ D¦ = 0.286 cm −1, ¦ A¦ = 70.0 × 10 −4 cm −1. The results of the ESR analysis are compared with previous studies of the analogous layered compound Cd 2P 2S 6. The Mn(II) crystal-field splitting parameter D increases approximately eight-fold from that in the sulfide lattice. The exceptionally large crystal-field splitting is correlated with the layered structure of the lattice and the MnSe bond covalency. It is concluded that the dominant effect is that of the bond covalency.

Photoluminescence studies of layered transition metal phosphorus chalcogenides and their pyridine intercalation compounds

Ultraviolet photoexcitation of Cd 2P 2S 6 and Zn 2 P 2 S 6 single crystals produces a characteristic photoluminescence between 2.5 and 1.5 eV. Mn 2P 2S 6 exhibits only low energy emission due to transitions between localized d-orbital states. These results are consistent with the electronic band structure model for transition metal phosphorus chalcogenides with the general chemical formula M 2P 2X 6 (Cd, Zn, Mg, Mn, X = sulfur or selenium), which predicts highly localized states associated with the transition metal d orbitals and delocalized, band-like states derived from sulfur and phosphorus orbitals. When pyridine containing a small amount of water is intercalated into Cd 2P 2S 6, the excitation and the photoluminescence spectra are changed substantially. The photoluminescence intensity increases approximately tenfold and the position of the excitation edge is shifted to lower energy by 0.5 eV. Intercalation with anhydrous pyridine does not affect either the excitation spectrum or the photoluminescence spectrum of the host lattice.

Deuterium NMR of pyridine intercalated cadmium chalcogenophosphate

Deuterium NMR spectra of the intercalation complexes of lamellar Cd 2P 2S 6 with various deuterated pyridine molecules are reported. The measurements indicate that the pyridine molecules lie within the chalcogen van der Waals gaps with their molecular planes parallel to the chalcogen layers. Between room temperature and −60°C the pyridine molecules reorient rapidly (on the NMR time scale) about an axis perpendicular to their molecular plane.

Preparation, properties and structure of di-(acetamidinium)-difluoropentathiodiphosphate

Plate-shaped, colorless crystals were grown from a solution, originating with the reaction of P 4S 10 and NH 4F in CH 3CN. By a molar ratio of 4NH 4F/P 4S 10, third of P 4S 10 reacted to Di-(acetamidinium)-difluoropentathiodiphosphate, [CH 3C(NH 2) 2] 2P 2S 5F 2. Crystals are melting in the range of 134 – 142 °C under their decomposition. The crystal structure has been determined from three-dimensional MoK β data, collected on a CAD-4 diffractometer. It crystallizes in the space group C2/c with four formula units in a cell of dimensions a = 10.600(5) b = 10.069(5) c = 15.129(8) Ā β = 92,35(5)° with V = 1613.4 Ā 3, D o = 1,557 g.cm −3, D o 1.49 g.cm −3. The structure was solved by the direct methods program system MULTAN 82 and anisotropically refined by least-squares techniques to a final R = 0,037 based on 966 independent intensities. The hydrogen atoms were located from a difference map. The difluoropentathiodiphosphate-anion consists of two PS 3F-tetrahedra which are connected together by a common sulfur atom. This bridge-atom occupies a special equivalent position on a twofold rotation axis, therefore the anion shows the point symmetry 2. Bond distances and angles within the tetrahedra have the usual values (P-S bridge = 2,075(1) Ā, P-S terminal = 1.951(1) and 1.944(1) Ā, P-F = 1.577(2) Ā), < P-S-P = 107.8(1)°. The nitrogen- carbon-atoms of the acetamidinium-cation are lying in plane. Bonds lengths are: CC = 1.485(5) Ā, CN = 1.301(4) and 1.280(5) Ā. There are hydrogen bonds in the structure.

Far infrared spectra of hexachalcogenohypodiphosphates

The far infrared (fir) reflection spectra of the hexachalcogenohypodiphosphates M 2P 2 X 6 ( M = Mg, Cd, Mn, Fe, Co, Ni, Pb, Sn; X = S, Se) have been studied. TO LO splittings are determined from Kramers-Kronig analyses, the splitting is large for the lattice vibration modes of ferroelectric Sn 2P 2S 6 but very small for Ni 2P 2S 6. Measurements with polarized light permit an assignment of the A 2u and E u modes of the ethane like P 2S 6 units in Mn 2P 2S 6. Factor group analyses were performed for all hitherto described hexachalcogenohypodiphosphates. The fir absorption spectra of the less symmetric compounds Hg 2P 2S 6, Hg 2P 2Se 6, Ca 2P 2S 6, TiP 2S 6, In 4 3 P 2S 6, In 4 3 P 2Se 6 , and CuCrP 2S 6 are given.

Vibrational study of the [P 2S 4−6] anion, of some MPS 3 layered compounds ( [formula omitted]), and of their intercalates with [Co( η5-C 5H 5) +2] cations

The infrared and Raman spectra [10–3100 cm −1] have been recorded for aqueous solutions and polycrystalline samples of Na 4P 2S 6 · 6H 2O as well as for several lamellar MPS 3 (or M 2P 2S 6) compounds with M = Fe, Co, Ni, In 2 3 and their intercalates with cobalticenium cations. A complete assignment of the observed spectra is proposed and a normal coordinate analysis of the [P 2S 4− 6] anion is carried out; this allows proposal of a new assignment, for the spectra of the layered MPS 3 host systems which is slightly modified with respect to prior work. A detailed analysis of the infrared and far-infrared spectra is also reported for the intercalates with [Co( η 5-C 5H 5) + 2] cations. From these results, it is concluded that the mechanism of the electronic transfer during the intercalation process depends on the nature of the metal: when M = Co or Ni the main reduction site is the PP bond, while when M = Fe (and perhaps also Mn) the reduction involves mainly the metal ion itself.

In situ electron spin resonance spectroscopy studies of electrode processes

The usefulness of ESR spectroscopy for studying electrode processes is discussed and then illustrated by two selected examples. The first one deals with the identification of a radical intermediate in the electroreduction of some naphthazarin derivatives. The second example shows the possibility of elucidating the mechanism of electron exchange inside an electrode material, such as M 2P 2S 6, during its electroreduction with simultaneous intercalation of lithium ions.

Ferroelectricity in Sn 2P 2S 6

Tin-hypothiodiphosphate, Sn 2P 2S 6 (monoclinic; a=6.529, b=7.485, c=11.317 A ̊ ; ß=124.11°; space group Pc) has been found to be ferro-electric. At 20°C the spontaneous polarization is 14 μCoulomb/cm 2 in the [101] direction. The coercive field is 750 V/cm.

Vapour growth and crystal data of the thio(seleno)-hypodiphosphates Sn 2P 2S 6, Sn 2P 2Se 6, Pb 2P 2Se 6 and their mixed crystals

Single crystals (monoclinic polyhedra up to 5×5×5 mm 3) of the thio(seleno)-hypodiphosphates Sn 2P 2S 6 (yellowish-brown), Sn 2P 2Se 6 (black), Pb 2P 2S 6 (yellow) and Pb 2P 2Se 6 (dark-red) have been grown by vapour transport with iodine. The space group of Sn 2P 2S 6 is Pc, that of the other compounds P2 1/c. All four compounds are completely miscible. Already small replacements of Sn by Pb (around 10 mole %) in Sn 2P 2S 6 change the space group to P2 1/c. The pure as well as the 1:1 mixed-anion and mixed cation compounds were characterized by x-ray and thermal analysis.

Crystal growth of metal-phosphorus-sulfur compounds by vapor transport

Single crystals of the thio-phosphates: Cu 3PS 4, InPS 4, GaPS 4, BiPS 4 and the thio-hypophosphates Sn 2P 2S 6, Cd 2P 2S 6, Fe 2P 2S 6 and Mn 2P 2S 6 were grown in sizes up to 10 mm by vapour transport with iodine. Lattice parameters and space groups are given.