Skip to main content
NCBI home page
ACS AuthorChoice logoLink to ACS AuthorChoice
. 2026 Jun 16;148(25):26555–26563. doi: 10.1021/jacs.6c06234

Pressure-Induced Stabilization of Terbium(IV) in CsTb(CrO4)2 Characterized by X‑ray Absorption Spectroscopy

Tyler W Hines †, Lucia Amidani ‡,§, Nicholas B Beck †, Kacy N Mendoza †, Christoph Sahle ∥, Joseph M Sperling †, Sami Vasala ‡,§, Kristina O Kvashnina ‡,§,*, Thomas E Albrecht †,*
PMCID: PMC13339621  PMID: 42301761

Abstract

Single crystals of CsTb­(CrO4)2 and CsDy­(CrO4)2, where the lanthanide metals are in the trivalent state under ambient conditions, have been investigated under high-pressure conditions on the gigapascal scale utilizing a diamond anvil cell. These compounds were characterized by single-crystal X-ray diffraction in addition to high-pressure solid-state UV-vis-NIR spectroscopy, Raman spectroscopy, and Tb L3-edge high-energy-resolution fluorescence-detected X-ray absorption near-edge structure (HERFD-XANES). The high-pressure UV-vis-NIR spectra reveal strong broadening of the metal-to-ligand charge transfer band to lower energies, associated with a visible color change from yellow to dark red/black. Clear evidence for the stabilization of Tb4+ under high pressure is provided by the appearance of a second edge feature characteristic of Tb4+, starting at 19.62 GPa in the high-pressure L3-edge HERFD-XANES at around 7528 eV. This represents the first example of Tb4+ being stabilized by high pressure and expands upon the limited chemistry of terbium in the tetravalent state.

graphic file with name ja6c06234_0008.jpg

graphic file with name ja6c06234_0006.jpg

Introduction

The chemistry of the lanthanide elements is dominated by the most stable 3+ oxidation state across the series, owing to the core-like behavior of the valence 4f electrons. However, some lanthanides can be stabilized in the divalent or tetravalent state, given appropriate ligands and coordination geometry. − Of these, the divalent lanthanides are more widely used, mostly as strong, one-electron reductants in organic synthesis, as exemplified by the use of SmI2 and its derivatives. Additionally, stabilization of divalent lanthanides is generally much more achievable, with examples of every lanthanide (except radioactive promethium) isolated in the divalent state. − Of the lanthanides, the divalent oxidation state is most common for Eu and Yb, stemming from their divalent electronic configuration, which results in a half-filled 4f 7 (Eu2+) or filled 4f 14 (Yb2+) subshell. ,

Similarly, although the tetravalent state in the lanthanides is more elusive, the stabilization provided by the 4f 0 and 4f 7 electron configurations in cerium and terbium provides Ln3+/4+ oxidation potentials of −1.6 V and −3.1 V, respectively, resulting in molecules and materials that can be isolated, albeit with difficulty for Tb4+. Ce is by far the most common due to the much lower Ce3+/4+ oxidation potential of −1.6 V, with examples of molecular complexes stabilized under atmospheric conditions, such as the common Ce4+ starting material, ceric ammonium nitrate. Contrasting this with Tb4+ and Pr4+, the difficulty of stabilizing these two states is obvious, given the limited number of molecular complexes isolated in the solid state and the stringent anaerobic conditions and carefully designed ligands necessary to stabilize them. − This does beg the question, however, of whether the physical compression of a hard donor ligand–metal ion bond can stabilize higher oxidation states, as described by Pearson’s Hard Soft Acid Base (HSAB) Theory.

Pressure-induced valence transitions in lanthanide compounds are known; however, they are largely limited to the divalent-to-trivalent transition of the metals, monochalcogenides, and intermetallic compounds of europium, samarium, thulium, and ytterbium that are readily accessible in their +2 states. − Ce is the only lanthanide element with literature precedent to undergo a pressure-induced valence fluctuation from trivalent to tetravalent in the metallic phase, in addition to some chalcogenide, pnictide, and intermetallic compounds. ,−

Outside of the f elements, pressure-induced valence changes have been demonstrated in examples that include FeTiO3, TlReO4, CuFeO2, BiNiO3, and PbCrO3. ,− Chromium specifically exhibits a wide variety of stable oxidation states from −2 to +6, leading to rich redox chemistry, as evident by the pressure-induced stabilization of Cr4+ at 4.2 GPa in PbCrO3. For the f block elements specifically, Cs2[(UO2)2(CrO4)3] and Dy­(CrO4) compounds have been synthesized, stabilizing chromium in the rare Cr5+ oxidation state that commonly undergoes disproportionation. , Additionally, the compound CsAm­(CrO4)2 with chromium in its common +6 state, exhibits a broad, low-energy 5f → 6d metal-to-ligand charge-transfer (MLCT) band that arises from the accessible Am4+ state (Am3+/4+ = −2.62 V vs S.H.E). The low-energy MLCT band in CsAm­(CrO4)2, stabilization of Cr5+ in Ln­(CrO4), and pressure-induced charge transfer through bridging O2– anions in similar systems suggest that trivalent rare earth compounds with chromate anions in their common +6 oxidation state may facilitate the stabilization of lanthanides in the tetravalent state with the application of pressure. ,−

Herein, the possibility of pressure-induced oxidation of lanthanides is investigated in CsLn­(CrO4)2 (Ln3+ = Tb3+ and Dy3+). These compounds have been characterized using high-pressure UV-vis-NIR and Raman spectroscopies, in addition to high-pressure Tb L3-edge high-energy-resolution fluorescence-detected X-ray absorption near-edge structure (HERFD-XANES) for CsTb­(CrO4)2. Utilizing these methods, we report evidence of the pressure-induced stabilization of Tb4+ in CsTb­(CrO4)2.

Experimental Section

Materials

Cs2CrO4 (99.5%, Alfa Aesar), HNO3 (ACS reagent, 70%, Sigma-Aldrich), Tb4O7 (99.9%, Sigma-Aldrich), and Dy2O3 (99.9%, Sigma-Aldrich) were used as received. Ln­(NO3)3·nH2O (Ln3+ = Tb3+, Dy3+) were synthesized by dissolving the respective lanthanide oxide in concentrated HNO3, followed by drying to completeness resulting in crystalline Ln­(NO3)3·nH2O. These nitrates were assumed to be in the hexahydrated Ln­(NO3)3·6H2O form.

Syntheses

CsLn­(CrO4)2 (Ln = Tb, Dy) were synthesized in a hydrothermal reaction based on previous methods by Galley et al. The synthesis of CsCe­(CrO4)2 was attempted, but the addition of Cs2CrO4 to Ce­(NO3)3·6H2O resulted in the immediate oxidation of cerium and produced brown amorphous powder products. In a typical synthesis, 0.2 mmol Ln­(NO3)3·6H2O, 0.4 mmol Cs2CrO4, and 2 mL H2O were loaded into a 23 or 11 mL PTFE-lined autoclave. The autoclaves were sealed and heated at 200 °C for 48 h in a box furnace and allowed to cool to room temperature over 48 h (cooling rate ∼3.7 °C/h). The resulting product was filtered, washed with deionized water to remove excess Cs2CrO4, and dried. This yielded well-faceted orange or yellow single crystals with a block crystal habit for CsTb­(CrO4)2 and CsDy­(CrO4)2, respectively. The bulk material can be viewed in the Supporting Information (Figure S1). Yields for these syntheses were greater than 54% (Table S1).

Crystallographic Studies

Single crystals of CsTb­(CrO4)2 and CsDy­(CrO4)2 were submerged in immersion oil and placed on a 75 μm diameter MiTeGen loop. The loops with CsTb­(CrO4)2 and CsDy­(CrO4)2 were mounted on the goniometer of a Bruker D8 Quest diffractometer and aligned with the incident X-ray beam using a digital camera integrated with the ApexV software. Collection strategies were calculated and optimized using the ApexV software. The data were collected with Mo Kα (λ = 0.71093 Å) radiation source at 100 K for CsTb­(CrO4)2 and 150 K for CsDy­(CrO4)2 using an Oxford 1000 cryostream. The CsTb­(CrO4)2 structure was refined on the Olex2 v1.5 software using the SHELXT structural solution and SHELXL structural refinement. − The CsDy­(CrO4)2 structure was refined on the Olex2-v1.5 software using the SHELXS structural solution and SHELXL structural refinement. − Powder X-ray diffraction was collected on a Bruker D2 Phaser between 2θ angles of 5° and 50°. Powder patterns can be found in the Supporting Information (Figures S3–S4).

Ambient Pressure Solid-State UV-vis-NIR Spectroscopy

Single crystals of CsTb­(CrO4)2 and CsDy­(CrO4)2 were placed on a glass slide and submerged in immersion oil. The solid-state UV-vis-NIR transmission data for these samples were collected on a CRAIC Technologies microspectrometer at room temperature. Data were collected between 320 and 1700 nm, and collection times were optimized by the CRAIC Minerva software.

Ambient Pressure Solid-State Raman Spectroscopy

Single crystals of CsTb­(CrO4)2 and CsDy­(CrO4)2 were placed on a glass slide. The solid-state Raman spectra were collected on a Bruker Senterra II Raman microscope by using a 785 nm laser at a power of 100 mW, with 20 coadditions and an integration time of 1000 ms. Raman spectra were baseline-corrected in the OPUS 8.7.41 software.

Ambient Pressure Solid-State X-ray Absorption Spectroscopy

HERFD-XANES at the Tb L3-edge was acquired on BM20 at the ESRF synchrotron facility. The incident energy was selected with a fixed-exit Si(111) double-crystal monochromator. A Rh-coated toroidal mirror was used to focus the beam to 2.5 × 0.075 mm on the sample. The horizontal size of the beam was reduced to 0.5 mm by using slits. HERFD-XANES was acquired by integrating a small bandwidth around the maximum of the Lα1 emission of Tb while scanning the incident energy across the Tb L3 absorption edge. The maximum of the Tb Lα1 emission line was selected by the fourth harmonic of 4 Ge(110) bent crystal analyzers mounted on a Johann-type X-ray emission spectrometer and working at a Bragg angle of 81.18°. The spectrometer was set to a 0.25 m Rowland radius and equipped with crystal analyzers bent at a 0.5 m radius to maximize the solid angle covered by the spectrometer. Data were processed using PyMCA software, including the normalization and background subtraction tools integrated therein. Quantification analysis was performed using ITFA software.

Single crystals of CsTb­(CrO4)2 were placed on a Kapton tape and mounted on the sample stage to collect ambient-pressure HERFD-XANES.

Variable Pressure UV-vis-NIR, Raman, and X-ray Absorption Spectroscopy

For the high-pressure UV-vis-NIR and Raman spectroscopy experiments, a 200 μm diameter hole was drilled into a stainless-steel gasket, indented to 100 μm, and mounted onto a DACTools (Naperville, IL, USA) SSDAC 80 diamond anvil cell (DAC). Single crystals of CsTb­(CrO4)2 and CsDy­(CrO4)2 were loaded into the mounted stainless-steel gasket along with ruby spheres as a pressure reference. − The gasket hole was filled with poly­(dimethylsiloxane) as the pressure medium to ensure hydrostatic transfer of pressure throughout the cell, and the cell was sealed. The ruby fluorescence was measured on a CRAIC Technologies microspectrometer with an excitation wavelength of 546 nm to determine the pressure inside the DAC at each pressure step. , Ruby fluorescence was fit to a Voigt function to determine the λmax. For the high-pressure X-ray absorption spectroscopy experiments, a 200 μm diameter hole was drilled into a beryllium gasket, indented to 100 μm, and mounted onto an mBX 110 diamond anvil cell. Single crystals of CsTb­(CrO4)2 were loaded into the mounted beryllium gasket along with ruby spheres as a pressure reference. − The gasket hole was filled with a 4:1 methanol:ethanol mixture as the pressure medium, and the cell was sealed. HERFD-XANES was not collected for CsDy­(CrO4)2. The ruby fluorescence was measured on a BETSA Pressure by Ruby Luminescence System at each pressure step. Ruby fluorescence was fit to a Voigt function to determine the λmax. Solid-state UV-vis-NIR, Raman, and X-ray absorption spectra were then collected at various pressures in the loaded DAC based on the methods above.

Results and Discussion

Both CsTb­(CrO4)2 and CsDy­(CrO4)2 crystallize in the monoclinic space group P2/c, isostructural to previously reported lanthanide chromates, with one crystallographically unique Ln3+ cation, Cs+ cation, and CrO4 2– anion in the asymmetric unit. , This layered structure is visualized in Figure (a) viewed along the c-axis. A picture of the asymmetric unit with thermal ellipsoid plots can be found in the Supporting Information (Figure S2). The CrO4 2– tetrahedra share corners and edges with the Ln3+ polyhedra to form layers, and these layers are separated by Cs+ cations filling the interlayer space. The Ln3+ and Cs+ cations sit on 2e (0, y, 1/4) and 2f (1/2, y, 1/4) Wyckoff positions, respectively, with 2-fold site symmetry. The Cr6+ cations sit on the 4g (x, y, z) general Wyckoff position. The local geometry (Figure (b)) of the Ln3+ polyhedra and CrO4 2– units is triangular dodecahedron with D 2d symmetry and tetrahedral with T d symmetry, respectively. Bond lengths, unit cells, and other crystallographic information are similar between the two structures, following the lanthanide contraction, and can be found in the Supporting Information (Tables S2–S3). Powder patterns can also be found in the Supporting Information (Figures S3–S4).

1.

1

Open in a new tab

Polyhedral representations for CsLn­(CrO4)2. (a) Depicts the extended structure viewed along the c-axis to visualize the layered structure, and (b) the eight-coordinate trigonal dodecahedral local geometry of the Ln3+ centers. Terbium/dysprosium, chromium, oxygen, and cesium atoms are represented by orange, yellow, red, and gray spheres, respectively. Tb3+/Dy3+ and CrO4 2– are represented by orange and yellow polyhedra, respectively.

Tracking the Laporte Forbidden f→f transitions of the f elements can provide insights into the underlying electronic structure and f electron perturbations as a function of pressure. − Unfortunately, Tb3+ 4f→4f transitions have the lowest probabilities in the lanthanide series. Additionally, the most intense transitions for Tb3+ are in the region of 350 to 400 nm and are obscured by the ligand-to-metal charge-transfer (LMCT) of the chromate oxoanion. The same is true for Dy3+ with the exception of the 6H15/2→6F5/2 transition at about 800 nm that is barely observed at ambient pressure to ca. 6 GPa (Figure S6) even though the molar absorptivity of this transition is about five times larger than the most intense Tb3+ peak (Figure b). At ambient pressure, without being in a DAC, several more 4f→4f transitions are observed (Figure S5). Thus, the 4f→4f transitions of Tb3+ and Dy3+ cannot be utilized to analyze the electronic structure of the lanthanide metal center as they have been in other recent high-pressure spectroscopic studies of the f elements. ,,,, Despite this, the charge-transfer and 4f→5d bands can still provide valuable information.

2.

2

Open in a new tab

High-pressure UV-vis-NIR absorption spectra of (a) CsTb­(CrO4)2 and (b) CsDy­(CrO4)2.

At ambient pressure, the solid-state UV-vis data reveal that CsTb­(CrO4)2 has a lower energy feature than that of CsDy­(CrO4)2 corroborating the darker orange color of the bulk CsTb­(CrO4)2 crystals (Figure S5). This lower energy feature is almost certainly a combination of 4f→5d and MLCT transitions, given that the Tb3+/4+ oxidation potential is lower than Dy3+/4+ and is the second most feasible in the lanthanide series, where even molecules with Tb4+ have now been synthesized. ,− ,, It has been known for over half a century that there is a linear correlation between these transitions and the ion’s redox behavior. , Additionally, the oxidizing power of CrO4 2– is enough to easily oxidize Ce3+.

As observed in Figure a, the MLCT band in CsTb­(CrO4)2 is clearly broadened to include lower energies with the application of pressure and is associated with a visual color change from yellow-orange to dark red/black, as observed in Figure (a). This suggests that the charge transfer from the Tb3+ cations to the CrO4 2– anions is becoming more favorable, shifting this associated transition to lower energies and indicating a closing of the bandgap and semiconductor behavior. Similar pressure-induced effects on the MLCT are observed in the berkelium complexes of Bk2[C6(CO2)6]­(H2O)8·2H2O and [(Bk­(pmtz)2(H2O)3)2(μ-pmtz)]2(pmtz)2·6H2O (pmtz– = 5-(pyrimidyl)­tetrazolate), where the pressure-induced red-shifting and broadening of the MLCT band is only observed for the berkelium complexes and is absent from the analogous curium and californium complexes. , This was attributed to the accessible Bk4+ state (Bk3+/Bk4+ = −1.4 V vs. S.H.E), causing charge transfer to become more favorable with the application of pressure. , Likewise, the strong shifting of the MLCT band for CsTb­(CrO4)2 could be due to the somewhat accessible Tb4+ state (Tb3+/Tb4+ = −3.1 V vs S.H.E).

3.

3

Open in a new tab

Pictures of crystals of (a) CsTb­(CrO4)2 and (b) CsDy­(CrO4)2 in a diamond anvil cell under increasing pressure.

However, one should not arrive at such conclusions with just this result. The pressure-dependent UV-vis-NIR spectra for CsDy­(CrO4)2 are presented in Figure b, where the lanthanide ion in this compound, Dy, is more redox-inert with a Dy3+/4+ oxidation potential calculated to be between −4.5 V and −5.2 V. There are a few known Dy4+ materials characterized in the literature, such as Cs3DyF7 that required F2(l) at 170 bar and 693 K to synthesize. Therefore, CsDy­(CrO4)2 was still deemed to be a redox-inert analog for CsTb­(CrO4)2 due to its more largely negative oxidation potential. ,− In CsDy­(CrO4)2, there is an extent of broadening and red-shifting of the LMCT band from the CrO4 2– despite the redox inactivity of the Dy3+ center. This likely does not include the lanthanide metal at all. Instead, this observation could be the result of charge transfer between neighboring chromate subunits that are brought closer together with the application of pressure. As the structure is compressed, the oxygen atoms are brought closer to a neighboring chromium metal center to the point of bridging and induce charge transfer to the neighboring chromium center. Thus, under this hypothesis, the color change in the CsDy­(CrO4)2 compound is attributed to charge transfer interactions between chromate units, similar to what is observed in common dichromate and trichromate salts, where these salts are typically a red-orange and red color, respectively. It should also be noted that the broadening of the MLCT band is reversible upon the release of pressure in both compounds (Figure S7).

To further analyze the origin of this color change for both of these lanthanide chromate compounds, high-pressure Raman spectroscopy was performed. This technique is commonplace in the general high-pressure literature because it can provide valuable information for structural changes and rearrangements that occur with the application of high pressure. − The high-pressure Raman spectra, separated into various wavenumber regions for CsTb­(CrO4)2 and CsDy­(CrO4)2 are provided in Figure . The full ambient-pressure and high-pressure Raman spectra, in addition to peak assignments, can be found in the Supporting Information (Figures S8–S9 and Tables S4–S5). At ambient pressure, the observed Raman modes of the CrO4 2– units were the ν2 symmetric bending between 330–360 cm–1, the ν4 antisymmetric bending between 380–450 cm–1, ν1 symmetric stretching between 865–885 cm–1, and ν3 antisymmetric stretching between 825–830 cm–1 and 965–975 cm–1. There are also low intensity Ln–O vibrational modes observed between 500–700 cm–1 and external lattice modes below 260 cm–1. −

4.

4

Open in a new tab

High-pressure Raman spectra of CsTb­(CrO4)2 in the regions of (a) 50–250 cm–1, (b) 250–800 cm–1, and (c) 800–1100 cm–1 in addition to high-pressure Raman spectra of CsDy­(CrO4)2 in the regions of (d) 50–250 cm–1, (e) 250–800 cm–1, and (f) 800–1100 cm–1.

Generally, the high-pressure effect on the Raman shifts in both lanthanide chromate compounds is similar, with substantial shifting to higher energy, broadening, splitting, and the diminishing of intensity at the highest pressures tested here. The shifting to higher energies observed here is due to the compression of the chemical bonds that causes these vibrational modes to occur at higher energy and is common in the literature. − ,, For the ν2 symmetric bending (330–360 cm–1) and ν4 antisymmetric bending (380–450 cm–1) modes in CsTb­(CrO4)2 (Figure b) and CsDy­(CrO4)2 (Figure e), similar pressure-induced effects are observed, where these signals are shifted to higher energies, broadened, decrease in intensity, and eventually substantially overlap to the point where some modes cannot be differentiated.

The difference between these two compounds can be observed in the high- and low-wavenumber regions. In the high-wavenumber region of 800–1100 cm–1 for CsTb­(CrO4)2 (Figure c), the ν1 symmetric stretch at 864 cm–1 with a shoulder at higher wavenumbers, is split to a larger degree, resulting in three distinct peaks at 11.45 GPa. At ambient pressure for CsDy­(CrO4)2, two peaks are observed at 870 cm–1 and 883.7 cm–1, but under pressure, no further splitting of these two signals is observed (Figure f). As for the low-wavenumber region below 250 cm–1 that contains the external lattice vibrations, significant changes can be observed in the high-pressure spectra of CsTb­(CrO4)2 (Figure a) starting at 10.14 GPa, with splittings of the peaks around 100, 140, and 185 cm–1 of the previous pressure step of 4.70 GPa, as well as more peaks arising below 100 cm–1. Comparing this to CsDy­(CrO4)2, there are less obvious changes that occur in the pressure-dependent Raman spectra in the phonon region (Figure d), but concrete conclusions are difficult to draw based on this data due to the overall diminished intensity of the Raman signals with the application of pressure. Despite this, with the significant changes under pressure for the CsTb­(CrO4)2 compound compared to the redox-inert CsDy­(CrO4)2 in the ν1 symmetric stretches and the phonon modes, there seems to be a rearrangement of the lattice that could be a sign of underlying redox chemistry occurring between the Tb3+ metal center and the coordinating CrO4 2– anions.

To finally determine the origin of the effects observed in the high-pressure UV–vis-NIR and Raman spectra for CsTb­(CrO4)2, high-pressure Tb3+ L3-edge high-energy-resolution fluorescence-detected X-ray absorption near-edge structure (HERFD-XANES) was performed and is provided in Figure . At ambient (Figure S10) and low (Figure ) pressures, a single intense edge feature is observed around 7517 eV, consistent with Tb3+.

5.

5

Open in a new tab

High-pressure Tb L3-edge HERFD-XANES spectra for CsTb­(CrO4)2.

Upon compression, the ingrowth of a second edge feature around 7528 eV is observed starting at 19.62 GPa and grows in intensity with the subsequent increase in pressure up to an experimental limit of 40.92 GPa. The appearance and growth of this peak are also correlated with a decrease in the peak intensity of the characteristic Tb3+ peak around 7517 eV as the pressure increases. Peak positions of the high-pressure HERFD-XANES spectra are reported in the Supporting Information (Table S6). The ingrowth of the 7528 eV peak is consistent with the existence of Tb4+, as indicated by previous L3-edge XAS spectra for Tb4+ complexes. ,− For reference, recent reports of L3-edge XAS spectra found these characteristic Tb4+ double-edge features at 7518.9 and 7526.1 eV for TbO2 and 7520.3 and 7528.5 eV for [Tb4+(NP­(1,2bis- t Bu-diamidoethane)­(NEt2))4]. , Comparing these data to the Tb3+ L3-edge HERFD-XANES reported here, this L3-edge HERFD-XANES data provides strong evidence that tetravalent terbium is stabilized in CsTb­(CrO4)2 with the application of pressure in a DAC starting at 19.62 GPa. Furthermore, the percentage of Tb4+ stabilized at the reported pressure steps was quantified as 3% at 19.62 GPa, 21% at 25.71 GPa, 25% at 32.08 GPa, and 27% at 40.92 GPa. The relative concentration error was estimated to be on the order of 5%, as defined by the ITFA package. It should also be noted that the pre-edge feature around 7508 eV is unaffected by pressure up to an experimental limit of 40.92 GPa.

The contributions from the two Tb oxidation states were quantified using iterative transformation factor analysis (ITFA) and Athena software. It was found that ITFA produced higher-quality peak fittings than Athena, so ITFA was chosen for the quantification provided here (Figure S12). The ITFA procedure was applied to the normalized and as-measured Tb L3 HERFD-XANES spectra. The analysis was carried out in several steps. First, principal component analysis (PCA) was performed to determine the number of components contributing to the HERFD-XANES spectra. The PCA results indicated that the spectra are well reproduced by a linear combination of two components, corresponding to Tb3+ and Tb4+, while the third, fourth, fifth, sixth, and seventh components show no significant contributions. In the second step, CsTb­(CrO4)2 at 1.22 GPa and TbO2 under ambient conditions were used as standards and assumed to contain 100% Tb3+ and 100% Tb4+, respectively. The iterative target test (ITT) procedure was then applied to determine the relative concentrations of the two components as reported above. The relative concentration error was estimated to be on the order of 5%, as defined by the ITFA package.

It should be noted that with the partial oxidation of Tb3+, there must also be some chemical species that are reduced. Owing to the rich redox chemistry of Cr, it is likely that Cr6+ is partially reduced to Cr5+, as Tb4+ is stabilized under pressure. To evaluate this hypothesis, Cr L3-edge HERFD-XANES was performed on CsTb­(CrO4)2 inside the DAC; however, Cr6+ impurities were found in the beryllium gasket alloy that houses the sample. This caused the signal of the single crystal of CsTb­(CrO4)2 to be heavily overshadowed by the signal produced from the Cr6+ in the beryllium gasket, and the partial reduction of Cr6+ was unable to be experimentally confirmed by these methods. Nonetheless, the appearance of double-edge features at 7517.49 and 7528 eV in the high-pressure Tb L3-edge HERFD-XANES provided sufficient evidence that the Tb4+ is stabilized under high pressure starting at 19.62 GPa, and this is likely associated with the concurrent partial reduction of Cr6+ to Cr5+.

Conclusions

The high-pressure Tb L3-edge HERFD-XANES, supplemented with high-pressure UV-vis-NIR and Raman spectroscopy reported here, supports the stabilization of Tb4+ in CsTb­(CrO4)2 starting at 20 GPa and increasing the Tb4+ content with additional pressure. This represents the first example of pressure-induced oxidation of Tb to stabilize the tetravalent state and thus provides an alternative pathway for accessing the tetravalent state without the need for an inert atmosphere or extreme oxidants. These results suggest that accessing uncommon high-valent oxidation states in the f elements may be more achievable than previously perceived by applying high pressure.

The pressure that Tb4+ is first observed is associated with an almost completely diminished signal in the Raman spectrum and a dark red/black color of the crystal, stemming from the red shifting of the MLCT band as indicated by the high-pressure UV-vis-NIR spectra. Comparing CsTb­(CrO4)2 to CsDy­(CrO4)2 with the more redox-inert dysprosium lanthanide ion, the high-pressure Raman and UV-vis-NIR spectra yield similar results. Previous reports have attributed pressure-induced red shifting of an MLCT band to other accessible oxidation states in the lanthanides and actinides, but the similar results presented here for CsDy­(CrO4)2 suggest that one must be careful when making this conclusion. The red shifting of the broad LMCT band for CsDy­(CrO4)2 could instead be due to charge-transfer effects between nearby CrO4 2– units that are amplified under pressure.

Supplementary Material

ja6c06234_si_001.pdf (817.8KB, pdf)

Acknowledgments

We acknowledge the European Synchrotron Radiation Facility (ESRF) and Helmholtz-Zentrum Dresden-Rossendorf (HZDR) for the provision of synchrotron radiation facilities under proposal number A20-1-907. This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Heavy Elements Chemistry Program under award number DE-SC0023693. C.S. acknowledges funding from the BMBF (Federal Ministry of Education and Research) with ErUM Pro grant 05K22PE2.

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.6c06234.

  • Images of products; synthesis yields; thermal ellipsoid plots; powder X-ray diffraction patterns; crystallographic data; ambient pressure UV-vis-NIR, and Raman spectra; UV-vis-NIR spectra after the release of pressure; high-pressure Raman spectra across the entire spectral range; peak assignments for Raman spectra; high pressure; and HERFD-XANES peak positions (PDF)

The manuscript was written through the contributions of all authors. All authors have given approval to the final version of the manuscript.

U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Heavy Elements Chemistry Program, under Award Number DE-SC0023693. C.S. acknowledges funding from the BMBF (Federal Ministry of Education and Research) with ErUM Pro grant 05K22PE2.

The authors declare no competing financial interest.

References

  1. Gompa T. P., Ramanathan A., Rice N. T., La Pierre H. S.. The Chemical and Physical Properties of Tetravalent Lanthanides: Pr, Nd, Tb, and Dy. Dalton Trans. 2020;49(45):15945–15987. doi: 10.1039/D0DT01400A. [DOI] [PubMed] [Google Scholar]
  2. Wineinger H. B., Sperling J. M., Albrecht T. E.. Molecular Complexes of Low-Valent f-Elements from Lanthanum to Californium. Coord. Chem. Rev. 2025;545:217004. doi: 10.1016/j.ccr.2025.217004. [DOI] [Google Scholar]
  3. Bousrez G., Jaroschik F.. Organic Synthesis with Elemental Lanthanides – Going Beyond Samarium and Ytterbium. Eur. J. Org. Chem. 2022;2022(18):e202200202. doi: 10.1002/ejoc.202200202. [DOI] [Google Scholar]
  4. Du Z., Li W., Zhu X., Xu F., Shen Q.. Divalent Lanthanide Complexes: Highly Active Precatalysts for the Addition of N–H and C–H Bonds to Carbodiimides. J. Org. Chem. 2008;73(22):8966–8972. doi: 10.1021/jo801693z. [DOI] [PubMed] [Google Scholar]
  5. Bochkarev M. N.. Molecular Compounds of “New” Divalent Lanthanides. Coord. Chem. Rev. 2004;248(9):835–851. doi: 10.1016/j.ccr.2004.04.004. [DOI] [Google Scholar]
  6. Rice N. T., Popov I. A., Russo D. R., Bacsa J., Batista E. R., Yang P., Telser J., La Pierre H. S.. Design, Isolation, and Spectroscopic Analysis of a Tetravalent Terbium Complex. J. Am. Chem. Soc. 2019;141(33):13222–13233. doi: 10.1021/jacs.9b06622. [DOI] [PubMed] [Google Scholar]
  7. Rice N. T., Popov I. A., Russo D. R., Gompa T. P., Ramanathan A., Bacsa J., Batista E. R., Yang P., La Pierre H. S.. Comparison of Tetravalent Cerium and Terbium Ions in a Conserved, Homoleptic Imidophosphorane Ligand Field. Chem. Sci. 2020;11(24):6149–6159. doi: 10.1039/D0SC01414A. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Palumbo C. T., Zivkovic I., Scopelliti R., Mazzanti M.. Molecular Complex of Tb in the + 4 Oxidation State. J. Am. Chem. Soc. 2019;141(25):9827–9831. doi: 10.1021/jacs.9b05337. [DOI] [PubMed] [Google Scholar]
  9. Willauer A. R., Palumbo C. T., Fadaei-Tirani F., Zivkovic I., Douair I., Maron L., Mazzanti M.. Accessing the + IV Oxidation State in Molecular Complexes of Praseodymium. J. Am. Chem. Soc. 2020;142(12):5538–5542. doi: 10.1021/jacs.0c01204. [DOI] [PubMed] [Google Scholar]
  10. Willauer A. R., Douair I., Chauvin A.-S., Fadaei-Tirani F., Bünzli J.-C. G., Maron L., Mazzanti M.. Structure Reactivity and Luminescence Studies of Triphenylsiloxide Complexes of Tetravalent Lanthanides. Chem. Sci. 2022;13(3):681–691. doi: 10.1039/D1SC05517H. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Willauer A. R., Palumbo C. T., Scopelliti R., Zivkovic I., Douair I., Maron L., Mazzanti M.. Stabilization of the Oxidation State + IV in Siloxide-Supported Terbium Compounds. Angew. Chem., Int. Ed. 2020;59(9):3549–3553. doi: 10.1002/anie.201914733. [DOI] [PubMed] [Google Scholar]
  12. Pearson R. G.. Hard and Soft Acids and Bases. J. Am. Chem. Soc. 1963;85(22):3533–3539. doi: 10.1021/ja00905a001. [DOI] [Google Scholar]
  13. Mushnikov N., Goto V., Kolomiets T., Yoshimura K., Zhang W., Kageyama H.. Alloying and Pressure Effect on the Mixed-Valence State of Yb in YbInCu4 . J. Phys.: Condens. Matter. 2004;16(13):2395–2406. doi: 10.1088/0953-8984/16/13/018. [DOI] [Google Scholar]
  14. Schöppner M., Moser J., Kratzer A., Potzel U., Mignot J. M., Kalvius G. M.. Changes of Valence State of Yb in YbCuAl at High Pressure: A Mössbauer Study. Z. Für Phys. B Condens. Matter. 1986;63:25–32. doi: 10.1007/BF01312574. [DOI] [Google Scholar]
  15. Jayaraman A., Narayanamurti V., Bucher E., Maines R. G.. Continuous and Discontinuous Semiconductor-Metal Transition in Samarium Monochalcogenides Under Pressure. Phys. Rev. Lett. 1970;25(20):1430–1433. doi: 10.1103/PhysRevLett.25.1430. [DOI] [Google Scholar]
  16. Dallera C., Annese E., Rueff J.-P., Palenzona A., Vankó G., Braicovich L., Shukla A., Grioni M.. Determination of Pressure-Induced Valence Changes in YbAl2 by Resonant Inelastic X-Ray Emission. Phys. Rev. B. 2003;68(24):245114. doi: 10.1103/PhysRevB.68.245114. [DOI] [Google Scholar]
  17. Tsiok O. B., Khvostantsev L. G., Golubkov A. V., Smirnov I. A., Brazhkin V. V.. General Behavior of Chalcogenides of Rare-Earth Metals in Transition to the Intermediate Valence State under High Pressures. Phys. Rev. B. 2014;90(16):165141. doi: 10.1103/PhysRevB.90.165141. [DOI] [Google Scholar]
  18. Petit L., Svane A., Lüders M., Szotek Z., Vaitheeswaran G., Kanchana V., Temmerman W. M.. Phase Transitions in Rare Earth Tellurides under Pressure. J. Phys.: condens. Matter. 2014;26(27):274213. doi: 10.1088/0953-8984/26/27/274213. [DOI] [PubMed] [Google Scholar]
  19. Wada H., Hundley M. F., Movshovich R., Thompson J. D.. Pressure Effect on the Valence Transition of EuNi2(Ge1‑xSix)2 . Phys. Rev. B. 1999;59(2):1141–1144. doi: 10.1103/PhysRevB.59.1141. [DOI] [Google Scholar]
  20. Kumar R. S., Zhang Y., Thamizhavel A., Svane A., Vaitheeswaran G., Kanchana V., Xiao Y., Chow P., Chen C., Zhao Y.. Pressure Induced Valence Change of Eu in EuFe2As2 at Low Temperature and High Pressures Probed by Resonant Inelastic X-Ray Scattering. Appl. Phys. Lett. 2014;104(4):042601. doi: 10.1063/1.4863203. [DOI] [Google Scholar]
  21. Temmerman W. M., Svane A., Petit L., Lüders M., Strange P., Szotek Z.. Pressure Induced Valence Transitions in f-Electron Systems. Phase Transitions. 2007;80(4–5):415–443. doi: 10.1080/01411590701228703. [DOI] [Google Scholar]
  22. Kumar R. S., Svane A., Vaitheeswaran G., Kanchana V., Bauer E. D., Hu M., Nicol M. F., Cornelius A. L.. Pressure-Induced Valence Change in YbAl3: A Combined High-Pressure Inelastic X-Ray Scattering and Theoretical Investigation. Phys. Rev. B. 2008;78(7):075117. doi: 10.1103/PhysRevB.78.075117. [DOI] [Google Scholar]
  23. Matsubayashi K., Kawamura N., Mizumaki M., Ishimatsu N.. Pressure-Induced Valence Change toward the QCP in 4f-Electron Compounds Determined by X-Ray Absorption Spectroscopy. High. Press. Res. 2016;36(3):419–428. doi: 10.1080/08957959.2016.1199695. [DOI] [Google Scholar]
  24. Mitsuda A., Hamano S., Araoka N., Yayama H., Wada H.. Pressure-Induced Valence Transition in Antiferromagnet EuRh2Si2 . J. Phys. Soc. Jpn. 2012;81(2):023709. doi: 10.1143/JPSJ.81.023709. [DOI] [Google Scholar]
  25. Jayaraman A., Singh A. K., Chatterjee A., Devi S. U.. Pressure-Volume Relationship and Pressure-Induced Electronic and Structural Transformations in Eu and Yb Monochalcogenides. Phys. Rev. B. 1974;9(6):2513–2520. doi: 10.1103/PhysRevB.9.2513. [DOI] [Google Scholar]
  26. Huyan S., Ryan D. H., Slade T. J., Lavina B., Jose G., Wang H., Wilde J. M., Ribeiro R. A., Zhao J., Xie W., Bi W., Alp E. E., Bud’ko S. L., Canfield P. C.. Strong Enhancement of Magnetic Ordering Temperature and Structural/Valence Transitions in EuPd3S4 under High Pressure. Proc. Natl. Acad. Sci. U. S. A. 2023;120(52):e2310779120. doi: 10.1073/pnas.2310779120. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Jayaraman A., Dernier P., Longinotti L. D.. Study of the Valence Transition in SmS Induced by Alloying, Temperature, and Pressure. Phys. Rev. B. 1975;11(8):2783–2794. doi: 10.1103/PhysRevB.11.2783. [DOI] [Google Scholar]
  28. Dionicio G., Wilhelm H., Hossain Z., Geibel C.. Temperature- and Pressure-Induced Valence Transition in EuCo2Ge2 . Phys. B Condens. Matter. 2006;378–380:724–725. doi: 10.1016/j.physb.2006.01.258. [DOI] [Google Scholar]
  29. Fuse A., Nakamoto G., Kurisu M., Ishimatsu N., Tanida H.. The Valence State of Yb Metal under High Pressure Determined by XANES Measurement up to 34.6 GPa. J. Alloys Compd. 2004;376(1):34–37. doi: 10.1016/j.jallcom.2003.12.035. [DOI] [Google Scholar]
  30. Jayaraman A.. Valence Changes at High Pressure in Systems Containing Lanthanoids. Angew. Chem., Int. Ed. 1980;19(8):587–593. doi: 10.1002/anie.198005871. [DOI] [Google Scholar]
  31. Wu M., Zheng L., Chu S., Qin Z., Chen X.-J., Lin C., Tang Z., Hu T.. Pressure-Induced Valence Change and Semiconductor–Metal Transition in PbCrO3 . J. Phys. Chem. C. 2014;118(40):23274–23278. doi: 10.1021/jp5072346. [DOI] [Google Scholar]
  32. Vedel I., Oki K., Redon A. M., Leger J. M.. Electronic Transitions Induced by Pressure in Cerium Monochalcogenides and Monopnictides. Phys. BC. 1986;139–140:361–363. doi: 10.1016/0378-4363(86)90599-1. [DOI] [Google Scholar]
  33. Holmes A. T., Jaccard D., Miyake K.. Signatures of Valence Fluctuations in CeCu2Si2 under High Pressure. Phys. Rev. B. 2004;69(2):024508. doi: 10.1103/PhysRevB.69.024508. [DOI] [Google Scholar]
  34. Rueff J.-P., Raymond S., Taguchi M., Sikora M., Itié J.-P., Baudelet F., Braithwaite D., Knebel G., Jaccard D.. Pressure-Induced Valence Crossover in Superconducting CeCu2Si2 . Phys. Rev. Lett. 2011;106(18):186405. doi: 10.1103/PhysRevLett.106.186405. [DOI] [PubMed] [Google Scholar]
  35. Wu X., Steinle-Neumann G., Narygina O., Kantor I., McCammon C., Pascarelli S., Aquilanti G., Prakapenka V., Dubrovinsky L.. Iron Oxidation State of FeTiO3 under High Pressure. Phys. Rev. B. 2009;79(9):094106. doi: 10.1103/PhysRevB.79.094106. [DOI] [PubMed] [Google Scholar]
  36. Azuma M., Carlsson S., Rodgers J., Tucker M. G., Tsujimoto M., Ishiwata S., Isoda S., Shimakawa Y., Takano M., Attfield J. P.. Pressure-Induced Intermetallic Valence Transition in BiNiO3 . J. Am. Chem. Soc. 2007;129(46):14433–14436. doi: 10.1021/ja074880u. [DOI] [PubMed] [Google Scholar]
  37. Jayaraman A., Kourouklis G. A., Van Uitert L. G.. Pressure-Induced Structural Transitions and Valence Change in TlReO4: A High-Pressure Raman Study. Phys. Rev. B. 1987;36(16):8547–8551. doi: 10.1103/PhysRevB.36.8547. [DOI] [PubMed] [Google Scholar]
  38. Xu W. M., Rozenberg G. K., Pasternak M. P., Kertzer M., Kurnosov A., Dubrovinsky L. S., Pascarelli S., Munoz M., Vaccari M., Hanfland M., Jeanloz R.. Pressure-Induced Fe→Cu Cationic Valence Exchange and Its Structural Consequences: High-Pressure Studies of Delafossite CuFeO2 . Phys. Rev. B. 2010;81(10):104110. doi: 10.1103/PhysRevB.81.104110. [DOI] [Google Scholar]
  39. García Baonza V., Lobato Á., Recio J. M., Taravillo M.. Charge Analysis in (RE)­CrO4 Scheelites by Combined Raman Spectroscopy and Computer Simulations. J. Solid State Chem. 2022;316:123624. doi: 10.1016/j.jssc.2022.123624. [DOI] [Google Scholar]
  40. Siidra O. I., Nazarchuk E. V., Kayukov R. A., Bubnova R. S., Krivovichev S. V.. CrVI→CrV Transition in Uranyl Chromium Compounds: Synthesis and High-Temperature X-Ray Diffraction Study of Cs2[(UO2)2(CrO4)3] Z. Für Anorg. Allg. Chem. 2013;639(12–13):2302–2306. doi: 10.1002/zaac.201300219. [DOI] [Google Scholar]
  41. Galley S. S., Arico A. A., Lee T.-H., Deng X., Yao Y.-X., Sperling J. M., Proust V., Storbeck J. S., Dobrosavljevic V., Neu J. N., Siegrist T., Baumbach R. E., Albrecht-Schmitt T. E., Kaltsoyannis N., Lanatà N.. Uncovering the Origin of Divergence in the CsM­(CrO4)2 (M = La, Pr, Nd, Sm, Eu; Am) Family through Examination of the Chemical Bonding in a Molecular Cluster and by Band Structure Analysis. J. Am. Chem. Soc. 2018;140(5):1674–1685. doi: 10.1021/jacs.7b09474. [DOI] [PubMed] [Google Scholar]
  42. Sheldrick G. M.. Crystal Structure Refinement with SHELXL. Acta Crystallogr., Sect. C: Struct. Chem. 2015;71(1):3–8. doi: 10.1107/S2053229614024218. [DOI] [PMC free article] [PubMed] [Google Scholar]
  43. Dolomanov O. V., Bourhis L. J., Gildea R. J., Howard J. A. K., Puschmann H.. OLEX2: A Complete Structure Solution, Refinement and Analysis Program. J. Appl. Crystallogr. 2009;42(2):339–341. doi: 10.1107/S0021889808042726. [DOI] [Google Scholar]
  44. Sheldrick G. M.. SHELXT – Integrated Space-Group and Crystal-Structure Determination. Acta Crystallogr. Sect. Found. Adv. 2015;71(1):3–8. doi: 10.1107/S2053273314026370. [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Scheinost A. C., Claussner J., Exner J., Feig M., Findeisen S., Hennig C., Kvashnina K. O., Naudet D., Prieur D., Rossberg A., Schmidt M., Qiu C., Colomp P., Cohen C., Dettona E., Dyadkin V., Stumpf T.. ROBL-II at ESRF: A Synchrotron Toolbox for Actinide Research. J. Synchrotron Radiat. 2021;28(1):333–349. doi: 10.1107/S1600577520014265. [DOI] [PMC free article] [PubMed] [Google Scholar]
  46. Kvashnina K. O., Scheinost A. C.. A Johann-Type X-Ray Emission Spectrometer at the Rossendorf Beamline. J. Synchrotron Radiat. 2016;23(3):836–841. doi: 10.1107/S1600577516004483. [DOI] [PubMed] [Google Scholar]
  47. Piermarini G. J., Block S., Barnett J. D., Forman R. A.. Calibration of the Pressure Dependence of the R1 Ruby Fluorescence Line to 195 Kbar. J. Appl. Phys. 1975;46:2774–2780. doi: 10.1063/1.321957. [DOI] [Google Scholar]
  48. Mao H. K., Xu J., Bell P. M.. Calibration of the Ruby Pressure Gauge to 800 Kbar under Quasi-Hydrostatic Conditions. J. Geophys Res. Solid Earth. 1986;91(B5):4673–4676. doi: 10.1029/JB091iB05p04673. [DOI] [Google Scholar]
  49. Dewaele A., Torrent M., Loubeyre P., Mezouar M.. Compression Curves of Transition Metals in the Mbar Range: Experiments and Projector Augmented-Wave Calculations. Phys. Rev. B. 2008;78(10):104102. doi: 10.1103/PhysRevB.78.104102. [DOI] [Google Scholar]
  50. Chijioke A. D., Nellis W. J., Soldatov A., Silvera I. F.. The Ruby Pressure Standard to 150 GPa. J. Appl. Phys. 2005;98:114905. doi: 10.1063/1.2135877. [DOI] [Google Scholar]
  51. Petitgirard S., Jacobs J., Cerantola V., Collings I. E., Tucoulou R., Dubrovinsky L., Sahle C. J.. A Versatile Diamond Anvil Cell for X-Ray Inelastic, Diffraction and Imaging Studies at Synchrotron Facilities. Rev. Sci. Instrum. 2019;90(9):095107. doi: 10.1063/1.5119025. [DOI] [PubMed] [Google Scholar]
  52. Melnikov P., Parada C., Bueno I., Morán E.. On Rubidium Lanthanide Double Chromates. J. Alloys Compd. 1993;190(2):265–267. doi: 10.1016/0925-8388(93)90409-G. [DOI] [Google Scholar]
  53. Aroyo M. I., Perez-Mato J. M., Capillas C., Kroumova E., Ivantchev S., Madariaga G., Kirov A., Wondratschek H.. Bilbao Crystallographic Server: I. Databases and Crystallographic Computing Programs. Z. Für Krist. - Cryst. Mater. 2006;221(1):15–27. doi: 10.1524/zkri.2006.221.1.15. [DOI] [Google Scholar]
  54. Sperling J. M., Beck N., Scheibe B., Bai Z., Brannon J., Gomez-Martinez D., Grödler D. A., Johnson J., Lin X., Rotermund B. M., Albrecht-Schönzart E. T.. Synthesis, Characterization, and High-Pressure Studies of a 3D Berkelium­(III) Carboxylate Framework Material. Chem. Commun. 2022;58(13):2200–2203. doi: 10.1039/D1CC06958F. [DOI] [PubMed] [Google Scholar]
  55. Sperling J. M., Warzecha E., Klamm B. E., Gaiser A. N., Windorff C. J., Whitefoot M. A., Albrecht-Schönzart T. E.. Pronounced Pressure Dependence of Electronic Transitions for Americium Compared to Isomorphous Neodymium and Samarium Mellitates. Inorg. Chem. 2021;60(1):476–483. doi: 10.1021/acs.inorgchem.0c03293. [DOI] [PubMed] [Google Scholar]
  56. Bai Z., Beck N. B., Scheibe B., Sperling J. M., Weiland A., Ruf M., Brannon J. P., Rotermund B. M., Gomez Martinez D., Albrecht-Schönzart T. E.. Investigation of Pressure Effects in the Bimetallic Transplutonium Tetrazolate Complexes [(An­(pmtz)2(H2O)3)2(μ-pmtz)]2(pmtz)2·nH2O (An3+ = Cm3+, Bk3+, and Cf3+) J. Am. Chem. Soc. 2024;146(11):7822–7830. doi: 10.1021/jacs.4c00803. [DOI] [PubMed] [Google Scholar]
  57. Sperling J. M., Warzecha E. J., Celis-Barros C., Sergentu D.-C., Wang X., Klamm B. E., Windorff C. J., Gaiser A. N., White F. D., Beery D. A., Chemey A. T., Whitefoot M. A., Long B. N., Hanson K., Kögerler P., Speldrich M., Zurek E., Autschbach J., Albrecht-Schönzart T. E.. Compression of Curium Pyrrolidine-Dithiocarbamate Enhances Covalency. Nature. 2020;583(7816):396–399. doi: 10.1038/s41586-020-2479-2. [DOI] [PubMed] [Google Scholar]
  58. Binnemans K., Görller-Walrand C.. On the Color of the Trivalent Lanthanide Ions. Chem. Phys. Lett. 1995;235(3):163–174. doi: 10.1016/0009-2614(95)00126-O. [DOI] [Google Scholar]
  59. Gomez Martinez D., Sperling J. M., Beck N. B., Wineinger H. B., Brannon J. P., Whitefoot M. A., Horne G. P., Albrecht-Schönzart T. E.. Comparison of Americium­(III) and Neodymium­(III) Monothiophosphate Complexes. Inorg. Chem. 2024;63(20):9237–9244. doi: 10.1021/acs.inorgchem.4c00869. [DOI] [PubMed] [Google Scholar]
  60. Sperling J. M., Warzecha E., Windorff C. J., Klamm B. E., Gaiser A. N., Whitefoot M. A., White F. D., Poe T. N., Albrecht-Schönzart T. E.. Pressure-Induced Spectroscopic Changes in a Californium 1D Material Are Twice as Large as Found in the Holmium Analog. Inorg. Chem. 2020;59(15):10794–10801. doi: 10.1021/acs.inorgchem.0c01290. [DOI] [PubMed] [Google Scholar]
  61. Saji T., Aoyagui S.. Polarographic Studies on Bipyridines Complexes: II. Correlation between Charge-Transfer Frequencies and Oxidation Potentials of Tris (2,2′-Bipyridine) Complexes of Iron, Ruthenium, Osmium, Cobalt and Chromium. J. Electroanal. Chem. Interfacial Electrochem. 1975;60(1):1–10. doi: 10.1016/S0022-0728(75)80196-3. [DOI] [Google Scholar]
  62. Peover M. E.. Correlations between Optical and Electrode Charge-Transfer Processes in Organic Systems. Electrochim. Acta. 1968;13(5):1083–1094. doi: 10.1016/0013-4686(68)80037-4. [DOI] [Google Scholar]
  63. Varga L. P., Asprey L. B.. Free Ion 4f n Levels of the Tetravalent Lanthanides. Fluorescence and Absorption Spectra of Cesium Dysprosium (IV) Heptafluoride. J. Chem. Phys. 1968;48(1):139–146. doi: 10.1063/1.1664459. [DOI] [Google Scholar]
  64. Han D., Uda T., Nose Y., Okajima T., Murata H., Tanaka I., Shinoda K.. Tetravalent Dysprosium in a Perovskite-Type Oxide. Adv. Mater. 2012;24(15):2051–2053. doi: 10.1002/adma.201200127. [DOI] [PubMed] [Google Scholar]
  65. Hoppe R.. Recent Progress in Oxo- and Fluorometalate Chemistry. Angew. Chem., Int. Ed. 1981;20(1):63–87. doi: 10.1002/anie.198100631. [DOI] [Google Scholar]
  66. Hu Z., Kaindl G., Vandré D., Hoppe R., Wortmann G.. X-Ray Absorption Study of Tetravalent Dy Compounds: Cs2RbDyF7 and Cs2KDyF7 . J. Alloys Compd. 1994;205(1):263–269. doi: 10.1016/0925-8388(94)90799-4. [DOI] [Google Scholar]
  67. Yuan H., Rodriguez-Hernandez P., Muñoz A., Errandonea D.. Putting the Squeeze on Lead Chromate Nanorods. J. Phys. Chem. Lett. 2019;10(16):4744–4751. doi: 10.1021/acs.jpclett.9b01978. [DOI] [PubMed] [Google Scholar]
  68. Goncharov A. F.. Raman Spectroscopy at High Pressures. Int. J. Spectrosc. 2012;2012(1):1–16. doi: 10.1155/2012/617528. [DOI] [Google Scholar]
  69. Bandiello E., Errandonea D., Martinez-Garcia D., Santamaria-Perez D., Manjón F. J.. Effects of High-Pressure on the Structural, Vibrational, and Electronic Properties of Monazite-Type PbCrO4 . Phys. Rev. B. 2012;85(2):024108. doi: 10.1103/PhysRevB.85.024108. [DOI] [Google Scholar]
  70. Baran E. J., Ferrer E. G., Bueno I., Parada C.. Vibrational Spectra of Some Double Chromates of the Type LnK­(CrO4)2 . J. Raman Spectrosc. 1990;21(1):27–30. doi: 10.1002/jrs.1250210106. [DOI] [Google Scholar]
  71. Ughade S., Poddar P.. A Systematic Study of Rare-Earth Ions Size-Dependent Structural Phase Transition from Monazite to Zircon-Type in Rare Earth Chromates Using Raman Spectroscopy. J. Raman Spectrosc. 2023;54(7):793–801. doi: 10.1002/jrs.6542. [DOI] [Google Scholar]
  72. Viola M. D. C., Sangra A. M., Pedregosa J. C.. Vibrational Spectroscopic Characterization of Lanthanide Molybdates. J. Mater. Sci. 1993;28(24):6587–6590. doi: 10.1007/BF00356399. [DOI] [Google Scholar]
  73. Popov V. V., Menushenkov A. P., Yastrebtsev A. A., Dubyago F. E., Rudakov S. G., Svetogorov R. D., Ognevskaya N. V., Tsarenko N. A., Seregina N., Shchetinin I. V., Ponkratov K. V.. Influence of the Lanthanide on the Composition and Structure of Hydrated Ln Chromates. J. Phys.: Conf. Ser. 2021;2036(1):012022. doi: 10.1088/1742-6596/2036/1/012022. [DOI] [Google Scholar]
  74. Bueno I., Garcia O., Parada C., Puche R. S.. Crystal Growth, IR and Raman Spectra, Thermal Decomposition and Magnetic Properties of KLn­(CrO4)2 (Ln – Pr, Nd, Sm) J. Common Met. 1988;139(2):261–271. doi: 10.1016/0022-5088(88)90007-0. [DOI] [Google Scholar]
  75. Panchal V., Errandonea D., Manjón F. J., Muñoz A., Rodríguez-Hernández P., Achary S. N., Tyagi A. K.. High-Pressure Lattice-Dynamics of NdVO4 . J. Phys. Chem. Solids. 2017;100:126–133. doi: 10.1016/j.jpcs.2016.10.001. [DOI] [Google Scholar]
  76. Huang Y., Butler I. S.. High-Pressure Micro-Raman Spectra of Potassium Chromate­(VI) and Potassium Tungstate­(VI) Appl. Spectrosc. 1990;44(8):1326–1328. doi: 10.1366/000370290789619513. [DOI] [Google Scholar]
  77. Löble M. W., Keith J. M., Altman A. B., Stieber S. C. E., Batista E. R., Boland K. S., Conradson S. D., Clark D. L., Lezama Pacheco J., Kozimor S. A., Martin R. L., Minasian S. G., Olson A. C., Scott B. L., Shuh D. K., Tyliszczak T., Wilkerson M. P., Zehnder R. A.. Covalency in Lanthanides. An X-Ray Absorption Spectroscopy and Density Functional Theory Study of LnCl6 x– (x = 3, 2) J. Am. Chem. Soc. 2015;137(7):2506–2523. doi: 10.1021/ja510067v. [DOI] [PubMed] [Google Scholar]
  78. Bianconi A, Marcelli A, Dexpert H, Karnatak R, Kotani A, Jo T, Petiau J.. Specific Intermediate-Valence State of Insulating 4f Compounds Detected by L 3 X-Ray Absorption. Phys. Rev. B. 1987;35(2):806–812. doi: 10.1103/PhysRevB.35.806. [DOI] [PubMed] [Google Scholar]
  79. Hu Z.. Valency and 4f Covalency of Cs2RbTbF7 . Phys. Rev. B. 1995;51(12):7514–7520. doi: 10.1103/PhysRevB.51.7514. [DOI] [PubMed] [Google Scholar]
  80. Hu Z., Kaindl G., Müller B. G.. Core-Level Spectroscopy of the Tetravalent Lanthanide Compounds M3LnF7 (with M = Cs, Rb; Ln = Ce, Pr, Nd, Tb, Dy) J. Alloys Compd. 1997;246(1):177–185. doi: 10.1016/S0925-8388(96)02474-7. [DOI] [Google Scholar]
  81. Minasian S. G., Batista E. R., Booth C. H., Clark D. L., Keith J. M., Kozimor S. A., Lukens W. W., Martin R. L., Shuh D. K., Stieber S. C. E., Tylisczcak T., Wen X.. Quantitative Evidence for Lanthanide-Oxygen Orbital Mixing in CeO2, PrO2, and TbO2 . J. Am. Chem. Soc. 2017;139(49):18052–18064. doi: 10.1021/jacs.7b10361. [DOI] [PubMed] [Google Scholar]
  82. Roßberg A., Reich T., Bernhard G.. Complexation of Uranium­(VI) with Protocatechuic AcidApplication of Iterative Transformation Factor Analysis to EXAFS Spectroscopy. Anal. Bioanal. Chem. 2003;376(5):631–638. doi: 10.1007/s00216-003-1963-5. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

ja6c06234_si_001.pdf (817.8KB, pdf)

Articles from Journal of the American Chemical Society are provided here courtesy of American Chemical Society

RESOURCES