Pulse radiolysis studies of mangiferin: A C-glycosyl xanthone isolated from Mangifera indica

Pulse radiolysis technique has been employed to study the reaction of different oxidizing and reducing radicals with mangiferin. The reaction of OH radical showed the formation of transient species absorbing in 380–390 and 470–480 nm region. The reaction with specific one-electron oxidants (N₃, CCl₃O₂) also showed the formation of similar transient absorption bands and is assigned to phenoxyl radicals. The pK_a values of the transient species have been determined to be 6.3 and 11.9. One-electron oxidation potential of mangiferin at pH 9 has been found to be 0.62 V vs. NHE. The reaction of e_aq⁻ showed the formation of transient species with λ_max at 340 nm, which is assigned to the ketyl anion radical formed on addition of e_aq⁻ at carbonyl site. Reactions of one-electron oxidised mangiferin radicals with ascorbic acid have also been studied.     

Concentration dependent Raman study of 1,4-diethynylbenzene on gold nanoparticle surfaces

Concentration dependent adsorption behaviors of 1,4-diethynylbenzene (DEB) on gold nanoparticle surfaces have been investigated by means of surface-enhanced Raman scattering (SERS). The spectral features including the multiple peaks in the ν(CC)_bound stretching region were found to vary as the bulk concentration of DEB in gold nanoparticles. At a low concentration of 10⁻⁶ M, only the multiple ν(CC)_bound band was conspicuous at ∼2000 cm⁻¹ and the free CC stretching band was barely detected in the SERS spectra. When the bulk concentration was increased, the ν(CC)_free band became prominent at ∼2104 cm⁻¹. These splitting bands may provide the evidence that DEB is adsorbed on gold mainly through one of the two acetylene groups with the other CC groups being pendent with respect to the gold surface. Ab initio density functional theory (DFT) calculations of DEB were performed to check the vibrational assignment.     

Raman spectroscopy investigation of mono- and diacyl-polyoxyethylene glycols

Physical and thermal properties of polyoxyethylene glycol glycerides (Gelucire 50/13) used as sustained release matrix forming agent in pharmaceutical applications are studied by Raman spectroscopy combined with X-ray diffraction and differential scanning calorimetry methods.At first, Raman spectroscopy was used to characterize the polymorphs and liquid state of PEG 1500, with emphasis placed on the evolution of the Raman-active CC and CO stretching region (1300–1100 cm⁻¹), along with complementary analysis of the Raman-active CH stretching modes (3000–2800 cm⁻¹) in comparison with temperature. Unique Raman signatures were obtained for all phases, with their identity confirmed using DSC and XRD. The CC and CO stretching modes, which provided insight into the trans/gauche content, permitted polymorph discrimination due to differences in the number of modes, their relative frequencies and their full-widths at half-maximum. CH stretching generally increased with polymorph stability, indicating the dominance of methylene antisymmetric CH₂ vibrations as the PEG 1500 crystal lattice became more ordered. The change in the intensities of the CH stretching bands was used to probe the order–disorder transition.The second time, Raman spectroscopy of Gelucire 50/13 was performed to characterize the contribution of its each component, with emphasis placed on the evolution of the t(CH₂) and ν(CC) vibrational mode regions (1300–1200 cm⁻¹), along with analysis of the Raman-active CH stretching modes (3000–2800 cm⁻¹), δ(CH₂) and δ(CH₃) deformation region (1500–1400 cm⁻¹), and r_as(CH₂) rocking region (900–800 cm⁻¹). In comparison with temperature, the changes of the ratios of I[ν_s(CH₂)]/I[ν_as(CH₂)] (I₂₈₅₀/I₂₈₉₀), I[ν_as(CH₂)]/I[ν_s(CH₃)] (I₂₈₉₀/I₂₉₅₀), I[δ(CH₂)]/I[δ(CH₃)] (I₁₄₄₄/I₁₄₉₀), I₁₂₉₆/I₁₂₈₂ and I[r_as(CH₂)]/I[t(CH₂)] (I₈₄₅/I₁₂₈₂) were directly correlated with conformational changes of the Gelucire structure. Overall, Raman spectroscopy clearly demonstrated that the different functional groups studied could be characterized independently, allowing for the understanding of their role in Gelucire polymorphism.     

High-resolution infrared analysis of seven fundamental bands of gaseous isothiazole between 750 and 1500 cm−1

The gas phase IR spectrum of isothiazole, C₃H₃NS, between 550 and 1700 cm⁻¹ was recorded with a resolution of ca. 0.003 cm⁻¹. The rotational structure of seven fundamental bands in the region 750–1500 cm⁻¹ has been assigned and analysed by the Watson Hamiltonian model. A number of local resonances in the bands have been identified and explained qualitatively in terms of Coriolis interactions. For each band upper state spectroscopic constants, including band center, rotational constants, and quartic centrifugal distortion constants are given. From observed crossings due to resonances we locate the weak bands ν₉(A′) and ν₁₃(A′) at 1041.9(2) and 642.0(3) cm⁻¹, respectively. The anharmonic frequencies have been determined using a cc-pVTZ basis set, at the MP2 and B3LYP levels; the two theoretical methods give very similar results for rotational constants, anharmonic band center frequencies and distortion constants, and many of these are in good agreement with experiment.     

Vibrational spectroscopy of lapachol, α- and β-lapachone: Theoretical and experimental elucidation of the Raman and infrared spectra

Raman and infrared spectroscopy were applied for the vibrational characterization of lapachol and its pyran derivatives, α-lapachone and β-lapachone. Experimental spectra of solid state samples were acquired between 4000 and 100 cm⁻¹ in Raman experiments, and between 4000 and 600 cm⁻¹ (mid-infrared) and 600–100 cm⁻¹ (far-infrared) with FTIR spectroscopy, respectively. Full structure optimization and theoretical vibrational wavenumbers were calculated at the B3LYP/6-31 + + G(d,p) level. Detailed assignments of vibrational modes in an experimental and theoretical spectra were based on potential energy distribution analyses, using Veda 4.1 software. Clear differentiation between the three compounds was verified in the region between 1725 and 1525 cm⁻¹, in which the ν(CO) and ν(CC) modes of the quinone moiety were assigned.     

Radical Localization in a Series of Symmetric NiII Complexes with Oxidized Salen Ligands

Square‐planar nickel(II) complexes of salen ligands, N,N′‐bis(3‐tert‐butyl‐(5R)‐salicylidene)‐1,2‐cyclohexanediamine), in which R=tert‐butyl ( 1 ), OMe ( 2 ), and NMe₂ ( 3 ), were prepared and the electronic structure of the one‐electron‐oxidized species [ 1 – 3 ]^+. was investigated in solution. Cyclic voltammograms of [ 1 – 3 ] showed two quasi‐reversible redox waves that were assigned to the oxidation of the phenolate moieties to phenoxyl radicals. From the difference between the first and second redox potentials, the trend of electronic delocalization 1 ^+.> 2 ^+.> 3 ^+. was obtained. The cations [ 1 – 3 ]^+. exhibited isotropic g tensors of 2.045, 2.023, and 2.005, respectively, reflecting a lower metal character of the singly occupied molecular orbital (SOMO) for systems that involve strongly electron‐donating substituents. Pulsed‐EPR spectroscopy showed a single population of equivalent imino nitrogen atoms for 1 ^+., whereas two distinct populations were observed for 2 ^+.. The resonance Raman spectra of 2 ^+. and 3 ^+. displayed the ν_8a band of the phenoxyl radicals at 1612 cm^?1, as well as the ν_8a bands of the phenolates. In contrast, the Raman spectrum of 1 ^+. exhibited the ν_8a band at 1602 cm^?1, without any evidence of the phenolate peak. Previous work showed an intense near‐infrared (NIR) electronic transition for 1 ^+. (Δν_1/2=660 cm^?1, ε=21 700 M ^?1 cm^?1), indicating that the electron hole is fully delocalized over the ligand. The broader and moderately intense NIR transition of 2 ^+. (Δν_1/2=1250 cm^?1, ε=12 800 M ^?1 cm^?1) suggests a certain degree of ligand‐radical localization, whereas the very broad NIR transition of 3 ^+. (Δν_1/2=8630 cm^?1, ε=2550 M ^?1 cm^?1) indicates significant localization of the ligand radical on a single ring. Therefore, 1 ^+. is a Class III mixed‐valence complex, 2 ^+. is Class II/III borderline complex, and 3 ^+. is a Class II complex according to the Robin–Day classification method. By employing the Coulomb‐attenuated method (CAM‐B3LYP) we were able to predict the electron‐hole localization and NIR transitions in the series, and show that the energy match between the redox‐active ligand and the metal d orbitals is crucial for delocalization of the radical SOMO.     

Fourier transform and high sensitivity cw-cavity ringdown absorption spectroscopies of ozone in the 6030–6130 cm−1 region. First observation and analysis of the 3ν1+3ν3 and 2ν2+5ν3 bands

The absorption spectrum of ¹⁶O₃ has been recorded between 6030 and 6130 cm⁻¹ by Fourier Transform Spectroscopy (GSMA, Reims) and cw-cavity ringdown spectroscopy (LSP, Grenoble). The two new bands 3ν₁+3ν₃ and 2ν₂+5ν₃ centered at 6063.923 and 6124.304 cm⁻¹, respectively are observed and analyzed. Rovibrational transitions with J and K_a values up to 40 and 10, respectively, could be assigned. The rovibrational fitting of the observed energy levels shows that some rotational levels of the (303) and (025) bright states are perturbed by interaction with the (232), (510) and (124) dark states. The observed energy levels could be reproduced with a rms deviation of 5×10⁻³ cm⁻¹ using a global analysis based on an effective Hamiltonian including the five interacting states. The energy values of the three dark vibrational states provided by the fit are found in good agreement with theoretical predictions.The parameters of the resulting effective Hamiltonian and of the transition moment operator retrieved from the measured absolute line intensities allowed calculating a complete line list of 2035 transitions, available as Supplementary Material. The integrated band strengths are estimated to be 1.22×10⁻²⁴ and 3.15×10⁻²⁴ cm⁻¹/(mol cm⁻²) at 296 K for the 3ν₁+3ν₃ and 2ν₂+5ν₃ bands, respectively. A realistic error for these band strengths is 15% (see text).     

A Raman study on the coordination sites and stability of the [Al(formamide)5]Cl3 complex

Raman experiments of aluminum chloride and formamide (FA) solutions in different compositions and temperatures were carried out. Spectral changes provoked by the increase of the salt concentration were observed in different regions. The ν_CO and ν_CN modes of FA upon complexation were upshifted and suggest that the CONH hybrid (II) is stabilized by Al(III). Bands at 547 and 295 cm⁻¹, which are assigned to the ν_AlO and ν_AlN vibrations, respectively, evidence coordination through both O and N atoms of FA. The quantitative analysis performed at the carbonyl stretching region found 5 FA molecules around this cation, resulting in the formation of the [Al(FA)₅]Cl₃ complex. Its stability is maintained by whole studied concentration range and up to around 100 °C. At higher temperatures, distortions in the FA shell begin occurring and a new component at 356 cm⁻¹ is then observed and assigned to the [AlCl₄]⁻ complex.     

Molecular and vibrational structure of the extracellular bacterial signal compound N-butyryl-homoserine lactone (C4-HSL)

The molecular and vibrational structure of the title compound (C4-HSL) was studied by experimental and theoretical methods. The infrared (IR) absorption spectrum was measured in the solid state and in CCl₄ suspension. The observed absorption bands were compared with transitions obtained with B3LYP/cc-pVTZ density functional theory (DFT) calculations. Two stable molecular conformations were predicted, corresponding to an endo- and an exo-conformer with similar energies. Intermolecular amide–amide hydrogen bonding in the crystal state was approximated by a simple cluster model, leading to excellent agreement with the observed solid state IR spectrum. Due to the low solubility of C4-HSL in common solvents for IR spectroscopy, such as CS₂ and CCl₄, a liquid solution spectrum of pure, monomeric C4-HSL was not obtained. However, absorbance peaks observed in oversaturated CCl₄ solution could be assigned to distinct contributions from suspended micro-crystalline aggregates and dissolved monomeric species. The key vibrational bands of the monomeric form of C4-HSL are reported here for the first time: 3425 cm^?1 [ν(N–H)], 1784 cm^?1 [ν(CO), lactone], 1688 cm^?1 [amide I], and 1494 cm^?1 [amide II] (CCl₄).     

An infrared study on Langmuir–Blodgett films of 14,15-bis(hydroxyimino)-13-thiaoctacosane

The Langmuir–Blodgett (LB) films of 14,15-bis(hydroxyimino)-13-thiaoctacosane (TOC) on aluminium plated substrates were investigated using Fourier transform infrared (FTIR), grazing angle (GAIR) and horizontal attenuated total reflectance (HATR) techniques. The LB films of TOC can be transferred onto the solid substrate successfully. The molecular structure of LB films was analysis by comparing the GAIR and HTAR spectra. The intense bands at 2848 and 2918 cm⁻¹ are assigned to symmetric ν_s(CH₂) and asymmetric ν_a(CH₂) stretching vibrations of methylene groups. These peaks suggest that the alkyl chains in TOC are nearly in all-trans conformational state. The presence in the infrared spectra of several bands due to the methylene wagging and twisting modes and of the splitting of the bands due to the methylene scissoring mode at 1467 and 1459 cm⁻¹ and the CH₂ rocking mode at 720 and 731 cm⁻¹ also indicates that in films of TOC alkyl chains are in the all-trans conformation and packed in either an orthorhombic or a monoclinic structure with an orthorhombic subcell containing two mutually orthogonal molecules. Another conclusion presented in this paper that the alkyl chain tilt, which is the angle between the axis, which bisects the C–C bonds and the surface normal, was quite large by comparing the GAIR and HATR spectra.     

Benefits of near-infrared spectroscopy for characterization of selected organo-montmorillonites

The potential of near infrared (NIR) spectroscopy in characterization of organically modified clay minerals is introduced. Selected organo-clays, possibly perspective fillers in clay polymer nanocomposites, were prepared from Na-montmorillonite and different surfactants containing octylammonium chain(s), hexadecylammonium chain(s) or a benzene ring with or without a reactive double bond. Based on the stretching (ν) and bending (δ) vibrations observed in the middle IR (MIR) region, the first overtone (2νXH) and combination (ν + δ)XH modes of XH groups (X = O, C, N) are identified. The effect of larger alkylammonium cations on the vibrations of Si-O and OH bonds in montmorillonite layers is observed. The changes in the intensity of the (ν + δ)H₂O band near 5250 cm⁻¹ allows for comparison of the amount of water adsorbed on the montmorillonite surface. The water content decreases with the size of the organic cation reflecting increasing hydrophobicity of the montmorillonite surface. The NIR region shows the 2νCH₃ and 2νCH₂ bands in the 5900-5500 cm⁻¹ region, an upward shift is observed for the complex band due to 2νCH(Ar) of aromatic benzene ring. The NIR spectra are extremely useful in identification of NH₂⁺, NH⁺ and vinyl groups, which are difficult to recognize in the MIR spectra of organo-clays due to overlapping with other absorption bands. The intense bands corresponding to overtones and combination vibrations of NH₃⁺ and NH₂⁺ groups are found in the 6600-6050 cm⁻¹ and 5000-4600 cm⁻¹ regions, the (ν + δ)NH⁺ is unambiguously identified near 4750 cm⁻¹. The characteristic band assigned to 2νCH₂ in H₂CC is detected near 6130 cm⁻¹.     

A FTIR study of ethylene oxidation on an Ru/ZnO system

The interaction of ethylene with a highly dispersed and oxidized Ru/ZnO catalyst has been studied at room temperature (RT) by FTIR spectroscopy. A fast oxidative reaction at RT produces a glycolate-like species strongly adsorbed on the surface, and at the same time the depletion of a strong and narrow band assigned to an RuO surface group. The assignment of the spectrum of a C₂H₄O₂ complex, characterized by two intense bands at 1035 and 890 cm⁻¹ and by 10 other bands in the range 3000-700cm⁻¹, is performed on the basis of a C_2ν symmetry and confirmed by C₂D₄ oxidation data; this assignment is performed by comparison of our spectra with the literature data for ethylene glycol and related complexes. A long oxidative reaction at RT with formation of formate and carboxylate-like species at the expense of the glycolate was also observed.     

High-resolution Fourier transform infrared spectroscopy and analysis of the ν12 fundamental band of ethylene-d4

The Fourier transform infrared (IR) spectrum of the ν₁₂ fundamental band of ethylene-d₄ (C₂D₄) has been measured with an unapodized resolution of 0.004 cm⁻¹ in the frequency range of 1030–1130 cm⁻¹. A total of 1340 assigned transitions have been analyzed and fitted using a Watson's A-reduced Hamiltonian in the I^r representation to derive rovibrational constants for the upper state (v₁₂=1) up to five quartic terms with a standard deviation of 0.00042 cm⁻¹. They represent the most accurate constants for the band thus far. The ground state rovibrational constants were also further improved by a fit of combination–differences from the IR measurements. The relatively unperturbed band was found to be basically A-type with a band centre at 1076.98492±0.00003 cm⁻¹.     

Vibrational (i.r. and Raman) spectra and conformational studies of 1-formyl-3-thiosemicarbazide

The i.r. and Raman spectra (30–4000 cm⁻¹) of 1-formyl-3-thiosemicarbazide (FTSC) and deuterated ftsc-d₄, have been studied. Most of the vibration modes reveal pairs of bands and show strong temperature dependence. A band group {ν(NNH₂)} at ∼ 1100 cm⁻¹ exhibits well resolved doublet (1095 and 1112 cm⁻¹) structure below 100 k. The intensity in the 11 12 cm⁻¹ band decreases regularly (band disappears at 150 K) with the rise in temperature. Two new bands at 955 and 1070 cm⁻¹ appear while measured above 400 K. The system eventually exists in several conformers in simultaneous equilibria. Moreover, a few bands {e.g. ν(CO), ν(CS) and ν(CH)} that show strong intensifies in i.r. exhibit weak (or zero) intensifies in the Raman and vice-versa. The features (characteristic of u and g vibration species) could be explained by a C_2h pseudo symmetry space group proposed for the system. Both the FTSC and FTSC-d₄ represent strong molecular associations. This favours the maximum abundance in the dimer stabilized conformers.     

Vibrational spectroscopic study of syngenite formed during the treatment of liquid manure with sulphuric acid

Syngenite (K₂Ca(SO₄)₂·H₂O), formed during treatment of manure with sulphuric acid, was studied by infrared, near-infrared (NIR) and Raman spectroscopy. C_s site symmetry was determined for the two sulphate groups in syngenite (P2₁/m), so all bands are both infrared and Raman active. The split ν₁ (two Raman+two infrared bands) was observed at 981 and 1000 cm⁻¹. The split ν₂ (four Raman+four infrared bands) was observed in the Raman spectrum at 424, 441, 471 and 491 cm⁻¹. In the infrared spectrum, only one band was observed at 439 cm⁻¹. From the split ν₃ (six Raman+six infrared) bands three 298 K Raman bands were observed at 1117, 1138 and 1166 cm⁻¹. Cooling to 77 K resulted in four bands at 1119, 1136, 1144 and 1167 cm⁻¹. In the infrared spectrum, five bands were observed at 1110, 1125, 1136, 1148 and 1193 cm⁻¹. From the split ν₄ (six infrared+six Raman bands) four bands were observed in the infrared spectrum at 604, 617, 644 and 657 cm⁻¹. The 298 K Raman spectrum showed one band at 641 cm⁻¹, while at 77 K four bands were observed at 607, 621, 634 and 643 cm⁻¹. Crystal water is observed in the infrared spectrum by the OH-liberation mode at 754 cm⁻¹, OH-bending mode at 1631 cm⁻¹, OH-stretching modes at 3248 (symmetric) and 3377 cm⁻¹ (antisymmetric) and a combination band at 3510 cm⁻¹ of the H-bonded OH-mode plus the OH-stretching mode. The near-infrared spectrum gave information about the crystal water resulting in overtone and combination bands of OH-liberation, OH-bending and OH-stretching modes.     

Synthesis,spectral studies,antimicrobial and insect antifeedant activities of some substituted styryl 4′-fluorophenyl ketones

Good yield of some substituted styryl 4′-fluorophenyl ketones were synthesized by solvent free fly-ash:water catalyzed eco-friendly environmentally benign Aldol reaction. These chalcones were characterized by physical constants, micro analysis and spectral data. Antimicrobial and insect antifeedant activities were measured in all chalcones. The group frequencies of all chalcones like carbonyl stretches νCO, C–F and the deformation modes of vinyl part of CH– out of plane, in-plane, CHCH out of plane and >CC< out of plane (cm⁻¹), the vinyl hydrogen and carbons δ(ppm) of H_α, H_β, C_α, C_β and CO were assigned and these frequencies were correlated with various kinds of substituent constants. From the results of statistical analysis the influence of electronic effects of substituents on the spectral data of carbonyl group, vinyl proton and carbons of the ketones have been explained.     

Far infrared spectra of mono- and bisphthalocyanine derivatives

The far infrared spectra of a series of unsubstituted monophthalocyanine (Pc) and di-Pc derivatives and some of the corresponding tetra-tert-butyl substituted Pc molecules are reported. The infrared data were recorded between 100 and 4.50 cm⁻¹. The vibrational assignment of metal-nitrogen stretching frequencies is discussed. The far infrared data for tert-butyl Pc derivatives and a group of C_4ν Pc complexes are presented here for the first time.     

In situ infrared and EXAFS studies of an Ag cluster in zeolite X

The in situ measurements of infrared spectra and the Ag K-edge EXAFS spectra of the fully Ag⁺ exchanged zeolite X (Ag₈₆–X) were carried out from room temperature to 300 °C under vacuum. By evacuation at room temperature the O–H stretch vibration (ν(O–H)) mode around 3 μm disappears and the coordination number of oxygen around Ag, N_Ag–O, decreases due to removal of water molecules. The T–O asymmetric stretch (ν_as(T–O)) mode associated with zeolite framework oxygen appears around 10 μm. These infrared spectra are fitted by summing up Gaussian peaks. The positions of the main two peaks are 1000 and 1100 cm⁻¹ at room temperature. At 100 °C, a third infrared peak appears at around 955 cm⁻¹, the total N_Ag–O becomes small and the coordination number of Ag around Ag, N_Ag–Ag, is 0.5. These results suggest that Ag atoms change sites in the zeolite and play an important role as a precursor of the Ag clusters. At 300 °C, the peaks around 1000 and 1100 cm⁻¹ shift to 1050 and 1140 cm⁻¹, respectively, and N_Ag–Ag becomes 2.9, which indicates that the Ag clusters attached to the zeolite framework are stabilized at high temperature. When the zeolite with Ag clusters is exposed to atmosphere, it is found that: (1) the ν(O–H) mode around 3 μm appears again, (2) there are two main peaks (1000 and 1100 cm⁻¹) and a small peak around 856 cm⁻¹ and (3) the local structure of the Ag clusters formed at 300 °C never reverses.     

Hydrogen bond effect on the bonding and B2 molecular vibrations of pyrrole

The influence of the hydrogen bond on the infrared B₂ symmetry modes of pyrrole (C_2ν) has been studied. CNDO/2 calculations suggest that the most probable structure for the associated pyrrole involves the interaction NH ⋯ π. The shortest distance between the nitrogen atom and the ring of the nearest neighbor molecule is about 2.9 Å. The absorption bands of pyrrole in the gaseous state at 474, 626 and 720 and 826 cm⁻¹ have been assigned to the NH, ring and CH out-of-plane deformation modes.     

Vibrational spectroscopic characterization of the phosphate mineral series eosphorite–childrenite–(Mn,Fe)Al(PO4)(OH)2·(H2O)

The phosphate mineral series eosphorite–childrenite–(Mn,Fe)Al(PO₄)(OH)₂·(H₂O) has been studied using a combination of electron probe analysis and vibrational spectroscopy. Eosphorite is the manganese rich mineral with lower iron content in comparison with the childrenite which has higher iron and lower manganese content. The determined formulae of the two studied minerals are: (Mn_0.72,Fe_0.13,Ca_0.01)(Al)_1.04(PO₄, OHPO₃)_1.07(OH_1.89,F_0.02)·0.94(H₂O) for SAA-090 and (Fe_0.49,Mn_0.35,Mg_0.06,Ca_0.04)(Al)_1.03(PO₄, OHPO₃)_1.05(OH)_1.90·0.95(H₂O) for SAA-072. Raman spectroscopy enabled the observation of bands at 970 cm⁻¹ and 1011 cm⁻¹ assigned to monohydrogen phosphate, phosphate and dihydrogen phosphate units. Differences are observed in the area of the peaks between the two eosphorite minerals. Raman bands at 562 cm⁻¹, 595 cm⁻¹, and 608 cm⁻¹ are assigned to the ν₄ bending modes of the PO₄, HPO₄ and H₂PO₄ units; Raman bands at 405 cm⁻¹, 427 cm⁻¹ and 466 cm⁻¹ are attributed to the ν₂ modes of these units. Raman bands of the hydroxyl and water stretching modes are observed. Vibrational spectroscopy enabled details of the molecular structure of the eosphorite mineral series to be determined.