Synthesis of an optically active helical poly(1,3-phenyleneethynylene) bearing stable radicals and its chiroptical and magnetic properties

We synthesized an optically active helical poly(1,3-phenyleneethynylene) with pendant galvinoxyl residues and dimethyl(10-(1S)-pinanyl)silyl groups. The hydrogalvinoxyl precursor polymer was given by polymerization of (1,3-diiodophenyl)hydrogalvinoxyl and 1,3-diethynyl-5-[dimethyl(10-(1S)-pinanyl)silyl]benzene using Pd(PPh₃)₄ catalyst (M_w = 1.7 × 10⁵, M_w/M_n = 3.7). In the CD spectrum taken in ethyl acetate solution, clear Cotton effects were observed in the absorption region of the backbone and hydrogalvinoxyl chromophore, indicating an excess of one-handed helical foldamer conformation. The polymer yielded the corresponding polyradical with high spin concentration by treatment of the polymer solution with PbO₂. The Cotton effects appeared in CD spectra of the polymer and polyradical by addition of methanol to the chloroform solution, although the Cotton effects were hardly observed in chloroform. On the other hand, in the MCD spectra of the polymer and polyradical taken in chloroform solution, Faraday effects were observed in the absorption region of the backbone and galvinoxyl chromophore. The static magnetic susceptibility of the chiral polyradical was measured using a SQUID magnetometer, and showed the antiferromagnetic interaction.     

Characterization and catalytic properties of nickel-substituted hexagonal mesoporous silica prepared by microwave-hydrothermal method

The liquid phase of acetylation of 1,2-dimethoxybenzene with acetic anhydride has been investigated over a series of acid nickel-mesoporous materials (Ni-MCM-41) synthesized by the microwave irradiation method with different Si/Ni ratios (Si/Ni = 80, 50, 10) and characterized by several spectroscopic techniques such as: N₂ physical adsorption, ICP, XRD, TEM, FT-IR, and a temperature programmed desorption (TPD) of pyridine. In fact, the catalyst Ni-MCM-41 (10) showed better performance in the acid-catalyzed acetylation of 1,2-dimethoxybenzene employing acetic anhydride as an acylating agent. Furthermore, the kinetics of the acetylation of 1,2-dimethoxybenzene over these catalysts have also been investigated.     

Quantitative analysis of hydrogen bonding in electrospun fibers of poly(4-vinyl pyridine)/(4,4′-biphenol) complexes by ATR using liquid blends as models

To understand the characteristics of electrospun fibers of poly(4-vinyl pyridine) (P4VP) that are potentially crosslinked by hydrogen-bonding when blended with small molecules like 4,4′-biphenol (BiOH), it is necessary to determine the proportion of hydrogen-bonded pyridine rings (f_b) and to contrast it with F_OH, the mole percent of OH groups available for interacting with the pyridine rings. While this can be done by Fourier transform infrared spectroscopy (FTIR), two practical difficulties must be overcome. First, the correct intensities of the overlapped bands of free and hydrogen-bonded pyridine must be obtained, which is possible using the second derivative spectra. Second, the band absorption coefficient ratio (a) of the pair of bands must be known. In the P4VP/BiOH system, only the pair of free and hydrogen-bonded pyridine ring bands at 993 and 1007 cm⁻¹ can be used for quantitative analysis. We determined, by analysis of liquid blends of BiOH as well as phenol with a model compound, 4-ethylpyridine (EtPy), using the attenuated total reflection mode (ATR), that a = 0.40. This led to values of f_b = F_OH, indicative of full complexation of the OH groups to pyridine, in the EtPy/BiOH liquid blends up to the BiOH solubility limit in EtPy (F_OH = 60%) and in the EtPy/phenol blends up to F_OH = 100%. In the electrospun P4VP/BiOH fibers prepared from solutions with F_OH up to about 120%, f_b averages 0.76F_OH, and full complexation of the pyridine groups is achieved only at about F_OH = 160%. In both P4VP/BiOH and EtPy/BiOH, the complexation occurs between one pyridine ring and one hydroxyl group. This work thus shows a new method to quantify the relative number of hydrogen-bonded pyridine rings in P4VP; it is expected to be applicable to other polymer-small molecule and polymer-polymer blends having suitable liquid models.     

Hypervalent iodine(III) catalyzed rapid and efficient access to benzimidazoles,benzothiazoles and quinoxalines: Biological evaluation of some new benzimidazole-imidazo[1,2-a]pyridine conjugates

A rapid, simple and highly efficient method for the synthesis of a variety of 2-aryl-benzimidazoles, 2-aryl-benzothiazoles and quinoxalines has been developed using Koser’s reagent [PhI(OH)OTs] as catalyst. The present work highlights the potential of Koser's reagent ([PhI(OH)OTs]) for the synthesis of benzimidazoles, benzothiazoles and quinoxalines, etc. Short reaction time, high yields, importantly low catalyst loading, broad substrate scope and scalability are the salient features of this methodology. Particularly, this method has been employed successfully to synthesize highly structured indole-benzimidazole and quinoxaline-6-carboxamide derivatives as well as biologically important benzimidazole-imidazo[1,2-a]pyridine conjugates in moderate to good yields. These remarkable features make the present methodology a valid contribution to the existing precedents for the synthesis of benzimidazoles, etc. In the MTT assay, benzimidazole-imidazo[1,2-a]pyridine conjugates 3s, 3t and 3v were found to be active on MCF-7 (IC₅₀ values of 5.10 ± 0.10, 8.23 ± 0.02, and 10.75 ± 0.03 µM, respectively) and MDA-MB-231 cell lines (IC₅₀ values of 10.83 ± 0.13, 7.68 ± 0.05, and 7.87 ± 0.24 µM, respectively). Flow-cytometry analysis revealed that the treatment of MCF-7 cells with compound 3s showed moderate effect on the progression of G0/G1 phase of the cell cycle.     

Infrared and Raman spectra of magnesium ammonium phosphate hexahydrate (struvite) and its isomorphous analogues. IX: Spectra of protiated and partially deuterated cubic magnesium caesium phosphate hexahydrate

Infrared and Raman spectra of cubic magnesium caesium phosphate hexahydrate, MgCsPO₄·6H₂O (cF100), and its partially deuterated analogues were analyzed and compared to the previously studied spectra of the hexagonal analogue, MgCsPO₄·6H₂O (hP50). The vibrational spectra of the cubic and hexagonal dimorphic analogues are similar, especially in the regions of HOH stretching and bending vibrations. In the difference IR spectrum of the slightly deuterated analogue (<5% D), one distinctive band appears at 2260 cm⁻¹ with a small shoulder at around 2170 cm⁻¹, but only one band is expected in the region of the OD stretchings of isotopically isolated HDO molecules. The small weak band could possibly result from second-order transitions (a combination of HDO bending and some libration of the same species) rather than statistical disorder of the water molecules. By comparing the IR spectra in the region of external vibrations of water molecules of the protiated compound recorded at RT (room temperature) and at LNT (liquid nitrogen temperature) and those in the series of the partially deuterated analogues, it can be stated with certainty that the bands at 924 and 817 cm⁻¹ result from librations of water molecules, rocking and wagging respectively. And the band at 429 cm⁻¹ can be safely attributed to a stretching Mg–O_w mode. In the ν₃(PO₄) and ν₄(PO₄) region in the infrared spectra, one band in each is observed, at 995 and 559 cm⁻¹, respectively. In the region of the ν₁ modes, in the Raman spectrum of the protiated compound, one very intense band was observed at 930 cm⁻¹ which is only insignificantly shifted to 929 cm⁻¹ in the spectrum of the perdeuterated compound. The band at 379 cm⁻¹ in the Raman spectrum could be assigned to the ν₂(PO₄) modes. With respect to the phosphate ion vibrations, the comparison between the two polymorphic forms of MgCsPO₄·6H₂O and their deuterated compounds shows that ν₁(PO₄) and ν₃(PO₄) appear at lower wavenumbers in the cubic phase than in the hexagonal phase. These data are in full agreement with the lower repulsion potential at the cubic lattice sites compared with that for the hexagonal lattice sites.     

Esterification of acetic acid with n-Butanol using vanadium oxides supported on γ-alumina

Esterification of acetic acid with n-Butanol has been studied in a heterogeneous reaction system using two γ-alumina-supported vanadium oxide catalysts with different V loadings, which were prepared by the impregnation of a precipitated alumina. The alumina support and the supported catalysts were characterized using X-ray diffraction, N₂ adsorption, EDX analysis and NH₃-TPD techniques. The effects of the reaction time, of the molar ratio of the reactants, of the speed of agitation and of the mass fraction of the catalyst on the catalytic properties were studied. In the presence of the supported catalyst containing 10 wt % V₂O₅ (10V-Al₂O₃ sample) the conversion reached 87.7% after 210 min of reaction at 100 °C with an n-Butanol-to-acetic acid mole ratio equal to one. The conversion as well as the total acidity measured by TPD of NH₃ increased in the following order: Al₂O₃ < 5V-Al₂O₃ (5 wt % V₂O₅/Al₂O₃) < 10V-Al₂O₃. In all cases the reaction was completely selective to n-butyl acetate. Nevertheless, a loss in catalytic activity after three reaction cycles with 10 V₂O₅–Al₂O₃ catalyst was observed.     

Excited state structural dynamics and Herzberg–Teller coupling of tetraphenylporphine explored via resonance Raman spectroscopy and density functional theory calculation

Resonance Raman spectra of free-base tetraphenylporphine (TPP) were obtained with 397.9, 416, and 435.7 nm excitation wavelengths and density functional calculations were done to elucidate the electronic transitions and the resonance Raman spectra (RRs) of TPP. The RRs indicate that the Franck–Condon region photodynamics for S₀ → S₄ electronic state is predominantly along the C_m–ph stretch while that for S₀ → S₃ electronic state is predominantly along the porphin ring C_βC_β stretch. Non-totally symmetric vibrational modes were regularly presented in resonance Raman spectra: the shorter the excitation wavelengths were, the stronger intensity the modes had, which can be interpreted in terms of electric dipole transition moments caused by Franck–Condon and Herzberg–Teller coupling.Four non-total symmetry vibrational mode υ_52, υ₆₄, υ₉₇ and υ₁₃₀ in A₂ irreducible representative of TPP were observed in 397.9, 416 and 435.7 nm resonance Raman spectrum. With the shorter wavelength laser excitations at 416 or 397.9 nm, the A₂ vibrational modes show more enhanced Raman intensity by comparison with those in the TPP spectrum excited at 435.7 nm.     

LIF technique offers the potential for the detection of cadmium-induced alteration in photosynthetic activities of Zea Mays L.

The laser-induced fluorescence spectra of leaves of Zea mays L. plants treated with different concentrations (0.01, 0.10 and 1.00 mM) of cadmium were recorded in region 650–800 nm using 488 nm line of Argon Ion laser as excitation source and PMT as detector. Besides this, blue-green fluorescence and Chl fluorescence were also measured using third harmonic (355 nm) of Nd:YAG laser as excitation source and 320 M monochromator with intensified charge coupled device as a detector in the region 400–800 nm. These spectra have been used to analyse the effect of several doses of cadmium on the photosynthetic activities of Z. mays L. plants. The fluorescence intensity ratios (FIR) of control as well as treated Z. mays L. were calculated by evaluating curve-fitted parameters using Gaussian spectral function. In addition, growth parameters like photosynthetic pigments content were also estimated. The chlorophyll fluorescence intensity ratio F685/F735 excited by both 488 and 355 nm lines are strongly correlated with photosynthetic pigments content (total chlorophyll and carotenoids) and their ratios. Consequently, there also existed a correlation between the blue-green fluorescence intensity ratio F470/F540 and photosynthetic pigments content.     

Methanol adsorption on γ-irradiated SiO2 surface

The adsorption of methanol on γ-irradiated and un-irradiated SiO₂ surfaces pretreated at 473 K was investigated by Fourier transform infrared spectroscopy, temperature programmed desorption (TPD) and pulse methods. Methanol adsorbed only in molecular form on the un-irradiated sample. Treating the pre-irradiated silica surface with methanol at room temperature formaldehyde and hydrogen were formed. The methanol adsorbed on the irradiated silica transformed to formyl groups during a longer time at room temperature and desorbed as formaldehyde simultaneously with CH₃OH (T_max=395 K) on the TPD.     

The FTIR spectra of substituted tetraoxa[8]circulenes and their assignments based on DFT calculations

The FTIR spectrum of symmetrical derivative of the tetraoxa[8]circulene, named para-dinaphthyleno-2,3,10,11-tetraundecyldiphenylenotetrafuran (p-2B2N4R, R = n-C₁₁H₂₃) has been recorded and interpreted using density functional theory (DFT) calculations for the model compounds p-2B2N4R (R = H, C₂H₅). The unsubstituted tetraoxa[8]circulene, namely para-dinaphthylenodiphenylenotetrafuran (p-2B2N) and para-dinaphthyleno-2,3,10,11-tetraethyldiphenylenotetrafuran (p-2B2N4R, R = C₂H₅) belong to the D_2h and D₂ symmetry point groups, respectively. The equilibrium molecular geometry, harmonic vibrational frequencies and infrared intensities have been calculated utilizing the DFT/B3LYP method with the 6–31G(d) basis set using the symmetry constraints. Comparison of the calculated vibrational spectra with the experimental data provides a reliable assignment of the observed bands in the FTIR spectra. The results of quantum-chemical calculations provide a complete interpretation of vibrational modes based on a good agreement with all details of the experimental spectra.     

Raman study on pentacene:C60 bulk heterojunction films

We measured 785 nm excited Raman and infrared spectra of pentacene-d₁₄. The observed spectra were assigned on the basis of the Raman and infrared spectra calculated by the density functional theory (DFT) method at the B3LYP/6⬜311 + G** level. We measured 785 nm excited Raman spectrum of a pentacne-d₁₄:C₆₀ bulk heterojunction film. The spectrum was assigned on the basis of the wavenumber shifts upon deuteration of pentacene. The assignments of the 1462 and 493 cm^↙1 A_g bands of C₆₀ were confirmed. The 511, 453, and 256 cm^↙1 bands, which were observed only in pentacene:C₆₀ bulk heterojunction films, did not show large deuteration shifts. This result indicates that the 511, 453, and 256 cm^↙1 bands are attributed to activation of the silent modes of C₆₀ due to symmetry lowering_.     

Flow-injection chemiluminescence determination of dihydralazine sulfate in serum using luminol and diperiodatocuprate (III) system

A novel flow-injection chemiluminescence (CL) method for the determination of dihydralazine sulfate (DHZS) is described. The method is based on the reaction of luminol and diperiodatocuprate (K₂[Cu(H₂IO₆)(OH)₂], DPC) in alkaline medium to emit CL, which is greatly enhanced by DHZS. The possible CL mechanism was first proposed based on the kinetic characteristic, CL spectrum and UV spectra. The optimum condition for the CL reaction was in detail studied using flow-injection system. The experiments indicated that under optimum condition, the CL intensity was linearly related to the concentration of DHZS in the range of 7.0 × 10^?9 to 8.6 × 10^?7 g mL^?1 with a detection limit (3σ) of 2.1 × 10^?9 g mL^?1. The proposed method had good reproducibility with the relative standard deviation 3.1% (n = 7) for 5.2 × 10^?8 g mL^?1 of DHZS. This method has the advantages of simple operation, fast response and high sensitivity. The special advantage of the system is that very low concentration of luminol can react with DPC catalyzed by DHZS to get excellent experiment results. And CL cannot be observed nearly when luminol with same concentration reacts with other oxidants, so luminol–DPC system has higher selectivity than other luminol CL systems. The method has been successfully applied to determine DHZS in serum.     

Photocatalytic reduction of cadmium over CuFeO2 synthesized by sol–gel

The Cd²⁺ photo-electrodeposition was successfully carried out in air-equilibrated aqueous CuFeO₂ suspension. The delafossite CuFeO₂ is p-type semiconductor characterized by a low optical gap, properly matched to the sun spectrum, and a long term chemical stability in neutral solution. It has been elaborated by the sol–gel technique where the specific surface area is increased via the surface/bulk ratio. The TG/DSC plots and IR spectra show that the solid phases are formed only at temperatures exceeding 400 and at 700 °C, the system is mixed phases. When fired at 950 °C under nitrogen flow, the delafossite has been identified (CuO + CuFe₂O₄ → CuFeO₂ + ½O₂). All the XRD lines index in a hexagonal unit cell with the lattice constants a = 284.2 and c = 169.4 pm. The photocurrent onset potential (+0.35 V_SCE) is close to the flat band potential (+0.23 V_SCE) determined from the capacitance measurement. CuFeO₂/Cd²⁺ solution is a self photo-driven system, the absorption of light promotes electrons into CuFeO₂–CB with a potential (?0.93 V_SCE) sufficient to reduce Cd²⁺. This occurs because of the dark Cd²⁺ adsorption on the surface powder. The system was optimized with respect to the following physical parameters: pH 6.8, Cd²⁺ (100 ppm) and a mass concentration C_m (1 mg catalyst/ml solution). The hetero-system CuFeO₂/TiO₂ has been also reported for a comparative purpose. Prolonged irradiation (>50 min) was accompanied by a pronounced decrease in the rate of Cd-deposition owing to the competitive water reduction. Indeed, the generated bi-functional CuFeO₂/Cd particles account for the low over-potential of hydrogen and favour its evolution in aqueous solution.     

XAFS characterization of La1−xSrxMnO3±δ catalysts prepared by Pechini’s method

XAFS experiments at the Mn and Sr K-edges were carried out in order to investigate the short-range arrangement of Mn and Sr sites on La_1−xSr_xMnO_3±δ highly doped perovskites (x = 0, 0.2, 0.4 and 0.6). The Mn K-edge EXAFS spectra show a static Jahn–Teller distortion of the MnO₆ for x = 0 and 0.2, which is drastically reduced as x increases. The distortion of perovskite, characterized by the Mn–O–Mn tilt angle, progressively decreases with increasing Sr contents. Sr K-edge results indicated a decrease on the Sr–Mn coordination number upon Sr doping. Based on this and TPD results, a charge compensating mechanism is proposed suggesting a partial Mn oxidation and formation of Mn defect vacancies due to the introduction of Sr.     

Preparation and thermal properties of lanthanide complexes with 2,3-dichlorobenzoic acid and 1,10-phenanthroline

Three lanthanide complexes with a general formula [Ln(2,3-DClBA)₃phen]₂ (Ln(III) = Eu(1), Tb(2), Ho(3); 2,3-DClBA = 2,3-dichlorobenzoate; phen = 1,10-phenanthroline) were synthesized and characterized by elemental analysis, molar conductance, infrared and ultraviolet spectra and powder X-ray diffraction (XRD). The luminescent properties of the complexes 1 and 2 were studied. The thermal behaviors of the complexes were also discussed by thermogravimetric (TG), differential thermogravimetric (DTG) and infrared spectra (IR) techniques. The heat capacities of the complexes were measured from 259.15 to 493.02 K by means of Differential scanning calorimeter (DSC). The dependence of heat capacity on the reduce temperature x (x = [T ? (T_max + T_min)/2]/[(T_max ? T_min)/2]) was fitted to a polynomial equation with the least squares method for each complex. Furthermore, based on the fitted polynomial, the smoothed heat capacities and the derived thermodynamic functions (H_T ? H_298.15 K), (S_T ? S_298.15 K) and (G_T ? G_298.15 K) in the measured temperature range were obtained with an interval of 10 K.     

Glass transition in polymers monitored by synchronous scan spectra

The synchronous scan spectra (SSS) technique was successfully applied to monitor the macromolecular chain motions near the glass transition temperature in polystyrene (PS) and poly (vinyl methyl ether) (PVME) films on a copper substrate. In SSS of PS and PVME films, two peaks at 467 nm and 473 nm, which correlated to the light source spectrum of the spectrofluorimeter, were used to characterize the glass transition of polymers. By monitoring the intensity of peaks at 467 and 473 nm in the spectra, the intensity-temperature curves exhibited kinks near the glass transition. The kinks have also been shown in plots of I_R473/I_R467 vs. temperature, which implies the distinct fluctuation of SSS intensity distribution at the glass transition temperature of the polymer. As a spectroscopy measurement method with simplicity, rapidity and sensitivity, the SSS method was proved to be able to monitor the glass transition in polymers, which has been commonly measured by differential scanning calorimetry (DSC).     

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.     

Achiral additives dramatically enhance enantioselectivities in the BINOL–Ti(IV) complex catalyzed aldol condensations of aldehydes with Chan’s diene

Achiral additives can dramatically enhance the enantioselectivities in the BINOL–Ti(IV) complex catalyzed aldol condensations of aldehydes with Chan’s diene. The best results were obtained by using 2.0 equiv of LiCl with respect to (S)-BINOL/Ti(Oi-Pr)₄ as the additive. In the presence of 4.0 mol % of LiCl and 2.0 mol % of BINOL/Ti(Oi-Pr)₄, all aldehydes tested gave δ-hydroxy-β-ketoesters as almost pure single enantiomers. Moreover, the present catalyst system was highly effective on reducing the catalyst loadings to 0.1 mol %.     

Investigation of steam reforming of acetic acid to hydrogen over Ni–Co metal catalyst

Catalytic generation of hydrogen by steam reforming of acetic acid over a series of Ni–Co catalysts have been studied. The catalyst with the molar ratio of 0.25:1 between Ni and Co was superior to other catalysts. The effects of reaction temperature, liquid hourly space velocity (LHSV) and molar ratios of steam-to-carbon (S/C) were studied in detail over this catalyst. At T = 673 K, LHSV = 5.1 h⁻¹, S/C = 7.5:1, the catalyst exhibited the best performances. Acetic acid was converted completely to hydrogen, while H₂ selectivity reached up to 96.3% and CO₂ selectivity up to 98.1% was obtained, respectively. Ni–Co catalyst showed rather stable performances for the 70 h time-on-stream without any deactivation.     

Synchronous ATR infrared and NIR-spectroscopy investigation of sepiolite upon drying

A new environmental cell allowing for the independent synchronous collection of the near- and mid-infrared spectra (12,000–600 cm⁻¹) in the diffuse reflection and attenuated total reflection (ATR) modes, respectively, is reported. The cell is employed to study in real time the dehydration of the phyllosilicate mineral sepiolite, Mg₈Si₁₂O₃₀(OH)₄(OH₂)₄·wH₂O, in both its natural form and after in situ deuteration at ambient. The spectra are obtained under dynamic purging with dry N₂ and compared to those of the same material conditioned over saturated salt solutions. Sepiolite is an important industrial mineral with a modulated structure of alternating tunnels and ribbons. Its mild drying is associated with pronounced vibrational spectral changes due to the removal of surface and zeolitic H₂O and the concomitant structural relaxation of the ribbons. Detailed assignments are provided for the fundamental, combination and overtone spectrum of H₂O confined in the tunnels of sepiolite, SiOH groups on the external surface of the particles, and Mg₃OH groups in the 2:1 ribbons. The spectra are discussed in comparison to those of palygorskite (modulated phyllosilicate with narrower ribbons and tunnels), talc (trioctahedral magnesian phyllosilicate without modulation) and high-surface area silica. It is demonstrated that sepiolite exhibits three discrete states of zeolitic hydration at ambient temperature: Besides the previously known hydrated (w = 7–8) and dry (w = 0–1) states which dominate the spectra above 30% and below 3% relative humidity, respectively, a hitherto unknown intermediate (w = 4–5) is found in the 3–10% range. The new state is most conveniently identified in the near-infrared by a ν₀₂ Mg₃O-H stretching mode at 7205 cm⁻¹ (ν₀₁ = 3686 cm⁻¹, X = 83.5 cm⁻¹) and a characteristic H₂O combination band at 5271 cm⁻¹ (D₂O: 3908 cm⁻¹).