Spectra Of D2O Research Articles

Preparation and evaluation of fenbendazole methyl-β-cyclodextrin inclusion complexes

As an orally effective benzimidazole anthelmintic agent, fenbendazole was not only widely used in agriculture and animal husbandry to prevent and treat parasites, but also shows anti-cancer effects against several types of cancer, exhibits anti-cancer effects in paclitaxel and doxorubicin-resistant cancer cells. However, fenbendazole’s poor in water solubility (0.3 µg/mL), limits its clinical applications. Even great efforts were made toward increasing its water solubility, the results were not significant to reach anti-cancer drug delivery requirement (5–10 mg/mL). Through single factor and orthogonal strategy, many complex conditions were designed and used to prepare the complexes, the inclusion complex with methyl-β-cyclodextrin with 29.2 % of inclusion rate and 89.5% of inclusion yield can increase drug’s water solubility to 20.21 mg/mL, which is the best result so far. Its structure was confirmed by differential scanning calorimetry, scanning electron microscopic image, 1D and 2D NMR spectra in D2O. In its in vitro pharmacokinetic study, fenbendazole was 75% released in 15 min., in its in vivo pharmacokinetic study, the bio-availabilities of fenbendazole, its major metabolic anthelmintic agent oxfendazole and its minor metabolic anthelmintic agent oxfendazole were increased to 138%, 149% and 169% respectively, which would allow for fewer drug doses to achieve the same therapeutic effect and suggest that the complex can be used as a potential anticancer agent.

Theoretical and experimental OD-stretch vibrational spectroscopy of heavy water.

In view of the current situation in which the OD-stretch vibrational spectra have been scarcely computed with non-polarizable rigid D2O models, we investigate the IR and Raman spectra of D2O by using a newly-reported model TIP4P/2005-HW. From the comparison between the calculations and experimental data, we find the excellent performance of TIP4P/2005-HW for vibrational spectroscopy of D2O in the same manner as TIP4P/2005 for H2O, although one may still conveniently employ an alternative method that regards OH as putative OD to calculate the OD-stretch spectra with similar quality from TIP4P/2005 trajectories. We also demonstrate that the appropriate setting for the spectral simulation of D2O under the time-averaging approximation reflects the slower dynamics (i.e., slower motion of translation and rotation due to the heavier mass and stronger hydrogen bond) of D2O than H2O. Moreover, we show from the theoretical calculations that the established interpretation of the OH-stretch spectra of H2O is finely applicable to the OD-stretch of D2O.

Probing n-Octyl α-d-Glycosides Using Deuterated Water in the Lyotropic Phase by Deuterium NMR.

The lyotropic phase behavior of four common and easily accessible glycosides, n-octyl α-d-glycosides, namely, α-Glc-OC8, α-Man-OC8, α-Gal-OC8, and α-Xyl-OC8, was investigated. The presence of normal hexagonal (HI), bicontinuous cubic (VI), and lamellar (Lα) phases in α-Glc-OC8 and α-Man-OC8 including their phase diagrams in water reported previously was verified by deuterium nuclear magnetic resonance (2H NMR), via monitoring the D2O spectra. Additionally, the partial binary phase diagrams and the liquid crystal structures formed by α-Gal-OC8 and α-Xyl-OC8 in D2O were constructed and confirmed using small- and wide-angle X-ray scattering and 2H NMR. The average number of bound water molecules (nb) per headgroup in the Lα phase was determined by the systematic measurement of the quadrupolar splitting of D2O over a wide range of molar ratio values (glycoside/D2O), especially at high glucoside composition. The number of bound water molecules bound to the headgroup was found to be around 1.5-2.0 for glucoside, mannoside, and galactoside, all of which possesses four OH groups. In the case of xyloside, which has only three OH groups, the bound water content is ∼2.0. Our findings confirmed that the bound water content of all n-octyl α-d-glycosides studied is lower compared to the number of possible hydrogen bonding sites possibly due to the fact that most of the OH groups are involved in intralayer interaction that holds the lipid assembly together.

Dual thermo-responsive amphiphilic alternating copolymers: one-pot synthesis and the temperature-induced self-assembly

Synthesis and self-assembly of stimuli-responsive amphiphilic alternating copolymers (AAC) are an emerging land of tremendous possibilities. Herein, by combining backbone polyethylene glycol (PEG) with pendent oligo-polyglycol simultaneously, two alternating LCST segments are knitted through enzymatic synthesis, giving a series of alternating poly[(PEG400-a-succinic acid)-co-(diol(3EG)-a-succinic acid)] (PPSDS) for the first time. All the PPSDSs show only one-step sharp temperature responsiveness in transmittance–temperature curve owing to stabilization effect of PEG400. The cloud points can be linearly controlled by simply adjusting the feeding ratio of PEG400/diol-3EG. Referring to published works and 1H-NMR spectra in D2O, all the obtained AAC formed penetrable nanovesicles under 4 °C. The TEM and 1H-NMR results confirmed that when heated to 18 °C, PPSDS of “9/1” transformed from nanovesicles to large-compound micelles due to large hydrophobic volume, while other PPSDS of “8/2, 7/3, 6/4” retained the vesicle structures, except that the hydrophilic layer turned from PEG400 + diol(3EG) to PEG400 alone, leading to the size reduction. The temperature-controlled size “expansion and contraction” of nanovesicles was unique for AAC, which was potentially good for enhancing loading rate. Further heating above cloud point resulted in the destruction of nanostructures and irregular intermolecular aggregations. The first reported dual temperature-responsive AAC was innovative in structure design, providing a potential opportunity for the design and synthesis of controllable self-assemble structures and smart biomacromolecules in biomedical applications.

The absorption spectrum of D2O in the region of 0.97 μm: the 3ν1 + ν3 vibrational–rotational band

The vibrational–rotational absorption spectrum of D2O in the range from 10 120 to 10 450 cm–1 is recorded on a Fourier transform spectrometer with a resolution of 0.05 cm–1. The measurements were performed using a multipass White cell with an optical path length of 24 m. A light-emitting diode with brightness higher than that of other devices was used as a radiation source. The signal-to-noise ratio was about 104. The spectrum is interpreted as consisting of lines of more than 400 transitions. The spectral characteristics of lines (centers, intensities, and half widths) are determined by fitting the Voigt profile parameters to experimental data by the least-squares method. The intensities of lines and the experimental rotational energy levels of the (301) vibrational state of the D2 16O molecule with high rotational quantum numbers are determined for the first time.

Synthesis and crystal structure of hexacerium(IV) cluster-containing Keggin polyoxometalate trimer

A novel hexacerium(IV) cluster-containing polyoxometalate (POM), K18[{Ce6(μ3-O)4(μ3-OH)4(OAc)2}(A-α-SiW9O34)2(α-SiW11O39)]·37H2O (K18Ce6-POM), was unexpectedly obtained by a reaction of the potassium salt of open-Dawson POM, K13[{K(H2O)3}2{K(H2O)2}α,α-Si2W18O66]·19H2O (K-open POM), with (NH4)2[Ce(NO3)6], in a 0.5M KOAc/HOAc buffer solution (pH4.8) at 80°C, and unequivocally characterized by X-ray crystallography, 1H, 13C, and 29Si NMR spectroscopy, FTIR spectroscopy, complete elemental analysis, and TG/DTA. X-ray crystallography revealed that the monolacunary Keggin unit, [α-SiW11O39]8−, and the two trilacunary Keggin units, [A-α-SiW9O34]10−, are connected by a central Ce6-oxo/hydroxide cluster moiety, [Ce6(μ3-O)4(μ3-OH)4(OAc)2]10+, to form a trimeric Keggin polyanion, [{Ce6(μ3-O)4(μ3-OH)4(OAc)2}(A-α-SiW9O34)2(α-SiW11O39)]18− (Ce6-POM). 1H, 13C, and 29Si NMR spectra in D2O suggested that the Ce6-POM was obtained as a single species and its molecular structure was maintained in solution.

Absorption spectrum of D2O between 10000–11000 cm-1

A study of the vibration-rotation absorption spectrum of the D2O molecule in the range 10100–10800cm-1 has been performed. The spectrum was recorded using a Fourier Transform Spectrometer with the spectral resolution of 0.05cm-1 coupled to the multi-pass White-type cell providing an optical path length of 24m. A light-emitting diode was used as the radiation source, giving a high brightness that resulted in an S/N ratio of measurements of about 104. The rovibrational assignment of more than 920 lines was carried out, and the parameters of the spectral lines (i.e. centers, intensity and half-width) were determined by least-squares fitting of the Voigt contour parameters to the experimental data. A total of 530 rotational energy levels belonging to nine vibrational states (301), (103), (400), (221), (122), (320), (004), (023) and (042) and with maximum rotational quantum numbers J=16 and Ka=9 was determined. 101 energy levels were derived from the experiment for the first time.

Conformations of Flavan-3-ols in Water: Analysis Using Density Functional Theory.

To elucidate the conformations and their relative stabilities of flavan-3-ols in water, the optimized structures and energies were calculated by density functional theory, in which M06-2X, ωB97X-D, B3LYP, and CAM-B3LYP were examined as exchange-correlation functionals. The results were evaluated by comparing calculated spin-spin coupling constants of vicinal protons with the corresponding values observed in experimental 1H NMR spectra in D2O. The M06-2X and ωB97X-D results showed good agreement with the experimental NMR data and revealed that the B-ring (pseudoequatorial)/3-O (pseudoaxial) conformers were more stable [5.4-8.7 kJ/mol (1.3-2.1 kcal/mol)] than the B-ring (pseudoaxial)/3-O (pseudoequatorial) conformers in the 2,3-cis-flavan-3-ols, while the B-ring (pseudoequatorial)/3-O (pseudoequatorial) conformers and the B-ring (pseudoaxial)/3-O (pseudoaxial) conformers had similar stabilities in the 2,3-trans-flavan-3-ols.

Raman spectroscopic investigation on pure D2O/H2O from 303 to 573 K: interpretation and implications for water structure

D2O and H2O structure are investigated by Raman spectroscopy from 303 to 573 K at saturated vapor pressures in a fused silica capillary tube. As temperature increases to 573 K, Raman peak of D2O is blue‐shifted by 93 cm−1, lower than that of H2O by 128 cm−1, but the two Raman shoulders of D2O/H2O nearly remain unchanged in wavenumber. By fitting the spectra into five Gaussian components assigned to water molecules with different hydrogen bonding (HB) environments, these spectral features are interpreted by a mechanism that D2O and H2O have equal types of water molecules with similar HB degrees – fully hydrogen‐bonded H2O/D2O (FHW/D) and partially hydrogen‐bonded H2O/D2O (PHW/D) but distinct HB configurations that O…D–O is more symmetric and stronger than O…H–O. Much smaller values but slightly weaker temperature dependence of full widths at half maxima for D2O spectra ((FWHM)D2O) than (FWHM)H2O are primarily due to much weaker but slightly less temperature‐dependent intermolecular couplings in D2O than in H2O. Enthalpy change (ΔH) and entropy change (ΔS) on transition from FHW/D to PHW/D are determined based on Gaussian fitting. At low temperatures, a higher ΔHD2O (8.62 ± 0.06 kJ mol−1) than ΔHH2O (7.19 ± 0.05 kJ mol−1) further indicates that O…D–O is about 20% stronger than O…H–O. However, difference between O…D–O strength and O…H–O strength tends to diminish above 434 K, suggested by the rather close ΔHD2O and ΔHH2O, and same value of ΔSD2O and ΔSH2O. Copyright © 2017 John Wiley & Sons, Ltd.

ChemInform Abstract: Aluminum‐ and Gallium‐Containing Open‐Dawson Polyoxometalates.

AbstractK10 [{Al4 (μ‐OH)6}{α,α‐Si2W18 O66}]·28.5H2O (I) and K10 [{Ga4(μ‐OH)6} (α,α‐Si2W18O66)] ·25H2O (II) are prepared in 14 and 26% yield, resp., by the reaction of a 1:2 aqueous molar mixture of the trilacunary Keggin compounds Na10[A‐α‐SiW9O34] or K10[A‐α‐SiW9O34] with Al(NO3)3 or Ga(NO3)3, resp.

Aluminum‐ and Gallium‐Containing Open‐Dawson Polyoxometalates

AbstractAl‐ and Ga‐containing open‐Dawson polyoxometalates (POMs), K10[{Al4(μ‐OH)6}{α,α‐Si2W18O66}]·28.5H2O (Al4‐open) and K10[{Ga4(μ‐OH)6}(α,α‐Si2W18O66)]·25H2O (Ga4‐open) were synthesized by the reaction of trilacunary Keggin POM, [A‐α‐SiW9O34]10–, with Al(NO3)3·9H2O or Ga(NO3)3·nH2O, and unequivocally characterized by single‐crystal X‐ray analysis, 29Si and 183W NMR, and FT‐IR spectroscopy as well as elemental analysis and TG/DTA. Single‐crystal X‐ray analysis revealed that the {M4(μ‐OH)6}6+ (M = Al, Ga) clusters were included in an open pocket of the open‐Dawson polyanion, [α,α‐Si2W18O66]16–, which was constituted by the fusion of two trilacunary Keggin POMs via two W–O–W bonds. These two open‐Dawson structural POMs showed clear difference of the bite angles depending on the size of ionic radii. In cases of both compounds, the solution 29Si and 183W NMR spectra in D2O showed only one signal and five signals, respectively. These spectra were consistent with the molecular structures of Al4‐ and Ga4‐open, suggesting that these polyoxoanions were obtained as single species and maintained their molecular structures in solution.

Crosslinked triblock copolymeric micelle for redox-responsive drug delivery

In this paper, novel biodegradable amphiphilic triblock copolymer based on methoxy poly(ethylene glycol)-b-poly(ɛ-caprolactone)-b-poly(2-(2-oxo-1,3,2-dioxaphospholoyloxy)ethyl methacrylate) (mPEG-b-PCL-b-PPEMA) was successfully synthesized. After Michael-addition reactions between amine groups of cystamine and carbon–carbon double bonds of PPEMA segments, the crosslinked reduction-sensitive copolymer mPEG-b-PCL-b-PPEMA-SS- was obtained for efficient delivery and controlled release of doxorubicin (DOX) to cancer cells. Both the uncrosslinked and crosslinked copolymers could self-assemble to form nano-sized micelles in aqueous solution, while transmission electron microscopy (TEM) observation showed that the micelles dispersed in spherical shape with nano-size before and after DOX loading. Meanwhile, 1H NMR spectra in D2O indicated the formation of a lower mobility core by crosslinking method and a solid-like rigid core via further DOX-loaded. As compared to the uncrosslinked copolymer, the core crosslinking structure in mPEG-b-PCL-b-PPEMA-SS- could improve the micellar stability and enhance the drug loading capacity and entrapment efficiency. The in vitro release studies showed more sustained drug release behavior of crosslinked mPEG-b-PCL-b-PPEMA-SS- which could be accelerated quantitatively in response to the reductive condition similar to intracellular environment. Furthermore, confocal laser scanning microscopy (CLSM) indicated much more efficient cellular uptake of DOX delivered by mPEG-b-PCL-b-PPEMA-SS-, while MTT assays also demonstrated potent cytotoxic activity against HeLa cells.

Dynamic registration of D216O absorption spectrum in silica aerogel

Absorption spectra of the gas phase and adsorbed D2О in the silica aerogel with nanoscale pores were investigated in 3700–5400 cm−1 range using dynamic registration with Fourier Transform spectrometer IFS-125M. Two types of sample with pores of 60 nm wide – the nitrogen gas-treated and untreated aerogels – were examined. The surface treatment of the sample changes noticeably the broadband absorption of adsorbed water. Spectrum of D2O in the pores differs from the spectrum of bulk water as for bandwidth so for band maximum. It was found that treatment of the pores by dry nitrogen leads to increasing hydrophilic properties of the material and to change water band contour. The D2О line widths in both the aerogels exceed those of free monomer in 1.1–3 times at the same pressure. Calculations of self-broadening coefficients of the D2O lines were performed using semi-empirical method based on the impact theory of broadening and includes the correction factors. The calculated results well agree with experimental data. Greater differences were found for the shift of the line centre. The D2O line shifts in the treated pores significantly exceed line shifts in the untreated pores. For some lines, these shifts have the opposite sign indicating complex nature of the molecule–wall interaction.

Substitution of gadolinium ethylenediaminetetraacetate with phosphites: towards gadolinium deposit in nephrogenic systemic fibrosis

In neutral media, reactions of gadolinium ethylenediaminetetraacetates with phosphorous acid result in the formation of the mixed-ligand polymeric complex K3n[Gd(EDTA)(HPO3)]n·7nH2O () and dimeric complex Na6[Gd2(EDTA)2(HPO3)2]·2.5NaCl·21H2O () (H4EDTA = ethylenediaminetetraacetic acid) in warm solution. Further substitution with citric acid gives the monomeric gadolinium citrate with EDTA (NH4)2Na[Gd(EDTA)(H2cit)]·4H2O (). The compounds were characterized by elemental analysis, single crystal X-ray diffraction, FT-IR, ESI-MS and thermogravimetric analysis. Structural analysis indicates that three coordinated water molecules in the gadolinium ethylenediaminetetraacetate trihydrates are replaced by phosphite ions (HPO3(2-)) in the compounds and . Gadolinium atoms are octa-coordinated by EDTA and the phosphite ion, the latter links adjacent Gd-EDTA units to generate an infinite one-dimensional chain in compound and a dimeric octatomic ring in . In complex , coordinated water molecules were substituted by the α-hydroxy, α-carboxy and β-carboxy groups of citrate. Citrate is favourable for inhibiting the formation of Gd-EDTA phosphite. All the complexes are very easily soluble in water. The solution behavior of the isostructural lanthanum complexes was probed with (13)C and (31)P NMR spectra in D2O for comparison. ESI-MS analysis and recrystallization proved that complexes and dissociate to the monomeric unit of Gd-EDTA and free HPO3(2-) in aqueous solution. Substitutions of gadolinium ethylenediaminetetraacetates to and are attributed to be the cause of nephrogenic systemic fibrosis in some way.

Thermo- and pH-responsive copolymers based on PLGA-PEG-PLGA and poly(l-histidine): Synthesis and in vitro characterization of copolymer micelles

A series of novel thermo- and pH-responsive block copolymers of PHis-PLGA-PEG-PLGA-PHis composed of poly(ethylene glycol) (PEG), poly(d,l-lactide-co-glycolide) (PLGA) and poly(l-histidine) (PHis) were synthesized and used for the construction of stimuli-responsive copolymer micelles. The starting polymers of PLGA-PEG-PLGA and PHis were synthesized by ring-opening polymerization of dl-lactide and glycolide with PEG as an initiator and l-histidine N-carboxylanhydride with isopropylamine as an initiator, respectively. The final copolymer was obtained by the coupling reaction of PHis with PLGA-PEG-PLGA. The copolymer micelles were constructed to have an inner core consisting of two hydrophobic blocks (PLGA and deprotonated PHis) and an outer hydrophilic PEG shell. The temperature- and pH-induced structure changes of the micelles were characterized by an alteration in particle size, a decrease in pyrene florescence intensity, and a variation of 1H NMR spectra in D2O. It was speculated that the hydrophobic–hydrophilic transitions of PEG and PHis in response to temperature and pH variations accounted for the destabilization of micelles. In vitro release profiles, cell cytotoxicity and intracellular location studies further confirmed the temperature- and pH-responsive properties of the copolymer micelles. These results demonstrate the potential of the developed copolymers to be stimuli-responsive carriers for targeted delivery of anti-cancer drugs.

Deuterium NMR Investigation of the Lyotropic Phases of Alkyl β-Glycoside/D2O Systems

We have investigated the phase behavior of four glycosides (βC8OGlc, βC8SGlc, βC10OGlc, βC8OGal) in water and D2O by optical polarizing microscopy and deuterium NMR. Previously published phase diagrams were evaluated by deuterium NMR, via monitoring D2O spectra, and confirmed the presence of the hexagonal, bicontinuous cubic, and lamellar phases in these glycosides. We have also shown the presence of the gel phase in (βC10OGlc) and observed the extensive supercooling of the lamellar phase to temperatures well below the Kraft line. While the main features of the phase diagrams were confirmed, some phase boundaries were found to be slightly different. Magnetically aligned spectra were also observed for relatively dilute samples for the hexagonal phase (βC8OGlc and βC8OGal) and the lamellar phase (βC8SGlc and βC10OGlc). The average number of bound water molecules per headgroup in the lamellar phase for the glycosides was determined by the systematic measurement of the quadrupolar splitting of D2O over a wide range of values of the (glycoside/water) molar ratio. The number of water molecules bound to the headgroup was found on average to be about 1.6-1.7 water molecules with no significant differences in this value for the different glycosides (and over the temperature range investigated), indicating that the bound water content is predominately influenced by the number of hydroxyl groups of the headgroup only. However, this bound water content of only 1.6-1.7 water molecules per sugar headgroup is surprisingly low, suggesting strong intermolecular interactions of the OH groups of headgroup sugars. The results are in line with computational results reported earlier for the octyl-β-glucoside and β-galactoside, which show the presence of strong intralayer hydrogen bonding.

Experimental and theoretical studies of 1,2-di(3-hydroxypyridinium)-ethylene dibromide

The molecular structure of 1,2-di(3-hydroxypyridinium)-ethylene dibromide (1) has been characterized by single-crystal X-ray diffraction, DFT calculations, FTIR and NMR spectra. The crystals are monoclinic, space group C2/c. The bromide anions are engaged in the H⋯Br− hydrogen bonds of 2.31(4)Å, while the O⋯Br− distances are 3.094(2)Å. The dication and hydrogen-bonded bromide anions are located on the inversion center. From two optimized structures at the B3LYP/6-311++G(d,p) level of theory, one is extended (1a) similarly as in the crystals with the H⋯Br− hydrogen bonds of 1.922Å, while the other (2) is asymmetric and bent, as a result of N+⋯Br− electrostatic attractions with distances between 4.067 and 4.375Å and CH⋯Br− contacts. The FTIR spectrum of 1 is consistent with the X-ray results. Interpretation of the 1H and 13C NMR spectra in D2O has been based on 2D experiments. The calculated GIAO/B3LYP/6-311++G(d,p) magnetic isotropic shielding constants have been used to predicted 13C chemical shifts for the optimized structures of 1a and 2.

A Phase Solubility Study on the Chiral Discrimination of Ibuprofen by β-Cyclodextrin Complexes

The effects of chiral discrimination in inclusion complexes formed by native β-cyclodextrin and its substituted form (namely methyl-β-cyclodextrin) with racemate or pure enantiomers of the non-steroidal anti-inflammatory drug ibuprofen have been investigated in water. Stability constants and complexation efficiency have been determined for these host–guest systems with a 1:1 molar ratio from phase solubility profiles, showing that in aqueous solution, methylated cyclodextrin is a better complex agent than native cyclodextrin, with more enhanced effects for the (R)-enantiomer. These results have been validated using NMR technique. In particular, 1H NMR spectra in D2O show a splitting of the signals for the methyl group and the aromatic protons close to the asymmetric centre of the racemate ibuprofen included in cyclodextrin cavity.

Study of the Structure and Photochemical Decomposition of Azidoadamantanes Entrapped in α‐ and β‐Cyclodextrin

AbstractPhotolysis of 1‐azidoadamantane (1), either in its neat state or in alkane solution, yields the dimeric product 4. In contrast, amino alcohol 3 is formed as the sole product in high yield when 1 is confined within cyclodextrins (CyDs). To understand the discrepancy in product distribution caused by supramolecular encapsulation, CyD inclusion complexes (ICs) of azidoadamantanes were fully characterized. Indeed, intermolecular selectivity was influenced by reactant orientation and mobility. Both, 1‐ (1) and 2‐azidoadamantane (5) yield 1:1 ICs with β‐CyD and 1:2 ICs with α‐CyD. As inferred from 2‐D ROESY spectra in D2O, 1 is accommodated at the wider rim of β‐CyD with the azido group pointing into the cavity. However, two principal orientations of 5 inside the cavity of β‐CyD were found. Single crystal X‐ray analysis of solid 5 also demonstrates a bimodal orientation within β‐CyD. In addition, the first induced circular dichroism (ICD) study of an alkyl azide entrapped within CyD cavities is reported. From these data, it was concluded that azide 1 is bound more strongly within β‐CyD in H2O/EtOH = 8:2 at 293 K (Ka = 20240 ± 1000 M–1) than is 2‐azidoadamantane (5) (Ka = 7450 ± 400 M–1).

The hyperfine structure in the rotational spectra of D2O: Lamb-dip measurements and quantum-chemical calculations

Thirteen rotational transitions of the doubly deuterated isotopic species of water, D2 16O, have been recorded in the millimeter- and submillimeter-wave region. The Lamb-dip technique has been used to resolve the hyperfine structure due to deuterium quadrupole coupling, due to spin–rotation as well as dipolar spin–spin interactions, thus enabling the determination of the corresponding hyperfine parameters to a good accuracy. The experimental investigation has been assisted by high-level quantum-chemical calculations of the hyperfine parameters.