2b 2g Research Articles

Vanadyl ions influence on spectroscopic and dielectric properties of glass network

Melt quenching derived (in air) transparent glasses containing 30LiF 10SrO (60 − x)B 2O 3 xV 2O 5, with 0 ⩽ x ⩽ 1.0 (mol%) were investigated for physical, spectroscopic measurements, viz., optical absorption, electron spin resonance (ESR) and FTIR along with dielectric properties (dielectric constant ε′, loss tan δ, conductivity σ ac, etc.). The results were analyzed to correlate with each other in the light of local environment and oxidation states of vanadyl ion in the glass network. The observed blue shift in 3T 1g(F) → 3T 2g(F) and red shift in 2B 2g → 2E g transitions and decrease in Δ g ∥/Δ g ⊥ values up to V 8 indicates that the decrease in tetragonality of the vanadium site. The increase in area of optical absorption peak, ESR signal intensity and in the relative value of ac conductivity up to 0.8 mol% of V 2O 5 doped glasses is due to the predominant presence of V 4+ and V 3+ ions. Beyond this concentration, the redox ratio V 4+/V 5+ is found to decrease. By the gradual replacement of B 2O 3 by V 2O 5 up to 0.8 mol% the semi conducting nature of the glass network is found to increase due to increase of BO 3 structural units beyond this concentration insulating strength of glass matrix is increased.

Infrared and electronic spectroscopy of p-C 6H 4Cl 2+–L n clusters with L = Ar, N 2, H 2O, and p-C 6H 4Cl 2

Mass-selected clusters of the para-dichlorobenzene cation (p-C 6H 4Cl 2 +, pDCB +) are characterized by vibrational and electronic photodissociation spectroscopy in a molecular beam expansion. Infrared (IR) spectra of pDCB +–L n with L = Ar ( n = 1–7) and L = H 2O ( n = 1) and (pDCB) 2 +–Ar n with n ≤ 2 are recorded in the C–H stretch range in the 2B 2g ground electronic state of pDCB +. The IR spectra with L = Ar display essentially no shift as a function of the cluster size and approximate to high accuracy the hitherto unknown IR spectra of pDCB + and its (pDCB) 2 + dimer. In addition to the two IR active C–H stretch fundamentals at 3095 and 3107 cm −1, several intense combination bands are detected and assigned in the 2800–3100 cm −1 range for pDCB +. Comparison with the spectrum of neutral pDCB demonstrates structural changes upon ionization, which are consistent with the results of quantum chemical calculations performed at the B3LYP/6-311++G** level. Analysis of the photofragmentation branching ratios for pDCB +–Ar n yields a binding energy of ∼550 cm −1 for the roughly equivalent π-bonded Ar ligands. The IR spectrum of pDCB +–H 2O displays broader transitions with only minor redshifts (∼5–15 cm −1) due to the stronger intermolecular interaction. The C–H stretch spectrum is consistent with a π-bonded charge-dipole configuration. The IR spectrum of (pDCB) 2 +, as inferred from the spectrum of the Ar-tagged species, is rather different from those of pDCB + and pDCB, indicative of a charge-resonance type interaction in this homodimer cation. The electronic spectra of the B 2B 3u ← X 2B 2g transition near 500 nm are reported for pDCB +–Ar, pDCB +–N 2, and pDCB +–H 2O. Only small shifts of the electronic origin transition are observed upon complexation, indicating little change in the intermolecular interaction energy upon electronic excitation. This conclusion is also supported by the modest excitation of unresolved intermolecular modes, suggesting that also the geometry changes in these clusters are small upon B ← X excitation.

Geometric distortions of octahedral cations and tetrahedral anions in disordered [Cu(bpy) 3]CrO 4·7.5H 2O crystal – A comparative study

A novel copper(II) chromate complex of the formula [Cu(bpy) 3][CrO 4]·7.5H 2O ( 1) (bpy = 2,2′-bipyridine) was prepared in the crystalline form and characterized by X-ray diffraction and spectroscopic methods (EPR, FIR-IR, NIR–Vis–UV). Two non-equivalent [Cu(bpy) 3] 2+ groups in the form of tetragonally elongated octahedron are built into the hydrogen-bonded network. The tetragonality parameter T is 0.9830 and 0.9876 for Cu(1) and Cu(2) centers, respectively, points to the significant Jahn–Teller (JT) distortion in the tris-bipyridine copper(II) cations. The EPR parameters g 1, g 2 and g 3 are equal to 2.168, 2.159 and 2.072, respectively, correspond to the Cu–N bond directions oscillating between long and short distances. The chromate moiety is a non-coordinated to the metal center and forms a very distorted tetrahedron with three bond lengths in the range 1.617(2)–1.629(2) Å. The O(3A) and O(3B) atoms execute reorientational motion between two equilibrium arrangements with equal probability. The related geometric distortion, Δ r, is 0.097 Å. The Gaussian analysis of single crystal electronic spectra was based on the four d– d bands assigned for Cu(II) center to the 2A 1g(dx2−y2) → 2A 2g(dz2), 2B 1g(dxy), 2B 2g(dxz) and 2B 3g(dyz) transitions in D 2h symmetry.

Synthesis and spectroscopy of tetraborate glasses doped with copper

Lithium and potassium–lithium tetraborate glasses doped with Cu (Li 2B 4O 7:Cu and KLiB 4O 7:Cu) of high optical quality were obtained from polycrystalline compounds by fast cooling of the corresponding melt. Cu impurity was added to the Li 2B 4O 7 and KLiB 4O 7 compounds in the form of a CuO oxide in the amounts of 0.4 and 1.6 mol.%. On the basis of EPR and optical spectroscopy (absorption, emission and luminescence excitation and kinetics) data analysis it was shown that the Cu impurity was incorporated into the tetraborate glass network as Cu 2+ (3d 9) and Cu + (3d 10) ions. The EPR spectra of Cu 2+ centers were almost identical in glasses with the Li 2B 4O 7:Cu and KLiB 4O 7:Cu compositions and were characteristic for glassy compounds. The Cu 2+ EPR spectra parameters ( g-values, hyperfine constants and peak-to-peak linewidths) in the Li 2B 4O 7:Cu and KLiB 4O 7:Cu glasses were obtained at T = 300 K. The characteristic broad absorption band peaked near 750 nm was assigned to the 2B 1g → 2B 2g transition of the Cu 2+ centers. An intense absorption in the UV region ( λ < 350 nm) was related to the Cu 2 + → O 2− charge-transfer band. Broad emission bands with the maxima near 420 and 465 nm were observed in the luminescence spectra of the Li 2B 4O 7:Cu and KLiB 4O 7:Cu glasses. The emission bands, peaked near 420 and 465 nm, were characterized by single exponential decay with lifetimes τ = 23 and 27 μs, respectively for the Li 2B 4O 7:Cu and KLiB 4O 7:Cu glasses (Cu content—1.6 mol.%) at T = 300 K. Both emission bands belonged to the Cu + centers with different local environments or their distortion. A possible local structure for two types of Cu + centers in a tetraborate glass network is discussed.

A Convenient Synthesis of 2,3‐Dihydro‐3‐methylidene‐1H‐isoindol‐1‐ones by Reaction of 2‐Formylbenzo­nitriles with Dimethyloxosulfonium Methylide

AbstractA facile method for the synthesis of 2,3‐dihydro‐3‐methylidene‐1H‐isoindol‐1‐one and its derivatives carrying substituent(s) at C(5) and/or C(6) has been developed. The reaction of 2‐formylbenzonitrile (1a) with dimethyloxosulfonium methylide, generated by the treatment of trimethylsulfoxonium iodide with NaH in DMSO/THF at 0°, resulted in the formation of 2,3‐dihydro‐3‐methylidene‐1H‐isoindol‐1‐one (2a) in 77% yield. Similarly, six 2‐formylbenzonitriles carrying substituent(s) at C(4) and/or C(5), i.e., 1b–1g, also gave the corresponding expected products 2b–2g in comparable yields.

Structure of selected basic copper(II) sulphate minerals based upon spectroscopy – Implications for hydrogen bonding

The application of near-infrared and infrared spectroscopy has been used for identification and distinction of basic Cu-sulphates that include devilline, chalcoalumite and caledonite. Near-infrared spectra of copper sulphate minerals confirm copper in divalent state. Jahn–Teller effect is more significant in chalcoalumite where 2B 1g → 2B 2g transition band shows a larger splitting (490 cm −1) confirming more distorted octahedral coordination of Cu 2+ ion. One symmetrical band at 5145 cm −1 with shoulder band 5715 cm −1 result from the absorbed molecular water in the copper complexes are the combinations of OH vibrations of H 2O. One sharp band at around 3400 cm −1 in IR common to the three complexes is evidenced by Cu OH vibrations. The strong absorptions observed at 1685 and 1620 cm −1 for water bending modes in two species confirm strong hydrogen bonding in devilline and chalcoalumite. The multiple bands in ν 3 and ν 4(SO 4) 2− stretching regions are attributed to the reduction of symmetry to the sulphate ion from T d to C 2V. Chalcoalumite, the excellent IR absorber over the range 3800–500 cm −1 is treated as most efficient heat insulator among the Cu–sulphate complexes.

Spectroscopy of selected copper group minerals: Chalcophyllite and chenevixite-implications for hydrogen bonding

NIR and IR spectroscopy has been applied for detection of chemical species and the nature of hydrogen bonding in arsenate complexes. The structure and spectral properties of copper(II) arsenate minerals: chalcophyllite and chenevixite are compared with copper(II) sulphate minerals: devilline, chalcoalumite and caledonite. Split NIR bands in the electronic spectrum of two ranges 11,700–8500 cm −1 and 8500–7200 m −1 confirm distortion of octahedral symmetry for Cu(II) in the arsenate complexes. The observed bands with maxima at 9860 and 7750 cm −1 are assigned to Cu(II) transitions 2B 1g → 2B 2g and 2B 1g → 2A 1g. Overlapping bands in the NIR region 4500–4000 cm −1 is the effect of multi-anions OH −, (AsO 4) 3− and (SO 4) 2−. The observation of broad and diffuse bands in the range 3700–2900 cm −1 confirms strong hydrogen bonding in chalcophyllite relative to chenevixite. The position of the water bending vibrations indicates the water is strongly hydrogen bonded in the mineral structure. The strong absorption feature centred at 1644 cm −1 in chalcophyllite indicates water is strongly hydrogen bonded in the mineral structure. The H 2O-bending vibrations shift to low wavenumbers in chenevixite and an additional band observed at 1390 cm −1 is related to carbonate impurity. The characterisation of IR spectra by ν 3 antisymmetric stretching vibrations of (SO 4) 2− and (AsO 4) 3 ions near 1100 and 800 cm −1 respectively is the result of isomorphic substitution for arsenate by sulphate in both the minerals of chalcophyllite and chenevixite.

Spectroscopy and structural state of V 4+ ions in lithium aluminosilicate glass and glass–ceramics

The optical property of LAS glass and the structural states of V 4+ ions were studied by use of kinds of spectra (UV–visible, IR, Raman and EPR) in LAS glass and glass–ceramics containing V 2O 5. It was found that the V 4+ ions formed by reduction of V 5+ ions, and existed as the VO 2+ complex in octahedral coordination with a tetragonal compression with C 4v symmetry in LAS glass. Additionally, the V 4+ ions partially replaced Li + and occupied tetrahedral sites in beta-quartz solid solution crystal phase. The color of the glasses drastically changed from light yellow-green to claret during crystallization, and the optical absorption in visible range attribute to the transitions of 2B 2g → 2B 1g and 2B 2g → 2E g of V 4+ ions in high crystal field, which was affected by the above structural variation of V 4+. Moreover, the addition of V 2O 5 in LAS glass decreased crystallization temperature of main beta-quartz solid solution crystal phase.

Oligonucleotides Containing 7‐Deaza‐2′‐deoxyinosine as Universal Nucleoside: Synthesis of 7‐Halogenated and 7‐Alkynylated Derivatives, Ambiguous Base Pairing, and Dye Functionalization by the Alkyne–Azide ‘Click’ Reaction

AbstractOligonucleotides containing 7‐deaza‐2′‐deoxyinosine derivatives bearing 7‐halogen substituents or 7‐alkynyl groups were prepared. For this, the phosphoramidites 2b–2g containing 7‐substituted 7‐deaza‐2′‐deoxyinosine analogues 1b–1g were synthesized (Scheme 2). Hybridization experiments with modified oligonucleotides demonstrate that all 2′‐deoxyinosine derivatives show ambiguous base pairing, as 2′‐deoxyinosine does. The duplex stability decreases in the order Cd&gt;Ad&gt;Td&gt;Gd when 2b–2g pair with these canonical nucleosides (Table 6). The self‐complementary duplexes 5′‐d(F7c7I‐C)6, d(Br7c7I‐C)6, and d(I7c7I‐C)6 are more stable than the parent duplex d(c7I‐C)6 (Table 7). An oligonucleotide containing the octa‐1,7‐diyn‐1‐yl derivative 1g, i.e., 27, was functionalized with the nonfluorescent 3‐azido‐7‐hydroxycoumarin (28) by the Huisgen–Sharpless–Meldal cycloaddition ‘click’ reaction to afford the highly fluorescent oligonucleotide conjugate 29 (Scheme 3). Consequently, oligonucleotides incorporating the derivative 1g bearing a terminal CC bond show a number of favorable properties: i) it is possible to activate them by labeling with reporter molecules employing the ‘click’ chemistry. ii) Space demanding residues introduced in the 7‐position of the 7‐deazapurine base does not interfere with duplex structure and stability (Table 8). iii) The ambiguous pairing character of the nucleobase makes them universal probes for numerous applications in oligonucleotide chemistry, molecular biology, and nanobiotechnology.

Complex α‐Pyrones Synthesized by a Gold‐Catalyzed Coupling Reaction

Complex α‐Pyrones Synthesized by a Gold‐Catalyzed Coupling Reaction

CASPT2 study on the low-lying electronic states of the [formula omitted] and [formula omitted] ions

Geometries and energy levels for the five lowest-lying states of the p - C 6 H 4 F 2 + ion and of the p - C 6 H 4 Cl 2 + ion were calculated by using the CASPT2 and CASSCF methods in conjunction with a contracted atomic natural orbital (ANO-L) basis set. For the 1 2B 3g state of p - C 6 H 4 F 2 + the D 2h geometry was found not to correspond to an energy minimum, and one should consider 1 2B 3 as the second excited state of the ion which has a nonplanar D 2 minimum-energy structure. Based on our CASPT2 adiabatic excitation energy ( T 0) calculations, we assign the X, A, B, C, and D states of p - C 6 H 4 F 2 + to 1 2B 2g, 1 2B 1g, 1 2B 3, 1 2B 3u, and 1 2B 2u, respectively, and the X, A, B, C, and D states of p - C 6 H 4 Cl 2 + to 1 2B 2g, 1 2B 1g, 1 2B 3u, 1 2B 2u, and 1 2B 3g, respectively. The CASPT2 T 0 values and CASPT2 T v ′ (relative energy at the molecular geometries) values are in reasonable agreement with the available experimental data evaluated using adiabatic and vertical ionization potentials. The potential energy curves (PECs) for F-loss dissociation from the five states of the p - C 6 H 4 F 2 + ion and for Cl-loss dissociation from the five states of the p - C 6 H 4 Cl 2 + ion were calculated at the CASPT2//CASSCF level. The CASPT2//CASSCF PECs indicate that the 1 2B 2g, 1 2B 1g, and 1 2B 3u states of the p - C 6 H 4 F 2 + and p - C 6 H 4 Cl 2 + ions correlate with the X 1A 1, 1 3B 1, and 1 1B 1 states of the C 6H 4F + and C 6H 4Cl + ions, respectively. In the case of p - C 6 H 4 F 2 + the 1 2B 3g state correlates to the 1 1A 1 state of the C 6H 4F + ion and the 1 2B 2u state to 1 3A 2, while in the case of p - C 6 H 4 Cl 2 + the 1 2B 2u state correlates to the 1 1A 1 state of the C 6H 4Cl + ion and the 1 2B 3g state to 1 3A 2. There are energy barriers along the 1 2B 1 (1 2B 2g), 1 2A 2 (1 2B 1g), 2 2B 1 (1 2B 3u), and 2 2B 2 (1 2B 2u) PECs of the p - C 6 H 4 F 2 + ion and the 1 2A 2 (1 2B 1g) and 2 2B 2 (1 2B 3g) PECs of the p - C 6 H 4 Cl 2 + ion.

EPR and optical absorption studies of VO 2+ ions in alkaline earth aluminoborate glasses

Electron paramagnetic resonance (EPR) and optical absorption studies have been carried out for VO 2+ ions in calcium aluminoborate glasses. The EPR spectra of all the glass samples exhibit resonance signals, characteristic of VO 2+ ions. The values of spin-Hamiltonian parameters indicate that the VO 2+ ions in calcium aluminoborate glasses were present in octahedral co-ordination with a tetragonal compression and belong to C 4v symmetry. The number of spins ( N) participating in resonance was calculated as a function of concentration as well as temperature. It is observed that variation of N with temperature obeys the Boltzmann law. From the EPR data, the paramagnetic susceptibility ( χ) is calculated at various temperatures and the Curie constant ( C) was evaluated from the 1/ χ– T graph. The Fermi contact interaction parameter ( k), dipolar hyperfine coupling parameter ( P) have been calculated and these values are found to be independent of V 2O 5 content and temperature. The optical absorption spectrum exhibits two bands corresponding to the d–d transition 2B 2g → 2E g and 2B 2g → 2A 1g in the order of increasing energy. The theoretical values of optical basicity ( Λ th) of the glasses have also been evaluated.

Electron paramagnetic resonance and optical absorption studies of Cu 2+ ion doped polyvinyl alcohol films

Electron paramagnetic resonance (EPR) and optical absorption studies have been carried out on Cu 2+ ions doped in polyvinyl alcohol films (PVA). EPR spectrum at room temperature exhibits hyperfine structure characteristic of Cu 2+ ions in tetragonal symmetry. The EPR spectra have also been recorded at various temperatures. The number of spins participating in the resonance is measured as a function of temperature and the activation energy is calculated. The paramagnetic susceptibility ( χ) is calculated from the EPR data at various temperatures and the Curie constant is evaluated from 1/ χ versus T graph. The optical absorption spectrum exhibits a broad band which has been assigned to the transition 2B 1g → 2B 2g.

Optical characterization of Cu 2+ ion-doped zinc lead borate glasses

We have developed a new series of zinc lead borate (ZLB) glasses by varying ZnO content, to enhance UV transmission, in the chemical composition of xZnO–15PbO–(85− x)B 2O 3, where x = 0 , 5, 10, 15, 20, 25, 30, 35, 40 and 45 mol% ZnO. From the measurement of UV absorption spectra both the direct and indirect band gaps have been evaluated. Also different physical properties of a reference glass of 45ZnO–15PbO–40B 2O 3 have been studied. From the measurement of refractive indices at six different wavelengths, Cauchy's constants ( A = 1.578743209 ; B = 131832.33 nm 2 and C = - 0.77756 × 1 0 10 nm 4 ) have been computed and a satisfactory correlation has been achieved between the theoretical and the experimental results. Absorption spectra of Cu 2+(45− x)ZnO–15PbO–40B 2O 3 (where x=0.1, 0.2, 0.5 and 1.0 mol%) have shown two absorption bands at 428 nm ( 2B 1g→ 2E g) and 777 nm ( 2B 1g→ 2B 2g). Emission spectra of (1.0 mol%) Cu 2+:ZLB have revealed two emission transitions at 400 and 493 nm with excitations at 288 and 316 nm.

EPR and optical absorption studies of Cu 2+ ions in alkaline earth alumino borate glasses

Electron paramagnetic resonance (EPR) and optical absorption spectra of Cu 2+ ions in alkaline earth alumino borate glasses doped with different concentrations of CuO have been studied. The EPR spectra of all the glasses exhibit the resonance signals, characteristic of Cu 2+ ions present in axially elongated octahedral sites. The number of spins participating in the resonance has been calculated as a function of temperature for calcium alumino borate (CaAB) glass doped with 0.1 mol% of CuO. From the EPR data, the paramagnetic susceptibility ( χ) was calculated at different temperatures ( T) and from the 1/ χ– T graph, the Curie temperature of the glass has been evaluated. The optical absorption spectra of all the glasses show a single broad band, which has been assigned to the 2B 1g → 2B 2g transition of the Cu 2+ ions. The variation in the intensity of optical absorption with the ionic radius of the alkaline earth ion has been explained based on the Coulombic forces. By correlating the EPR and optical absorption spectral data, the nature of the in-plane σ bonding between Cu 2+ ion and the ligands is estimated. From the fundamental ultraviolet absorption edges of the glasses, the optical energy gap ( E opt) and the Urbach energy (Δ E) are evaluated. The variation in E opt and Δ E is explained based on the number of defect centers in the glass.

Spectral analysis of Cu 2+: B 2O 3–ZnO–PbO glasses

A new series of heavy metal oxide (PbO) based zinc borate glasses in the chemical composition of (95 − x)B 2O 3–5ZnO– xPbO ( x = 10, 15, 20, 25, 30, 35, 40, 45 and 50 mol%) have been prepared to verify their UV filtering performance. Both direct and indirect optical band gaps ( E opt) have been evaluated for these glasses. For a reference glass of 45B 2O 3–5ZnO–50PbO, refractive indices at different wavelengths are measured and found the results satisfactorily correlated with the theoretical data upon the computation of Cauchy's constants of A = 1.766029949, B = 159531.024 nm 2 and C = −1.078 × 10 10 nm 4. Measurements concerning X-ray diffraction (XRD), FT-IR, differential scanning colorimeter (DSC) profiles have been carried out for this glass. The FT-IR profile has revealed that the glass has both BO 3 and BO 4 units. From DSC thermogram, glass transition temperature ( T g), crystallization temperature ( T c) and melting temperature ( T m) have been located and from them, other related parameters of the glass have also been calculated. Visible absorption spectra of 45B 2O 3–5ZnO–(50 − x)PbO– xCuO ( x = 0. 1, 0.2, 0.5 and 1.0 mol%) have revealed two absorption bands at around 400 nm ( 2B 1g → 2E g) and 780 nm ( 2B 1g → 2B 2g) of Cu 2+ ions, respectively. Emission bands at 422 and 512 nm are found for the 1 mol% CuO doped glass with excitations at 306 and 332 nm.

Density functional theory investigation of S 2− in KCl: evidence for the existence of a di-vacancy site

Electron paramagnetic resonance experiments have shown that, depending on the doping procedure, two different S 2 − centers may coexist in KCl. These centers have the 2B 2g ( g x [ 1 ¯ 10 ] < g y [ 001 ] ) and the 2B 3g ( g x [ 1 ¯ 10 ] > g y [ 001 ] ) ground state, respectively. As no experimental ligand hyperfine data are available, it could not be determined whether the S 2 − molecular ion replaces a single halide ion (mono-vacancy site) or two nearest neighbor halide ions (di-vacancy site). Also, other defect models could a priory be considered. In this work, cluster in vacuo density functional theory calculations of the g and 33S hyperfine tensors show that the S 2 − ion at a mono-vacancy site has the 2B 2g ground state, whereas S 2 − in a di-vacancy exhibits a 2B 3g ground state. For the latter center, the possibility of charge compensation by a cation vacancy is also considered. The calculations indicate that a possible vacancy is not in the direct vicinity (nearest or next-nearest neighbor) of the S 2 − ion.

EPR and optical absorption spectral studies of Cu 2+ ions doped in alkali lead tetraborate glasses

Electron paramagnetic resonance and optical absorption spectra of Cu 2+ ions in 90R 2B 4O 7+(10− x) PbO + xCuO (where R=Li, Na and K; 0.25 ⩽ x ⩽ 1.5 mol% of CuO) glasses have been studied. EPR spectra of all glasses show resonance peaks characteristic of Cu 2+ ions. From the observed EPR spectra, the spin-Hamiltonian parameters have been evaluated. The values of spin-Hamiltonian parameters indicate that Cu 2+ ions in alkali lead tetraborate glasses have octahedral coordination with a strong tetragonal distortion. The number of spins participating in resonance is measured as a function of temperature and the activation energy is calculated. The paramagnetic susceptibility is also calculated from the EPR data at various temperatures. From the plot of temperature versus 1/ χ, the Curie constant and the Curie temperature values have been evaluated. The optical absorption spectra of all the glass samples show two bands. One broad band at low-energy side is assigned to 2B 1g→ 2B 2g transition of Cu 2+ ion and the intense band at high-energy side is assigned to charge transfer band. By correlating EPR and optical absorption data, the molecular orbital coefficients have been evaluated.

Glycosylidene Carbenes. Part 32

AbstractAcylation and sulfonylation of the N,N′‐unsubstituted glucosylidenespirodiaziridines 1A/1B 95 : 5 with Ac2O, BzCl, FmocCl, TsCl, (naphthalen‐2‐yl)sulfonyl, and (2,4,6‐triisopropylphenyl)sulfonyl chloride, and concomitant rearrangement gave the acylated and sulfonylated gluconolactone hydrazones 2B–2G in 40–83% yield (Scheme 2). Similarly, the galacto and manno analogues 3A/3B 95 : 5 and 5A/5B 55 : 45 and the mannofuransoylidene‐diaziridine 30 were acetylated and tosylated to give 4A, 4B, 6, 31A, and 31B (55–73% yield; Schemes 2 and 5). 15N‐Labelling of 11A/11B and 14A/14B showed that the pseudoequatorial NH of the gluco diaziridines 1 and the pseudoaxial NH of the galacto diaziridines 3 were preferentially acetylated and tosylated (Scheme 3). Sulfonylation of the N‐methylated diaziridines 19A/19B 72 : 28, 22A/22B 85 : 15, 25A/25B 85 : 15, 28A/28B 80 : 20, and 33A/33B/33C/33D 76 : 4 : 12 : 8 yielded the N‐methyl‐N‐tosylglyconolactone hydrazones 20, 23, 26, 29, and 34 (44–66%; Schemes 4 and 5). The methylated N‐atom of the diaziridines proved more reactive, irrespective of the configuration at C(2) and C(4). The products were readily hydrolysed to glyconolactones.

EPR and optical absorption of Cu 2+ ions in ternary K 2SO 4–Na 2SO 4–ZnSO 4 glasses

Electron Paramagnetic Resonance (EPR) and optical absorption spectra of Cu 2+ ions in K 2SO 4–Na 2SO 4–ZnSO 4 glasses have been studied. EPR spectrum of the glasses doped with Cu 2+ ions exhibits a pronounced peak at g=2.05 and a broad quadruplet with low signal intensity at g=2.39; the latter arising from the hyperfine splitting of g ∥. The temperature dependence of the glasses doped with Cu 2+ ions has also been studied. The optical absorption spectrum of the glasses doped with Cu 2+ ions shows a single broad absorption band in the near-infrared region, which is attributed to 2B 1g→ 2B 2g transition. By correlating the EPR and optical spectral data, the molecular orbital coefficient β 2 1 for Cu 2+ ions has been evaluated.