Sensitization of Tb3+ luminescence with Ce3+ in LaOBr: Tb3+, Ce3+

Luminescence emission and uv-excitation properties of LaOBr: Tb³⁺, LaOBr: Ce³⁺, and LaOBr: Tb³⁺, Ce³⁺ phosphors were studied. The visible emission spectra of La_0.995Tb_0.005OBr consists of⁵D_3,4 →⁷F_3–6 transitions in the wavelength range of 410–630 nm. The excitation of the Tb³⁺ ion gives a broad 4f → 5d transition band at 254 nm and weaker4f → 4f transition lines above 300 nm. The uv-excitation and emission of La_0.995Ce_0.005OBr at 290, 315, 355 (excitation), and 440 nm (emission) originate from transitions between the 4f-ground state and the four crystal field components of the5d²D excited state. The sensitization of Tb³⁺ luminescence in LaOBr with Ce³⁺ at varying concentrations is described and discussed. With increasing Ce³⁺ concentration the ⁵D₃ →⁷F transitions of Tb³⁺ quench totally and the⁵D₄ →⁷F transitions begin to quench gradually. The excitation spectrum of the⁵D₄ →⁷F₅ transition of Tb³⁺ consists of four bands due to Tb³⁺ and Ce³⁺, of which the three Ce³⁺ bands increase in intensity and the Tb³⁺ band decreases as the Ce³⁺ concentration is increased.     

The production of Cr(NH3)6 from the acid catalysed hydrolysis of Cr(NH3)5(NCO)

The rate of the reaction

has been investigated at 40–65°C with [HClO₄] varying from 0.04 to 0.6 M (μ = 0.6 M, NaClO₄). The observed rate law has the form: -d[Cr(NH₃)₅(NCO)²⁺]/dt = k_obs[Cr(NH₃)₅(NCO)²⁺] where k_obs = a[H+]²{1 + b[H⁺]²} and ^?1 at 55.0°C, a = 0.36 M^?1 s^?2 and b = 6.9 × 10^?3 M^?1 s^?1. The rate of loss of Cr(NH₃)₅(NCO)²⁺ increases with increasing acidity to a limiting value (at [H⁺] ～ 0.5 M) but the yield of Cr(NH₃)₆³⁺ decreases with increasing [H⁺] and increases with increasing temperature. In the kinetic studies the maximum yield of Cr(NH₃)₆³⁺ was 35% but a synthetic procedure has been developed to give a 60% yield.     

b 1Σ+ emissions from group V-VII diatomic molecules: bo+ → X10+, X21 emissions of SbBr

Chemiluminescence studies of the reactions of microwave-discharged oxygen with SbBr₃ have led to the observation of some band sequences in the near infrared region which are attributed to b0⁺ → X₁0⁺ and b0⁺ → X₂1 transitions of SbBr. Analysis of the spectra yielded T_e values for the X₂1 and b0⁺ states of 874 ± 10 and 12756 ± 10 cm^?1, respectively, and vibrational frequencies in the X₁0⁺, X₂1 and b0⁺ states of ω′'_e(X₁, X₂) = 257 ± 10 and ω′_e(b) = 270 ± 10cm^?1.     

Computational modeling of environmental plutonyl mono-, di- and tricarbonate complexes with Ca counterions: Structures and spectra: , PuO2(CO3)2Ca, and PuO2(CO3)3Ca3

We have computed the structures, and select vibrational spectra, electron density and molecular orbital contour plots of plutonium(VI) complexes of environmental importance such as [PuO₂(CO₃)₂]²⁻ and [PuO₂(CO₃)₃]⁴⁻. We show that Ca²⁺ is efficacious in gas-phase modeling of electronic and spectroscopic properties of multiply charged plutonyl di and tricarbonate anions through complexes such as PuO₂(CO₃)₂Ca and [PuO₂(CO₃)₃Ca₃]²⁺.     

Field desorption mass spectra of [M(CO)3(η-arene)]X (MMn,Re; XBF4, PF6) salts

Field desorption mass spectra are reported for a range of [M(CO)₃(η-arene)]X (MMn or Re, XBF₄ or PF₆) salts. In most cases the spectra are simple, being dominated by molecular, [M]^+·, [M + 1]⁺, and [MCO]⁺ ions for the cationic part of their structure. However, with the π-chloroarene complexes [Mn(CO)₃(η-ClC₆H₅)]PF₆ and [Mn(CO)₃(η-1-Cl, 4-MeC₆H₄)]PF₆, facile loss of the chloro substituent and further fragmentation leads to unusually complex spectra, which include strong peaks arising from recombination of fragment species. Cluster ions are also noted in several cases, allowing identification of the anion.     

Electronic structure of Re2Cl82−

The multiple scattering Xα method has been used to calculate the ordering of both occupied and unoccupied one-electron energy states of Re₃Cl₈^2?. Single crystal polarized electronic spectra of [(n-C₄H₉)₄N]₂[Re₂Cl₈] have been measured at 5 K. Principal band maxima are observed at 14 180 (z), 30870 (xy), and 39 215 (z) cm^?1. The calculation, observed polarizations, and a comparison of band positions in Re₂Cl₈^2? and Re₂Br₈^2? suggest the following transition assignments for the former complex: 14 180 cm^?1, b_2gδ → b_1uδ*; 30 870 cm^?1, e_g → b_1uδ*; 39 215 cm^?1, e_uπ → e_gπ*.     

Theoretical investigations of Fe porphyrins. V. Low-lying electronic states of bisammineporphinatoiron(III)

Ab initio CI calculations are reported on the lowest doublet, quartet, and sextet states of [Fe^III(P)(NH₃)₂]⁺. The low-spin ground state is calculated as (d_xy² (d_π)³ with d_xy(d_π)⁴ higher by 0.15 eV. The near-ir bands at ～1 eV observed in low-spin ferriheme proteins are attributed to (π → d_π) transitions. The lowest high-spin state is ⁶A_1g, and the near-ir transitions of the high-spin ferriheme proteins observed at ～1.2 eV are attributed to higher ⁶[tripsextet] excited states [i.e., ring triplet, metal sextet]. The 30-ps “triplet” transient populated with low quantum yield observed in laser-flash studies on Fe^III(TPP)CI [TPP = tetrapbenylporphyrin] may be an ¹[tripsextet] state.     

Synthesis and Crystal Structure of Cucurbit[6]uril Adduct of Hydrogen-bonded Cluster Complex [Mo3(μ3-Se)(μ2-O)3(H2O)6Cl3]+

Reaction of [MoOCl₅]²⁻ with in situ generated H₂Se under hydrothermal conditions (4M HCl, 140 °C) leads to reduction of Mo(V) to Mo(IV) with the formation of a triangular cluster Mo₃(μ₃-Se)(μ-O)₃⁴⁺ in high yield. It is present in HCl solutions as aqua chlorocomplex [Mo₃(μ₃-Se)(μ-O)₃(H₂O)₆Cl₃]⁺ which was isolated and structurally characterized as supramolecular adduct with cucurbit[6]uril (CB[6]), {[Mo₃(μ₃-Se)(μ-O)₃(H₂O)₆Cl₃]₂CB[6]}Cl₂·15H₂O. Dedicated to Professor Dieter Fenske on the Occasion of his 65th Birthday     

b1Σ+ Emissions from group V–VII diatomic molecules. b 0+ → X1 0+, X2 1 emissions of AsI and SbI

Chemiluminescence from the b 0⁺ → X₁ 0⁺ band system of AsI and of the b 0⁺ → X₁ 0⁺, X₂ 1 systems of SbI in the near-infrared spectral region has been observed in a discharge flow system. Analysis of the spectra led to the spectroscopic constants (in cm^?1) of AsI: ω_e(X₁, X₂) = 257 ± 2, ω_ex_e(X₁, X₂) = 0.82 ± 0.2, T_e(b 0⁺) = 11738 ± 5, ω_e(b 0⁺) = 271 ± 2, ω_ex_e(b 0⁺) = 0.66 ± 0.2, and of SbI: T_e(X₂ 1) = 965 ± 10, ω_e(X₁, X₂) = 206 ± 6, T_e(b 0⁺) = 12328 ± 10, ω_e(b 0⁺) = 211 ± 6. The intensity ratio of the two sub-systems b 0⁺ → X₂ 1 and b 0⁺→ X₁ 0⁺ was found to be ≈0.013 in the case of SbI and ? 0.01 for AsI.     

Anharmonicity in rotational and vibrational excitation of H2 by Li+ collisions

Integral cross sections for pure rotational and vibrational-rotational excitation of H₂(X¹Σ⁺_g) by Li⁺(¹S) impact are computed by close-coupling methods at 0.2, 0.6, and 1.2 eV in the c.m. system using vibrational functions that are numerical solutions of the one-dimensional radial Schrödinger equation for harmonic, Morse, and adiabatically corrected Kolos-Wolniewicz (KW) potential functions. Comparison of results employing KW and Morse functions shows excellent agreement for all transitions studied. Findings using harmonic oscillator functions, however, differ noticeably from KW and Morse values for vibrational (0 → 1) and very large rotational (Δj = 10) transitions, but are satisfactory for lower order (0 → 2, 4, 6, 8) rotational transitions.     

Vibrational branching ratios for the A3Πi → X3Σ− system of OH+ and OD+

Near-thermal charge exchange between He⁺ and H₂(D₂O) is used as a source of OH⁺(OD⁺) A³H_i→ X³Σ^? emission. A comparison between experimental emission branching ratios and those calculated in the r-centroid approximation suggests that the electronic transition moment varies as a function of the r-centroid.     

He(I) and He(II) photoelectron spectra of 1-aza-1,3-butadiene-tricarbonyliron complexes: [Fe(CO)3(R1NCHCHCHR2)]

He(I) and He(II) photoelectron spectra are reported for the 1-aza-1,3-butadienes (R¹NCHCHCHR² denoted by R¹,R²-ABD) t-Bu,Me-ABD and i-Pr,Ph-ABD and their tricarbonyliron complexes [Fe(CO)₃(R¹,R²-ABD)]. Assignments of ionizations from the iron d and ligand orbitals have been made with the aid of He(I)/He(II) intensity ratios and some semi-empirical molecular orbital calculations on the model ligand Me,H-ABD (MNDO) and on the model complex [Fe(CO)₃(H,H-ABD)] (CNDO/S).A remarkable feature is the lowering of the ionization energy from the Fe d_xz/yz² orbital with respect to the other d orbitals (d_xy/d_x²–y²/d_z²)⁶ by about 0.9 eV, an effect which has not been found for the related [Fe(CO)₃(1,3-butadiene)] complexes. The involvement of the nitrogen lone pair in the bonding between the R¹,R²-ABD and Fe(CO)₃ moieties is discussed.     

Oximato bridged RhIII2MII and RhIIIMI species (MII = Mn, Co, Ni; MI = Cu, Ag)

The reaction of [RhCl₂(HPhL)(PhL)] with M^II(ClO₄)₂·6H₂O in presence of alkali has furnished trinuclear [RhCl₂(PhL)₂]₂M(H₂O)₂·H₂O (HPhL is phenylazobenzaldoxime; M = Mn, Co, Ni). A similar reaction with M^I(PPh₃)₂NO₃ yielded binuclear [RhCl₂(PhL)₂]M(PPh₃)₂ (M = Cu, Ag). In these molecules the oximato group acts as a bridge between Rh^III (bonded at N) and M^II or M^I (bonded at O). In structurally characterized [Rh^IIICl₂(PhL)₂]₂Mn(H₂O)₂.H₂O the centrosymmetric distorted octahedral MnO₆ coordination sphere is spanned by four oximato oxygen atoms and two water molecules lying in trans position. In the lattice the neighbouring molecules are held together by H₂O⋯H₂O⋯H₂O hydrogen bonds generating infinite zigzag chains. The manganese atoms lie parallel to the C-axis, the shortest Mn...Mn distance being 7.992 ?. Magnetic exchange interactions if any are small as seen in room temperature magnetic moments. The manganese system displays a strong EPR signal near g = 2.00. In the complex [RhCl₂(PhL)₂]Cu(PPh₃)₂ the copper atom is coordinated to two oximato oxygen atoms and the two phosphorus atoms in a distorted tetrahedral geometry. The softness of the phosphine ligand is believed to sustain the stable coordination of hard oximato oxygen to soft Cu^I. The coordination sphere of the RhIII atom in both the complexes is uniformly trans-RhN₄Cl₂.     

The relevancy of the [B2N4] substructure in the electronic structure of the metal-rich lanthanum nitridoborate La3(B2N4)

Lanthanoide nitridoborates of the general formula Ln₃(B₂N₄) with Ln=La, Ce, Pr, and Nd occur as black crystalline materials. Their structures contain oxalate-like [B₂N₄]⁸⁻ ions being stacked in an eclipsed formation along one crystallographic direction. Electronic structures were calculated for a molecular [B₂N₄]⁸⁻, for the [B₂N₄] partial structure, and for the complete La₃(B₂N₄) structure with the extended Hückel algorithm to analyze the bonding characteristics and to trace the necessity and properties of one surplus electron of (La³⁺)₃(B₂N₄⁸⁻)(e⁻). The HOMO of a [B₂N₄]⁸⁻ is B-B σ bonding, and the LUMO is B-B π bonding but B-N antibonding. The energy band of the solid state [B₂N₄] partial structure corresponding to the LUMO is broadened as a result of intermolecular B?B interactions between adjacent [B₂N₄] units along the stacking direction. Due to bonding interactions with La d orbitals, this band is significantly lowered in energy and occupied with one electron in the band structure of La₃(B₂N₄). This singly occupied band exhibits no band crossings but creates a semimetal-like band structure situation.     

Na-Li-[V3O8] insertion electrodes: Structures and diffusion pathways

The potential insertion-electrode compounds Na_1.2[V₃O₈] (NaV) and Na_0.7Li_0.7[V₃O₈] (NaLiV) were synthesized from mixtures of Na₂CO₃, Li₂CO₃ and V₂O₅, which were melted at 750° and subsequently cooled to room temperature. The structures of NaV and LiV contain sheets of polymerized (VO_n) polyhedra, which are topologically identical to the sheet of polymerized polyhedra in Li_1.2[V₃O₈] (LiV). Vanadium occurs in three different coordination environments: [2+3] V(1), [2+2+2] V(2) and [1+4+1] V(3). Calculated bond-valence sums indicate that V⁴⁺ occurs preferentially at the V(3) site, which agrees with the general observation that [6]-coordinated V⁴⁺ prefers [1+4+1]-rather than [2+2+2]-coordination. The M-cations Na and Li occur at three distinct sites, M(1), M(2) and M(3) between the vanadate sheets. The M(1)-site is fully occupied and has octahedral coordination. The M(2) sites are partly occupied in NaV and NaLiV, in which they occur in [4]- and [6]-coordination, respectively. Li partly occupies the M(3) site in NaLiV, in which it occurs in [3]-coordination. The M(2) and M(3) sites in NaLiV occur closer to the vanadate sheets than the M(2) sites in NaV and LiV. The shift in these cation positions is a result of the larger distance between the vanadate sheets in NaLiV than in LiV, which forces interstitial Li to move toward one of the vanadate sheets to satisfy its coordination requirements. Bond-valence maps for the interstitial cations Na and Li are presented for NaV, NaLiV and LiV. These maps are used to determine other potential cation positions in the interlayer and to map the regions of the structure where the Na and Li have their bond-valence requirements satisfied. These regions are potential pathways for Na and Li diffusion in these structures, and are used to explain chemical diffusion properties of Na and Li in the Na-Li-[V₃O₈] compounds.     

Solvothermal synthesis of three new dimeric thiogermanates (enH)4Ge2S6, [Mn(en)3]2Ge2S6 and [Ni(en)3]2Ge2S6 from germanium dioxide and sulfur powder

Three new thiogermanates (enH)₄Ge₂S₆ (1) and [M(en)₃]₂Ge₂S₆ (M=Mn (2), Ni (3); en=ethylenediamine) were synthesized using GeO₂ and S₈ as starting materials in molar ratio of 1:0.5 under solvothermal conditions. These compounds suggest that the dimeric [Ge₂S₆]⁴⁻ anion is likely to be the main germanium-containing species in en system and it also might be preferred as counter anions by the transition metal complex cations in crystallization. The cations of [Mn(en)₃]²⁺ and [Ni(en)₃]²⁺ are even better mineralizers than the protonated amine of [enH]⁺. The crystal systems of [Ge₂S₆]⁴⁻ compounds are related to entities of cations and intermolecular reactions between cations and [Ge₂S₆]⁴⁻ anions. The compounds remove ethylenediamine and H₂S molecules in multi steps when being heated under nitrogen stream.     

以[M(DETA)2)]n+(M=Cu2+, Ni2+, Co3+)为客体的MnPS3夹层化合物的合成、结构表征与磁性研究

将过渡金属配合物阳离子([M(DETA)₂]ⁿ⁺(M=Cu²⁺,Ni²⁺,Co³⁺;DETA=Diethylenetriamine,二乙烯三胺)作为客体插入层状MnPS₃层间得到了相应的3个夹层化合物。通过X-射线粉末衍射、元素分析和红外光谱对夹层化合物的结构进行了表征。结果表明,与主体MnPS₃ 0.65 nm的层间距相比较,夹层化合物(Mn_0.88PS₃[Cu(DETA)₂]_0.12)的层间距扩大了0.32 nm,由此推测客体[Cu(DETA)₂]²⁺在层间以平面四方的配位形式存在,而另2个夹层化合物(Mn_0.79PS₃[Ni(DETA)₂]_0.21和Mn_0.74PS₃[Co(DETA)₂]_0.17)的层间距扩大了0.48 nm,说明客体[(M(DETA)₂]ⁿ⁺,M=Co³⁺,Ni²⁺) 在主体层间以八面体配位形式存在。磁性测试结果表明过渡金属离子[(M(DETA)₂]ⁿ⁺(M=Cu²⁺,Co³⁺)的插入能引起主体MnPS₃的磁性在35~40 K发生由顺磁向亚铁磁性的转变并表现自发磁化,而客体[Ni(DETA)₂]²⁺却使夹层化合物的反铁磁相互作用增强,抑制了自发磁化的发生。     

Coordination chemistry of higher oxidation states. 10 [1]. Oxofluoroanions of osmium(VIII) [OsO4F2]2− and [OsO3F3]−

Trioxotrifluoroosmates(VIII) M[OsO₃F₃] (M = Cs, Rb, K) have been prepared by direct combination of OsO₃F₂ and the appropriate alkali fluoride MF. The reaction of OsO₄ with M′F (M′ = Cs, Rb) in aqueous solution produces the tetraoxodifluoroosmates(VIII) M′₂[OsO₄F₂]. On the basis of their vibrational spectra the assignment of a $\text{fac}$ (C_3v) structure to [OsO₃F₃]^? and a $\text{cis}$ (C_2v) to [OsO₄F₂]^2? is proposed. The electronic spectra of the anions have been recorded and are interpreted using the optical electronegativity concept.     

The luminescence of Pr3+ in BaY4Si5O17

The cell constants of four new monoclinic compounds BaR₄X₅O₁₇ (R = Y, Gd; X = Si, Ge) are given. The luminescence of various RE activators in the silicates is reported. Pr³⁺-activated BaY₄Si₅O₁₇ shows efficient ultraviolet 5d → 4f emission and weak 4f → 4f emission (mainly red luminescence from the ¹D₂ level). The 5d → 4f emission is ascribed to Pr³⁺ on Y sites, the 4f → 4f emission to Pr³⁺ on Ba sites. Energy transfer from Pr³⁺ to Gd³⁺ has been observed. Gd³⁺ plays an intermediate role in the energy transfer from Pr³⁺ to Sm³⁺ and to Dy³⁺ in BaGd₄Si₅O₁₇. Upon activation with Tb³⁺ the silicates show characteristic green Tb³⁺ luminescence with a quantum efficiency of 75% for ultraviolet excitation.