Generation of fullerenyl radicals and chemiluminescence in the (C<Subscript>60</Subscript>—R<Subscript>3</Subscript>Al)—O<Subscript>2</Subscript> system

Fullerenyl radicals (FR) RC₆₀ ^· and chemiluminescence (CL) are generated in the presence of O₂ in C₆₀—R₃Al (R = Et, Buⁱ) solutions in toluene (T = 298 K). The FR are formed due to the addition of the R^· radical, which is an intermediate of R₃Al autooxidation, to C₆₀. Mass spectroscopy and HPLC were used to identify Et_nC₆₀H_m (n, m = 1–6), Et_pC₆₀ (p = 2–6), and dimer EtC₆₀C₆₀Et as stable products of FR transformations. As found by ESR, the EtC₆₀ ^· radical (g = 2.0037) is also generated by photolysis of solutions obtained after interaction in the (C₆₀— R₃Al)—O₂ system. In the presence of dioxygen, the FR is not oxidized but yields complexes with O₂, which appear as broadening of the ESR signals. Chemiluminescence arising in the (C₆₀—R₃Al)—O₂ system is much brighter (I _max = 1.86·10⁸ photon s⁻¹ mL⁻¹) than the known background CL (I _max = 6.0·10⁶ photon s⁻¹ mL⁻¹) for the autooxidation of R₃Al and is localized in a longer-wavelength spectral region (λ_max = 617 and 664 nm). This CL is generated as a result of energy transfer from the primary emitter ³CH₃CHO* to the products of FR transformation: R_nC₆₀H_m, R_pC₆₀, and EtC₆₀C₆₀Et. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 205–213, February, 2007.     

Conformational Analysis,Infrared, and Fluorescence Spectra of 1-Phenyl-1,2-propandione 1-oxime and Related Tautomers: Experimental and Theoretical Study

Summary. Conformational analysis and frequency calculation were achieved for 1-phenyl-1,2-propandione 1-oxime and its four tautomers: 1-nitroso-1-phenyl-1-propen-2-ol, 1-nitroso-1-phenyl-2-propanone, 2-hydroxy-1-phenyl-propenone oxime, and 3-nitroso-3-phenyl-propen-2-ol. Calculations were carried out at the Hartree–Fock (HF), Density Functional Theory (B3LYP), and the second-order M?ller–Plesset perturbation (MP2) levels of theory using 6-31G^* and 6-311G^** basis sets. Five conformers with no imaginary vibrational frequency were obtained by free rotations around three single bonds of 1-phenyl-1,2-propandione-1-oxime: Ph–C(NOH)C(O)CH₃, PhC(NOH)–C(O)CH₃, and PhC(N–OH)C(O)CH₃. Similarly, eight structures with no imaginary vibrational frequency were encountered upon rotations around three single bonds of 1-nitroso-1-phenyl-1-propen-2-ol: Ph–C(NO)C(OH)CH₃, PhC(N–O)C(OH)CH₃, and PhC(NO)C(–OH)CH₃. In the same manner, six minima were found through rotations around three single bonds of 1-nitroso-1-phenyl-2-propanone: Ph–CH(NO)C(O)CH₃, PhCH(–NO)C(O)CH₃, and PhCH(NO)–C(O)CH₃. Also, two minima were found through rotations around four single bonds of 2-hydroxy-1-phenyl-propenone oxime: Ph–C(NOH)C(OH)CH₂, PhC(N–OH)C(OH)CH₂, PhC(NOH)–C(OH)CH₂, and Ph-C(NOH)C(–OH)CH₂. Finally, two minima were found through rotations around four single bonds of 3-nitroso-3-phenyl-propen-2-ol: Ph–CH(NO)C(OH)CH₂, PhCH(–NO)C(OH)CH₂, PhCH(NO)–C(OH)CH₂, and PhCH(NO)C(–OH)CH₂. Interconversions within the above sets of conformers were probed through scanning (one and/or two dimensional), and/or QST3 techniques. The order of the stability of global minima encountered was: 1,2-propandione-1-oxime > 1-nitroso-1-phenyl-2-propanone > 1-nitroso-1-phenyl-1-propen-2-ol > 2-hydroxy-1-phenyl-propenone oxime > 3-nitroso-3-phenyl-propen-2-ol. Hydrogen bonding appears significant in tautomers of 1-nitroso-1-phenyl-1-propen-2-ol and 2-hydroxy-1-phenyl-propenone oxime. The CIS simulated λ_max for the first excited singlet state (S₁) of 1-phenyl-1,2-propandione 1-oxime is 300.4 nm, which was comparable to its experimental λ_max of 312.0 nm. The calculated IR spectra of 1-phenyl-1,2-propandione 1-oxime and its tautomers were compared to the experimental spectra.     

Conformational Analysis, Infrared, and Fluorescence Spectra of 1-Phenyl-1,2-propandione 1-oxime and Related Tautomers: Experimental and Theoretical Study

Conformational analysis and frequency calculation were achieved for 1-phenyl-1,2-propandione 1-oxime and its four tautomers: 1-nitroso-1-phenyl-1-propen-2-ol, 1-nitroso-1-phenyl-2-propanone, 2-hydroxy-1-phenyl-propenone oxime, and 3-nitroso-3-phenyl-propen-2-ol. Calculations were carried out at the Hartree–Fock (HF), Density Functional Theory (B3LYP), and the second-order M?ller–Plesset perturbation (MP2) levels of theory using 6-31G^* and 6-311G^** basis sets. Five conformers with no imaginary vibrational frequency were obtained by free rotations around three single bonds of 1-phenyl-1,2-propandione-1-oxime: Ph–C(NOH)C(O)CH₃, PhC(NOH)–C(O)CH₃, and PhC(N–OH)C(O)CH₃. Similarly, eight structures with no imaginary vibrational frequency were encountered upon rotations around three single bonds of 1-nitroso-1-phenyl-1-propen-2-ol: Ph–C(NO)C(OH)CH₃, PhC(N–O)C(OH)CH₃, and PhC(NO)C(–OH)CH₃. In the same manner, six minima were found through rotations around three single bonds of 1-nitroso-1-phenyl-2-propanone: Ph–CH(NO)C(O)CH₃, PhCH(–NO)C(O)CH₃, and PhCH(NO)–C(O)CH₃. Also, two minima were found through rotations around four single bonds of 2-hydroxy-1-phenyl-propenone oxime: Ph–C(NOH)C(OH)CH₂, PhC(N–OH)C(OH)CH₂, PhC(NOH)–C(OH)CH₂, and Ph-C(NOH)C(–OH)CH₂. Finally, two minima were found through rotations around four single bonds of 3-nitroso-3-phenyl-propen-2-ol: Ph–CH(NO)C(OH)CH₂, PhCH(–NO)C(OH)CH₂, PhCH(NO)–C(OH)CH₂, and PhCH(NO)C(–OH)CH₂. Interconversions within the above sets of conformers were probed through scanning (one and/or two dimensional), and/or QST3 techniques. The order of the stability of global minima encountered was: 1,2-propandione-1-oxime > 1-nitroso-1-phenyl-2-propanone > 1-nitroso-1-phenyl-1-propen-2-ol > 2-hydroxy-1-phenyl-propenone oxime > 3-nitroso-3-phenyl-propen-2-ol. Hydrogen bonding appears significant in tautomers of 1-nitroso-1-phenyl-1-propen-2-ol and 2-hydroxy-1-phenyl-propenone oxime. The CIS simulated λ_max for the first excited singlet state (S₁) of 1-phenyl-1,2-propandione 1-oxime is 300.4 nm, which was comparable to its experimental λ_max of 312.0 nm. The calculated IR spectra of 1-phenyl-1,2-propandione 1-oxime and its tautomers were compared to the experimental spectra.     

Chemiluminescence in the reaction of LnI<Subscript>2</Subscript> (Ln = Dy,Nd) with water

Chemiluminescence (CL) upon the reaction of crystalline LnI₂ (Ln = Dy, Nd) with water was found. The CL emitters are the Ln³⁺* electron-excited ions (Dy³⁺*, λ_max = 470, 570 nm; Nd³⁺*, λ = 700–1200 nm) generated by the electron transfer from the Ln^II ions to the H₂O molecules. The identified reaction products are H₂, dissolved LnI₃, and insoluble LnI(OH)₂ (49–51% and 48–50% yield for DyI₂ and NdI₂, respectively). The treatment of NdI₂ with an H₂O solution in THF gives the NdI₂OH(thf)₂·3H₂O complex and hydrogen. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1890–1893, October, 2007.     

Chemiluminescence during thermolysis of the (Ph3COOCPh3)n—Ph3C· peroxide containing captured triphenylmethyl radical

Chemiluminescence (CL) in the thermolysis of (Ph₃COOCPh₃)_n—Ph₃C^· containing the triphenylmethyl radical captured during the synthesis of Gomberg's peroxide was found. Two CL emitters were identified: the triplet state of benzophenone (³Ph₂CO*) and Ph₃C^·*. Ph₃C^·* is formed due to the energy transfer from the excited ³Ph₂CO* generated in the disproportion of thermolysis intermediates, Ph₃CO^· radicals. This Ph₃C^·* luminescence is the first example of CL activation by an organic radical. Chemiluminescence during the thermolysis of Ph₃COOCPh₃ containing no Ph₃C^· is resulted from the emission of one emitter, ³Ph₂CO*. The solid-phase CL was found during the oxidation of Ph₃C^· with dioxygen after the destruction of the crystalline lattice as a result of the thermolysis of the (Ph₃COOCPh₃)_n—Ph₃C^· peroxide.     

Synthesis and crystal structure determination of Cl-substituted iridium(III) acetylacetonate

γ-Halogen-substituted iridium(III) acetylacetonates of general formula Ir(acacX)₃,where acacX = CH₃ -CO-CX-CO- CH₃,X =Br, I, were synthesized. The compounds are characterized by melting points and chemical analysis data for C, H, Br, and I. An X-ray diffraction analysis was performed for iridium(III) acetylacetonate and its y-substituted analogs, crystal data were obtained, and crystal structures were determined. The crystals are monoclinic;the structures are molecular. Crystal data: Ir(acac)3 _- IrO₆C₁₅H₂₁,a = 13.900(2), b = 16.440(3), c = 7.494(2) ?, γ =98.63(2)‡, V= 1693.2 ?³,space group P2₁/b,Z = 4, d_calc =1.92 g/cm³,sin θ/λ_max = 0.703, F_hkl = 2841, R = 0.044. Ir(acacBr)_3- IrBr₃O₆C₁₅H₁₈,a = 12.794(2), b = 15.753(2), c = 9.990(2) ? Β = 105.76(2)‡, V= 1937.6 ?³,space group P2₁/n,Z =4, d_calc =2.49 g/cm³, sinθ/λ_max = 0.702, F_hkl = 1748, R = 0.048. Ir(acacI)3- M₃O₆C₁₅H₁₈,a = 12.855(2), b = 10.136(2), c =16.338(3)?, Β = 104.6(2)‡, V=2059.8?³,space group P2₁/n, Z =4, d_calc = 2.79g/cm³, θ_max =25‡, F_hkl = 2817, R =0.032. The Ir..Ir distances were estimated to be > 7.49 ? for Ir(acac)3 and > 8.10 ? for Ir(acacBr)3 and Ir(acacl)₃.If the estimate is limited to 10 ?, the intermolecular coordination number (ICN) in the structures is 10. Translated fromZhurnal Struktumoi Khimii, Vol. 40, No. 2, pp. 331–339, March–April, 1999     

Chemiluminecsence in the oxidation of Na2C60 by the (NH4)2Ce(NO3)6 complex in THF

Chemiluminescence (_max = 790 nm) in the oxidation of fulleride Na₂C₆₀ by the (NH₄)₂Ce(NO₃)₆ complex in THF was found. The ³C₆₀* triplet of fullerene formed in the transfer of an electron from the intermediate C₆₀ ^– anion to Ce^IV was suggested to be the chemiluminescence emitter.     

Structure and photochromic and magnetic properties of 1-isopropyl-3,3,5′,6′-tetramethylspiro[indoline-2,2′-2<Emphasis Type="Italic">H</Emphasis>-pyrano[3,2-<Emphasis Type="Italic">b</Emphasis>]pyridinium] tris(oxalato)chromate(III)

Single crystals of 1-isopropyl-3,3,5′,6′-tetramethylspiro[indoline-2,2′-2H-pyrano[3,2-b]-pyridinium] tris(oxalato)chromate(III) (Sp)₃Cr(C₂O₄)₃ were prepared for the first time. The molecular and crystal structure of this salt was studied by X-ray diffraction. The crystal structure of the salt consists of the structural units [3(Sp)⁺…Cr(C₂O₄)₃ ³⁻], in which the charged pyranopyridinium moieties of the photochromic cations (Sp)+ are directed toward the oxalate groups, whereas the indoline moieties are directed into the cavities between the structural units. This structure appeared to be favorable for photochromic transformations in the crystals. Under UV irradiation of the (Sp)₃Cr(C₂O₄)₃ salt, the thermally stable closed form of spiropyran (λ_max = 370 nm) is transformed into the open form (λ_max = 574 and 603 nm). The reverse cyclization proceeds slowly in the dark (k = 1.0(2)·10⁻⁵ s⁻¹ and rapidly under visible light irradiation. The spectroscopic and photochromic properties of the oxalatochromate (Sp)₃Cr(C₂O₄)₃ are similar to those of the iodide SpI. The magnetic properties of (Sp)₃Cr(C₂O₄)₃ were studied before and after UV irradiation.     

Radiation chemical investigations on aqueous solutions of C60(OH)18

The ultraviolet-visible absorption spectrum of C₆₀(OH)₁₈ in water showed an absorption band with λ_max = 215 nm and other characteristic absorption bands of C₆₀ are not observed. The singlet-singlet and triplet-triplet absorption bands are not observed in the 400–900 nm region. It has low reactivity with e_aq⁻ and formed an absorption band with λ_max = 580 nm. The hydroxyl radicals react with a bimolecular rate constant of 2.4×10⁹ dm³ mol⁻¹ s⁻¹ and showed an absorption band at 540 nm.     

Solution ozonolysis of C<Subscript>70</Subscript>: stable products and chemiluminescence

For the first time the total and relative contents of the stable ozonolysis products of fullerene C₇₀ solutions were identified by IR spectroscopy and elemental and chemical analyses. At the 100% conversion of C₇₀ a mixture of products corresponding to the empirical formula C₇₀O_14.3H_0.21 (epoxides: polyketones: polyesters: secondary fullerene ozonides (SFOZ): acids = 1.07: 6: 6: 0.21: 1.02) is formed. The content of polyketones, polyesters, acids, and SFOZ increases during the whole ozonolysis time (1 h). The number of oxygen atoms in epoxides C₇₀O _n (n = 1–4) is lower than that in epoxides C₆₀O _n (n = 1–6) formed by the ozonolysis of fullerene C₆₀. The kinetic curve of accumulation of epoxides C₇₀O _n (n = 1–4) passes through a maximum, which is observed 0.5 min after the beginning of ozonolysis. No epoxides were identified among the products 3.5 min after the ozonolysis. The photoluminescence (PL) (λ_max = 645 and 685 nm) of fullerene polyketones in glassy EtO₂/EtOH solutions frozen at 77 K was observed. This PL is much brighter, than that of polyketones formed upon the ozonolysis of fullerenes C₆₀. For the first time the chemiluminescence (CL) was detected and studied upon the ozonolysis of C₇₀ solutions at 300 K. The CL emitters are excited states of fullerene polyketones. The CL spectrum is partially overlapped with the known CL spectrum appeared upon the ozonolysis of C₆₀ (λ_max = 685 nm) but contains the greater number of maxima (λ_max = 645 and 685 nm), which is related to a lower symmetry of the C₇₀ oxidation products.     

Kinetic, spectral and redox properties of the transients formed on one-electron reduction of 3, 3, 6, 6-tetramethyl-3, 4, 6, 7, 9-pentahydro-10-phenyl (1, 8) (2H, 5H) acridinedione in aqueous-organic mixed solvent system: A pulse radiolysis study

The phenyl substituted acridine-1,8-dione (AD) dye reacts with (CH₃)₂*COH radicals with a bimolecular rate constant of 0.6 × 10⁸ dm³ mol⁻¹ s⁻¹ in acidic aqueous-organic mixed solvent system. The transient optical absorption band (λ_max = 465 nm, ɛ = 6.8 × 10² dm³ mol⁻¹ cm⁻¹) is assigned to ADH* formed on protonation of the radical anion. In basic solutions, (CH₃)₂*COH radicals react with a bimolecular rate constant of 4.6 × 10⁸ dm³ mol⁻¹ s⁻¹ and the transient optical absorption band (λ_max = 490 nm, ɛ = 10.4 × 10³ dm³ mol⁻¹ cm⁻¹) is assigned to radical anion, AD*⁻, which has a pK_a value of 8.0. The reduction potential value of the AD/AD*⁻ couple is estimated to be between −0.99 and −1.15 V vs NHE by pulse radiolysis studies. The cyclic voltammetric studies showed the peak potential close to −1.2 V vs Ag/AgCl.     

Synthesis, characterization, photophysical and electrochemical properties of new phosphorescent dopants for OLEDs

New heteroleptic iridium(III) complexes of 2-(p-substituted-phenyl)-pyridine were synthesized and characterized. These complexes have two cyclometalated ligands (C^∧N) and a bidentate ancillary ligand (LX), that is, (C^∧N)₂Ir(LX). LX was either acetylacetonate or 5-nitro-8-hydroxy quinolate. Substitution on the p-phenyl of C^∧N ligands was used to alter the electronic properties of these complexes. The (C^∧N)₂Ir(acac) complexes show phosphorescence with good quantum yields and microsecond lifetimes and also show photoluminescence over a wide visible range (λ_max = 503-620 nm). The HOMO level and triplet energy level of these complexes were also determined. These data indicate their potential use as emitting materials for organic light emitting diodes, OLEDs.     

Synthesis and crystal structure of complex of Ce(NO<Subscript>3</Subscript>)<Subscript>3</Subscript> with N-(3-methyl-pyridin-2-yl)-formimidoyl-(3-methyl-pyridin-2-yl) hydrazone

The reaction of 3,6-di-(3-methyl-pyridin-2-yI)-s-tetrazine (DMPTZ, II) with Ce^III salt [Ce(NO₃)₃ · 6H₂O] generates a new ligand, N-(3-methyl-pyridin-2-yl)-formimidoyl-(3-methyl-pyridin-2-yl) hydrazone (L), and forms a new complex: a mononuclear complex [Ce(L)(NO₃)₂ (H₂O)₃] · NO₃ (III). Crystal data for III: space group P-1, with a = 0.7133(4) nm, b = 1.1139(2) nm, c = 1.4572(3) nm, α= 102.13(2)°, β= 99.81(3)°, γ= 91.10(3)°, Z = 2, V = 1113.6(7) nm³, μ = 2.123 mm⁻¹ and F(000) = 630. L acts as a tri-dentate chelating ligand in III. There are 10 coordination sites around Ce³⁺ of III, which are respectively occupied by seven oxygen atoms (four from two nitrate anions and three from three H₂O molecules) and three nitrogen atoms (all from L). The cerium atom and three chelating nitrogen atoms are coplanar. The mechanism of the metal assisted decomposition is discussed briefly.     

Ca9Y(PO4)7:Ce3+,Tb3+纳米荧光粉的制备及发光性能

采用水热法制备出Ca_9Y(PO4)7∶Ce~(3+),Tb~(3+)纳米荧光粉,通过XRD、SEM和荧光光谱等对样品进行了分析,研究在Ca_9Y(PO4)7基质中引入Ce~(3+),Tb~(3+)离子对发光性能的影响规律。研究发现因Tb~(3+)离子自身能量交叉驰豫的存在,使得单掺Tb~(3+)时,通过调节Tb~(3+)离子的浓度可以实现对发光颜色的控制。同时研究了Ce~(3+)-Tb~(3+)之间的能量传递为电多极相互作用的偶极-四极机制,Ce~(3+)-Tb~(3+)之间最大的能量传递效率为55.6%。Ca_9Y(PO4)7∶Ce~(3+),Tb~(3+)的发光颜色可以通过激活离子之间的能量传递和共发射得到可控调节。SEM分析表明荧光粉颗粒尺寸在100 nm左右,分散性好。     

Chemoluminescence in the oxidation of Na2S by oxygen in water solutions

Chemiluminescence was observed in the the oxidation of Na₂S by oxygen in aqueous solution. One of the luminescence emitters was identified as the triplet state (SO₂) (_max = 420 nm) generated without participation of free radicals at the first stage of oxidation of Na₂S to Na₂S₂O₃. Oxygen is a necessary reagent for CL and isa quenching agent. CL was shown to increase in the presence of Ru(bpy)₃Cl₂ as a result of the transfer of energy from (SO₂) to form Ru(bpy)₃ ²⁺, which emits at _max = 593 nm.Translated fromIzvestiya Akademii Nauk Seriya Khimicheskaya, No, 7, pp 1864–1865, July, 1996.     

Decomposition of electron-excited molecules of molybdenum and tungsten phosphine hydride and phosphine nitrogen complexes

The kinetics and mechanism of photodehydrogenation of the phosphine hydride complexes MH₄L₄ (M = Mo, W; L are phosphine ligands) and the formation of coordinatively unsaturated species M_L4 were studied by the absorbance of long-wavelength bands with λ_max at 450–460 nm appeared in the absorption spectra of the photoproducts. The rate constants of the reactions of the coordinatively unsaturated M(DPPE)₂ species (M = Mo, W; DPPE = Ph₂PCH₂CH₂PPh₂) with molecular nitrogen in benzene were determined (k _W = 200 s⁻¹, k _Mo = 8700 s⁻¹). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 282–284, February, 2008.     

Rearrangements of cyclopentadienyl cyanates,isocyanates and their thio-,seleno-, and telluro-analogs

Dynamic NMR spectroscopy revealed that pentaphenylcyclopentadienyl isoselenocyanate undergoes reversible hetero-Cope rearrangement (ΔG ^≠ _{408 K} ∼ 22 kcal mol⁻¹, C₆D₅CD₃) giving isomeric selenocyanate in which 1,5-sigmatropic shifts of the SeCN group along the perimeter of the cyclopentadiene ring occur (ΔG ^≠ _{298 K} = 16.7 kcal mol⁻¹, C₆D₅CD₃). On the contrary, pentaphenylcyclopentadienyl iso(thio)cyanates Ph₅C₅NCO and Ph₅C₅NCS are structurally rigid compounds on the NMR time scale. The energy barrier to the 3,3-shift of the isoselenocyanate group in pentaphenylcyclopentadienyl derivative Ph₅C₅NCSe (ΔG _{298 K} ^≠ = 17.9 kcal mol⁻¹) caclulated using the B3LYP/6-31G** method is 7.6 kcal mol⁻¹ lower than for the unsubstituted analog H₅C₅NCSe.     

Crystal structure and fluorescence/phosphorescence of two novel Cd(II) coordination polymers

Two novel Cd(II) coordination polymers [Cd₄(C₆H₄O₂N)₈(H₂O)₄]_n (1) and [Cd₂(C₁₀H₂O₈)(H₂O)₆]_n (2) have been synthesized under hydrothermal condition and structurally characterized. Crystal data: (1), orthorhombic, Pbca, a=11.4494(19) Å, b=12.0969(6) Å, c=17.4073(8) Å, V=2410.9(4) ų, Z=8, D _calc=2.064 g·cm⁻³; (2), triclinic, P , a=5.5962(7) Å, b=7.7758(6) Å, c=9.6975(10) Å, α=111.981(5)°, β=101.649(6)°, γ=98.240(5)°, V=371.95(7) ų, Z=2, D _calc=2.603 g·cm⁻³. Complex (1) possesses three-dimensional infinite structure, while complex (2) adopts two-dimensional layers and the layers are connected by the many types of hydrogen bonds, forming three-dimensional network. Study results of the photophysical properties show that both complexes can emit strong blue fluorescence and complex (1) also emits phosphorescence (λ ^pl _max=511 nm, τ=32 ms) in the solid state at room temperature.     

Tuning luminescent properties through solid-solution in (Ba1−xSrx)9Sc2Si6O24:Ce3+,Li+

A solid-solution of cerium-substituted alkaline earth scandium silicate phosphors, (Ba_1−xSr_x)₉Sc₂Si₆O₂₄:Ce³⁺,Li⁺ (x = 0, 0.25, 0.50, 0.75, 1), have been prepared by solid-state reaction. The structures, characterized using synchrotron X-ray powder diffraction, show the solid-solution closely follows Vegard's law. The substitution of Sr for Ba results in a decrease of the alkaline earth–oxygen bond distances by more than 0.1 Å at all three crystallographic sites, leading to changes in optical properties. The room temperature photoluminescent measurements show the structure has three excitation peaks corresponding to Ce³⁺ occupying the three independent alkaline earth sites. The emission of (Ba_1−xSr_x)₉Sc₂Si₆O₂₄:Ce³⁺,Li⁺ is red-shifted from the near-UV (λ_max = 384 nm) for x = 0 to blue (λ_max = 402 nm) for x = 1. The red-shifted photoluminescent quantum yield also increases when Sr is substituted for Ba in these compounds.     

Chemiluminescence during decomposition of 1,4-dimethylnaphthalene endoperoxide on the silica gel and alumina surface

Decomposition of 1,4-dimethylnaphthalene endoperoxide supported on the silica gel and alumina surface is accompanied by chemiluminescence (CL) in the IR and visible spectral regions. The CL emitter in the IR region is singlet oxygen. The ¹O₂ dimol contributes mainly to the emission at λ_max = 630 and 700 nm. It was shown by the IR-CL method that endoperoxide decomposition on the sorbent surface follows the first-order kinetics. The activation parameters of the process were determined. On the Al₂O₃ and silica gel surfaces a substantial acceleration of the decomposition of 1,4-dimethylnaphthalene endoperoxide is observed compared to the solution. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 199–204, February, 2007.