Spectrophotometric Characteristics of New Pyridylindolizine Derivatives Solutions

Three new pyridylindolizine derivatives, 1, 2, 3-tricarbometoxi-7-(4-pyridyl)-pyrrolo[1, 2-a]pyridine (I), 1,2-dicarboethoxy-3-(4-bromobenzoyl)-7-(4-pyridyl)-pyrrolo[1,2-a]pyridine (II) and its isomer 1,2-dicarboethoxy-3- (4-bromobenzoyl) -5- (2-pyridyl) -pyrrolo[1, 2-a]pyridine (III) have been investigated in different solutions by UV-VIS absorption, steady-state, and time-resolved fluorescence methods. The effects of the substituent and solvent on the spectroscopic properties have been demonstrated. The fluorescence decay data could be fitted to a single-exponential function. The lifetime values are higher in protic polar than in aprotic apolar solvents for compound I. In the case of compounds II and III the fluorescence intensities and lifetimes are very low, with the exception of III in aprotic solvents. The absorption and fluorescence properties of the compounds showed a solvent dependence.     

2,4,6-Triazido-1,3,5-Triazine, 2,4,6-Triazidopyrimidine,and 2,4,6-Triazidopyridine as Precursors of Carbon Nitride Materials

The thermolysis of 2,4,6-triazido-1,3,5-triazine (I), 2,4,6-triazidopyrimidine (II), and 2,4,6-triazidopyridine (III) and its products were studied by DSC, mass spectrometry, IR spectroscopy, and electron microscopy. The thermal transformations of I gave planar nets formed by polyconjugated C–N bonds arranged into bundle aggregates. The thermolysis product of III consists of low-molecular compounds and has globular morphology. The thermolysis of II resulted in a mixture of products of both types, among which the planar nets were dominant. The relationship between the structure of the products of the thermal transformations of I, II, and III and the kinetic characteristics of these processes was discussed.     

Spectroscopic and thermodynamic features of conical bubble luminescence

The influence on luminescence from conical bubble collapse (CBL) with varying Ar gas content while perturbing the liquid 1,2-Propanediol (PD) has been investigated. The temporal, spatial, and spectral features were analysed with regards to the dynamics of collapse and liquid degradation. Sulphuric acid and sodium chloride were added to disturb the liquid. The following three cases were studied: PD/Ar, (I), (PD + H₂SO₄)/Ar, (II), and (PD + H₂SO₄ + NaCl)/Ar, (III). The intensities of those cases decrease as III > II > I. Temporally, single and multiple light emissions were found to occur. The pulse shape exhibited a large variety of profiles with a main maximum and up to two local maxima around the main maximum. These local maxima resembled those generated by laser cavitation. Spatially, no radial symmetry was detected in the light emissions. Spectrally, the Swan, CH and CN lines were observed at low volumes of gas and driving pressure. The OH radical and OH-Ar bands, as well as the Na and K lines, consistently appeared superimposed on an underlying continuum that almost disappeared in (III). The Na line was observed with two satellite diffuse bands representing Na-Ar complexes in (I) and (II), whereas in (III), only the line of sodium could be seen. Weak and diffuse emission lines from the Ar atom in the near-IR region were observed in (I) and (II).The proposed mechanism of bright CBL was based on the energy transfer from electron-excited homolytic cleavage products to the chromophore molecules generated during the collapse-rebound time line (∼8200 K and ∼1 ms of collapse time from model), which had accumulated inside the liquid and remained on the walls of cavity during the repetition of the collapse. A general mechanism for the bright CBL is broached.     

Bent-shaped mesogenic oxadiazoles and thiadiazoles with terminal methyl group

Rod-shaped 4-methylbenzoic acid-N′-(4′-n-alkoxybenzoyl) hydrazide (series I) have been synthesized by the Schotten–Baumann reaction of 4-methylbenzhydrazide with 4-n-alkoxy benzoyl chloride using dry pyridine, as a solvent. The series I compounds have been cyclized to bent-shaped mesogenic 2-(4′-methylphenyl)-5-(4″-n-alkoxyphenyl)-1,3,4-oxadiazoles (series II) and 2-(4′-methylphenyl)-5-(4″-n-alkoxyphenyl)-1,3,4-thiadiazole (series III) using POCl₃ and Lawesson's reagent, respectively. The synthesized compounds are characterized by the combination of elemental analysis and standard spectroscopic methods. In series II, lower and middle members are non-mesogenic. n-Dodecyloxy to n-hexadecyloxy derivatives exhibit enantiotropic nematic mesophase. In series III, all the compounds synthesized exhibit enantiotropic nematic mesophase. n-Tetradecyloxy and n-hexadecyloxy derivatives also exhibit enantiotropic SmA mesophase. The mesomorphic properties of the series II and III used in this study are compared with each other and with other structurally related compound to evaluate the effect of different heterocyclic moieties as well as terminal substituents on mesomorphism.     

Some new four-parameter potentials and their use in the study of vibrational thermodynamical quantities of diatomic molecules

Three four-parameter potentials,U _I,U _II andU _III have been proposed and their accuracy has been demonstrated by finding the mean square deviation from the true RKR potential curve for 15 electronic states of 12 diatomic molecules. Their percentage average mean square deviations from RKR curve have been found to be 1.45, 1.86 and 2.89, respectively. These compare favourably with the value 2.67 for the recently suggested four-parameter potential of Wei Hua which itself yields better results than the commonly employed three-parameter potentials. The superiority of the new potentials (especially ofU _I andU _II has been further established by using these potentials to calculate the molecular constants α_e and ω_ex_e following Dunham’s method. The corresponding percentage average mean deviations, for α_e, turn out to be 3.75, 5.13 and 15.43 and for ω_ex_e 8.73, 17.23 and 27.49, respectively, against the respective values of 7.97 and 18.88 with Wei Hua’s four-parameter potential. Also included are the values of dissociation energy determined with these potentials and these too corroborate the better performance ofU _I andU _II. The relative worth of various potential functions has been further tested by carrying out numerical study of vibrational partition function (evaluated by sum over states method), entropy and thermal capacity for the ground state of 7 molecules and comparing these with the corresponding findings based on the RKR data.     

Magnetic susceptibility of multinary diamondlike semiconductors

Summary The magnetic susceptibility of some A^IB ₂ ^II C^IIIX ₄ ^VI (A^I=Cu, Ag; B^II=Zn, Cd; C^III=Ga, In; X^VI=Se, Te) diamondlike chalcogenides has been measured at RT. Coherently with the form of the relative A^IC^IIIX ₂ ^VI -B^IIX^VI phase diagrams, their magnetic susceptibility fulfils the sum rule typical of ideal solid solutions. Separate values of the diamagnetic and paramagnetic contributions to total magnetic susceptibility are reported and discussed according to a chemical-bond approach previously described. Paper presented at the ?V International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16, 1982.     

Novel RCo5Ga7 intermetallic compound

The novel RCo₅Ga₇ (R=Y, Tb, Dy, Ho and Er) intermetallic compounds have been synthesized, and their crystallographic and magnetic properties have been studied using X-ray diffraction and magnetic measurement. RCo₅Ga₇ crystallizes in an orthorhombic structure with ScFe₆Ga₆ type. The space group is Immm, and Z=2. According to the structural refinement result, the 2a, 4e, 4f, 4g, 4h, and 8k crystal positions are occupied by 2R, 4Ga^I, 4(Ga^II, Co^I), 4Ga^III, 4(Ga^IV,Co^II), and 8(Co^III,Ga^V), respectively. The RCo₅Ga₇ intermetallic compound can be stabilized in the range of the radius ratio of R_Re/R_(Co,Ga)<1.36. The RCo₅Ga₇ compound exhibits a paramagnetic behavior. The magnetization at 5 K ranges from 28.93 to 40.62 emu/g.     

Synthesis and EPR spectroscopy of nitroxyl derivatives of the C60 fullerene

The 2,2,5,5-tetramethyl-3-imidazoline-3-oxy-1-oxyl-4-(azidophenyl) derivatives of the C₆₀ fullerene with one (compound I), two (compound II), and three (compound III) nitroxyl groups are synthesized and studied by EPR spectroscopy. It is demonstrated that successive addition of nitroxyl radicals to C₆₀ leads to a decrease in the rotational mobility of molecules. Chromatographically inseparable isomers are found for compounds II and III.     

Fluorescence of N,N-di(2-carboxyethyl)-<Emphasis Type="Italic">p</Emphasis>-anisidine in solution and crystalline states

The fluorescence properties of N,N-di(2-carboxyethyl)-p-anisidine (I) in solvents of various nature and in the crystalline state have been studied at room temperature (273 K) and at the boiling point of liquid nitrogen (77 K). Fluorescence in aqueous solutions of I with protonated (λ _ex /λ _fl ^max = 225/290 nm) and unprotonated (λ _ex /λ _fl ^max = 270/380 nm) amino nitrogen has been detected. On going from aqueous solutions to nonaqueous, the fluorescence band of unprotonated I experiences a blue shift and its intensity rises. The fluorescence intensity of the band in aprotic polar solvents is higher than that in protic solvents. A linear dependence of the fluorescence intensity of deprotonated I on Cu(II) concentration (ranging from 1.0 to 5.0 mg/dm³) in aqueous solution has been found. The fluorescence intensity of I in aqueous solutions at 77 K and pH 1–6 has been shown to increase in the presence of Zn(II) (1–170 mg/dm³) and Cd(II) (2–330 mg/dm³) although a similar dependence is not observed at 293 K.     

Peculiarities of crystal structures and magnetic properties of Cu(II) and Ni(II) mixed-ligand complexes on the 1,3-dithiole-2-thione-4,5-dithiolate basis

Mixed-ligand Cu(II) and Ni(II) complexes, [Cu(dmit)(bpy)]₂ (I), [Ni(dmit)(phen)₂] (II) and [Ni(dmit)(phen)₂]·CH₂Cl₂ (III) (dmit=1.3-dithiole-2-thione-4.5-dithiolate, phen=1.10-phenantroline, bpy=2.2′-bipyridine) have been prepared by ligand exchange between phen or bpy and (Bu₄N)₂[M(dmit)₂] (M=Ni, Cu) and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray analysis and by investigation of magnetic and resonance properties. In complex I, the monomeric units form dimers in a head-to-tail arrangement by weak coordination bonds between copper and dithiolate sulfur atoms and π–π interactions between dmit and bpy from neighboring monomers. Dimers in I are further extended into chains by weak Cu–S(thione) contacts. In crystal packing of complex II and III, there exists a weak π–π interaction between two parallel phen molecules of the adjacent complexes. As a consequence, the magnetic and resonance characteristics of copper complex may be described in approximation of exchange-coupled pairs of Cu²⁺ ions with ion spin S=1/2. The nickel complexes are described by isotropic exchange model for single-site spin S=1.     

Internal conversion studies of the 114 keV transition in175Lu

Measurements of the conversion line intensities, the directional correlation and the conversion probability for the 114 keVM1+E2 transition in¹⁷⁵Lu are reported. TheE2 admixture, determined from relativeK andL intensities, is (19.2±0.2)%. The theoreticalL _I internal conversion coefficient is found to be about 8% too low relative theK,L _II andL _III conversion coefficients.     

X-ray energy levels: Deviations between experimental and theoretical values

Energy values ofK, L _II andL _III levels calculated by the relativistic self consistent field method have been used to compute the energies ofKα _{1, 2} lines. These values deviate considerably from the experimental values due to Bearden and Burr. The deviations are discussed and given an empirical fit.     

Synthesis and Luminescent Properties of Lanthanide Complexes with Structurally Related Novel Multipodal Ligands

To explore the relationship between the structure of the ligands and the luminescent properties of the lanthanide complexes, a series of lanthanide nitrate complexes with two novel structurally related multipodal ligands, 1,3-bis{[(2’-(2-picolylaminoformyl))phenoxyl]methyl}benzene (L ^I ) and 1,2-bis{[(2’-(2-picolylaminoformyl))phenoxyl]methyl}benzene (L ^II ), have been synthesized and characterized by elemental analysis, infrared spectra and molar conductivity measurements. At the same time, the luminescent properties of the Eu(III) and Tb(III) nitrate complexes in solid state and the Tb(III) nitrate complexes in solvents were investigated at room temperature. Under the excitation of UV light, these complexes exhibited characteristic emissions of central metal ions. The lowest triplet state energy levels T₁ of these ligands both match better to the lowest resonance energy level of Tb(III) than to Eu(III) ion. The influence of the structure of the ligands on the luminescent intensity of the complexes was also discussed.     

Inhibition and Promotion of the Oxidation Processes of Water-Soluble Cationic Co(II)-Porphyrin Under Its Interaction with Nucleic Acids

Using the methods of absorption spectroscopy and resonance Raman scattering, we have made a comparative study of water-soluble cationic Co(II)- and Co(III)-5,10,15,20-tetrakis(4-N-methyl-pyridiniumyl)porphyrins(Co^II(TMpy-P4) and Co^III(TMpy-P4) with DNA and synthetic single- and double-stranded polynucleotides. It has been found that Co^II(TMpy-P4), which in aqueous solutions containing no nucleic acids is readily oxidized to Co^III(TMpy-P4) by the molecular oxygen dissolved there, markedly changes its oxidation ability when bound to nucleic acid. Under interaction with guanine-containing polynucleotides, the rate of change in the oxidation state of cobalt from Co(II) to Co(III) increases as compared to such for the solution of porphyrin in a buffer. But in complexes with DNA and adenine- and thymine-containing polynucleotides, CoII(TMpy-P4), on the contrary, becomes stable. The observed effects of inhibition/promotion of Co^II(TMpy-P4) oxidation when it is bound to nucleic acids are assumed to be due to the weakening/strengthening of the electron-donor properties of the extraligand on cobalt, which leads to a change in cobalt affinity to molecular oxygen. The role of immobilized water molecules in the change in the properties of cobalt extraligands has been considered. On the basis of the analysis of the spectral data obtained, modes for incorporating Co^II(TMpy-P4) into DNA and model polynucleotides are proposed. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 538–545, July–August 2005.     

Kinetics and mechanism of the growth of gold nanoparticles by reduction of tetrachloroauric acid by hydrazine in Triton N-42 reverse micelles

The kinetics of the growth of gold nanoparticles during the reduction of tetrachloroauric acid by hydrazine in dispersed aqueous solution encapsulated by reverse micelles of Triton N-42 surfactant (with decane as dispersion medium) was studied by means of spectrophotometry. According to DLS data, at a set value of solubilization capacity V _s/V _o = 0.005 initial micelles have an aqueous core hydrodynamic diameter d _c = 3.6±0.2 nm. The final particles obtained after full reduction of Au^III have a metallic core of defect-free single-crystalline gold with a narrow size distribution and average core diameter d _Au = 7.7 ± 1.4 nm as shown by TEM. The rate of the particle growth is limited by the rate of gold reduction. The process kinetics corresponds to the model consisting of two stages of reduction Au^III → Au^I → Au⁰. The stages involve the formation and redox decay of the intermediate complexes Au(N₂H₄)Cl₃ and Au(N₂H₄)Cl, and each stage proceeds via two routes: (1) homogeneous in the dispersed aqueous phase, and (2) heterogeneous on the particle surfaces. Reactions taking route (2) are autocatalytic because they proceed with participation of the surface atoms of particles as the final products of Au^III reduction. The dependencies of observed rate constants on reagent concentrations, temperature, and solubilization capacity of the micellar solution are studied.     

Relative internal conversion electron intensities of the 113 keV transition in177Hf

The intensities of the internal conversion lines of the 113 keVM1 +E2 transition in¹⁷⁷Hf have been measured. From comparison with theoretical conversion coefficients the transition has been found to be (95.2 ± 0.5)%E2 corresponding to ¦δ¦=4.5 ± 0.3. The theoreticalL _I andM _I conversion coefficients used in the comparison have been increased by 5% according to the result that for pureE2 transitions in the deformed region theL _I/L _II,L _I/L _III,M _I/M _II, andM _I/M _III theoretical ratios are too low (～5%). Moreover, the present result indicates that theL _II/L _III andM _II/M _III ratios obtained from the tabulations by Hager and Seltzer and from the computer program by Pauli are too high (1–2%).     

Correlation between the electric-field effect and weak-link type in YBa2Cu3−x Oy and YBa2Cu3−x Oy /Agx high-T c superconducting ceramics

An experimental study is reported of the effect of an electric field E⩽120 MV/m and of temperature T on the critical current I _c and I-V characteristics of yttrium-based high-T _c superconducting ceramics. The materials studied were copper-deficient ceramics, YBa₂Cu_3−x O_y (D samples), and YBa₂Cu_3−x O_y/Ag_x ceramics [S samples with silver present in amounts equal to the copper deficiency (0⩽x⩽0.4)]. It has been established that in D samples at 77 K, the electric field increases I _c and reduces substantially R for I>I _c, whereas in S samples no field effect is observed. Measurements of the I _c(T) dependence near the critical temperature showed that they can be described for all samples by a relation of the type I _c =const(1−T/T _c )^α, where α≈1 for the D samples, and α≈2 for the S samples. The results obtained suggest that the electric-field effect correlates with the existence in the ceramic of SIS-type weak links at grain boundaries. Fiz. Tverd. Tela (St. Petersburg) 40, 1195–1198 (July 1998)     

Transitions de phase destructive et non destructive dans le cristal moleculaire bromo-2 naphtalene

The polymorphism of 2-bromonaphthalene has been studied by both crystallographic and energetical methods. Three crystalline forms have been characterized, respectively denoted Br_III, Br_II and Br_I. The first one is the stable form up to 319 K. At this temperature a first order phase transition occurs which breaks the single crystal and leads to a disordered structure Br_I isotypic with the naphthalene one. The Br_II form is a metastable one which appears when cooling the Br_I, form; when so formed, the Br_II phase can give again the Br_I one by annealing; so that the Br_I-Br_II transition is reversible. This second order transition extends over a large temperature range (275–319 K), it does not destroy the single crystal and corresponds to a substructural modification along the c axis of the monoclinic cell. The anomalies of the Cp curve and the variations of the principal components of the thermal expansion tensor suggest that there are two competitive temperature dependent molecular reorientations. The transition Br_II→Br_III which leads to the stable ordered form is spontaneous at room temperature, it takes place sluggishly and destroys the single crystal.Cell parameters of the Br_III form have been determined from powder data using an automatic indexing method: a = 9.578(1) Å, B = 9.601(1) Å, c = 10.303(1) Å, α = 100.79(1)°, β = 109.06(1)°, γ = 101.77(1)°. (Figure of merit M₂₀ = 86.)     

A Family of Integral Transformations and Basic Hypergeometric Series

We present a conjecture giving a family of commuting operators {I(α)|α ∈ C}, in terms of n-fold integral transformations. For the simplest case n=2, the commutativity is proved by using several summation and transformation formulas for the basic hypergeometric series.