Reflection and transmission of plane waves at the interface of an elastic half-space and a fractional order thermoelastic half-space

The problem of reflection and transmission due to longitudinal and transverse waves incident obliquely at a plane interface between uniform elastic solid half-space and fractional order thermoelastic solid half-space has been studied. It is found that the amplitude ratios of various reflected and refracted waves are functions of angle of incidence and frequency of incident wave and are influenced by the fractional order thermoelastic properties of media. The expressions of amplitude ratios and energy ratios have been computed numerically for a particular model. The variation of amplitude and energy ratios with angle of incidence is shown graphically. The conservation of energy at the interface is verified.     

Catalytic dehydrocoupling of thienyl/furyl-substituted carbosilanes – Synthesis and characterization of functional poly(hydrosilane)s [RMe2Si(CH2)xSiH]n, (R = 2-Th, 4-Me-2-Th, 2-Fu, 5-Me-2-Fu; x = 2 and 3)

The carbosilanes RMe₂Si(CH₂)_xSiH₃, [R = 2-Th (1a, 2a), 4-Me-2-Th (3a, 4a), 2-Fu (5a, 6a), 5-Me-2-Fu (7a, 8a); x = 2 and 3], with primary SiH₃ end groups undergo a facile dehydropolymerization under ambient conditions (50 °C, 48 h) in presence of Cp₂TiCl₂/2.2 n-BuLi catalyst to afford the corresponding poly(hydrosilane)s 1–8 bearing carbosilyl side chains appended with thienyl/furyl groups. These have been characterized by GPC, IR, multinuclear (¹H, ¹³C{¹H}, ²⁹Si{¹H}) NMR, UV and PL spectral studies.     

Intruder configurations in the A=33 isobars: 33Mg and 33Al

The beta decay of 33Mg (N=21) presented in this Letter reveals intruder configurations in both the parent and the daughter nucleus. The lowest excited states in the N=20 daughter nucleus, 33Al, are found to have nearly 2p-2h intruder configuration, thus extending the "island of inversion" beyond Mg. The allowed direct beta-decay branch to the 5/2{+} ground state of the daughter nucleus 33Al implies positive parity for the ground state of the parent 33Mg, contrary to an earlier suggestion of negative parity from a g-factor measurement. An admixture of 1p-1h and 3p-3h configurations is proposed for the ground state of 33Mg to explain all of the experimental observables.     

Preparation of Cu, Ag, Fe and Al nanoparticles by the exploding wire technique

We describe a novel process for the production of nanoparticles of Cu, Ag, Fe and Al which involves exploding their respective wires, triggered by large current densities in the wires. The particles are characterised by X-ray diffraction (XRD) and atomic force microscopy (AFM). Particle sizes in the range 20–100nm were obtained employing this technique. The XRD results reveal that the nanoparticles continue to retain lattice periodicity at reduced particle sizes, displaying in some cases evidence of lattice strain and preferential orientation. In the case of Fe, Mossbauer spectroscopy reveals loss of ferromagnetism as a result of the reduced size of the particles. Dedicated to Professor C N R Rao on his 70th birthday     

Enthalpies of formation of gas-phase N3, N3-, N5+, and N5- from Ab initio molecular orbital theory, stability predictions for N5(+)N3(-) and N5(+)N5(-), and experimental evidence for the instability of N5(+)N3(-)

Ab initio molecular orbital theory has been used to calculate accurate enthalpies of formation and adiabatic electron affinities or ionization potentials for N3, N3-, N5+, and N5- from total atomization energies. The calculated heats of formation of the gas-phase molecules/ions at 0 K are DeltaHf(N3(2Pi)) = 109.2, DeltaHf(N3-(1sigma+)) = 47.4, DeltaHf(N5-(1A1')) = 62.3, and DeltaHf(N5+(1A1)) = 353.3 kcal/mol with an estimated error bar of +/-1 kcal/mol. For comparison purposes, the error in the calculated bond energy for N2 is 0.72 kcal/mol. Born-Haber cycle calculations, using estimated lattice energies and the adiabatic ionization potentials of the anions and electron affinities of the cations, enable reliable stability predictions for the hypothetical N5(+)N3(-) and N5(+)N5(-) salts. The calculations show that neither salt can be stabilized and that both should decompose spontaneously into N3 radicals and N2. This conclusion was experimentally confirmed for the N5(+)N3(-) salt by low-temperature metathetical reactions between N5SbF6 and alkali metal azides in different solvents, resulting in violent reactions with spontaneous nitrogen evolution. It is emphasized that one needs to use adiabatic ionization potentials and electron affinities instead of vertical potentials and affinities for salt stability predictions when the formed radicals are not vibrationally stable. This is the case for the N5 radicals where the energy difference between vertical and adiabatic potentials amounts to about 100 kcal/mol per N5.     

Polynitrogen chemistry: preparation and characterization of (N5)2SnF6, N5SnF5, and N5B(CF3)4

Metathetical processes were used to convert N5SbF6 into N5[B(CF3)4] and (N5)2SnF6. The latter salt is especially noteworthy because it contains two N5+ ions per anion, thus demonstrating that salts with touching polynitrogen cations can be prepared. This constitutes an important milestone towards our ultimate goal of synthesizing a stable, ionic nitrogen allotrope. The stepwise decomposition of (N5)2SnF6 yielded N5SnF5. Multinuclear NMR spectra show that in HF the SnF5- ion exists as a mixture of Sn2F(10)(2-) and Sn4F(20)(4-) ions. Attempts to isolate FN5 from the thermolysis of (N5)2SnF6 were unsuccessful, yielding only the expected decomposition products, FN3, N2, trans-N2F2, NF3, and N2.     

Methyl Tin(IV) derivatives of HOTeF(5) and HN(SO(2)CF(3))(2): a solution multinuclear NMR study and the X-ray crystal structures of (CH(3))(2)SnCl(OTeF(5)) and [(CH(3))(3)Sn(H(2)O)(2)][N(SO(2)CF(3))(2)

The new tin(IV) species (CH(3))(2)SnCl(OTeF(5)) was prepared via either the solvolysis of (CH(3))(3)SnCl in HOTeF(5) or the reaction of (CH(3))(3)SnCl with ClOTeF(5). It was characterized by NMR and vibrational spectroscopy, mass spectrometry, and single crystal X-ray diffraction. (CH(3))(2)SnCl(OTeF(5)) crystallizes in the monoclinic space group P2(1)/n (a = 5.8204(8) A, b =10.782(1) A, c =15.493(2) A, beta = 91.958(2) degrees, V = 971.7(2) A(3), Z = 4). NMR spectroscopy of (CH(3))(3)SnX, prepared from excess Sn(CH(3))(4) and HX (X = OTeF(5) or N(SO(2)CF(3))(2)), revealed a tetracoordinate tin environment using (CH(3))(3)SnX as a neat liquid or in dichloromethane-d(2) (CD(2)Cl(2)) solutions. In acetone-d(6) and acetonitrile-d(3) (CD(3)CN) solutions, the tin atom in (CH(3))(3)SnOTeF(5) was found to extend its coordination number to five by adding one solvent molecule. In the strong donor solvent DMSO, the Sn-OTeF(5) bond is broken and the (CH(3))(3)Sn(O=S(CH(3))(2))(2)(+) cation and the OTeF(5)(-) anion are formed. (CH(3))(3)SnOTeF(5) and (CH(3))(3)SnN(SO(2)CF(3))(2) react differently with water. While the Te-F bonds in the OTeF(5) group of (CH(3))(3)SnOTeF(5) undergo complete hydrolysis that results in the formation of [(CH(3))(3)Sn(H(2)O)(2)](2)SiF(6), (CH(3))(3)SnN(SO(2)CF(3))(2) forms the stable hydrate salt [(CH(3))(3)Sn(H(2)O)(2)][N(SO(2)CF(3))(2)]. This salt crystallizes in the monoclinic space group P2(1)/c (a = 7.3072(1) A, b =13.4649(2) A, c =16.821(2) A, beta = 98.705(1) degrees, V = 1636.00(3) A(3), Z = 4) and was also characterized by NMR and vibrational spectroscopy.     

Design and synthesis of fluconazole/bile acid conjugate using click reaction

Novel fluconazole/bile acid conjugates were designed and their regioselective synthesis was achieved in very high yield via Cu(I) catalyzed intermolecular 1,3-dipolar cycloaddition. These new molecules showed good antifungal activity against Candida species.