- Moessbauer studies of pressure-induced amorphization in the molecular crystal SnBr4
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Properties of the molecular structure abd the Sn(IV) valence of the pressure-amorphized SnBr4 molecular crystal were investigated by (119)Sn Moessbauer spectroscopy. Studies were conducted at 80 K with pressures to 25 GPa, far beyond the amorphization onset at P(c) = 7 - 9 GPa as determined by previous Raman studies. No valence change in the Sn(IV) central ion takes place as deduced from the isomer shift (IS) variation with pressure, in contrast to the analogous molecular crystal SnI4 which undergoes amorphization and metallization under pressure. The IS value of 1.15(5) mm/s, with respect to a CaSnO3 source at 300 K, remains practically constant over the whole pressure range, suggesting little variation in both the Sn-Br intramolecular distances and covalency within the amorphous and/or insulator pressure regime. A single line spectrum is characteristic of the Moessbauer data obtained in the 0 - 5 GPa range, indicating the preservation of fourfold symmetry of the SnBr4 molecule in the crystal. Above 5 GPa, near P(c), a quadruple interaction takes place concurrentwith a dramatic increase in the recoil-free fraction (f). The value of the quadrupole splitting reaches a maximum of 0.9 mm/s at P .apprx. 15 G Pa and remains constant thereafter. By .apprx. 9 GPa the absorption area, which is proportional to f, increases by 30 - 40% over the lowest pressure value and then remains constant at higher pressure. These results are consistent with the formation of a molecular species, e.g., a (SnBr4)2 dimer, lacking the T(d) symmetry at the original Sn(4+) site and having optical phonons hard enough not to be excited by the nuclear recoil process. Molecular association into (SnBr4)2 dimers, the building block ofthe high-pressure disordered state, also explains many of the experimen tal features of the Raman data. Upon decompression, Moessbauer (and Raman) data suggest that these dimers dissociate into monomers at .apprx. 5 GPa; however, a disordered structure of SnBr4 persists as pressure is decreased further. Crystallization is fully recovered below 1 GPa. The nature of the pressure-induced amorphization of the insulator SnBr4 is discussed in terms of the structural and valence properties of the analogousmetallic SnI4.
- Hearne, G. R.,Pasternak, M. P.,Taylor, R. D.
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- Influence of hidden halogen mobility on local structure of CsSn(Cl1?xBrx)3mixed-halide perovskites by solid-state NMR
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Tin halide perovskites are promising candidates for lead-free photovoltaic and optoelectronic materials, but not all of them have been well characterized. It is essential to determine how the bulk photophysical properties are correlated with their structures at both short and long ranges. Although CsSnCl3is normally stable in the cubic perovskite structure only above 379 K, it was prepared as a metastable phase at room temperature. The transition from the cubic to the monoclinic phase, which is the stable form at room temperature, was tracked by solid-state133Cs NMR spectroscopy and shown to take place through a first-order kinetics process. The complete solid solution CsSn(Cl1?xBrx)3(0 ≤x≤ 1) was successfully prepared, exhibiting cubic perovskite structures extending between the metastable CsSnCl3and stable CsSnBr3end-members. The NMR spectra of CsSnBr3samples obtained by three routes (high-temperature, mechanochemical, and solvent-assisted reactions) show distinct chemical shift ranges, spin-lattice relaxation parameters and peak widths, indicative of differences in local structure, defects and degree of crystallinity within these samples. Variable-temperature119Sn spin-lattice relaxation measurements reveal spontaneous mobility of Br atoms in CsSnBr3. The degradation of CsSnBr3, exposed to an ambient atmosphere for nearly a year, was monitored by NMR spectroscopy and powder X-ray diffraction, as well as by optical absorption spectroscopy.
- Karmakar, Abhoy,Bhattacharya, Amit,Sarkar, Diganta,Bernard, Guy M.,Mar, Arthur,Michaelis, Vladimir K.
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p. 3253 - 3263
(2021/03/17)
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- Synthesis, structure, third-order nonlinear optical properties and Hirshfeld surface analysis of tetrakis(azepanium) hexachlorostannate(IV) dichloride and tetrakis(azepanium) hexabromostannate(IV) dibromide
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The new organic-inorganic hybrids of tetrakis(azepanium) hexachlorostannate(IV) dichloride (1) and tetrakis(azepanium) hexabromostannate(IV) dibromide (2) crystals have been grown after slow evaporation of the solvent and characterized through single-crys
- Manonmani,Balakrishnan,Dhanalakshmi,Ahamed, S. Rafi,Vinitha,Sockalingam
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- Metal-organic hybrids of tin(IV): Synthesis, crystal structure, third-order nonlinear optical properties and Hirshfeld surface analysis of bis(1,2,3,4-tetrahydroquinolinium) hexahalostannate(IV)
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The self-assembled organic-inorganic hybrid materials such as bis(1,2,3,4-tetrahydroquinolinium) hexachlorostannate(IV) (1) and bis(1,2,3,4-tetrahydroquinolinium) hexabromostannate(IV) (2) have been synthesized for their huge applications in opto-non-line
- Dhanalakshmi,Balakrishnan,Ahamed, S. Rafi,Vinitha,Parthiban
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- Fluorous reaction systems
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The present invention provides a method for carrying out a chemical reaction comprising the steps of forming an organic/fluorous solubilizing liquid phase comprising a solvent system. The solvent system is selected or adapted to substantially solubilize a fluorous reaction component or components (that is, a fluorous reagent, a fluorous catalyst and/or a fluorous reactant). The "fluorous reaction component" is functionalized to comprise at least one fluorous moiety having the formula -(R)d (Rf)e. (Rf)e is at least one fluorous group and e is a whole number. (R)d is an organic (for example, hydrocarbon) spacer group, which may be present or absent, and d is an integer equal to at least zero. The solvent system is also adapted to substantially solubilize an organic reaction component or components. After the reaction occurs in the organic/fluorous solubilizing liquid phase, a phase separation into at least a fluorous phase and an organic phase is effected. The present invention also provides a chemical compound of the formula XM?(R) (Rf)!3, wherein M is Ge or Sn and X is an atom or group selected to react with an organic reaction component or components.
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- Synthesis and characterization of allylic dihaloboranes
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Volatile allylic dihaloboranes have been prepared and characterized by 1H, 11B, 13C, and 19F NMR spectroscopy and mass spectrometry. The stability (τ1/2) of such compounds in dilute CDCl3 solutions depends on the substituents and the halides and ranges from a few minutes (allylic dibromoboranes) to several days (allylic difluoroboranes). Allyldihaloborane etherates were obtained by addition of diethyl ether to the corresponding free allyldihaloborane.
- Le Serre, Stéphanie,Guillemin, Jean-Claude
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p. 5844 - 5848
(2008/10/08)
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- The theory of regular solutions applied to molar excess enthalpies and volumes of binary mixtures containing stannic bromide
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The molar excess enthalpies, HmE, at 313.15 K and molar excess volumes, VmE, at 303.15, 308.15, and 313.15 K for the binary mixtures of stannic bromide with benzene, cyclohexane, and tetrachloromethane have been determined.Both HmE and VmE for the three sets of binary mixtures are positive over the entire range of composition.The experimental results have been compared with those predicted by regular solution theory.It is observed that HmE calculated for regular solutions are highly sensitive to the estimation of C12.The calculated VmE are in good agreement with the experimental data if it is assumed that (dE/dP)T=0; and the ratio of internal pressures to the cohesive energy densityare the same for unmixed and the mixed components.
- Suri, S. K.,Maheshwari, R. C.
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p. 707 - 711
(2007/10/02)
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- The Heat Capacities, Entropies, and Enthalpies of Tin Tetrabromide in the Temperature Range of 6.7-330 K
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Measurements of Cp, used subsequently for determining the thermodynamic characteristics of the phase transitions of SnBr4 are reported.The enthalpy difference and the entropy under standard conditions have been calculated from the results.
- Berezovskii, G. A.,Stenin, Yu. G.,Paukov, I. E.
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p. 593 - 594
(2007/10/02)
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- Phosphorus-31 and tin-119 NMR studies on tin(IV) halides and their adducts
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Tin-119 NMR spectra have been recorded for SnX4 (X = Cl, Br, I) and mixtures thereof. All fifteen possible SnClxBryIz (x + y + z = 4) species were observed. Tin-119 NMR spectra were observed for SnX-5 and SnX2-6 (X = Cl, Br) and for an equimolar mixture of SnCl2-6 and SnBr2-6 which gave all ten possible isomers of [SnClxBr6-x]2- in the statistical distribution. Phosphorus-31 and tin-119 NMR spectra were observed for SnX4(PBu3)2 (X = Cl, Br) and a mixture gave all six possible trans phosphine isomers in the statistical distribution. [SnX5(PBu3)]- (X = Cl, Br) species show some disproportionation, although the [SnX5(PBu3)]- ion is the dominant species in solution. A mixture of [SnCl5(PBu3)]- and [SnBr5-(PBu3)]- gave a complex mixture in solution, but all twelve isomers of the [SnCl5Br5-x(PBu3)]- series were identified. The well known pairwise additivity model fits well within the tetrahalide or hexahalide anion series and it is shown that the chemical shift of tin both tetrahedral and octahedral environments may be predicted from a single set of interaction parameters if geometrical factors are taken into account. The same interaction parameters are of use in identifying the mixed tin halide-phosphine complexes.
- Colton, Ray,Dakternieks, Dainis,Harvey, Cheryl-Ann
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- Boron-nitrogen compounds. XIV. The preparation of vinyldibromoborane and some of its reactions with amines
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In the reaction of tetravinyltin with boron tribromide, mercury has been found to exhibit a twofold effect: (a) it ensures the utilization of all four organic groups for the conversion of the boron trihalide to an organodihalogenoborane and (b) one notes the complete absence of organoboron by-products. As a result, the isolation and characterization of vinyldibromoborane was accomplished. Reactions of the latter compound with various amines have been studied and B-vinylated bisaminoboranes, 1,3,2-diazaborolidines, and borazines have been prepared. B-Vinylation does not appear to influence the electronic nature of the B-N bond to any appreciable degree.
- Fritz, Peter,Niedenzu, Kurt,Dawson, John W.
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p. 626 - 627
(2008/10/08)
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