Syntheses and structural characterization of the heavier alkali-metal stannates bearing the tripodal triamino framework: structural trends in the series of [MeSi(SiMe2N(4-CH3C6H4))3Sn][M] (M = Na,K, Rb)

Treatment of the lithium stannate [MeSi(SiMe(2)N(4-CH(3)C(6)H(4)))(3)SnLi(OEt(2))] (1) with AgCl yielded the corresponding distannane [MeSi(SiMe(2)N(4-CH(3)C(6)H(4)))(3)Sn](2) (2) as the product of an oxidative coupling in good yield. The distannane (2) underwent reductive cleavage with the heavier alkali metals (sodium, potassium, rubidium) in a non-coordinating solvent (toluene or cyclohexane), to afford the solvate-free stannates(II) [MeSi(SiMe(2)N(4-CH(3)C(6)H(4)))(3)Sn][M] (M = Na (3), K (4), and Rb (5)), which were structurally characterized. The Na atom in 3 is directly bonded to two of the three amido-N atoms of the stannate cage and additionally solvated by pi-coordination of a tolyl substituent of a neighboring stannate cage. In contrast, the group 1 metal cations in the two isomorphous compounds 4 and 5 are further removed from the nitrogen functions and are pi-coordinated by three tolyl arene rings. The Sn-K distances in 4 were found to be 3.635 and 3.870 A, whereas the Sn-Rb contacts in 5 are 3.708 and 3.908 A; these are the first such Sn-Rb bonding contacts to be characterized in a molecular compound by X-ray diffraction.     

A high-resolution study of the 14.4-μm infrared band of deuterofluoroform

The FT-IR spectrum of the ν₃ parallel band of deuterofluoroform has been recorded at a resolution of 0.0045 cm^?1. Nine independent spectral parameters were determined which reproduce some 650 observed wavenumbers with a standard error of 3 × 10^?4 cm^?1. The constants derived for the ν₃ band are (in cm^?1): ν₀ = 694.2822(3); B₀ = 0.3309321(9); B₃ = 0.3302464(11); α^B = 6.859(10) × 10^?4; α^C = 1.429 × 10^?4; D₃^J = 3.168(3) × 10^?7; D₀^J = 3.188(3) × 10^?7; D_JK³ = 4.766 × 10^?7; D_JK⁰ = 4.864 × 10^?7; and D_K⁰ ? D_K³ = 2 × 10^?10.     

Comparison of Two Inverse Filtering Methods in Parameterization of the Glottal Closing Phase Characteristics in Different Phonation Types

SUMMARY: Inverse filtering (IF) is a common method used to estimate the source of voiced speech, the glottal flow. This investigation aims to compare two IF methods: one manual and the other semiautomatic. Glottal flows were estimated from speech pressure waveforms of six female and seven male subjects producing sustained vole /a/ in breathy, normal, and pressed phonation. The closing phase characteristics of the glottal pulse were parameterized using two time-based parameters: the closing quotient (C1Q) and the normalized amplitude quotient (NAQ). The information given by these two parameters indicates a strong correlation between the two IF methods. The results are encouraging in showing that the parameterization of the voice source in different speech sounds can be performed independently of the technique used for inverse filtering.     

Unsymmetrical Ni(II)-imidoylamidine complexes derived from a novel oxime-mediated single-pot reaction of nitriles

The neutral bisimidoylamidine (or 1,3,5-triazapentadiene) Ni(II) complexes [Ni{HN=C(R)N=C(C(6)H(4)CO)N}(2)] {R=Me, Et, nPr, iPr, (CH(2))(3)Cl}, bearing an iminoisoindolinone moiety, have been generated by a novel 2-propanone oxime-mediated single-pot reaction of phthalonitrile and nickel(II) acetate in solution of the corresponding alkylnitrile (RCN). Single-crystal X-ray diffraction analyses indicate a square-planar geometry of the imidoylamidine core. The synthesised compounds represent rare specimens of genuine unsymmetrical imidoylamidine complexes as well as their first examples generated from nitriles in a single-pot reaction.     

Interplay of electrostatic and hydrophobic effects with binding of cationic gemini surfactants and a conjugated polyanion: experimental and molecular modeling studies

Understanding factors responsible for the fluorescence behavior of conjugated polyelectrolytes and modulation of their behavior are important for their application as functional materials. The interaction between the anionic poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl}copolymer (PBS-PFP) and cationic gemini surfactants alpha,omega-(CmH2m+1N+(CH3)2)2(CH2)s(Br-)2 (m-s-m; m=12, s=2, 3, 5, 6, 10, and 12) has been studied experimentally in aqueous solution. These surfactants are chosen to see whether molecular recognition and self-assembly occurs between the oppositely charged conjugated polyelectrolyte and gemini surfactant when the spacer length on the surfactant is similar to the intercharge separation on the polymer. Without surfactants, PBS-PFP exists as aggregates. These are broken up upon addition of gemini surfactants. However, as anticipated, the behavior strongly depends upon spacer length (s). Fluorescence measurements show three surfactant concentration regimes: At low concentrations (<2x10(-6) M) quenching occurs and is most marked with the small spacer 12-2-12; at intermediate concentrations (approximately 2x10(-6)-10(-3) M), fluorescence intensity is constant, with a 12-carbon spacer 12-12-12 showing the strongest fluorescence; above the critical micelle concentration (CMC; approximately 10(-3) M) increases in emission intensity are seen in all cases and are largest with the intermediate spacers 12-5-12 and 12-6-12, where the spacer length most closely matches the distance between monomer units on the polymer. With longer spacer length surfactants, surface tension measurements for concentrations below the CMC reveal the presence of polymer-surfactant aggregates at the air-water interface, possibly reflecting increased hydrophobicity. Above the CMC, small-angle neutron scattering experiments for the 12-6-12 system show the presence of spherical aggregates, both for the pure surfactant and for polyelectrolyte/gemini mixtures. Molecular dynamics simulations help rationalize these observations and show that there is a very fine balance between electrostatic and hydrophobic interactions. With the shortest spacer 12-2-12, Coulombic interactions are dominant, while for the longest spacer 12-12-12 the driving force involves hydrophobic interactions. Qualitatively, with the intermediate 12-5-12 and 12-6-12 systems, the optimum balance is observed between Coulombic and hydrophobic interactions, explaining their strong fluorescence enhancement.     

Concerted halogen and hydrogen bonding in [RuI2(H2dcbpy)(CO)2]···I2···(CH3OH)···I2···[RuI2(H2dcbpy)(CO)2

A new type of concerted halogen bond-hydrogen bond interaction was found in the solid state structure of [RuI(2)(H(2)dcbpy)(CO)(2)]···I(2)···(MeOH)···I(2)···[RuI(2)(H(2)dcbpy)(CO)(2)]. The iodine atoms of the two I(2) molecules interact simultaneously with each other and with the OH group of methanol of crystallization. The interaction was characterized by single crystal X-ray measurements and by computational charge density analysis based on DFT calculations.