Internal energy content of n-butylbenzene, bromobenzene, iodobenzene and aniline molecular ions generated by two-photon ionization at 266 nm. A photodissociation study

A technique to investigate photodissociation kinetics on a nanosecond time scale has been devised for molecular ions generated by multiphoton ionization (MPI) using mass-analyzed ion kinetic energy spectrometry. The branching ratio or rate constant has been determined for the photodissociation of the n-butylbenzene, bromobenzene, iodobenzene, and aniline molecular ions generated by MPI at 266 nm. The ion internal energies have been estimated by comparing the measured kinetic data with the previous energy dependence data. The analysis has shown that only those molecular ions generated by two-photon ionization contribute to the photodissociation signals. Around half of the available energy has been found to remain as molecular ion internal energy in the two-photon ionization process. Copyright 1999 John Wiley & Sons, Ltd.     

Synthesis and Reactivity towards DIBAL‐H of Cyclo‐Siloxanes cyclo‐[R2SiOSi(Ot‐Bu)2O]2, cyclo‐(t‐BuO)2Si(OSiR2)2O,and cyclo‐R2Si[OSi(Ot‐Bu)2]2O (R = Me,Ph)

The six‐, eight‐ and twelve‐membered cyclo‐siloxanes, cyclo‐[R₂SiOSi(Ot‐Bu)₂O]₂ (R = Me ( 1 ), Ph ( 2 )), cyclo‐(t‐BuO)₂Si(OSiR₂)₂O (R = Me ( 3 ), Ph ( 4 )), cyclo‐R₂Si[OSi(Ot‐Bu)₂]₂O (R = Me ( 5 ), Ph ( 6 )) and cyclo‐[(t‐BuO)₂Si(OSiMe₂)₂O]₂ ( 3a ) were synthesized in high yields by the reaction of (t‐BuO)₂Si(OH)₂ and [(t‐BuO)₂SiOH]₂O with R₂SiCl₂ and (R₂SiCl)₂O (R = Me, Ph). Compounds 1 — 6 were characterized by solution and solid‐state ²⁹Si NMR spectroscopy, electrospray mass spectrometry and osmometric molecular weight determination. The molecular structure of 4 has been determined by single crystal X‐ray diffraction and features a six‐membered cyclo‐siloxane ring that is essentially planar. The reduction of 1 — 6 with i‐Bu₂AlH (DIBAL‐H) led to the formation of the metastable aluminosiloxane (t‐BuO)₂Si(OAli‐Bu₂)₂ ( 7 ) along with Me₂SiH₂ and Ph₂SiH₂.     

Crystallographic report: 1,3‐Bis[(trimethylsilylmethyl)dichlorostannyl]propane, [(Me3SiCH2)Cl2Sn]2(CH2)3

The dinuclear molecule of [(Me₃SiCH₂)Cl₂Sn]₂(CH₂)₃ adopts an extended conformation and features distorted tetrahedral tin centres, with the greatest distortion manifested in the C? Sn? C angles of approximately 128 °. The distortions are ascribed to the influence of intermolecular Sn···Cl interactions. Copyright © 2002 John Wiley & Sons, Ltd.     

Bis(3‐endo‐camphoryl)phosphinic Acid,a Non‐Racemic Helical Supramolecular Host with Aquapores

Bis(3‐endo‐camphoryl)phosphinic acid ( 1 ) was prepared by the reaction of the lithium enolate of D‐(+)‐camphor and phosphorous trichloride followed by an oxidative work up. Compound 1 crystallizes from wet toluene as monohydrate 1 ·H₂O, which was investigated by X‐ray crystallography. Molecules of 1 are associated by strong hydrogen bonds giving rise to the formation of a supramolecular helix. The interior channel of the helix is filled by a one‐dimensional (1D) string of water molecules that are also associated by hydrogen bonding. The 1D string adopts a twisted zigzag conformation. Although the hydrogen bond networks are not cross‐linked both the screw of the helix and the twist of the 1D string of water molecules are left‐handed (M) and controlled by the chiral camphoryl residues situated on the exterior of the helix. The overall supramolecular structure is strongly reminiscent of aquaporin‐1, a significant membrane‐channel protein responsible for the transport of water into the cells.     

1-Naphthyl- and mesityltellurium(IV, II) derivatives of small bite chelating organic ligands: Effect of steric bulk and intramolecular secondary bonding interaction on molecular geometry and supramolecular association

The synthesis and characterization of unsymmetric diorganotellurium compounds containing a sterically demanding 1-naphthyl or mesityl ligand and a small bite chelating organic ligand capable of 1,4-Te?N(O) intramolecular interaction is described. The reaction of ArTeCl₃ (Ar = 1-C₁₀H₇, Np; 2,4,6-Me₃C₆H₂, Mes) with (SB)HgCl [SB = the Schiff base, 2-(4,4′-NO₂C₆H₄CHNC₆H₃-Me)] or a methyl ketone (RCOCH₃) afforded the corresponding dichlorides (SB)ArTeCl₂ (Ar = Np, 1Aa; Mes, 1Ba) or (RCOCH₂)ArTeCl₂ (Ar = Np; R = Ph (2Aa), Me (3Aa), Np (4Aa); Ar = Mes, R = Ph (2Ba)). Reduction of 1Aa and 1Ba by Na₂S₂O₅ readily gave the tellurides (SB)ArTe (Ar = Np (1A), Mes, (1B)) but that of dichlorides derived from methylketones was complicated due to partial decomposition to tellurium powder and diarylditelluride (Ar₂Te₂), resulting in poor yields of the corresponding tellurides 2A, 2B and 3A. Oxidation of the isolated tellurides with SO₂Cl₂, Br₂ and I₂ yielded the corresponding dihalides. All the synthesized compounds have been characterized with the help of IR, ¹H, ¹³C, and ¹²⁵Te NMR and in the case of 2Aa, and 2Ba by X-ray crystallography. Appearance of only one ¹²⁵Te signal indicated that the unsymmetric derivatives were stable to disproportionation to symmetric species. Intramolecular 1,4-Te?O secondary bonding interactions (SBIs) are exhibited in the crystal structures of both the tellurium(IV) dichlorides, 2Aa, and 2Ba. Steric repulsion of the mesityl group in the latter dominates over lone pair-bond pair repulsion, resulting in significant widening of the equatorial C-Te-C angle. This appears to be responsible for the lack of Te?Cl involved supramolecular associations in the crystal structure of 2Ba.     

Clifford Fourier Transformation and Uncertainty Principle for the Clifford Geometric Algebra Cl 3,0

First, the basic concept of the vector derivative in geometric algebra is introduced. Second, beginning with the Fourier transform on a scalar function we generalize to a real Fourier transform on Clifford multivector-valued functions Third, we show a set of important properties of the Clifford Fourier transform on Cl_3,0 such as differentiation properties, and the Plancherel theorem. Finally, we apply the Clifford Fourier transform properties for proving an uncertainty principle for Cl_3,0 multivector functions.     

Synthesis and structure of some cis-and trans-myrtanylstannanes

Enantiomerically pure cis- and trans-myrtanylstannanes cis-MyrSnPh₃ (1), trans-MyrSnPh₃ (2), cis-MyrSnPh₂Cl (3), trans-MyrSnPh₂Cl (4), cis-MyrSnPhCl₂ (5), trans-MyrSnPhCl₂ (6), cis-MyrSnCl₃ (7), trans-MyrSnCl₃ (8) were synthesized and fully characterized by ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy. The molecular structures of 1, 3, 6, 7, and [trans-MyrSn(OH)Cl₂ · H₂O]₂ (8a) a hydrolysis product of 8, were determined by X-ray crystallography.