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The relative stereochemistry of acyclic diamines with several stereogenic centers has been analyzed by NMR spectroscopy in combination with conformational deconvolution. Binding to a bisporphyrin molecular clip improves the stereochemical assignment significantly. The diamines were synthesized from inexpensive sugar alcohols, and their stable hydrochlorides were quantitatively converted into free bases by treatment with ion-exchange resin., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Thermal cycloaddition of 1,3-dipolar azomethine ylides to the sidewalls of multiwalled carbon nanotubes (MWNTs) has been used to prepare MWNTs that contain 2-methylenethiol-4-(4-octadecyloxyphenyl) (4), N-octyl-2-(4-octadecyloxyphenyl) (5) or 2-(4-octadecyloxyphenyl)pyrrolidine (6) units. All these contain the 4-octadecyloxyphenyl substituent that acts as a solubilizing group. Microwave (MiW)-assisted heating was found to be highly efficient for soluble MWNTs, for which the amount of added groups after only 2 h of MiW heating at 200 degrees C, determined by using thermogravimetric analysis, was found to be in the same range as that obtained after 100-120 h of conventional heating of soluble and insoluble MWNTs. Solubility is a key feature for a successful MiW-heated reaction; MWNTs insoluble in the reaction medium yielded considerably less addends in the MiW-heated reactions than in the conventionally heated reaction. The location and even distribution of the pyrrolidine units over the outermost layer of the MWNTs was verified by transmission electron microscopy analysis of 4 that had been treated with gold nanoparticles and thoroughly washed to remove gold particles adsorbed on nonfunctionalized parts of the MWNTs.

Semiempirical and density functional electronic structure theory methods were used to study SWNT-X--R bond strengths, where the single-walled carbon nanotube (SWNT) had an armchair or zigzag structure, the link heteroatom X was O, N(H), or S and the hydrocarbon chain R was CH(2)CH(3), CH(OH)CH(3), CHCH(2), or CH(CF(3))CH(3). In all systems the hydrocarbon was bonded to the end of the nanotube. The SWNT-X--R bond (that is, the bond joining the link atom to the hydrocarbon) is more than 0.4 eV stronger for armchair than for zigzag nanotubes with the same diameters, irrespective of whether O, N, or S are used as link atoms or whether OH, C==C, or CF(3) groups are present in the hydrocarbon chain. This raises the possibility for selective manipulation of armchair/zigzag nanotubes using a variety of link atoms and hydrocarbon structures. The SWNT-O--CH(CF(3))CH(3) bond is weaker than the SWNT-O--CH(2)CH(3) bond (for both armchair and zigzag nanotubes), while inclusion of a double bond in the ethyl chain increases the bond strengths. Also, SWNT-S--CH(2)CH(3) and SWNT-N(H)--CH(2)CH(3) bonds are stronger than SWNT-O--CH(2)CH(3) bonds.

The chiral chelating ligand N,N'-bis(phenylethyl)bispidine (1) forms a rigid cavity which accommodates (pi-allyl)palladium species with high selectivity. In the resulting complex, the absolute configuration of the pi-allyl ligand can be determined by the detection in NMR spectra of a few unambiguous interligand NOEs. Dynamic processes involving the pi-allyl ligand can be investigated. Depending on the analytical target, ligand (S,S)-1 or (R,R)-1 may be used.