Pulsed nuclear magnetic resonance and molecular reorientation in solid 1,3,5-trifluorobenzene

Single and double-pulse transient experiments have been used for the direct measurement of the resonant and non-resonant spin contributions to the ¹H and ¹⁹F second moments in polycrystalline 1,3,5,-C₆H₃F₃. The applicability of these experiments to molecular solids is examined. The temperature dependence of the experimental proton second moment has been investigated between 130 K and the melting point at 267·7 K; a transition centred on 200 K is observed. It is shown that the molecules have an ordered arrangement in the crystal at all temperatures and that this transition is due to thermally activated reorientational jumps of the molecules through 120° about their triad axes. The activation energy for this motion is 42·7 ± 2·9 kJ mol^-1 as determined from the temperature dependence of the ‘apparent’ second moment in the transition region.     

Reduced-symmetry deep-cavity cavitands

The syntheses of reduced-symmetry deep-cavity cavitands by two-stage stereoselective bridging with substituted benzal bromides is reported. Conditions for the optimal formation of the trisbridged derivatives were readily established. However, it was not possible to determine conditions which selectively promoted formation of either one of the two bisbridged species, or the monobridged compound, above the other products. A comparison of yields for A/B bisbridged derivatives verses A/C bisbridged derivatives may indicate that the one-pot formation of deep-cavity cavitands occurs primarily through the former species.     

Guest-controlled self-sorting in assemblies driven by the hydrophobic effect

The extent of self-sorting in systems comprised of two different deep-cavity cavitands is investigated. The nature of the guest(s) encapsulated in the resulting assemblies is shown to profoundly influence the extent of self-sorting.     

A deuterated deep-cavity cavitand confirms the importance of C-H...X-R hydrogen bonds in guest binding

A deuterated cavitand host was examined for its affinity to a series of guests; for halogenated, preorganized guests binding was significantly stronger than the corresponding protium host.     

Water-soluble, self-assembling container molecules: an update

Over the past five years, an important development in the area of self-assembling containers has been the increase in interest in those containers that function in aqueous solution. This progress is a reflection of a similar trend within supramolecular chemistry in general, and is driven in part by the need to address issues and challenges within the biological sciences, as well as a desire to develop new strategies for greener chemistries carried out in water. It is also an opportunity to learn more about fundamental topics such as the hydrophobic effect. In this critical review we discuss progress in aqueous-based self-assembling container molecules since 2005 (177 references).     

Solvent denaturation of supramolecular capsules assembled via the hydrophobic effect

The organic co-solvent induced denaturation of a series of capsular complexes formed between trioxolane guests and a water-soluble deep-cavity cavitand was examined. The results obtained demonstrate a wide range of denaturation properties, and suggest the important factors governing capsule stability.     

An efficient one-pot synthesis of coumarin-amino acid derivatives as potential anti-inflammatory and antioxidant agents

Abstract

A series of seven coumarinyl-amino acid ester conjugates have been synthesized and characterized by NMR (¹H and 13C) and mass spectra. Further, the compounds were investigated for their therapeutic applications such as anti-inflammatory and antioxidant activities. Among the synthesized compounds most of the analogs showed good efficiency compared with the standard.