A light controlled cavitand wall regulates guest binding

Here we report a cavitand with a photochemical switch as one of the container walls. The azo-arene switch undergoes photoisomerization when subjected to UV light producing a self-fulfilled cavitand. This process is thermally and photochemically reversible. The reported cavitand binds small molecules and these guests can be ejected from the cavitand through this photochemical process.     

Resolving Component Overlap in Multiwavelength Kinetic Spectroscopy: Application to Raman Scattering from Intermediates in Triplet-State Photoreactions

Abstract— Understanding of reaction mechanisms in photochemistry is advanced both by kinetic measurements to determine rates of reaction and by spectroscopic studies of the structures of precursors and photoproducts. When kinetics and spectroscopy are combined in a time-resolved, multiwavelength spectroscopic measurement on a reacting system, spectra and structures of intermediates can also be determined. In this paper, the application of multidimensional least-squares and factor analysis techniques for resolving overlapped spectra from intermediates in photochemical kinetics are discussed. The methods are employed specifically to resolve Raman spectra of intermediates in triplet-state photoreactions. By varying excitation intensity, spectra of excited-triplet states are resolved from ground states and solvent. By varying the concentration of a triplet quencher in the sample, the Raman spectrum of a sensitizer excited state (benzophe-none) can be resolved from those of acceptor-triplet states or radical photoproducts. Applications of these concepts in other areas of photochemical kinetics are addressed.     

Crystal engineering of novel cocrystals of a triazole drug with 1,4-dicarboxylic acids

Cocrystals of the poorly soluble antifungal drug cis-itraconazole (1) with 1,4-dicarboxylic acids have been prepared. The crystal structure of the succinic acid cocrystal with 1 was determined to be a trimer by single-crystal X-ray. The trimer is comprised of two molecules of 1 oriented in antiparallel fashion to form a pocket with a triazole at either end. The extended succinic acid molecule fills the pocket, bridging the triazole groups through hydrogen-bonding interactions rather than interacting with the more basic piperazine nitrogens. The solubility and dissolution rate of some of the cocrystals are approximately the same as those of the amorphous drug in the commercial formulation and are much higher than those for the crystalline free base. The results suggest that cocrystals of drug molecules have the possibility of achieving the higher oral bioavailability common for amorphous forms of water-insoluble drugs while maintaining the long-term chemical and physical stability that crystal forms provide.     

Divergent Late‐Stage (Hetero)aryl C−H Amination by the Pyridinium Radical Cation

(Hetero)arylamines constitute some of the most prevalent functional molecules, especially as pharmaceuticals. However, structurally complex aromatics currently cannot be converted into arylamines, so instead, each product isomer must be assembled through a multistep synthesis from simpler building blocks. Herein, we describe a late‐stage aryl C?H amination reaction for the synthesis of complex primary arylamines that other reactions cannot access directly. We show and rationalize through a mechanistic analysis the reasons for the wide substrate scope and the constitutional diversity of the reaction, which gives access to molecules that would not have been readily available otherwise.     

Ferrocene derivatives included in a water-soluble cavitand: are they electroinactive?

The formation in aqueous solution of kinetically stable inclusion complexes between a deep-cavity cavitand and several redox active ferrocene derivatives was demonstrated using (1)H NMR spectroscopy. The electrochemical kinetics of the inclusion complexes was strongly attenuated as compared to that observed with the free guests.     

Infrared spectra of V(n)Bz(n+1) sandwich clusters: a theoretical study of size evolution

Results of density functional theory computations of infrared (IR) spectra of linear sandwich V(n)Bz(n+1), n = 1-6, complexes are presented. It is shown that the systematic changes in the spectra as a function of the complex size can be categorized and understood in terms of responses of the "parent" modes of the Bz molecule and the VBz complex. The analysis presented should be applicable to a broad class of linear sandwich systems.