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“Orientational isomerism” is a concept necessary for deeper understanding of the selective reactivities in a host-guest system. This concept has been rarely explored in the context of supramolecular host guest chemistry. We designed a model system including four cyclohexene derivatives and a water-soluble host Octa Acid (OA), with hydrophobic inner cavity. The overall length of the guest molecules (~ 12 Å) was limited by manipulating the alkyl substituents at 1- and 4-positions on the cyclohexene ring. 1D 1H /2D COSY and NOESY NMR and photooxygenation reaction were used to understand the observations with this model system. Specific packaging or “orientational isomerism” of each guest molecule, induced by the host OA led to specific, in one case enhanced product selectivity. With this model system we show the important role of “orientational isomerism” in explaining enhanced product selectivity in a host-guest supramolecular system. 

Excited state chemistry and physics of molecules, in addition to their inherent electronic and steric features, depend on their immediate microenvironments. This study explores the influence of an organic capsule, slightly larger than the reactant molecule itself, on the excited state chemistry of the encapsulated molecule. Results presented here show that the confined molecule, in fact, is not isolated and can be manipulated from outside even without direct physical interaction. Examples where communication between a confined molecule and a free molecule present outside is brought about through electronic and energy transfer processes are presented. Geometric isomerization of octa acid encapsulated stilbenes induced by energy and electron transfer by cationic sensitizers that attach themselves to the anionic capsule is examined. The fact that isomerization occurs when the sensitizer present outside is excited illustrates that the reactant and sensitizer are communicating across the molecular wall of the capsule. Ability to remotely activate a confined molecule opens up new opportunities to bring about reactions of confined radical ions and triplet excited molecules generated via long distance energy and electron transfer processes. 

Extending the applications of Photoremovable Protecting Groups (PPGs) to “cage” phenols has generally met with unusually complex PPG byproducts. In this study, we demonstrate that the p –hydroxyphenacyl (pHP) cage for both simple and complex phenolics, including tyrosine, dispenses free phenols. With the simpler unsubstituted phenols, the reaction is governed by their Brønsted Leaving Group ability. On the other hand, the byproducts of the cage vary with these phenols. For the more acidic phenols the cage byproduct follows the Favorskii rearrangement to form p -hydroxyphenylacetic acid whereas for the weaker phenols other reactions such as reduction and hydrolysis begin to emerge. When the photolysis is conducted in octa acid (OA) containers, non-Favorskii, unrearranged fragments of the cage and other byproducts arise. 

ortho -Nitrobenzyl ( o NB) triggers have been extensively used to release various molecules of interest. However, the toxicity and reactivity of the spent chromophore, o -nitrosobenzaldehyde, remains an unaddressed difficulty. In this study we have applied the well-established supramolecular photochemical concepts to retain the spent trigger o -nitrosobenzaldehyde within the organic capsule after release of water-soluble acids and alcohols. The sequestering power of organic capsules for spent chromophores during photorelease from ortho -nitrobenzyl esters, ethers and alcohols is demonstrated with several examples.