Excited State Chemistry of Capsular Assemblies in Aqueous Solution and on Silica Surfaces

Abstract

Synthesis and encapsulation properties of two new water-soluble resorcinol-capped organic cavitands (tetra acid and octa acid; RTA and ROA) are reported in this Letter. Organic guest molecules template the formation of capsular assembly of the above cavitands in water. Depending upon the guest, either 1:2 (guest to host) or 2:2 capsular assemblies were formed. The excited state properties of guests such as anthracene, camphorthione, and 4,4'-dimethyl benzil were distinctly different within a capsular assembly from those when they were free in a solution. Importantly, the host-guest complexes of the above two hosts (RTA and ROA) as well as octa acid (OA) could be transferred to a silica surface. The excited state behavior of host-guest assemblies on silica surface resembled that in solution. The high cage effect in the decarbonylation products and high yield of rearrangement product obtained upon photolysis of 1-phenyl-3-tolyl-2-propanone included within RTA, ROA, and OA both in solution and on silica surface supported the conclusion that capsular assemblies of these hosts are stable on silica surface.

“Pointsource” Delivery of a Photosensitizer Drug and Singlet Oxygen: Eradication of Glioma Cells In Vitro

“…There was a kinetic likeness in the photorelease although the sigmoid was 7.7‐fold steeper in the n ‐butanol than the PBS. Silica surface properties and factors including greater solubility in n ‐butanol than PBS play key roles in the extent of the pheophorbide retention on the silica tip surface. The results were similar from internal irradiation (described here) vs external irradiation of the sensitizer solid, where increasing light intensity in the former was a correlation with, but not causation of the sigmoidal behavior.…”

Water-Soluble Cavitands ☆

“…85 In addition to serving as solution-based reaction vessels, these types of cavitands have been immobilized on silica surfaces 86 and appended to gold nanoparticles. For example, azidoadamantanes form stable 1:1 complexes with OA 37, which upon irradiation result in the corresponding nitrene complexes in which the guest inserts into one of the four benzyl hydrogens of the host.…”

Applications of supramolecular capsules derived from resorcin[4]arenes, calix[n]arenes and metallo-ligands: from biology to catalysis

“…128 They demonstrated that the properties of photo-reactor are maintained in the heterogeneous system, and that capsular assemblies are stable on silica surface.…”