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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. 

Thiocarbonyls exhibit unique photophysical properties, characterized by rapid intersystem crossing (ISC) due to favorable singlet−triplet energetics and enhanced spin−orbit coupling. However, the role of hydrogen bonding in modulating the ISC remains underexplored. This study investigates the effect of solvent−solute hydrogen bonding on the ISC dynamics of 7-(diethylamino)-4- methyl-2-sulfanylidene-2H-chromen-2-one (thiocoumarin 1, TC1) using steadystate and time-resolved spectroscopy, complemented by theoretical calculations. Experimental data reveal that in methanol, hydrogen bonding leads to increased fluorescence quantum yield, prolonged singlet-state lifetime, and reduced triplet yield compared to aprotic acetonitrile. Time-resolved spectroscopy identifies an additional long-lived emissive singlet state in methanol, attributed to a hydrogen-bonded state, which slows ISC. Theoretical calculations demonstrate that hydrogen bonding alters the electronic structure and constrains ISC along key nuclear coordinates, including the C S bond vibration and dihedral angles, leading to decreased triplet formation. These findings provide mechanistic insights into hydrogen-bonding-mediated control of ISC in thiocoumarins, with implications for designing functional materials with tunable photophysical properties. 

Evaporative misters have long been used in urban spaces for heat mitigation, yet their thermal stress impacts and optimal operating conditions have not been fully explored. To fill this gap, we develop a misting model and embed it into an urban canopy model for the first time. Our tests confirm that misters can considerably reduce maximum urban canyon air temperature (up to 17.5 °C) and human skin temperature (up to 0.48 °C) in a hot and dry city (Phoenix, AZ). They continue to effectively reduce thermal stress, albeit with half of the cooling benefits, in a hot and humid city (Houston, TX). These thermal stress impacts are contingent upon wind speeds: the optimal wind speeds generally fall within an intermediate range—from light air (with low mist flow rates) to a moderate breeze (with higher mist flow rates). We then incorporate misting into a broader comparison of blue cooling strategies, including irrigation (on vegetation) and sprinkling (on pavements). With abundant water resources, sprinkling on asphalt and misting are the most effective cooling solutions, particularly suitable for middays and late afternoons, respectively. To balance cooling benefits with limited water resources, we propose a thermostatic control scheme that can save at least 10.5 m3/day of water compared to continuous misting for a 100-m stretch of street, equivalent to the water demand of about 20 Phoenix residents. Notably, misting and sprinkling generate rapid cooling in under 10 min with sufficient flow rates, demonstrating their potential as fast activation measures during extreme heat emergencies. 

ndene, a hydrophobic molecule, exhibits complex behavior in water due to its tendency to aggregate. This study combines NMR spectroscopy, molecular dynamics simulations, and ab initio calculations to investigate indene’s dynamic interactions with monomeric and aggregated states. NMR results reveal dynamic chemical exchange between monomer and aggregate states, and further studies show a preferential aggregation pathway akin to Ostwald ripening. Molecular dynamics simulations provide insights into indene behavior in water and acetonitrile, with a pronounced preference for aggregation in water. Geometry optimization and thermochemistry calculations reveal the formation of stable dimers, with water favoring aggregation energetically. These findings advance our understanding of hydrophobic molecule behavior in water and have implications for organic compound–aqueous environment interactions and photochemistry research. 

We deconvolute the distinct and sometimes competing effects of geometric and material chirality in metastructures created from materials that are intrinsically chiral. We find that overlapping Mie-like resonances in nanodisk arrays leads to 6-fold CD enhancement compared to a uniform film. Furthermore, making the medium chiral does not necessarily increase CD; enhancement depends on the magnitude of the Pasteur parameter and its real and imaginary components. Finally, to demonstrate how geometric and material chirality can be combined, we design a geometrically chiral meta-atom out of chiral media and observe over 9-fold enhancement in both CD andg-factor compared to a metasurface comprised of achiral material. 

Water is an under-appreciated reaction medium that has been shown to facilitate photodimerization reactions. Despite having a low formal concentration, hydrophobic nature of organic compounds could lead to higher local concentrations, thereby favoring their cycloaddition. In contrast, photodimerization reactions are unlikely to occur in organic solvents under similar conditions. This study explores the supramolecular assembly of small organic molecules in water, focusing on their role in promoting photodimerization reactions. NMR spectroscopy, molecular dynamics simulations, and ab initio calculations were used to examine the dynamic interactions between indene and its aggregated state in water. Quantum mechanical calculations suggest that the stacking of indene with an antiparallel-displaced orientation is the most stable configuration, and MD simulations support the role of water in promoting aggregation. NMR results confirm the existence of indene aggregates, and 2D NMR reveals dynamic exchange between monomer and aggregate states. The study elucidates the complex dynamics of indene aggregation and its impact on photodimerization, providing insights into designing other photoreactions in water.