Abstract A new design strategy to control the efficiency of a photocleavage reaction based on changing the nature of the excited state is presented. A novel class of photoactive compounds has been synthesized by combining the classical o ‐nitrobenzyl scaffold with an environmentally sensitive dye, 4‐amino‐nitrobenzothiazole. Irradiation in a polar solvent led to an excited state that was inoperative for photochemistry whereas excitation in a nonpolar solvent led to an excited state that was photochemically active. While our design hypothesis tests true for the on/off control of a photochemical process, an alternative photochemical ring‐opening of the heterocycle appears to be the preferred process in contrast to the intended photocleavage process.
Self-assembled monolayers are predicated on thermodynamic equilibrium; hence, their properties project accessible relaxation pathways. Herein, we demonstrate that charge tunneling correlates with conformational degrees of freedom(s). Results from open chain and cyclic head groups show that, as expected, distribution in tunneling data correlates with the orientation of the head group, akin to the odd–even effect and more importantly the degree of conformational freedom, but fluctuates with applied bias. Trends in nature of distributions in current density illuminate the need for higher statistical moments in understanding these rather dynamic systems. We employ skewness, kurtosis, and estimation plots to show that the conformational degree of freedom in the head group significantly amplifies the odd–even effect and may lead to enhanced or perturbed tunneling based on whether the head group is on an odd- or even-parity spacer.
A new class of push–pull dyes based on the reactive isobenzofuran core have been synthesized. The new dyes have a smaller HOMO–LUMO gap than a related class of dyes based on benzofurazan and allow for isolation of structural factors that contribute to environmental sensitivity. Experimental and theoretical evidence implicate different photophysical processes are responsible for a reversal of emissive behavior that is observed between isobenzofuran and benzofurazan analogues.
An unexpected nucleophilic aromatic substitution lead to a novel benzothiadiazole scaffold that bore the functional group pattern associated with benzyl-type photocleavable protecting groups. The new molecules display efficient photochemical release of leaving groups with blue light. The performance of both ortho- and meta-substituted derivatives was probed through both structural manipulation and computational metrics to improve performance.
Differentiation of heterocyclic isomers by solution 1H, 13C, and 15N NMR spectroscopy is often challenging due to similarities in their spectroscopic signatures. Here, 13C{14N} solid-state NMR spectroscopy experiments are shown to operate as an "attached nitrogen test", where heterocyclic isomers are easy to distinguish based on one-dimensional nitrogen-filtered 13C solid-state NMR. We anticipate that these NMR experiments will facilitate the assignment of heterocyclic isomers during synthesis and natural product discovery.
