Steering the Ultrafast Opening and Closure Dynamics of a Photochromic Coordination Cage by Guest Molecules

Abstract

Photochemical studies on supramolecular hosts that can encapsulate small guest molecules commonly focus on three aspects: photoswitching the cage to release or trap the guest, the effect of the confining environment on the guest, and light-induced exciton or charge transfer within the cage structure. Here, we exploit ultrafast spectroscopy to address how the guest alters the photoswitching characteristics of the cage. For this, the impacts of three disparate guest compounds on ring-opening or ring-closure of a dithienylethene (DTE) ligand in a photoswitchable DTEbased coordination cage are juxtaposed. The guest modulates both outcome and timescale of the cage's photodynamics, by an interplay of structural strain, heavy-atom effect, and enhancement of charge-transfer processes exercised by the guest on the photo-excited cage. The approach might prove beneficial for attuning the applicability of photoswitchable nanocontainers and desired guest compounds.

Molecular Cage with Dual Outputs of Photochromism and Luminescence Both in Solution and the Solid State

“…Photochromic materials undergoing reversibly structural transformations in response to light stimuli can display distinct photochemical and photophysical properties under different circumstances. Compared to other stimuli-responsive materials, − this class of photoactive compounds have unique advantages, such as contactless control and quick responsiveness, which have enabled their wide applications such as in photoresponsive materials, − biomedical materials, − and supramolecular materials. − …”

Multiple Flexibilities Trigger Luminescent Piezochromism of Closely Packed Cu(I) Coordination Polymers

“…The luminescence or apparent colors of probe molecules display response to the external stimuli such as light, [1,2] heat, [3] pressures, [4,5] gases, [6,7] solvents, [8,9] and so on, which is strongly related to the structural change and charge/electron transfer in the response process. [10][11][12] Especially, for compounds with piezochromic property, applied pressure affects the molecular packing and conformation of the materials, usually resulting in the redshift or quenching luminescence.…”

Crystal Engineering of Two Light and Pressure Responsive Physisorbents

“…This has previously been attempted through photochromic guests in framework cavities, [25] linker ligands with pendant AB or BTCP sidearms [19,20] or grafting of such moieties into either cages or framework backbones. [33][34][35][36][37][38][39][40] Although the latter category has the potential to produce the most pronounced structural changes, tethering reduces conformational freedom and mobility, requiring judicious linker selection (BTCP ligands are thus more optimal than AB ligands). Nevertheless, of the 58 ring-closed BTCP structures reported in the Cambridge Structural Database (CSD), [41] only two entries are porous sorbents wherein BTCP was used to modulate gas sorption.…”