Taking Photochromism beyond Visible: Direct One‐Photon NIR Photoswitches Operating in the Biological Window

Abstract

The success of photopharmacology is inevitably tied to the availability of photoswitches, which can be operated within the biological window (λ=650-1450 nm) to maximize penetration in tissue. A general design strategy has been devised and a dihydropyrene derivative is described here that displays negative T-type photochromism, allowing for efficient and nearly quantitative (95 %) switching induced by NIR light λ>800 nm. The thermal half-life of the decolored ring-open meta-cyclophanediene isomer ranges from minutes to hours, depending on the solvent polarity and hence serves as a probe of the local environment. Due to the rather subtle geometrical differences between the two isomers, suitably modified NIR photoswitches are potential candidates for switching when bound in the pocket of the biological target, in principle allowing for reversible light-induced inhibitor deactivation as an alternative approach to externally regulate biological functions.

Nature‐Inspired Emerging Chiral Liquid Crystal Nanostructures: From Molecular Self‐Assembly to DNA Mesophase and Nanocolloids

“…Many researches focus on the development of photoresponsive molecules that can be driven with light irradiations at a longer wavelength. [184][185][186][187] We have achieved reversible visible-lightdriven dynamic tuning of RGB reflection color in cholesteric LCs by designing a novel light-driven chiral azobenzene molecular photoswitch with extended conjugation. [188] After that we looked toward the possibility of dynamic reflection tuning of cholesteric superstructures by remote NIR irradiation.…”

The Many Ways to Assemble Nanoparticles Using Light

“…In principle, all of the approaches described above are applicable to NPs of other shapes, such as cubes and 2D prisms. Second, the recent years have seen the development of a plethora of new photochromic systems, some of which have significantly improved switching characteristics, such as the greatly increased thermal half‐lives of the metastable state and the ability to switch using red or NIR light. The ability to control NP self‐assembly using these and other new molecular switches remains to be investigated.…”

Designing Molecular Photoswitches for Soft Materials Applications

“…DHPs are another type of photoswitch, which is intrinsically negative photochromic. Recently, we have been able to develop such negative photochromic DHP switches that can be addressed by NIR light ( Figure ) . In the ring‐closed isomer, donor and acceptor groups are conjugated over the aromatic 14π‐electron system and the resulting quinoid resonance structure gives rise to an intense long‐wavelength charge‐transfer (CT) band, which tails out beyond 800 nm in various organic solvents.…”

“…Negative photochromic donor–acceptor–DHP addressable by NIR light. Reproduced with permission . Copyright 2018, Wiley‐VCH.…”