A molecule that can be opened, closed, made to glow and even directed to form different products with different wavelengths of light could become a powerful building block for the next generation of smart materials. Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) have designed and synthesized a multifunctional molecular switch that responds reversibly to ultraviolet light while combining fluorescence, bistability, selective photochemical behavior and intrinsic chirality in a single compact structure.
The compound, described in a study published in Chemical Science, is based on dihydrobenzofuro[3,2-b]benzofuran, abbreviated as DHB. Its defining feature is a ring system that can exist in two stable structural states. When exposed to light with a wavelength of 285 nanometers, one carbon–oxygen bond breaks and the molecular ring opens. The resulting structure, referred to as B-OH, has different electronic properties from the closed form and emits fluorescence, making the molecular transformation readily detectable.
The process can be reversed using light at 325 nanometers. Under this longer-wavelength ultraviolet illumination, the open form undergoes a ring-closing reaction and returns to the original structure. This reversibility is central to the molecule’s potential as a molecular switch. Rather than undergoing a one-way decomposition, the compound can repeatedly move between two states in response to carefully selected light inputs, allowing information or chemical behavior to be controlled without physical contact.
At the molecular level, the two forms differ in the way their atoms are connected and how their electrons are distributed across the conjugated framework. In the closed state, the structure does not display the same fluorescence response as the open form. Once the carbon–oxygen bond is cleaved, the resulting B-OH species adopts an electronically distinct arrangement that can absorb and emit light more efficiently. This change in optical behavior provides a built-in signal: the molecule effectively reports its own structural state by switching its fluorescence on.
The researchers also found that the system is bistable, meaning that both the open and closed forms can persist as relatively stable states under appropriate conditions. Bistability is an important property for responsive materials because it allows a molecular device to retain a selected state instead of immediately relaxing back to its starting configuration. In a future material, this could help create light-controlled optical memories, molecular sensors or coatings that preserve information about a previous stimulus.
DHB adds another unusual feature to the design: intrinsic chirality. Chiral molecules exist in two mirror-image forms known as enantiomers. Although these enantiomers share the same chemical formula and many of the same conventional physical properties, they interact differently with circularly polarized light. The two DHB enantiomers showed opposite circular dichroism spectra, indicating that the molecules absorb left- and right-handed circularly polarized light differently. Circular dichroism, or CD, therefore provides a way to identify and study the molecule’s handedness as well as its light-driven structural behavior.
This combination of photochromism, fluorescence and chirality gives the molecular switch several independent optical signatures. Researchers can follow the ring-opening and ring-closing reactions through changes in absorption, monitor the open form through fluorescence and investigate the enantiomers using CD spectroscopy. Such complementary readouts are valuable in molecular engineering because they make it possible to distinguish not only whether a switch has changed state, but also which structural and chiral form is present.
The team demonstrated that the ring-opening reaction could be controlled directionally by modifying the molecule’s side groups. These substituents influence the electronic environment around the reactive portion of the scaffold and can alter how the photochemical process proceeds. By incorporating different side groups into the starting material, the researchers were able to selectively favor the formation of different products. This type of control could eventually allow light to guide chemical transformations along specific pathways rather than simply turning a single reaction on or off.
Understanding the switch required a broad combination of techniques. The researchers used organic synthesis to prepare the compounds, computational chemistry to examine their structures and possible reaction mechanisms, spectroscopy to follow their optical responses, and crystallography to determine molecular arrangements. Advanced characterization methods helped connect the observed fluorescence and CD signals with specific changes in bonding and geometry. According to the researchers, bringing these approaches together revealed how the molecule’s structure controls its switching mechanism and its optical properties.
The work reflects a wider effort to create materials that respond to external signals in ways inspired by biology. Living systems constantly convert environmental information into structural or functional changes, from electrically triggered activity in neurons to light-directed growth in plants. Synthetic molecular switches aim to reproduce some of this adaptability in nonliving materials. Unlike many biological systems, however, these compounds can be designed to respond to precise wavelengths, operate reversibly and be incorporated into engineered devices.
The researchers’ next step is to embed the molecular switches into larger polymers. A polymer containing many light-responsive units could amplify the behavior of an individual molecule, potentially producing changes in fluorescence, color, conductivity or mechanical properties across an entire material. Such systems might be useful in responsive surfaces, optical components, sensors, photonic devices and low-energy technologies in which light replaces electrical or chemical controls.
Several challenges remain before these applications become practical. Researchers will need to understand how the switch behaves when surrounded by neighboring polymer chains, whether the two states remain stable in a solid material and how efficiently the reactions can be repeated over many cycles. They will also need to control the wavelengths required for switching and determine how the molecular environment affects fluorescence and photochemical selectivity. Nevertheless, the new DHB platform demonstrates how one carefully engineered molecule can combine multiple functions that are often pursued separately.
By linking reversible bond breaking, fluorescence activation, product-selective photochemistry and chiral optical behavior, the OIST team has created more than a simple light-sensitive compound. The molecule acts as a compact laboratory for studying how structure, motion and optical response can be programmed at the nanoscale. If its properties can be transferred successfully into polymers and other larger materials, light-controlled molecular switches could help make future technologies more responsive, visually readable and energy efficient.
Subject of Research: Experimental study of a multifunctional, light-driven molecular switch with reversible ring opening and closing, fluorescence switching, bistability and intrinsic chirality.
Article Title: Dihydrobenzofuro[3,2-b]benzofuran: a light-driven molecular switch with fluorescence switching, bistability, and intrinsic chirality
News Publication Date: 20-Jul-2026
Web References: Okinawa Institute of Science and Technology Pi-Conjugated Polymers Unit: https://www.oist.jp/research/research-units/picpu ; DOI: https://doi.org/10.1039/d6sc04288k
References: Hassan et al., “Dihydrobenzofuro[3,2-b]benzofuran: a light-driven molecular switch with fluorescence switching, bistability, and intrinsic chirality,” Chemical Science, DOI: 10.1039/d6sc04288k.
Image Credits: Made by Fathy Hassan, using materials from Hassan et al., Chemical Science, 2026, DOI: 10.1039/d6sc04288k.
Keywords
Molecular switch, photochemistry, light-responsive materials, fluorescence switching, ring-opening reaction, ring-closing reaction, bistability, intrinsic chirality, circular dichroism, organic chemistry, molecular chemistry, polymer chemistry, photonic materials, OIST.
Tags: advanced molecular building blocksfluorescent bistable compoundsintrinsic molecular chiralityLight-activated molecular switcheslight-controlled electronic propertiesmultifunctional photoresponsive materialsnext-generation smart material designphotochemical behavior in molecular switchesphotochromic ring-opening and closingphotoresponsive smart materialsreversible UV-sensitive moleculesultraviolet light-induced structural transformation
