Synthesis and Photophysical Characterization of Azoheteroarenes

A set of azoheteroarenes have been synthesized with Buchwald–Hartwig coupling and microwave-assisted O₂ oxidation as the key steps. Several compounds exhibit good to excellent photoswitching properties (high switching efficiency, good fatigue resistance, and thermal stability of <i>Z</i>-isomer) relevant for photocontrolled applications, which pave the way for use in photopharmacology

Interactions of a Photochromic Spiropyran with Liposome Model Membranes

The interactions between anionic or zwitterionic liposomes and a water-soluble, DNA-binding photochromic spiropyran are studied using UV/vis absorption and linear dichroism (LD) spectroscopy. The spectral characteristics as well as the kinetics of the thermal isomerization process in the absence and presence of the two different liposome types provide information about the environment and whether or not the spiropyran resides in the liposome membrane. By measuring LD on liposomes deformed and aligned by shear flow, further insight is obtained about interaction and binding geometry of the spiropyran at the lipid membranes. We show that the membrane interactions differ between the two types of liposomes used as well as the isomeric forms of the spiropyran photoswitch

The Open and Closed Forms of a Perfluoro Diarylethene PhotoswitchHalogen Bonding, Network Topology, and CSD Analysis

The structure of the perfluoro cyclopentene diarylethene photoswitch 3,3′-(perfluorocyclopent-1-ene-1,2-diyl)bis(2-ethyl-6-iodobenzo[b]thiophene 1,1-dioxide) (C25H16F6I2O4S2) 1 at 100 K has a tetragonal (I41/a) symmetry. The compound has a halogen-bonded network structure described by the uninodal five-connected joa net. This net is related to another uninodal six-connected net sfo. Analysis using the Cambridge Structural Database (CSD) shows that the majority of structures with the perfluoro cyclopentene diarylethene motif, >85%, have a C···C distance of around 3.5 Å where a new single bond will develop during photoswitching, whereas compound 1 falls in a second smaller category with C···C distances of around 4.2 Å. The photochemical reaction of 1 under UV light in ethanol gave a closed form that crystallized as ethanol solvate 2a in the P21/c space group, and recrystallization in acetone gave the nonsolvated form 2b crystallizing in the space group Fdd2. We did not observe, and do not believe that it is possible, to photoswitch 1 in the solid state as the C···C distance where a new single bond will develop is very long

An All-Photonic Molecule-Based D Flip-Flop

The photochromic fluorescence switching of a fulgimide derivative was used to implement the first molecule-based D (<i>delay</i>) flip-flop device, which works based on the principles of sequential logic. The device operates exclusively with photonic signals and can be conveniently switched in repeated cycles

Characterization of the Thermal and Photoinduced Reactions of Photochromic Spiropyrans in Aqueous Solution

Six water-soluble spiropyran derivatives have been characterized with respect to the thermal and photoinduced reactions over a broad pH-interval. A comprehensive kinetic model was formulated including the spiro- and the merocyanine isomers, the respective protonated forms, and the hydrolysis products. The experimental studies on the hydrolysis reaction mechanism were supplemented by calculations using quantum mechanical (QM) models employing density functional theory. The results show that (1) the substitution pattern dramatically influences the p<i>K</i>_a-values of the protonated forms as well as the rates of the thermal isomerization reactions, (2) water is the nucleophile in the hydrolysis reaction around neutral pH, (3) the phenolate oxygen of the merocyanine form plays a key role in the hydrolysis reaction. Hence, the nonprotonated merocyanine isomer is susceptible to hydrolysis, whereas the corresponding protonated form is stable toward hydrolytic degradation

An All-Photonic Molecule-Based Parity Generator/Checker for Error Detection in Data Transmission

The function of a parity generator/checker, which is an essential operation for detecting errors in data transmission, has been realized with multiphotochromic switches by taking advantage of a neuron-like fluorescence response and reversible light-induced transformations between the implicated isomers

Optically Switchable NIR Photoluminescence of PbS Semiconducting Nanocrystals using Diarylethene Photoswitches

Precisely modulated photoluminescence (PL) with external control is highly demanded in material and biological sciences. However, it is challenging to switch the PL on and off in the NIR region with a high modulation contrast. Here, we demonstrate that reversible on and off switching of the PL in the NIR region can be achieved in a bicomponent system comprised of PbS semiconducting nanocrystals (NCs) and diarylethene (DAE) photoswitches. Photoisomerization of DAE to the ring-closed form upon UV light irradiation causes substantial quenching of the NIR PL of PbS NCs due to efficient triplet energy transfer. The NIR PL fully recovers to an on state upon reversing the photoisomerization of DAE to the ring-open form with green light irradiation. Importantly, fully reversible switching occurs without obvious fatigue, and the high PL on/off ratio (>100) outperforms all previously reported assemblies of NCs and photoswitches

OFF-ON-OFF Fluorescence Switch with T-Latch Function

A novel molecular system with characteristics of an OFF-ON-OFF fluorescence switch was designed to integrate the function of a T-latch. In detail, a receptor₁-fluorophore-receptor₂ architecture was adopted to achieve fluorescence switching upon addition of protons

All-Photonic Multifunctional Molecular Logic Device

Photochromes are photoswitchable, bistable chromophores which, like transistors, can implement binary logic operations. When several photochromes are combined in one molecule, interactions between them such as energy and electron transfer allow design of simple Boolean logic gates and more complex logic devices with all-photonic inputs and outputs. Selective isomerization of individual photochromes can be achieved using light of different wavelengths, and logic outputs can employ absorption and emission properties at different wavelengths, thus allowing a single molecular species to perform several different functions, even simultaneously. Here, we report a molecule consisting of three linked photochromes that can be configured as AND, XOR, INH, half-adder, half-subtractor, multiplexer, demultiplexer, encoder, decoder, keypad lock, and logically reversible transfer gate logic devices, all with a common initial state. The system demonstrates the advantages of light-responsive molecules as multifunctional, reconfigurable nanoscale logic devices that represent an approach to true molecular information processing units

Dynamic and Progressive Control of DNA Origami Conformation by Modulating DNA Helicity with Chemical Adducts

DNA origami has received enormous attention for its ability to program complex nanostructures with a few nanometer precision. Dynamic origami structures that change conformation in response to environmental cues or external signals hold great promises in sensing and actuation at the nanoscale. The reconfiguration mechanism of existing dynamic origami structures is mostly limited to single-stranded hinges and relies almost exclusively on DNA hybridization or strand displacement. Here, we show an alternative approach by demonstrating on-demand conformation changes with DNA-binding molecules, which intercalate between base pairs and unwind DNA double helices. The unwinding effect modulates the helicity mismatch in DNA origami, which significantly influences the internal stress and the global conformation of the origami structure. We demonstrate the switching of a polymerized origami nanoribbon between different twisting states and a well-constrained torsional deformation in a monomeric origami shaft. The structural transformation is shown to be reversible, and binding isotherms confirm the reconfiguration mechanism. This approach provides a rapid and reversible means to change DNA origami conformation, which can be used for dynamic and progressive control at the nanoscale