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Merocyanines (MC) usually adopt ring opened zwitterionic structures that are interconvertible with their ring‐closed spiropyran photoisomers. By methylating the phenolate oxygen, and thereby blocking the ring‐closure reaction, a cis/trans‐only MC photoswitch was obtained, yielding a perfect candidate for a detailed examination of the cis/trans isomerization mechanism for this class of compounds. This photoswitch displays outstanding properties including excellent photoreaction quantum yields and photoswitching turnovers. Due to the central polymethine bridge of MC, in principle eight cis (C)/trans/(T) isomers are possible. Density Functional Theory (DFT) calculations revealed the CCT and TTT‐isomers of the studied compound as most stable cis and trans ground state isomers, respectively. UV/vis transient absorption studies combined with conical intersection computations with the complete active space self‐consistent field (CASSCF) method show that both trans/cis‐ and cis/trans‐photoisomerizations are initiated by a rotation of the central doubled bond fragment. A hot ground state species is then formed, which undergoes a second isomerization. Thus, the cis/trans reaction proceeds via a CCT‐CTT‐TTT sequence and the reverse reaction via TTT‐TCT‐CCT. [ABSTRACT FROM AUTHOR]

Herein, we report a tri‐component photochromic molecular cocktail that can be used to encrypt and decrypt information. The time‐dependent fluorescent response of this cocktail is highly non‐linear with respect to the set of inputs used (concentrations of the three photochromic components, excitation‐ and emission wavelengths), a property required for the generation of so‐called encryption keys. The all‐optical system can generate more than 80 million unique fluorescence responses by applying different input combinations and is operated using a conventional fluorimeter. [ABSTRACT FROM AUTHOR]

Green‐to‐blue triplet–triplet annihilation photon upconversion with the well‐studied upconversion pair 9,10‐diphenylanthracene (DPA)/platinum octaethylporphyrin (PtOEP) was used to reversibly drive the photoisomerization of diarylethene (DAE) photoswitches by using visible light. By carefully selecting the kinetic and spectral properties of the molecular system as well as the experimental geometry, a single green light source can be used to selectively trigger both the ring‐opening and the ring‐closing reactions, whilst also inducing fluorescence from the colored closed isomer that can be used as a readout to monitor the isomerization process in situ. The upconversion solution and the DAE solution are kept physically separated, allowing them to be characterized both concomitantly and individually without further separation processes. The ring‐closing reaction using upconverted photons was quantified and compared to the efficiency of direct isomerization with ultraviolet light. [ABSTRACT FROM AUTHOR]

Two amidine-substituted spiropyran derivatives have been characterized with respect to the DNA-binding properties over a broad pH interval. The two derivatives differ in the number of positive charges. By varying the pH, the protonation state of the derivatives is also changed, allowing for additional variations in the charge distribution. We show that the closed spiro isomer does not bind for either of the two derivatives, whereas the open merocyanine forms bind both in the protonated and in the nonprotonated state, but with dramatically different binding constants. Flow-oriented linear dichroism (LD) measurements also show that there are differences in the binding modes between the various forms. We rationalize these differences in terms of structure and charge distribution. [ABSTRACT FROM AUTHOR]

• Light is used for operating (supra)molecular logic devices in all-photonic mode. • Light enables spatiotemporal control, recycling, and logic reconfiguration. • Multiphotochromic platforms raise the complexity level of logic operations. • Photoswitches are integrated in supramolecular assemblies for information processing. In this Review the use of light to address stimuli-responsive molecular and supramolecular systems with applications in information processing and binary logic is discussed. Molecular photoswitches are at the focal point of the herein summarized works. Light offers great advantages in terms of spatiotemporal control and remote triggering. As an additional surplus, excited state processes, such as energy- and electron-transfer can be precisely designed such that photoswitchable systems yield the desired logic operation or function. As opposed to chemical signals, photons are traceless reagents, enabling the recycled operation and reconfiguration of the discussed devices. The herein in an account-style summarized examples provide an overview of merging photoswitching with information processing, hopefully serving as a starting point for further research in this exciting field. [ABSTRACT FROM AUTHOR]

A series of photochromic diarylmaleimide derivatives has been synthesized and studied with respect to the photochromic properties in aqueous solution. The main rationale is to investigate if these compounds could be used as photoswitchable units in biological contexts, motivated by the fact that the diarylmaleimide structural motif is identified in many pharmacophores. Thus, photoswitchable variants of this class of compounds could be very useful in the quest for photoactivatable drugs. The photoinduced cyclization reaction (colorization) is suppressed in solvents of high polarity, whereas the ring-opening reaction (decolorization) still occurs with high efficiency. The photochromically active anti-parallel conformer of the open form is more abundant in the asymmetrically substituted derivatives, which in turn favors the formation of the closed isomeric form. The rates of the thermal isomerization reactions have also been assessed, together with the resistance toward thermal degradation. Here it was observed that the maleimide derived compounds were not susceptible to the thermally driven reactions (hydrolysis and isomerization). [ABSTRACT FROM AUTHOR]