Search Results (55)

The development of photoactive molecules for photothermal energy storage is a focus of research in solar energy utilization technology. Azobenzene photoswitch has emerged as a promising candidate for solar energy conversion and storage due to its unique photoisomerization characteristics. Nonetheless, a majority of azobenzene-based molecular photothermal systems have a significant drawback: they depend on ultraviolet light for E-to-Z isomerization to store photon energy rather than visible light, which seriously hinders the development of azobenzene photoswitch in practical solar energy utilization applications. In this study, an azobenzene photothermal molecule that can effectively store visible-light photon energy was design and synthesized, which includes a tetra-ortho-chlorinated azo structure as the “head” part and an alkyl chain at para-position as the “tail” part. The ultraviolet–visible and ¹H NMR spectrum indicated that the obtained tetra-ortho-chlorinated azobenzene photothermal molecule could effectively absorb and store photon energy under 550 nm irradiation and release the stored energy upon 430 nm light irradiation. The storage energy density of the charged azobenzene photothermal molecule was determined to be 13.50 kJ/mol through differential scanning calorimetry and 28.21 kJ/mol via density functional theory theoretical calculations. This discrepancy was ascribed to the 64% Z-isomer yield harvesting during the charging process. Furthermore, the obtained tetra-ortho-chlorinated azobenzene exhibited long-term energy storage (approximately 11 days of half-life) and cyclic stability (100 cycles). Notably, the E-isomer of tetra-ortho-chlorinated azobenzene exhibited a high degree of supercooling, which may be advantageous for use in extremely low-temperature environments. Full article

The therapeutical applicability of the anticancer drug phototrexate, a photoswitchable derivative of the antimetabolite dihydrofolate reductase inhibitor methotrexate, highly depends on the stability of its bioactive isomer. Considering that only the cis configuration of phototrexate is bioactive, in this work, the effect of the molecular environment on the stability of the cis isomer of this drug has been investigated. UV-vis absorption and fluorescence-based solvent relaxation methods have been used. Protic methanol and non-protic dimethylsulfoxide were used as medium-ranged permittivity solvents. The results showed a decreased rate of cis → trans conversion and enhanced stabilities of the cis isomer in methanol. Temperature-dependent measurements of the isomerization rate reflect the increased activation energy in methanol. Full article

The reversible photo-induced conformation transition of a single molecule with a [5]helicene backbone has garnered considerable interest in recent studies. Based on such a switching process, one can build molecular photo-driven switches for potential applications of nanoelectronics. But the achievement of high-performance reversible single-molecule photoswitches is still rare. Here, we theoretically propose a 13,14-dimethylcethrene switch whose photoisomerization between the ring-closed and ring-open forms can be triggered by ultraviolet (UV) and visible light irradiation. The electronic structure transitions and charge transport characteristics, concurrent with the photo-driven electrocyclization of the molecule, are calculated by the non-equilibrium Green’s function (NEGF) in combination with density functional theory (DFT). The electrical conductivity bears great diversity between the closed and open configurations, certifying the switching behavior and leading to a maximum on–off ratio of up to 10³, which is considerable in organic junctions. Further analysis confirms the evident switching behaviors affected by the molecule–electrode interfaces in molecular junctions. Our findings are helpful for the rational design of organic photoswitches at the single-molecule level based on cethrene and analogous organic molecules. Full article

In recent years, significant advancements have been made in the research of photoswitchable probes. These probes undergo reversible structural and electronic changes upon light exposure, thus exhibiting vast potential in molecular detection, biological imaging, material science, and information storage. Through precisely engineered molecular structures, the photoswitchable probes can toggle between “on” and “off” states at specific wavelengths, enabling highly sensitive and selective detection of targeted analytes. This review systematically presents photoswitchable fluorescent and colorimetric probes built on various molecular photoswitches, primarily focusing on the types involving photoswitching in their detection and/or signal response processes. It begins with an analysis of various molecular photoswitches, including their photophysical properties, photoisomerization and photochromic mechanisms, and fundamental design concepts for constructing photoswitchable probes. The article then elaborates on the applications of these probes in detecting diverse targets, including cations, anions, small molecules, and biomacromolecules. Finally, it offers perspectives on the current state and future development of photoswitchable probes. This review aims to provide a clear introduction for researchers in the field and guidance for the design and application of new, efficient fluorescent and colorimetric probes. Full article

The study of fast non-equilibrium solvent relaxation in organic chromophores is still challenging for molecular modeling and simulation approaches, and is often overlooked, even in the case of non-adiabatic dynamics simulations. Yet, especially in the case of photoswitches, the interaction with the environment can strongly modulate the photophysical outcomes. To unravel such a delicate interplay, in the present contribution we resorted to a mixed quantum–classical approach, based on quantum mechanically derived force fields. The main task is to rationalize the solvent reorganization pathways in chromophores derived from cyclocurcumin, which are suitable for light-activated chemotherapy to destabilize cellular lipid membranes. The accurate and reliable decryption delivered by the quantum-derived force fields points to important differences in the solvent’s reorganization, in terms of both structure and time scale evolution. Full article

Significant research endeavors have been devoted to developing adhesives with reversible switching capabilities, allowing them to activate adhesion in response to diverse environmental stimuli. Among these, photo-switchable adhesives stand out as particularly promising. The presence of a photo-reversible solid-to-liquid transition, characterized by a transition temperature (T_SL), in certain azobenzene-containing polymers offers a compelling avenue for creating such adhesives. The development of a method based on Atomic Force Microscopy to measure both the glass transition temperature (T_g) and T_SL provided an opportunity to investigate the impact of various structural parameters on the solid-to-liquid transition of azopolymers. Our findings revealed that increasing the molecular weight (Mn) from 3400 to 8100 g/mol needed to achieve a highly cohesive adhesive resulted in an elevation in T_SL (>10 °C), making the solid-to-liquid transition at room temperature more challenging. However, incorporating a highly flexible substituent at the para position of the azobenzene group proved effective in significantly reducing the T_SL value (from 42 °C to 0 °C). This approach allows for the creation of photo-switchable adhesives with intriguing properties. We believe that our results establish a pathway toward developing a robust room-temperature photo-switchable adhesive. Full article

Diarylethene (DAE) molecular photoswitches draw attention as building units in the preparation of diverse photoactive molecules. An interesting class of these molecules are photoactive peptides. A way to build DAE moiety into peptides/peptidomimetics is via DAE amino acids, an example of which has been demonstrated in bioactive cyclic peptides, wherein the DAE Fmoc-amino acid was prepared and used. Herein, the preparation of DAE Boc-amino acid is presented using a modified method of synthesis. This contribution to the DAE amino acid collection could be useful in the further enhancement of diversity in designing different routes to photoactive peptides. Full article

Quantum dots (QDs) are emerging as promising candidates for innovative memristive materials, owing to their distinct surface, quantum size, and edge effects. Recent research has focused on tailoring QDs with specific organic molecules to fine-tune charge transfer states between the host and grafted species, as well as enhancing their dispersibility and processability. Violet phosphorus (VP), a newly discovered two-dimensional phosphorus allotrope, offers excellent carrier dynamics, predictable modifiability, and superior oxidation resistance, making it a promising contender in this domain. In this study, we synthesized a rich azobenzene-containing star-shaped polymer diazonium salt (AzoSPD) to functionalize violet phosphorus quantum dots (VPQDs), with the dual objectives of enhancing organic dispersibility and introducing photo-switching capabilities. The synthesized AzoSPD–VPQDs exhibit intramolecular charge transfer characteristics under electrical stimuli of ambient conditions, displaying significant non-volatile rewriteable memory properties and a substantial switching ratio exceeding 2 × 10³. Furthermore, the high resistance state (HRS) current can be enhanced by nearly 40 times under 465 nm illumination, enabling optoelectronic information sensing and storage within a single device. This work not only provides insights into enhancing the optoelectronic properties of QDs through functional organic molecular modification but also represents a pioneering exploration of the potential applications of VPQDs in novel memristors. Full article

The construction of multifunctional, single-molecule nanocircuits to achieve the miniaturization of active electronic devices is a challenging goal in molecular electronics. In this paper, we present an effective strategy for enhancing the multifunctionality and switching performance of diarylethene-based molecular devices, which exhibit photoswitchable rectification properties. Through a molecular engineering design, we systematically investigate a series of electron donor/acceptor-substituted diarylethene molecules to modulate the electronic properties and investigate the transport behaviors of the molecular junctions using the non-equilibrium Green’s function combined with the density functional theory. Our results demonstrate that the asymmetric configuration, substituted by both the donor and acceptor on the diarylethene molecule, exhibits the highest switching ratio and rectification ratio. Importantly, this rectification function can be switched on/off through the photoisomerization of the diarylethene unit. These modulations in the transport properties of these molecular junctions with different substituents were obtained with molecule-projected self-consistent Hamiltonian and bias-dependent transmission spectra. Furthermore, the current–voltage characteristics of these molecular junctions can be explained by the molecular energy level structure, showing the significance of energy level regulation. These findings have practical implications for constructing high-performance, multifunctional molecular-integrated circuits. Full article

Bioactive amines are highly relevant for clinical and industrial application to ensure the metabolic status of a biological process. Apart from this, generally, amine identification is a key step in various bioorganic processes ranging from protein chemistry to biomaterial fabrication. However, many amines have a negative impact on the environment and the excess intake of amines can have tremendous adverse health effects. Thus, easy, fast, sensitive, and reliable sensing methods for amine identification are strongly searched for. In the past few years, Meldrum’s acid furfural conjugate (MAFC) has been extensively explored as a starting material for the synthesis of photoswitchable donor–acceptor Stenhouse adducts (DASA). DASA formation hereby results from the rapid reaction of MAFC with primary and secondary amines, which has so far been demonstrated through numerous publications for different applications. The linear form of the MAFC-based DASA exhibits intense pink coloration due to its linear conjugated triene-2-ol conformation, which has inspired researchers to use this easy synthesizable molecule as an optical sensor for primary, secondary, and biogenic amines. Due to its new entry into amine identification, a collection of the literature exclusively on MAFC is demanded. In this mini review, we intend to present the state-of-the-art of MAFC as an optical molecular sensor in hopes to motivate researchers to find even more applications of MAFC-based sensors and methods that pave the way to their usage in medicinal applications. Full article

Glutamate ionotropic receptors mediate fast excitation processes in the central nervous system of vertebrates and play an important role in synaptic plasticity, learning, and memory. Here, we describe the action of two azobenene-containing compounds, AAQ (acrylamide–azobenzene–quaternary ammonium) and QAQ (quaternary ammonium–azobenzene–quaternary ammonium), which produced rapid and fully reversible light-dependent inhibition of glutamate ionotropic receptors. The compounds demonstrated voltage-dependent inhibition with only minor voltage-independent allosteric action. Calcium-impermeable AMPA receptors had weaker sensitivity compared to NMDA and calcium-permeable AMPA receptors. We further revealed that the compounds bound to NMDA and calcium-permeable AMPA receptors in different modes. They were able to enter the wide selectivity filter of AMPA receptors, and strong negative voltages caused permeation into the cytoplasm. The narrow selectivity filter of the NMDA receptors did not allow the molecules to bypass them; therefore, QAQ and AAQ bound to the shallow channel site and prevented channel closure by a foot-in-the-door mechanism. Computer simulations employing available AMPA and NMDA receptor structures readily reproduced the experimental findings, allowing for the structure-based design of more potent and selective drugs in the future. Thus, our work creates a framework for the development of light-sensitive blockers of calcium-permeable AMPA receptors, which are desirable tools for neuroscience. Full article

Switchable nonlinear optical (NLO) materials have widespread applications in electronics and optoelectronics. Thermo-switches generate many times higher NLO responses as compared to photo-switches. Herein, we have investigated the geometric, electronic, and nonlinear optical properties of spiropyranes thermochromes via DFT methods. The stabilities of close and open isomers of selected spiropyranes are investigated through relative energies. Electronic properties are studied through frontier molecular orbitals (FMOs) analysis. The lower HOMO-LUMO energy gap and lower excitation energy are observed for open isomers of spiropyranes, which imparts the large first hyperpolarizability value. The delocalization of π-electrons, asymmetric distribution and elongated conjugation system are dominant factors for high hyperpolarizability values of open isomers. For deep understanding, we also analyzed the frequency-dependent hyperpolarizability and refractive index of considered thermochromes. The NLO response increased significantly with increasing frequency. Among all those compounds, the highest refractive index value is observed for the open isomer of the spiropyran 1 (1.99 × 10⁻¹⁷ cm²/W). Molecular absorption analysis confirmed the electronic excitation in the open isomers compared to closed isomers. The results show that reversible thermochromic compounds act as excellent NLO molecular switches and can be used to design advanced electronics. Full article

Carbohydrate-based low-molecular-weight gelators are interesting new materials with many potential applications. These compounds can be designed to include multiple stimuli-responsive functional groups. In this study, we designed and synthesized several chemically responsive bola-glycolipids and dimeric carbohydrate- and diarylethene-based photoswitchable derivatives. The dimeric glycolipids formed stable gels in a variety of solvent systems. The best performing gelators in this series contained decanedioic and dithienylethene (DTE) spacers, which formed gels in eight and nine of the tested solvents, respectively. The two new DTE-containing esters possessed interesting photoswitching properties and DTE derivative 7 was found to have versatile gelation properties in many solvents, including DMSO solutions at low concentrations. The gels formed by these compounds were stable under acidic conditions and tended to hydrolyze under basic conditions. Several gels were used to absorb rhodamine B and Toluidine blue from aqueous solutions. In this study, we demonstrated the rational design of molecular gelators which incorporated photoresponsive and pH responsive functions, leading to the discovery of multiple effective stimuli-responsive gelators. Full article

The first-, second-, and third-order molecular nonlinear optical properties, including two-photon absorption of a series of derivatives, involving two dithienylethene (DTE) groups connected by several molecular linkers (bis(ethylene-1,2-dithiolato)Ni- (NiBDT), naphthalene, quasilinear oligothiophene chains), are investigated by employing density functional theory (DFT). These properties can be efficiently controlled by DTE switches, in connection with light of appropriate frequency. NiBDT, as a linker, is associated with a greater contrast, in comparison to naphthalene, between the first and second hyperpolarizabilities of the “open–open” and the “closed–closed” isomers. This is explained by invoking the low-lying excited states of NiBDT. It is shown that the second hyperpolarizability can be used as an index, which follows the structural changes induced by photochromism. Assuming a Förster type transfer mechanism, the intramolecular excited-state energy transfer (EET) mechanism is studied. Two important parameters related to this are computed: the electronic coupling (V_DA) between the donor and acceptor fragments as well as the overlap between the absorption and emission spectra of the donor and acceptor groups. NiBDT as a linker is associated with a low electronic coupling, V_DA, value. We found that V_DA is affected by molecular geometry. Our results predict that the linker strongly influences the communication between the open–closed DTE groups. The sensitivity of the molecular nonlinear optical properties could assist with identification of molecular isomers. Full article

The potential of E–Z photoisomerization in molecular organic light-to-thermal conversion and storage in an E–styryl merocyanine system was studied in a polar acidic medium. A photoswitchable styryl merocyanine dye (E)-2-(2-(2-hydroxynaphthalen-1-yl)vinyl)-3,5-dimethylbenzo[d]thiazol-3-ium iodide was synthesized for the first time. The reversible E–Z photoisomerisation of the dye was investigated using UV-Vis spectroscopy and DFT calculations. E–Z isomerization was induced through the use of visible light irradiation (λ = 450 nm). The obtained experimental and theoretical results confirm the applicability of the Z and E isomers for proton-triggered light harvesting. Full article