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Impaired expression of GABA transporters (GATs) is closely related to the pathogenesis of among others Parkinson's disease and epilepsy. As such, lipophilic nipecotic acid analogs have been extensively studied as GAT1-addressing drugs and radioligands but suffer from limited brain uptake due to the zwitterionic properties of the nipecotic acid moiety. Bioisosteric replacement of the carboxylic acid group is a promising strategy to improve the brain uptake, though it requires knowledge on the binding of these isosteres to GAT1. To screen nipecotic acid isosteres for their affinity to GAT1 in a time- and cost-effective manner, this research aims to develop a molecular imprinted polymer (MIP) that mimics the natural binding site of GAT1 and can act as an alternative screening tool to the current radiometric and mass spectrometry cellular-based assays. To this end, a nipecotic acid MIP was created using the electropolymerization of ortho-phenylenediamine (oPD) by cyclic voltammetry (CV). The optimization of the generated receptor layer was achieved by varying the scan rate (50-250 mV/s) and number of CV cycles (5-12), yielding an optimized MIP with an average imprinting factor of 2.6, a linear range of 1-1000 nm, and a theoretical LOD of 0.05 nm, as analyzed by electrical impedance spectroscopy (EIS). Selectivity studies facilitated the investigation of major binding interactions between the MIP and the substrate, building an experimental model that compares characteristics of various analogs. Results from this model indicate that the substrate carboxylic acid group plays a more important role in binding than an amine group, after comparing the binding of cyclohexanecarboxylic acid (average IF of 1.7) and piperidine (average IF of 0.46). The research culminates in a discussion regarding the feasibility of the in vitro model, comparing the synthetic system against the biological performance of GAT1. Thus, evaluating if it is possible to generate a synthetic GAT1 mimic, and if so, provide directions for follow-up research., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Chemical reduction of a vertically expanded pentacene, TIPS- peri -pentacenopentacene (TIPS-PPP), with sodium metal in THF readily afforded a doubly-reduced product isolated as [{Na + (THF) 3 } 2 (TIPS-PPP2-)]. Single-crystal X-ray diffraction revealed the formation of a π-complex of TIPS-PPP2- with two {Na + (THF) 3 } moieties. The sodium ion is coordinated to three C-atoms at the most negatively charged edge sites and at the lateral ethynyl group. The delocalisation of the charge on the ethynyl function is accompanied by its notable elongation ( Δ = 0.015 Å) coupled with the contraction of the adjacent single C-C bond ( Δ = 0.033 Å). Bond length analysis supported by Harmonic Aromaticity Oscillator Model (HOMA) shows that the dianion can be written with four aromatic sextets in agreement with the Clar representation. Although TIPS-PPP2- has 36 π-electrons (4 n ), it does not show a global magnetic paratropic response. The rings with the most negative charge density have a very low paratropic response, while the other rings have a low diatropic response. Overall, the dianion is a non-aromatic molecule.

Antimicrobial resistance (AMR) poses a significant threat to global health, powered by pathogens that become increasingly proficient at withstanding antibiotic treatments. This review introduces the factors contributing to antimicrobial resistance (AMR), highlighting the presence of antibiotics in different environmental and biological matrices as a significant contributor to the resistance. It emphasizes the urgent need for robust and effective detection methods to identify these substances and mitigate their impact on AMR. Traditional techniques, such as liquid chromatography-mass spectrometry (LC-MS) and immunoassays, are discussed alongside their limitations. The review underscores the emerging role of biosensors as promising alternatives for antibiotic detection, with a particular focus on electrochemical biosensors. Therefore, the manuscript extensively explores the principles and various types of electrochemical biosensors, elucidating their advantages, including high sensitivity, rapid response, and potential for point-of-care applications. Moreover, the manuscript investigates recent advances in materials used to fabricate electrochemical platforms for antibiotic detection, such as aptamers and molecularly imprinted polymers, highlighting their role in enhancing sensor performance and selectivity. This review culminates with an evaluation and summary of commercially available and spin-off sensors for antibiotic detection, emphasizing their versatility and portability. By explaining the landscape, role, and future outlook of electrochemical biosensors in antibiotic detection, this review provides insights into the ongoing efforts to combat the escalating threat of AMR effectively.

Pseudomonas aeruginosa is a multidrug-resistant Gram-negative bacterium that poses a significant threat to public health, necessitating rapid and on-site detection methods for rapid recognition. The goal of the project is therefore to indirectly detect the presence of P. aeruginosa in environmental water samples targeting one of its quorum-sensing molecules, namely, ( S )- N -butyryl homoserine lactone (BHL). To this aim, molecularly imprinted polymers (MIPs) were synthesized via bulk free-radical polymerization using BHL as a template molecule. The obtained MIP particles were immobilized onto screen-printed electrodes (MIP-SPEs), and the BHL rebinding was analyzed via electrochemical impedance spectroscopy (EIS). To study the specificity of the synthesized MIPs, isotherm curves were built after on-point rebinding analysis performed via LC-MS measurements for both MIPs and NIPs (nonimprinted polymers, used as a negative control), obtaining an imprinting factor (IF) of 2.8 (at C f = 0.4 mM). The MIP-SPEs were integrated into an electrochemical biosensor with a linear range of 1 × 10 1 -1 × 10 3 nM and a limit of detection (LoD) of 31.78 ± 4.08 nM. Selectivity measurements were also performed after choosing specific interferent molecules, such as structural analogs and potential interferents, followed by on-point analysis performed in spiked tap water to prove the sensor's potential to detect the presence of the quorum-sensing molecule in environmentally related real-life samples., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Ensuring a rapid and accurate identification of harmful bacteria is crucial in various fields including environmental monitoring, food safety, and clinical diagnostics. Conventional detection methods often suffer from limitations such as long analysis time, complexity, and the need for qualified personnel. Therefore, a lot of research effort is devoted to developing technologies with the potential to revolutionize the detection of pathogenic bacteria by offering rapid, sensitive, and user-friendly platforms for point-of-care analysis. In this light, biosensors have gained significant commercial attention in recent years due to their simplicity, portability, and rapid analysis capabilities. The purpose of this review is to identify a trend by analyzing which biosensor technologies have become commercially successful in the field of bacteria detection. Moreover, we highlight the characteristics that a biosensor must possess to finally arrive in the market and therefore in the hands of the end-user, and we present critical examples of the market applications of various technologies. The aim is to investigate the reason why certain technologies have achieved commercial success and extrapolate these trends to the future economic viability of a new subfield in the world of biosensing: the development of biomimetic sensor platforms. Therefore, an overview of recent advances in the field of biomimetic bacteria detection will be presented, after which the challenges that need to be addressed in the coming years to improve market penetration will be critically evaluated. We will zoom into the current shortcomings of biomimetic sensors based on imprinting technology and aptamers and try to come up with a recommendation for further development based on the trends observed from previous commercial success stories in biosensing., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Accurate and fast on-site detection of harmful microorganisms in food products is a key preventive step to avoid food-borne illness and product recall. In this study, screen-printed electrodes (SPEs) were functionalized via a facile strategy with surface imprinted polymers (SIPs). The SIP-coated SPEs were used in combination with the heat transfer method (HTM) for the real-time detection of Escherichia coli. The sensor was tested in buffer, with a reproducible and sensitive response that attained a limit of detection of 180 CFU/mL. Furthermore, selectivity was assessed by analyzing the sensor's response to C. sakazakii, K. pneumoniae and S. aureus as analogue strains. Finally, the device was successfully used for the detection of E. coli in spiked milk as proof-of-application, requiring no additional sample preparation. These results suggest the proposed thermal biosensor possesses the potential of becoming a tool for routine, on-site monitoring of E. coli in food safety applications., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Pseudomonas aeruginosa is a ubiquitous multi-drug-resistant bacterium, capable of causing serious illnesses and infections. This research focuses on the development of a thermal sensor for the indirect detection of P. aeruginosa infection using molecularly imprinted polymers (MIPs). This was achieved by developing MIPs for the detection of pyocyanin, the main toxin secreted by P. aeruginosa . To this end, phenazine was used as a dummy template, evaluating several polymeric compositions to achieve a selective MIP for pyocyanin recognition. The sensitivity of the synthesized MIPs was investigated by UV-vis analysis, with the best composition having a maximum rebinding capacity of 30 μmol g -1 and an imprinting factor (IF) of 1.59. Subsequently, the MIP particles were immobilized onto planar aluminum chips using an adhesive layer, to perform thermal resistance measurements at clinically relevant concentrations of pyocyanin (1.4-9.8 μM), achieving a limit of detection (LoD) of 0.347 ± 0.027 μM. The selectivity of the sensor was also scrutinized by subjecting the receptor to potential interferents. Furthermore, the rebinding was demonstrated in King's A medium, highlighting the potential of the sensor for the indirect detection of P. aeruginosa in complex fluids. The research culminates in the demonstration of the MIP-based sensor's applicability for clinical diagnosis. To achieve this goal, an experiment was performed in which the sensor was exposed to pyocyanin-spiked saliva samples, achieving a limit of detection of 0.569 ± 0.063 μM and demonstrating that this technology is suitable to detect the presence of the toxin even at the very first stage of its production.

Amine-carbamate self-immolative (SI) spacers represent practical and versatile tools in targeted prodrugs, but their slow degradation mechanism limits drug activation at the site of disease. We engineered a pyrrolidine-carbamate SI spacer with a tertiary amine handle which strongly accelerates the spacer cyclization to give a bicyclic urea and the free hydroxy groups of either cytotoxic (Camptothecin) or immunostimulatory (Resiquimod) drugs. In silico conformational analysis and pK a calculations suggest a plausible mechanism for the superior efficacy of the advanced SI spacer compared to state-of-art analogues., (© 2022 The Authors. ChemMedChem published by Wiley-VCH GmbH.)

We report the synthesis and optoelectronic properties of TIPS-peri-pentacenopentacene (TIPS-PPP), a vertical extension of TIPS-pentacene (TIPS-PEN) and a low-band-gap material with remarkable stability. We found the synthetic conditions to avoid the competition between 1,2- and 1,4-addition of lithium acetylide on the large aromatic dione. The high stability of TIPS-PPP is due to the peri-fusion which increases the aromaticity by generating two localized aromatic sextets that are flanked with 2 diene fragments, similar to two fused-anthracenes. Like TIPS-PEN, TIPS-PPP shows the archetypal 2D brickwall motif in crystals with a larger transfer integral and smaller reorganization energy. The high mobility of up to 1 cm 2  V -1  s -1 was obtained in an organic field-effect transistor fabricated by a wet process. Also, TIPS-PPP was used as a near-infrared (NIR) emitter for NIR organic-light-emitting-diode devices resulting in a high external quantum efficiency at 800 nm., (© 2021 Wiley-VCH GmbH.)

Five new N-phenyl-carbazole benzopyrans bearing different substitutions on one of the phenyl rings at the sp3 carbon have been synthesized. Their molecular structures were investigated by X-ray and NMR analyses and through quantum chemical calculations. The photochromic mechanism under UV irradiation in toluene, consisting of the consecutive formation of transoid-cis (TC) and transoid-trans (TT) isomers, was studied by UV-vis spectral and kinetic analyses. These molecules have been specifically designed to ascertain the possibility of favouring the formation of the less thermodynamically stable TT at the photostationary state, upon exploiting steric hindrance effects on the diene part of the molecule. The spectrokinetic study allowed the estimation of most of the spectrokinetic parameters, such as molar extinction coefficients, quantum yields of UV colouration and visible photobleaching, and the rate constants of the fast and slow thermal bleaching processes. Peculiar effects of substituents with different donor strengths on one phenyl ring located at the 3-position were observed on the spectrokinetic properties.

Biradicaloid compounds with an open-shell ground state have been the subject of intense research in the past decade. Although diindenoacenes are one of the most developed families, only a few examples have been reported as active layers in organic field-effect transistors (OFETs) with a charge mobility of around 10 -3 cm 2 V -1 s -1 due to a steric disadvantage of the mesityl group to kinetically stabilize compounds. Herein, we disclose our efforts to improve the charge transport of the diindenoacene family based on hexahydro-diindenopyrene (HDIP) derivatives with different annelation modes for which the most reactive position has been functionalized with (triisopropylsilyl)ethynyl (TIPS) groups. All the HDIP derivatives show remarkably higher stability than that of TIPS-pentacene, enduring for 2 days to more than 30 days, which depends on the oxidation potential, the contribution of the singlet biradical form in the ground state and the annelation mode. The annelation mode affects not only the band gap and the biradical character ( y 0 ) but also the value of the singlet-triplet energy gap (Δ E S-T ) that does not follow the reverse trend of y 0 . A method based on comparison between experimental and theoretical bond lengths has been disclosed to estimate y 0 and shows that y 0 computed at the projected unrestricted Hartree-Fock (PUHF) level is the most relevant among those reported by all other methods. Thanks to their high stability, thin-film OFETs were successfully fabricated. Well balanced ambipolar transport was obtained in the order of 10 -3 cm 2 V -1 s -1 in the bottom-gate/top-contact configuration, and unipolar transport in the top-gate/bottom-contact configuration was obtained in the order of 10 -1 cm 2 V -1 s -1 which is the highest value obtained for biradical compounds with a diindenoacene skeleton., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Printed organic electronics has attracted considerable interest in recent years as it enables the fabrication of large-scale, low-cost electronic devices, and thus offers significant possibilities in terms of developing new applications in various fields. Easy processing is a prerequisite for the development of low-cost, flexible and printed plastics electronics. Among processing techniques, meniscus guided coating methods are considered simple, efficient, and low-cost methods to fabricate electronic devices in industry. One of the major challenges is the control of thin film morphology, molecular orientations and directional alignment of polymer films during coating processes. Herein, the recent progress of emerging field of meniscus guided printing organic semiconductor materials is discussed. The first part of this report briefly summarizes recent advances in meniscus guided coating techniques. The second part discusses periodic deposits and patterned deposition at moving contact lines, where the mass-transport influences film morphology due to convection at the triple contact line. The last section summarizes our strategy to fabricate large-scale patterning of π-conjugated polymers using meniscus guided method., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Designing stable open-shell organic materials through the modifications of the π-topology of molecular organic semiconductors has recently attracted considerable attention. However, their uses as an active layer in organic field-effect transistors (OFETs) are very limited, and the obtained hole and electron charge mobilities are around 10 -3 cm 2 V -1 s -1 . Herein, we disclose the synthesis of two peri-fused materials, so-called tetracenotetracene (TT) and pentacenopentacene (PP), which have low band gaps of 1.79 and 1.42 eV, respectively. Their ground state natures have been investigated by different experiments including steady state absorption, electron spin resonance, superconducting quantum interfering device, and variable-temperature NMR along with DFT calculations. TT and PP have closed-shell and singlet open-shell structures in their ground state, respectively, and possess high stability. Their biradical characteristics were found to be 0.50 and 0.64. The origin of the open-shell character of PP is related to the concomitant opening of two tetracenes with the recovering of two extra aromatic sextets and a small HOMO-LUMO energy gap (gap <1.5 eV). Thanks to the high stability, thin film OFET devices could be fabricated. In TG-BC configuration PP shows a remarkably high hole mobility of 1.4 cm 2 V -1 s -1 , while TT exhibits a hole mobility of 0.77 cm 2 V -1 s -1 . In the configuration of BG-TC, ambipolar behaviors for both were obtained with hole and electron mobilities of 0.21 and 0.01 cm 2 V -1 s -1 for PP and 0.14 and 0.006 cm 2 V -1 s -1 for TT.

The serendipitous isolation of very small amounts of two naphthocyclobutadiene (NCB) derivatives has led to the computational re-examination of the electrocyclization of Z,Z-3,5-octadiene-1,7-diyne as well as the experimental and computational study of diethynylindeno[2,1-a]fluorene derivatives that contain the 3,5-octadiene-1,7-diyne motif as part of a larger π-framework. In both cases the calculated potential energy surface strongly implicates two successive electrocyclic reactions to afford the antiaromatic products. With the octadienediyne fragment locked in the reactive conformation, the postulated diethynylindeno[2,1-a]fluorene intermediates afford the NCBs in modest to good yields. X-ray crystallography of four NCBs as well as NICS-XY scan calculations show that the paratropic motif is located primarily in the benzocyclobutadiene fragment within the larger π-scaffold., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A set of fully-conjugated indenofluorenes has been synthesized and confirmed by solid-state structure analysis. The indeno[2,1-c]fluorenes and their benzo-fused analogues all contain the antiaromatic as-indacene core. The molecules possess high electron affinities and show a broad absorption that reaches into the near-IR region of the electromagnetic spectrum. All of the featured compounds reversibly accept up to two electrons as revealed by cyclic voltammetry. Analysis of molecule tropicity using NICS-XY scan calculations shows that, while the as-indacene core is less paratropic than s-indacene, benz[a]-annulation further reduces the antiaromaticity of the core. Antiaromatic strength of the as-indacene core can also be tuned by the position of fusion of additional arenes on the outer rings., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two chloromethyl phenylcarbamate-based chiral stationary phases, one containing an amylose-type chiral selector (Lux Amylose 2, from Phenomenex) and the other a cellulose-type one (Lux Cellulose-4, from Phenomenex), were successfully used for the chiral resolution of three helical chromenes featuring a helicene-like structure. The compound bearing a phenyl substituent on the helicene-like structure was enantioresolved at 25°C with Lux Cellulose-4 and a n-hexane/1-propanol 99:1 v/v eluent. With a n-hexane/2-propanol 99.8:0.2 v/v mobile phase, the same column (operated at 35°C) provided the separation of the four isomers of the compound having a hexyl residue on the helicene-like motif and an additional asymmetric carbon. Lux Amylose-2 was necessary for the enantioseparation of the compound having the sole hexyl residue on the helical scaffold. For the last compound a n-hexane/2-propanol 99.8:0.2 v/v eluent was used, and the column temperature was fixed at 5°C. The enantiomer elution order was appraised by using electronic circular dichroism and theoretical calculations. Notably, different thermodynamics of retention and enantioseparation were observed for molecules with pronounced structural similarity, that is, the enantiomer pairs of the compound containing the additional asymmetric carbon atom. Indeed, both entropically and enthalpically controlled adsorption and separation processes were observed., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The extension of the pyrene ring from dimethyl 2,2'-(pyrene-1,6-diyl)dibenzoate derivatives by an intramolecular Friedel-Crafts acylation can be realized in an efficient and regioselective manner using triflic acid as proton source. Naphtho-tetracenone derivatives are obtained in high yields at room temperature while Bis-tetracene-diones are prepared upon heating. Both products display interesting fluorescence properties in the visible range with quantum yields varying from 50 to 60 %., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The benchmark of soluble organic semiconductors based on acenes is the 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-PEN). However TIPS-PEN still suffers from photoinduced oxidation due to its low degree of aromaticity. Increasing the aromaticity while keeping similar optical and electrochemical properties as well as a shape suitable for good hole transport can be achieved with two-dimensional polycyclic aromatic hydrocarbons (2D-PAHs). Herein, we present an efficient synthesis and characterization of bistetracene derivatives that exhibit a band gap up to 1.71 eV and an increased stability up to 21 times compared to TIPS-PEN and mobility over 0.1 cm 2  V -1  s -1 in solution-processed organic field-effect transistors. Based on simple structural consideration, the high stability is attributed to the aromaticity of the bistetracene which is comparable to an anthrancene along each tetracene. According to Clar's sextet rule, the bistetracene should be best regarded as two anthracenes fused at the face bridged by two ethylenic spacers. The synthesis path paves the way towards the preparation of ambipolar and/or longer 2D-PAHs such as bispentacenes and could give rise to organic semiconductors with interesting properties., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two tetraceno[2,1,12,11-opqra]tetracene-extended tetrathia-fulvalenes were prepared and found to undergo reversible conversion into their planar polycyclic aromatic hydrocarbons (PAHs) upon electrochemical oxidation - at potentials probing the best valence bond representations.

The first photoresponsive cholesteric liquid crystal comprising a photoisomerizable helical naphthopyran derivative dopant and a nematic liquid crystal is reported. An unprecedented helical twisting power switching ratio of over 90% allowed us to demonstrate multi-cycle rotational motion of micro-objects by UV light irradiation.

The technological application of sensitized upconversion based on triplet-triplet annihilation (TTA) requires the transition from systems operating in liquid solutions to solid-state materials. Here, we demonstrate that the high upconversion efficiency reported in hyper-cross-linked nanoparticles does not originate from residual mobility of the embedded dyes as it happens in soft hosts. The hyper-reticulation from one side blocks the dyes in fixed positions, but on the other one, it suppresses the nonradiative spontaneous decay of the triplet excitons, reducing intramolecular relaxations. TTA is thus enabled by an unprecedented extension of the triplet lifetime, which grants long excitons diffusion lengths by hopping among the dye framework and gives rise to high upconversion yield without any molecular displacement. This finding paves the way for the design of a new class of upconverting materials, which in principle can operate at excitation intensities even lower than those requested in liquid or in rubber hosts.

Two novel helical naphthopyrans have been synthesised. The helical scaffold has the interesting effect of increasing the thermal stability of the transoid-trans (TT) open isomer formed upon UV irradiation of the closed form (CF), which transforms these naphthopyrans from thermal to photochemical photochromes. The photochromic performance is excellent in both polar and apolar solvents and the conversion percentage from the CF to the TT form can be as high as 92.8 %. We propose a new method to determine the quantum yields of the photochemical processes that lead to transoid-cis (TC) and TT isomers, and their molar absorption coefficients. The thermal stability of the TT and TC isomers has been studied in different solvents. The quantum yields of fluorescence before and after irradiation, along with the decay lifetimes, have also been measured. TD-DFT calculations have been performed to determine the relative thermodynamic stability of the species involved in the photochromic mechanism and to rationalise their spectral properties., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Diindeno[1,2- b :2',1'- n ]perylene, a new derivative of the indenoacene family was synthesized, and its electronic, electrochemical, and electrical properties were investigated. This material has a closed shell electronic configuration which corresponds to a quinoidal structure with a low band gap of 1.35 eV. Molecular packing in the single crystal was studied by single-crystal X-ray structural analysis, and this information was subsequently used in the determination of the charge transfer integrals via density functional theory methods. The charge-carrier transport properties of the diindeno[1,2- b :2',1'- n ]perylene-5,12-dione and diindeno[1,2- b :2',1'- n ]perylene derivatives were investigated through the fabrication and characterization of field-effect transistors via both vacuum-deposited and solution-processed films, respectively. Diindeno[1,2- b :2',1'- n ]perylene exhibited a field-effect behaviour with a hole mobility up to 1.7 × 10 -3 cm 2 V -1 s -1 when the active layer was solution-processed.

The synthesis and characterisation of a three-dimensional lithium-organic framework MIL-145 is described, which upon thermal treatment yields a second open framework, MIL-146, that contains four and three-coordinate lithium centres: the coordinatively unsaturated trigonal planar lithium centres are able to reversibly bind water with crystallinity maintained, while the dehydrated phase shows preferential adsorption of CO(2) over N(2).

The photochromism of [3H]-naphthopyran derivatives can be switched from T-type to inverse- or P-type through the manipulation of relative thermodynamic stabilities of open isomers with intramolecular CH-π bonds.

Bis-spiropryran molecules were grafted onto the surface of upconverting nanoparticles. Fluorescence resonance energy transfer from the upconverting nanoparticles to the surface bis-spiropyran molecules triggered the transformation of the ring-closed bis-spiropyran to the ring-open bis-merocyanine forms.

Azobenzene-coated polymer nanoparticles in the 16-nm-diameter range act as phototriggered nanomotors combining photo to kinetic energy conversion with optical control through light intensity gradients. The grafted dyes act as molecular propellers: their photoisomerization supplies sufficient mechanical work to propel the particles in an aqueous medium toward the intensity minima with velocities of up to 15 μm/s. It is shown that nanoparticles can be driven over tens of micrometers by translating the intensity gradients in the plane. The analysis of the particles motion demonstrates the decisive role of photoisomerization in the transport with a measured driving force that is 3 to 4 orders of magnitude higher than optical forces., (© 2011 American Chemical Society)

The coexistence of 18 isomers, identified by NMR spectroscopy and gathered into six states with very different absorption properties, is observed upon irradiation with selective wavelengths of a triphotochromic system joining two naphthopyran entities through a dithienylethene bridge. The sequential electronic coupling of photochromic groups resulted in an absorption behavior reaching far into NIR.

The synthesis, linear optical and nonlinear optical properties, as well as the electrochemical behavior of a series of pro-ligands containing the 4-(4-N,N-dimethylaminostyryl)-1-methyl pyridinium (DASP(+)) group as a push-pull moiety covalently linked to terpyridine or bipyridine as chelating ligands are reported in this full paper. The corresponding multifunctional Ru(II) and Zn(II) complexes were prepared and investigated. The structural, electronic, and optical properties of the pro-ligands and the ruthenium complexes were investigated using density functional theory (DFT) and time-dependent (TD) DFT calculations. A fairly good agreement was observed between the experimental and the calculated electronic spectra of the pro-ligands and their corresponding ruthenium complexes. A quenching of luminescence was evidenced in all ruthenium complexes compared with the free pro-ligands but even the terpyridine-functionalized metal complexes exhibited detectable luminescence at room temperature. Second order nonlinear optical (NLO) measurements were performed by Harmonic Light Scattering and the contribution of the DASP(+) moieties (and their relative ordering) and the metal-polypyridyl core need to be considered to explain the nonlinear optical properties of the metal complexes.

Core-shell type dual fluorescent nanoparticles (NPs) in the 16 nm diameter range with a selective ligand (cyclam) attached to the surface and two fluorophores--9,10-diphenyl-anthracene (donor, D) and pyrromethene PM 567 (acceptor, A)--embedded within the polymer core were synthesized and their fluorescent and copper-sensing properties were studied and compared to single D-doped and A-doped NPs. The acceptor (A) and donor (D) dyes were chosen to allow two sequential Förster resonance energy transfer (FRET) processes from D to A and from the encapsulated dyes to copper complexes that form at the surface and act as quenchers. NPs with different D/A loads were readily obtained by two consecutive entrapments of the dyes. Dual NPs present tunable fluorescence emission that is dependent on the doping ratio. FRET from D to A results in sensitized emission from A upon excitation of D, with FRET efficiencies reaching 80 % at high acceptor loads. A 9-fold amplification of the signal of A is observed at high D-to-A ratios. Single- and dual-dye-doped NPs were used to detect the presence of cupric ions in water by using the quenching of fluorescence as a transduction signal. In accordance with the spectral overlaps and the values of the critical distance (R0) of D- and A-copper complex pairs, the acceptor is much more sensitive than the donor. In dual fluorescent NPs, the sensitized emission of A is efficiently attenuated whereas the remaining emission of D is much less affected, allowing the detection of copper in a ratiometric manner upon excitation at a single (D) wavelength. Dual-dye-doped NPs with the highest acceptor loads (23 A-per-NP) were found to be the most sensitive for the detection of copper over a wide range of concentrations (20 nM to 8.5 microM). Owing to its great convenience and modularity, the cascade FRET strategy based on dual fluorescent NPs holds great promise for the design of various sensing nanodevices.

The title compound, C(61)H(68)F(8)O(2)S(2), is a photochromic liquid crystal based on diaryl-ethene as photoswitchable unit. The F atoms connected to the benzene rings are disordered over two positions; the site-occupation factors refined to 0.830 (3)/0.170 (3). The mol-ecule adopts a photo-active anti-parallel conformation and the distance between the two reactive C atoms of the thio-phene rings is 3.448 (3) Å. The dihedral angles between the central cyclo-pentene ring and the adjacent thio-phene rings are 43.56 (3) and 48.58 (3)°. These structural elements exhibit a suitable geometry for photochromic behaviour in the crystalline state.

A series of "push-pull" salts substituted with an electron-donating bis(N,N-dimethyl)aniline unit and different electron-withdrawing methyl or chelating pyridinium units have been designed and synthesized from Michler's ketone. The spectroscopic and electronic properties were investigated and compared to their DAST homologues. The studies revealed that a lower HOMO-LUMO gap is obtained in all cases, showing the ability of our donor to increase the "push-pull" effect. Two chromophores with a terpyridine as acceptor end group have also been prepared.

[reaction: see text] The photochromic performance of a hybrid system connecting naphthopyran and dithienylethene was investigated, and the photochemistry of eight different isomers was explored by choosing an appropriate wavelength of light.

The kinetics of the thermal fading of four halogenated naphthopyrans (NP) have been analyzed using NMR spectroscopy in CD(3)CN. Two photomerocyanines (TT and TC) were detected after UV irradiation. The main relaxation process TC --> NP was coupled with TT/TC isomerization. The activation parameters of the various processes were rationalized by considering electronegativity and polarizability of the halogen substituents and their selective solvation by the electronegative nitrogen of acetonitrile.

The effects of the molecular variation of diarylethenes on the mesomorphic, photochromic, and fluorescence properties have been investigated, and dramatic changes in the fluorescence, photochromic, and liquid crystal behavior were observed.

Systematic variation of the molecular symmetry in a photochromic system based on a 1,2-bis(2-methylbenzo[b]thiophen-3-yl)hexafluorocyclopentene group, connected by decyl spacers to two cyanobiphenyl groups as mesogens, allows for a systematic investigation of the correlations between molecular shape and symmetry, electronic effects, photochromic conversion and liquid-crystalline properties.

Photochromic liquid crystals based on [2H]-chromenes functionalised in the 3,3[prime or minute]-positions by phenyl groups linked to 4-cyano-4[prime or minute]-hydroxybiphenyl groups via alkyl and siloxane spacers as chromophore were synthesised and the photochromic and mesomorphic behaviour was investigated., (Copyright 2004 The Royal Society of Chemistry)

A spectrokinetic study of the photophysical and photochemical properties of a series of photochromes bearing thienyl (T(1)), dithienyl (T(2)) and terthienyl (T(3)) groups linked to a naphthopyran in position 3 (sp(3) carbon) or 8 (naphtho moiety) has been carried out. The effect of the number and position of the thienyl groups on the excited state properties of the six compounds in the singlet and triplet manifold has been investigated by stationary and pulsed fluorimetric techniques, laser flash photolysis and kinetic analysis of the colouration/decolouration processes upon continuous irradiation. On increasing the length of the oligothiophene moiety, the contribution of fluorescence to the deactivation processes becomes detectable, while the photocolouration yield decreases. Moreover, only for compounds with T(3) groups was the triplet absorption observed by laser flash photolysis; its decay did not contribute to photocolouration. The competition between physical (fluorescence emission and intersystem crossing) and chemical relaxations markedly affects the behaviour of the compound bearing the T(3) group at the naphtho moiety, which shows the most efficient intersystem crossing and fluorescence emission while does not lead to photoproduction of the coloured open form. A parallel study of the NMR spectra of the compounds bearing one thiophene group allowed two and four photomerocyanine-type photoproducts to be identified for the naphtho-substituted and pyran-substituted compounds, respectively. The compound with a thiophene group at the naphtho moiety was studied in more detail at different temperatures. On the basis of the combined optical and NMR spectrometric results, a reasonable mechanism of its photochromic behaviour is proposed.

A photochromic liquid crystal system based on a diarylethene functionalised in the 2,2'-positions and linked to 4-cyano-4'-hydroxybiphenyl groups via alkyl spacers as chromophores was synthesised and its photochromic and mesomorphic behaviour was investigated.

The influence of oligothiophene substituents on five new [3H]naphtho[2,1-b]pyrans has been investigated using flash photolysis and continuous irradiation techniques. Photochromic properties strongly depend on the number and position of the thienyl units. Thienyl substitution increases the UV/visible absorbance of the lower energy transition of both the naphthopyran and merocyanine isomers. The rate constants of the thermal fading processes also increase with the number of thiophenic entities. Although several minor photoisomers, whose relative amounts depend on the irradiation conditions could be involved, it has been assumed that under continuous monochromatic irradiation, the evolution of the photochromic reaction can be described by the formation of only one photoisomer. Under these conditions, quantum yields of photocolouration and molar absorption coefficients of the non-isolable photomerocyanine isomer were evaluated by photokinetic analysis. Flash-photolytic colourability can be interpreted using continuous irradiation parameters. A linear correlation has been established between experimental and calculated colourability. This result shows that similar photochromic reactions leading to similar photoisomers are triggered either by polychromatic flash photolysis or by continuous monochromatic irradiation.