A photoresponsive dithienylethene derivative bearing chiral pinene-based arms underwent a stereoselective photoinduced cyclization reaction to produce greater than 98% of a single diastereomer. The magnitude of the optical rotation changed as much as Delta[alpha]373 = 8698 degrees upon alternate irradiation with 400 nm and greater than 434 nm light.

A more than six orders of magnitude UV-responsive organic field-effect transistor is developed using a benzothiophene (BTBT) semiconductor and strong donor-acceptor Disperse Red 1 as the traps to enhance charge separation. The device can be returned to its low drain current state by applying a short gate bias, and is completely reversible with excellent stability under ambient conditions.

[16] a) Assuming a hexagonal arrangement of the porous structures of the micro-and meso-porous silica matrices, FSM-16, as indicated in the XRD and TEM results, Equation 1 can be derived from a geometrical consideration,where W 0 is the pore volume per unit weight, a is the lattice constant from the XRD result, t is the thickness of the pore wall, and r is the density of the pore wall, which is assumed to be 2.2 g mL ±1.The thickness of the pore wall, t, can be obtained as a constant value of 0.9 nm from the plot of W 0 as a function of a. The pore diameter, d, can be estimated as a±t. b) M. Hruk, M. Jaroniec, A. Sayari, J. Phys. Chem. B, 1997, 101, 583. [17] S. Inagaki, A. Koiwai, N. Suzuki, Y. Fukushima, K. Kuroda, Bull. Chem. Soc. Jpn. 1996, 69, 1449 A Multi-Addressable Photochromic 1,2-Dithienylcyclopentene-Phenoxynaphthacenequinone Hybrid** By Andrew J. Myles, Tony J. Wigglesworth, and Neil R. Branda*The current interest in miniaturizing the components of machinery and electronics down to the molecular level is a major impetus to developing molecular systems that display switchable properties.[1] Photochromic compounds exhibit reversible variations in their physical characteristics when stimulated by light [1,2] and are some of the best contenders for use in electro-optical devices and memory media, where each isomer of the photochromic compound can represent ª0º or ª1º of a digital code. [3] One key aspect in the progress of molecular switching technology is the development of more complex systems that integrate several switchable functions into a single molecule. Memory media capable of processing more than two pieces of information at the same storage site is an illustrative example of an application of the use of multi-addressable switching strategies. Several impressive examples of multi-addressable switching systems have been reported with as many as six addressable states existing within the same molecule.[4] However, their practical application is limited due to the thermal reversibility of the switching units in almost all cases, the inability to access all states in most cases, and the fact that addition of chemical reagents is often required. A thermally stable, multi-addressable, all-photon mode system is more desirable as it will benefit from the fast response times and the ease at which monochromatic light can be tuned and focused when it is used as the switching stimulus. Few of the photochromic compounds known today display the favorable properties of 1,2-dithienylcyclopentene derivatives (DTE). These compounds undergo the thermally irreversible photochemical cyclization reactions (DTE-o > DTE-c) illustrated in Scheme 1, with a high degree of fatigue resistance, making them the most promising candidates for molecular read/write systems.[5] Scheme 1 also presents the photochromic phenoxynaphthacenequinone (PNQ) motif, which interconverts between its trans-(PNQ-t) and ana-forms (PNQ-a), also with a high level of thermal irreversibility and fatigue resistance. [6] We present here an all-pho...

Dithienylethenes (DTEs) are one of the most promising classes of photochromic compounds for use in optoelectronic devices such as waveguides, memory media and sensors. The development of DTE based polymers that contain a high mass-content of the photoactive DTE component, that maintain their photochromic activity in the solid-state and that are easily processed into thin-films under a variety of conditions is critical for the implementation of the materials into useful applications. This Microreview provides an overview of the

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A series of homo-and copolymers containing different photochromic dithienylethene (DTE) architectures was prepared by ring-opening metathesis polymerization (ROMP) techniques. Each DTE structure can be uniquely addressed in the two-and three-component copolymers, providing a means to generate a wide range of colors when the compounds are selectively photocyclized to their ring-closed forms. Multicomponent, multiaddressable materials of this type are beneficial for applications such as multistate photochromic recording, displays, inks, and barcodes.

Photochromic molecules based on 1,2-bis(3-thienyl)cyclopentene derivatives undergo reversible photocyclization reactions between their colorless open-ring, 1o, and colored closed-ring, 1c, forms (see structures below) with an impressive degree of fatigue resistance and thermal irreversibility. [1] The photoreactions can be accompanied by changes in useful physical properties other than absorbance, including refractive index, [2] luminescence, [3] electronic conductance, [4] viscosity, [5] and optical rotation. [6] The photomodulation of these properties has the potential to significantly advance optoelectronic technologies.In order to fully exploit these versatile compounds they must be incorporated into forms that can be easily processed, such as films, which necessitates the development of photoresponsive polymers. [7] Ring-opening metathesis polymerization (ROMP) is an ideal method for preparing functional polymers due to its mild reaction conditions and its compatibility with a wide range of functional groups. [8] We have recently capitalized on this versatility by generating several photoresponsive polymers (2, see structure below) where the photochromic element is attached to the polymer's backbone. [9] Although many of these novel polymers contain an impressive 68 wt.-% of the photoactive dithienylethene, a further increase in the content of the photochromic component will produce ultrahigh-density polymers that will be beneficial in optoelectronic applications.Higher densities can be achieved by decreasing the size of the linker that connects the dithienylethene to the polymer backbone. A better approach takes advantage of the fact that ROMP of strained bicyclic dienes produces cyclopentene rings, analogous to the way bicyclic alkenes generate cyclopentane derivatives. This strategy results in the incorporation of the central ring of the photochromic 1,2-bis(3-thienyl)cyclopentene directly into the polymer backbone. Here we report the first lipophilic and hydrophilic main-chain photochromic homopolymers 5a±c prepared using ROMP. [10] Synthesis of the key dichloride monomer 4a is achieved in a single step by cross-coupling the zinc salt of 3-bromo-5-chloro-2-methylthiophene [11] 3 with 2,3-dibromobicyclo-[2.2.1]hepta-2,5-diene, [12] as shown in Scheme 1. [13] The scheme also illustrates how monomer 4a can be converted to the corresponding diester 4b. Polymers 5a and 5b are then prepared with typical ROMP conditions using commercially COMMUNICATIONS

A series of block copolymers containing a dendronised cationic block for efficient DNA binding and a poly(ethylene glycol) block for encapsulation of the complex were synthesised in a modular fashion using a combination of click chemistry and ring-opening metathesis polymerisation. DNA binding experiments, investigated using gel electrophoresis, dynamic light scattering and transmission electron microscopy, showed that all polymers prepared in this study strongly complex DNA and self-assemble into polyion complex micelles with apparent hydrodynamic radii ranging from 20-120 nm at physiological pH (7.4). The in vitro transfection efficiency and toxicity of these potential non-viral vectors were also evaluated in HeLadouble dagger cells using plasmid DNA encoding for green fluorescent protein as the reporter gene.