3',5'-Di-chloro-N,N-diphenyl-[1,1'-biphen-yl]-4-amine.

The title tri-phenyl-amine derivative, C24H17Cl2N, featuring a 3,5-di-chloro-1,1'-biphenyl moiety has been synthesized and structurally characterized. The mol-ecular structure shows rotations of the phenyl rings in the range of 37-40° from the amine plane. In the crystal, the mol-ecules inter-act by van der Waals inter-actions.

Computational and Crystallographic Examination of Naphthoquinone Based Diarylethene Photochromes.

Photochromic compounds have a lengthy history of study and a profusion of applications that stand to gain from these studies. Among the classes of photochromic compounds, diarylethenes show desirable properties including high fatigue resistance and thermal stability, thus meeting some of the most important criteria necessary to enter the realm of practical applications. Recently, photochromic diarylethenes containing quinone functionalities have demonstrated interesting optical and solid-state properties. When properly interfaced with suitable electron withdrawing groups on the aryl component, both the ring-opening and ring-closing reactions can be achieved with visible light; this is in contrast to most other diarylethenes where UV light is required for ring closure. Unfortunately, quantitative conversion from open to closed forms is not possible. In this work, we examine the relative energies of conformations of solid-state structures observed by X-ray crystallography and evaluate their thermal stabilities based on density functional theory (DFT) calculations. Time-dependent DFT (TD-DFT) is used to model the UV-vis absorption spectra of these quinone diarylethenes. We show that spectral overlap between open and closed forms is a major hindrance to full photoconversion.

A Suzuki Approach to Quinone-Based Diarylethene Photochromes.

Diarylethene photochromes show promise for use in advanced organic electronic and photonic materials with burgeoning considerations for biological applications; however, these compounds typically require UV light for photoswitching in at least one direction, thus limiting their appeal. We here introduce a naphthoquinone-based diarylethene that switches between open and closed forms with visible light. The synthesis of this quinone diarylethene relies on Suzuki methodology, allowing for the inclusion of functional groups not otherwise accessible with current synthetic routes.

The temperature dependent photoswitching of a classic diarylethene monitored by in situ X-ray diffraction.

Organic photochromic molecules including diarylethenes are of particular interest for their numerous potential applications including high-density optical data storage and light-activated switches. In this report, we examined the temperature dependence of the light-drive photocyclization reaction in a classic diarylethene. The steady-state populations were monitored spectroscopically and by temperature dependent in situ photocrystallography, the latter being the first reported example of this technique. The observed decrease in the steady-state population with decreasing temperature suggests this classic diarylethene possesses an excited-state potential energy surface topology similar to previously reported "inverted" diarylethenes.

Photoresponsive porous materials: the design and synthesis of photochromic diarylethene-based linkers and a metal-organic framework.

The synthesis and characterization of novel photochromic diarylethene-based linkers for use in metal­organic frameworks is described including crystal structure analysis of nearly all reaction intermediates. The bis-carboxylated dithien-3-ylphenanthrenes can be prepared under relatively mild conditions in high yield and were subsequently used to create a photoresponsive metal­organic framework, UBMOF-1. While the photochromism of the ligand TPDC in solution is fully reversible, the cycloreversion reaction is suppressed when this linker is incorporated into the crystalline framework of UBMOF-1.

Photo-responsive MOFs: light-induced switching of porous single crystals containing a photochromic diarylethene.

Herein we report the synthesis and characterization of light responsive metal organic framework (MOF) single crystals containing the photochromic diarylethene 1,2-bis(2,5-dimethyl-thien-3-yl)perfluorocyclopentene. Polarized light microscopy on single crystals indicates that the photochrome is preferentially aligned along the c-axis of the host.

Tailor-made additives for morphology control in molecular bulk-heterojunction photovoltaics.

Tailor-made additives, which are molecules that share the same molecular structure as a parent molecule with only slight structural variations, have previously been demonstrated as a useful means to control crystallization dynamics in solution. For example, tailor-made additives can be added to solutions of a crystallizing parent molecule to alter the crystal growth rate, size, and shape. We apply this strategy as a means to predictably control morphology in molecular bulk-heterojunction (BHJ) photovoltaic cells. Through the use of an asymmetric oligomer substituted with a bulky triisobutylsilyl end group, the morphology of BHJ blends can be controlled resulting in a near doubling (from 1.3 to 2.2%) in power conversion efficiency. The use of tailor-made additives provides promising opportunities for controlling crystallization dynamics, and thereby film morphologies, for many organic electronic devices such as photovoltaics and field-effect transistors.

Tautomerism in 10-(hy-droxy-imino)-phenanthren-9-one.

In the title compound, C(14)H(9)NO(2), a static disorder exists between the keto-oxime and hy-droxy-nitroso tautomers, in an approximate ratio of 4.6:1, based on refined occupancies for disordered parts. No inter-molecular hydrogen bonding is present in the crystal structure. Instead, both tautomers exhibit similar intra-molecular O-H⋯O hydrogen bonds.

It takes more than an imine: the role of the central atom on the electron-accepting ability of benzotriazole and benzothiadiazole oligomers.

We report on the comparison of the electronic and photophysical properties of a series of related donor-acceptor-donor oligomers incorporating the previously known 2H-benzo[d][1,2,3]triazole (BTz) moiety as the acceptor and the recently reported BTzTD acceptor, a hybrid of BTz and 2,1,3-benzothiadiazole (BTD). Although often implied in the polymer literature that BTz has good acceptor character, we show that this moiety is best described as a weak acceptor. We present electrochemical, computational, and photophysical evidence supporting our assertion that BTzTD is a strong electron acceptor while maintaining the alkylation ability of the BTz moiety. Our results show that the identity of the central atom (N or S) in the benzo-fused heterocyclic ring plays an important role in both the electron-accepting and the electron-donating ability of acceptor moieties with sulfur imparting a greater electron-accepting ability and nitrogen affording greater electron-donating character. We report on the X-ray crystal structure of a BTzTD trimer, which exhibits greater local aromatic character in the region of the triazole ring and contains an electron-deficient sulfur that imparts strong electron-accepting ability. Additionally, we examine the transient absorption spectra of BTzTD and BTz oligomers and report that the BTz core promotes efficient intersystem crossing to the triplet state, while the presence of the thiadiazole moiety in BTzTD leads to a negligible triplet yield. Additionally, while BTz does not function as a good acceptor, oligomers containing this moiety do function as excellent sensitizers for the generation of singlet oxygen.

A solution- and solid-state investigation of medium effects on charge separation in metastable photomerocyanines.

The effects of solution-state dielectric and intermolecular interactions on the degree of charge separation in metastable spirooxazine photomerocyanines (PMCs) is investigated. We report the first X-ray diffraction (XRD) analyses of an open form, a metastable photomerocyanine, of the spirooxazine class of photochromic molecules in two derivatives: spiro[azahomoadamantane-isoquinolinoxazine] (1) and spiro[azahomoadamantane-phenanthrolinoxazine] (2). Using the results of XRD analysis of the open photomerocyanine forms, in conjunction with computation, solvatochromism, and solution NMR studies, we have investigated the effect of the medium on the ground-state structure of these photomerocyanines. Solvatochromism and NMR chemical shift studies of 1 and 2 support the assignment of a quinoidal structure in nonpolar solvents and a zwitterionic structure in high-polarity solvents. The effect of azahomoadamantyl substitution is explored by comparing 1 and 2 with the analogous indolyl derivatives, spiro[indoline-isoquinolinoxazine] (3) and spiro[indoline-phenanthrolinoxazine] (4) through XRD analysis of the closed spirooxazine (SO) forms, solution-state kinetic experiments, solvatochromism, and NMR studies. Longer C(spiro)-O bond lengths in the SO form and slower rates of thermal PMC --> SO isomerization for the azahomoadamantyl derivatives are associated with greater zwitterionic character in the PMC form, as found in the solvatochromism studies. XRD analysis of photomerocyanines 1 and 2 indicate a greater contribution from the canonical zwitterionic resonance form relative to the quinoidal form in the solid state. Structural differences observed in two pseudopolymorphs of 2-PMC suggest that the degree of charge-separated character is influenced by the crystal packing environment. These results provide direct structural evidence for the effects of the medium polarity on charge-separated states of photomerocyanines.

Rotavirus viremia and extraintestinal viral infection in the neonatal rat model.

Rotaviruses infect mature, differentiated enterocytes of the small intestine and, by an unknown mechanism, escape the gastrointestinal tract and cause viremia. The neonatal rat model of rotavirus infection was used to determine the kinetics of viremia, spread, and pathology of rotavirus in extraintestinal organs. Five-day-old rat pups were inoculated intragastrically with an animal (RRV) or human (HAL1166) rotavirus or phosphate-buffered saline. Blood was collected from a subset of rat pups, and following perfusion to remove residual blood, organs were removed and homogenized to analyze rotavirus-specific antigen by enzyme-linked immunosorbent assay and infectious rotavirus by fluorescent focus assay or fixed in formalin for histology and immunohistochemistry. Viremia was detected following rotavirus infection with RRV and HAL1166. The RRV 50% antigenemia dose was 1.8 x 10(3) PFU, and the 50% diarrhea dose was 7.7 x 10(5) PFU, indicating that infection and viremia occurred in the absence of diarrhea and that detecting rotavirus antigen in the blood was a more sensitive measure of infection than diarrhea. Rotavirus antigens and infectious virus were detected in multiple organs (stomach, intestines, liver, lungs, spleen, kidneys, pancreas, thymus, and bladder). Histopathological changes due to rotavirus infection included acute inflammation of the portal tract and bile duct, microsteatosis, necrosis, and inflammatory cell infiltrates in the parenchymas of the liver and lungs. Colocalization of structural and nonstructural proteins with histopathology in the liver and lungs indicated that the histological changes observed were due to rotavirus infection and replication. Replicating rotavirus was also detected in macrophages in the lungs and blood vessels, indicating a possible mechanism of rotavirus dissemination. Extraintestinal infectious rotavirus, but not diarrhea, was observed in the presence of passively or actively acquired rotavirus-specific antibody. These findings alter the previously accepted concept of rotavirus pathogenesis to include not only gastroenteritis but also viremia, and they indicate that rotavirus could cause a broad array of systemic diseases in a number of different organs.

Photochromism of a spirooxazine in the single crystalline phase.

The single crystals of a closed form spirooxazine spiro[azahomoadamantane-isoquinolinoxazine] were found for the first time to undergo photocoloration processes consistent with photochromism in the single crystalline phase.