2-(2-Methyl­naphtho[2,1-b]furan-1-yl)acetic acid

In the title mol­ecule, C15H12O3, the two six-membered and one five-membered fused-ring system is almost planar and the CH2C(=O)OH residue is essentially orthogonal to it. In the crystal structure, centrosymmetric dimers are formed via the carboxylic acid {⋯O=C—O—H}2 synthon

Methyl 2-(5-bromo-2-methyl­naphtho[2,1-b]furan-1-yl)acetate

The three fused six-, six- and five-membered rings in the title compound, C16H13BrO3, are coplanar, the CH2C(=O)OCH3 residue being twisted out of this plane [dihedral angle = −26.9 (4)°]. Centrosymmetric dimers are found in the crystal structure stabilized by C—H⋯O inter­actions involving the furan O atom

Photo- and Collision-Induced Isomerization of a Charge-Tagged Norbornadiene–Quadricyclane System

Molecular photoswitches based on the norbornadiene-quadricylane (NBD-QC) couple have been proposed as key elements of molecular solar thermal energy storage schemes. To characterize the intrinsic properties of such systems, reversible isomerization of a charge-tagged NBD-QC carboxylate couple is investigated in a tandem ion mobility mass spectrometer, using light to induce intramolecular [2 + 2] cycloaddition of NBD carboxylate to form the QC carboxylate and driving the back reaction with molecular collisions. The NBD carboxylate photoisomerization action spectrum recorded by monitoring the QC carboxylate photoisomer extends from 290 to 360 nm with a maximum at 315 nm, and in the longer wavelength region resembles the NBD carboxylate absorption spectrum recorded in solution. Key structural and photochemical properties of the NBD-QC carboxylate system, including the gas-phase absorption spectrum and the energy storage capacity, are determined through computational studies using density functional theory

Solar Energy Storage by Molecular Norbornadiene–Quadricyclane Photoswitches:Polymer Film Devices

Devices that can capture and convert sunlight into stored chemical energy are attractive candidates for future energy technologies. A general challenge is to combine efficient solar energy capture with high energy densities and energy storage time into a processable composite for device application. Here, norbornadiene (NBD)–quadricyclane (QC) molecular photoswitches are embedded into polymer matrices, with possible applications in energy storing coatings. The NBD–QC photoswitches that are capable of absorbing sunlight with estimated solar energy storage efficiencies of up to 3.8% combined with attractive energy storage densities of up to 0.48 MJ kg −1 . The combination of donor and acceptor units leads to an improved solar spectrum match with an onset of absorption of up to 529 nm and a lifetime (t 1/2 ) of up to 10 months. The NBD–QC systems with properties matched to a daily energy storage cycle are further investigated in the solid state by embedding the molecules into a series of polymer matrices revealing that polystyrene is the preferred choice of matrix. These polymer devices, which can absorb sunlight and over a daily cycle release the energy as heat, are investigated for their cyclability, showing multicycle reusability with limited degradation that might allow them to be applied as window laminates

Norbornadiene photoswitches anchored to well-defined oxide surfaces: From ultrahigh vacuum into the liquid and the electrochemical environment

Employing molecular photoswitches, we can combine solar energy conversion, storage, and release in an extremely simple single molecule system. In order to release the stored energy as electricity, the photoswitch has to interact with a semiconducting electrode surface. In this work, we explore a solar-energy-storing model system, consisting of a molecular photoswitch anchored to an atomically defined oxide surface in a liquid electrolyte and under potential control. Previously, this model system has been proven to be operational under ultrahigh vacuum (UHV) conditions. We used the tailor-made norbornadiene derivative 2-cyano-3-(4-carboxyphenyl)norbornadiene (CNBD) and characterized its photochemical and electrochemical properties in an organic electrolyte. Next, we assembled a monolayer of CNBD on a well-ordered Co3O4(111) surface by physical vapor deposition in UHV. This model interface was then transferred into the liquid electrolyte and investigated by photoelectrochemical infrared reflection absorption spectroscopy experiments. We demonstrate that the anchored monolayer of CNBD can be converted photochemically to its energy-rich counterpart 2-cyano-3-(4-carboxyphenyl)quadricyclane (CQC) under potential control. However, the reconversion potential of anchored CQC overlaps with the oxidation and decomposition potential of CNBD, which limits the electrochemically triggered reconversion

Photoswitching of Dihydroazulene Derivatives in Liquid-Crystalline Host Systems

Photoswitches and dyes in the liquid-crystalline nematic phase have the potential for use in a wide range of applications. A large order parameter is desirable to maximize the change in properties induced by an external stimulus. A set of photochromic and nonphotochromic dyes were investigated for these applications. It was found that a bent-shaped 7-substituted dihydroazulene (DHA) photoswitch exhibited liquid-crystalline properties. Further investigation demonstrated that this material actually followed two distinct reaction pathways on heating, to a deactivated form by a 1,5-sigmatropic shift and to a linear 6-substituted DHA. In addition, elimination of hydrogen cyanide from the photoactive DHA gave both bent and linear azulene dyes. In a nematic host that has no absorbance around 350 nm, it was found that only the linear DHA derivative has nematic properties; however, both 6- and 7-substituted DHAs were found to have large order parameters. In the nematic host, ring opening of either DHA to the corresponding vinylheptafulvene resulted in a decrease in dichroic order parameter and an unusually fast back-reaction to a mixture of both DHAs. Likewise, only the linear azulene derivative showed mesomorphic properties. In the same nematic host, large order parameters were also observed for these dyes

Tracking molecular resonance forms of donor-acceptor push-pull molecules by single-molecule conductance experiments

The ability of molecules to change colour on account of changes in solvent polarity is known as solvatochromism and used spectroscopically to characterize charge-transfer transitions in donor–acceptor molecules. Here we report that donor–acceptor-substituted molecular wires also exhibit distinct properties in single-molecule electronics under the influence of a bias voltage, but in absence of solvent. Two oligo(phenyleneethynylene) wires with donor–acceptor substitution on the central ring (cruciform-like) exhibit remarkably broad conductance peaks measured by the mechanically controlled break-junction technique with gold contacts, in contrast to the sharp peak of simpler molecules. From a theoretical analysis, we explain this by different degrees of charge delocalization and hence cross-conjugation at the central ring. Thus, small variations in the local environment promote the quinoid resonance form (off), the linearly conjugated (on) or any form in between. This shows how the conductance of donor–acceptor cruciforms is tuned by small changes in the environment

One-step Preparation of ZnO Electron Transport Layers Functionalized with Benzoic Acid Derivatives

We present a "one-step" approach to modify ZnO electron transport layers (ETLs) used in organic solar cells. This approach involves adding benzoic acid (BZA) derivatives directly to the ZnO precursor solution, which are then present at the surface of the resulting ZnO film. We demonstrate this approach for three different BZA derivatives, namely benzoic acid, chlorobenzoic acid, and 4-hydrazinobenzoic acid. For all molecules, improved device performance and stability is demonstrated in solar cells using an active layer blend of PTQ10 (donor) and ITIC-Br (non-fullerene acceptor) compared to such cells prepared using untreated ZnO. Furthermore, similar or improved device performance and stability is demonstrated compared to conventional PEIE treatment of ZnO. The presence of the BZA derivatives at the surface after processing is established using X-ray photoelectron spectroscopy and near-edge X-ray absorption fine-structure spectroscopy. From atomic force microscopy analysis and X-ray diffraction studies, the addition of BZA derivatives appears to restrict ZnO grain growth; however, this does not negatively impact device performance. ZnO layers treated with BZA derivatives also exhibit higher water contact angle and lower work function compared to untreated ZnO. This approach enables simplification of device manufacture while still allowing optimization of the surface properties of metal oxide ETLs. Keywords: electron transport layers, zinc oxide, organic solar cells, surface modificationComment: Manuscript: 25 pages, 8 figures, 5 tables. Supplementary Material: 36 pages, 22 figures, 13 tables. Submitted to Solar Energy Materials and Solar Cell

Single-molecule detection of dihydroazulene photo-thermal reaction using break junction technique

基于隧穿机制的电输运是物质世界的基本过程之一。在单分子尺度，分子结构的细微变化足以导致电学性质的显著区别，这也使通过单分子电学检测方法研究化学反应过程成为可能。在这一研究工作中，课题组将通常用于单分子电学测量的裂结技术用于单分子尺度反应动力学的表征。这一工作也为未来的合成化学和化学工程研究提供了一种新思路，即通过纳米技术构造反应微环境，可以实现化学反应速率、产物和产率的优化。 该研究工作是在洪文晶教授和丹麦哥本哈根大学Mogens B. Nielsen教授的共同指导下，通过跨学科的国际合作所完成的。其中洪文晶教授课题组负责该研究工作的实验表征和统计分析，丹麦哥本哈根大学Mogens B. Nielsen教授课题组负责分子体系的合成，Kurt V. Mikkelsen教授和Gemma C. Solomon教授课题组分别负责了该研究工作的反应动力学和电输运理论计算，这也是洪文晶教授课题组与上述研究团队的首次科研合作。我校萨本栋微纳研究院的杨扬助理教授也参与了数据分析和机理讨论的部分工作。 洪文晶教授课题组长期致力于单分子尺度下的化学反应、分子组装、分子器件电输运等方面的相关研究，开发了一系列能够在单分子尺度实现精密控制和精确测量的科学仪器。以此为基础，课题组与国内外材料化学和理论研究团队密切合作，在单分子尺度电输运的量子干涉效应、电化学调控和化学反应表征等领域进行了一系列探索。【Abstract】Charge transport by tunnelling is one of the most ubiquitous elementary processes in nature. Small structural changes in a molecular junction can lead to significant difference in the single-molecule electronic properties, offering a tremendous opportunity to examine a reaction on the single-molecule scale by monitoring the conductance changes. Here, we explore the potential of the single-molecule break junction technique in the detection of photo-thermal reaction processes of a photochromic dihydroazulene/vinylheptafulvene system. Statistical analysis of the break junction experiments provides a quantitative approach for probing the reaction kinetics and reversibility, including the occurrence of isomerization during the reaction. The product ratios observed when switching the system in the junction does not follow those observed in solution studies (both experiment and theory), suggesting that the junction environment was perturbing the process significantly. This study opens the possibility of using nano-structured environments like molecular junctions to tailor product ratios in chemical reactions.This work was generously supported by the University of Copenhagen, the Danish e-Infrastructure Cooperation, the European Union Seventh Framework Programme (FP7/2007-2013) under the ERC grant agreement no.258806, the Danish Council for Independent Research—Natural Sciences, the Carlsberg foundation, NSFC (21673195,21503179), EC FP7 ITNs ‘MOLESCO’ project numbers 606728, and the Young Thousand Talent Project of China. 研究工作得到了国家自然科学基金（21673195，21503179）、固体表面物理化学国家重点实验室、能源材料化学协同创新中心（2011-iChEM）的大力资助与支持