Synthesis of 1,6/7-(NO2)2-Perylenediimide and 1,6/7-(NH2)2-Perylenediimide as Regioisomerically Pure Materials

The use of perylenediimide (PDI) building blocks in materials for organic electronic is of considerable interest. This popular n-type organic semiconductor is tuned by introducing peripheral groups in their ortho and bay positions. Such modifications radically alter their optoelectronic properties. In this article, we describe an efficient method to afford regioisomerically pure 1,6/7-(NO2)2- and (NH2)2-PDIs employing two key steps: the selective crystallization of 1,6-(NO2)2-perylene-3,4,9,10-tetracarboxy tetrabutylester and the nitration of regiopure 1,7-Br2-PDI with silver nitrite. The optoelectronic properties of the resulting regioisomerically pure dinitro, diamino-PDIs and bisazacoronenediimides (BACDs) are reported and demonstrate the need to separate both regioisomers of such n-type organic semiconductors for their inclusion in advanced optoelectronic devices. For the first time, the two regioisomers of the same PDI starting material are available on the multigram scale, which will stimulate the exploration of regioisomerism/properties relationship for this family of dyes.

Responses of the Necrotrophic Fungus Alternaria brassisicola to the Indolic Phytoalexin Brassinin

Alternaria brassicicola causes black spot disease in Brassicaceae. During host infection, this necrotrophic fungus is exposed to various antimicrobial compounds, such as the phytoalexin brassinin which is produced by many cultivated Brassica species. To investigate the cellular mechanisms by which this compound causes toxicity and the corresponding fungal adaptive strategies, we first analyzed fungal transcriptional responses to short-term exposure to brassinin and then used additional functional approaches. This study supports the hypothesis that indolic phytoalexin primarily targets mitochondrial functions in fungal cells. Indeed, we notably observed that phytoalexin treatment of A. brassicicola disrupted the mitochondrial membrane potential and resulted in a significant and rapid decrease in the oxygen consumption rates. Secondary effects, such as Reactive oxygen species production, changes in lipid and endoplasmic reticulum homeostasis were then found to be induced. Consequently, the fungus has to adapt its metabolism to protect itself against the toxic effects of these molecules, especially via the activation of high osmolarity glycerol and cell wall integrity signaling pathways and by induction of the unfolded protein response.

Third-Order Nonlinear Optical Figure of Merits for Conjugated TTF−Quinone Molecules

We have revealed a substantial enhancement of third-order optical figure of merits by the synthesis of a compact molecule possessing the tetrathiafulvalene (TTF) group with two backside C=O groups. Addition of the saturated methylene chain substantially suppresses the third-order optical figure of merits and even local optical hyperpolarizabilities at lambda = 532 nm. Another TTF-derivative molecule possessing ethylenic and acetylenic chains demonstrates large hyperpolarizabilities; however, generally, the figure of merit factor decreases due to the increasing optical losses as a consequence of enhanced linear absorption. At the same time, both of the chromophores have a large nonlinear optical response. General approaches for search and design of the third-order optical materials with improved properties are given.

S-position isomers of BEDT-TTF and EDT-TTF: synthesis and influence of outer sulfur atoms on the electrochemical properties and crystallographic network of related organic metals

The synthesis and characterization of new modified tetrathiafulvalenes (TTF), the S-position isomers of BEDT-TTF and EDT-TTF, are described. The synthetic strategy presented in this work is based on an efficient and unprecedented two-step sequence for the conversion of a vicinal bis(hydroxymethyl) functionality into a disulfide ring. Different routes are discussed in terms of efficiency for the synthesis of the symmetric S-position isomer of BEDT-TTF and that of EDT-TTF. Their electrochemical properties are combined with data obtained from UV/Vis spectroscopy and orbital calculations, and the electronic influence of peripheral sulfur atoms on the neutral and oxidized species is discussed. The introduction of these outer sulfur atoms at the periphery of the TTF core gives rise to specific intermolecular S...S interactions in the corresponding organic materials. Crystallographic studies of radical cation salts synthesized upon electrocrystallization clearly showed that the network obtained is dictated by the outer sulfur atoms, which are responsible for a characteristic and unprecedented "windmill" array.

Electrolytic electrospray ionization mass spectrometry of C(60)-TTF-C(60) derivatives: high-resolution mass measurement and molecular ion gas-phase reactivity

The electrochemical process involved in electrospray ionization is used to obtain odd-electron molecular ions from C(60)-TTF-C(60) and its methano derivatives. Exact mass measurements obtained using high-resolution mass spectrometry are reported, and the gas-phase behavior of the radical cation (retro-Diels-Alder reaction and [M/2 + H](+) ion formation) is described.