Dipole-induced, thermally stable lamellar structure by polar aromatic silane.

Controlled self-assembly of polar aromatic silane leads to the formation of well-ordered lamellar structures. Graphite-like features are clearly visible with a scanning electron microscope (SEM). In addition, X-ray diffraction (XRD) patterns suggest a d spacing of 14.28 A along the z-axis and 4.42 A in the xy plane, which all agree with theoretical modeling. Constructing multistacks of silane molecules with a high degree of ordering is a daunting task. Amorphous monolayers are frequently reported. Aggravated van der Waals interaction, pi-pi electron overlapping, and solvophobic interactions can all lead to the formation of multistacks. The importance of a dipole to the ordered stacking is essentially unknown. This work suggests that a strong dipole-dipole interaction can be another important driving force in forming lamellar structures. The resulting large electrostatic interactions between the dipole and water provide an excellent thermal stability for these lamellas up to 350 degrees C. Organized, layered structures with a permanent dipole can be used in piezoelectric devices or as active surfaces to bind polar molecules, such as toxic gas, methanol, or DNA.

Biological versus electronic adaptive coloration: how can one inform the other?

Adaptive reflective surfaces have been a challenge for both electronic paper (e-paper) and biological organisms. Multiple colours, contrast, polarization, reflectance, diffusivity and texture must all be controlled simultaneously without optical losses in order to fully replicate the appearance of natural surfaces and vividly communicate information. This review merges the frontiers of knowledge for both biological adaptive coloration, with a focus on cephalopods, and synthetic reflective e-paper within a consistent framework of scientific metrics. Currently, the highest performance approach for both nature and technology uses colourant transposition. Three outcomes are envisioned from this review: reflective display engineers may gain new insights from millions of years of natural selection and evolution; biologists will benefit from understanding the types of mechanisms, characterization and metrics used in synthetic reflective e-paper; all scientists will gain a clearer picture of the long-term prospects for capabilities such as adaptive concealment and signaling.

Self-assembled nanolayers of conjugated silane with pi-pi interlocking.

The packing of electronic molecules into planar structures and an ensured pi-pi interaction within the plane are preferred for efficient organic transistors. Thin films of organic electronics are exemplar, but the widely adopted molecular design and associated fabrication lead to limited ordering in multistack construction motifs. Here we demonstrate self-assembled nanolayers of organic molecules having potential electronic utility using an amphiphilic silane as a building block. Unlike a cross-linked (tetrahedral) configuration found in conventional siloxane networks, a linear polymer chain is produced following silane polycondensation. As a result, hydrophobic branches plus a noncovalent pi-pi interlocking between the molecules promote planar packing and continuous stacking along the surface normal. In contrast to conventional pi-pi stacking or hydrogen bonding pathways in a fibrous construct, multistacked nanolayers with coexisting pi-pi and herringbone interlocking can provide unmatched properties and processing convenience in molecular electronics.

Blue phosphorescence from mixed cyano-isocyanide cyclometalated iridium(III) complexes.

The synthesis, structure, and photophysical and electrochemical properties of cyclometalated iridium complexes with ancillary cyano and isocyanide ligands are described. In the first synthetic step, cleavage of dichloro-bridged dimers [Ir(N=C)2(mu-Cl)]2 (N=C = 2-phenylpyridine, 2-(2-fluorophenyl)pyridine, and 2-(2,4-difluorophenyl)pyridine) by isocyanide ligands gave monomeric species of the types Ir(N=C)2(RNC)(Cl) (RNC = t-butyl isocyanide, 1,1,3,3-tetramethylbutyl isocyanide, 2-morpholinoethyl isocyanide, and 2,6-dimethylphenyl isocyanide). In turn, the chloride was replaced by cyanide giving Ir(N=C)2(RNC)(CN). The X-ray structures for two of the complexes show that the trans-pyridyl/cis-phenyl geometry of the parent dimer is preserved, with the ancillary ligands positioned trans to the cyclometalated phenyls. The cyano complexes all display strong blue photoluminescence in ambient, deoxygenated solutions with the first lambdamax ranging from 441 to 458 nm, quantum yields spanning 0.60 to 0.75, and luminescent lifetimes of 12.0-21.4 mus. A lack of solvatochromism and highly structured emission indicate that the lowest energy excited state is triplet ligand centered with some admixture of singlet metal-to-ligand charge-transfer character.

Photophysical properties of anthanthrene-based tunable blue emitters.

Anthanthrene (1) derivatives substituted at the 4,10 and 6,12 positions (2-6) were synthesized as promising candidates for organic light emitting diodes (OLEDs). The emission of these compounds can be manipulated in the blue region (lambda(max) = 437-467 nm) through structural modifications. Photophysical and electrochemical properties (phi(F) = 0.20-0.47; tau(F) = 2.97-6.06 ns; HOMO-LUMO energy gap = 2.25-2.56 eV) as well as geometry optimized structures of 1-6 are reported.

Photophysical and electrochemical properties of heteroleptic tris-cyclometalated iridium(III) complexes.

Mixed (difluoro)phenylpyridine/(difluoro)phenylpyrazole tris-cyclometalated iridium complexes were prepared in order to study the effect of fluorination and the pyridine/pyrazole ratio on the emission and electrochemical properties. Increasing fluorination and replacement of pyridine by pyrazole both leads to a widening of the HOMO-LUMO gap and generally leads to a blue shift in emission.