Circularly polarised luminescence from planar-chiral Phanephos/Tb(iii)(hfa)3 hybrid luminophores.

Planar-chiral Phanephos, containing the coordinatable P(iii), formed P(iii)/Tb(iii)(hfa)3 hybrid luminophores that successfully emitted characteristic circularly polarised luminescence (CPL) due to 5D4→7F5 transitions in solution. On the other hand, BINAP, containing P(iii)[double bond, length as m-dash]O as axially chiral ligand, exhibited no detectable CPL with Tb(iii)(hfa)3.

Inhibition of Polymorphic Property of Naphthoquinonepigment Derived from Vitamin K.

Organicpigment, 2-Methyl-3-(4-fluorophenylthio)-1,4-naphthalenedione (2), that is a new Vitamin K derivative bearing a fluorine group, did not show any polymorphism disregard of three different solvents. For comparison, its naphthoquinone analogue with a bromine group (1) showed clearly polymorphism susceptible to these solvents.

Solvent-sensitive signs and magnitudes of circularly polarised luminescence and circular dichroism spectra: probing two phenanthrenes as emitters endowed with BINOL derivatives.

A C2-symmeric binaphthyl framework bearing phenanthrene as the emitter exhibited circularly polarised luminescence (CPL) in dilute solutions. The CPL and circular dichroism signs of the luminophores were altered by solvents (chloroform, methanol, acetonitrile, and dimethylformamide). DFT and TD-DFT calculations indicated that the dihedral angle between the phenanthrene and naphthyl rings was responsible for the apparent sign inversion. The role of solvent molecules in the ground and photoexcited states was discussed based on Hansen solubility parameters (δ, δd, δp and δh).

Circularly polarised luminescence of pyrenyl di- and tri-peptides with mixed d- and l-amino acid residues.

Multiple pyrenes as pendants of enantioimpure di-/tripeptides (abbreviated as N-LD-C, N-DL-C, N-LLD-C and N-DDL-C) showed pyrene-origin CPL and CD signals, which were associated with conflicting CPL-/CD-signs, compared to the corresponding enantiopure di-/tri-peptides.

Interactions between C and Cu atoms in single-layer graphene: direct observation and modelling.

Metal doping into the graphene lattice has been studied recently to develop novel nanoelectronic devices and to gain an understanding of the catalytic activities of metals in nanocarbon structures. Here we report the direct observation of interactions between Cu atoms and single-layer graphene by transmission electron microscopy. We document stable configurations of Cu atoms in the graphene sheet and unique transformations of graphene promoted by Cu atoms. First-principles calculations based on density functional theory reveal a reduction of energy barrier that caused rotation of C-C bonds near Cu atoms. We discuss two driving forces, electron irradiation and in situ heating, and conclude that the observed transformations were mainly promoted by electron irradiation. Our results suggest that individual Cu atoms can promote reconstruction of single-layer graphene.

Circularly polarised luminescence and circular dichroism of l- and d-oligopeptides with multiple pyrenes.

Among l- and d-oligopeptides with multiple pyrenes as pendants, the dipeptides with two and three pyrenes showed blue-coloured circularly polarised luminescence as high as |gem|≈ (0.86-1.1) × 10(-2) at around 450 nm, reflecting from exciton couplets of twisted pyrenes.

Multiple optical properties of a naphthoquinone pigment: 2-methyl-3-(hydroxyphenylthio)-1,4-naphthalenedione.

Naphthoquinone pigments 2-methyl-3-(4- or 2-hydroxyphenylthio)-1,4-naphthalenedione show characteristic optical properties in solution and in the solid state. The position of the OH group in the pigment leads to varied optical properties, including a characteristic colour, in the solid state. The pigment with a 2-OH substituent displays solvatochromism in solution, and that with a 4-OH substituent displays optical chirality in the solid state.

Nonclassical dual control of circularly polarized luminescence modes of binaphthyl-pyrene organic fluorophores in fluidic and glassy media.

The fluorescent modes and signs of the circularly polarized luminescence of an axially chiral binaphthyl-pyrene organic fluorophore were successfully controlled by changing from a fluidic chloroform solution to a glassy poly(methyl methacrylate) solid film.

A new method for separating configurational and constitutional chiralities using diffuse reflectance circular dichroism (DRCD).

Solid-state chiral chemistry has attracted significant scientific interest because of its application in the chiral-selective production, chiral recognition, resolution, and detection of enantiomers of a chiral compound. Combining a novel diffuse reflectance circular dichroism (DRCD) technique with powder X-ray crystallographic analysis, we investigated the origin of chiral properties from the molecular and supramolecular chiralities and the possibility of separating independent CD signals from the superimposed CD signal resulting from different chiral origins.

Material design of plasma-enhanced chemical vapour deposition SiCH films for low-k cap layers in the further scaling of ultra-large-scale integrated devices-Cu interconnects.

Cap layers for Cu interconnects in ultra-large-scale integrated devices (ULSIs), with a low dielectric constant (k-value) and strong barrier properties against Cu and moisture diffusion, are required for the future further scaling of ULSIs. There is a trade-off, however, between reducing the k-value and maintaining strong barrier properties. Using quantum mechanical simulations and other theoretical computations, we have designed ideal dielectrics: SiCH films with Si-C2H4-Si networks. Such films were estimated to have low porosity and low k; thus they are the key to realizing a cap layer with a low k and strong barrier properties against diffusion. For fabricating these ideal SiCH films, we designed four novel precursors: isobutyl trimethylsilane, diisobutyl dimethylsilane, 1, 1-divinylsilacyclopentane and 5-silaspiro [4,4] noname, based on quantum chemical calculations, because such fabrication is difficult by controlling only the process conditions in plasma-enhanced chemical vapor deposition (PECVD) using conventional precursors. We demonstrated that SiCH films prepared using these newly designed precursors had large amounts of Si-C2H4-Si networks and strong barrier properties. The pore structure of these films was then analyzed by positron annihilation spectroscopy, revealing that these SiCH films actually had low porosity, as we designed. These results validate our material and precursor design concepts for developing a PECVD process capable of fabricating a low-k cap layer.

Control of circularly polarized luminescence by using open- and closed-type binaphthyl derivatives with the same axial chirality.

The solution-dispersed-state and polymer-dispersed-state circular dichroism (CD) and circularly polarized luminescence (CPL) properties of chiral binaphthyl fluorophores could be controlled by the choice of open- or closed-type substituents on the binaphthyl units and by the axial chirality of the binaphthyls.

Nonclassical tunability of solid-state CD and CPL properties of a chiral 2-naphthalenecarboxylic acid/amine supramolecular organic fluorophore.

The solid-state chiral optical properties (circular dichroism and circularly polarized luminescence) of a 2-naphthalenecarboxylic acid/amine supramolecular organic fluorophore can be controlled by changing the aryl unit of the chiral 1-arylethylamine component of the molecule rather than altering the chirality of the 1-arylethylamine itself.

Control of the solid-state chiral optical properties of a supramolecular organic fluorophore containing 4-(2-arylethynyl)-benzoic acid.

The solid-state chiral optical properties of a 4-(2-arylethynyl)-benzoic acid/amine supramolecular organic fluorophore can be controlled by changing the arylethynyl group of the achiral 4-(2-arylethynyl)-benzoic acid component molecule rather than the chirality of the amine component molecule.

Supramolecular chirality measured by diffuse reflectance circular dichroism spectroscopy.

Supramolecular chirality of crystals which display chirality only in the solid state was for the first time measured by diffuse reflectance circular dichroism (DRCD) spectroscopy for sublimable 1 : 1 pyrene (PYR)-p-benzoquinone (Q) complex, and its integrity was proved.

A coincident spontaneous resolution system for racemic 1,1'-binaphthyl-2,2'-dicarboxylic acid and 1,2-diphenylethylenediamine induced by water.

Spontaneously resolvable conglomerate crystals are obtained by combining racemic (rac)-1,1'-binaphthyl-2,2'-dicarboxylic acid and rac-1,2-diphenylethylenediamine, and this spontaneous resolution system is induced by water which is present in the crystallization solvent.

A solid-state fluorescent host system with a 2(1)-helical column consisting of chiral (1R,2S)-2-amino-1,2-diphenylethanol and fluorescent 1-pyrenecarboxylic acid.

A solid-state fluorescent host system was created by self-assembly of a 2(1)-helical columnar organic fluorophore composed of (1R,2S)-2-amino-1,2-diphenylethanol and fluorescent 1-pyrenecarboxylic acid. This host system has a characteristic 2(1)-helical columnar hydrogen- and ionic-bonded network. Channel-like cavities are formed by self-assembly of this column, and various guest molecules can be included by tuning the packing of this column. Moreover, the solid-state fluorescence of this host system can change according to the included guest molecules. This occurs because of the change in the relative arrangement of the pyrene rings as they adjust to the tuning of the packing of the shared 2(1)-helical column, according to the size of the included guest molecules. Therefore, this host system can recognize slight differences in molecular size and shape.

A charge-transfer complex of 10,10'-dihydroxy-9,9'-biphenanthryl and methylviologen as a visual inclusion host system.

A charge-transfer (CT) complex, composed of 10,10'-dihydroxy-9,9'-biphenanthryl as the electron donor and 1,1'-dimethyl-4,4'-bipyridinium dichloride as the electron acceptor, is formed only by the inclusion of guest molecules. The color of this inclusion CT complex is sensitive to the component guest molecules.

Visualization of molecular recognition: a novel system based on charge-transfer complexes composed of 1,1'-bi-2-naphthol derivatives and p-benzoquinone.

[reaction: see text] Charge-transfer (CT) complexes composed of 1,1'-bi-2-naphthol derivatives as an electron donor and p-benzoquinone as an acceptor serve as an excellent host system for visual molecular recognition. This is because they form inclusion crystals with guest aromatic compounds which display remarkably different colors depending on the structure of the component molecules and on the method of crystallization (i.e., solution crystallization or solid cogrinding of component crystals).

CD spectra of d-f heterobimetallic helicates with segmental di-imine ligands.

We have investigated the CD spectra of a series of enantiomerically pure heterobimetallic helicates, Lambda,Lambda-[LnCr(1)(3)](6+) (Ln = Eu, Gd, Tb), which contain segmental di-imine ligands. For the mononuclear precursor of these helicates, Lambda-[Cr(1)(3)](3+), a positive exciton couplet was observed around 330 nm, as expected for a tris(di-imine) complex with this absolute configuration. The titration of Ln(III) ions into a solution of this complex leads to the formation of Lambda,Lambda-[LnCr(1)(3)](6+). During this process, the CD signal was observed to invert to give a signal which was negative at lower energies. We investigated the observed changes in the CD spectra using a ZINDO-based computational method which we have previously developed. We were able to show that the exciton coupling of the chromophores coordinated to the Cr and Ln ions give rise to CD signals of opposite phase, despite having the same nominal absolute configuration. Exciton coupling between chromophores located on different metal centers ("internuclear" exciton coupling) is also predicted to have a significant impact on the observed spectrum. We were able to "deconstruct" the observed CD spectra into a set of competing exciton coupling effects and show that the sign of these spectra does not correlate with the absolute configuration of the individual metal centers.

CD spectra of polynuclear complexes of diimine ligands: theoretical and experimental evidence for the importance of internuclear exciton coupling.

We have recently reported on dinuclear complexes Lambda,Lambda-[Co(2)L(2)Cl(2)]CoCl(4) of two novel chiral ligands (1a and 1b) which contain pyridyl-imine chelate groups (Telfer, S. G.; Sato, T.; Kuroda, R. Chem. Commun. 2003, 1064-1065). The absolute configuration of the cobalt(II) centers was unambiguously assigned by X-ray crystallography. However, the sign of the exciton couplets in their CD spectra was opposite to that expected on the basis of the stereochemistry of the metal centers. We present a rationalization of these anomalous spectra in terms of an "internuclear" exciton coupling model which takes into account the coupling of chromophores located on different metal centers. We have performed a series of semiempirical (ZINDO) calculations which provide quantitative support to this model. These findings show that the absolute configuration of the metal centers in a polynuclear complex may be incorrectly assigned on the basis of CD data if internuclear coupling effects are not taken into consideration. We summarize the CD spectral data of number of other chiral polynuclear complexes from the literature, including dinuclear complexes bridged by the 2,2'-bipyrimidine ligand, complexes of the HAT ligand, and dinuclear triple-stranded helicates. The amplitude of the CD spectra of many of these complexes is not additive with the number of chromophores. These anomalous spectra can be accounted for by taking internuclear coupling effects into consideration.