Soluble and easily crystallized anthracene derivatives: precursors of solution-processable semiconducting molecules

New soluble anthracene derivatives containing thiophene and phenylenevinylene derivatives were synthesized via well-known synthetic routes. TIPS derivatives were added at the 9,10-positions of anthracene for the solubility and crystallinity. Both of the molecules were found to be promising for high charge mobility and stable organic semiconductors. The soluble anthracene core (TIPSAnt) is a potential precursor for the synthesis of novel semiconducting materials.     

Direct 23Na NMR observation of mixed cations residing inside a G-quadruplex channel

We report direct (23)Na NMR observation for the presence of mixed cations (Na(+)/K(+), Na(+)/Rb(+), Na(+)/Sr(2+)) inside the G-quadruplex channel formed by the self-association of guanosine 5'-monophosphate at pH 8.     

Uncommon ferromagnetic interactions in a homometallic Co(II) chain bridged by a single end-to-end azide

A new one-dimensional heterochiral coordination polymer [Co(bmdt)(N3)2].MeCN (1.MeCN) with well-isolated chains was prepared via a self-assembly process. Magnetic data show that intrachain ferromagnetic couplings via the single end-to-end azide group are observed, which is an extraordinary case among the azide-bridged Co(II) systems.     

Synthesis and structure-linear and structure-nonlinear optical properties of multi-dipolar zigzag oligoaryleneethynylenes

A novel series of monodisperse, multi-dipolar zigzag oligoaryleneethynylenes DA(n) and D-Ar-A(n), bearing electron-donating dibenzothiophene and electron-accepting dibenzothiophene dioxide as arenes, with up to six charge-transfer (dipolar) units have been designed and synthesized by palladium-catalyzed Sonogashira coupling reactions. The linear and nonlinear optical properties of these multi-dipolar oligoaryleneethynylenes can easily be modified or enhanced by incorporating/extending with various central aryleneethynyl moieties such as phenylethynyl, oligo(9,9-dibutylfluorenyl)ethynyl, and oligothienylethynyl within the donor-acceptor units. Interestingly, the absorption and emission of these zigzag oligoaryleneethynylenes are not dependent on the number of covalently linked dipolar chromophores; however, the fluorescence quantum efficiencies consistently decrease with increased number of covalently linked dipolar units. These zigzag oligoaryleneethynylenes exhibit a linear increase in the two-photon absorption (TPA) cross-sections with increased number of covalently linked dipolar units without red-shifting the absorption and emission spectra. In addition, very large TPA cross-sections in the femtosecond regime (sigma(800) = 1306 GM in DMF or sigma(750) = 1522 GM in CH(2)Cl(2)) were obtained for D-TF-A(4) despite the moderate strength of the donor-acceptor pair. Our results suggest that the TPA properties of these zigzag oligoaryleneethynylenes including TPA wavelength and TPA cross-section can easily be tuned by means of modifying the central aryleneethynylene units and increasing the number of dipolar units, respectively. This approach provides an alternative means to tune or enhance the TPA cross-section at a specific wavelength.     

Synthesis and photovoltaic properties of efficient organic dyes containing the benzo[b]furan moiety for solar cells

New organic dyes composed of the benzo[b]furan donor, thiophene-conjugated bridge, and cyano acrylic acid acceptor have been newly synthesized through the one-pot coupling cyclization key step. Nanocrystalline TiO2 dye-sensitized solar cell was fabricated using this dye. A solar-to-electric conversion efficiency of 6.65% and 4.70% is achieved with 1 and 2, respectively.     

Supramolecular ordering of amide dendrons in lyotropic and thermotropic conditions

Self-assembled superstructures of amide dendrons, from first to third generation including monodendrons and covalently linked dimers, were extensively examined, and the supramolecular ordering processes in thermotropic and lyotropic conditions were compared. The superstructures as determined by X-ray diffraction and DSC revealed that the first and second generation dendrons showed nearly identical superstructures regardless of the assembly conditions. But, the third generation dendrons showed a more sensitive self-organizing behavior. The structure obtained from the gel state was lamellar with a more extended conformation, while the structure from the melt state revealed the columnar superstructures of contracted branches. The superstructure formed from the gel state also showed a structural change upon raising the temperature and assumed a structure similar to the thermotropically driven one, implying that the structure formed from the gel is thermodynamically unstable. The formation of lamellar- or cylinder-type superstructures from amide dendrons was primarily dependent on the shape of dendrons, which is associated with the branch size (generation) and the surrounding conditions.     

Bis­[(2,2‐di­methyl‐1,3‐propane­diamine‐κ2N,N′)(piperidine‐2‐car­boxylato‐κ2N,O)­platinum(II)] sulfate

The title compound, [Pt(C₆H₁₀NO₂)(C₅H₁₄N₂)]₂(SO₄), crystallizes with two cations in the asymmetric unit. The two complex cations, which have a square‐planar Pt^II coordination, are chemically identical but differ slightly in the conformations of their amine groups. A neutral complex, viz. (2,2‐di­methyl‐1,3‐propane­di­amine‐κ²N,N′)bis(2‐piperidine­carb­oxyl­ato‐κN)platinum(II), is shown to form in solution and to change rapidly into the title compound.     

A simulation model for determining variable worker requirements in a service operation with time-dependent customer demand

In a service operation where worker requirements have to be determined for short scheduling time periods with nonstationary customer demand, the assumptions necessary for applying steady-state solutions to elementary queueing models are usually violated. This paper describes a simulation study of the behavior of such a service operation. The results are compared with the steady-state solutions to a queueing model where individual scheduling time periods are assumed to be independent. It is found that if the system utilization is below a derived maximum value (based on a service level criterion), then the steady-state solutions are robust enough to explain the behavior of the system and can be used to schedule worker requirements.     

Dielectric force and relative motion between two spherical particles in electrophoresis

When two particles close to each other are in electrophoretic motion, each particle is under the influence of the nonuniform electric field generated by the other particle. Two particles may attract or repel each other due to the dielectric force, depending on their positions in the nonuniform electric field. In this work, the dielectric interaction and the subsequent relative motion of the two arbitrarily oriented spherical particles are analyzed. The dielectric force is obtained by integrating the Maxwell stress. The result is valid for arbitrary orientations of the particles under the thin electrical-double-layer assumption. The magnitude of the dielectric force is compared to the so-called inertia-induced force, which shows that the dielectric force is normally much greater than the inertia-induced force. The relative velocity of particles is determined by the force balance between the dielectric force and the Stokes drag. The regions of attraction and repulsion are defined. It is shown that a pair of particles eventually aligns parallel to the externally applied electric field, except in the case where the two particles are initially oriented perpendicular to the electric field. A closed-form analytical solution is obtained for the particle trajectory by using the approximate expression for the dielectric force valid for not-too-closely located particles.