Light scattering from polymer films having optically anisotropic rodlike texture. III. Inter-rod interference

Effects of interparticle interference on depolarized light scattering from polymer films having nonspherulitic (rodlike, disklike, or fibrous) crystalline superstructures are explored, both theoretically and experimentally. Discrepancies between the observed “rodlike scattering” and the predicted scattering based on “single-rod” theory are pointed out and accounted for in terms of various types of aggregation models for polymeric solids and solutions.     

Exchange interaction of 5,5'-(m- and p-phenylene)bis(10-phenyl-5,10-dihydrophenazine) dications and related analogues

[structures: see text] 5,5'-(m-Phenylene)bis[(10-aryl-5,10-dihydrophenazine) dications, 3a2+ and 3b2+, and their p-analogues 4a2+ and 4b2+, were prepared, and their exchange interaction was investigated. The EPR spectra of these dications at 123 K in a butyronitrile matrix showed the population of a triplet state. The temperature dependence of the EPR signal intensity (absolute value(delta m(s)) = 2) showed that these dications had singlet ground states with deltaE(ST)/k(B) = -27 to -21 K for the m-isomer 3(2+) and with deltaE(ST)/k(B) = -10 to -8 K for the p-isomer 4(2+). Theoretical calculation of the exchange interaction J for these dications at the orthogonal torsion angle geometries was carried out for 3a2+ and 4a2+ and for (m- and p-phenylene)bisphenothiazine dications 1(2+) and 2(2+) using the broken-symmetry approach for the singlet states. A good correlation was observed between the calculated J and a MO-energy term in the triplet state, deltaE(TMO) = absolute value(HOMO(alpha) - (HOMO - 1)(alpha)). The calculated J values were negative in the order of 10 K for the m-dications (J/k(B) = -14.7 K for 1(2+), -11.5 K for 3a(2+)), but much smaller negative values were found for the p-isomers (J/k(B) = -0.9 K for 2(2+), -0.8 K for 4a2+). The smaller absolute value(J) values for the p-dications are qualitatively consistent with the experimental deltaE(ST) (2J) values.     

Quintet bis(carbene) from triplet diarylcarbenes introduced at the 1,8-position of anthracene

[9-(10-phenyl)anthryl](4-bromo-2,6-dimethylphenyl)diazomethane was found to be stable enough to survive Sonogashira coupling reaction conditions and was converted to [9-(10-phenyl)anthryl](4-trimethylsilylethynyl-2,6-dimethylphenyl)diazomethane, which was reacted with 1,8-diiodoanthracene to give bis(diazo) compound. Bis(carbene) generated by irradiation of the bis(diazo) compound generated a fairly persistent S = 2 quintet state. [structure: see text]     

Hexaazaphenalenyl anion revisited: a highly symmetric planar pi system with multiple-networking ability for self-assembled metal complexation

The hexaazaphenalenyl anion (HAP, 3-), a highly symmetric heterocyclic pi system, has been synthesized and characterized. The crystal structures of its potassium salt K+.3- and copper complex Cu2+.(NH3)4.(3-)2 show pi-pi stacking and radially extended hydrogen bonds as well as coordination bonds constructed by the HAP anion. These in-plane and out-of-plane strong interactions demonstrate the multiple-networking ability of the HAP anion.     

Biomolecule-Assisted Synthesis of Hierarchical Multilayered Boehmite and Alumina Nanosheets for Enhanced Molybdenum Adsorption

The effective utilization of various biomolecules for creating a series of mesoporous boehmite (γ-AlOOH) and gamma-alumina (γ-Al₂O₃) nanosheets with unique hierarchical multilayered structures is demonstrated. The nature and concentration of the biomolecules strongly influence the degree of the crystallinity, the morphology, and the textural properties of the resulting γ-AlOOH and γ-Al₂O₃ nanosheets, allowing for easy tuning. The hierarchical γ-AlOOH and γ-Al₂O₃ multilayered nanosheets synthesized by using biomolecules exhibit enhanced crystallinity, improved particle separation, and well-defined multilayered structures compared to those obtained without biomolecules. More impressively, these γ-AlOOH and γ-Al₂O₃ nanosheets possess high surface areas up to 425 and 371 m² g⁻¹, respectively, due to their mesoporous nature and hierarchical multilayered structure. When employed for molybdenum adsorption toward medical radioisotope production, the hierarchical γ-Al₂O₃ multilayered nanosheets exhibit Mo adsorption capacities of 33.1–40.8 mg g⁻¹. The Mo adsorption performance of these materials is influenced by the synergistic combination of the crystallinity, the surface area, and the pore volume. It is expected that the proposed biomolecule-assisted strategy may be expanded for the creation of other 3D mesoporous oxides in the future.     

Light scattering from polymer films having optically anisotropic rodlike texture. A quantitative test of theories

The light scattering intensity distribution from rodlike crystalline superstructures is quantitatively investigated theoretically and experimentally. The arithmetic average of theoretical H_v scattered intensities at azimuthal angle μ = 0° and μ = 45° is shown to decrease with increasing scattering angle θ in proportion to W^?1 at high scattering angles for a system composed of a random assembly of rodlike superstructure having very small lateral dimensions relative to the length. The quantity W is defined as 2π(L/λ) sin θ where L is the length of the rod, and λ is the wavelength of light in the medium. A method is proposed to estimate the length L by using the W^?1 dependence. Effects of internal heterogenity, polydispersity in rod length, and finite lateral dimensions of the rodlike superstructure are considered to account for experimental deviation of the scattered intensity distributions from the W^?1 dependence. The effect of finite lateral dimensions turns out to be the most important.     

A Redox-Active Microporous Organosiloxane Containing a Stable Neutral Radical,Trioxotriangulene

A new silyl-substituted trioxotriangulene ( TOT ) neutral radical and corresponding porous organosiloxanes (POSs) were synthesized. The neutral radical exhibited a peculiarly high stability and formed a diamagnetic π-dimer characteristic to TOT neutral radicals stabilized by the strong multiple SOMO-SOMO interaction in both solution and solid states. POSs including TOT units within the organosiloxane-wall were prepared by polycondensation of the silyl groups and formed microporous structures with ∼1 nm-size diameters. Redox ability of TOT units in the POS was demonstrated by the treatment of oxidant/reductant in heterogeneous suspension condition, where the TOT units were reversibly converted between reduced and neutral radical species. Furthermore, the solid-state electrochemical measurements of the POS revealed the reversible multi-stage redox ability of TOT units involving polyanionic species within the organosiloxane-wall.