Electron- or hole-transporting nature selected by side-chain-directed π-stacking geometry: liquid crystalline fused metalloporphyrin dimers

Novel liquid crystalline (LC) semiconductors were prepared from the copper complex of a fused porphyrin dimer as the electroactive core by attaching to its periphery dodecyl and semifluoroalkyl side chains site-specifically (P≡P(hetero)) and semifluoroalkyl side chains alone (P≡P(homo)). The former and latter formed rectangular columnar and orthorhombic LC mesophases, respectively, where the stacking geometries of the π-conjugated core are quite different from one another. Although the π-electronic properties of the core units in P≡P(hetero) and P≡P(homo) in solution are substantially identical to one another, transient photocurrent profiles of their LC states under time-of-flight conditions clearly showed that P≡P(hetero) behaves as an n-type semiconductor, whereas P≡P(homo), in contrast, behaves as a p-type semiconductor.     

Rational synthesis of supramolecular assemblies based on tetraplatinum units: synthesis, characterization, and selective substitution reactions of four different Pt4 clusters

Four different types of square‐planar Pt₄ clusters, trans‐[Pt₄(μ‐OCOCH₃)₆(μ‐ArNCHNAr)₂] ( 2 : ArNCHNAr=N,N′‐diarylformamidinate), [Pt₄(μ‐OCOCH₃)₇(μ‐ArNCHNAr)] ( 8 ), cis‐[Pt₄(μ‐OCOCH₃)₆(κ⁴‐N₄‐DArBp)] ( 9 : DArBp=1,3‐bis(arylbenzamidinate)propane), and [Pt₄Cl₂(μ‐OCOCH₃)₅(κ⁴‐N₂,P₂‐dpfam)] ( 13 : dpfam=N,N′‐bis[(2‐diphenylphosphino)phenyl]formamidinate), were successfully prepared by using selective substitution reactions of in‐plane acetate ligands of [Pt₄(μ‐OCOCH₃)₈] ( 1 ), which has four in‐plane and four out‐plane acetate ligands, with appropriate capping ligands. Fundamental substitution reactions of the remaining in‐plane acetates with benzoic acid derivatives were also investigated. All newly prepared complexes were characterized from spectral and physical data and combustion analysis. X‐ray crystallographic studies of some of the clusters were also performed. Electrochemical measurements of amidinate‐modified Pt₄ clusters revealed stepwise oxidation processes of the Pt₄ core due to Pt₄⁹⁺/Pt₄⁸⁺ and Pt₄¹⁰⁺/Pt₄⁹⁺. Based on the lability of the in‐plane acetate ligands of the modified Pt₄ clusters, reactions of cis‐[Pt₄(μ‐OCOCH₃)₆(κ⁴‐N₄‐DArBp)] ( 9 c : Ar=C₆H₄tBu‐4) with ferrocenedicarboxylic acid and p‐phenylenedipropionic acid resulted in the selective formation of cyclic dimers 17 and 18 and the reaction of 13 with 4,4′‐biphenyldicarboxylic acid afforded a linear dimer 20 . The dimers were characterized by spectral data, as well as X‐ray analyses for 17 and 18 . The finding of two Fe³⁺/Fe²⁺ redox couples in the electrochemical measurement of dimer 17 indicated that two ferrocenyl units in dimer 17 communicated electronically.     

Fast and accurate radiance calculations using truncation approximation for anisotropic scattering phase functions

The phase function for solar light scattering by large particles such as cloud droplets is strongly anisotropic due to very strong peaking in the forward direction. This creates numerical difficulties when attempting to calculate accurate reflected and transmitted radiances, which are important for remote sensing of atmospheric and surface properties. A popular approach uses the delta function to approximate the forward-scattering peak in a fraction of energy and a limited number of polynomial terms or a geometrically truncated function for the remaining fraction (so-called truncation approximations). This article compares and discusses several methods for fast and accurate calculations using truncation approximations. When using a single truncation approximation for all scattering orders, large biases appear in directions near the solar and anti-solar points. As shown here, high accuracy can be obtained using different truncation approximations depending on the order of scattering. Of particular importance is the use of phase functions close to the exact phase functions for the first few orders of scattering. Applying the method in combination with the Monte Carlo (MC) method, in which the truncation fraction for a scattering order depends on the scattering angle at the previous scattering event, obtains accurate radiance calculations under almost all geometrical and optical conditions, including in directions near the solar point. Because the method also reduces computational noise due to the MC sampling of radiance, it is useful for fast and accurate radiance calculations for cloudy atmospheres.     

Strongly relatively nonexpansive sequences in Banach spaces and applications

We introduce the concept of a strongly relatively nonexpansive sequence in a Banach space and investigate its properties. Then we apply our results to the problem of approximating a common fixed point of a countable family of relatively nonexpansive mappings in a uniformly convex and uniformly smooth Banach space.      

Ion‐Pairing Assemblies Based on Pentacyano‐Substituted Cyclopentadienide as a π‐Electronic Anion

Pentacyanocyclopentadienide (PCCp^?), a stable π‐electronic anion, provided various ion‐pairing assemblies in combination with various cations. PCCp^?‐based assemblies exist as single crystals and mesophases owing to interionic interactions with π‐electronic and aliphatic cations with a variety of geometries, substituents, and electronic structures. Single‐crystal X‐ray analysis revealed that PCCp^? formed cation‐dependent arrangements with contributions from charge‐by‐charge and charge‐segregated assembly modes for ion pairs with π‐electronic and aliphatic cations, respectively. Furthermore, some aliphatic cations gave dimension‐controlled organized structures with PCCp^?, as observed in the mesophases, for which synchrotron XRD analysis suggested the formation of charge‐segregated modes. Noncontact evaluation of conductivity for (C₁₂H₂₅)₃MeN⁺ ? PCCp^? films revealed potential hole‐transporting properties, yielding a local‐scale hole mobility of 0.4 cm² V^?1 s^?1 at semiconductor–insulator interfaces.     

Two‐Dimensional Tetrathiafulvalene Covalent Organic Frameworks: Towards Latticed Conductive Organic Salts

The construction of a new class of covalent TTF lattice by integrating TTF units into two‐dimensional covalent organic frameworks (2D COFs) is reported. We explored a general strategy based on the C₂+C₂ topological diagram and applied to the synthesis of microporous and mesoporous TTF COFs. Structural resolutions revealed that both COFs consist of layered lattices with periodic TTF columns and tetragonal open nanochannels. The TTF columns offer predesigned pathways for high‐rate hole transport, predominate the HOMO and LUMO levels of the COFs, and are redox active to form organic salts that exhibit enhanced electric conductivity by several orders of magnitude. On the other hand, the linkers between the TTF units play a vital role in determining the carrier mobility and conductivity through the perturbation of 2D sheet conformation and interlayer distance. These results open a way towards designing a new type of TTF materials with stable and predesignable lattice structures for functional exploration.     

The effects of the choice of the k-interval number on radiative calculations

The selection of the number of k-interval is a foundation to correlated k-distribution method and the problem of how to do it still remains unsettled. It is pointed out by numerical computation in this work that choosing the number of k-interval is a major factor affecting accuracy and speed in radiative calculation. To increase the number of k-interval is an efficient method to improve the accuracy. However, it is found by this study that there exists a saturation of the accuracy to an increase of the number. The optimal rules on the number of k-interval choosing are proposed in the paper. Then, five versions on atmospheric absorption by gases appropriate for GCMs are given according to them.