Control of Axial Chirality by Planar Chirality Based on Optically Active [2.2]Paracyclophane

Optically active X-shaped molecules based on the planar chiral [2.2]paracyclophane building block were prepared, in which di(methoxy)terphenyl units were stacked on the central benzene rings. At 25 °C, anisolyl rings freely rotate in solution, while in the crystal form, they are fixed by intramolecular CH–π interactions, thereby leading to the expression of the axial chirality, i.e., propeller chirality was exhibited by the planar chiral [2.2]paracyclophane moiety. The X-shaped molecule exhibited good circularly polarized luminescence (CPL) profiles with moderate Φ_PL and a large g_lum value in the order of 10⁻³ at 25 °C, in solution. In contrast, at −120 °C, dual CPL emission with opposite signs was observed. According to the theoretical studies, the rotary motion of the anisolyl units is suppressed in the excited states, and so emission from two isomers could be observed. These results demonstrate that the axial chirality was controlled by the planar chirality, leading ultimately to propeller chirality.     

Enhanced antifungal activities of four Zn(II) complexes based on uniconazole

Four Zn(II) complexes, [Zn L ₂(SO₄)]_n ( 1 ), [Zn L ₄(H₂O)₂]?2(NO₃)?4EtOH ( 2 ), [Zn L ₂Cl₂]? L ( 3 ), and [Zn L ₂Br₂]? L ( 4 ) ( L  = uniconazole), were synthesized using a hydrothermal method and characterized by elemental analysis, FT‐IR spectroscopy, and single‐crystal XRD. Complex 1 formed a one‐dimensional polymer chain. However, complexes 2 ‐ 4 were obtained as zero‐dimensional mononuclear coordination compounds. The antifungal activities of these complexes were then evaluated against four selected fungi using the mycelial growth rate method. The resulting data indicate that all complexes show better antifungal activities than their ligands and mixtures. In addition, the interactions between the metal salts of complexes 1 ‐ 4 and uniconazole seem to be synergistic. Furthermore, the polymer chain structure of complex 1 significantly enhanced the bioactivity, especially against Botryosphaeria ribis ( I ). Density functional theory (DFT) calculations were carried out to help explain the enhanced bioactivity after the formation of Zn(II) complexes. The resulting data show that the HOMO–LUMO energy gaps of complexes 1 ‐ 4 (0.0578, 0.0946, 0.1053, and 0.1245 eV) are smaller than that of the free ligand (0.1247 eV) and correlate with the antifungal activity of the zinc complexes.     

Air‐Stable Spirofluorene‐Containing Ladder‐Type Bis(alkynyl)borane Compounds with Readily Tunable Full Color Emission Properties

A series of air‐stable spiro‐fused ladder‐type boron(III) compounds has been designed, synthesized, and the electrochemistry and photophysical behavior have been characterized. By simply varying the substituents on the pyridine ring and extending the π‐conjugation of the spiro framework, the emission color of these compounds can be easily fine‐tuned spanning the visible spectrum from blue to red. All compounds exhibit a broad and structureless emission band across the entire visible region, assigned as an intramolecular charge‐transfer transition originating from the thiophene of the spiro framework to the pyridine‐borane moieties. In addition, these compounds demonstrate high photoluminescence quantum yields of up to 0.81 in dichloromethane solution and 0.86 in doped thin films. Some of the compounds have also been employed as emissive materials, in which solution‐processed organic light‐emitting devices (OLEDs) with tunable emission colors spanning the visible spectrum from blue, green to red have been realized, demonstrating the potential applications of these boron compounds in OLEDs.     

A computational method for geometric optimization of enhanced heat transfer devices based upon entropy generation minimization

A computational fluid dynamics‐based optimization methodology is developed, appropriate for the geometric optimization of enhanced heat transfer devices based upon the principle of entropy generation minimization, in which the objective function is evaluated from a flow field obtained by computational simulation. A quasi‐Newton optimization procedure is employed, with computation of the objective function gradients based upon a finite difference approach. The optimization procedure is developed to be general with regard to the choice of objective function, the details of the problem under consideration, and the computational methodology employed in solving the fluid flow and heat transfer problems. A novel implementation of a Taylor series‐based procedure for the fast solution of nearby problems is presented, which is found to greatly benefit the efficiency of the present methodology. Finally, a numerical experiment is presented, illustrating the use of the present method in the geometric optimization of a practical enhanced heat transfer device on the basis of the criterion of entropy generation minimization. The optimization of the fin spacing of a simple plate fin heat sink is considered, and a comparison of the computational results with results obtained by analytical optimization based upon empirical friction factor and Nusselt number correlations is given. Copyright © 2012 John Wiley & Sons, Ltd.     

可见近红外光响应直接Z型异质结光催化剂LaNiO3/CdS的产氢性能

通过冷凝-回流方式制备可见近红外光响应直接 Z型 LaNiO₃/CdS纳米杂化物，在对其进行物理化学表征后将其应用于光解水产氢反应。在可见光照射下，LaNiO₃/CdS光催化剂在5 h的H₂产量达到737 μmol，其H₂产量是CdS的4.3倍(172 μmol)。光电化学测试证实，LaNiO₃/CdS之间异质结的构筑能有效地促进光生载流子在界面的迁移、分离，从而促进其光解水产氢效率和稳定性的提高。同时随着近红外光的引入，其产氢活性提高至996 μmol。在上转换荧光测试中，LaNiO₃在808 nm光激发下在406和628 nm显示出发射荧光，这表明其能在近红外光照射下产生光生载流子，从而进一步提高其光解水产氢效率。     

Engineered Bifunctional Luminescent Pillared-Layer Frameworks for Adsorption of CO2 and Sensitive Detection of Nitrobenzene in Aqueous Media

Through a dual-ligand synthetic approach, five isoreticular primitive cubic (pcu)-type pillared-layer metal–organic frameworks (MOFs), [Zn₂(dicarboxylate)₂(NI-bpy-44)] ⋅ x DMF ⋅ y H₂O, in which dicarboxylate=1,4-bdc ( 1 ), Br-1,4-bdc ( 2 ), NH₂-1,4-bdc ( 3 ), 2,6-ndc ( 4 ), and bpdc ( 5 ), have been engineered. MOFs 1 – 5 feature twofold degrees of interpenetration and have open pores of 27.0, 33.6, 36.8, 52.5, and 62.1 %, respectively. Nitrogen adsorption isotherms of activated MOFs 1′ – 5′ at 77 K all displayed type I adsorption behavior, suggesting their microporous nature. Although 1′ and 3′ – 5′ exhibited type I adsorption isotherms of CO₂ at 195 K, MOF 2′ showed a two-step gate-opening sorption isotherm of CO₂. Furthermore, MOF 3′ also had a significant influence of amine functions on CO₂ uptake at high temperature due to the CO₂–framework interactions. MOFs 1 – 5 revealed solvent-dependent fluorescence properties; their strong blue-light emissions in aqueous suspensions were efficiently quenched by trace amounts of nitrobenzene (NB), with limits of detection of 4.54, 5.73, 1.88, 2.30, and 2.26 μm , respectively, and Stern–Volmer quenching constants (K_sv) of 2.93×10³, 1.79×10³, 3.78×10³, 4.04×10³, and 3.21×10³ m ⁻¹, respectively. Of particular note, the NB-included framework, NB@ 3 , provided direct evidence of the binding sites, which showed strong host–guest π–π and hydrogen-bonding interactions beneficial for donor–acceptor electron transfer and resulting in fluorescence quenching.     

TiO2 photocatalysis for the degradation of pollutants in gas phase: From morphological design to plasmonic enhancement

TiO₂-based photocatalysis has become a viable technology in various application fields such as (waste)water purification, photovoltaics/artificial photosynthesis, environmentally friendly organic synthesis and remediation of air pollution. Because of the increasing impact of bad air quality worldwide, this review focuses on the use and optimization of TiO₂-based photocatalysts for gas phase applications. Over the past years various specific aspects of TiO₂ photocatalysis have been reviewed individually. The intent of this review is to offer a broad tutorial on (recent) trends in TiO₂ photocatalyst modification for the intensification of photocatalytic air treatment. After briefly introducing the fundamentals of photocatalysis, TiO₂ photocatalyst modification is discussed both on a morphological and an electronic level from the perspective of gas phase applications. The main focus is laid on recent developments, but also possible opportunities to the field. This review is intended as a solid introduction for researchers new to the field, as well as a summarizing update for established investigators.     

Encapsulation and Enhanced Luminescence Properties of IrIII Complexes within a Hexameric Self‐Assembled Capsule

Encapsulation and luminescence studies of [Ir(ppy)₂(bpy)]Cl (ppy=2‐phenylpyridinate, bpy=2,2′‐bipyridine) within a hexameric resorcinarene capsule are reported. One Ir^III complex cation was encapsulated within the capsule, as demonstrated by NMR and dynamic light scattering (DLS) studies. The emission color of the Ir^III complex was drastically changed from orange to yellow by encapsulation, in contrast with the lack of significant changes in the absorption spectrum. The hexameric capsule effectively hampers the non‐radiative pathway to increase both the luminescence quantum yield and the exited state lifetime. The luminescent properties of the encapsulated Ir^III complex depend on the ratio of Ir^III complex to the resorcinarene monomer as well as the concentration of resorcinarene monomer owing to the reversible process of self‐assembly of the hexameric capsule. Quenching experiments revealed that the Ir^III complex in the capsule was effectively separated from quenchers.     

An Atomically Precise Au10Ag2 Nanocluster with Red–Near‐IR Dual Emission

A red–near‐IR dual‐emissive nanocluster with the composition [Au₁₀Ag₂(2‐py?C≡C)₃(dppy)₆](BF₄)₅ ( 1 ; 2‐py?C≡C is 2‐pyridylethynyl, dppy=2‐pyridyldiphenylphosphine) has been synthesized. Single‐crystal X‐ray structural analysis reveals that 1 has a trigonal bipyramidal Au₁₀Ag₂ core that contains a planar Au₄(2‐py?C≡C)₃ unit sandwiched by two Au₃Ag(dppy)₃ motifs. Cluster 1 shows intense red–NIR dual emission in solution. The visible emission originates from metal‐to‐ligand charge transfer (MLCT) from silver atoms to phosphine ligands in the Au₃Ag(dppy)₃ motifs, and the intense NIR emission is associated with the participation of 2‐pyridylethynyl in the frontier orbitals of the cluster, which is confirmed by a time‐dependent density functional theory (TD‐DFT) calculation.