Directing transition metal-based oxygen-functionalization catalysis

This review presents the recent progress of oxygen functionalization reactions based on non-electrochemical (conventional organic synthesis) and electrochemical methods. Although both methods have their advantages and limitations, the former approach has been used to synthesize a broader range of organic substances as the latter is limited by several factors, such as poor selectivity and high energy cost. However, because electrochemical methods can replace harmful terminal oxidizers with external voltage, organic electrosynthesis has emerged as greener and more eco-friendly compared to conventional organic synthesis. The progress of electrochemical methods toward oxygen functionalization is presented by an in-depth discussion of different types of electrically driven-chemical organic synthesis, with particular attention to recently developed electrochemical systems and catalyst designs. We hope to direct the attention of readers to the latest breakthroughs of traditional oxygen functionalization reactions and to the potential of electrochemistry for the transformation of organic substrates to useful end products.

This review presents the recent progress of oxygen functionalization catalysis via non-electrochemical (conventional organic synthesis) and electrochemical routes.     

Directing droplets using microstructured surfaces

Systematic variation of microscale structures has been employed to create a rough superhydrophobic surface with a contact angle gradient. Droplets are propelled down these gradients, overcoming contact angle hysteresis using energy supplied by mechanical vibration. The rough hydrophobic surfaces have been designed to maintain air traps beneath the droplet by stabilizing its Fakir state. Dimensions and spacing of the microfabricated pillars in silicon control the solid-liquid contact area and are varied to create a gradient in the apparent contact angle. This work introduces the solid-liquid contact area fraction as a new control variable in any scheme of manipulating droplets, presenting theory, fabricated structures, and experimental results that validate the approach.     

Directing Traffic: Halogen-Bond-Mediated Membrane Transport

The plasma membrane regulates the transport of molecules into the cell. Small hydrophobic molecules can diffuse directly across the lipid bilayer. However, larger molecules require specific transporters for their entry into the cell. Regulating the cellular entry of small molecules and proteins is a challenging task. The introduction of halogen, particularly iodine, to small molecules and proteins is emerging to be a promising strategy to improve the cellular uptake. Recent studies reveal that a simple substitution of hydrogen atom with iodine not only increases the cellular uptake, but also regulates the membrane transport. The strong halogen-bond-forming ability of iodine atoms plays a crucial role in the transport and the introduction of iodine may provide an efficient strategy for studying membrane activity and cellular functions and improving the delivery of therapeutic agents. This Concept article does not provide a comprehensive picture of membrane transport but highlights halogen-substitution as a novel strategy for understanding and regulating the cell-membrane traffic.     

Directing the polar organization of microtubules

Microtubules (MTs) are polar protein filaments that participate in critical biological functions ranging from motor protein direction to coordination of chromosome separation during cell division. The effective facilitation of these processes, however, requires careful regulation of the polar orientation and spatial organization of the assembled MTs. We describe here an artificial approach to polar MT assembly that enables us to create three-dimensional polar-oriented synthetic microtubule organizing centers (POSMOCs). Utilizing engineered MT polymerization in concert with functionalized micro- and nanoscale particles, we demonstrate the controllable polar assembly of MTs into asters and the variations in aster structure determined by the interactions between the MTs and the functionalized organizing particles. Inspired by the aster-like form of biological structures such as centrosomes, these POSMOCs represent a key step toward replicating biology's complex materials assembly machinery.     

Directing Foldamer Self-Assembly with a Cyclopropanoyl Cap

The rational design of self-assembling organic materials is extremely challenging due to the difficulty in precisely predicting solid-state architectures from first principles, especially if synthons are conformationally flexible. A tractable model system to study self-assembly was constructed by appending cyclopropanoyl caps to the N termini of helical α/β-peptide foldamers, designed to form both N−H⋅⋅⋅O and C^α−H⋅⋅⋅O hydrogen bonds, which then rapidly self-assembled to form foldectures (foldamer architectures). Through a combined analytical and computational investigation, cyclopropanoyl capping was observed to markedly enhance self-assembly in recalcitrant substrates and direct the formation of a single intermolecular N−H⋅⋅⋅O/C^α−H⋅⋅⋅O bonding motif in single crystals, regardless of peptide sequence or foldamer conformation. In contrast to previous studies, foldamer constituents of single crystals and foldectures assumed different secondary structures and different molecular packing modes, despite a conserved N−H⋅⋅⋅O/C^α−H⋅⋅⋅O bonding motif. DFT calculations validated the experimental results by showing that the N−H⋅⋅⋅O/C^α−H⋅⋅⋅O interaction created by the cap was sufficiently attractive to influence self-assembly. This versatile strategy to harness secondary noncovalent interactions in the rational design of self-assembling organic materials will allow for the exploration of new substrates and speed up the development of novel applications within this increasingly important class of materials.     

Catalytic Alkyne Arylation Using Traceless Directing Groups

By using Pd⁰/Mandyphos, we achieved a three‐component aminoarylation of alkynes to generate enamines, which are then hydrolyzed to either α‐arylphenones or α,α‐diarylketones. This Pd‐catalyzed method overcomes established known pathways to enable the use of amines as traceless directing groups for C?C bond formation.     

Directing Polymorphism in the Helical Nanofilament Phase

Herein, it is reported that the polymorphism in the helical nanofilament (HNF, B₄) liquid-crystalline phase depends on the fabrication methods, that is, UV-driven formation and template-assisted self-assembly in the nanoconfined geometry. As a result, uniaxially oriented HNFs with different helical structures were obtained, in which generation of the twisted-ribbon and cylindrical-ribbon polymorphs showed that even the molecular lattice has a different orientation. The detailed structures were directly observed by SEM and grazing-incidence X-ray diffraction with synchrotron radiation. The resultant polymorphs could be used in chiro-optical applications due to the capability for fine control of the helical structures.     

Directing two-dimensional molecular crystallization using guest templates

The use of a coronene guest template directs the formation of a 2D Kagomé network in preference to alternative close packed and parallel hydrogen-bonded structures of tetracarboxylic acid tectons self-assembled from solution on a graphite surface.     

Chemistry of singlet Oxygen. XXVII. Directing effect of methoxy group in additions to methoxystyrenes

A methoxy group on a styrene double bond directs O₂ attack $\text{cis}$, giving 1,4 addition if the phenyl is $\text{cis}$, or ene reaction if a CH₃ is $\text{cis}$. If no substituent is $\text{cis}$, 1,4 attack on the $\text{trans}$ phenyl occurs at a slower rate.     

Directing Aluminum Atoms into Energetically Favorable Tetrahedral Sites in a Zeolite Framework by Using Organic Structure‐Directing Agents

The Al location in zeolites can have massive influences on the zeolite properties because it directly correlates with the cationic active sites. Herein, the synthesis of IFR zeolites with controlled Al distribution at different tetrahedral sites (T sites) is reported. The computational calculations suggest that organic structure‐directing agents (OSDAs) used for zeolite synthesis can alter the energetically favorable T sites for Al. Zeolite products synthesized under identical conditions but with different OSDAs are found to have altered fractions of Al at different T sites in accordance with the energies derived from the zeolite–OSDA complexes. Our finding thus provides evidence for the ability of OSDAs to direct Al into more energetically favorable T sites, thereby offering rational synthetic guidelines for the selective placement of Al into specific crystallographic sites.     

Directing spatial disposition of ferrocene around homoadenine tetrads

We report synthesis and crystallographic studies of a ferrocenyl conjugate of adenine, where the hydrogen bonding interactions promote and stabilize nucleobase homotetrad formation.     

Directing group-controlled hydrosilylation: regioselective functionalization of alkyne

Pt(0)-catalyzed hydrosilylation of unsymmetric alkynes proceeds in a highly regioselective manner with a dimethylvinylsilyl (DMVS) group as the directing group. This hydrosilylation affords a single regioisomer of silylalkenes from propargylic and homopropargylic alcohol derivatives. DMVS also has an accelerating effect that allows group-selective hydrosilylation of the DMVS-attached alkyne prior to that of other alkynes. Combined hydrosilylation and transformation reactions of the resulting silylalkenes afford various tri-substituted alkenes and multi-oxy-functionalized compounds with high regioselectivity from unsymmetric alkynes.     

Directing the self-assembly of nanocrystals beyond colloidal crystallization

This article gives an overview of recent progress in the self-assembly of nanocrystals. Classic self-assembly of nanocrystals, so-called colloidal crystallization driven by van der Waals interactions, is highlighted first with an emphasis on the recent realization of binary colloidal crystals. Next, new developments in the integration of nanocrystals into clusters based on electrostatic interactions, hydrogen bonding and dipole-dipole interactions are summarized, shedding light on the defined control of the interactions between the nanocrystals. Finally, the fabrication of heterogenous nanocrystals, obtained via either phase selective modification at the water/oil interface or facet-selective crystal growth on non-spherical nanocrystals is discussed. These last materials may provide significant building blocks for mimicking molecular self-assembly.     

Directing energy transfer in discrete one-dimensional oligonucleotide-templated assemblies

Monodisperse DNA-templated one dimensional dye assemblies have been constructed in which the energy transfer can be directed. Fluorescence experiments suggest an optimum transfer efficiency for stacks of 30 bases long.     

导向剂法合成低硅X型沸石(LSX)

利用导向剂法(CDA)合成低硅[n(SiO₂)/n(Al₂O₃)≈2.0]X型沸石,用XRD,X射线荧光光谱测定样品的晶相及化学组成,并利用电子衍射对导向剂在老化过程中的结构变化进行了研究.结果表明,导向剂法合成速度快、杂晶极少.在晶化过程中的导向作用是一个持续过程,其活性不仅与配方、老化时间和温度有关,而且与其晶面的生长有关.     

Directing Role of Cage Structure for Crystallization of Zeolites

The directing mechanisms of liquid directing agents of zeolite Y and zeolite L were studied by means of light transmission, ultracentrifugation, NMR, XRD and “cross-exchange” experiments. It was discovered that not only microcfystals of zeolites, but also cage structures of zeolites play the directing role for crystallization of zeolites.