Diels–Alder via Molecular Recognition in a Crystalline Molecular Flask

In the pore of a porous coordination network, Diels–Alder reactants, a diene and a dienophile, are recognized by donor–acceptor and multiple H-bond interactions, respectively, and fixed at ideal positions for the reaction. Heating the crystals promoted the Diels–Alder reactions with enhanced reactivity and controlled regioselectivity as clearly monitored by in situ X-ray crystallography

X‑ray Snapshot Observation of Palladium-Mediated Aromatic Bromination in a Porous Complex

Pd-mediated aromatic bromination is intriguing to synthetic and organometallic chemists due to both its synthetic utility and, more importantly, a proposed mechanism involving an uncommon Pd­(IV)/Pd­(II) catalytic cycle. Here, we report an X-ray snapshot observation of a Pd reaction center during a Pd-mediated aromatic bromination in a single crystal of a porous coordination network crystalline scaffold. Upon treatment of a single crystal with <i>N</i>-bromosuccinimide, sequential X-ray snapshots revealed that the aryl-Pd­(II)-L species embedded in the network pores was converted to the brominated aryl product through a transient aryl-Pd­(II)-Br species, which is normally unobservable because of its rapid dimerization into insoluble Pd₂(μ-Br)₂ species. Though the reaction pathway may be biased by the crystalline state, the new X-ray snapshot method relies on crystalline flasks to provide important mechanistic insight

Networked-Cage Microcrystals for Evaluation of Host–Guest Interactions

We have developed a new synthetic protocol for the preparation of a microcrystalline powder (median size: <i>X</i>₅₀ = 25 μm) of networked M₆L₄ cages <b>1a</b> for the stationary phase of an affinity column on a greater than 50 g scale. Analogously to large single crystals <b>1b</b> (<i>X</i>₅₀ ≈ 0.5 mm), microcrystals <b>1a</b> accommodate guest molecules tetrathiafulvalene (TTF) and fullerene (C₆₀) at up to 32 and 35 wt %, respectively. Importantly, the host–guest interactions within networked cages could be evaluated in terms of the retention time from HPLC analysis by using microcrystals <b>1a</b> as the stationary phase. In this way, favorable guests for networked cages <b>1</b> and even solution M₆L₄ cage <b>2</b> could easily be assessed by HPLC

Cyclo‑<i>meta</i>‑phenylene Revisited: Nickel-Mediated Synthesis, Molecular Structures, and Device Applications

From a one-pot nickel-mediated Yamamoto-type coupling reaction of <i>m</i>-dibromobenzene, five congeners of [<i>n</i>]­cyclo-<i>meta</i>-phenylenes were synthesized and fully characterized. The [<i>n</i>]­cyclo-<i>meta</i>-phenylenes possessed a commonly shared arylene unit and intermolecular contacts but varied in packing structures in the crystalline solid state. Columnar assembly of larger congeners yielded nanoporous crystals with carbonaceous walls to capture minor protic or aliphatic solvent molecules. The concise and scalable synthesis allowed exploration of the macrocyclic hydrocarbons as bipolar charge carrier transport materials in organic light-emitting diode devices

Modular Synthesis of Aromatic Hydrocarbon Macrocycles for Simplified, Single-Layer Organic Light-Emitting Devices

A method for the modular synthesis of aromatic hydrocarbon macrocycles has been developed for base materials in single-layer organic light-emitting devices. The method with Ir-catalyzed direct C–H borylation and Suzuki–Miyaura coupling was concise and scalable, which allowed for a gram-scale preparation of aromatic hydrocarbon macrocycles that have bulky substituents at the periphery. The new arylated hydrocarbon macrocycles enabled a quantitative electro-optical conversion in organic light-emitting devices with a phosphorescent emitter, which is, notably, in a single-layer architecture consisting of two regions of doped and undoped materials. The highest external quantum efficiencies reached 24.8%, surpassing those of previous hydrocarbon base materials