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

Chiral Crystalline Sponges for the Absolute Structure Determination of Chiral Guests

Chiral crystalline sponges with preinstalled chiral references were synthesized. On the basis of the known configurations of the chiral references, the absolute structures of guest compounds absorbed in the pores of the crystalline sponges can be reliably determined without crystallization or chemical modification

X‑ray Structure Analysis of Ozonides by the Crystalline Sponge Method

The crystalline sponge method was used for the X-ray structure analysis of ozonide compounds. As this new technique requires only microgram quantities of the samples, structural analysis can be conducted without product isolation, isomer separation, or crystallization and most importantly without any risk of explosion

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