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Pentacoordinate Al catalysts comprising bipyridine (bpy) and phenanthroline (phen) backbones were synthesized and their catalytic activity in epoxide/anhydride copolymerization was investigated and compared to ( t-Bu salph)AlCl. Stoichiometric reactions of tricyclic anhydrides with Al alkoxide complexes produced ring-opened products that were characterized by NMR spectroscopy, mass spectrometry, and X-ray crystallography, revealing key regio- and stereochemical aspects. 

A halogen-bonded supramolecular ladder comprised of a novel pyrimidine-based cyclobutane photoproduct synthesized in the organic solid state via a [2 + 2] photoreaction is reported. The photoproduct rctt -tetrakis(5′-pyrimidyl)cyclobutane functions as rungs while the linear divergent halogen-bond donor 1,4-diiodoperchlorobenzene acts as the rails. Our report also confirms the structure and stereochemistry of the tetrapyrimidyl cyclobutane ring system. 

A halogen-bonded eight-fold interpenetrated diamondoid net was constructed employing a node generated in the solid state. Specifically, co-crystallization of a tetrahedral-like tecton, rctt -tetrakis(4-pyridyl)cyclobutane (4,4′-TPCB), combined with a rigid halogen-bond donor, 1,4-diiodoperchlorobenzene, achieved a diamondoid architecture. In the co-crystal, 4,4′-TPCB is found to form three types of linkages based on one cis - and two trans -orientations enabled by the intrinsic rctt -stereochemisty of the central cyclobutane ring. Thus, 4,4′-TPCB is able to adapt to the constraints of the diamondoid net owing to the flexibility of the pendant 4-pyridyl groups. 

The formation of a photoreactive cocrystal based upon 1,2-diiodoperchlorobenzene ( 1,2-C 6 I 2 Cl 4 ) and trans -1,2-bis(pyridin-4-yl)ethylene ( BPE ) has been achieved. The resulting cocrystal, 2( 1,2-C 6 I 2 Cl 4 )·( BPE ) or C 6 Cl 4 I 2 ·0.5C 12 H 10 N 2 , comprises planar sheets of the components held together by the combination of I...N halogen bonds and halogen–halogen contacts. Notably, the 1,2-C 6 I 2 Cl 4 molecules π-stack in a homogeneous and face-to-face orientation that results in an infinite column of the halogen-bond donor. As a consequence of this stacking arrangement and I...N halogen bonds, molecules of BPE also stack in this type of pattern. In particular, neighbouring ethylene groups in BPE are found to be parallel and within the accepted distance for a photoreaction. Upon exposure to ultraviolet light, the cocrystal undergoes a solid-state [2 + 2] cycloaddition reaction that produces rctt -tetrakis(pyridin-4-yl)cyclobutane ( TPCB ) with an overall yield of 89%. A solvent-free approach utilizing dry vortex grinding of the components also resulted in a photoreactive material with a similar yield.