Crossover Sorption of C H /CO and C H /C H in Soft Porous Coordination Networks.

Porous sorbents are materials that are used for various applications, including storage and separation. Typically, the uptake of a single gas by a sorbent decreases with temperature, but the relative affinity for two similar gases does not change. However, in this study, we report a rare example of "crossover sorption," in which the uptake capacity and apparent affinity for two similar gases reverse at different temperatures.

Selective sorption of oxygen and nitrous oxide by an electron donor-incorporated flexible coordination network.

Incorporating strong electron donor functionality into flexible coordination networks is intriguing for sorption applications due to a built-in mechanism for electron-withdrawing guests. Here we report a 2D flexible porous coordination network, [Ni(4,4'-bipyridine)(VTTF)]n(1) (where HVTTF = 2,2'-[1,2-bis(4-benzoic acid)-1,2ethanediylidene]bis-1,3-benzodithiole), which exhibits large structural deformation from the as-synthesized or open phase (1α) into the closed phase (1β) after guest removal, as demonstrated by X-ray and electron diffraction. Interestingly, upon exposure to electron-withdrawing species, 1β reversibly undergoes guest accommodation transitions; 1α⊃O (90 K) and 1α⊃NO (185 K).

Laterally π-Extended Dithia[6]helicenes with Heptagons: Saddle-Helix Hybrid Molecules.

A laterally π-extended dithia[6]helicene 1, representing an interesting saddle-helix hybrid molecule containing an unusual heptagon, has been synthesized by MoCl-mediated oxidative stitching of tetrakis(thienylphenyl)naphthalene precursor 2 involving reactive-site capping by chlorination and subsequent Pd-mediated dechlorination of tetrachlorinated intermediate 1-Cl. Highly distorted, wide helical structures of dithia[6]helicenes (1 and 1-Cl) were clarified by single-crystal X-ray diffraction analyses where heterochiral slipped π-π stacking was displayed in a one-dimensional fashion. Notably, theoretical studies on the thermodynamic behavior of 1 predicted an extraordinarily high isomerization barrier of 49.

Synthesis, properties, and crystal structures of π-extended double [6]helicenes: contorted multi-dimensional stacking lattice.

The synthesis and properties of a new π-extended double [6]helicene 2 and a dithia[6]helicene 3 are described. Compared to the previously reported parent double-helicene molecule 1, the introduction of n-butyl groups successfully improved the solubility, which allowed an experimental investigation into the electronic structure of 2 and 3 by photophysical measurements and cyclic voltammetry. The characteristic two-blade propeller structures of 2 and 3 were unambiguously determined by single-crystal X-ray diffraction analysis.

Thiophene-Fused π-Systems from Diarylacetylenes and Elemental Sulfur.

A simple yet effective method for the formation of thiophene-fused π-systems is reported. When arylethynyl-substituted polycyclic arenes were heated in DMF in the presence of elemental sulfur, the corresponding thiophene-fused polycyclic arenes were obtained via cleavage of the ortho-C-H bond. Thus, arylethynylated naphthalenes, fluoranthenes, pyrenes, corannulenes, chrysenes, and benzo[c]naphtho[2,1-p]chrysenes were effectively converted into the corresponding thiophene-fused π-systems.

Corannulene-Helicene Hybrids: Chiral π-Systems Comprising Both Bowl and Helical Motifs.

Two distinct structural elements that render π-systems nonplanar, i.e., geodesic curvature and helical motifs, have been combined into new polyarenes that contain both features.

Synthesis and Structural Features of Quadruple Helicenes: Highly Distorted π Systems Enabled by Accumulation of Helical Repulsions.

Quadruple helicenes, bearing dithia[6]helicene and [5]helicene substructures, were prepared by a well-controlled Scholl reaction. The 4-fold helicity provides 9 stereoisomers including 4 pairs of enantiomers and 1 meso isomer. Among them, differently distorted structures of a propeller-shaped isomer (QH-A) and a saddle-shaped isomer (QH-B) were unambiguously determined by X-ray crystallography.

Synthesis, Structures, and Properties of π-Extended Double Helicene: A Combination of Planar and Nonplanar π-Systems.

The synthesis, structures, and properties of a π-extended double helicene 1 are described. This double helicene 1 was synthesized by a four-fold oxidative C-H biphenylation of naphthalene followed by the Scholl reaction or via five steps including the Suzuki-Miyaura cross-coupling reaction and the Scholl reaction. Due to the two helical substructures, 1 has three isomers, i.