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Nanoporous solids, including metal-organic frameworks (MOFs), have long been known to capture small molecules by adsorption on their pore surfaces. Liquids are also known to accommodate small molecules by dissolution. These two processes have been recognized as fundamentally distinct phenomena because of the different nature of the medium—solids and liquids. Here, we report a dissolution-like gas accommodation so-called "adsorptive-dissolution" behavior in a MOF (PFAC-2) with pores densely filled with perfluoroalkyl chains. PFAC-2 does not have solvent-accessible voids; nevertheless, it captures oxygen molecules without changing the framework structure, analogous to molecular dissolution into liquids. Moreover, we demonstrate the selective capture of O2 by PFAC-2 in a mixture of O2 and Ar, which are difficult to separate due to their similarities such as boiling point and molecular size. Our results show the integration of molecular adsorption into nanospaces and dissolution into fluorous solvents, which can guide the design of crystalline adsorbents for selective molecular trapping and gas separation. A densely fluorinated nanospace demonstrates the integration of adsorption and dissolution, so-called "adsorptive-dissolution", which enables selective adsorption of O2 over Ar. [ABSTRACT FROM AUTHOR]

Dithieno[a,e]penalenes (DTPs) with various substituents were synthesized as a class of antiaromatic compounds. Annulation of thiophene rings imparts the pentalene moiety with high thermal stability even without bulky substituents, while retaining antiaromaticity. The higher magnitude of antiaromaticity in DTPs, in addition to the differences in the electronic structures of the fused aromatic rings, resulted in a narrower HOMO–LUMO gap than that of the corresponding dibenzo[a,e]pentalene analog, giving rise to red‐shifted electronic absorption that reaches the near‐infrared region. Moreover, systematic investigations on the solid‐state packing structure revealed that DTPs prefer offset face‐to‐face packing motifs rather than face‐centered π–π stacking. In particular, the thienyl‐substituted DTP bearing hydrophilic side chains exhibited thermochromic behavior in polar solvents, which was ascribed to the formation of aggregates. [ABSTRACT FROM AUTHOR]

Keywords: antiaromaticity; diazapentalene; imines; conjugation; thiophenes EN antiaromaticity diazapentalene imines conjugation thiophenes 16057 16057 1 11/24/21 20211122 NES 211122 B The strength of the antiaromaticity of the title compounds b is represented by the power of a phoenix. Antiaromaticity, diazapentalene, imines, conjugation, thiophenes This is a metaphor for the fact that the antiaromaticity of the 8 -electron system pentalene is substantially impaired by nitrogen doping, but is restored by the condensation of thiophene rings. [Extracted from the article]

Keywords: antiaromaticity; pentalene; thermochromism; thiophene; conjugation EN antiaromaticity pentalene thermochromism thiophene conjugation 1478 1478 1 01/23/21 20210121 NES 210121 B Dancing people parade along the rings b : The cover image depicts the movement of electrons on tetracyclic -conjugated systems under a magnetic field. While the annulation of benzene rings with a pentalene moiety resulted in the local aromatic character in the six-membered rings, the thiophene-fused analog retains the pronounced antiaromatic character of pentalene moiety. While the annulation of benzene rings with a pentalene moiety resulted in the local aromatic character in the six-membered rings, the thiophene-fused analog retains the pronounced antiaromatic character of pentalene moiety. [Extracted from the article]

We present here a group of Azo-BF 2 photoswitches that store and release energy in response to visible light irradiation. Unmodified Azo-BF 2 switches have a planar structure with a large π-conjugation system, which hinders E-Z isomerization when in a compacted state. To address this challenge, we modified the switches with one or two aliphatic groups, which altered the intermolecular interactions and arrangement of the photochromes in the solid state. The derivative with two substituents exhibited a non-planar configuration that provided particularly large conformational freedom, allowing for efficient isomerization in the solid phase. Our discovery highlights the potential of using double aliphatic functionalization as a promising approach to facilitate solid-state switching of large aromatic photoswitches. This finding opens up new possibilities for exploring various photoswitch candidates for molecular solar thermal energy storage applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A thiophene-fused 1,4-diazapentalene (TAP) was rationally designed and synthesized as a C=N-containing 4n π-electron system that exhibits restored antiaromaticity impaired by the doping with C=N bonds. X-ray crystallographic analysis and quantum chemical calculations revealed that the annulation of thiophene rings with the 1,4-diazapentalene moiety resulted in a much higher antiaromaticity than the pristine 1,4-diazapentalene. These effects can be ascribed to the reduced bond alternation of the eight-membered-ring periphery caused by stabilization of the less-stable bond-shifted resonance structure upon increasing the degree of substitution of imine moieties. Consequently, TAP underwent facile hydrogenation even under mild conditions because of its pronounced antiaromaticity and the high aromaticity of the corresponding hydrogenated product H 2 -TAP. In addition, the electrophilic C=N moieties in TAP led to the formation of a dense π-stacked structure. These results highlight the effect of partial replacement of C=C bonds with C=N bonds in antiaromatic π-electron systems., (© 2021 Wiley-VCH GmbH.)

Invited for the cover of this issue are Aiko Fukazawa and co-workers at Kyoto University and Nagoya University. The image depicts the π-electrons as people to highlight the effect of fused aromatic rings in the antiaromatic π-electron systems. Read the full text of the article at 10.1002/chem.202004244., (© 2021 Wiley-VCH GmbH.)