Functional group introduction and aromatic unit variation in a set of π‑conjugated macrocycles: revealing the central role of local and global aromaticity

π-Conjugated macrocycles are molecules with unique properties that are increasingly exploited for applications and the question of whether they can sustain global aromatic or antiaromatic ring currents is particularly intriguing. However, there are only a small number of experimental studies that investigate how the properties of π-conjugated macrocycles evolve with systematic structural changes. Here, we present such a systematic experimental study of a set of [2.2.2.2]cyclophanetetraenes, all with formally Hückel antiaromatic ground states, and combine it with an in-depth computational analysis. The study reveals the central role of local and global aromaticity for rationalizing the observed optoelectronic properties, ranging from extremely large Stokes shifts of up to 1.6 eV to reversible fourfold reduction, a highly useful feature for charge storage/accumulation applications. A recently developed method for the visualization of chemical shielding tensors (VIST) is applied to provide unique insight into local and global ring currents occurring in different planes along the macrocycle. Conformational changes as a result of the structural variations can further explain some of the observations. The study contributes to the development of structure–property relationships and molecular design guidelines and will help to understand, rationalize, and predict the properties of other π-conjugated macrocycles.

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Functional Group Introduction and Aromatic Unit Variation in a Set of π-Conjugated Macrocycles: Revealing the Central Role of Local and Global Aromaticity

10.26434/chemrxiv.14485002.v1 ◽

2021 ◽

Author(s):

Martina Rimmele ◽

Wojciech Nogala ◽

Maryam Seif-Eddine ◽

Maxie M. Roessler ◽

Martin Heeney ◽

...

Keyword(s):

Conformational Changes ◽

Structural Changes ◽

Molecular Design ◽

Experimental Studies ◽

Design Guidelines ◽

Structure Property ◽

Structural Variations ◽

Ring Currents ◽

Conjugated Macrocycles

π-Conjugated macrocycles are molecules with unique properties that are increasingly exploited for applications and the question of whether they can sustain global aromatic or antiaromatic ring currents is particularly intriguing. However, there are only a small number of experimental studies that investigate how the properties of π-conjugated macrocycles evolve with systematic structural changes. Here, we present such a systematic experimental study of a set of [2.2.2.2]cyclophanetetraenes, all with formally Hückel antiaromatic ground states, and combine it with an in-depth computational analysis. The study reveals the central role of local and global aromaticity for rationalizing the observed optoelectronic properties, ranging from extremely large Stokes shifts of up to 1.6 eV to reversible fourfold reduction, a highly useful feature for charge storage/accumulation applications. A recently developed method for the visualization of chemical shielding tensors (VIST) is applied to provide unique insight into local and global ring currents occurring in different planes along the macrocycle. Conformational changes as a result of the structural variations can further explain some of the observations. The study contributes to the development of structure–property relationships and molecular design guidelines and will help to understand, rationalize, and predict the properties of other π-conjugated macrocycles.

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Wood Pastures: A Transitional Habitat between Forests and Pastures for Dung Beetle Assemblages

Forests ◽

10.3390/f12010025 ◽

2020 ◽

Vol 12 (1) ◽

pp. 25

Author(s):

László Somay ◽

Viktor Szigeti ◽

Gergely Boros ◽

Réka Ádám ◽

András Báldi

Keyword(s):

Functional Group ◽

Animal Health ◽

Habitat Type ◽

Dung Beetle ◽

Dung Beetles ◽

Livestock Grazing ◽

Pitfall Traps ◽

Assemblage Composition ◽

Beetle Assemblages

Wood pastures are home to a variety of species, including the dung beetle. Dung beetles are an important functional group in decomposition. Specifically, in terms of livestock manure, they not only contribute to nutrient cycling but are key players in supporting human and animal health. Dung beetles, however, are declining in population, and urgent recommendations are needed to reverse this trend. Recommendations need to be based on solid evidence and specific habitats. Herein, we aimed to investigate the role of an intermediate habitat type between forests and pastures. Wood pastures are key areas for dung beetle conservation. For this reason, we compared dung beetle assemblages among forests, wood pastures, and grasslands. We complemented this with studies on the effects of dung type and season at three Hungarian locations. Pitfall traps baited with cattle, sheep, or horse dung were used in forests, wood pastures, and pasture habitats in spring, summer, and autumn. Dung beetle assemblages of wood pastures showed transient characteristics between forests and pastures regarding their abundance, species richness, Shannon diversity, assemblage composition, and indicator species. We identified a strong effect of season and a weak of dung type. Assemblage composition proved to be the most sensitive measure of differences among habitats. The conservation of dung beetles, and the decomposition services they provide, need continuous livestock grazing to provide fresh dung, as well as the maintenance of wood pastures where dung beetle assemblages typical of forests and pastures can both survive.

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A first-principles study of the atomic layer deposition of ZnO on carboxyl functionalized carbon nanotubes: the role of water molecules

Physical Chemistry Chemical Physics ◽

10.1039/d0cp05283c ◽

2021 ◽

Vol 23 (5) ◽

pp. 3467-3478

Author(s):

J. I. Paez-Ornelas ◽

H. N. Fernández-Escamilla ◽

H. A. Borbón-Nuñez ◽

H. Tiznado ◽

Noboru Takeuchi ◽

...

Keyword(s):

First Principles ◽

Ligand Exchange ◽

Functional Group ◽

Atomic Layer ◽

High Reactivity ◽

Water Molecules ◽

Exchange Reactions ◽

Layer Deposition ◽

The Right

Atomic description of ALD in systems that combine large surface area and high reactivity is key for selecting the right functional group to enhance the ligand-exchange reactions.

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The Role of Functional Group on the Exfoliation of Clay in Poly(L-lactide)

Macromolecular Rapid Communications ◽

10.1002/marc.200400452 ◽

2005 ◽

Vol 26 (3) ◽

pp. 183-187 ◽

Cited By ~ 59

Author(s):

Guang-Xin Chen ◽

Jai Bok Choi ◽

Jin San Yoon

Keyword(s):

Functional Group

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The role of the terminal functional group of self-assembled monolayers on fiber matrix adhesion

Journal of Applied Polymer Science ◽

10.1002/app.24388 ◽

2007 ◽

Vol 106 (1) ◽

pp. 462-469 ◽

Cited By ~ 6

Author(s):

E. Feresenbet ◽

D. Raghavan ◽

G. A. Holmes

Keyword(s):

Functional Group ◽

Self Assembled Monolayers ◽

Matrix Adhesion ◽

Assembled Monolayers ◽

Fiber Matrix ◽

Self Assembled ◽

Terminal Functional Group

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Effect of the Pyridine Substituent on the Role of the Phenol Functional Group in [Cu(pOHBz)2 (dPy)2 ] Complexes (pOHBz: p-Hydroxybenzoate, dPy= 4-Phenylpyridine, 4-Benzylpyridine, 3-Phenylpyridine).

ChemistrySelect ◽

10.1002/slct.201702833 ◽

2017 ◽

Vol 2 (35) ◽

pp. 11574-11580 ◽

Cited By ~ 2

Author(s):

Marta Sanchez-Sala ◽

Josefina Pons ◽

Ángel Álvarez-Larena ◽

Concepción Domingo ◽

José A. Ayllón

Keyword(s):

Functional Group

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Coronal transients: a summary

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1980.0236 ◽

1980 ◽

Vol 297 (1433) ◽

pp. 605-620 ◽

Cited By ~ 131

Keyword(s):

Interplanetary Medium ◽

Interplanetary Space ◽

Relative Role ◽

Transient Conditions ◽

Driving Mechanisms ◽

Field Gradients ◽

Ring Currents ◽

Ejection Process ◽

The Magnetic Field

Observations with orbiting coronagraphs have illuminated the role of coronal mass ejections in solar activity, and raised a number of questions concerning their origin, the nature of the forces driving the coronal material, and their signature in interplanetary space. Current models of the ejection process - including propagation of loops as a result of azimuthal field gradients, ring currents or a build-up of magnetic pressure from below - are summarized, as are magnetohydrodynamic codes intended to stimulate transient conditions. Metric radio observations, can, in principle, distinguish the relative role of the magnetic field in the ejection process; observations to date are surveyed. It is concluded that at present, no compelling evidence is available to distinguish between transient driving mechanisms, but future observations of the corona and interplanetary medium may resolve the present ambiguity.

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