Cover Feature: Azobenzene‐Substituted Triptycenes: Understanding the Exciton Coupling of Molecular Switches in Close Proximity (Chem. Eur. J. 38/2022)

Abstract

You can′t separate this couple: One of the azo‐substituted tripycenes synthesized in this work is highlighted in front of its UV‐Vis absorption spectrum. Even though the azobenzenes are separated by a sp3 center, they experience excitonic coupling, as illustrated by the lightning. More information can be found in the Research Article by H. A. Wegner and co‐workers (DOI: 10.1002/chem.202200972). Design by Felix Bernt.

Exciton States of Azobenzene Aggregates: A First‐Principles Study

“…Furthermore, several works have addressed exciton formation in covalently linked multiazobenzenes. [38][39][40][41][42][43][44][45][46] Here, we expand the previous studies by treating large 1D and 2D clusters of azobenzenes (up to 18 molecules) by means of first-principles quantum chemical methods such as timedependent long-range corrected density functional theory (TD-lc-DFT) and ab initio configuration interaction singles (CIS). Nowadays, thanks to the progress in computational resources, these methods can be applied to large molecules/clusters of molecules, and, importantly, they do not suffer from the so-called charge transfer (CT) problem of TD-DFT.…”

Exciton states of azobenzene aggregates: A first-principles study

“…Furthermore, several works have addressed exciton formation in covalently linked multiazobenzenes. [38][39][40][41][42][43][44][45][46] Here, we expand the previous studies by treating large 1D and 2D clusters of azobenzenes (up to 18 molecules) by means of first-principles quantum chemical methods such as time-dependent long-range corrected density functional theory (TD-lc-DFT) and ab initio configuration interaction singles (CIS). Nowadays, thanks to the progress in computational resources, these methods can be applied to large molecules / clusters of molecules, and, importantly, they do not suffer from the so-called charge transfer (CT) problem of TD-DFT.…”

Correlation between Absorption and Substitution of Photochromic 1,2‐Bis(thienyl)ethenes (BTEs) Using Modified Spectroscopic Hammett Equations

“…The concept of odd/even, alternant/non-alternant conjugated hydrocarbons [24] and the division of carbon atoms into two sets, starred and unstarred, undoubtedly has led to a deeper understanding of the dependence of conjugation on chemical as well as physical properties of chemical compounds. [25] The reference reactions for the determination of equation [1], [2], and [3] conjugated hydrocarbons display the differences of the reference reactions with respect to the conjugation, as the carboxylate group is joined to the benzene ring via an unstarred position (o (red)), whereas the exocyclic substituents of the dimethylbenzyl cation and the phenolate, for which the benzyl cation and anion are the isoconjugate equivalents, are starred positions in direct conjugation to the ring.…”

“…Photochromism is the reversible photochemical transformation of one isomer of a chemical compound into another which differs in its spectroscopic properties. [1] Some examples of photochromic molecules are shown in Scheme 1, the switchable properties of which are based on cis-trans-isomerism (azobenzenes 1), [2] ring-closure reactions (spiropyrans 2, [3] furylfulgides 3) [4] or disproportionations to form radical cations and radical anions from mesomeric betaines such as punicines 4. [5] The reconstitution of the initial isomer can be performed photochemically (P-type) or thermally (T-type), [1] whereby the latter mentioned isomerization is undesired for applications in optical devices.…”

“…[22] For reactions, in which the substituent X can enter into direct resonance interaction with the reaction site in the transition site, modified σ-values, referred to as σ + and σ À values, have been introduced by H. C. Brown. [23] The σ p + values were determined as rate constants of the S N 1 reaction of cumyl chlorides in 90 % acetone/water and calculated as expressed by Equation (2).…”