Of Twists and Curves: Electronics, Photophysics, and Upcoming Applications of Non‐Planar Conjugated Organic Molecules

Abstract

Non‐planar conjugated organic molecules (NPCOMs) contain π‐conjugation across their length and also exhibit asymmetry in their conformation. In other words, certain molecular fragments in NPCOMs are either twisted or curved out of planarity. This conformational asymmetry in NPCOMs leads to non‐uniform charge‐distribution across the molecule, with important photophysical and electronic consequences such as altered thermodynamic stability, chemical reactivity, as well as materials properties. Majorly, NPCOMs can be classified as having either Fused or Rotatable architectures. NPCOMs have been the focus of significant scientific attention in the recent past due to their exciting photophysical behavior that includes intramolecular charge‐transfer (ICT), thermally activated delayed fluorescence (TADF) and long‐lived charge‐separated states. In addition, they also have many useful materials characteristics such as biradical character, semi‐conductivity, dynamic conformations, and mechanochromism. As a result, rational design of NPCOMs and mapping their structure‐property correlations has become imperative. Researchers have executed conformational changes in NPCOMs through a variety of external stimuli such as pH, temperature, anions‐cations, solvent, electric potential, and mechanical force in order to tailor their photophysical, optoelectronic and magnetic properties. Converging to these points, this review highlights the lucrative electronic features, photophysical traits and upcoming applications of NPCOMs by a selective survey of the recent scientific literature.

Design of BODIPY dyes as triplet photosensitizers: electronic properties tailored for solar energy conversion, photoredox catalysis and photodynamic therapy

“…19) and helicenes, 20,21 will not be discussed in this review; interested readers can refer for instance to recently published reviews. 22,23…”

Azulene Bridged π‐Distorted Chromophores: The Influence of Structural Symmetry on Optoelectrochemical and Photovoltaic Parameters

“…[30] As shown in Figure 5, the two orthogonal =C(CN) 2 groups of TATC1 and TATC2 displayed a torsional potential (Θ) of À 104°and À 112°respectively, agreeing to the -anti-clinal conformation. Though this deviation from co-planarity could hamper an effective π-delocalization, [31] the TCBD group could potentially influence the decrease of πorbital energies to contribute for the acceptor character. [32] On the other hand, the CÀ C single bond linking the 2-thienyl and =C(CN) 2 group in TATC1 (1.36 Å) is shorter than that in TATC2 (1.53 Å).…”

Discrete π Stack of a Tweezer‐Shaped Naphthalenediimide–Anthracene Conjugate

“…Würthner and co‐workers have reported discrete π stacks in the aggregation of the related family of perylenediimides, based on the foldamer approach . However, it still remains instructive to develop more efficient and viable strategies to construct supramolecular discrete π stacks based on flexible π frameworks . To this end, we sought to introduce orthogonal intramolecular π NDI ⋅⋅⋅ π NDI interactions and hydrogen bonding to shape flexible and discrete π stacks in the NDI system.…”