Stable Bifunctional Perylene Imide Radicals for High-Performance Organic-Lithium Redox-Flow Batteries

Synthesis, Characterization, and Properties of Sila-Annulated Phenanthrene Imides

A series of sila-annulated phenanthrene imides were synthesized through a three-step synthetic route, which represent a hybrid class of biphenyl-based π-conjugated molecules incorporating an imide unit and silole. A comprehensive investigation of their structural, photophysical, and electronic properties was studied by experiment and theoretical calculations. Notably, sila-annulated phenanthrene imides with significant aggregation-induced emission (AIE) properties were observed.

Recent Developments on Electroactive Organic Electrolytes for Non-Aqueous Redox Flow Batteries: Current Status, Challenges, and Prospects

The ever-increasing threat of climate change and the depletion of fossil fuel resources necessitate the use of solar- and wind-based renewable energy sources. Large-scale energy storage technologies, such as redox flow batteries (RFBs), offer a continuous supply of energy. Depending on the nature of the electrolytes used, RFBs are broadly categorized into aqueous redox flow batteries (ARFBs) and non-aqueous redox flow batteries (NARFBs). ARFBs suffer from various problems, including low conductivity of electrolytes, inferior charge/discharge current densities, high-capacity fading, and lower energy densities. NARFBs offer a wider potential window and range of operating temperatures, faster electron transfer kinetics, and higher energy densities. In this review article, a critical analysis is provided on the design of organic electroactive molecules, their physiochemical/electrochemical properties, and various organic solvents used in NARFBs. Furthermore, various redox-active organic materials, such as metal-based coordination complexes, quinones, radicals, polymers, and miscellaneous electroactive species, explored for NARFBs during 2012-2023 are discussed. Finally, the current challenges and prospects of NARFBs are summarized.

Chemical doping of unsubstituted perylene diimide to create radical anions with enhanced stability and tunable photothermal conversion efficiency

N-doping of perylene diimides (PDIs) to create stable radical anions is significant for harvesting photothermal energy due to their intensive absorption in the near-infrared (NIR) region and non-fluorescence. In this work, a facile and straightforward method has been developed to control the doping of perylene diimide to create radical anions using organic polymer polyethyleneimine (PEI) as a dopant. It was demonstrated that PEI is an effective polymer-reducing agent for the n-doping of PDI toward the controllable generation of radical anions. In addition to the doping process, PEI could suppress the self-assembly aggregation and improve the stability of PDI radical anions. Tunable NIR photothermal conversion efficiency (maximum 47.9%) was also obtained from the radical-anion-rich PDI-PEI composites. This research provides a new strategy to tune the doping level of unsubstituted semiconductor molecules for varying yields of radical anions, suppressing aggregation, improving stability, and obtaining the highest radical anion-based performance.

Enantioselective Recognition of Helicenes by a Tailored Chiral Benzo[ghi]perylene Trisimide π-Scaffold

Enantioselective molecular recognition of chiral molecules that lack specific interaction sites for hydrogen bonding or Lewis acid-base interactions remains challenging. Here we introduce the concept of tailored chiral π-surfaces toward the maximization of shape complementarity. As we demonstrate for helicenes it is indeed possible by pure van-der-Waals interactions (π-π interactions and CH-π interactions) to accomplish enantioselective binding. This is shown for a novel benzo[ghi]perylene trisimide (BPTI) receptor whose π-scaffold is contorted into a chiral plane by functionalization with 1,1'-bi-2-naphthol (BINOL). Complexation experiments of enantiopure (P)-BPTI with (P)- and (M)-[6]helicene afforded binding constants of 10 700 M^-1 and 550 M^-1 , respectively, thereby demonstrating the pronounced enantiodifferentiation by the homochiral π-scaffold of the BPTI host. The enantioselective recognition is even observable by the naked eye due to a specific exciplex-type emission originating from the interacting homochiral π-scaffolds of electron-rich [6]helicene and electron-poor BPTI.

Rescuing the solid-state fluorescence of perylene diimide dyes by host–guest isolation

A host molecule with an open and flexible backbone was synthesized and is capable of recognizing various perylene diimide dyes. The host exhibits unique universality in improving the solid-state fluorescence of perylene diimide dyes.

Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area

A series of perylene bisimide (PBI) dyes bearing various aryl substituents in 1,6,7,12 bay positions has been synthesized by Suzuki cross-coupling reaction. These molecules exhibit an exceptionally large and conformationally fixed twist angle of the PBI π-core due to the high steric congestion imparted by the aryl substituents in bay positions. Single crystal X-ray analyses of phenyl-, naphthyl- and pyrenyl-functionalized PBIs reveal interlocked π-π-stacking motifs, leading to conformational chirality and the possibility for the isolation of enantiopure atropoisomers by semipreparative HPLC. The interlocked arrangement endows these molecules with substantial racemization barriers of about 120 kJ mol-1 for the tetraphenyl- and tetra-2-naphthyl-substituted derivatives, which is among the highest racemization barriers for axially chiral PBIs. Variable temperature NMR studies reveal the presence of a multitude of up to fourteen conformational isomers in solution that are interconverted via smaller activation barriers of about 65 kJ mol-1 . The redox and optical properties of these core-twisted PBIs have been characterized by cyclic voltammetry, UV/Vis/NIR and fluorescence spectroscopy and their respective atropo-enantiomers were further characterized by circular dichroism (CD) and circular polarized luminescence (CPL) spectroscopy.

Molecular Engineering of Aromatic Imides for Organic Secondary Batteries

Aromatic imides are a class of attractive organic materials with inherently electroactive groups and large π electron-deficient scaffolds, which hold potential as electrode materials for organic secondary batteries (OSBs). However, the undecorated aromatic imides are usually plagued by low capacity, high solubility in electrolyte, and poor electronic/ionic conductivity. Molecular engineering has been demonstrated to be an effective strategy to address unsatisfying characteristics of the aromatic imides, thereby expanding their scope for applications in OSBs. In this review, the recent research progress in modulation of the capacity, dissolution, and electronic/ionic conductivity of aromatic imides for organic lithium batteries, organic sodium batteries, and redox flow batteries are summarized. In addition, the challenge and prospective of aromatic imides in organic secondary battery applications are also discussed.

Synthesis and self-assembly of a penta[60]fullerene bearing benzo[ghi]perylenetriimide units

New penta(organo)fullerene bearing five benzo[ghi]perylenetriimide units has been synthesized to form self-assemblies through π–π interactions.

Recent Advances in the Development of Organic and Organometallic Redox Shuttles for Lithium-Ion Redox Flow Batteries

In recent years, redox flow batteries (RFBs) and derivatives have attracted wide attention from academia to the industrial world because of their ability to accelerate large-grid energy storage. Although vanadium-based RFBs are commercially available, they possess a low energy and power density, which might limit their use on an industrial scale. Therefore, there is scope to improve the performance of RFBs, and this is still an open field for research and development. Herein, a combination between a conventional Li-ion battery and a redox flow battery results in a significant improvement in terms of energy and power density alongside better safety and lower cost. Currently, Li-ion redox flow batteries are becoming a well-established subdomain in the field of flow batteries. Accordingly, the design of novel redox mediators with controllable physical chemical characteristics is crucial for the application of this technology to industrial applications. This Review summarizes the recent works devoted to the development of novel redox mediators in Li-ion redox flow batteries.

Anion–π interactions in lithium–organic redox flow batteries

The interactions between the electrolyte anions and electron-deficient redox-active organic molecules (anion–π interactions) have strong influences on the battery properties due to the anion–π-induced formation of radical anions or sandwich-like aggregates.

1,1′-Bi(2-naphthol-4,5-dicarboximide)s: blue emissive axially chiral scaffolds with aggregation-enhanced emission properties

Novel electron-deficient 1,1′-binaphthol derivatives bearing two dicarboximide groups at the peri-positions show intense blue luminescence and aggregation-enhanced emission characteristics.

An electron-deficient nanosized polycyclic aromatic hydrocarbon with enhanced anion–π interactions

A super-electron-deficient nano-sized polycyclic aromatic hydrocarbon with six imide groups at the corners has been synthesized, which exhibited enhanced anion–π interactions with various anions.