Direct Evidence of Significantly Different Chemical Behavior and Excited‐State Dynamics of 1,7‐ and 1,6‐Regioisomers of Pyrrolidinyl‐Substituted Perylene Diimide

Novel bay‐functionalized perylene diimides with additional substitution sites close to the perylene core have been prepared by the reaction between 1,7(6)‐dibromoperylene diimide 6 (dibromo‐PDI) and 2‐(benzyloxymethyl)pyrrolidine 5 . Distinct differences in the chemical behaviors of the 1,7‐ and 1,6‐regioisomers have been discerned. While the 1,6‐dibromo‐PDI produced the corresponding 1,6‐bis‐substituted derivative more efficiently, the 1,7‐dibromo‐PDI underwent predominant mono‐debromination, yielding a mono‐substituted PDI along with a small amount of the corresponding 1,7‐bis‐substituted compound. By varying the reaction conditions, a controlled stepwise bis‐substitution of the bromo substituents was also achieved, allowing the direct synthesis of asymmetrical 1,6‐ and 1,7‐PDIs. The compounds were isolated as individual regioisomers. Fullerene (C₆₀) was then covalently linked at the bay region of the newly prepared PDIs. In this way, two separate sets of perylene diimide–fullerene dyads, namely single‐bridged (SB‐1,7‐PDI‐C₆₀ and SB‐1,6‐PDI‐C₆₀) and double‐bridged (DB‐1,7‐PDI‐C₆₀ and DB‐1,6‐PDI‐C₆₀), were synthesized. The fullerene was intentionally attached at the bay region of the PDI to achieve close proximity of the two chromophores and to ensure an efficient photoinduced electron transfer. A detailed study of the photodynamics has revealed that photoinduced electron transfer from the perylene diimide chromophore to the fullerene occurs in all four dyads in polar benzonitrile, and also occurs in the single‐bridged dyads in nonpolar toluene. The process was found to be substantially faster and more efficient in the dyads containing the 1,7‐regioisomer, both for the singly‐ and double‐bridged molecules. In the case of the single‐bridged dyads, SB‐1,7‐PDI‐C₆₀ and SB‐1,6‐PDI‐C₆₀, different relaxation pathways of their charge‐separated states have been discovered. To the best of our knowledge, this is the first observation of photoinduced electron transfer in PDI‐C₆₀ dyads in a nonpolar medium.     

One donor–two acceptor (D–A1)‐(D–A2) random terpolymers containing perylene diimide,naphthalene diimide,and carbazole units

A series of one donor–two acceptor (D–A₁)‐(D–A₂) random terpolymers containing a 2,7‐carbazole donor and varying compositions of perylene diimide (PDI) and naphthalene diimide (NDI) acceptors was synthesized via Suzuki coupling polymerization. The optical properties of the terpolymers are weighted sums of the constituent parent copolymers and all show strong absorption over the 400 to 700 nm range with optical bandgaps ranging from 1.77 to 1.87 eV, depending on acceptor composition. The copolymers were tested as acceptor materials in bulk heterojunction all‐polymer solar cells using poly[(4,8‐bis‐(2‐ethylhexyloxy)‐benzo[1,2‐b;4,5‐b′]dithiophene)‐2,6‐diyl‐alt‐(4‐(2‐ethylhexanoyl)‐thieno[3,4‐b]thiophene)‐2,6‐diyl] (PBDTTT‐C) as the donor material. In contrast to the optoelectronic properties, the measured device parameters are not composition dependent, and rather depend solely on the presence of the NDI unit, where the devices containing any amount of NDI perform half as well as those using the parent polymer containing only carbazole and PDI. Overall this is the first example of a one donor–two acceptor random terpolymer system containing perylene diimide (PDI) and naphthalene diimide (NDI) acceptor units, and demonstrates a facile method of tuning polymer optoelectronic properties while minimizing the need for complicated synthetic and purification steps. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3337–3345     

Highly Soluble Porphyrin (TPP)-Perylene Diimide (PDI) Dyad and Triad:Synthesis and Spectroscopic Studies

Novel porphyrin‐perylene diimide dyad (TPP‐PDI) and porphyrin‐perylene diimide‐porphyrin triad (TPP‐PDI‐TPP) were synthesized and characterized. Their structure and properties were studied by UV, FL, ¹H NMR, MS, elemental analysis, etc. The variation of fluorescence feature and UV spectra of TPP‐PDI‐TPP triad were investigated at different concentration of CF₃COOH in THF. The incorporation of CF₃COOH leads to the closure of the efficient charge transfer decay. After protonation of porphyrin units, the fluorescence intensity of TPP‐PDI‐TPP triad increased greatly. The fluorescence intensity of TPP‐PDI‐TPP triad restored after addition of triethylamine into the solution. Thus, TPP‐PDI‐TPP triad was a proton‐type fluorescence switch based on acid‐base control. Moreover, different from porphyrin‐perylene type molecular switches reported before, this TPP‐PDI‐TPP triad has wonderful solubility in organic solvents.     

Designing a Perylene Diimide/Fullerene Hybrid as Effective Electron Transporting Material in Inverted Perovskite Solar Cells with Enhanced Efficiency and Stability

Electron transport materials (ETM) play an important role in the improvement of efficiency and stability for inverted perovskite solar cells (PSCs). This work reports an efficient ETM, named PDI‐C₆₀, by the combination of perylene diimide (PDI) and fullerene. Compared to the traditional PCBM, this strategy endows PDI‐C₆₀ with slightly shallower energy level and higher electron mobility. As a result, the device based on PDI‐C₆₀ as electron transport layer (ETL) achieves high power conversion efficiency (PCE) of 18.6 %, which is significantly higher than those of the control devices of PCBM (16.6 %) and PDI (13.8 %). The high PCE of the PDI‐C₆₀‐based device can be attributed to the more matching energy level with the perovskite, more efficient charge extraction, transport, and reduced recombination rate. To the best of our knowledge, the PCE of 18.6 % is the highest value in the PSCs using PDI derivatives as ETLs. Moreover, the device with PDI‐C₆₀ as ETL exhibits better device stability due to the stronger hydrophobic properties of PDI‐C₆₀. The strategy using the PDI/fullerene hybrid provides insights for future molecular design of the efficient ETM for the inverted PSCs.     

Synthesis and characterization of donor–bridge–acceptor alternating copolymers containing perylene diimide units and their application to photovoltaic cells

We have used Suzuki coupling to prepare a series of alternating copolymers featuring coplanar cyclopentadithiophene and hole‐transporting carbazole units. We observed quenching in the photoluminescence spectra of our polymers after incorporating pendent electron‐deficient perylene diimide ( PDI ) moieties on the side chains, indicating more efficient photoinduced electron transfer. Electrochemical measurements revealed that the PDI ‐containing copolymers displayed reasonable and sufficient offsets of the energy levels of their lowest unoccupied molecular orbitals for efficient charge dissociation. The performance of bulk heterojunction photovoltaic cells incorporating the copolymer/[6,6]‐phenyl‐C₆₁‐butyric acid methyl ester blends (1:4, w/w) was optimized when the active layer had a thickness of 70 nm. The photocurrents of the devices were enhanced as a result of the presence of the PDI moieties, thereby leading to improved power conversion efficiencies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1298–1309, 2010     

Combining Fullerenes and Zwitterions in Non‐Conjugated Polymer Interlayers to Raise Solar Cell Efficiency

Polymer zwitterions were synthesized by nucleophilic ring‐opening of 3,3′‐(but‐2‐ene‐1,4‐diyl)bis(1,2‐oxathiolane 2,2‐dioxide) (a bis‐sultone) with functional perylene diimide (PDI) or fullerene monomers. Integration of these polymers into solar cell devices as cathode interlayers boosted efficiencies of fullerene‐based organic photovoltaics (OPVs) from 2.75 % to 10.74 %, and of non‐fullerene‐based OPVs from 4.25 % to 10.10 %, demonstrating the versatility of these interlayer materials in OPVs. The fullerene‐containing polymer zwitterion ( C₆₀‐PZ ) showed a higher interfacial dipole (Δ) value and electron mobility than its PDI counterpart ( PDI‐PZ ), affording solar cells with high efficiency. The power of PDI‐PZ and C₆₀‐PZ to improve electron injection and extraction processes when positioned between metal electrodes and organic semiconductors highlights their promise to overcome energy barriers at the hard‐soft materials interface of organic electronics.     

Electron Delocalization in Perylene Diimide Helicenes

We report two new helicenes derived from the double fusion of an acene with two perylene diimide (PDI) subunits. These PDI‐helicene homologs exhibit very different structural and electronic properties, despite differing by only a single ring in the link between the PDI units. The shorter inter‐PDI link brings the two PDI subunits closer together, and this results in the collision of their respective π‐electron clouds. This collision facilitates intramolecular through‐space electronic delocalization when the PDI‐helicene is reduced.     

A Novel Fluorescent Probe Based on Perylene Derivative for Hg2+ Ions and Biological Thiols and its Application in Live Cell Imaging and Theoretical Calculations

The selective and sensitive detection of biothiols; cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) in aqueous solutions is of considerable importance because of their pivotal roles in maintaining the reducing environment in the cells. This study describes a strategy for the determination of biothiols based on the PDI/Met‐Hg²⁺complex platform. We designed and fabricated methionine modified perylene diimide molecule as a selective sensing probe for Hg²⁺ ions in aqueous solutions ( PDI/Met‐Hg ²⁺). The complex between perylene bisimide derivative ( PDI/Met) and Hg²⁺ was investigated and it demonstrated turn‐on fluorescence response for the detection of the biological thiols. Besides, PDI/Met displayed fluorescence quenching response in the presence of mercury ions and the emission intensity of PDI/Met‐Hg²⁺ was recovered after transferring biothiols (Cys, Hcy, and GSH). Thus, PDI/Met could be utilized as a fluorescent chemosensor for the sequential recognition of mercury ions and biological thiols.     

A Solution‐Processed Air‐Stable Perylene Diimide Derivative for N‐type Organic Thin Film Transistors

For future all‐soluble organic thin film transistor (OTFT) applications, a new soluble n‐type air‐stable perylene diimide derivative semiconductor material with (trifluoromethyl)benzyl groups (TC–PDI–F) is synthesized. The film is formed by spin‐coating in air and optimized for OTFT fabrications. The transistor characteristics and air‐stability of the TC–PDI–F OTFTs is measured to investigate the feasibility of using solution‐processed TC–PDI–F for future OTFT applications. For all‐solution OTFT process applications, the transistor characteristics are demonstrated by using TC–PDI–F as an n‐type semiconductor material and liquid‐phase‐deposited SiO₂ (LPD–SiO₂) as a gate dielectric material. All processes (except material synthesis and electrode deposition) and electrical measurements are conducted in air.     

Energy Transfer at the Single‐Molecule Level: Synthesis of a Donor–Acceptor Dyad from Perylene and Terrylene Diimides

In 2004, we reported single‐pair fluorescence resonance energy transfer (spFRET), based on a perylene diimide (PDI) and terrylene diimide (TDI) dyad ( 1 ) that was bridged by a rigid substituted para‐terphenyl spacer. Since then, several further single‐molecule‐level investigations on this specific compound have been performed. Herein, we focus on the synthesis of this dyad and the different approaches that can be employed. An optimized reaction pathway was chosen, considering the solubilities, reactivities, and accessibilities of the building blocks for each individual reaction whilst still using established synthetic techniques, including imidization, Suzuki coupling, and cyclization reactions. The key differentiating consideration in this approach to the synthesis of dyad 1 is the introduction of functional groups in a nonsymmetrical manner onto either the perylene diimide or the terrylene diimide by using imidization reactions. Combined with well‐defined purification conditions, this modified approach allows dyad 1 to be obtained in reasonable quantities in good yield.     

A Soluble Ladder‐Conjugated Star‐Shaped Oligomer Composed of Four Perylene Diimide Branches and a Fluorene Core: Synthesis and Properties

A new ladder‐conjugated star‐shaped oligomer electron‐transporting material TetraPDI‐PF , with four perylene diimide (PDI) branches and a fluorene core, was efficiently synthesized. The oligomer is highly soluble in dichlorobenzene with a solubility of 155 mg mL^?1, which is higher than those of PDI (35 mg mL^?1) and PDI‐Phen (70 mg mL^?1). Demonstrated by thermogravimetric analysis (TGA), the oligomer exhibits excellent thermal stability with the decomposition temperature (T_d) of 291.2 °C, which is 65 °C higher than that of PDI. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed to investigate the electrochemical properties. Although the CV curves of TetraPDI‐PF are successively scanned for 15 cycles, they still remain invariable reduction potentials. The oligomer also shows outstanding photostability, even better than PDI, which maintains 99 % fluorescence intensity after irradiation for 10 min using maximum laser intensity. In the steady‐state space‐charge‐limited current (SCLC) devices, TetraPDI‐PF exhibits higher intrinsic electron mobility of 2.22×10^?5 cm² V^?1 s^?1, three orders of magnitude over that of PDI (3.52×10^?8 cm² V^?1 s^?1). The bulk heterojunction (BHJ) organic solar cells (OSCs) using TetraPDI‐PF as non‐fullerene acceptors and P3HT as donors give optimum power conversion efficiency (PCE) of 0.64 %, which is 64 times that of the PDI:P3HT BHJ cells.     

Circularly Polarized Luminescence of Chiral Perylene Diimide Based Enantiomers Triggered by Supramolecular Self‐Assembly

Two perylene diimide (PDI) enantiomers ( d/l ‐PDI ) incorporating the d /l ‐alanine moiety have been designed and synthesized. d/l ‐PDI in chloroform displays bright‐yellow fluorescence that is redshifted to orange‐red when the solvent contains a methanol fraction of 99 vol %. No circular dichroism (CD) or circularly polarized luminescence (CPL) signals were observed for d/l ‐PDI enantiomers in CHCl₃. Interestingly, the d/l ‐PDI enantiomers exhibit clear mirror‐image Cotton effects and CPL emission in the aggregate state. The optical anisotropy factor (g_lum) is as high as 0.02 at f_m=99 %, which can be attributed to self‐assembly through intermolecular π–π interactions in the aggregate state.     

Unprecedented Charge‐Transfer Complex of Fused Diporphyrin as Near‐Infrared Absorption‐Induced High‐Aspect‐Ratio Nanorods

Charge‐transfer (CT) complexes of near‐infrared absorbing systems have been unknown until now. Consequently, structural similarities between donor and acceptor are rather important to achieve this phenomenon. Herein, we report electron donors such as non‐fused diporphyrin‐anthracene (DP), zinc diporphyrin‐anthracene (ZnDP) and fused zinc diporphyrin‐anthracene (FZnDP) in which FZnDP absorbs in NIR region and permits a CT complex with the electron acceptor, perylene diimide (PDI ) in CHCl₃ exclusively. UV/Vis‐NIR absorption, ¹H NMR, NOESY and powder X‐ray diffraction analysis demonstrated that the CT complex formation occurs by π–π stacking between perylene units in FZnDP and PDI upon mixing together in a 1:1 molar concentration in CHCl₃, unlike non‐fused ZnDP and DP. TEM and AFM images revealed that the CT complex initially forms nanospheres leading to nanorods by diffusion of CH₃OH vapors into the CHCl₃ solution of FZnDP/PDI (1:1 molar ratio). Therefore, these CT nanorods could lead to significant advances in optical, biological and ferroelectric applications.     

Hydrophobicity Control in Adaptive Crystalline Assemblies

An amphiphile based on polyethylene glycol (PEG) polymer and two molecular moieties (perylene diimide and C₇ fluoroalkyl, PDI and C₇F) attached to its termini assembles into crystalline films with long‐range order. The films reversibly switch from crystalline to amorphous above the PEG melting temperature. The adaptive behavior stems from the responsiveness of the PEG domain and the robustness of the PDI and C₇F assemblies. The hydrophobicity of the film can be controlled by heating, resulting in switching from highly hydrophobic to superhydrophilic. The long‐range order, reversible crystallinity switching, and the temperature‐controlled wettability demonstrate the potential of block copolymer analogues based on simple polymeric/molecular hybrids.     

Perylene and naphthalene diimide copolymers for all-polymer solar cells: Effect of perylene/naphthalene ratio

We report the synthesis of a series of copolymers, having 2,2′-bithiophene as electron-donating moiety, and perylene diimide (PDI) and/or naphthalene diimide (NDI) as electron-accepting moiety, and employed as non-fullerene acceptors in polymer solar cells (PSCs). All the copolymers show wide absorption varying from 300 to 850 nm in the visible and NIR spectrum. When changing the PDI/NDI ratio in the polymer backbone, The LUMO energy levels vary in the range of −3.90 to −3.80 eV and the HOMO energy levels vary in the range of −6.10 to −5.85 eV. Among PSCs based on PTB7-Th donor and these polymer acceptors, the devices based on PTB7-Th/NDI100 yield the best power conversion efficiency (PCE) of 4.67%, while the PTB7-Th/PDI100-based devices yield a PCE of 1.03%. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 682–689     

Time‐Dependent Aggregation‐Induced Enhanced Emission,Absorption Spectral Broadening,and Aggregation Morphology of a Novel Perylene Derivative with a Large D–π–A Structure

Strong aggregation‐caused quenching of perylene diimides (PDI) is changed successfully by simple chemical modification with two quinoline moieties through C?C at the bay positions to obtain aggregation‐induced enhanced emission (AIEE) of a perylene derivative ( Cya‐PDI ) with a large π‐conjugation system. Cya‐PDI is weakly luminescent in the well‐dispersed CH₃CN or THF solutions and exhibits an evident time‐dependent AIEE and absorption spectra broadening in the aggregated state. In addition, morphological inspection demonstrates that the morphology of the aggregated form of Cya‐PDI molecules changed from plate‐shaped to rod‐like aggregates under the co‐effects of time and water. An edge‐to‐face arrangement of aggregation was proposed and discussed. The fact that the Cya‐PDI aggregates show a broad absorption covering the whole visible‐light range and strong intermolecular interaction through π–π stacking in the solid state makes them promising materials for optoelectric applications.     

A new donor–acceptor double‐cable carbazole polymer with perylene bisimide pendant group: Synthesis,electrochemical, and photovoltaic properties

We report here electrochemical synthesis of novel soluble donor–acceptor (D–A) polymer with suitably functionalized perylenetetracarboxylic diimide dye derivative covalently linked to carbazole moiety (Cbz‐PDI). The band gap, E_g was measured using UV–Vis spectroscopy and compared with that obtained by cyclic voltammetry (CV). Efficient intramolecular electron transfer from carbazole‐donor to perynediimide‐acceptor leads to remarkable fluorescence quenching of the perylene core. Furthermore, spectroelectrochemical property and surface morphology of the polymer film were investigated. Characteristic monoanion and dianion radical bands on the UV–Vis absorption spectra attributed to the electrochemical reduction of the neutral polymer were observed. During the reduction process, red color of the film turned into blue and violet, respectively. Finally, the photovoltaic performance of the D–A double‐cable polymer was checked and nearly 0.1% electrical conversion efficiency is obtained under simulated AM 1.5 solar light with 100 mW/cm² radiation power. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6280–6291, 2009     

A Highly Selective and Turn‐on Fluorescent Probe for Fe3+ Ion Based on Perylene Tetracarboxylic Diimide

We have demonstrated a turn‐on fluorescent sensor 6 for detection of Fe³⁺ based on photo‐induced electron transfer (PET) mechanism. The probe comprises a perylene tetracarboxylic diimide (PDI) fluorophore and two bis((1,2,3‐triazol‐4‐yl)methyl)amine (DTA) moieties as the metal ion receptors. It exhibits high selectivity toward Fe³⁺ over various other metal ions in CH₃CN/H₂O (1:1, V/V). The binding stoichiometry for 6 ‐Fe³⁺ complexes has been determined to be 1:2 by a Job plot of fluorescence. The association constant between 6 and Fe³⁺ was estimated to be 1.04×10¹⁰ (mol/L)^?2 by Benesi‐Hildebrand equation.     

Surface‐Bound Cucurbit[8]uril Catenanes on Magnetic Nanoparticles Exhibiting Molecular Recognition

We demonstrate the preparation of surface‐bound cucurbit[8]uril (CB[8]) catenanes on silica nanoparticles (NPs), where CB[8] was employed as a tethered supramolecular “handcuff” to selectively capture target guest molecules. In this catenane, CB[8] was threaded onto a methyl viologen (MV²⁺) axle and immobilized onto silica NPs. The formation of CB[8] catenanes on NPs were confirmed by UV/Vis titration experiments and lithographic characterization, demonstrating a high density of CB[8] on the silica NPs surface, 0.56 nm^?2. This CB[8] catenane system exhibits specific molecular recognition towards certain aromatic molecules such as perylene bis(diimide), naphthol and aromatic amino acids, and thus it can act as a nanoscale molecular receptor for target guests. Furthermore, we also demonstrate its use as an efficient and recyclable nano‐platform for peptide separation. By embedding magnetic NPs inside silica NPs, separation could be achieved by simply applying an external magnetic field. Moreover, the peptides captured by the catenanes could be released by reversible single‐electron reduction of MV²⁺. The entire process demonstrated high recoverability.