Library of Azabenz-Annulated Core-Extended Perylene Derivatives with Diverse Substitution Patterns and Tunable Electronic and Optical Properties

Ring Fusion Elevates the Electronic Mobility of Azabenzannulated Perylene Diimide

The backwardness of n-type organic semiconductors still exists compared with the p-type counterparts. Thus, the development of high-performance n-type organic semiconductors is of great importance for organic electronic devices and their integrated circuits. In recent years, azabenzannulated perylene diimide (PDI), as one of immense bay-region-annulated PDI derivatives, has drawn considerable attentions. However, the electronic mobilities of azabenzannulated PDI derivatives are barely satisfactory. In this contribution, the peripheral benzene ring in azabenzannulated PDI 2 was fused to the ortho position by intramolecular C-H arylation cyclization. This endows the resultant azabenzannulated PDI 4 a planar configuration as well as electron deficient pentagonal ring. As a result, the electronic mobility of 4 is almost two orders of magnitude higher than that of the nonfused azabenzannulated PDI 2. This work shall pave a new avenue in elevating the performance of azabenzannulated PDI in organic electronics.

Substitution Effect of a Single Nitrogen Atom on π-Electronic Systems of Linear Polycyclic Aromatic Hydrocarbons (PAHs): Theoretically Visualized Coexistence of Mono- and Polycyclic π-Electron Delocalization

We theoretically investigated the nitrogen substitution effect on the molecular structure and π-electron delocalization in linear nitrogen-substituted polycyclic aromatic hydrocarbons (N-PAHs). Based on the optimized molecular structures and magnetic field-induced parameters of fused bi- and tricyclic linear N-PAHs, we found that the local π-electron delocalization of subcycles (e.g., mono- and bicyclic constituent moieties) in linear N-PAHs is preserved, despite deviation from ideal structures of parent monocycles. The introduction of a fused five-membered ring with a pyrrolic N atom (N-5MR) in linear N-PAHs significantly perturbs the π-electronic condition of the neighboring fused six-membered ring (6MR). Monocyclic pyrrole exhibits substantial bond length alternations, strongly influencing the π-electronic systems of both the fused N-5MR and 6MR in linear N-PAHs, depending on the location of shared covalent bonds. A fused six-membered ring with a graphitic N atom in an indolizine moiety cannot generate monocyclic π-electron delocalization but instead contributes to the formation of polycyclic π-electron delocalization. This is evidenced by bifurcated diatropic ring currents induced by an external magnetic field. In conclusion, the satisfaction of Hückel's 4n + 2 rule for both mono- and polycycles is crucial for understanding the overall π-electron delocalization. It is crucial to consider the unique characteristics of the three types of substituted N atoms and the spatial arrangement of 5MR and 6MR in N-PAHs.

Pictet-Spengler synthesis of twisted quinoline-fused BODIPYs as heavy-atom-free photosensitizers

Singly and doubly quinoline-fused BODIPYs were effectively synthesized through a reaction sequence consisting of the reduction of nitrophenyl-substituted BODIPYs and subsequent Pictet-Spengler cyclization. The combination of the BODIPY core and fused quinoline rings imposed significantly twisted conformations in the quinoline-fused BODIPYs (around 20.0° deviation from coplanarity obtained from X-ray crystal structure analysis). These twisted BODIPYs showed significantly reduced LUMO, redshifted absorption/emission bands, high molar extinction coefficients and satisfactory reactive oxygen species generation efficiency up to 0.56, indicating potential use as heavy-atom-free photosensitizers.

Tetraazacoronenes and Their Dimers, Trimers and Tetramers

Tetraazacoronenes were synthesized from bay-functionalized tetraazaperylenes by Zr-mediated cyclization and four-fold Suzuki-Miyaura cross coupling. In the Zr-mediated approach, an η4 -cyclobutadiene-zirconium(IV) complex was isolated as an intermediate to cyclobutene-annulated derivatives. Using bis(pinacolatoboryl)vinyltrimethylsilane as a C2 building block gave the tetraazacoronene target compound along with the condensed azacoronene dimer as well as higher oligomers. The series of extended azacoronenes show highly resolved UV/Vis absorption bands with increased extinction coefficients for the extended aromatic cores and fluorescence quantum yields of up to 80 % at 659 nm.

Bowl-Shaped Bispyrrole-Fused Perylene-diimide and Its Anions

Incorporating two pyrrole subunits at the bay positions of perylene-diimide has been a long-pursued goal since 2009, but it has not been achieved due to high strain. Herein, via one step Buchwald-Hartwig reaction, PDI-2N was successfully generated with a bowl depth of 1.52 Å. Though with electron-rich pyrrole embedding, PDI-2N's radical anion and dianion were facilely prepared and were investigated both experimentally and theoretically. Moreover, PDI-2N crystallized in different manners under distinct conditions, and it formed tubular crystals with infinite two-directional columnar stacking under DMF conditions. This finding develops a dream bowl-shaped PDI derivative that holds great promise in organoelectronics.

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

This review surveys recent progress in the chemistry of polycyclic heteroaromatic molecules with a focus on structural diversity and synthetic methodology. The article covers literature published during the period of 2016-2020, providing an update to our first review of this topic (Chem. Rev. 2017, 117 (4), 3479-3716).

A novel colorimetric and fluorescent probe based on a core-extended perylene tetra-(alkoxycarbonyl) derivative for the selective sensing of fluoride ions

A novel fluoride (F⁻) colorimetric and fluorescent probe (P1) based on a core-extended perylene tetra-(alkoxycarbonyl) (PTAC) derivative was developed. The probe exhibited high sensitivity and selectivity for distinguishing F⁻ from other common anions through significant changes of the UV-Vis and fluorescence spectra. Job's plot analysis revealed that the stoichiometry of the P1–F⁻ interaction is 1 : 1. The association constant between P1 and F⁻ was estimated to be 9.7 × 10² M⁻¹ and the detection limit of F⁻ was about 0.97 μM. An approximately 76 nm red-shift in the absorption and fluorescent quenching response was observed when F⁻ was associated with P1. The emission intensity (I₅₇₄) decreased linearly along with the F⁻ concentration from 3 × 10⁻⁵ M to 2 × 10⁻⁴ M. The mechanism of intermolecular proton transfer (IPT) was deduced based on the changes in the absorption, fluorescence, electrochemistry, and ¹H NMR titration spectra. The density functional theory (DFT) theoretical results of the P1–F⁻ complex are in good agreement with the experimental results. The rapid detection of F⁻ ions in the solid state and living cells was also studied.

A colorimetric and fluorescent probe based on a nuclear extended perylene tetra-(alkoxycarbonyl) derivative can be used for the detection of F⁻ in liquid, solid and living cells.

Facile Azabenz-Annulations through UV-induced Photocyclization: A Promising Method for Perylenediimide-Based Organic Semiconductors

The derivatization of perylenediimides (PDIs) by bay decoration is essential for the development of PDI-based semiconductors owing to their excellent photoelectric properties. Herein, four bis-azabenz-annulated PDIs (bis-AzaBPDIs) are concisely synthesized in high yields through ultraviolet-induced photocyclization, where the reaction processes including aldimine condensation, cyclization, and oxidative re-aromatization are investigated. The optical characterizations and theoretical simulation reveal that the unique properties of the four bis-AzaBPDIs are comparable to their parent PDI. Organic field effect transistors with compounds 2, 3, or 4 as active layers indicated that all compounds showed unipolar electron transport properties with the mobilities of 1.1×10^-3 , 5.8×10^-4 , and 8.5×10^-6  cm²  V^-1  s^-1 , respectively. These results suggest the great potential of bis-AzaBPDIs as organic semiconductors. The easy preparation approach reported in this work would renew research interest in developing bis-AzaBPDI-based optoelectronic molecules.

Diels-Alder Cycloaddition to the Bay Region of Perylene and Its Derivatives as an Attractive Strategy for PAH Core Expansion: Theoretical and Practical Aspects

PAHs (polycyclic aromatics hydrocarbons), the compound group that contains perylene and its derivatives, including functionalized ones, have attracted a great deal of interest in many fields of science and modern technology. This review presents all of the research devoted to modifications of PAHs that are realized via the Diels–Alder (DA) cycloaddition of various dienophiles to the bay regions of PAHs, leading to the π-extension of the starting molecule. This type of annulative π-extension (APEX) strategy has emerged as a powerful and efficient synthetic method for the construction of polycyclic aromatic hydrocarbons and their functionalized derivatives, nanographenes, and π-extended fused heteroarenes. Then, [4 + 2] cycloadditions of ethylenic dienophiles, -N=N-, i.e., diazo-dienophiles and acetylenic dienophiles, are presented. This subject is discussed from the organic synthesis point of view but supported by theoretical calculations. The possible applications of DA cycloaddition to PAH bay regions in various science and technology areas, and the prospects for the development of this synthetic method, are also discussed.

Visible-Light-Mediated Synthesis of AzaBenzannulated Perylenediimide-Based Light-Harvesting Dyads

Intramolecular imine photocyclization has been explored for grafting on the bay region of perylenediimide (PDI) different electro- and photoactive chromophores to achieve new AzaBenzannulated-PDI (AzaBPDI) dyads. Triphenylamine (TPA), fluorene (Fl), perylenemonoimide (PMI), and perylenediimide (PDI) units have been successfully assembled to AzaBPDI using this straightforward one-pot synthesis starting from the easily accessible 1-aminoPDI. This original procedure was compared to the well-known Pictet-Spengler reaction and appears to be an attractive alternative in terms of versatility and efficiency with higher yields obtained. The optical and electrochemical properties of these molecular systems demonstrated large absorption capabilities in the visible range, good accepting abilities with low LUMO levels, and efficient electronic interactions between chromophoric units such as energy or electron transfers. In addition, with their large dihedral angle estimated by theoretical calculations, those dyads should present interesting applications in various organic optoelectronic devices. In particular, the PMI-AzaBPDI and PDI-AzaBPDI dyads presenting low LUMO levels, a broad absorption in the visible range, and a twisted conformation make them good candidates as non-fullerene acceptors in organic solar cells.

Nitro-Perylenediimide: An Emerging Building Block for the Synthesis of Functional Organic Materials

Perylenediimide (PDI) is one of the most important classes of dyes and is intensively explored in the field of functional organic materials. The functionalization of this electron-deficient aromatic core is well-known to tune the outstanding optoelectronic properties of PDI derivatives. In this respect, the functionalization has been mostly addressed in bay-positions to halogenated derivatives through nucleophilic substitutions or metal-catalyzed coupling reactions. Being aware of the synthetic difficulties of obtaining the key intermediate 1-bromoPDI, we will present as an alternative in this review the potential of 1-nitroPDI: a powerful building block to access a large variety of PDI-based materials.

Catalyst-Free One-Pot Synthesis of Unsymmetrical Five- and Six-Membered Sulfur-Annulated Heterocyclic Perylene Diimides for Electron-Transporting Property

A novel unsymmetrical five- and six-membered sulfur-annulated heterocyclic perylene diimides (PDI) derivative was obtained by a one-pot and catalyst-free synthesis in a high yield. The unsymmetrical PDI exhibits a noteworthy bathochromic shift absorption of up to 700 nm and a low-lying lowest unoccupied molecular orbital level of -3.99 eV. The compound owns a complete planar structure and a high electron mobility of 4.8 × 10^-3 cm² V^-1 s^-1 in solution-processable top-gate/bottom-contact organic field-effect transistor device.

Progress in the synthesis of perylene bisimide dyes

Rapid progress in the synthesis of perylene bisimide dyes gave an old scaffold new life.

Carbocyclization approaches to electron-deficient nanographenes and their analogues

Versatile π-aromatic building blocks and selective coupling transformations enable rapid assembly of complex electron-deficient molecules, useful as n-type organic semiconductors.

Detection of gaseous amines with a fluorescent film based on a perylene bisimide-functionalized copolymer

A fluorescent copolymer containing PBI units and hydroxyl-ethyl structures was developed for the fast and sensitive detection of gaseous amines