Syntheses and properties of 1,6 and 1,7 perylene diimides and tetracarboxylic dianhydrides

Via Sonogashira cross-coupling with different alkynes, 1,6 and 1,7 perylene diimides (PDIs) and perylene tetracarboxylic dianhydrides (PTCDs) were synthesized from the corresponding regioisomeric mixture of 1,6/1,7-dibromo precursors. Both bulky triphenyl propyne (TPP) groups and nonbulky hexyl groups allow for facile chromatographic separation. The optical properties of these compounds are discussed. Neutral bay substituents hypsochromically shift both the absorption and emission through deformation from planarity of the perylene core.     

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.     

Selective bromination of perylene diimides under mild conditions

A novel method for the bromination of perylene diimides, PDI (1), under mild conditions is reported. Variation of the reaction conditions allows mono- and dibromination of PDIs to afford 2 and 3 (these can be separated through standard procedures) or exclusive dibromination to afford 3. Pure 1,7 regioisomers are obtained through repetitive crystallization. The structure of 1,7-3b was elucidated by a single-crystal X-ray analysis. The facility of the bromination reaction, which decreases in the order 1a > 1b > 1c, depends on PDI aggregation propensities. Monobrominated PDIs were utilized for the syntheses of novel unsymmetrical piperidinyl (4a and 4b) and trimethylsilylethynyl derivatives (5a and 5b). Computational studies (DFT) on imide substituent rotation in PDIs reveal that in the case of bulky groups there is a restricted rotation leading to isomers, in agreement with our experimental results. An aromatic core twist in PDIs bearing one and two bromine substituents was also investigated by DFT.     

Cyclophanes of perylene tetracarboxylic diimide with different substituents at bay positions

Cyclophanes of perylene tetracarboxylic diimides (PDIs) with different substituents at the bay positions, namely four phenoxy groups at the 1,7-positions (1), four piperidinyl groups at the 1,7-positions (2), and eight phenoxy groups at the 1,6,7,12-positions (3) of the two PDI rings, have been synthesized by the condensation of perylene dianhydride with amine in a dilute solution. These novel cyclophanes were characterized by (1)H NMR spectroscopy, MALDI-TOF mass spectrometry, electronic absorption spectroscopy, and elemental analysis. The conformational isomers of cyclophanes substituted with four piperidinyl groups at the 1,7-positions (2 a and 2 b) were successfully separated by preparative TLC. The main absorption band of the cyclophanes shifts significantly to the higher energy side in comparison with their monomeric counterparts, which indicates significant pi-pi interaction between the PDI units in the cyclophanes. Nevertheless, both the electronic absorption and fluorescence spectra of the cyclophanes were found to change along with the number and nature of the side groups at the bay positions of the PDI ring. Time-dependent DFT calculations on the conformational isomers 2 a and 2 b reproduce well their experimental electronic absorption spectra. Electrochemical studies reveal that the first oxidation and reduction potentials of the PDI ring in the cyclophanes increase significantly compared with those of the corresponding monomeric counterparts, in line with the change in the energy of the HOMO and LUMO according to the theoretical calculations.     

Photophysical and electrochemical properties of 1,7-diaryl-substituted perylene diimides

Substituent effects on the photophysical and electrochemical properties of 1,7-diaryl-substituted perylene diimides (1,7-Ar(2)PDIs) have been carefully explored. Progressive red-shifts of the absorption and emission maxima were observed when the electron-donating ability of these substituents was increased. Linear Hammett correlations of 1/lambda(max) versus sigma(+) were observed in both spectral analyses. The positive slopes of the Hammett plots suggested that the electronic transitions carry certain amounts of photoinduced intramolecular charge-transfer (PICT) character from the aryl substituents to the perylene diimide core which leads to the reduction of the electron density on the substituents. The substituent electronic effects originated mainly from the perturbation of the core PDI HOMO energy level by the substituents. This conclusion was supported by PM3 analyses and confirmed by cyclic voltammetry experiments. More interestingly, the Ph(2)NC(6)H(4)-substituted PDI, 4i, showed an unusual dual-band absorption that spans from 450 to 750 nm. We tentatively assigned these two bands as the charge-transfer band and the PDI core absorption, respectively.     

Palladium complexes of perylene diimides: strong fluorescence despite direct attachment of late transition metals to organic dyes

We prepared the first sigma-bonded metal complexes of widely utilized organic dyes, perylene tetracarboxylic acid diimides (PDIs). These 1,7-dipalladium PDI complexes were synthesized by C-Br oxidative addition of 1,7-dibromo-N,N'-dicyclohexyl PDI (Br2PDI) to Pd(0) phosphine complexes bearing triphenylphosphine and bischelating 1,2-bis(diphenylphosphino)ethane (dppe). The structures of Pd-PDI complexes were elucidated by single-crystal X-ray analysis. Surprisingly, despite direct attachement of two late transition metal centers, Pd-PDI systems are highly fluorescent (Phi=0.65 and 0.22 for triphenylphosphine and dppe systems, respectively). This is rationalized in terms of weak electronic interactions between the metal centers and PDI pi-system, as revealed by TD-DFT calculations.     

1,6‐ and 1,7‐Regioisomers of Dicyano‐Substituted Perylene Bisimides: Synthesis,Optical and Electrochemical Properties

In this study, 1,6‐ ad 1,7‐regioisomers of dicyano‐substituted perylene bisimides (1,6‐ C and 1,7‐ C ) were synthesized and successfully isolated from their regioisomeric mixture using conventional methods of separation, and subsequently characterized by 400 MHz ¹H NMR spectroscopy. This is the first time that the 1,6‐dicyanoperylene bisimide 1,6‐ C has been obtained in pure form. Moreover, the optical and electrochemical properties of 1,6‐ C and 1,7‐ C were found to be virtually the same. Time‐dependent density functional theory calculations performed on both dyes are reported in order to rationalize their electronic structures and optical properties.     

1,6- and 1,7-regioisomers of dinitro- and diamino-substituted perylene bisimides: synthesis,photophysical and electrochemical properties

1,6- and 1,7-regioisomers of dinitro- (1,6-3 and 1,7-3) and diamino-substituted perylene bisimides (1,6-1 and 1,7-1) were synthesized. The regioisomers 1,6-3 and 1,7-3 were successfully separated by high performance liquid chromatography and characterized by 500 MHz ¹H NMR spectroscopy. Subsequently, the reduction of 1,6-3 and 1,7-3 afforded the corresponding diaminoperylene bisimides 1,6-1 and 1,7-1, respectively. This is the first time 1,6-regioisomers of dinitro- and diamino-substituted perylene bisimides are obtained in pure form. The photophysical and electrochemical properties of 1,6-3 and 1,7-3 were found to be almost the same. However, the regioisomers 1,6-1 and 1,7-1 exhibit significant differences in their optical characteristics. The absorption spectrum of 1,6-1 covers a larger part of the visible region compared to that of 1,7-1. Upon excitation, 1,6-1 also show larger dipole moment change than that of 1,7-1. Time-dependent density functional theory calculations are reported on these dyes in order to rationalize their electronic structure and absorption spectra.     

Theoretical study of one-photon and two-photon absorption properties of perylene tetracarboxylic derivatives

The geometrical structure, electronic structure, one-photon absorption (OPA) and two-photon absorption (TPA) properties of the perylene tetracarboxylic derivatives (PTCDs) were studied theoretically by using density functional theory (DFT) and Zerner's intermediate neglect of differential overlap (ZINDO) methods. The results revealed that increasing the number of naphthalene nucleus, extending the conjugated length on long axis, increasing the strength of donor group on lateral side, decreasing the DeltaE(H-L) (energy gap between the highest occupied orbital and the lowest unoccupied orbital) and keeping the conjugation effect and inductive effect along the same molecular axis are the efficient ways to enlarge TPA cross section of PTCDs compounds. The results that PTCDs compounds exhibited extremely large TPA cross section of around 800-1100 nm (near infrared region) shed light into the significance of the PTCDs compounds for applications in TPA labeling materials in vivo.     

Perylene-3,4,9,10-tetracarboxylic acid diimides: synthesis, physical properties, and use in organic electronics

Perylene-3,4,9,10-tetracarboxylic acid diimides (perylene diimides, PDIs) have been used as industrial pigments for many years. More recently, new applications for PDI derivatives have emerged in areas including organic photovoltaic devices and field-effect transistors. This Perspective discusses the synthesis and physical properties of PDI derivatives and their applications in organic electronics.     

Desymmetrization of Perylenediimide Bay Regions Using Selective Suzuki–Miyaura Reactions from Dinitro Substituted Derivatives

Bay decoration of perylenediimide (PDI) is an attractive approach for tuning the optoelectronic properties of the dye as well as breaking backbone planarity, which provides the possibility of preventing the undesired formation of aggregates. This is usually performed through successive bis-bromination of PDI and pallado-catalyzed cross-coupling, which leads to symmetric triads. We now describe an efficient synthetic strategy for desymmetrization of the accepting PDI core by starting from its bis-nitration. To this end, Suzuki–Miyaura Couplings (SMC) were carried out on a mixture of 1,6- and 1,7-dinitroPDI regioisomers to add triphenylamine donating moieties and obtain donor–acceptor–donor triads. Investigation of the reactivity of dinitro PDI derivatives toward SMC has allowed us to access unprecedented asymmetric π-conjugated PDI-centered triads. These 1,6- and 1,7-PDI based triads, prepared as regioisomeric mixtures, were successfully separated and their spectroscopic, crystallographic and optoelectronic differences are reported.     

The Photostability of Two Optical Materials Based on Perylene Diimide Substituted by Different Aromatic Groups at the Bay Area

The perylene diimide substituented by thiophene rings at bay area shows photoactivity and can be used as a photo sensor, but another one substituented by mestylene groups is photostable. The single crystal of 1,7‐mesitylene perylene diimide was obtained. X‐ray diffraction data of the crystal revealed that the plane of the perylene core was hardly twisted by introduction of mesitylene groups. These mestylene groups are like clips maintaining the planarity of the perylene core. Density functional theory calculation was applied to study the difference of photophysical and photochemical properties. The discovery is valuable for design guidance of perylene diimides.     

Bis-morpholine-substituted perylene bisimides: impact of isomeric arrangement on electrochemical and spectroelectrochemical properties

The synthesis and separation of the 1,6- and 1,7- isomers of N,N'-bis(n-butyl)dimorpholino-3,4:9,10-perylenetetracarboxylic acid bisimide are reported. Investigations of the electrochemical and spectroscopic, in particular, spectroelectrochemical, properties of the two isomers reveal a sequence of electrochemically and chemically reversible redox processes for both isomers. Importantly, the 1,7-isomer of N,N'-bis(n-butyl)dimorpholino-3,4:9,10-perylenetetracarboxylic acid bisimide was observed to undergo a two-electron oxidation process, which contrasts with the behavior of both the corresponding 1,6-isomer and other related amino-substituted perylene bis-imide species.     

Preparation and characterization of regioisomerically pure 1,7-disubstituted perylene bisimide dyes

A detailed study on bromination and subsequent imidization of perylene bisanhydride with cyclohexylamine is reported. The present results reveal that previously reported 1,7-difunctionalized perylene bisimides are presumably contaminated with the respective 1,6 regioisomers. N,N'-Dicyclohexyl-1,7-dibromoperylene bisimide 1,7-3 is obtained for the first time in isomerically pure form, and its structure is unequivocally confirmed by X-ray analysis. By using regioisomerically pure 1,7-dibromoperylene bisimide 1,7-3, 1,7-dipyrrolidinylperylene bisimides 4a-c and 1,7-dipyrrolidinylperylene bisanhydride 5 as well as the unsymmetrically difunctionalized 1-bromo-7-pyrrolidinyl- and 1-cyano-7-pyrrolidinylperylene bisimides 7 and 8 are synthesized in good yield.     

Controlled cyclopolymerization of 4,5-disubstituted 1,7-octadiynes and its application to the synthesis of a dendronized polymer using Grubbs catalyst

Cyclopolymerization of 1,7-octadiynes using a ruthenium-based Grubbs catalyst, to produce conjugated polymers containing six-membered rings as repeat units is generally much slower than the corresponding polymerization of 1,6-heptadiynes, and thus it is considered less useful. Here, we demonstrate the regioselective cyclopolymerization of 4,5-disubstituted 1,7-octadiynes with considerably enhanced reactivity. Using a third generation Grubbs catalyst with a rapid initiation step, various conjugated polymers with low polydispersity indices (PDIs) could be synthesized under optimized conditions. Among the various monomers tested, those with bulky substituents underwent controlled polymerization within 1 h at room temperature, which was a significant improvement over previous reports. This led us to a more efficient preparation of fully conjugated block copolymers. Finally, owing to the fast cyclopolymerization, a synthetically challenging dendronized polymer was successfully prepared from a macromonomer containing two second generation dendrons at the 4 and 5 positions of 1,7-octadiyne, and its rod-like conformation was visualized using atomic force microscopy. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 274–279     

Investigation of the two-photon absorption cross-section in perylene tetracarboxylic derivatives: nonlinear spectra and molecular structure

We investigated the 2PA absorption spectrum of a family of perylene tetracarboxylic derivatives (PTCDs): bis(benzimidazo)perylene (AzoPTCD), bis(benzimidazo)thioperylene (Monothio BZP), n-pentylimidobenzimidazoperylene (PazoPTCD), and bis(n-butylimido)perylene (BuPTCD). These compounds present extremely high two-photon absorption, which makes them attractive for applications in photonics devices. The two-photon absorption cross-section spectra of perylene derivatives obtained via Z-scan technique were fitted by means of a sum-over-states (SOS) model, which described with accuracy the different regions of the 2PA cross-section spectra. Frontier molecular orbital calculations show that all molecules present similar features, indicating that nonlinear optical properties in PTCDs are mainly determined by the central portion of the molecule, with minimal effect from the lateral side groups. In general, our results pointed out that the differences in the 2PA cross-sections among the compounds are mainly due to the nonlinearity resonance enhancement.     

有机太阳能电池中基于苝二酰亚胺结构小分子受体进展

最近几年,有机太阳能电池中的非富勒烯小分子受体研究引起了人们的兴趣。其中,苝二酰亚胺(PDI)类分子因具有良好的电子传输能力,较强的电子亲和力,稳定的光、热、化学性能以及化学结构的可设计性带来的性能可调控性而得到广泛的关注。本文总结了近三年来在体异质结有机太阳能电池应用方面PDI小分子受体的研究进展,重点关注了PDI分子结构对其性能的影响,希望为以后PDI类受体分子的设计思路起到一定的启发作用。     

Facile synthesis of 1-bromo-7-alkoxyl perylene diimide dyes: toward unsymmetrical functionalizations at the 1,7-positions

In this Letter, we report a facile approach to synthesize unsymmetrical 1-bromo-7-alkoxyl perylene diimides by the nucleophilic substitution of one of the two 1,7-dibromo units with an alkyl alcohol using K₂CO₃ as the base. A further replacement of another bromo, for example, by using 4-hydroxylpyridine resulted in unsymmetrical functionalizations at the 1,7-positions. The optical properties of the unsymmetrical PDI derivative were reported and compared with those of the symmetrical derivative.     

Self‐Assembled 1D‐Nanowire Lasers of Perylenediimides

The 1D nanostructures of perylenediimides (PDIs) have been readily obtained owing to strong cofacial π–π stacking interactions, which, however, subsequently render PDIs weakly emissive in the solid state. Therefore, organic solid‐state lasers based on 1D nanostructures of PDIs have not been achieved yet. Herein, we prepared 1D‐nanowires of N,N’‐bis(1‐ethylpropyl)‐2,5,8,11‐tetrakis(o‐methylphenyl)‐perylene‐3,4:9,10‐tetracarboxylic acid diimide (mp‐PDI), which stack into a loosely J‐type arrangement. J‐aggregation leads to a solid‐state photoluminescence (PL) efficiency φ>18 % and the nanowires of mp‐PDI exhibit excellent Fabry–Perot (FP) mode laser action.     

Facile synthesis of chiral unsymmetric perylene tetracarboxylic diimides involving α-amino acids

A facile synthesis of chiral unsymmetric perylene tetracarboxylic diimides (PDIs) has been developed and the first two nonracemic chiral amphiphilic PDIs have been synthesized. The key building blocks, AB bifunctional 3,4,9,10-perylenetetracarboxylic-3,4-anhydride-9,10-imides, were prepared conveniently from enantiomerically pure α-amino acids, which were introduced as the steric and stereochemical controlling units. Such building blocks allow the incorporation of sterically and stereochemically controlled PDI moieties into both terminal and inner positions.