Molecular assemblies of perylene bisimide dyes in water

Perylene bisimides are among the most valuable functional dyes and have numerous potential applications. As a result of their chemical robustness, photostability, and outstanding optical and electronic properties, these dyes have been applied as pigments, fluorescence sensors, and n‐semiconductors in organic electronics and photovoltaics. Moreover, the extended quadrupolar π system of this class of dyes has facilitated the construction of numerous supramolecular architectures with fascinating photophysical properties. However, the supramolecular approach to the formation of perylene bisimide aggregates has been restricted mostly to organic media. Pleasingly, considerable progress has been made in the last few years in developing water‐soluble perylene bisimides and their application in aqueous media. This Review provides an up‐to‐date overview on the self‐assembly of perylene bisimides through π–π interactions in aqueous media. Synthetic strategies for the preparation of water‐soluble perylene bisimides and the influence of water on the π–π stacking of perylene bisimides as well as the resulting applications are discussed.     

On/off switching of perylene tetracarboxylic bisimide luminescence by means of substitution at the N-position by electron-rich mono-, di-, and trimethoxybenzenes

A series of perylene tetracarboxylic bisimides, substituted at the N-position with methoxyphenyl groups, have been synthesized together with model compounds and their photophysical properties have been investigated by means of steady-state and time-resolved spectroscopic techniques. The luminescence properties of the examined compounds vary remarkably with the substitution pattern, with emission quantum yields ranging from 1 to 10(-2)-10(-3). The observed quenching of the luminescence is assigned to a photoinduced electron transfer (PET) from the electron-rich methoxybenzene unit to the perylene bisimide moiety. The radical anion of perylene bisimide has been detected by transient-absorption spectroscopy. The results could satisfactorily be explained by taking into consideration the redox potentials of the partners and the electron-releasing ability of each methoxy group in relation to its position with respect to N. Quantum-chemical calculations were also performed.     

Hydrogen-bonded oligo(p-phenylenevinylene) functionalized with perylene bisimide: self-assembly and energy transfer

We describe the synthesis, supramolecular ordering on surfaces and in solution, and photophysical characterization of OPV4UT-PERY, an oligo(p-phenylenevinylene) (OPV) with a covalently attached perylene bisimide moiety. In chloroform, the molecule forms dimers through quadruple hydrogen bonding of the ureido-s-triazine array. This is supported by scanning tunneling microscopy (STM) studies, which reveal dimer formation at the liquid (1,2,4-trichlorobenzene)/solid (graphite) interface. Moreover, contrast reversal in bias-dependent STM imaging provides information on the ordering and different electronic properties of the oligo(p-phenylenevinylene) and perylene bisimide moieties. In dodecane, the molecule self-assembles into H-type aggregates that are still soluble as a result of the hydrophobic shell formed by the dodecyloxy wedges. The donor-acceptor molecule is characterized by efficient energy transfer from the photoexcited OPV to the perylene bisimide. Mixed assemblies with analogous OPVs lacking the perylene bisimide unit have been prepared in dodecane solution and energy transfer to the incorporated perylene bisimides has been studied by fluorescence spectroscopy.     

Effect of the Ortho Alkylation of Perylene Bisimides on the Alignment and Self-Assembly Properties

The effect of the ortho alkylation of perylene bisimides on the alignment and self-assembly properties has been studied. It was found that the dichroic properties of perylene bisimides in a liquid crystal host can be reversed with a single synthetic step by ortho alkylation. Furthermore, a solvent-induced growth of ultralong organic n-type semiconducting fibrils from non-ortho-alkylated perylene bisimide was observed. Ortho substitution of the perylene bisimide core alters the mode of fibrillar growth, leading to isotropic crystallization.     

Suzuki coupling reaction of 1,6,7,12-tetrabromoperylene bisimide

[STRUCTURE: SEE TEXT] 1,6,7,12-Tetrabromoperylene-3,4,9,10-tetracarboxylic acid bisanhydride and the corresponding tetrabrominated perylene bisimide were first synthesized with high yields. The Suzuki coupling reaction of novel tetrabromoperylene bisimide with phenylbonoric acid was studied. The four bromines in the bay position of the perylene core were substituted successfully to yield 1,6,7,12-teraphenylperylene bisimide. The photochemical properties of the novel perylene bisimides were studied and presented.     

Synthesis and Optical Properties of Water‐Soluble Polyglycerol‐Dendronized Rylene Bisimide Dyes

Four new water‐soluble polyglycerol‐dendronized perylene, terrylene, and quaterrylene bisimides have been synthesized and characterized with respect to their optical properties in polar organic solvents and water by using UV/Vis and fluorescence spectroscopy. All of these dyes were highly soluble in water, but the size of the chosen polyglycerol dendron was only sufficient to completely suppress dye aggregation for the core‐unsubstituted perylene derivative. Their high solubility in water and their absorption and emission wavelengths up to the NIR region make the core‐unsubstituted perylene and terrylene bisimides ideal candidates for applications in bioimaging, whilst the lack of fluorescence for quaterrylene bisimide in all polar solvents does not warrant further investigation of this chromophore in fluorescence and imaging applications. Likewise, tuning of the emission of rylene bisimides towards longer wavelengths by employing electron‐donating bay substituents is not a promising strategy, owing to the lower fluorescence quantum yields in polar solvents and, in particular, in water.     

Synthesis and Predetermined Supramolecular Chirality of Carbohydrate‐Functionalized Perylene Bisimide Derivatives

Eight carbohydrate‐modified perylene bisimides ( PBI‐4 lac‐2 lac , PBI‐4 lac‐2 Man , PBI‐4 lac‐2 Gal , PBI‐4 lac‐2 Mal , PBI‐4 Man‐2 Man , PBI‐4 Man‐2 lac , PBI‐4 Man‐2 Gal and PBI‐4 Man‐2 Mal ) were synthesized, and the following predetermined supramolecular chirality rule was found: perylene bisimides modified with disaccharides (D ‐lactose and D ‐maltose) at the imide position generated right‐handed chirality, and those modified with monosaccharides (D ‐mannose and D ‐galactose) generated left‐handed chirality, when D ‐lactose or D ‐mannose was substituted in the bay positions of perylene bisimides with amide bonds as the linking spacers. These results may be because of the difference in the stacking angle of the perylene bisimide backbones induced by the steric effect and the additional hydrogen bonds between the disaccharide residues. This study provides an important design rule for predetermined chiral self‐assembly of perylene bisimides.     

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.     

1,6-Disubstituted perylene bisimides: concise synthesis and characterization as near-infrared fluorescent dyes

Detailed studies on bromination and subsequent imidization of perylene bisanhydride were reported. 1,6,7,12-Tetrabromoperylene bisimide was obtained in an optimized high yield. In addition, 1,6-disubstituted regioisomer was separated for the first time in isomerically pure form, and the structure was confirmed by ¹H NMR, MS, element analysis, and photophysical measurements. By using a mixture of regioisomers 1,6- and 1,7-dibromo-perylene bisimide, 1,6-dipiperidinylperylene bisimides (1,6-Piper-Pery) were synthesized, purified, and their fluorescence were measured with a peak at 760 nm. These compounds can be used as stable near-infrared absorbing and fluorescent dyes.     

Localization/Delocalization of Charges in Bay‐Linked Perylene Bisimides

The copper‐mediated Ullmann coupling of 1,7‐dibromoperylene bisimides afforded structurally perfect singly‐linked perylene bisimide (PBI) arrays, whilst the homo‐coupling of 1,12‐dibromoperylene bisimides gave doubly‐linked and triply‐linked diperylene bisimides. The interactions of three bay‐linked diperylene bisimides that differed in their linkage (singly, doubly, and triply) were investigated in their neutral and reduced forms (mono‐anion to tetra‐anion). UV/Vis absorption and fluorescence spectroscopy revealed different degrees of interaction, which was explained by exciton coupling and conjugation effects. The electrochemical properties and spectroelectrochemistry also showed quite‐different degrees of PBI interactions in the reduced mixed‐valence species, which was apparent by the observation of CT bands. The interpretation of the experimental findings was supported by spin‐restricted and ‐unrestricted DFT and time‐dependent TD‐DFT calculations with the long‐range‐corrected CAM‐B3LYP functional. Accordingly, the degree of interaction in both the neutral and reduced forms of the bay‐linked PBIs was qualitatively in the order doubly linked<singly linked?triply linked, owing to the different degrees of twisting and flexibility between the two PBIs moieties. Only triply linked diPBI showed completely delocalized wavefunctions over the entire π‐system.     

Synthesis and near-infrared characteristics of novel perylene bisimide dyes bay-functionalized with naphthalimide chromophores

Novel perylene bisimide dyes bay-functionalized with naphthalimide chromophores have been prepared conveniently by coupling of 1,8-naphthalimide and dibromoperylene bisimides. Their optical properties were investigated by UV-vis and fluorescence spectroscopy. The absorption spectra of these compounds showed wide spectral responses from 300 to 700 nm,which would be potentials for application as organic solar cells.     

可溶性的含羧基苝酰亚胺类化合物的合成及其光谱性质研究

本文主要以酐(1)为起始物,通过在环母体结构的1、6、7、12位上引入苯氧基和对甲基苯氧基合成了另外两种酐化合物(2a和2b);所得到的酐化合物与6-氨基已酸进行反应,合成了3种可溶性的含有羧基的酰亚胺化合物(3a、3b和3c),使用红外、紫外、荧光、¹H-NMR,元素分析对所合成的化合物进行了表征.经研究发现,环母体结构的1、6、7、12位上苯氧基和对甲基苯氧基的引入,能使得所合成的含羧基酰亚胺类化合物的最大吸收波长分别红移了44.1 nm和50.1 nm;Stokes位移变大,分别为34.1 nm和30.0 nm;而荧光量子产率有所降低但下降趋势不明显.     

Efficient Construction of Highly-fused Diperylene Bismides by Cu/Oxalic Diamide-promoted Zipper-mode Double C—H Activation

Copper/oxalic diamide-promoted dimerization of tetrachlorinated perylene bisimide to construct highly-fused diperylene bisimides through Ullmann coupling and zipper-mode double C—H activation has been developed in this study.This one-step reaction combining homocoupling with C—H activation proceeded smoothly under the action of inexpensive metal-ligand system.This protocol is expected to expand the available synthetic tools for condensed ring systems of perylene bisimide(PBIs).     

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.     

Water-soluble and fluorescent dendritic perylene bisimides for live-cell imaging

We prepared dendritic perylene bisimide probes with triblock structures: perylene bisimides fluorescence cores, branched oligo(glutamic acid)s and polyethylene glycol chains. These probes showed good water solubility, low cytotoxicity and strong fluorescence in live cells.     

Effects of bay substituents on the racemization barriers of perylene bisimides: resolution of atropo-enantiomers

The activation parameters for the interconversion of atropisomers (P- and M-enantiomer) of core-twisted perylene bisimides have been determined by dynamic NMR spectroscopy (DNMR) and time- and temperature-dependent CD spectroscopy. By comparing the activation parameters of a series of perylene bisimides containing halogen or aryloxy substituents in the bay area (1,6,7,12-positions), a clear structure-property relationship has been found that demonstrates that the kinetic and thermodynamic parameters for the inversion of enantiomers are dependent on the apparent overlap parameter Sigmar* of the bay substituents. This study reveals a high stability (DeltaG(368 K) = 118 kJ/mol) for the atropo-enantiomers of tetrabromo-substituted perylene bisimide in solution. Accordingly, the enantiomers of this derivative could be resolved by HPLC on a chiral column. These enantiomers do not racemize in solution at room temperature and, thus, represent the first examples of enantiomerically pure core-twisted perylene bisimides.     

The composite material of perylene bisimide dye in MCM-41 and its photophysical and photochemical properties

The mesoporous material MCM-41 was synthesized by a hydrothermal method, and perylene bisimide dye was incorporated into its channels by impregnation. The absorption, FTIR, fluorescence emission, and decay spectra of perylene bisimide dye in CHCl₃ and in MCM-41 were studied to investigate the effect of the one-dimensional channel of MCM-41 on the photophysical and photochemical properties of the dye. The results indicated that the nanochannels of MCM-41 shifted the absorption and emission maxima to red and broadened the spectra, with loss of vibrational structure. The fluorescence decay curves fitted a double-exponential function and the lifetime of perylene bisimide dye in MCM-41 was prolonged. The huge surface area of the mesoporous molecular sieve MCM-41 prevented aggregation of dye molecules, which can thus be used at high concentration.     

Fluorescent and electroactive cyclic assemblies from perylene tetracarboxylic acid bisimide ligands and metal phosphane triflates

Tetraaryloxy-substituted perylene tetracarboxylic acid bisimides with one or two 4-pyridyl receptor substituents at the imide functionality were synthesized and employed in transition metal directed self-assembly with Pd(II) and Pt(II) phosphane triflates. Upon mixing of the components, quantitative formation of functional molecular square-type complexes containing four dye molecules and model complexes of a 2:1 (perylene bisimide ligand:transition metal ion) stoichiometry was observed. The isolated metallosupramolecular squares were characterized by 1H and 31P [1H] NMR spectroscopy as well as conventional electrospray ionization (ESI) and ESI-FTICR mass spectrometry, which gave evidence for the structure and the high stability of these giant cyclic dye assemblies (molecular weight (3a) 8172, Pt-Pt corner diagonal ca. 3.4 nm). Studies of the optical absorption and fluorescence properties and the electrochemistry and spectroelectrochemistry of both the perylene bisimide ligands and the perylene bisimide metal complexes show that Pt(II) coordination does not interfere with the optical and electrochemical properties of the perylene bisimide ligands; this gives squares with high fluorescence quantum yields (phiF (3a)=0.88) and three fully reversible redox couples. The latter could be unambiguously related to quantitative formation of perylene bisimide radical cations (E1/2 = +0.93 V vs. Fc/Fc+), radical anions (E1/2= - 1.01 V vs. Fc/Fc+), and dianions (E1/2 = -1.14 V vs. Fc/Fc+); these redox reactions change the charge state of the cyclic assembly from +12 to zero. In contrast, Pd(II) coordination influenced the electrochemical properties of the assembly because of an irreversible palladium reduction at E1/2= -1.15 V versus Fc/Fc+. Finally, dynamic ligand exchange processes between different metallosupramolecular assemblies were investigated by multinuclear NMR and electrospray mass spectrometry. These studies confirmed the reversible nature of the pyridine-Pt(II)/Pd(II) coordination process.     

1,6‐Dinitroperylene Bisimide Dyes: Synthesis,Characterization and Photophysical Properties

1,6‐ and 1,7‐regioisomers of dinitro‐substituted perylene bisimides ( 1a — 1b and 2a — 2b ) were synthesized under mild condition in high yields. The 1,6‐ and 1,7‐regioisomers were successfully isolated from the regioisomeric mixture using conventional methods of separation and subsequently characterized by 500 MHz ¹H NMR spectroscopy. This is the first time when 1,6‐dinitroperylene bisimides ( 1a — 1b ) are obtained in pure form. Furthermore, the photophysical and electrochemical properties of 1 and 2 were found to be almost the same. The nitro functionalities provide stability of n‐type charge carriers by lowering the LUMO to resist ambient oxidation, which may offer potential applications in air‐stable n‐type organic semiconductors.     

Solubility and Crystallizability: Facile Access to Functionalized π‐Conjugated Compounds with Chlorendylimide Protecting Groups

Functional π‐conjugated molecules are relevant for the preparation of new organic electronic materials with improved performance. However, their synthesis is often rendered difficult by their inherently low solubility, and the permanent attachment of solubilizing groups may change the properties of the material. Here, we introduced the chlorendylimidyl moiety as a new temporary protecting group for the straightforward large‐scale synthesis of protected quarter‐, sexi‐, octathiophene, and perylene bisimide diamine and dicarboxylic acid derivatives. The obtained chlorendylimides and chlorendylimidyl active esters were highly soluble in organic solvents, and optical spectroscopy confirmed the low tendency of the compounds to aggregate in solution. At the same time, they could be conveniently purified by recrystallization or precipitation. Single‐crystal X‐ray structures obtained for most compounds showed supramolecular motifs highlighting the role of the rigid, polychlorinated chlorendyl moieties in their crystallization. The obtained protected diamine and dicarboxylic acid derivatives were easily deprotected and converted into various amide‐substituted oligothiophenes and perylene bisimides that are of interest as new functional materials for organic electronic thin film or nanowire devices.