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Self-assembly versus complexation with polycyclic aromatic hydrocarbon (PAH) guest molecules is studied for a series of perylene bisimides (PBIs). Bulky imide substituents at the PBI guide their self-assembly into dimer aggregates with null-type exciton coupling. Host–guest titration experiments with perylene and triphenylene PAHs afford 1 : 1 and 1 : 2 complexes whose properties are studied by single crystal X-ray analysis and UV/Vis and fluorescence spectroscopy. [ABSTRACT FROM AUTHOR]

Perylene bisimides (PBIs) are among the best fluorophores but have to be enwrapped for optoelectronic applications by large and heavy substituents to prevent their ππ‐stacking, which is known to accelerate non‐radiative decay processes in the solid state. Here, light‐weight di‐tert‐butylsilyl groups are introduced to bridge 1,12‐dihydroxy and 1,6,7,12‐tetrahydroxy PBIs to afford sublimable dyes for vacuum‐processed optoelectronic devices. For both new compounds, this substitution provides a twisted and shielded perylene π‐core whose, via OSiObridges, rigid structure affords well‐resolved absorption and emission spectra with strong fluorescence in solution, as well as in the solid state. The usefulness of these dyes for vacuum‐processed optoelectronic devices is demonstrated in organic light‐emitting diodes (OLEDs) that show monomer‐like emission spectra and high maximum external quantum efficiency (EQEmax) values of up to 3.1% for the doubly silicon‐bridged PBI. [ABSTRACT FROM AUTHOR]

Multichromophoric macrocycles and cyclophanes are important supramolecular architectures for the elucidation of interchromophoric interactions originating from precise spatial organization. Herein, by combining an axially chiral binaphthol bisimide (BBI) and a bay‐substituted conformationally labile twisted perylene bisimide (PBI) within a cyclophane of well‐defined geometry, we report a chiral PBI hetero‐cyclophane (BBI‐PBI) that shows intramolecular energy and solvent‐regulated chirality transfer from the BBI to the PBI subunit. Excellent spectral overlap and spatial arrangement of BBI and PBI lead to efficient excitation energy transfer and subsequent PBI emission with high quantum yield (80–98 %) in various solvents. In contrast, chirality transfer is strongly dependent on the respective solvent as revealed by circular dichroism (CD) spectroscopy. The combination of energy and chirality transfer affords a bright red circularly polarized luminescence (CPL) from the PBI chromophore by excitation of BBI. [ABSTRACT FROM AUTHOR]

A series of donor‐acceptor (D−A) macrocyclic dyads consisting of an electron‐poor perylene bisimide (PBI) π‐scaffold bridged with electron‐rich α‐oligothiophenes bearing four, five, six and seven thiophene units between the two phenyl‐imide substituents has been synthesized and characterized by steady‐state UV/Vis absorption and fluorescence spectroscopy, cyclic and differential pulse voltammetry as well as transient absorption spectroscopy. Tying the oligothiophene strands in a conformationally fixed macrocyclic arrangement leads to a more rigid π‐scaffold with vibronic fine structure in the respective absorption spectra. Electrochemical analysis disclosed charged state properties in solution which are strongly dependent on the degree of rigidification within the individual macrocycle. Investigation of the excited state dynamics revealed an oligothiophene bridge size‐dependent fast charge transfer process for the macrocyclic dyads upon PBI subunit excitation. [ABSTRACT FROM AUTHOR]

A new type of cathode interlayer composed of 2,6‐di‐tert‐butyl‐phenol‐functionalized perylene bisimide (PBI‐2P) is successfully applied as an electron transporting layer for fused‐ring nonfullerene organic solar cells (OSCs). The stable contact between these novel electron transporting layers and the representative nonfullerene acceptor Y6 greatly enhances the device stability compared to conventional amine‐group containing cathode interlayers. Moreover, the easily formed biradical species in the interlayers yields rather good thickness tolerance of the PBI‐2P layer in photovoltaic devices. The OSCs based on the PBI‐2P interlayer show a power conversion efficiency up to 17.20% and good stability compared to amino‐group functionalized interlayers. The findings demonstrate a promising design principle for cathode interlayer engineering based on pigment chromophores equipped with the 2,6‐di‐tert‐butylphenoxy groups that are prone to form the respective ultrastable butylphenoxy radicals for stable nonfullerene OSCs. [ABSTRACT FROM AUTHOR]

The first planar π‐extended azulene that retains aromaticity of odd‐membered rings was synthesized by [3+3] peri‐annulation of two naphthalene imides at both long‐edge sides of azulene. Using bromination and subsequent nucleophilic substitution by methoxide and morpholine, selective functionalization of the π‐extended azulene was achieved. Whilst these new azulenes can be regarded as isomers of terrylene bisimide they exhibit entirely different properties, which include very narrow optical and electrochemical gaps. DFT, TD‐DFT, as well as nucleus‐independent chemical shift calculations were applied to explain the structural and functional properties of these new π scaffolds. Furthermore, X‐ray crystallography confirmed the planarity of the reported π‐scaffolds and aromaticity of their azulene moiety. [ABSTRACT FROM AUTHOR]

We report the direct imidization of naphthalene and perylene dicarboxylic anhydrides/esters with bulky ortho,ortho‐diaryl‐ and ortho,ortho‐dialkynylaniline derivatives. This imidization method uses n‐butyllithium as a strong base to increase the reactivity of bulky amine derivatives, proceeds under mild reaction conditions, requires only stoichiometric amounts of reactants and gives straightforward access to new sterically crowded rylene dicarboximides. Mechanistic investigations suggest an isoimide as intermediary product, which was converted to the corresponding imide upon addition of an aqueous base. Single‐crystal X‐ray diffraction analyses reveal dimeric packing motifs for monoimides, while two‐side shielded bisimides crystallize in isolated molecules without close π–π‐interactions. Spectroscopic investigations disclose the influence of the bulky substituents on the optical properties in the solid state. [ABSTRACT FROM AUTHOR]

Depending on the connectivity of solubilizing oligoethylene glycol (OEG) side chains to the π‐cores of amphiphilic naphthalene and perylene bisimide dyes, self‐assembly in water occurs either upon heating or cooling. Herein, we show that this effect originates from differences in the enwrapping capability of the π‐cores by the OEG chains. Rylene bisimides bearing phenyl substituents with three OEG chains attached directly to the hydrophobic π‐cores are strongly sequestered by the OEG chains. These molecules self‐assemble at elevated temperatures in an entropy‐driven process according to temperature‐ and concentration‐dependent UV/Vis spectroscopy and calorimetric dilution studies. In contrast, for rylene bisimides in which phenyl substituents with three OEG chains are attached via a methylene spacer, leading to much weaker sequestration, self‐assembly originates upon cooling in an enthalpy‐driven process. Our explanation for this controversial behavior is that the aggregation in the latter case is dictated by the release of "high energy water" from the hydrophobic π‐surfaces as well as dispersion interactions between the π‐scaffolds which drive the self‐assembly in an enthalpically driven process. In contrast, for the former case we suggest that in addition to the conventional explanation of a dehydration of hydrogen‐bonded water molecules from OEG units it is in particular the increase in conformational entropy of back‐folded OEG side chains upon aggregation that provides the pronounced gain in entropy that drives the aggregation process. Thus, our studies revealed that a subtle change in the attachment of solubilizing substituents can switch the thermodynamic signature for the self‐assembly of amphiphilic dyes in water from enthalpy‐ to entropy‐driven. [ABSTRACT FROM AUTHOR]

The self-assembly of a new perylene bisimide (PBI) organogelator with 1,7-dimethoxy substituents in the bay position affords non-fluorescent H-aggregates at high cooling rates and fluorescent J-aggregates at low cooling rates. Under properly adjusted conditions, the kinetically trapped 'off-pathway' H-aggregates are transformed into the thermodynamically favored J-aggregates, a process that can be accelerated by the addition of J-aggregate seeds. Spectroscopic studies revealed a subtle interplay of π-π interactions and intra- and intermolecular hydrogen bonding for monomeric, H-, and J-aggregated PBIs. Multiple polymerization cycles initiated from the seed termini demonstrate the living character of this chain-growth supramolecular polymerization process. [ABSTRACT FROM AUTHOR]

An unprecedented crystal-packing arrangement of a tetramethoxy-bay-substituted perylene bisimide (PBI) consists of three crystallographically independent molecules, that is, an achiral ( AC) PBI of saddle-shaped geometry along with two pairs of propeller-like twisted ( P)- and ( M)-enantiomeric PBI frameworks. All these five conformations are observed within a single π-stack revealing an intriguing packing sequence with an inversion of chirality from P to M via AC. Nudged elastic band calculations for the isolated molecule show that AC is a local minimum of the P to M interconversion path. In addition, two minor conformations were observed in the crystal, one of which resembles a transition-state molecule. Theoretical studies of dimeric and trimeric stacks reveal that the coexistence of all these structures in the crystal lattice is aided by the strong dispersion interactions between PBI cores and perfectly interdigitated dodecyl chains which stabilize energetically higher conformations. [ABSTRACT FROM AUTHOR]

Aromatic bis(dicarboximides), abbreviated as bisimides or diimides, are interesting building blocks for the construction of electro- and photofunctional architectures. The possibility of reversible reduction of aromatic molecules equipped with imide units at modest redox potentials between about −1.3 and −1.0 V vs. the ferrocenium/ferrocene redox couple could be exploited by a broad variety of electroactive cyclophanes, macrocycles and catenane scaffolds to direct molecular motions by charging the systems with electrons. Whilst most of the work in this field has been accomplished for the smaller pyromellitic (PyBI) and naphthalene bisimides (NBI), the larger perylene bisimides (PBI) offered an entry into the field of photofunctional systems. Here cyclophanes with closely stacked PBI units provided insight into exciton coupling in homo and hetero dye dimers or ultrafast loss of coherence of the initially populated exciton states to give excimers or symmetry-broken charge separated states. In contrast, for PBI cyclophanes with larger cavities guest encapsulation could efficiently modulate the photophysical properties to give highly fluorescent host–guest complexes upon incorporation of electron-poor aromatic guest molecules or fully quenched systems upon incorporation of electron-rich molecules. For larger PBI macrocycles energy transfer processes could be investigated as well as the solvent-templated folding into double string ropes with high sensitivity (absorption, fluorescence) for the specific aromatic solvents. Finally, with a metallosupramolecular approach larger macrocycles (e.g. squares and hexagons) and cages (e.g. tetrahedrons) became accessible which could be exploited to study a variety of electro- and photophysical processes. [ABSTRACT FROM AUTHOR]

A new perylene bisimide (PBI) dye self-assembles through hydrogen bonds and π-π interactions into J-aggregates that in turn self-organize into liquid-crystalline (LC) columnar hexagonal domains. The PBI cores are organized with the transition dipole moments parallel to the columnar axis, which is an unprecedented structural organization in π-conjugated columnar liquid crystals. Middle and wide-angle X-ray analyses reveal a helical structure consisting of three self-assembled hydrogen-bonded PBI strands that constitute a single column of the columnar hexagonal phase. This remarkable assembly mode for columnar liquid crystals may afford new anisotropic LC materials for applications in photonics. [ABSTRACT FROM AUTHOR]

Binding of guest molecules with high affinity and selectivity requires well-designed hosts to provide optimized interactions in the host-guest complexes. Herein we report the design and synthesis of new cyclophanes 2PBI(2,6- iPr)2 and 2PBI(2,6-Ph)2 based on core-disubstituted perylene bisimide (PBI) chromophores bearing two phenoxy bay-substituents that evoke almost planar PBI scaffolds. This strategy afforded the new cyclophanes with conformationally rigid cavities to ensure strong binding to stiff planar polycyclic aromatic hydrocarbons (PAHs). Our detailed host-guest binding studies with different PAHs by UV/Vis and fluorescence titration experiments revealed record binding strengths for PAHs with binding constants of up to 1.6×106 m−1 in chloroform at room temperature. One- and two-dimensional NMR experiments and solvent-dependent titration studies revealed self-encapsulation of the side arms of PBI bay-substituents into the cavities that attained high fluorescence quantum yields of these cyclophanes close to unity by preventing the interaction of PBI subunits in the excited states. The binding constants and Gibbs free energies of host-guest complexations disclosed significant effects of PBI bay-substituents and core twist on the binding affinity of the cyclophanes. [ABSTRACT FROM AUTHOR]

The specific hydrophobic effect involved in the self-assembly of a bolaamphiphilic perylene bisimide (PBI) dye bearing oligoethylene glycol (OEG) chains has been identified. In pure water, the self-assembly is entropically driven and enthalpically disfavored, as explored by optical spectroscopy and isothermal titration calorimetry studies. Besides strong π-π interactions between the PBI units that are primarily of enthalpic nature, the major contribution to the self-assembly is the gain of entropy by release of confined water molecules from the hydration shell of the hydrophilic OEG moieties. Both contributions favor self-assembly, but their countervailing thermodynamic parameters are reflected in an uncommon temperature dependence, which can be inverted upon gradual addition of an organic cosolvent that makes the π-π interaction increasingly dominant. [ABSTRACT FROM AUTHOR]

Unprecedented neutral perylene-3,4:9,10-tetracarboxylic acid bisimide (PBI) radicals and biradicals were synthesized by facile chemical oxidation of 4-hydroxyarylsubstituted PBIs. Subsequent characterization by optical and magnetic spectroscopic techniques, as well as quantum chemical calculations, revealed an open-shell singlet biradical ground state for the PBI biradical OS-2" (=1.2191) with a relatively small singlet-triplet energy gap of 0.041 eV and a large singlet biradical character of y=0.72. [ABSTRACT FROM AUTHOR]

A rigid, covalently linked perylene-3,4:9,10-tetracarboxylic acid bisimide (PBI) cyclophane was synthesized by imidization of a bay-substituted perylene bisanhydride with p-xylylenediamine. The interchromophoric distance of approximately 6.5 Å establishes an ideal rigid cavity for the encapsulation of large aromatic compounds such as perylene and anthracene with binding constants up to 4.6×104 M−1 (in CHCl3). For electron-poor guest molecules, the complexation process is accompanied by a significantly increased fluorescence, whereas the emission intensity is dramatically quenched by more electron-rich guests because of the formation of charge-transfer complexes. Furthermore, the influence of the PBI core twist on the binding constant results in a remarkable selectivity towards more flexible aromatic guest molecules. [ABSTRACT FROM AUTHOR]

A broad series of homochiral perylene bisimide (PBI) dyes were synthesized that are appended with amino acids and cationic side chains at the imide positions. Self-assembly behavior of these ionic PBIs has been studied in aqueous media by UV/Vis spectroscopy, revealing formation of excitonically coupled H-type aggregates. The interactions of these ionic PBIs with different ds-DNA and ds-RNA have been explored by thermal denaturation, fluorimetric titration and circular dichroism (CD) experiments. These PBIs strongly stabilized ds-DNA/RNA against thermal denaturation as revealed by high melting temperatures of the formed PBI/polynucleotide complexes. Fluorimetric titrations showed that these PBIs bind to ds-DNA/RNA with high binding constants depending on the number of the positive charges in the side chains. Thus, spermine-containing PBIs with six positive charges each showed higher binding constants (log Ks=9.2-9.8) than their dioxa analogues (log Ks=6.5-7.9) having two positive charges each. Induced circular dichroism (ICD) of PBI assemblies created within DNA/RNA grooves was observed. These ICD profiles are strongly dependent on the steric demand of the chiral substituents of the amino acid units and the secondary structure of the DNA or RNA. The observed ICD effects can be explained by non-covalent binding of excitonically coupled PBI dimer aggregates into the minor groove of DNA and major groove of RNA which is further supported by molecular modeling studies. [ABSTRACT FROM AUTHOR]

The unexpected introduction of a cationic imidazolium substituent in the 2-position of a tetrachloro-substituted perylene-3,4:9,10-tetracarboxylic acid bisimide (PBI) by the reaction of PBI-Cl4 1 with the N-heterocyclic carbene 1,3-di-iso-propyl-imidazolin-2-ylidene (iPr2Im 2) enables the isolation of an ambient stable zwitterionic radical. The remarkable stability of this unprecedented PBI-centered radical facilitates the complete characterization by several spectroscopic methods as well as single crystal structure analysis. Redox studies revealed that iPr2Im-PBI-Cl4 4 can be transferred reversibly to the corresponding anion and cation, respectively, even on a preparative scale. [ABSTRACT FROM AUTHOR]

Two new perylene bisimide (PBI) derivatives possessing crown ether receptors at the 1,7 bay-positions and solubilizing ionic imide substituents were synthesized and their self-assembly properties in the presence of different metal ions were studied, revealing highly selective barium ion templated self-assembly of 15-crown-5 functionalized PBI into H-type dimer aggregates. [ABSTRACT FROM AUTHOR]

Formation of a tetrahedron with >4 nm perylene bisimide (PBI) dye edges and ZnII vertices in a one-pot 22 component self-assembly reaction is reported. The luminescent polyhedron equilibrates to a Zn2L3 helicate and disassembles upon dilution. Insights into the subcomponent self-assembly of extended PBI ligands help to refine design rules for constructing large photofunctional metallosupramolecular hosts. [ABSTRACT FROM AUTHOR]

The phosphorescence emission of perylene bisimide derivatives has been rarely reported. Two novel ruthenium(II) and iridium(III) complexes of an azabenz-annulated perylene bisimide (ab-PBI), [Ru(bpy)2(ab-PBI)][PF6]2 1 and [Cp*Ir- (ab-PBI)Cl]PF6 2 are now presented that both show NIR phosphorescence between 750-1000 nm in solution at room temperature. For an NIR emitter, the ruthenium complex 1 displays an unusually high quantum yield (Φp) of 11% with a lifetime (τp) of 4.2 μs, while iridium complex 2 exhibits Φp< 1% and τp=33 μs. 1 and 2 are the first PBI-metal complexes in which the spin-orbit coupling is strong enough to facilitate not only the Sn→Tn intersystem crossing of the PBI dye, but also the radiative T1→S0 transition, that is, phosphorescence. [ABSTRACT FROM AUTHOR]

In this work, we have elucidated in detail the folding properties of two perylene bisimide (PBI) foldamers composed of two and three PBI units, respectively, attached to a phenylene ethynylene backbone. The folding behaviors of these new PBI folda-dimer and trimer have been studied by solvent-dependent UV/Vis absorption and 1D and 2D NMR spectroscopy, revealing facile folding of both systems in tetrahydrofuran (THF). In CHCl3 the dimer exists in extended (unfolded) conformation, whereas partially folded conformations are observed in the trimer. Temperature-dependent 1H NMR spectroscopic studies in [D8]THF revealed intramolecular dynamic processes for both PBI foldamers due to, on the one hand, hindered rotation around CN imide bonds and, on the other hand, backbone flapping; the latter process being energetically more demanding as it was observed only at elevated temperature. The structural features of folded conformations of the dimer and trimer have been elucidated by different 2D-NMR spectroscopy (e.g., ROESY and DOSY) in [D8]THF. The energetics of folding processes for the PBI dimer and trimer have been assessed by calculations applying various methods, particularly the semiempirical PM6-DH2 and the more sophisticated B97D approach, in which relevant dispersion corrections are included. These calculations corroborate the results of NMR spectroscopic studies. Folding features in the excited states of these PBI foldamers have been characterized by using time-resolved fluorescence and transient absorption spectroscopy in THF and CHCl3, exhibiting similar solvent-dependent behavior as observed for the ground state. Interestingly, photoinduced electron transfer (PET) process from electron-donating backbone to electron-deficient PBI core for extended, but not for folded, conformations was observed, which can be explained by a fast relaxation of excited PBI stacks in the folded conformation into fluorescent excimer states. [ABSTRACT FROM AUTHOR]

Armdrücken: Die Rückgrat ‐ dirigierte „Arm ‐ in ‐ Arm“ ‐ Aggregation einer neuartigen Perylenbisimid(PBI) ‐ Dyade mit einem festgelegten intramolekularen Abstand führt zur Bildung von kinetisch stabilen erweiterten PBI ‐ π ‐ Stapeln. Es wird gezeigt, dass sich die PBI ‐ Dyade zu Oligomeren aus bis zu 21 Einheiten anordnet. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Selbstorganisation: Eine Perylenbisimid(PBI) ‐ Dyade bildet durch Selbstorganisation einen bimolekularen Komplex, der aus einem Stapel von vier PBI ‐ π ‐ Einheiten besteht und dessen hohe kinetische Stabilität für π ‐ gestapelte Farbstoffaggregate beispiellos ist (siehe Bild). Diese ausgedehnten supramolekularen Systeme sind von Interesse für die Aufklärung der funktionellen Eigenschaften von Farbstoffaggregaten. [ABSTRACT FROM AUTHOR]

We describe the thermodynamic characterization of the assembly process of a covalently connected trimeric Zn porphyrin 1 induced by coordination to a bispyridyl functionalized perylene bisimide 2. The perylene bisimide ligands act as pillars via two axial coordination bonds with the porphyrinic Zn(II) ions fixing the planes of the porphyrin units in a nearly co-facial orientation and inducing the formation of trigonal prism-like structures. The fully assembled 12·23 aggregate and the partially assembled one, 12·22, in which only two zinc porphyrin sites of trimeric 1 are axially coordinated to 2, are present in solution in equilibrium with freely diffusing species 1 and 2. The strong quenching observed in the mixture for the luminescence of the components 2 and 1 is ascribed to an efficient photoinduced electron transfer from the Zn porphyrin units of 1 to coordinated 2 occurring upon excitation of both components within the assemblies. In the formed assemblies, the Zn porphyrin units of the trimer 1 behave independently. Thus, the porphyrin units that are not coordinated with 2 in the partially assembled complex, 12·22, display the same photophysical behaviour registered for freely diffusing 1. The rate of charge separation within the cage is nearly independent on the polarity of the solvent (ca. 1010 s-1) whereas the charge recombination process, leading to the ground state, has a lifetime of 110 ps in dichloromethane and ca. 6 ns in toluene, in agreement with a Marcus inverted behaviour. [ABSTRACT FROM AUTHOR]

Four sterically shielded aromatic bisimides are synthesized and their ability to form cocrystals with the triplet sensitizer platinum(II) acetylacetonate (Pt(acac)2) is investigated. Single crystals of the individual electron‐deficient bisimides are studied first, two showing bright blue fluorescence with quantum yields of up to 28%, while the other two barely emit at all. After successful cocrystallization of all four aromatic bisimides with the electron‐rich Pt(II) complex, two different stoichiometries, either 1:1 or 1:2, are found in the crystalline solid state, whose absorbance and photoluminescence exhibit distinct bathochromic shifts. While two naphthalene bisimides show strong and long‐lived room‐temperature phosphorescence (RTP) with quantum yield exceeding 50%, the other two aromatic bisimides show only minor photoluminescence at RT, but a bright low‐temperature phosphorescence (LTP) at 80 K. Theoretical calculations reveal the importance of changing the magnetic quantum number ml of the involved d‐orbitals at the platinum center as well as the alignment of the Pt(II) center above an aromatic C─C bond for an efficient intersystem crossing in these hybrid systems. [ABSTRACT FROM AUTHOR]

Nucleophilic substitution of 1,6,7,12-tetrachloro perylene bisimide (PBI) with n-butanethiol provided a novel, highly twisted PBI bearing four sulphur coordination sites at the bay positions, from which silver and palladium complexes were prepared. [ABSTRACT FROM AUTHOR]

Self-assembly of octahedral Fe(II) ions and linear perylene bisimide (PBI) dyes with 2,2′-bipyridine groups covalently attached at the imide positions quantitatively yields an Fe4(PBI)6 tetrahedron by the directional bonding approach. With an edge length of 3.9 nm and estimated internal volume >950 Å3, tetrahedron T is one of the largest M4L6 tetrahedra ever reported. Importantly, many of the desirable photo- and electroactive properties of the PBI ligands are transferred to the nanoscale metallosupramolecule. Tetrahedron T absorbs strongly across the visible spectrum out to 650 nm and exhibits a total of 7 highly reversible electrochemical oxidation and reduction waves spanning a 3.0 V range. This facile cycling of 34 electrons between +18 and −16 charged species is likely enabled due to the porous nature of the tetrahedron that allows the necessary counterions to freely flow in and out of the host. Host−guest encapsulation of C60 by T in acetonitrile was studied by 13C NMR spectroscopy, UV−vis spectroscopy, and ESI-MS, confirming that the tetrahedron is a suitable host for large, functional guest molecules. [ABSTRACT FROM AUTHOR]

An adequately designed, bay-tethered perylene bisimide (PBI) dimer Bis-PBI was synthesized by Pd/Cu-catalyzed Glaser-type oxidative homocoupling of the respective PBI building block. This newly synthesized PBI dimer self-assembles exclusively and with high binding constants of up to 106 M-1 into a discrete π-stack of four chromophores. Steady-state absorption and emission spectra show the signatures of H-type excitonic coupling among the dye units. Broadband fluorescence upconversion spectroscopy (FLUPS) reveals an ultrafast dynamics in the optically excited state. An initially coherent Frenkel exciton state that is delocalized over the whole quadruple stack rapidly (τ = ~200 fs) loses its coherence and relaxes into an excimer state. Comparison with Frenkel exciton dynamics in PBI dimeric and oligomeric H-aggregates demonstrates that in the quadruple stack coherent exciton propagation is absent due to its short length of aggregates, thereby it has only one relaxation pathway to the excimer state. Furthermore, the absence of pump-power dependence in transient absorption experiments suggests that multiexciton cannot be generated in the quadruple stack, which is in line with time-resolved fluorescence measurements. [ABSTRACT FROM AUTHOR]

A series of semirigid perylene bisimide (PBI) macrocycles with varied ring size containing two to nine PBI chromophores were synthesized in a one-pot reaction and their photophysical properties characterized by fluorescence, steady-state, and transient absorption spectroscopy as well as femtosecond stimulated Raman spectroscopy. These macrocycles show solvent-dependent conformational equilibria and excited-state properties. In dichloromethane, the macrocycles prevail in wide-stretched conformations and upon photoexcitation exhibit symmetry-breaking charge separation followed by charge recombination to triplet states, which photosensitize singlet oxygen formation. In contrast, in aromatic solvents folding of the macrocycles with a distinct odd-even effect regarding the number of PBI chromophore units was observed in steady-state and time-resolved absorption and fluorescence spectroscopy as well as femtosecond stimulated Raman spectroscopy. These distinctive optical properties are attributable to the folding of the even-membered macrocycles into exciton-vibrational coupled dimer pairs in aromatic solvents. Studies in a variety of aromatic solvents indicate that these solvents embed between PBI dimer pairs and accordingly template the folding of even-membered PBI macrocycles into ropelike folded conformations that give rise to solvent-specific exciton-vibrational couplings in UV-vis absorption spectra. As a consequence of the embedding of solvent molecules in the coiled double-string rope architecture, highly solvent specific intensity ratios are observed for the two lowest-energy exciton-vibrational bands, enabling assignment of the respective solvent simply based on the absorption spectra measured for the tetramer macrocycle. [ABSTRACT FROM AUTHOR]

We have elucidated excimer-mediated intra-molecular electron transfer in cofacially stacked PBIs tethered by two phenylene-butadiynylene loops. The electron transfer between energetically equivalent PBIs is revealed by the simultaneous observation of the PBI radical anion and cation bands in the transient absorption spectra. The fluorescence decay time of the excimer states is in good agreement with the rise time of PBI radical bands in transient absorption spectra suggesting that the electron transfer dynamics proceed via the excimer state. We can conclude that the excimer state effectuates the efficient charge transfer in the cofacially stacked PBI dimer. [ABSTRACT FROM AUTHOR]

We have investigated the kinetic and thermodynamic supramolecular polymerizations of a series of amide-functionalized perylene bisimide (PBl) organogelator molecules bearing alkyl spacers of varied lengths (ethylene to pentylene chains, PBI-1-C2 to PBI-1-C5) between the amide and PBI imide groups. These amide-functionalized PBIs form one-dimensional fibrous nanostructures as the thermodynamically favored states in solvents of low polarity. Our in-depth studies revealed, however, that the kinetic behavior of their supramolecular polymerization is dependent on the spacer length. Propylene- and pentylene-tethered PBIs follow a similar polymerization process as previously observed for the ethylene-tethered PBI. Thus, the monomers of these PBIs are kinetically trapped in conformationally restricted states through intramolecular hydrogen bonding between the amide and imide groups. In contrast, the intramolecularly hydrogen-bonded monomers of butylene-tethered PBI spontaneously self-assemble into nanoparticles, which constitute an off-pathway aggregate state with regard to the thermodynamically stable fibrous supramolecular polymers obtained. Thus, for this class of jr-conjugated system, an unprecedented off-pathway aggregate with high kinetic stability could be realized for the first time by introducing an alkyl linker of optimum length (C4 chain) between the amide and imide groups. Our current system with an energy landscape of two competing nucleated aggregation pathways is applicable to the kinetic control over the supramolecular polymerization by the seeding approach. [ABSTRACT FROM AUTHOR]

We present a model for the relaxationdynamics in perylene bisimidedimers, which is based on ab initio electronic structure and quantumdynamics calculations including effects of dissipation. The excited-statedynamics proceeds via a mixing of electronic states of local Frenkeland charge-transfer characters, which becomes effective upon a smalldistortion of the dimer geometry. In this way, it is possible to explainthe fast depopulation of the photoexcited state, which we characterizeby femtosecond transient absorption measurements. The combined theoreticaland experimental analysis hints at a trapping mechanism, which involvesnonadiabatic and dissipative dynamics in an excited-state vibronicmanifold and provides an atomistic picture that might prove valuablefor future design of photovoltaic materials. [ABSTRACT FROM AUTHOR]

The concentration-dependent absorption and temperature-dependent fluorescence of the perylene bisimide dye PBI 1 in methylcyclohexane point to a biphasic aggregation behavior. At intermediate concentrations and temperatures, respectively, a dimer with low fluorescence yield dominates, which cannot be extended to longer aggregates. Those are formed at high concentrations and low temperatures, respectively, via a second, energetically unfavorable dimer species that acts as a nucleus. A corresponding aggregation model reproduces accurately the concentration dependence and allows extracting the equilibrium constants and spectra of the distinct species. The differences in the photophysical properties indicate H-type excitonic coupling for the favored dimer and J-type characteristics for the extended aggregates which could be related to structural models based on DFT calculations. The energetics can be understood by considering hydrogen-bonding and π–π-stacking interactions. [ABSTRACT FROM AUTHOR]