Perylene Diimide Moieties Research Articles

Synthesis and spectral properties of ruthenium(II) complexes based on 2,2′-bipyridines modified by a perylene chromophore

Abstract Five new 2,2′-bipyridines functionalized with a perylene or a perylenediimide moiety were synthesized and the corresponding heteroleptic ruthenium(II) complexes ([Ru(bpy) 2 ( L )](PF 6 ) 2 ; bpy = 2,2′-bipyridyl, L = perylene-substituted bpy ligand) were prepared. The UV–vis spectra of the ruthenium(II) complexes showed red-shifted and intense absorption bands derived from the conjugated structure of the new ligands.

Charge and energy transfer in a bithiophene perylenediimide based donor–acceptor–donor system for use in organic photovoltaics

The elementary charge and excitation energy transfer steps in a novel symmetric donor-acceptor-donor triad first described in Roland et al. Phys. Chem. Chem. Phys., 2012, 14, 273, consisting of a central perylenediimide moiety as a potential electron acceptor and two identical electron rich bithiophene compounds, have been investigated using quantum chemical methodology. These elementary processes determine the applicability of such systems in photovoltaic devices. The molecular structure, excited states and the photo-physical properties are investigated using smaller model systems and including solvation effects. The donor and acceptor π-systems are separated by an ethyl bridge such that the molecular orbitals are either located on the donor or acceptor moiety making the identification of locally excited versus charge transfer states straightforward. Using excited state geometry optimizations, the mechanism of photo-initiated charge separation could be identified. Geometry relaxation in the excited donor state leads to a near-degeneracy with the locally excited acceptor state, entailing strong excitonic coupling and resonance energy transfer. This energy transfer process is driven by planarization and bond length alternation of the donor molecule. Geometry relaxation of the locally excited acceptor state in turn reveals a crossing with the energetically lowest charge transfer excited state. The energetic position of the latter depends in a sensitive fashion on the solvent. This provides an explanation of the sequential process observed in the experiment, favoring ultrafast (∼130 fs) formation of the excited acceptor state followed by slower (∼3 ps scale) formation of the charge separated state.

Sub-100 fs charge transfer in a novel donor–acceptor–donor triad organized in a smectic film

Ultrafast transient absorption spectroscopy is performed on a novel donor-acceptor-donor triad made of two identical bisthiophene derivatives as electron donors and a central perylenediimide moiety as electron acceptor. The triad is extended at both ends by covalently bound siloxane chains that confer self-organisation into thin smectic films at ambient temperature. When diluted in chloroform, selective excitation of the donor moiety leads to resonance energy transfer within 130 fs to the acceptor moiety, followed by the formation of a charge transfer (CT) state in ~3 ps. The CT state recombines entirely on a 55 ps time scale. In the liquid crystal films, excitonic intermolecular coupling leads to significant changes in the dynamics. Most remarkably, ultrafast intra- and intermolecular CT state formation occurs in about 60 fs, i.e. on a time scale comparable to electronic coherence times. While the intra-molecular CT states recombine on the same time scale as in solution or even faster, inter-molecular CT states live for about 1 ns. Last, triplet states of the perylenediimide moiety dominate the differential absorption after ~1 ns. We anticipate that the fast recombination of intra-molecular CT states and the triplet state formation may severely limit the photo-current in these materials.

Synthesis and properties of fluorene-oligothiophenes perylenediimide triads and their electropolymerizations

A series of novel donor–acceptor–donor triads, namely PFTn (n = 0–4), consisting of fluorene-oligothiophenes (FTn) as a donor and perylenediimide (PDI) as an acceptor were synthesized and characterized. The chemically bonded electron donor and acceptor chromophores in the triads were found to be independent. These triads showed a strong intramolecular photo-induced electron transfer (PET) between both chromophores, which gave rise to a quasi-quantitative fluorescence quenching of both PDI and FTn moieties. Distinctively, a reverse energy transfer from the acceptor PDI to the donor FTn induced a strong fluorescence emission from the FTn moieties in the triads PFT3 and PFT4. The PFTn (n = 1–3) triads were proven to undergo an electrochemical oxidative coupling reaction and become electropolymerizable materials to form polymer plastic films (poly(PFTnn)), while PFT4 proved to be an electrochemically stable molecule.

Synthesis and characterization of n-type conjugated copolymers bearing perylene diimide moieties

Three electron-deficient conjugated polymers based on perylene diimide (PDI) units, namely, poly[(N,N′-didodecyl-3,4,9,10-perylene diimide-1,7-diyl)-alt-(9,9-dihexylfluorene-2,7-diyl)] (PPDIF), poly{(N,N′-didodecyl-3,4,9,10-perylene diimide-1,7-diyl)-alt-[N-(2-ethylhexyl) carbazole-3, 6-diyl]} (PPDIC) and poly{(N,N′-didodecyl-3,4,9,10-perylene diimide-1,7-diyl)-co-[N-(2-ethylhexyl) carbazole-3,6-diyl]-co-(9,9-dihexylfluorene-2,7-diyl)} (PPDICF) have been synthesized via Suzuki coupling reaction, and their chemical structures are confirmed by 1H NMR, 13C NMR and FT-IR. All these polymers show broad absorption bands in 250–700 nm, and their optical band gaps are calculated to be ~1.7 eV. Cyclic voltammetry results confirm that the objective macromolecules possess high electron affinity of ~3.9 eV. By employing poly-3-hexylthiophene (P3HT) as electron donor and PPDIC as electron acceptor, all polymer solar cells (aPSCs) with bulky heterojunction structure have been fabricated, preliminary results indicate they have one of the most highest open-circuit voltage (Voc) (0.86 V) reported so far in aPSCs with PDI-based polymers as electron acceptor.

Fullerodendrimers with a perylenediimide core

Dendritic C60–perylenediimide (PDI) conjugates PerG1–PerG3 have been prepared under esterification conditions starting from a perylene diol building block (Per) and fullerodendrons bearing a carboxylic acid function at the focal point. The cyclic voltammograms recorded for PerG1–PerG3 show the characteristic electrochemical features of both constitutive units, i.e.methanofullerene and PDI. The comparison with the corresponding model compounds (Per and F) shows that the oxidation of the dendrimers is centered on the PDI core, while the first reduction corresponds to a fullerene-centred process. The photophysical properties of PerG1–PerG3 and of the related reference systems Per and F were investigated in toluene solution. Per and F exhibit almost superimposed fluorescence bands sitting across the Vis and NIR spectral regions, showing that the corresponding singlet states are virtually isoenergetic (∼1.75 eV). The two bands are characterized by very different fluorescence quantum yields and short singlet lifetimes; Per: Φfluo = 7.8%, τ = 3.7 ns; F: Φfluo = 0.04%, τ = 1.8 ns. In the dendrimers, the isoenergetic singlet levels of the PDI and fullerene moieties lead to a very peculiar luminescence behaviour that is invariably found regardless of the excitation wavelength. The detected fluorescence band in PerG1–PerG3 has always the shape of the PDI central core, reduced in intensity by about 20 times compared to Per, whilst the lifetime is that of the peripheral fullerene unit. At 298 K, this unconventional behaviour is interpreted by a kinetic model involving fast equilibration of the singlet levels separated by about 0.06 eV, the PDI-centred level being the highest one. At 77 K the equilibration is suppressed and the fluorescence of the PDI central core is fully restored, showing that the corresponding level becomes lower-lying than the fullerene singlet. Bimolecular transient absorption studies made on solutions containing F and Per show that triplet energy transfer from the photoexcited fullerene to the PDI occurs. Similar investigations on PerG1–PerG3 only exhibit the features of the PDI triplet, evidencing that this level is populated in a timescale shorter than 10 ns and is the final sink of the above lying excited states. Therefore, in dendrimers PerG1–PerG3, the photophysical behaviour is not dependent on the dendrimer size and structure, and light excitation is followed by inbound energy transfer to the central core and generation of the PDI triplet state.

A novel 2,7-linked carbazole based “double cable” polymer with pendant perylene diimide functional groups: preparation, spectroscopy and photovoltaic properties

The preparation and chemical analysis of a ‘double-cable’ conjugated polymer comprising a backbone of alternating 2,7-linked carbazole repeat units with covalently attached perylene diimide (PDI) substituents and dithienyl repeat units is presented. The backbone of the new “double-cable” polymer P1 acts as an electron donor while the pendant PDI substituents act as electron acceptors. In order to investigate the influence of the PDI moieties on the polymer backbone as well as to elucidate their photophysical interaction, three reference-compounds were also prepared and analysed: a polymer with the same backbone as that of P1 but without PDI substituents (P2) and two PDI derivatives with branched alkyl side chains (PDI 2 with 12-tricosanyl substituents and PDI 1 with 3-pentyl substituents). We find that polymer P1 shows pronounced electron transfer from the polymer backbone to the PDI chromophore units covalently bound to it, resulting in highly efficient quenching of excitons and strong suppression of fluorescence in solutions and in thin films. The existence of long-lived polaronic states resulting from exciton dissociation on P1 is confirmed using steady state photo-induced absorption spectroscopy. Despite the improved exciton quenching yield shown by P1 over a blend of P2/PDI, photovoltaic devices fabricated from P1 have a low external quantum efficiency (EQE) of around 0.43% at 410 nm; a value that is smaller than that from a conventional BHJ device of P2/PDI which is found to have a peak external quantum efficiency of 3.7% at 463 nm. We tentatively ascribe the reduced EQE of the double-cable polymer to geminate recombination of charge-carriers as a result of poor charge transport and a complete lack of donor acceptor phase separation.

Self‐assembled two‐dimensional porous network in aqueous solution based on perylene diimide phenylacetylene oligomer

AbstractTwo‐dimensional porous networks self‐assembled in solution are rare, while maintaining the solution‐phase network structure upon casting on solid supports presents a major challenge. We report on oligoarylacetylene bearing amphiphilic perylene diimide moieties that self‐assemble into a two‐dimensional porous network in aqueous solution that can be cast on surfaces, while maintaining the porous structure. The networks were characterized by cryogenic electron microscopy (cryo‐TEM and cryo‐SEM), and by atomic force microscopy, revealing formation of thin porous films (4‐nm thick). The network can be cast on various solid surfaces, preserving its solution‐phase structure. The design motif utilizing an oligoarylacetylene backbone with interacting amphiphilic pendants appears to be of wide utility for formation of novel assembly patterns. Copyright © 2010 John Wiley & Sons, Ltd.

Multichromophoric Phthalocyanine–(Perylenediimide)8 Molecules: A Photophysical Study

We describe the synthesis of a series of phthalocyanine (Pc)-perylenediimide (PDI)(8) "octad" molecules, in which eight PDI moieties are attached to a Pc core through alkyl-chain linkers. There is clear spectroscopic evidence that these octads can exist as non-aggregated "monomers" or form aggregates along the Pc cores, depending on the type of Pc and the solvent medium. In the low dielectric constant solvents, into which the octads are soluble, photoexcitation of the PDI units leads to rapid energy transfer to the Pc centre, rather than a charge separation between moieties. In octad monomers, the Pc singlet excited-state decays within tens of ps, whereas the excitons are stabilised in the aggregated form of the molecules, typically with lifetimes in the order of 1-10 ns. By contrast, in an octad design in which pi-pi interactions are suppressed by the steric hindrance of a corona of incompatible glycol tails around the molecule, a more straightforward photophysical interaction of Förster energy transfer between the PDI moieties and Pc core may be inferred. We consider these molecules as prototypical multichromophoric aggregates, giving delocalised states with considerable flexibility of design.

Photofunctional Self-Assembled Nanostructures Formed by Perylene Diimide−Gold Nanoparticle Hybrids

We report on the synthesis of organic dye-metal nanoparticle hybrids from two thiol-derivatized perylenediimide (PDI) ligands and 1.5 nm gold nanoparticles. The hybrids form spherical nanostructures when cast from 40% methanol/chloroform solution and toluene. The spherical aggregates are in the size range 50-230 nm in 40% MeOH/CHCl(3) mixture and 100-400 nm in toluene solution, as evidenced by transmission electron microscopy (TEM). Scanning electron microscopy (SEM) measurements show that these spherical aggregates are vesicles with a hollow interior. The π-π interactions of the perylenediimides are the predominant driving force leading to the aggregation of the hybrids, whereby the sizes of the nanospheres can be regulated via the PDI linker moiety and solvent choice. Femtosecond transient absorption studies of the hybrids reveal complex photophysical behavior involving electron transfer from the gold nanoparticles to the PDI moieties. This study shows that the formation of well-defined hybrid nanostructures as well as tuning their sizes can be achieved through employing a combination of the capping ligand choice and regulating the solvophobic interactions between the ligands.

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

AbstractWe 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

Organic donor-σ-acceptor molecules based on 1,2,4,5-tetrakis((E)-2-(5′-hexyl-2,2′-bithiophen-5-yl)vinyl)benzene and perylene diimide derivative and their application to photovoltaic devices

Donor-σ-acceptor molecules of HPBT- n(PDI) ( n = 1, 2, and 4) containing perylene diimide (PDI) and π-extended 1,2,4,5-tetrakis((E)-2-(5′-hexyl-2,2′-bithiophen-5-yl)vinyl)benzene (HPBT) have been successfully synthesized for studying the self-organization of each moiety and their applications in photovoltaic devices. Interesting features were found in these molecules: the aggregation-induced crystallization in the HPBT moieties enhanced the power conversion efficiency (PCE) in the photovoltaic cell. By incorporating HPBT as the donor and PDI as the acceptor moiety, we anticipated that their high degree of independent aggregation-induced crystallization would yield electron/hole transport channels and high mobility in the desired direction of charge transport. In a photovoltaic device, HPBT-1(PDI) gave a PCE of 0.22% with an open circuit voltage ranging from 0.62 to 0.63 V. When the HPBT moiety was more hindered by the PDI moiety, less PCE was observed in HPBT-2(PDI). Addition of methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) resulted in enhancement of the PCE due to enhanced visible absorption. The device bearing HPBT-1(PDI) and PCBM (1:4 mol ratio) demonstrate much higher PCE to be around 1.60%.

Evolution of the Triplet Excited State in PtII Perylenediimides

Here, we present the ultrafast dynamics of a series of metal complexes developed to permit access to the perylenediimide (PDI) triplet manifold that preserves the desirable colorfastness and visible light-absorption properties associated with these dyes. To this end, three Pt(II) complexes each bearing two PDI moieties tethered to the metal center through acetylide linkages emanating from one of the PDI bay positions have been thoroughly examined by static spectroscopic methods, electrochemistry, laser flash photolysis, and ultrafast transient absorption spectrometry. Upon ligation to the Pt(II) center, the bright singlet-state fluorescence (Phi = 0.91, tau = 4.53 ns) of the free PDI-CCH chromophore is quantitatively quenched, and no long wavelength photoluminescence is observed from any of the Pt(II)-PDI complexes in deaerated solutions. Ultrafast transient measurements reveal that upon ligation of PDI-CCH to the Pt(II) center, picosecond intersystem crossing (tau = 2-4 ps) from the (1)PDI excited state is followed by vibrational cooling (tau = 12-19 ps) of the hot (3)PDI excited state, whereas only singlet-state dynamics, including stimulated emission, were observed in the "free" PDI-CCH moiety. In each of the Pt-PDI chromophores, quantitatively similar transient absorption difference spectra were obtained; the only distinguishing characteristic is in their single-exponential lifetimes (tau = 246 ns, 1.0 mus, and 710 ns). These long-lived (3)PDI excited states are clearly poised for bimolecular electron and energy transfer schemes. In the present case, the latter is demonstrated through bimolecular sensitization of singlet oxygen phosphorescence at approximately 1270 nm in aerated dichloromethane solutions, producing reasonable (1)O(2) quantum yields (Phi(Delta) = 0.40-0.55) across this series of molecules.

Copolymers of perylene diimide with dithienothiophene and dithienopyrrole as electron-transport materials for all-polymer solar cells and field-effect transistors

Electron-accepting solution-processable conjugated polymers consisting of perylene diimide moieties alternating with dithienothiophene, oligo(dithienothiophene), or N-dodecyl dithienopyrrole units have been synthesized. All these polymers possess excellent thermal stability with decomposition temperatures over 400 °C. The glass-transition temperatures vary from 155 to 263 °C. These polymers show broad absorption extending from 250 to 900 nm with electrochemical and optical bandgaps as low as 1.4 eV; the maximum absorbance increases and the bandgap decreases with increasing the conjugation length of oligo(dithienothiophene), while the bandgap can also be decreased by the replacement of dithienothiophene by dithienopyrrole. The electrochemical onset reduction potentials range from −0.8 to −1.0 V vs. ferrocenium/ferrocene, suggesting that the electron affinities are essentially unaffected by the specific choice of donor moiety, while the onset oxidation potentials (+0.6 to +1.0 V) are a little more sensitive to the choice of donor. The mono dithienothiophene and the dithienopyrrole polymers were found to exhibit electron mobilities as high as 1.3 × 10−2 and 1.2 × 10−3 cm2V−1s−1, respectively, in top-contact organic field-effect transistors. Power conversion efficiencies in the range 0.77–1.1% were obtained under simulated AM 1.5, 100 mW/cm2 irradiation for all-polymer solar cells using the dithienothiophene-based polymers as acceptors in a 1 : 1 ratio with a polythiophene derivative as a donor. The device performance varies with the conjugation length of oligo(dithienothiophene) in the polymer acceptors, and for the best-performing material it can be further optimized to give a power conversion efficiency of 1.5% by increasing the donor/acceptor weight ratio to 3 : 1.

Triplet Formation Involving a Polar Transition State in a Well-Defined Intramolecular Perylenediimide Dimeric Aggregate

A cofacially stacked perylenediimide (PDI) dimer with a xanthene linker was studied under a variety of conditions (solvent, temperature) and serves as a model for the molecular interactions occurring in solid films. Intrinsically, the PDI units have a fluorescence quantum yield (Phi F) close to unity, but Phi F is lowered by a factor of 6-50 at room temperature when two PDI moieties are held in a cofacial arrangement, while the decay time of the most emissive state is increased significantly (tau F = 27 ns in toluene) compared to a monomeric PDI molecule (tau F = 4 ns). Fluorescence measurements show a strong solvent and temperature dependence of the characteristics of the emissive excited state. In a glassy matrix of toluene (TOL) or 2-methyltetrahydrofuran (2-MeTHF), Phi F is high, and the decay time is long (tau F = approximately 50 ns). At higher temperature, both Phi F and tau F are reduced. Interestingly, at room temperature, Phi F and tau F are also reduced with increasing solvent polarity, revealing the presence of a polar transition state. Photoinduced absorption of the stacked molecules from the picosecond to the microsecond time scale shows that after photoexcitation reorganization occurs in the first nanoseconds, followed by intersystem crossing (ISC), producing the triplet excited state. Using singlet oxygen ( (1)Delta g) luminescence as a probe, a triplet quantum yield (Phi T) greater than 50% was obtained in air-saturated 2-Me-THF. Triplet formation is exceptional for PDI chromophores, and the enhanced ISC is explained by a decay involving a highly polar transition state.

Large Reorganization Energy of Pyrrolidine-Substituted Perylenediimide in Electron Transfer

Excited-state dynamics of an electron-donating, pyrrolidine-substituted perylenediimide-C60 linked dyad have been investigated by means of time-resolved transient absorption spectroscopy and fluorescence lifetime measurements. By the picosecond transient absorption measurements at a selective excitation of the perylenediimide moiety, a charge-separated state has been successfully detected in polar solvents (i.e., benzonitrile, pyridine, and o-dichlorobenzene), demonstrating the occurrence of photoinduced electron transfer from the perylenediimide to the C60 moiety. In contrast, in nonpolar solvents (i.e., toluene), singlet−singlet energy transfer takes place from the perylenediimide to the C60, followed by intersystem crossing to the C60 excited triplet state and subsequent triplet−triplet energy transfer to yield the perylenediimide excited triplet state. Rate constants of the charge recombination in the polar solvents are found to be comparable to or even larger than those of the charge separation, which is in sharp contrast with electron transfer behavior in typical donor-C60 linked systems. A reorganization energy (0.86 eV) of the perylenediimide-C60 linked dyad obtained in the polar solvents is significantly larger than those of similar porphyrin-C60 linked dyads (0.51−0.66 eV) in which both have comparable edge-to-edge distances between donor and acceptor. The large reorganization energy of the perylenediimide-C60 linked dyad relative to the porphyrin-C60 linked dyads results from a relatively large conformational change in the pyrrolidine groups at the perylenediimide moiety accompanied by one-electron oxidation. This agrees with the fact that charge recombination to the ground state rather than the excited triplet state of the perylenediimide moiety is predominant in benzonitrile, irrespective of the lower energy level of the excited triplet state than that of the charge-separated state.

Energy and Electron Transfer in a Poly(fluorene-alt-phenylene) Bearing Perylenediimides as Pendant Electron Acceptor Groups

We describe the synthesis and characterization of a novel poly(fluorene-alt-phenylene) substituted with perylenediimide (PDI) moieties as pendant groups. Cyclic voltammetry experiments show the amphoteric nature of the material, which combines the good electron donor ability of the polymeric chain with the acceptor properties of the pendant PDI moieties. Absorption spectroscopy suggests the presence of PDI aggregates, whereas the emission spectra show a strong emission quenching of both the polymeric backbone and the PDI units. Further investigation on the energy and/or electron-transfer processes involved is carried out by temperature-dependent excitation spectra and photoluminescence lifetimes. These studies show the presence of electron transfer not only from the electron donor polymeric chain to the pendant PDI units but also, and more remarkably, to PDI aggregates both in solution and in solid state, as is further confirmed by photoinduced absorption spectroscopy.

Self-Assembled Fluorescent Hexaazatriphenylenes That Act as a Light-Harvesting Antenna

In this paper we report the self-assembling nature of fluorescent hexaazatriphenylenes (HATs) 6a-d with six alkyl/alkoxy-chain-containing biphenyl groups and their application to light-harvesting antennae. In a nonpolar solvent and the film state, the HAT derivatives form one-dimensional aggregates with an H-type parallel stacking mode, which were analyzed by 1H NMR, UV-vis, and steady-state and time-resolved fluorescence spectroscopy. When HAT derivative 7 with six perylenediimide moieties is incorporated into the one-dimensional aggregates, an efficient energy transfer takes place from the self-assembled HAT moiety as a light-harvesting antenna to the perylenediimide moiety as an energy acceptor. Further, when HAT derivative 8 with six triphenylamino moieties is newly added to the light-harvesting system, an intermolecular electron transfer occurs subsequently between the electron-accepting perylenediimide molecule and the electron-donating triphenylamino molecule.

Synthesis and Characterization of Long Perylenediimide Polymer Fibers: From Bulk to the Single-Molecule Level

The synthesis and characterization of perylenediimide polyisocyanides is reported. In addition to short oligomers, our synthetic approach results in the formation of extremely long, well-defined, and rigid perylenediimide polymers. Ordering and close-packing of the chromophores in these long polymers is guaranteed by attachment to a polyisocyanide backbone with amino acid side chains. Hydrogen bonding interactions between those groups stabilize and rigidify the helical polymer structure. The rodlike nature of the synthesized long perylenediimide pendant polyisocyanides as well as the helical arrangement of the chromophores is demonstrated by means of atomic force microscopy. Remarkably, polymer fibers up to 1 mum in length have been visualized, containing several thousands of perylenediimide molecules. Circular dichroism spectroscopy reveals the chiral organization of the chromophore units in the polymer, whereas absorption and emission measurements prove the occurrence of excited-state interactions between those moieties due to the close packing of the chromophore groups. However, an intricate optical behavior is encountered in bulk as a result of the coexistence of short oligomers and long polymers of perylenediimide, a situation subsequently uncovered by means of single-molecule experiments. Individual long helical perylenediimide polyisocyanides exhibit a typical red-shifted fluorescence spectrum, which, together with depolarized emission continuously decreasing in time, demonstrate that fluorescence arises from multiple excimer-like species in the polymer. Upon continuous irradiation of these long polymers, a fast decay in fluorescence lifetime is observed, a situation explained by photoinduced creation of quenching sites. Radical/ion formation by intramolecular electron transfer between close-by perylenediimide moieties is the most probable mechanism for this process. Appropriate control of the electron-transfer process might open the possibility of applying these polymers as perylenediimide-based supramolecular nanowires.

Light-Harvesting and Energy-Transfer System Based on Self-Assembling Perylene Diimide-Appended Hexaazatriphenylene

[reaction: see text]. Six perylene diimide-appended hexaazatriphenylene, HAT-PDI(6), was self-assembled in both solution and film state to form a highly stabilized dimer aggregate, in which an efficient energy transfer occurs from the hexaazatriphenylene core to the perylene-diimide moiety.