A panchromatic 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene –zinc phthalocyanine conjugate (Bodipy–ZnPc) 1 was synthesized starting from phthalocyanine aldehyde 4, via dipyrromethane 3 and ...dipyrromethene 2. Conjugate 1 represents the first example in which a Bodipy unit is tethered to the peripheral position of a phthalocyanine core. Electrochemical and optical measurements provided evidence for strong electronic interactions between the Bodipy and ZnPc constituents in the ground state of 1. When conjugate 1 is subjected to photoexcitation in the spectral region corresponding to the Bodipy absorption, the strong fluorescence characteristic of the latter subunit is effectively quenched (i.e., ≥97 %). Excitation spectral analysis confirmed that the photoexcited Bodipy and the tethered ZnPc subunits interact and that intraconjugate singlet energy transfer occurs with an efficiency of ca. 25 %. Treatment of conjugate 1 with N‐pyridylfulleropyrrolidine (8), an electron‐acceptor system containing a nitrogen ligand, gives rise to the novel electron donor–acceptor hybrid 1↔8 through ligation to the ZnPc center. Irradiation of the resulting supramolecular ensemble within the visible range leads to a charge‐separated Bodipy–ZnPc.+–C60.− radical‐ion‐pair state, through a sequence of excited‐state and charge transfers, characterized by a remarkably long lifetime of 39.9 ns in toluene.
Long live the hybrid! The synthesis and photophysical properties of a peripherally substituted Bodipy–zinc phthalocyanine dyad that absorbs over much of the visible spectral region are described. Axial coordination of a C60 derivative at phthalocyanine affords an electron donor–acceptor hybrid that, upon photoexcitation, undergoes a sequence of energy‐ and electron‐transfer reactions (see figure).
A thorough investigation on the physicochemical properties, including electrochemisty and photophysics, of a new class of donor−acceptor hybrids, namely, phthalocyanine-fullerene dyads, consisting of ...free base 1a and zinc and copper complexes 1b and 1c, respectively, brings new insights into the stabilization of charge-separated radical ion pairs and the impact of redoxactive transition-metal centers on the photoperformance of macrocyclic phthalocyanines. In these dyads, the role of the phthalocyanines is twofold: First, it functions as an antenna (i.e., absorbing very efficiently light in the visible region of the solar spectrum) and, second, as a donor moleculeonce photoexcited. The initial photoexcitation is succeeded by an ultrafast electron transfer largely due to the strong electronic coupling between electron donor (Pc) and electron acceptor (C60) generating surprisingly long-lived radical ion pairs Pc•+−C60 •- with lifetimes of several nanoseconds. Large driving forces for the charge recombination and small reorganization energies of the Pc−C60 ensembles corroborate slow charge recombination dynamics, which, in turn, helps to rationalize the long lifetimes of Pc•+−C60 •-.
Induction of self-organization between zinc phthalocyanine (ZnPc) and C60 moieties in a novel amphiphilic ZnPc−C60 salt results in uniformly nanostructured 1-D nanotubules. Their photoreactivity, in ...terms of ultrafast charge separation (i.e., ∼1012 s-1) and ultraslow charge recombination (i.e., ∼103 s-1), is remarkable. In addition, the observed ZnPc•+−C60 •- lifetime of 1.4 ms implies, relative to that of the monomeric ZnPc−C60 (∼3 ns), an impressive stabilization of 6 orders of magnitude.
A novel porphyrin-fullerene dyad assembled through Watson-Crick hydrogen bonds is described; this system undergoes photoinduced electron transfer upon irradiation with visible light to produce a ...charge separated state that is substantially longer lived than that of previous dyads of this type.
A new non-covalent electron transfer model system, based on the use of cytidine-guanosine hydrogen bonding interactions, is described that incorporates a phthalocyanine photodonor and a C60 fullerene ...acceptor.
We have prepared three isomeric donor−acceptor systems, in which two phthalocyanine (Pc) units have been attached to the 1-,5- (1a), 1-,8- (1b), or 2-,6- (1c) positions of a central anthraquinone ...(AQ) moiety, leading to packed (1b) or extended (1a and 1c) topologies. The electronic interactions between the donor and the acceptor in the ground state or in the excited states have been studied by different electrochemical and photophysical techniques. Due to the markedly different topologies, we have been able to modify these interactions at the intramolecular level and, by a proper choice of the solvent environment, at the intermolecular level within aggregates. In triad 1b, the ZnPc units are forced to π-stack cofacially and out of the plane of the AQ ring. Consequently, this molecule shows strong inter-Pc interactions that give rise to intramolecular excitonic coupling but a relatively small electronic communication with the AQ acceptor through the vinyl spacers. On the contrary, the 1-,5- or 2-,6-connections of triads 1a and 1c allow for an efficient π-conjugation between the active units that extends over the entire planar system. These two molecules tend to aggregate in aromatic solvents by π−π stacking, giving rise to J-type oligomers. Photoexcitation of the Pc units of 1a − c results in the formation of the Pc•+−AQ•- charge transfer state. We have demonstrated that the kinetics of these electron transfer reactions is greatly dependent on the aggregation status of the triads.
The synthesis and photophysical properties of several fullerene–phthalocyanine–porphyrin triads (1–3) and pentads (4–6) are described. The three photoactive moieties were covalently connected in an ...one‐step synthesis through 1,3‐dipolar cycloaddition to C60 of the corresponding azomethine ylides generated in situ by condensation reaction of a substituted N‐porphyrinylmethylglycine derivative and an appropriated formyl phthalocyanine or a diformyl phthalocyanine derivative, respectively. ZnP‐C60‐ZnPc (3), (ZnP)2‐ZnPc‐(C60)2 (6), and (H2P)2‐ZnPc‐(C60)2 (5) give rise upon excitation of their ZnP or H2P components to a sequence of energy and charge‐transfer reactions with, however, fundamentally different outcomes. With (ZnP)2‐ZnPc‐(C60)2 (6) the major pathway is an highly exothermic charge transfer to afford (ZnP)(ZnP.+)‐ZnPc‐(C60.−)(C60). The lower singlet excited state energy of H2P (i.e., ca. 0.2 eV) and likewise its more anodic oxidation (i.e., ca. 0.2 V) renders the direct charge transfer in (H2P)2‐ZnPc‐(C60)2 (5) not competitive. Instead, a transduction of singlet excited state energy prevails to form the ZnPc singlet excited state. This triggers then an intramolecular charge transfer reaction to form exclusively (H2P)2‐ZnPc.+‐(C60.−)(C60). A similar sequence is found for ZnP‐C60‐ZnPc (3).
Photoactive fullerenes: Several fullerene–phthalocyanine–porphyrin triads and pentads, covalently connected, give rise upon excitation of their porphyrin components to a sequence of energy and charge‐transfer reactions.
The synthesis of a new series of electron donor−acceptor conjugates (5, 10, 13, and 16) in which the electron acceptorC60and the electron donorπ-extended tetrathiafulvalene (exTTF)are bridged by ...means of m-phenyleneethynylene spacers of variable length is reported. The unexpected self-association of these hybrids was first detected to occur in the gas phase by means of MALDI-TOF spectrometry and subsequently corroborated in solution by utilizing concentration-dependent and variable-temperature 1H NMR experiments. Furthermore, the ability of these new conjugates to form wirelike structures upon deposition onto a mica surface has been demonstrated by AFM spectroscopy. In light of their photoactivity and redoxactivity, 5, 10, 13, and 16 were probed in concentration-dependent photophysical experiments. Importantly, absorption and fluorescence revealed subtle dissimilarities for the association constants, that is, a dependence on the length of the m-phenylene spacers. The binding strength is in 5 greatly reduced when compared with those in 10, 13, and 16. Not only that, the spacer length also plays a decisive role in governing excited-state interactions in the corresponding electron donor−acceptor conjugates (5, 10, 13, and 16). To this end, 5, in which the photo- and electroactive constituents are bridged by just one aromatic ring, displaysexclusively and independent of the concentration (10−6 to 10−4 M)efficient intramolecular electron transfer events on the basis of a “through-bond” mechanism. On the contrary, the lack of conjugation throughout the bridges in 10 (two m-phenyleneethynylene rings), 13 (three m-phenyleneethynylene rings), and 16 (four m-phenyleneethynylene rings) favors at low concentration (10−6 M) “through space” intramolecular electron transfer events. These are, however, quite ineffective and, in turn, lead to excited-state deactivations that are at high concentrations (10−4 M) dominated by intracomplex electron transfer events, namely, between exTTF of one molecule and C60 of another molecule, and that stabilize the resulting radical ion pair state with lifetimes reaching 4.0 μs.
A novel covalently linked bis(60fullerene)−phthalocyanine triad is reported, exhibiting long-lived photoinduced charge separation both in solution and in the solid state. The first demonstration of a ...working solar cell using triad 1 as the active material is also presented.
Phthalocyanines linked to C60 have been synthesized by two general strategies. One of them involves the addition of an azomethine ylide prepared in situ from a formyl phthalocyanine to C60, and the ...other one involves a statistical condensation of two substituted phthalonitriles, one of them bearing the C60 moiety covalently attached. These new phthalocyanine‐fullerene dyads have been studied by cyclic voltammetry and Osteryoung square wave voltammetry, and inter‐ and intramolecular electronic interactions between the two electroactive subunits have been demonstrated.
Se han sintetizado ftalocianinas unidas a C60 siguiendo dos estrategias generales. Una de ellas implica la adición de un iluro de azometino preparado in situ a partir de la correspondiente formilftalocianina, y la otra utiliza la condensación estadística de dos ftalonitrilos sustituidos, uno de los cuales está unido covalentemente a la unidad de C60. Estas nuevas diadas de ftalocianina‐fullereno se han estudiado por voltametría cíclica y voltametría de onda cuadrada de Osteryoung, habiéndose puesto de manifiesto la existencia entre ambas subunidades electroactivas de interacciones electrónicas, inter‐ e intramoleculares.
