Porphyrin-fullerene Dyad Research Articles

Photoinduced Electron Transfer in a Porphyrin-Fullerene Dyad at a Liquid Interface.

The excited-state properties of an amphiphilic porphyrin-fullerene dyad and of its porphyrin analogue adsorbed at the dodecane/water interface are investigated by using surface second-harmonic generation. Although the porphyrin is formally centrosymmetric, the second-harmonic spectra of both compounds are dominated by the intense Soret band of the porphyrin. Polarization-selective measurements and molecular dynamics simulations suggest an angle of about 45° between the donor-acceptor axis and the interfacial plane, with the porphyrin interacting mostly with the nonpolar phase. Time-resolved measurements reveal a marked concentration dependence of the dynamics of both compounds upon Q-band excitation, indicating the occurrence of intermolecular quenching processes. The significant differences in dynamics and spectra between the dyad and the porphyrin analogue are explained by a self-quenching of the excited dyad via an intermolecular electron transfer.

Advanced Nonvolatile Organic Optical Memory Using Self-Assembled Monolayers of Porphyrin-Fullerene Dyads.

Photo-switchable organic field-effect transistors (OFETs) represent an important platform for designing memory devices for a diverse array of products including security (brand-protection, copy-protection, keyless entry, etc.), credit cards, tickets, and multiple wearable organic electronics applications. Herein, we present a new concept by introducing self-assembled monolayers of donor–acceptor porphyrin–fullerene dyads as light-responsive triggers modulating the electrical characteristics of OFETs and thus pave the way to the development of advanced nonvolatile optical memory. The devices demonstrated wide memory windows, high programming speeds, and long retention times. Furthermore, we show a remarkable effect of the orientation of the fullerene–polymer dyads at the dielectric/semiconductor interface on the device behavior. In particular, the dyads anchored to the dielectric by the porphyrin part induced a reversible photoelectrical switching of OFETs, which is characteristic of flash memory elements. On the contrary, the devices utilizing the dyad anchored by the fullerene moiety demonstrated irreversible switching, thus operating as read-only memory (ROM). A mechanism explaining this behavior is proposed using theoretical DFT calculations. The results suggest the possibility of revisiting hundreds of known donor–acceptor dyads designed previously for artificial photosynthesis or other purposes as versatile optical triggers in advanced OFET-based multibit memory devices for emerging electronic applications.

Donor-π-Acceptor Type Porphyrin-Fullerene Dyad with Acetylene Bridge for p-Type Dye-sensitized Solar Cell

Abstract Donor-π-acceptor type porphyrin-fullerene dyads with an acetylene bridge were designed and synthesized. The dyad was found to produce a charge-separated state with a lifetime of 0.42 µs and a quantum yield of 0.78 in benzonitrile. The p-type dye-sensitized solar cells with the dyad exhibited higher photovoltaic performance than that with the porphyrin reference without the fullerene moiety.

Peculiar Properties of Charge Transfer in a Multilayered Film Structure upon Selective Pulsed Photoexcitation

Vectorial charge transfer upon pulsed laser excitation in three-layer Langmuir–Schafer structures consisting of 100% photoactive molecules of porphyrin-fullerene dyad, phthalocyanine and polythiophene was studied. The behavior of the photovoltaic responses of the structures changed significantly upon selective optical excitation of monolayers. The mechanisms of the vectorial charge transfer in samples depending on the individual components photoexcitation of the structure are discussed.

Switching Competition between Electron and Energy Transfers in Porphyrin-Fullerene Dyads.

Porphyrin-fullerene dyads were intensively studied as molecular donor-acceptor systems providing efficient photoinduced charge separation (CS). A practical advantage of the dyads is the possibility to tune its CS process by the porphyrin periphery modification, which allows one to optimize the dyad for particular applications. However, this tuning process is typically composed of a series of trial stages involving the development of complex synthetic schemes. To address the issue, we synthesized a series of dyads with properties switching between electron and energy transfer in both polar (benzonitrile) and nonpolar (toluene) media and developed a computation procedure with sufficient reliability by which we can predict the CS properties of the dyad in different media and design new dyads. The dyads photochemistry was established by conducting ultrafast transient absorption studies in toluene, anisole, and benzonitrile. The most crucial step in computational modeling was to establish a procedure for correction of the electronic-state energies obtained by DFT so that the effects of the electron correlation and the long-range interactions are properly incorporated. We also carried out standard electrochemical measurements and show that our computation approach predicts better thermodynamics of the dyads in different solvents.

Comparative Charge Transfer Studies of Porphyrin-Fullerene Dyads: Substituents Effect.

The present study deals with the study of charge transfer and photophysical properties of synthesized non-metallated fullerene-porphyrin dyad-III (H2P3-C60) via Prato reaction. The porphyrin has been substituted with electron donating groups (3,5-di-tert-butylbenzene) at meso positions facilitating the effective charge transfer for the formation of long lived charge-separated states in dyad molecule. The photophysical and thermal activated conducting properties of dyad was comprehensively studied to establish the effect of substituents and also by comparing with our reported dyad II having only meso-phenyl groups. The charge separation efficiency in dyad III has been calculated in solution as well as in films showing 62% and ˜99% quenching efficiency respectively suggesting faster photoinduced charge transfer from porphyrin to fullerene moiety. Transient absorption spectroscopy (TAS) showed formation of longer lived charge separated states in solution as well as in films compared to dyad-II. The thermal activated electrical conductivity measurement of dyad-III showed conductivity enhancement on increasing temperature. The activation energy for conduction was also found lower than dyad-II suggesting a substantial effect of electron-donating groups present on porphyrin ring in conducting behavior of dyad-III. Through this study with a very simple dyad structure we established that the presence of electron donating groups in dayds, highly influence photophysical and electronic properties. This special characteristic further makes them potential material to be used in various opto-electronic applications.

Electron transfer in oriented donor-acceptor dyads, intralayer charge migration, and formation of interlayer charge separated states in multi-layered Langmuir-Schäfer films.

Photoinduced intra- and interlayer electron transfer (ET) of doubly bridged donor-acceptor molecule, porphyrin-fullerene dyad (PF), was studied in single- and multi-layered Langmuir-Schäfer (LS) films and in LS films, where PF and an efficient electron donating polymer polyhexyltiophene (PHT) formed a bilayer PHT/PF and multi-layered PHT/PF structures. The ET through layers were investigated by a method, which measures the photovoltaic (PV) response proportional to the number of charge-separated (CS) states and to the CS distance between the electrons and holes formed in pulsed photo-excitation. Primary conclusions were, that ET starts as formations of CS dyads (P+F-) in single-layers, continues as long-range intra-layer charge migrations following interlayer CS between two adjacent monolayers. Quantitative conclusions were, that the interlayer ET efficiency is 100% in the bi-layered PF structure (2PF), where two CS dyads in adjacent layers forms CS complexes (P+F/PF-) and that the probability to form longer or higher order of CS complexes follows an expression of a convergent geometric series, with a converting factor of 2/3. In the PHT/PF bilayer structure the ET efficiency was one order of magnitude higher, than that for the 2PF structure due to the ET from the CS dyads to ground state electron donor PHT, with an acceptor density, much higher than that of (P+F-).

Exclusive triplet electron transfer leading to long-lived radical ion-pair formation in an electron rich platinum porphyrin covalently linked to fullerene dyad.

The formation of a high-energy, long-lived radical ion-pair by electron transfer exclusively from the triplet excited state, is demonstrated in a newly synthesized platinum porphyrin-fullerene dyad, in which the porphyrin ring is modified with three electron rich triphenylamine entities. The spin selectivity of the electron transfer leading to the formation of the radical ion-pair is demonstrated using time-resolved optical and EPR spectroscopic techniques.

Porphyrin-fullerene dyads –synthesis and redox/photophysical properties

Three free base porphyrin-fullerene dyads of C60-PH2R and their zinc complexes C60-PZnR were synthesized. They were fully characterized by mass spectrometry, nuclear magnetic resonance, infrared spectroscopy, and ultraviolet-visible spectroscopy. Studies on steady-state fluorescence spectroscopy and cyclic voltammetry show that the coordination of the porphyrin moiety with zinc ions leads to an increases in the singlet excited state energies, and decreases in both the HOMO level and the HOMO-LUMO gap. The introduction of the electron-donating groups of -Me or -OMe to the porphyrin core leads to a negative shift in the first oxidation potential, and a further decrease in the HOMO level. Calculation Results show that the coordination of zinc ions lead to a greatly increase in the photoinduced electron transfer constants ket and substituents of the porphyrin core also effect on ket value.

Synthesis, Structural, Spectral and Electrochemical Redox Properties of N-Fused Porphyrins and Their Photoinduced Electron Transfer Studies with C60 Derivatives

Porphyrins exhibit the variation in physicochemical properties according to the substitution at β/meso-positions of the macrocyclic ring which makes them a suitable candidate for various applications [1]. Non-covalent interactions play a significant role in execution of various building blocks which can be used for the inception and implementation of advanced functional materials including various porphyrin-fullerene donor-acceptor dyads [2]. Herein, we have synthesized a new series of β-substituted N-fused porphyrins (MTPP(N-fusedPh)X2, X = H, Br, Ph and PE, M = 2H, Co(II), Ni(II), Cu(II), and Zn(II)) (Figure 1) as donors in order to coordinate with C60 derivatives to form supramolecular dyads. Notably, these porphyrins exhibit very low oxidation potential due to intramolecular charge-transfer from β-arylamine group to porphyrin core. Efficient fluorescent quenching was observed for Zn(II) fused porphyrins while titrating with C60 derivatives due to axial coordination of C60Im to Zn(II) porphyrins. The quenching constants were found in the range of 104-105 M-1 which revealed the stable donor-acceptor dyads formation. The first oxidation potential of supramolecular dyads are anodically shifted (~100 mV) as compared to ZnTPP(N-fusedPh)X2. Photoinduced electron transfer (PET) studies of dyad containing Zn(II) N-fused porphyrin-imidazole appended C60 have been carried out. In this presentation, we will describe about the synthesis, structural, spectral and electrochemical redox properties of N-fused porphyrins and their photoinduced electron transfer studies with various C60 derivatives. Figure 1. (a) Structure of ZnTPP(N-fusedPh)X2 coordinated with C60Im (b) Fluorescence titration of ZnTPP(N-fusedPh)PE2 (4d) with C60Im (c) Cyclic voltammograms of ZnTPP(N-fusedPh)PE2 (4d) in presence and absence of C60Im. REFERENCES (a) Tanaka, T.; Osuka, A. Chem. Soc. Rev., 2015, 44, 943. (b) Wang, L.; Long, S.; Meng, Li, X.; Zhao, W.; Song, Y.; Cifuentes, M. P.; Humphrey, M. G.; Zhang, C. Org. Biomol. Chem. 2013, 11, 4250. (c) Kumar. R.; Sankar, M. Inorg. Chem. 2014, 53, 12706. (d) Grover, N.; Sankar, M.; Song, Y.; Kadish, K. M. Inorg. Chem. 2016, 55, 584. (e) Chaudhri, N.; Grover, N.; Sankar, M. Inorg. Chem. 2017, 56, 424. (f) Ke, X.; Yadav, P.; Cong, L.; Kumar, R.; Sankar, M; Kadish, K. M. Inorg. Chem. 2017, 56, 8527. (g) Chaudhri, N.; Grover, N.; Sankar, M. Inorg. Chem. 2017, 56, 11532. (h) Ke, X.; Kumar, R.; Sankar, M; Kadish, K. M. Inorg. Chem. 2018, 57, 1490. (i) Chaudhri, N.; Grover, N.; Sankar, M. Inorg. Chem. 2018, 57, 6658. (j) Chaudhri, N.; Grover, N.; Sankar, M. Inorg. Chem. 2018, 57, 11349. (k) Chaudhri, N.; Cong, L.; Grover, N.; Shan, W.; Anshul, K.; Sankar, M.; Kadish, K. M. Inorg. Chem. 2018, 57, 13213. (l) Grover, N.; Chaudhri, N.; Sankar, M. Inorg. Chem. 2019 (in press).(a) Fukuzumi S. Functional Organic Materials, Wiley-VCH: Weinheim, 2007 , (b) Follana-Berna, J.; Seetharaman, S.; Martın-Gomis, L.; Charalambidis, G.; Trapali, A.; Karr, P. A.; Coutsolelos, A. G.; Fernandez-Lazaro, F.; D’Souza, F.; Sastre-Santos, A. Phys. Chem. Chem. Phys., 2018, 20, 7798. Figure 1

Synthesis, spectral and redox properties of closely spaced pyrrole-β-position-linked porphyrin-fullerene dyads

Two free base meso-tetraphenylporphyrin-fullerene dyads, H2PMe-C60, H2POMe-C60, and their zinc complexes, ZnPMe-C60 and ZnPOMe-C60, which the para positions of the meso-tetrasubstituted phenyl groups of the porphyrin core were substituted by methyl(-Me) and methoxyl(-OMe) groups respectively, were synthesized. The porphyrin unit in the synthesized dyads is directly linked to the fullerene entity through the pyrrole-β- position rather than through the traditionally meso-substituted phenyl group, which may be more favorable for electron communication between the donor and the acceptor. They are fully characterized by mass spectrometry, nuclear magnetic resonance, infrared spectroscopy and ultraviolet visible spectroscopy. Experimental results obtained from steady-state fluorescence spectroscopy and cyclic voltammetry show that the coordination of the zinc ions lead to an increase in the singlet excited state energy of the metallated porphyrin unit by about 0.15 eV, and to a reduce in the HOMO level and in the HOMO-LUMO energy gap. The molecular reorganization energy decreases after the electron-donating groups of -Me or -OMe attaching to the para position of the meso-phenyl group of the porphyrin moiety. The results of the energy calculations show that photoinduced electron transfer is thermodynamically favorable for the synthesized porphyrin-C60 dyads. There exists a competition between the photoinduced electron transfer and energy transfer processes from the first singlet excited state of porphyrin core to fullerene moiety. The photoinduced electron transfer rate constant of the dyads were calculated according to Marcus theory. The results indicate that the coordination of metal zinc ions lead to great increase in the electron transfer rate constant. Further, the photoinduced electron transfer rate constant increases in the order ZnP-C60, ZnPMe-C60, ZnPOMe-C60.

Photogalvanic eff ect in porphyrin-pyrrolo[3′,4′:1,9]-(C60-Ih)[5,6]fullerene-2′,5′-dicarboxylate systems

The influence of molecular structural factors of covalently bound porphyrin-fullerene dyads and porphyrin—fullerene binary mixtures on photocurrent in model photoelectrochemical cells was studied. It was found that the photocurrent increased either by introducing solubilizing alkyl groups into the donor (porphyrin) or acceptor (fullerene) fragments, or by covalent binding porphyrin and fullerene into a donor-acceptor dyad.

Peculiar Photoinduced Electron Transfer in Porphyrin-Fullerene Akamptisomers.

Porphyrin-fullerene dyads are promising candidates for organic photovoltaic devices. The electron-transfer (ET) properties of the molecular devices depend significantly on the mutual position of the donor and acceptor. Recently, a new type of molecular isomerism (akamptisomerism) has been discovered. In the present study, we explore how photoinduced ET can be modulated by passing from one akamptisomer to another. To this aim, four akamptisomers of the quinoxalinoporphyrin-[60]fullerene complex are selected for computational study. The most striking finding is that, depending on the isomer, the porphyrin unit in the dyad can act as either electron donor or electron acceptor. Thus, the stereoisomeric diversity allows one to change the direction of ET between the porphyrin and fullerene moieties. To understand the effect of akamptisomerism on the photoinduced ET processes, a detailed analysis of initial and final states involved in the ET is performed. The computed rate for charge separation is estimated to be in the region of 1-10 ns-1 . The formation of a long-living quinoxalinoporphyrin anion radical species is predicted.

The electronic structures and excitation properties of three meso-pentafluorophenyl substituted zinc porphyrin–fullerene dyad

Understanding electronic structures and excitation properties is a fundamental issue to develop novel electron donor (D) and acceptor (A) molecular dyad that can be applied in optoelectronic systems. Here, the geometry, electronic structures, and excitation properties of three meso-pentafluorophenyl substituted zinc porphyrin fullerene ((F15P)ZnPC60) dyad were analyzed based on density functional theory (DFT) and time dependent DFT (TDDFT) calculations. The geometrical parameters provide the D-A distance is about 18.19 Å. The electronic structure analysis indicates that the highest occupied molecular orbital and the lowest unoccupied molecular orbital are localized in porphyrin core and C60, respectively. The transition configurations and the MOs suggest the excited states at the absorption maxima are local excited states, while the charge transfer (CT) states are transient intermediates. The population analysis supports the first singlet/triplet excited states are local excitations in porphyrin (LEP). Quasi-degeneracy of excited states between LEP and local excitation in C60 (LEC) enable the partial delocalization of eigenstates and excitation-energies over the D and A in dyad, while the quasi-degeneracy between CT and LEP generate synergistic enhancement effects for CT. The results of this work could be helpful to understand optoelectronic properties of (F15P)ZnPC60 dyad.

Triaryl-substituted pyrrolo-p-phenylene-linked porphyrin-fullerene dyads: Expanding the structural diversity of photoactive materials

A protocol for the synthesis of pyrrolo-p-phenylene-linked porphyrin-fullerene dyads suitable as photoactive materials was developed. The sequence of aziridination – aziridine ring opening – 1,3-dipolar cycloaddition reactions enabled us to provide structural variability both to the porphyrin core and to pyrrole linker, which facilitates designing the electronic structure and morphological parameters of the dyads. The key porphyrin building blocks, nitro-porphyrins, were synthesized by a stochastic cyclocondensation of arenecarbaldehydes with p-nitrophenyl(dipyrrolyl)methane.

Porphyrin–Fullerene Dyad Based on Indium(III) Complex. Donor–Acceptor Complex Formation Equilibrium

Formation kinetics and spectral properties of the donor–acceptor complexes of (5,10,15,20- tetra(2-methoxyphenyl)porphinato)chloroindium(III) with 2′-(pyridin-4-yl)-5′-(pyridin-2-yl)-1′-(pyridin- 2-yl)methylpyrrolidinyl[3′,4′:1,2][60]fullerene were studied. The formation of the donor–acceptor dyad [(Py3F)InTPP(2-OCH3)4]+Cl– occurs as a two-step reaction, including fast reversible coordination of the fullerene base molecule and slow irreversible displacement of the axial chloride ion to the second coordination sphere. Quantitative characteristics for the reaction rate and equilibrium were obtained. The reaction products were identified by IR and 1H NMR spectroscopy. The most important electron optical and stability parameters of the porphyrin–fullerene dyads with inner- and outer-sphere chloride ions were determined. These results are important for studies of the photophysics of porphyrin–fullerene dyads and development of photoconverters based on them.

Charge Stabilization in High-Potential Zinc Porphyrin-Fullerene via Axial Ligation of Tetrathiafulvalene

Extending the lifetime of the charge-separated states generated during photoinduced electron transfer in a covalently linked high-potential zinc porphyrin-fullerene dyad, (F15P)Zn–C60, was accomplished by metal–ligand axial coordination of pyridine-functionalized tetrathiafulvalene (TTF) via a dual-electron-transfer/hole migration mechanism. The meso-aryl positions of the zinc porphyrin carried three penta-fluorophenyl substituents that made the zinc porphyrin ring harder to oxidize by 0.43 V compared with zinc porphyrin with meso-phenyl substituents. Two TTF derivatives, a first with a pyridine directly linked to TTF (Py-TTF) and a second with a phenyl spacer between the pyridine and TTF (Py-phTTF), were employed to vary the distance between the primary photosensitizer/electron donor, zinc porphyrin, and the secondary electron donor, TTF. Both Py-TTF and Py-phTTF coordinated via the pyridine entity to the Zn center with 1:1 molecular stoichiometry and moderate binding constants. The supramolecular triads were characterized by optical absorption and emission, electrochemistry, and computational studies. An energy-level diagram was established to realize the different photochemical events in the triads. Using femtosecond transient absorption spectroscopy, it was possible to show that the coordinated TTF participated in electron transfer from the 1(F15P)Zn* in the case of the C60-(F15P)Zn:TTF triads to produce C60-(F15P)Zn•-:TTF•+ charge-separated state competitively with the electron transfer from the 1(F15P)Zn* to covalently linked C60 to produce C60•--(F15P)Zn•+:TTF charge-separated state. The two charge-separated states, C60-(F15P)Zn•-:TTF•+ and C60•--(F15P)Zn•+:TTF, were further involved in electron migration in the former case and hole transfer in the latter case to produce the C60•--(F15P)Zn:TTF•+ charge-separated state as the ultimate electron-transfer product. Due to distal separation of the positive and negative radical ions, long-lived charge-separated states persistent for about 0.35 μs was possible to accomplish, as shown by nanosecond transient absorption spectral studies.

Mechanistic insight into the photodynamic effect mediated by porphyrin-fullerene C60 dyads in solution and in Staphylococcus aureus cells.

The photodynamic action mechanism sensitized by a non-charged porphyrin-fullerene C60 dyad (TCP-C60) and its tetracationic analogue (TCP-C604+) was investigated in solution and in Staphylococcus aureus cells. The ability of both dyads to form a photoinduced charge-separated state was evidenced by the reduction of methyl viologen in N,N-dimethylformamide (DMF). Moreover, the formation of superoxide anion radicals induced by these dyads was detected by the reduction of nitro blue tetrazolium. Also, photosensitized decomposition of l-tryptophan (Trp) was investigated in the presence of reactive oxygen species (ROS) scavengers. The addition of β-carotene and sodium azide had a slight effect on reaction rate. However, photooxidation of Trp mediated by TCP-C60 was negligible in the presence of d-mannitol, while no protection was found using TCP-C604+. In a polar medium, these dyads mainly act by a contribution of type I pathway with low generation of singlet molecular oxygen, O2(1Δg). In S. aureus cell suspensions, an aerobic atmosphere was required for the photokilling of this bacterium. The photocytotoxicity induced by TCP-C60 was increased in D2O with respect to water, while a small effect was found using TCP-C604+. Furthermore, photoinactivation of microbial cells was negligible in the presence of sodium azide. The addition of d-mannitol did not affect the photoinactivation induced by TCP-C60. In contrast, S. aureus cells were protected by d-mannitol when TCP-C604+ was used as a photosensitizer. Also, generation of O2(1Δg) in the S. aureus cells was higher for TCP-C60 than TCP-C604+. Therefore, TCP-C60 appears to act in microbial cells mainly through the mediation of O2(1Δg). Although, a contribution of the type I mechanism was found for cell death induced by TCP-C604+. Therefore, these dyads with high capacity to produce photoinduced charge-separated state represent interesting photosensitizers to inactivate microorganisms by type I or type II mechanisms. In particular, TCP-C60 may be located in a non-polar microenvironment in the cells favoring a type II pathway, while a contribution of the type I mechanism was produced using the cationic TCP-C604+.

Effect of the triazole ring in zinc porphyrin-fullerene dyads on the charge transfer processes in NiO-based devices.

Herein, the synthesis of three covalently linked donor-acceptor zinc porphyrin-fullerene (ZnP-C60) dyads (C60trZnPCOOH, C60trZnPtrCOOH and C60ZnPCOOH) is described, and their application as sensitizers in NiO-based dye-sensitized solar cells (DSCs) is discussed. To the best of our knowledge, this is the first example where covalently linked ZnP-C60 dyads have been used as chromophores in NiO-based DSCs. In an effort to examine whether the distance of the chromophore from the electron acceptor entity and/or the NiO surface affects the performance of the cells, a triazole ring was introduced as a spacer between ZnP and the two peripheral units C60 and -COOH. The triazole ring was inserted between ZnP and C60 in dyad C60trZnPCOOH, whereas both the anchoring group and C60 were connected to ZnP through triazole spacers in C60trZnPtrCOOH, and dyad C60ZnPCOOH did not contain any triazole linker. Photophysical investigation performed by ultrafast transient absorption spectroscopy in solution and on the NiO surface demonstrated that all the porphyrin-fullerene dyads exhibited long-lived charge-separated states due to electron shifts from the reduced porphyrin core to C60. The transient experiments performed in solution showed that the presence of triazole ring influenced the photophysical properties of the dyads C60trZnPCOOH and C60trZnPtrCOOH and in particular, increased the lifetime of the charge-separated states compared to that of the C60ZnPCOOH dyad. On the other hand, the corresponding studies on the NiO surface proved that the triazole spacer has a rather moderate impact on the charge separation (NiO-ZnP˙+-C60˙-) and charge recombination (NiO-3*ZnP-C60) rate constants. All three dyads exhibited enhanced performance in terms of photovoltaic measurements with more than threefold increase compared to the reference compound PhtrZnPCOOH in which the C60 acceptor is absent. Two different electrolytes were examined (I3-/I- and CoIII/II) and in most cases, the presence of the triazole ring enhanced their photovoltaic performance. The best performing dyad in I3-/I- was C60trZnPCOOH (PCE = 0.076%); in CoIII/II, the best performing dyad was C60trZnPtrCOOH (PCE = 0.074%).

Structure-Photoproperties Relationship Investigation of the Singlet Oxygen Formation in Porphyrin-Fullerene Dyads.

A systematic structure-photoproperties relationship study of the interactions of porphyrin-fullerene dyads with molecular oxygen was conducted on a set of three porphyrin-fullerene dyads, as this approach of related applications - oxygen sensitivity and photo-induced singlet oxygen generation - of such dyads remained to be endeavoured. To promote energy transfers between the porphyrin and fullerene units and limit undesired charge separation, a particular attention was devoted to the choice of the solvents for the photoproperties determination. Toluene, in which in addition the compounds investigated are not aggregated, was selected accordingly. The molecular orbital levels and energy gaps of the dyads were determined by electrochemistry and theoretical calculations. Their ground state absorption, steady-state fluorescence-based oxygen sensitivity and photo-induced singlet oxygen generation were determined. The dyads were designed to benefit from a facilitated synthetic porphyrin-fullerene coupling thanks to an easy access to formyl-functionalized porphyrins. The effect of two structural parameters was investigated: the presence of electron-donating hexyloxy chains at the para position of the meso-phenyl, and the presence of a phenylacetylene spacer. This latest factor appeared to have the most predominant effect on all these properties.