Towards the generation of photoactive nanomaterials: a supramolecular approach

Objective of these four first chapters is to have a complete understanding of the supramolecular organisation of several complementary modules able to form 2-D networks first in solution using optical spectroscopy measurements as function of solvent polarity , concentration and temperature, and then on solid surface using microscopy techniques such as STM, AFM and TEM. The last chapter presents another type of supramolecular material for application in solar cells technology involving fullerenes and OPV systems. We describes the photoinduced energy and electron process using transient absorption experiments. All these systems provide an exceptional example for the potential of the supramolecular approach as an alternative to the restricted lithographic method for the fabrication of adressable molecular devices

Photoinduced electron transfer in a fullerene–oligophenylenevinylene dyad

none8A dialkylamino-subtituted oligophenylenevinylene (OPV) derivative bearing a fullerene subunit (F–D) has been prepared. The electrochemical properties of F–D have been investigated by cyclic voltammetry. Whereas the first reduction is centered on the C60 unit, the oxidation is centered on the dialkylamino subunit of the OPV rod. In F–D, both the OPV and the fullerene-centered fluorescence bands are quenched and this suggests the presence of photoinduced electron transfer from the amino-substituted OPV to the carbon sphere. By means of bimolecular quenching experiments, transient absorption spectral fingerprints of the radical cationic species have been detected in the VIS (670 nm) and NIR (1300–1500 nm) regions, along with the much weaker fullerene anion band at max = 1030 nm. Intramolecular photoinduced electron transfer occurs in the investigated dyad and a relatively long-lived charge-separated state has been detected, with a lifetime of 135 and 85 ns in toluene and benzonitrile, respectively. The longer lifetime in the less polar solvent suggests a Marcus inverted region behavior for the charge recombination process.noneA. Gégout; J. L. Delgado; J-F. Nierengarten; B. Delavaux-Nicot; A. Listorti; C. Chiorboli; A. Belbakra; N. ArmaroliA., Gégout; J. L., Delgado; J. F., Nierengarten; B., Delavaux Nicot; A., Listorti; Chiorboli, Claudio; A., Belbakra; N., Armarol

Photoinduced electron transfer in a fullerene–oligophenylenevinylene dyad

A dialkylamino-subtituted oligophenylenevinylene (OPV) derivative bearing a fullerene subunit (F-D) has been prepared. The electrochemical properties of F-D have been investigated by cyclic voltammetry. Whereas the first reduction is centered on the C60 unit, the oxidation is centered on the dialkylamino subunit of the OPV rod. In F-D, both the OPV and the fullerene-centered fluorescence bands are quenched and this suggests the presence of photoinduced electron transfer from the amino-substituted OPV to the carbon sphere. By means of bimolecular quenching experiments, transient absorption spectral fingerprints of the radical cationic species have been detected in the VIS (670 nm) and NIR (1300-1500 nm) regions, along with the much weaker fullerene anion band at λmax = 1030 nm. Intramolecular photoinduced electron transfer occurs in the investigated dyad and a relatively long-lived charge-separated state has been detected, with a lifetime of 135 and 85 ns in toluene and benzonitrile, respectively. The longer lifetime in the less polar solvent suggests a Marcus inverted region behavior for the charge recombination process

CCDC 631312: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures

Cyanobuta-1,3-dienes as Novel Electron Acceptors for Photoactive Multicomponent Systems

The synthesis, electrochemical, and photophysical properties of five multicomponent systems featuring a ZnII porphyrin (ZnP) linked to one or two anilino donor-substituted pentacyano- (PCBD) or tetracyanobuta-1,3- dienes (TCBD), with and without an interchromophoric bridging spacer (S), are reported: ZnP-S-PCBD (1), ZnP-S-TCBD (2), ZnP-TCBD (3), ZnP-(S-PCBD)2 (4), and ZnP-(S-TCBD)2 (5). By means of steady-state and time-resolved absorption and luminescence spectroscopy (RT and 77 K), photoinduced intramolecular energy and electron transfer processes are evidenced, upon excitation of the porphyrin unit. In systems equipped with the strongest acceptor PCBD and the spacer (1, 4), no evidence of electron transfer is found in toluene, suggesting ZnP→PCBD energy transfer, followed by ultrafast (<10 ps) intrinsic deactivation of the PCBD moiety. In the analogous systems with the weaker acceptor TCBD (2, 5), photoinduced electron transfer occurs in benzonitrile, generating a charge-separated (CS) state lasting 2.3 μs. Such a long lifetime, in light of the high Gibbs free energy for charge recombination (ΔGCR=-1.39 eV), suggests a back-electron transfer process occurring in the so-called Marcus inverted region. Notably, in system 3 lacking the interchromophoric spacer, photoinduced charge separation followed by charge recombination occur within 20 ps. This is a consequence of the close vicinity of the donor-acceptor partners and of a virtually activationless electron transfer process. These results indicate that the strongly electron-accepting cyanobuta-1,3-dienes might become promising alternatives to quinone-, perylenediimide-, and fullerene-derived acceptors in multicomponent modules featuring photoinduced electron transfer. Catch the electron: Strongly electron-accepting multicyanobuta-1,3-dienes provide a new class of electron acceptors for incorporation into photoactive multicomponent systems. Photophysical and electrochemical investigations revealed photoinduced intramolecular electron transfer (PET) from a ZnII porphyrin to 1,1,4,4-tetracyanobuta-1,3-diene acceptor sites appended by an insulating spacer, with a long-lived charge-separated excited state of 2.3 μs in benzonitrile. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Synthesis, photophysical, electrochemical, and electrochemiluminescent properties of 5,15-bis(9-anthracenyl)porphyrin derivatives

Novel 5,15-bis(9-anthracenyl)porphyrin derivatives (1a, 1b) were synthesized by stepwise Suzuki-type coupling reactions using anthracenyl-boronates bearing various electronically active moieties. Absorption spectra of these porphyrin conjugates reveal some degree of delocalisation with the directly linked chromophores, particularly in the case of anthracenyl-porphyrin bearing dimethylanilino moieties at the two extremities. Fluorescence and 77 K phosphorescence properties indicate that the excitation energy is invariably funnelled to the lowest singlet and triplet states of the porphyrin chromophore. The latter levels have been probed also by transient absorption spectroscopy, showing the typical triplet features detected in meso-substituted porphyrins. Extensive electrochemical studies have been performed to unravel the electronic properties of the newly synthesized porphyrins. Low-temperature cyclic voltammetry investigations showed that the anthracenyl-porphyrins are capable of undergoing as many as four electron transfer processes. In particular, by means of UV-Vis-NIR spectroelectrochemical measurements, a NIR-centred intramolecular photoinduced intervalence charge transfer (IV-CT) from a neutral N,N-dimethylanilino moiety to the N, N-dimethylanilino radical cation has been observed for the doubly-oxidised porphyrin 1b(2+). The molecules also showed unexpected electrogenerated chemiluminescence properties, which revealed to be largely controlled by the electronic characteristics of the peripheral anthracenyl substituents. The structural and the electronic properties of these complexes have been also characterised by DFT calculations, as well as by X-ray crystallographic analyses