Vicente M. Blas-Ferrando

Submillisecond-lived photoinduced charge separation in a fully conjugated phthalocyanine–perylenebenzimidazole dyad

A fully electronically conjugated phthalocyanine–perylenemonoimidebenzimidazole system, ZnPc–PMIBI 2, where the conjugation goes through the imide position of the perylene has been synthesized. The preparation was made possible by the condensation of a new unsymmetrically substituted diaminophthalocyanine, ZnPc(NH2)2, with a perylene monoanhydride monoimide. Both the experimental and the computational (DFT) results indicate that ZnPc–PMIBI exhibits significant intramolecular electronic interactions. The lifetime of the charge-separated (CS) state was extended to 0.26 ms, corresponding to the longest value ever reported for a covalent phthalocyanine–peryleneimide system in solution, and is attributed to the synergy of an extremely low CS energy, lower than the triplet energy of each chromophore, together with the coupling between both units, allowing fast charge separation.

Near-Infrared Photoelectrochemical Conversion via Photoinduced Charge Separation in Supramolecular Complexes of Anionic Phthalocyanines with Li+@C60

Two phthalocyanines possessing carboxylate groups ((TBA)4H2Pc·1 and (TBA)4H2Pc·2) form 1:2 supramolecular complexes with lithium cation-encapsulated C60 (Li(+)@C60) [H2Pc·1(4-)/(Li(+)@C60)2 and H2Pc·2(4-)/(Li(+)@C60)2] in a polar mixed solvent. From the UV-vis spectral changes, the binding constants (K) were estimated as ca. 10(12) M(-2). Upon the photoexcitation of constructed supramolecular complexes, photoinduced electron transfer occurred to form the charge-separated (CS) state. The lifetime of the CS state was determined to be 1.2 ms for H2Pc·2(4-)/(Li(+)@C60)2, which is the longest CS lifetime among the porphyrinoid/fullerene supramolecular complexes. H2Pc·1(4-)/(Li(+)@C60)2 also afforded the long-lived CS state of 1.0 ms. The spin state of the long-lived CS states was determined to be a triplet, as indicated by the EPR signal at g = 4. The reorganization energy (λ) and the electronic coupling term were determined to be λ = 1.70 eV, V = 0.15 cm(-1) from the temperature dependence of the rate constant for the charge recombination of the CS state of H2Pc·1(4-)/(Li(+)@C60)2. The energy of the CS state (0.49 eV) is much smaller than the reorganization energy, indicating that the back-electron-transfer process is located in the Marcus normal region. The small electronic coupling term results from the spin-forbidden back electron transfer due to the triplet CS state. Supramolecular complexes of anionic zinc phthalocyanines with Li(+)@C60 were also prepared and investigated. The ZnPc·4(4-)/Li(+)@C60 supramolecular nanoclusters were assembled on the optically transparent electrode (OTE) of nanostructured SnO2 (OTE/SnO2) to construct the dye-sensitized solar cell. The IPCE (incident photon-to-photocurrent efficiency) values of OTE/SnO2/(ZnPc·4(4-)/Li(+)@C60)n were much higher than the sum of the two IPCE values of the individual systems OTE/SnO2/(Li(+)@C60)n and OTE/SnO2/(ZnPc·4(4-))n, covering the near-infrared region.

Large-Size Star-Shaped Conjugated (Fused) Triphthalocyaninehexaazatriphenylene

Star-shaped triphthalocyaninehexaazatriphenylene 1 was synthesized via condensation between a new building block 1,2-diaminophthalocyanine and cyclohexanehexaone. Compound 1 represents the largest star-shaped phthalocyanine-fused hexaazatriphenylene reported so far. This largely expanded phthalocyanine shows good solubility and has a strong tendency to aggregate both in solution and on the surface, indicating its potential as an active component in organic electronic devices.

Synthesis and characterization of a sulfur-containing phtha locyanine-gold nanoparticle hybrid

This work reports on the synthesis and characterization of a new gold nanoparticle- zinc phthalocyanine system, AuNP-S( t Bu)3ZnPc, prepared by a ligand exchange reaction of tetraoctylammonium bromide with a novel unsymmetrically substituted zinc phthalocyanine which contains one thioester group in the peripheral position (AcS( t Bu)3ZnPc). The AuNp-S( t Bu)3ZnPc hybrid was characterized using UV-vis and 1 H NMR spectroscopies. Transmission electron microscopy allowed the estimation of the size, which was calculated to be ~5 nm. AuNPs-S( t Bu)3ZnPc conjugate showed much lower fluorescence quantum yield values than the AcS( t Bu)3ZnPc demonstrating either an energy or electron transfer from the ZnPc to the AuNP. The AuNP-S( t Bu)3ZnPc hybrid has been anchored to a TiO2 semiconducting layer using lipoic acid. A solid configuration of TiO 2-lipoic acid-AuNP-S( t Bu)3ZnPc has been prepared by anchoring lipoic acid to the TiO2 (TiO2-LA) and introducing later the TiO2-LA with free thiol groups in a toluene solution of AuNP-S( t Bu)3ZnPc. We have also observed by UV-vis and fluorescence measurements the importance of the ZnPc in avoiding AuNP aggregation on the TiO 2 surface.

Phthalocyanine-Gold Nanoparticle Hybrids: Modulating Quenching with a Silica Matrix Shell.

An asymmetrically substituted zinc phthalocyanine (ZnPc) with a terminal dithiolane group is anchored to Au nanoparticles (NPs) directly or through an interposed silica matrix. Transient absorption spectroscopy shows that the quenching of the ZnPc excited state by AuNPs occurs through a photoinduced electron transfer, the efficiency of which is modulated by the presence of the insulating silica matrix.