A facile and fast approach, based on microwave-enhanced Sonogashira coupling, has been employed to obtain in good yields both mono- and, for the first time, disubstituted push-pull Zn(II) porphyrinates bearing a variety of ethynylphenyl moieties at the β-pyrrolic position(s). Furthermore, a comparative experimental, electrochemical, and theoretical investigation has been carried out on these β-mono- or disubstituted Zn(II) porphyrinates and meso-disubstituted push-pull Zn(II) porphyrinates. We have obtained evidence that, although the HOMO-LUMO energy gap of the meso-substituted push-pull dyes is lower, so that charge transfer along the push-pull system therein is easier, the β-mono- or disubstituted push-pull porphyrinic dyes show comparable or better efficiencies when acting as sensitizers in DSSCs. This behavior is apparently not attributable to more intense B and Q bands, but rather to more facile charge injection. This is suggested by the DFT electron distribution in a model of a β-monosubstituted porphyrinic dye interacting with a TiO2 surface and by the positive effect of the β substitution on the incident photon-to-current conversion efficiency (IPCE) spectra, which show a significant intensity over a broad wavelength range (350-650 nm). In contrast, meso-substitution produces IPCE spectra with two less intense and well-separated peaks. The positive effect exerted by a cyanoacrylic acid group attached to the ethynylphenyl substituent has been analyzed by a photophysical and theoretical approach. This provided supporting evidence of a contribution from charge-transfer transitions to both the B and Q bands, thus producing, through conjugation, excited electrons close to the carboxylic anchoring group. Finally, the straightforward and effective synthetic procedures developed, as well as the efficiencies observed by photoelectrochemical measurements, make the described β-monosubstituted Zn(II) porphyrinates extremely promising sensitizers for use in DSSCs.

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We investigated the impact of Singly Occupied Molecular Orbital (SOMO) energy on the n-doping efficiency of benzimidazole-derivatives. By designing and synthesizing a series of new air-stable benzimidazole-based dopants with different SOMO energy levels, we demonstrated that an increase of the dopant SOMO energy by only ~0.3 eV enhances the electrical conductivity of a benchmark electron-transporting naphthalenediimide-bithiophene polymer by more than one order of magnitude. By combining electrical, X-ray diffraction, and electron paramagnetic resonance measurements with density functional theory calculations and analytical transport simulations, we quantitatively characterized the conductivity, Seebeck coefficient, spin density, crystallinity of the doped polymer as a function of the dopant SOMO energy. Our findings strongly indicate that charge and energy transport are dominated by the (relative) position of the SOMO level, whereas morphological differences appear to play a lesser role. These results set molecular-design guidelines for next-generation ntype dopants.

This work has produced experimental and theoretical evidence for the independence, on the nature of the metal, of the second order NLO response of [5-[[4′-(dimethylamino)phenyl]ethynyl]-15-[(4′′-nitrophenyl)ethynyl]-10,20-diphenylporphyrinate]M(II) NLO chromophores (M = Zn, Ni). EFISH measurements, carried out at a nonresonant 1.907 μm incident wavelength and at variable concentrations in CHCl3 or in a polar and donor solvent such as DMF or by addition of an excess of pyridine to a CHCl3 solution, have shown, together with a PGSE NMR investigation, that the different second order NLO response obtained in CHCl3 for Zn(II) and Ni(II) NLO chromophores is due to a different aggregation in CHCl3 solution. Theoretical DFT/TDDFT calculations on the NLO properties of dimeric aggregates of the NLO chromophores containing the Zn(II) center have suggested, in agreement with EFISH measurements and PGSE NMR investigation, a J aggregation which induces a doubling of the second order NLO response. The PGSE NMR investigation has also suggested a much weaker dipolar interaction for the dimerization process of the NLO chromophores containing the Ni(II) center. In this latter case the antiparallel alignment of the dipole moments of the two chromophores produces a lower second order NLO response, as experimentally observed in CHCl3 solution by increasing concentration.

A multitechnique physicochemical comparative investigation involving TDDFT theoretical calculations, steady-state and time-resolved electronic absorption spectra, and electrochemical and photoelectrochemical investigations was carried out on a family of push–pull porphyrinic sensitizers ([5-(4′-carboxy-phenylethynyl)-15-(4″-methoxy-phenylethynyl)-10,20-bis(3,5-di-tert-butylphenyl)porphyrinate]Zn(II) (1) and [5-(4′-carboxy-phenylethynyl)-15-(4″-N,N-dimethylamino-phenylethynyl)-10,20-bis(3,5-di-tert-butylphenyl)porphyrinate]Zn(II) (2) and the new fluorinated porphyrinic dye [5-(4′-carboxy-2′,3′,5′,6′-tetrafluorophenylethynyl)-15-(4″-N,N-dimethylamino-phenylethynyl)-10,20-bis(3,5-di-tert-butylphenyl)porphyrinate]Zn(II) (3)) with the aim of identifying the structurally related electronic properties at the basis of efficient interfacial charge separation. We found for all dyes a photoconversion nearly twice more effective for the B band than for the Q band, which could not be explained only by considerations based on the electron collection efficiency but also by a more energetically favorable electron injection from the S2 excited state. The lower photoconversion of the fluorinated dye 3, when compared to dyes 1 and 2, was explained not only by a more difficult absorption on the TiO2 photoanode but also by a lower electron injection efficiency and a less successful hole transfer to the electrolyte, leading to increased charge recombination.

Pd nanoparticles within a nitrogen‐containing covalent triazine framework (CTF) material are investigated to understand if the highly tunable CTF chemistry mediates the catalytic properties of the Pd nanoparticles. Surprisingly, our results demonstrate that the CTF stabilizes the formation of 2.6 nm PdHx particles within the pores. These confined PdHx particles are very active for the liquid‐phase oxidation of glycerol and promote CC cleavage, probably connected with the enhanced in situ formation of H2O2. During recycling tests, the confined particles are transformed progressively to very stable Pd0 particles. This stability has been attributed mainly to a confinement effect as nanoparticles trapped outside the pores lose activity rapidly. These results indicate that there is a potential to tune CTF chemistry to modify the chemistry of the catalytic metals significantly.

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The synthesis and characterization of novel fluorinated Er 3+ complexes emitting at the telecommunications wavelengths are presented. These new knowledge-based materials have been designed and optimized on the basis of an extensive photophysical investigation on the processes controlling the overall quantum yield, namely (i) the energy transfer process from the light harvesting conjugated antenna to the emitting ion and (ii) the nonradiative quenching of the lanthanide emission. The study of their photophysical properties has been used for the assessment of their application as active materials in a new generation of low-cost, optical communication amplifiers, based on solution-processed planar waveguides pumped by light emitting diodes (LEDs). Suitable ligands possessing a high-absorption cross-section (where commercially available LEDs operate), good energy level matching those of the ion, and high solubility in fluorinated polymers have been developed.