Electrostatic Association of Ammonium-Functionalized Layered-Transition-Metal Dichalcogenides with an Anionic Porphyrin

Ammonium-modified MoS₂ and WS₂ were prepared and characterized by complementary spectroscopic, thermal, and microscopic means. The positive charges on functionalized MoS₂ and WS₂, due to the presence of ammonium units, were exploited to electrostatically bring in contact an anionic porphyrin bearing a carboxylate moiety, yielding porphyrin/MoS₂ and porphyrin/WS₂ ensembles, <b>5a</b> and <b>5b</b>, respectively. Efficient photoluminescence quenching of porphyrin’s emission by MoS₂ and WS₂ within nanoensembles <b>5a</b> and <b>5b</b>, in combination with time-resolved photoluminescence assays, revealed transduction of energy from the photoexcited porphyrin to MoS₂ or WS₂

“Spider”-Shaped Porphyrins with Conjugated Pyridyl Anchoring Groups as Efficient Sensitizers for Dye-Sensitized Solar Cells

Two novel “spider-shaped” porphyrins, <i>meso</i>-tetraaryl-substituted <b>1PV-Por</b> and zinc-metalated <b>1PV-Zn-Por</b>, bearing four oligo­(<i>p</i>-phenylenevinylene) (oPPV) pyridyl groups with long dodecyloxy chains on the phenyl groups, have been synthesized. The presence of four pyridyl groups in both porphyrins, which allow them to act as anchoring groups upon coordination to various Lewis acid sites, the conjugated oPPV bridges, which offer the possibility of electronic communication between the porphyrin core and the pyridyl groups, and the dodecyloxy groups, which offer the advantage of high solubility in a variety of organic solvents of different polarities and could prevent porphyrin aggregation, renders porphyrins <b>1PV-Por</b> and <b>1PV-Zn-Por</b> very promising sensitizers for dye-sensitized solar cells (DSSCs). Photophysical measurements, together with electrochemistry experiments and density functional theory calculations, suggest that both porphyrins have frontier molecular orbital energy levels that favor electron injection and dye regeneration in DSSCs. Solar cells sensitized by <b>1PV-Por</b> and <b>1PV-Zn-Por</b> were fabricated, and it was found that they show power conversion efficiencies (PCEs) of 3.28 and 5.12%, respectively. Photovoltaic measurements (<i>J</i>–<i>V</i> curves) together with incident photon-to-electron conversion efficiency spectra of the two cells reveal that the higher PCE value of the DSSC based on <b>1PV-Zn-Por</b> is ascribed to higher short-circuit current (<i>J</i>_sc), open-circuit voltage (<i>V</i>_oc), and dye loading values. Emission spectra and electrochemistry experiments suggest a greater driving force for injection of the photogenerated electrons into the TiO₂ conduction band for <b>1PV-Zn-Por</b> rather than its free-base analogue. Furthermore, electrochemical impedance spectroscopy measurements prove that the utilization of <b>1PV-Zn-Por</b> as a sensitizer offers a high charge recombination resistance and, therefore, leads to a longer electron lifetime

Case Study for Artificial Photosynthesis: Noncovalent Interactions between C₆₀-Dipyridyl and Zinc Porphyrin Dimer

In this study, a new modified C₆₀ derivative with an oPE/oPPV conjugated bridge bearing two pyridyl groups has been used in combination with a flexible porphyrin dimer (<b>ZnP</b>_<b>2</b>) to construct an electron donor/acceptor hybrid (<b>C</b>_<b>60</b><b>-dipyr·ZnP</b>_<b>2</b>). This hybrid is based on metal to ligand coordination between the zinc centers of the porphyrin dimer and the two pyridyl groups that oPE/oPPV linker bears. In order to investigate the interactions between the electron donor and acceptor entities, both in the ground state and in the excited states, comprehensive photophysical assays have been carried out. In particular, both absorption and fluorescence titrations provided evidence for strong interactions between the electron donor and the electron acceptor within the hybrid. A binding constant (<i>K</i>_ass) in the order of 5.0 × 10⁵ M^–1 has been derived. Furthermore, transient absorption measurements revealed intramolecular electron-transfer from the photoexcited porphyrin dimer (<b>ZnP</b>_<b>2</b>) to the fullerene derivative (<b>C</b>_<b>60</b><b>-dipyr</b>), leading to a long-lived charge-separated state with a lifetime of up to 1525 ps

Long Spin Coherence Times on C₅₉N‑C₆₀ Heterodimer Radicals Entrapped in Cycloparaphenylene Rings

We investigate the effect of introducing C60 to (C59N)2 and the molecular ring, [10]cycloparaphenylene ([10]CPP), using electron paramagnetic resonance (EPR) measurements supported by density functional theory (DFT) calculations. Incorporating C60 into the system results in the formation of novel stable [10]CPP ⊃ C59N-C60• ⊂ [10]CPP encapsulated heterodimer radicals whose spin is localized on C60 and manifests in EPR measurements as a signal at g = 2.0022 without any discernable hyperfine structure. This signal has an exceptionally long spin coherence lifetime of 440 μs at room temperature, far longer than any of the radical fullerene species reported in the literature and over twice that of the C59N• ⊂ [10]CPP radical. The radicals are long-lived, with EPR signal still strong over a year after thermal activation. The [10]CPP ⊃ C59N-C60• ⊂ [10]CPP oligomer is more stable than C59N• ⊂ [10]CPP radicals and becomes the predominant species at room temperature after annealing. Its formation is thermally activated with an experimental activation energy of only 0.189 eV, as compared to 0.485 eV for the pure azafullerene-[10]CPP case. The [10]CPP ⊃ C59N-C60• ⊂ [10]CPP radicals discovered here could be used to bridge C59N• ⊂ [10]CPPs acting as qubits, providing effective coupling between them

VAR Fabric Modification: Inducing Antibacterial Properties, Altering Wettability/Water Repellence, and Understanding Reactivity at the Molecular Level

The present work focuses on the surface coating of VAR technical fibers, consisting of 64% viscose (cellulose), 24% Kevlar, 10% other types of polyamides, and 2% antistatic polymers. Kevlar is an aramid material exhibiting excellent mechanical properties, while cellulose is a natural linear polymer composed of repeating β-d-glucose units, having several applications in the materials industry. Herein, we synthesized novel, tailor-designed organic molecules possessing functional groups able to anchor on VAR fabrics and cellulose materials, thus altering their properties on demand. To this end, we utilized methyl-α-d-glucopyranose as a model compound, both to optimize the reaction conditions, before applying them to the material and to understand the chemical behavior of the material at the molecular level. The efficient coating of the VAR fabric with the tailor-made compounds was then implemented. Thorough characterization studies using Raman and IR spectroscopies as well as SEM imaging and thermogravimetric analysis were also carried out. The wettability and water repellency and antibacterial properties of the modified VAR fabrics were also investigated in detail. To the best of our knowledge, such an approach has not been previously explored, among other factors regarding the understanding of the anchoring mechanism at the molecular level. The proposed modification protocol holds the potential to improve the properties of various cellulose-based materials beyond VAR fabrics