Supramolecular porphyrin as an improved photocatalyst for chloroform decomposition

In this work, the outlying decoration of the free-base meso-(4-tetra) pyridyl porphyrin (H₂TPyP) with the RuCl(dppb)(5,5'-Me-bipy) ruthenium complex (here named Supra-H₂TPyP) is observed as an improved molecular photocatalyst for dye-mediated chloroform (CHCl₃) decomposition via one-photon absorption operating in the visible spectral range (532 nm and 645 nm). Supra-H₂TPyP offers a better option for CHCl₃ photodecomposition when compared to the same process mediated by pristine H₂TPyP, which requires either excited-state- or UV absorption. The chloroform photodecomposition rates for Supra-H₂TPyP as well as its excitation mechanisms are explored as a function of distinct laser irradiation conditions.

Catalytic properties of supramolecular polymetallated porphyrins

Supramolecular polymetallated pyridylporphyrins have been specially designed for exploring the binding and synergism between the macrocyclic system and the peripheral metal complexes. Their chemistry has been reviewed, focusing on the outstanding behavior in solution or as thin organized films generated with several nanomaterials, for application as molecular devices and in energy conversion processes.

Photophysics and visible light photodissociation of supramolecular meso-tetra(4-pyridyl) porphyrin/RuCl2(CO)(PPh3)2 structures

In the last decades, supramolecular structures have been explored in many technological efforts. One example of such supramolecules is attained when ruthenium complexes are attached in the outer sites of a porphyrin. Ruthenium complexes act as modulators of the photophysical processes of macrocyclic molecules. Besides the investigation of the main changes introduced by the ruthenium complexes in the electronic and vibronic properties, and in the excited state deactivation processes of porphyrins, discussions concerning the photostability of these supramolecules are much needed. Here, we investigate the supramolecular free-base meso-tetra(4-pyridyl) porphyrin decorated with "RuCl₂(CO)(PPh₃)₂" ruthenium species linked at each of its (4-pyridyl) moieties. The modifications in the photophysical processes introduced by the metallic outlying species are discussed and our results suggest an energy transfer process from the porphyrin B-band to the ruthenium complex MLCT-band. The demonstration of visible light photodissociation of the supramolecule, via both pulsed and continuous laser, is also addressed.

Surface enhanced Raman spectroelectrochemistry of a μ-oxo triruthenium acetate cluster: an experimental and theoretical approach

Surface enhanced Raman spectroelectrochemistry (SERS) spectroelectrochemistry provides a very sensitive technique to investigate the vibrational characteristics of coordination compounds and their particular behavior under the influence of plasmonic surfaces, concomitant with the exploitation of their redox properties and electronic spectra. The results, however, depend upon the mechanisms involved in the intensification of Raman spectra associated with the electromagnetic, resonance Raman and charge-transfer excitation at the Fermi levels. By probing the model complex [(Ru3O)(CH3COO)6(4,4'-bipy)3](n) (n = 1, 0, -1) adsorbed onto rough gold electrode surfaces, contrasting SERS profiles were obtained at several successive redox potentials and oxidation states, which enables a critical discussion on the role of the complex interaction with the gold surface, and the influence of the specific electronic bands in the triruthenium acetate cluster. Density functional theory (DFT) and time-dependent DFT calculations were carried out for the complex bound to an Au20 cluster to show the participation of active lowest unoccupied molecular orbital levels centered on the gold atoms. The corresponding charge-transfer band was predicted around 1200 nm, which supports a charge-transfer interpretation for the SERS response observed at λexc = 1064 nm. The selective enhancement of the vibrational modes was discussed based on the Raman theoretical calculations.

Probing surface−complex interactions with the bis(4-thienylterpyridine)iron(II) complex anchored on TiO2 and gold nanoparticles

The bis(4-thienylterpyridine)iron(II) complex was employed, in comparison with the 4-phenylterpyridine analogue, as a molecular probe for monitoring the surface plasmon interactions with gold nanoparticles. The two complexes exhibited distinct SERS responses, confirming the binding of the thienyl group to the gold nanoparticles. Their inclusion into β-cyclodextrin anchored on TiO2 surfaces provided a useful system for applications in UV dosimetry, based on the gradual bleaching of the violet-blue color under sunlight and air.

Sevenfold enhancement on porphyrin dye efficiency by coordination of ruthenium polypyridine complexes

Sevenfold enhancement of photoconversion efficiency was achieved by incorporation of peripheral ruthenium complexes to a porphyrin dye, generating supramolecular effects capable of playing several key roles (e.g., transferring energy to, inhibiting aggregation, and accepting the hole generated in the porphyrin center after electron injection), providing new insights for the design of better DSSC photosensitizers.

5-(1-(4-phenyl)-3-(4-nitrophenyl)triazene)-10,15,20-triphenylporphyrin: a new triazene-porphyrin dye and its spectroelectrochemical properties

The new triazene-porphyrin dye 5-(1-(4-phenyl)-3-(4-nitrophenyl)triazene)-10,15,20-triphenylporphyrin, encompassing a reactive protonated triazene moiety, was prepared starting from meso-tetraphenylporphyrin ( H2TPP ), first converting it to the 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin, then reducing to the 5-(4-aminophenyl)-10,15,20-tri(phenyl)porphyrin intermediate, and reacting with the diazonium salt of 4-nitroaniline; and characterized by spectroscopic and electrochemical methods. The absorption spectrum of the neutral species resembled the sum of H2TPP and of 1,3-bis(4-nitrophenyl)triazene spectrum, but the deprotonated anionic species showed more delocalized frontier orbitals, behaving as a push-pull system exhibiting triazenide-to-porphyrin charge-transfer transitions.

Resolution of isomeric multi-ruthenated porphyrins by travelling wave ion mobility mass spectrometry

The ability of travelling wave ion mobility mass spectrometry (TWIM-MS) to resolve cationic meta/para and cis/trans isomers of mono-, di-, tri- and tetra-ruthenated supramolecular porphyrins was investigated. All meta isomers were found to be more compact than the para isomers and therefore mixtures of all isomeric pairs could be properly resolved with baseline or close to baseline peak-to-peak resolution (R(p-p)). Di-substituted cis/trans isomers were found, however, to present very similar drift times and could not be resolved. N(2) and CO(2) were tested as the drift gas, and similar α but considerably better values of R(p) and R(p-p) were always observed for CO(2).

Unravelling the chemical morphology of a mesoporous titanium dioxide interface by confocal Raman microscopy: new clues for improving the efficiency of dye solar cells and photocatalysts

The presence of anatase and rutile domains on nanocrystalline films of P25 TiO2, as well as the distinct coordination modes of carboxylates on those phases, were revealed by confocal Raman microscopy, a technique that showed to be suitable for imaging the chemical morphology down to submicrometric size.