Sensitization of TiO 2 by Supramolecules Containing Zinc Porphyrins and Ruthenium−Polypyridyl Complexes (original) (raw)
Related papers
Dyes and Pigments, 2021
In the current work, we present the use of two free-base and two zinc-metallated porphyrinruthenium(II) polypyridine dyads, along with two reference porphyrin derivatives, as sensitizers in both n-and p-type DSSCs and DSPECs. Two of the dyads contain the well-known Ru(bpy)3 unit (HOOC-DMP-Ru(bpy)3 and HOOC-(Zn)DMP-Ru(bpy)3), while in the other two terpyridine-Ru(Cl)-bypiridine was used (HOOC-DMP-tpy-Ru and HOOC-(Zn)DMP-tpy-Ru). In all systems, the amide-bonding motif was utilized for the connection of the counterparts comprising each dyad. Photophysical investigation of the reported systems indicated sufficient electronic interactions for the dyads in their excited states (emission measurements). The photovoltaic measurements revealed that the presence of the ruthenium complex improves the overall performance of the dyads with the most efficient dyad being HOOC-(Zn)DMP-tpy-Ru in both n-and p-type DSSCs. Consequently, HOOC-(Zn)DMP-tpy-Ru was used to fabricate n-and p-DSPECs towards the oxidation of methoxybenzyl alcohol and the reduction of CO2, respectively.
Macromolecular Symposia, 2020
Porphyrin has excellent optical properties as required in solar cell applications, for example, high molar extinction coefficient and high quantum efficiency (≈80%). Excellent optical properties make porphyrin a good candidate as a photosensitizer, that is, in dye-sensitized solar cells (DSSC). Nevertheless, porphyrins exhibit poor charge transfer resulting in poor cell performance. Poor charge transfer in porphyrins is due to the aggregation, low porphyrin adsorption, and weakly bound porphyrins on the TiO 2 surface. Anchoring group attached to the porphyrin ring may play an important role to increase both charge transfer and porphyrin adsorption. This study adopts a strategy to increase the electron transfer from porphyrins to TiO 2 by applying different anchoring groups. This strategy aims both to reduce the aggregation and to enhance the binding between porphyrin and TiO 2 surface. The presence of methyl and carboxylic acid as the anchoring groups in the porphyrin system can increase the electronic coupling between the porphyrin and the TiO 2 surface while also hindering the aggregation. Thus, the presence of anchoring groups improves the electron injection efficiency and cell performance. The type and position of the anchoring groups strongly contribute to the electron injection, thus is discussed in detail.
New Journal of Chemistry, 2008
A saddle shaped tetracluster porphyrin species containing four [Ru 3 O(OAc) 6 (py) 2 ] + clusters coordinated to the N-pyridyl atoms of 5,10,15,20-tetra(3-pyridyl)porphyrin, H 2 (3-TCPyP), has been investigated in comparison with the planar tetra(4-pyridyl)porphyrin analogue H 2 (4-TCPyP). The steric effects from the bulky peripheral complexes play a critical role in the H 2 (3-TCPyP) species, determining a non-planar configuration around the porphyrin centre and precluding any significant p-electronic coupling, in contrast with the less hindered H 2 (4-TCPyP) species. Both systems exhibit a photoelectrochemical response in the presence of nanocrystalline TiO 2 films, involving the porphyrin excitation around 450 nm. However, only in the H 2 (4-TCPyP) case do the cluster moieties also contribute to the photoinduced electron injection process at 670 nm, reflecting the relevance of the electronic coupling between the porphyrin centre and the peripheral complexes.
Thermally induced anchoring of a zinc-carboxyphenylporphyrin on rutile TiO2 (110)
The Journal of Chemical Physics
Functionalization of surfaces has become of high interest for a wealth of applications such as sensors, hybrid photovoltaics, catalysis, and molecular electronics. Thereby molecule-surface interactions are of crucial importance for the understanding of interface properties. An especially relevant point is the anchoring of molecules to surfaces. In this work, we analyze this process for a zinc-porphyrin equipped with carboxylic acid anchoring groups on rutile TiO 2 (110) using scanning probe microscopy. After evaporation, the porphyrins are not covalently bound to the surface. Upon annealing, the carboxylic acid anchors undergo deprotonation and bind to surface titanium atoms. The formation of covalent bonds is evident from the changed stability of the molecule on the surface as well as the adsorption configuration. Annealed porphyrins are rotated by 45 • and adopt another adsorption site. The influence of binding on electronic coupling with the surface is investigated using photoelectron spectroscopy. The observed shifts of Zn 2p and N 1s levels to higher binding energies indicate charging of the porphyrin core, which is accompanied by a deformation of the macrocycle due to a strong interaction with the surface.
Journal of Molecular Structure, 2019
Unsymmetrical porphyrins were rationally-designed and synthesized to investigate the relation between their structure, properties and adsorption geometries, and their relative performance as dyes in dyesensitized solar cells. Photophysics, electrochemical and TiO2 anchoring properties of the new unsymmetrical Nglycolic acid amino phenyl porphyrins were evaluated. Most dyes showed good energy matching between excited state energies and the TiO2 conduction band. Depending on the porphyrins, anchoring to TiO2 occurred with only one carboxyl anchor group or with two N-glycolic acid amino phenyl connected to opposite and adjacent phenyl groups. It was found that cell efficiencies normalized for surface coverage are strongly affected by the adsorption geometry and spacer linker flexibility. The effective distance between the porphyrin core and the TiO2 surface has key importance in cell efficiencies. The data is consistent with a through-space electron transfer and anchoring via N-glycolic acid substituents located in adjacent phenyl groups results in higher surface coverage normalized cell efficiencies.
Thin molecular films of supramolecular porphyrins
Anais da Academia Brasileira de Ciências, 2000
A relevant series of symmetric supramolecular porphyrins has been obtained by attaching four [Ru II (bipy) 2 Cl] groups to the pyridyl substituents of meso-tetra(4-pyridyl)porphyrin and its metallated derivatives. These compounds display a rich electrochemistry and versatile catalytic, electrocatalytic and photochemical properties, associated with the ruthenium-bipyridine and the porphyrin complexes. These properties can be transferred to the electrodes by attaching thin molecular films of the compounds, by dip-coating, electrostatic assembly or electropolymerization. In this way, the interesting properties of those supermolecules and supramolecular assemblies can be used to prepare molecular devices and sensors.