Tris-Heteroleptic Ruthenium-Dipyrrinate Chromophores in a Dye-Sensitized Solar Cell

Impact of Anchoring Groups on the Photocatalytic Performance of Iridium(III) Complexes and Their Toxicological Analysis

Three different iridium(III) complexes, labelled as Ir1-Ir3, each bearing a unique anchoring moiety (diethyl [2,2'-bipyridine]-4,4'-dicarboxylate, tetraethyl [2,2'-bipyridine]-4,4'-diylbis(phosphonate), or [2,2'-biquinoline]-4,4'-dicarboxylic acid), were synthesized to serve as photosensitizers. Their electrochemical and photophysical characteristics were systematically investigated. ERP measurements were employed to elucidate the impact of the anchoring groups on the photocatalytic hydrogen generation performance of the complexes. The novel iridium(III) complexes were integrated with platinized TiO2 (Pt-TiO2) nanoparticles and tested for their ability to catalyze hydrogen production under visible light. A H2 turnover number (TON) of up to 3670 was obtained upon irradiation for 120 h. The complexes with tetraethyl [2,2'-bipyridine]-4,4'-diylbis(phosphonate) anchoring groups were found to outperform those bearing other moieties, which may be one of the important steps in the development of high-efficiency iridium(III) photosensitizers for hydrogen generation by water splitting. Additionally, toxicological analyses found no significant difference in the toxicity to luminescent bacteria of any of the present iridium(III) complexes compared with that of TiO2, which implies that the complexes investigated in this study do not pose a high risk to the aquatic environment compared to TiO2.

Recent developments in dipyrrin based metal complexes: Self-assembled nanoarchitectures and materials applications

While dipyrrin-boron complexes (BODIPYs) and their derivatives have attracted much attention, dipyrrin-based metal complexes recently appeared as a novel luminescent material. So far, dipyrrin-metal complexes have been regarded as non-luminescent or weakly luminescent. Interestingly, introduction of steric hindrance at the meso-position and the development of heteroleptic complexes with proper frontier orbital ordering are two recent strategies that have been developed to improve their luminescent ability. Compared with BODIPYs, one of the distinctive advantages of dipyrrin-metal complexes is that they can form a series of self-assembled supramolecules and polymer assemblies via facile coordination reactions. In recent times, several supramolecular, coordination polymers and Metal-Organic Frameworks (MOFs) have been developed, [Formula: see text] by spontaneous coordination reactions between dipyrrin ligands and metal ions. As a novel luminescent material, dipyrrin-metal complexes have been applied in many fields. This review article summarizes recent developments in dipyrrin-metal complexes from the viewpoint of the improvement of luminescent ability, the formation of supramolecular and coordination polymers and their potential applications.

Dipyrrin based metal complexes: reactivity and catalysis

Sometimes named half-porphyrins, bis-pyrrolic dipyrrin ligands endow their metal complexes with unique properties such as the potential to functionalize the heterocyclic backbone or the meso position and the ability to catalyze interesting chemical transformations. Thus, strategies towards the derivatization of or at the meso group and the use of dipyrrin metal complexes for the formation of a broad range of polypyrrolic derivatives such as 2,2'-bis-dipyrrins, nor-/hetero-corroles and porphynoids have been elaborated. Furthermore, the chelating ability of dipyrrins and the possibility of modifying their steric and electronic characteristics by functionalization can be exploited for the development of numerous complexes featuring appealing properties. Hence, C-H activation/amination, polymerization or oxidation reactions can be catalyzed by dipyrrin metal complexes and classical reagents such as Grignard species, Rh-based or Suzuki-Miyaura catalysts have been revisited by incorporation of dipyrrins in the coordination sphere of the metal cations. This contribution aims to review and illustrate all these aspects, highlighting the potential of these complexes for the design and synthesis of valuable organic compounds and metallo-organic architectures.

Propentdyopents: Brief history of a family of dipyrrolic pigments

Propentdyopents are naturally occurring dipyrroles deriving from the metabolism of heme and characterized by a dipyrrin-1,9-dione motif. The unusual name propentdyopent is due to the first colorimetric method (the Stokvis reaction) for the detection of these compounds, which were initially isolated from urine samples. Upon reduction in alkaline solutions, they produced red species that were termed pentdyopents to describe with Greek numerals their absorption maximum (525 nm) in the visible range. The precursors to the red pentdyopents were thus indicated as propentdyopents.Over the course of several decades, these dipyrrolic compounds have appeared in several studies of human physiology, typically associated to conditions of abnormal heme metabolism and/or oxidative stress. Concurrently, synthetic investigations have confirmed their chemical structure, reactivity, and ability to coordinate metals as bidentate monoanionic ligands. Notably, the planar dipyrrindione platform can undergo reversible one-electron redox processes and thereby act as an electron reservoir in metal complexes. In combination with the documented ability of the carbonyl groups to act as hydrogen-bonding acceptors, the coordination chemistry of propentdyopents could lead to new applications for this old class of pigments. Furthermore, the observation of these pigments in several clinical contexts could potentially delineate a role of propentdyopents as diagnostic biomarkers. This mini-review summarizes both the chemistry and biology of propentdyopents while highlighting the ample space for new discoveries.

Pre-/post-functionalization in dipyrrin metal complexes - antitumor and antibacterial activity of their glycosylated derivatives

A post-functionalization route to tris(dipyrrinato) metal complexes is presented giving access to a range of new complexes relevant in the context of medicinal inorganic chemistry. A pentafluorophenyl group in the meso-position of the dipyrrin ligand serves as an anchor for the connection with alcohols and thiocarbohydrates. The photochemotherapeutic activity of the complexes has been assessed in cellular assays with tumor cell lines and against the Gram-positive bacterium S. aureus. Finally, it is shown that this post-functionalization is also applicable to other dipyrrinato metal complexes.

1,10-Phenanthroline-dithiine iridium and ruthenium complexes: synthesis, characterization and photocatalytic dihydrogen evolution

Extending 1,10-phenanthroline with a dithiine link led to a remarkable increase of the luminescence lifetimes of the respective Ir(ppy)₂ and Ru(bpy)₂ complexes.

Comparative analysis of triarylamine and phenothiazine sensitizer donor units in dye-sensitized solar cells

A homologous set of dyes that differ only in the donor fragments, namely phenothiazine (PTZ) and triarylamine (TPA) units, were evaluated in dye-sensitized solar cells (DSSCs). The novel PTZ-based dye differs from the TPA-based dye in that it contains a sulfur bridge that planarizes two aromatic rings and enables higher dye loading and higher stability in the oxidized form. These positive features notwithstanding, the superior absorptivity of devices sensitized by TPA-based dyes resulted in significantly higher power conversion efficiencies (PCEs) than those sensitized by PTZ-based dyes.

Ruthenium(ii) complexes incorporating carbazole–diazafluorene based bipolar ligands for dye sensitized solar cell applications

A new type of ruthenium sensitizers, S3 and S4, consisting of carbazole–diazafluorene based bipolar ancillary ligands have been synthesized and characterized for dye sensitized solar cells.

Bis-tridentate Ru(ii) sensitizers with a spatially encumbered 2,6-dipyrazolylpyridine ancillary ligand for dye-sensitized solar cells

The sensitizer TF-tBu_C₃F₇ has shown the highest overall efficiencies of J_SC = 18.47 mA cm⁻², V_OC = 767 mV, FF = 0.71 and PCE = 10.05% under simulated one sun irradiation, due to the fine balance between dye loading and reduced charge recombination.

Influence of Ancillary Ligands in Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have motivated many researchers to develop various sensitizers with tailored properties involving anchoring and ancillary ligands. Ancillary ligands carry favorable light-harvesting abilities and are therefore crucial in determining the overall power conversion efficiencies. The use of ancillary ligands having aliphatic chains and/or π-extended aromatic units decreases charge recombination and permits the collection of a large fraction of sunlight. This review aims to provide insight into the relationship between ancillary ligand structure and DSSC properties, which can further guide the function-oriented design and synthesis of different sensitizers for DSSCs. This review outlines how the new and rapidly expanding class of chelating ancillary ligands bearing 2,2'-bipyridyl, 1,10-phenanthroline, carbene, dipyridylamine, pyridyl-benzimidazole, pyridyl-azolate, and other aromatic ligands provides a conduit for potentially enhancing the performance and stability of DSSCs. Finally, these classes of Ru polypyridyl complexes have gained increasing interest for feasible large-scale commercialization of DSSCs due to their more favorable light-harvesting abilities and long-term thermal and chemical stabilities compared with other conventional sensitizers. Therefore, the main idea is to inspire readers to explore new avenues in the design of new sensitizers for DSSCs based on different ancillary ligands.

Molecularly Engineered Ru(II) Sensitizers Compatible with Cobalt(II/III) Redox Mediators for Dye-Sensitized Solar Cells

Thiocyanate-free isoquinazolylpyrazolate Ru(II) complexes were synthesized and applied as sensitizers in dye-sensitized solar cells (DSCs). Unlike most other successful Ru sensitizers, Co-based electrolytes were used, and resulting record efficiency of 9.53% was obtained under simulated sunlight with an intensity of 100 mW cm(-2). Specifically, dye 51-57dht.1 and an electrolyte based on Co(phen)3 led to measurement of a JSC of 13.89 mA cm(-2), VOC of 900 mV, and FF of 0.762 to yield 9.53% efficiency. The improved device performances were achieved by the inclusion of 2-hexylthiophene units onto the isoquinoline subunits, in addition to lengthening the perfluoroalkyl chain on the pyrazolate chelating group, which worked to increase light absorption and decrease recombination effects when using the Co-based electrolyte. As this study shows, Ru(II) sensitizers bearing sterically demanding ligands can allow successful utilization of important Co electrolytes and high performance.

High photo-currents with a zwitterionic thiocyanate-free dye in aqueous-based dye sensitized solar cells

A zwitterionic dye shows high photocurrent and incident photon to current efficiency in water based dye sensitized solar cells.

Azadipyrromethene cyclometalation in neutral RuII complexes: photosensitizers with extended near-infrared absorption for solar energy conversion applications

In the on-going quest to harvest near-infrared (NIR) photons for energy conversion applications, a novel family of neutral ruthenium(ii) sensitizers has been developed by cyclometalation of an azadipyrromethene chromophore.

New thiocyanate-free ruthenium(ii) sensitizers with different pyrid-2-yl tetrazolate ligands for dye-sensitized solar cells

The synthesis of two new stable thiocyanate free Ru(ii) complexes with different pyrid-2-yl tetrazolate ligands is reported, along with promising DSSCs.