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Searching for a connection between the two-electron redox behavior of Group-14 elements and their possible use as platforms for the photoreductive elimination of chlorine, we have studied the photochemistry of [(o-(Ph2 P)C6 H4 )2 GeIV Cl2 ]PtII Cl2 and [(o-(Ph2 P)C6 H4 )2 ClGeIII ]PtIII Cl3 , two newly isolated isomeric complexes. These studies show that, in the presence of a chlorine trap, both isomers convert cleanly into the platinum germyl complex [(o-(Ph2 P)C6 H4 )2 ClGeIII ]PtI Cl with quantum yields of 1.7 % and 3.2 % for the GeIV -PtII and GeIII -PtIII isomers, respectively. Conversion of the GeIV -PtII isomer into the platinum germyl complex is a rare example of a light-induced transition-metal/main-group-element bond-forming process. Finally, transient-absorption-spectroscopy studies carried out on the GeIII -PtIII isomer point to a ligand arene-Cl. charge-transfer complex as an intermediate.

Developments in the field of photoredox catalysis that leveraged the long-lived excited states of Ir(III) and Ru(II) photosensitizers to enable radical coupling processes paved the way for explorations of synthetic transformations that would otherwise remain unrealized. While first row transition metal photocatalysts have not been as extensively investigated, valuable synthetic transformations covering broad scopes of olefin functionalization have been recently reported featuring photoactivated chlorobis(phenanthroline) Cu(II) complexes. In this study, the photochemical processes underpinning the catalytic activity of [Cu(dmp)2Cl]Cl (dmp = 2,9-dimethyl-1,10-phenanthroline) were studied. The combined results from static spectroscopic measurements and conventional photochemistry, ultrafast transient absorption, and electron paramagnetic resonance spin trapping experiments strongly support blue light (λex = 427 or 470 nm)-induced Cu-Cl homolytic bond cleavage in [Cu(dmp)2Cl]+ occurring in

Aryl halides are a fundamental motif in synthetic chemistry, playing a critical role in metal-mediated cross-coupling reactions and serving as important scaffolds in drug discovery. Although thermal decarboxylative functionalization of aryl carboxylic acids has been extensively explored, the scope of existing halodecarboxylation methods remains limited, and there currently exists no unified strategy that provides access to any type of aryl halide from an aryl carboxylic acid precursor. Herein, we report a general catalytic method for direct decarboxylative halogenation of (hetero)aryl carboxylic acids via ligand-to-metal charge transfer. This strategy accommodates an exceptionally broad scope of substrates. We leverage an aryl radical intermediate toward divergent functionalization pathways: (1) atom transfer to access bromo- or iodo(hetero)arenes or (2) radical capture by copper and subsequent reductive elimination to generate chloro- or fluoro(hetero)arenes. The proposed ligand-to-metal charge transfer mechanism is supported through an array of spectroscopic studies.

Choosing the right coordination geometry for the light-induced Cu(ii)-catalyzed oxidative decarboxylation.

Searching for a connection between the two-electron redox behavior of Group-14 elements and their possible use as platforms for the photoreductive elimination of chlorine, we have studied the photochemistry of [(o-(Ph

Aryl carboxylic acids are valuable, stable, and abundant functional handles in organic synthesis. Historically, their activation with established two-electron methods requires forcing conditions, and such protocols are limited in scope. In contrast, we envisioned that copper’s ability to generate open-shell species through ligand-to-metal charge transfer (LMCT), combined with its unique capacity to act as a potential aroyloxy and aryl radical reservoir, could mediate facile light- and copper-enabled aromatic decarboxylative functionalization by mitigating undesired reactivity of radical intermediates formed during aromatic decarboxylation. We report herein a general copper-LMCT open-shell activation platform for aromatic halodecarboxylation. Catalytic decarboxylative chlorination, bromination, and iodination of diverse (hetero)aryl carboxylic acids have been achieved to provide broadly used electrophilic cross-coupling handles from widely available aromatic acid precursors. Notably, decarboxylative fluorination of aryl carboxylic acids ­– a long-standing challenge in the field of organic synthesis – is readily accessible over a wide breadth of (hetero)aryl substrates. Ultrafast transient absorption (TA) spectroscopy experiments in combination with steady-state UV-vis spectroscopy studies are consistent with the proposed copper-LMCT mechanism, supporting the mechanistic basis of this activation platform.

In this study, we investigated the electrochemical effects of Fe co-deposition in thin Ni oxo/hydroxo films in borate, termed ‘NiFe–Bi’, electrodeposited from a Ni : Fe ratio of 9 : 1, 6 : 4, and 4 : 6 in solution. The NiFe–Bi films were investigated as-deposited and after anodic conditioning, and compared to Ni–Bi without intentional Fe doping at Ni(OH)2 loading from a submonolayer to 10 layers. Fe co-deposition enhanced the oxygen evolution reaction (OER) of as-deposited NiFe–Bi films relative to as-deposited Ni–Bi; however, anodic biasing was still required to maximize catalysis. The Ni(OH)2/NiOOH redox peaks of NiFe–Bi deposited from 6 : 4 and 4 : 6 Ni : Fe were more cathodic and more reversible than Ni–Bi peaks. Anodic conditioning caused the Ni(OH)2/NiOOH redox peaks of Ni–Bi and NiFe–Bi to shift anodically but without narrowing of peak separation, different from the effects of Fe co-deposition. After anodic conditioning, the turnover frequency (TOF) for OER per Ni center for Ni–Bi and NiFe–Bi was more proportional to the Ni content within the first linear Tafel region, with a promoting effect of Fe, and the films exhibited similar Tafel slopes of 37–42 mV dec−1. With increasing overpotential however, the TOF increased more significantly at high Fe : Ni ratio and was not proportional to the Ni content, and the Tafel slopes varied while notably decreasing for some NiFe–Bi films. Electrochemical results can support a Ni active site at low overpotential, but point to possibly different roles of Fe at low versus high potential. In addition, the effect of adding Fe3+ and Al3+ to the electrolyte was studied after deposition of Ni–Bi. Adding Fe resulted in reaching almost maximum activity in a single potential scan, confirming the promoting role of Fe in Ni–Bi and providing a quick alternative to applying anodic bias for hours to increase activity, while Al in the electrolyte poisoned OER catalysis at Ni–Bi and at NiFe–Bi. In the presence of both Fe and Al ions in solution however, with their opposite effects on the OER, the Ni(OH)2/NiOOH redox peaks shifted anodically with potential scanning.

We investigate the cause of amplification of light-energy conversion when coupling a nc-TiO2 film to a TiO2 inverse opal by comparing it to an inverse TiO2 glass (i-TiO2 -g) fabricated with the exact monodisperse air-hole size as an inverse opal with a stop band at 600 nm (600-i-TiO2 -o). A significant twofold average gain in the photon-to-current conversion efficiency is measured to the red of the stop band at the 600-i-TiO2 -o/nc-TiO2 bilayer under front-wall and back-wall illumination, greater than the gain within the stop band. A smaller amplification is measured under front-wall illumination-and no gain is measured under back-wall illumination-for i-TiO2 -g/nc-TiO2 at these energies. The photonic crystal therefore causes trapping of light through the bilayer, not only within the gap but also to the red, at frequencies within its dielectric band. This light-trapping effect is found to be dependent on structural order, as a highly disordered inverse glass film with the same air-hole size and thickness does not yield the same gain. A drop in the transmission of light is measured within the same frequencies to the red of the stop band upon adding nc-TiO2 to 600-i-TiO2 -o, consistent with light trapping in the bilayer.

We report a new family of ruthenium poly-pyridyl complexes that bear tetrazolate based ligands (either bi-chelate as in T162 or tri-chelate as in T120 and T147), along with their spectroscopic, electrochemical, and theoretical characterization. Dye-sensitized solar cells (DSSCs) with these complexes show good conversion efficiencies that are highly dependent on the respective electrolyte composition especially in the case of T120 and T147, due to their low lying LUMOs when compared to N719 and T162. DSSCs based on these dyes showed superb stability under light soaking at 70 °C for 2000 h. The T120 and T147 based cells retained their initial efficiencies after the long term-stability test, while the T162 and N719 efficiencies decreased by 18% and 40%, respectively.

We report a new water soluble and stable thiolate/disulfide redox couple (T(-)/DS) and its use with a new zwitterionic and thiocyanate-free dye (T169) in a 100% aqueous electrolyte system. A DSSC incorporating T169 and the T(-)/DS showed the highest photocurrents (Jsc = 13.30 mA cm(-2)) and IPCE% (84%) values reported to date. In addition, a 2000 h long-term stability measurement was performed, where Jsc and Voc of the above mentioned DSSC stayed somehow the same except for the fill factor (FF) which decreased from 0.62 to 0.48 and consequently lowered the total efficiency (from η = 4.5% on day 1 to η = 3.3% after 2000 h).