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This article describes a density functional theory (DFT) study to explore a bio‐inspired NiFe complex known for its experimental activity in electro‐reducing CO2 to CH4 when adsorbed on graphite. The coordination properties of the complex are investigated in isolated form and when physisorbed on a graphene surface. A comparative analysis of DFT approaches for surface modeling is conducted, utilizing either a finite graphene flake or a periodic carbon surface. Results reveal that the finite model effectively preserves all crucial properties. By examining predicted structures arising from CO2 insertion within the mono‐reduced NiFe species, whether isolated or adsorbed on the graphene flake, a potential species for subsequent electro‐reduction steps is proposed. Notably, the DFT study highlights two positive effects of complex adsorption: facile electron transfers between graphene and the complex, finely regulated by the complex state, and a lowering of the thermodynamic demand for CO2 insertion. [ABSTRACT FROM AUTHOR]

Nitrene transfer reactions have emerged as one of the most powerful and versatile ways to insert an amine function to various kinds of hydrocarbon substrates. However, the mechanisms of nitrene generation have not been studied in depth albeit their formation is taken for granted in most cases without definitive evidence of their occurrence. In the present work, we compare the generation of tosylimido iron species and NTs transfer from FeII and FeIII precursors where the metal is embedded in a tetracarbene macrocycle. Catalytic nitrene transfer to reference substrates (thioanisole, styrene, ethylbenzene and cyclohexane) revealed that the same active species was at play, irrespective of the ferrous versus ferric nature of the precursor. Through combination of spectroscopic (UV‐visible, Mössbauer), ESI‐MS and DFT studies, an FeIV tosylimido species was identified as the catalytically active species and was characterized spectroscopically and computationally. Whereas its formation from the FeII precursor was expected by a two‐electron oxidative addition, its formation from an FeIII precursor was unprecedented. Thanks to a combination of spectroscopic (UV‐visible, EPR, Hyscore and Mössbauer), ESI‐MS and DFT studies, we found that, when starting from the FeIII precursor, an FeIII tosyliodinane adduct was formed and decomposed into an FeV tosylimido species which generated the catalytically active FeIV tosylimide through a comproportionation process with the FeIII precursor. [ABSTRACT FROM AUTHOR]

It is recently demonstrated that diaryl‐naphthopyran photochromic dyes are efficient for sensitization of TiO2 mesoporous electrodes, thus allowing the fabrication of photochromo‐voltaic cells that can self‐adapt their absorption of light and their generation of electricity with the light intensity. Herein, the synthesis and characterization of two photochromic dyes based on a diaryl‐naphthopyran core, NPI‐ThPh and NPIFuPh, for use in dye sensitized solar cells is reported. Compared to the reference dye NPI, the molecules vary by the nature of the spacer, a thiophene or a furan, connecting the photochromic unit and the anchoring function. It was found that swapping a phenyl for a thiophene or a furan leads to an improvement of the absorption properties of the molecules, both in solution and after grafting on TiO2 electrodes, however their photochromic process becomes not fully reversible. Despite better absorption in the visible range, the new dyes show poorer photochromic and photovoltaic properties in devices compared to NPI. Thanks to UV–Vis spectroscopy, theoretical modelling, electrical characterization of the cells, and impedance spectroscopy, the factors limiting their performances have been unraveled. This study contributes to better understand the connection between photochromic and photovoltaic properties, which is key to develop better performing molecules of this class. [ABSTRACT FROM AUTHOR]

This article describes a density functional theory (DFT) study to explore a bio-inspired NiFe complex known for its experimental activity in electro-reducing CO 2 to CH 4 when adsorbed on graphite. The coordination properties of the complex are investigated in isolated form and when physisorbed on a graphene surface. A comparative analysis of DFT approaches for surface modeling is conducted, utilizing either a finite graphene flake or a periodic carbon surface. Results reveal that the finite model effectively preserves all crucial properties. By examining predicted structures arising from CO 2 insertion within the mono-reduced NiFe species, whether isolated or adsorbed on the graphene flake, a potential species for subsequent electro-reduction steps is proposed. Notably, the DFT study highlights two positive effects of complex adsorption: facile electron transfers between graphene and the complex, finely regulated by the complex state, and a lowering of the thermodynamic demand for CO 2 insertion., (© 2024 Wiley Periodicals LLC.)

The As III binding of two NTA-based tripodal pseudopeptides, possessing three cysteine (ligand L 1 ) or d-penicillamine residues (ligand L 2 ) as potential coordinating groups for soft semimetals or metal ions, was studied by experimental (UV, CD, NMR, and ESI-MS) and theoretical (DFT) methods. All of the experimental data, obtained with the variation of the As III :ligand concentration ratios or pH values in some instances, evidence the exclusive formation of species with an AsS 3 -type coordination mode. The UV-monitored titration of the ligands with arsenous acid at pH = 7.0 provided an absorbance data set that allowed for the determination of apparent stability constants of the forming species. The obtained stabilities (log K ' = 5.26 (As L 1 ) and log K ' = 3.04 (As L 2 )) reflect high affinities, especially for the sterically less restricted cysteine derivative. DFT calculated structures correlate well with the spectroscopic results and, in line with the 1 H NMR data, indicate a preference for the all- endo conformers resembling the As III environment at the semimetal binding sites in various metalloproteins.

Nitrene transfer reactions have emerged as one of the most powerful and versatile ways to insert an amine function to various kinds of hydrocarbon substrates. However, the mechanisms of nitrene generation have not been studied in depth albeit their formation is taken for granted in most cases without definitive evidence of their occurrence. In the present work, we compare the generation of tosylimido iron species and NTs transfer from Fe II and Fe III precursors where the metal is embedded in a tetracarbene macrocycle. Catalytic nitrene transfer to reference substrates (thioanisole, styrene, ethylbenzene and cyclohexane) revealed that the same active species was at play, irrespective of the ferrous versus ferric nature of the precursor. Through combination of spectroscopic (UV-visible, Mössbauer), ESI-MS and DFT studies, an Fe IV tosylimido species was identified as the catalytically active species and was characterized spectroscopically and computationally. Whereas its formation from the Fe II precursor was expected by a two-electron oxidative addition, its formation from an Fe III precursor was unprecedented. Thanks to a combination of spectroscopic (UV-visible, EPR, Hyscore and Mössbauer), ESI-MS and DFT studies, we found that, when starting from the Fe III precursor, an Fe III tosyliodinane adduct was formed and decomposed into an Fe V tosylimido species which generated the catalytically active Fe IV tosylimide through a comproportionation process with the Fe III precursor., (© 2022 Wiley-VCH GmbH.)