Abstract
A series of [Re(N^N)(CO)3(Cl)] (N^N = diimine) complexes based on 4-(pyrid-2-yl)-1,2,3-triazole (1), 1-benzyl-4-(pyrimidin-2-yl)-1,2,3-triazole (2), and 1-benzyl-4-(pyrazin-2-yl)-1,2,3-triazole (3) diimine ligands were prepared and their photophysical and electrochemical properties were characterized. The ligand-based reduction wave is shown to be highly sensitive to the nature of the triazole-based ligand, with the peak potential shifting by up to 600 mV toward more positive potential from 1 to 3. All three complexes are phosphorescent in solution at room temperature with λmax ranging from 540 nm (1) to 638 nm (3). Interestingly, the complexes appear to show inverted energy-gap law behaviour (τ = 43 ns for 1 versus 92 ns for 3), which is tentatively interpreted as reduced thermal accessibility of metal-centred (3MC) states from photoexcited metal to ligand charge transfer (3MLCT) states upon stabilisation of the N^N-centred lowest unoccupied molecular orbital (LUMO). The photophysical characterisation, supported by computational data, demonstrated a progressive stabilization of the LUMO from complex 1 to 3, which results in a narrowing of the HOMO–LUMO energy gap (HOMO = highest occupied molecular orbital) across the series and, correspondingly, red-shifted electronic absorption and photoluminescence spectra. The two complexes bearing pyridyl (1) and pyrimidyl (2) moieties, respectively, showed a modest ability to catalyse the electroreduction of CO2, with a peak potential at ca. −2.3 V versus Fc/Fc+. The catalytic wave that is observed in the cyclic voltammograms is slightly enhanced by the addition of water as a proton source.
Highlights
The demand for energy by an ever-growing population has seen atmospheric levels of CO2 rise to levels unprecedented in human history with the effects of anthropogenic climate change already evident
On On the basis of our in triazole-based coordination chemistry, we report the synthesis, the basis of interest our interest in triazole-based coordination chemistry, we report the synthesis, characterisation, and photophysical properties of thenew new rhenium(I)
A new series of rhenium(I) triazole tricarbonyl complexes were prepared and studied for their photophysical behaviour and their ability to catalyse the electroreduction of CO2
Summary
The demand for energy by an ever-growing population has seen atmospheric levels of CO2 rise to levels unprecedented in human history with the effects of anthropogenic climate change already evident. As part of an attempt to combat this, significant effort has been put into the development of catalytic systems for the photochemical and/or electrochemical conversion of CO2 into useful chemical feedstocks. The development of novel catalytic systems for these applications has involved significant efforts in ligand design in attempts to improve efficiency. Exploring facile routes to Inorganics 2020, 8, x ligand synthesis that are robust and versatile could enable access to a wide expanse of chemical designs. In this regard, the copper(I) catalysed 1,3-dipolar cycloaddition of alkynes and azides to
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