A combination of cryogenic UV-vis and CD spectroscopy and transient absorption spectroscopy at ambient temperature is used to study a new class of unidirectional rotary molecular motors. Stabilization of unstable intermediates is achieved below 95 K in propane solution for the structure with the fastest rotation rate, and below this temperature measurements on the rate limiting step in the rotation cycle can be performed to obtain activation parameters. The results are compared to measurements at ambient temperature using transient absorption spectroscopy, which show that behavior of these motors is similar over the full temperature range investigated, thereby allowing a maximum rotation rate of 3 MHz at room temperature under suitable irradiation conditions.
Photoactive NiO electrodes for cathodic dye-sensitised solar cells (p-DSCs) have been prepared with thicknesses ranging between 0.43.0 µm by spray-depositing pre-formed NiO nanoparticles on fluorine-doped tin oxide (FTO) coated glass substrates. The larger thicknesses were obtained in sequential sintering steps using a conventional furnace (CS) and a newly developed rapid discharge sintering (RDS) method. The latter procedure is employed for the first time for the preparation of pDSCs. In particular, RDS represents a scalable procedure that is based on microwave-assisted plasma formation that allows the production in series of mesoporous NiO electrodes with large surface areas for p-type cell photocathodes. RDS possesses the unique feature of transmitting heat from the bulk of the system towards its outer interfaces with controlled confinement of the heating zone. The use of RDS results in a drastic reduction of processing times with respect to other deposition methods that involve heating/calcination steps with associated reduced costs in terms of energy. P1-dye sensitized NiO electrodes obtained via the RDS procedure have been tested in DSC devices and their performances have been analysed and compared with those of cathodic DSCs derived from CS-deposited samples. The largest conversion efficiencies (0.12 %) and incident photon-to-current conversion efficiencies, IPCEs, (50 %) were obtained with sintered NiO electrodes having thicknesses of ~1.5-2.0 μm. In all the devices, the photogenerated holes in NiO lived significantly longer ( h ~ 1 s) than has previously been reported for P1-sensitized NiO 2 photocathodes. In addition, P1-sensitised sintered electrodes give rise to relatively high photovoltages (up to 135 mV) when the triiodide-iodide redox couple is used.
The deoxy-myoglobin (deoxy-Mb)/carbonmonoxy-myoglobin (Mb-CO) UV-vis assay is the principal method used for quantifying the rates of CO release from CO-releasing molecules (CO-RMs) that might possess therapeutic benefits. Some issues emerge when the Mb-CO assay is utilized for testing CO-RMs with novel structures, which are comprehensively discussed here for the first time. Two methods for processing raw UV-vis spectroscopic data generated from the assay are presented in this paper.
ABSTRACT. Analogues of [Ru(bpy) 3 ]2+ were prepared in which one pyridine ligand site is substituted by a N-heterocyclic carbene (NHC) ligand, i.e. either by an imidazolylidene with a variable wingtip group R (R = Me, 3a; R = Et, 3b; R = iPr, 3c), or by a benzimidazolylidene (Me wingtip group, 3d) or by a 1,2,3-triazolylidene (Me wingtip group, 3e). All complexes were characterized spectroscopically, photophysically, and electrochemically. An increase of the size of the wingtip groups from Me to Et or iPr groups distorts the octahedral geometry (NMR spectroscopy) and curtails the reversibility of the ruthenium oxidation. NHC ligands with methyl wingtip groups display reversible ruthenium oxidation at a potential that reflects the donor properties of the NHC ligand (triazolylidene > imidazolylidene > benzimidazolylidene). The most attractive properties were measured for the triazolylidene ruthenium complex 3e, featuring the smallest HOMO-LUMO gap in the series (2.41 eV), a slightly red-shifted absorption profile, and reasonable excited-state lifetime (188 ns) when compared to [Ru(bpy) 3 ] 2+ . These features demonstrate the potential utility of triazolylidene ruthenium complexes as photosensitizers for 2 solar energy conversion.
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