This article describes the construction of a novel optically transparent thin-layer electrochemical (OTTLE) cell for IR and UV-Vis spectroelectrochemical experiments at variable temperature. The cell has a three-electrode set melt-sealed into a smooth polyethylene spacer which is sandwiched between two CaF2 windows. The width of this spacer (0.18–0.20 mm) defines the thickness of the thin solution layer. The whole electrode assembly is housed in a thermostated Cu block of the OTTLE cell which fits into a double-walled nitrogen-bath cryostat. The experimental setup permits relatively fast electrolysis within the tested temperature range of 295 to 173 K under strictly anaerobic conditions and protection of light-sensitive compounds. Other important merits of the cell design include lack of leakage, facile cleaning, almost negligible variation of the preset temperature, and facile manipulation in the course of the experiments. The applicability of the variable-temperature IR/UV-Vis OTTLE cell is demonstrated by stabilization of a few electrogenerated carbonyl complexes of Mn(I) and Ru(II) with 3,5-di- tert. butyl-1,2-benzo(semi)quinone (DB(S)Q) and N, N′-diisopropyl-1,4-diaza-1,3-butadiene (iPr-DAB) ligands, respectively, at appropriately low temperatures.
Reaction of the dinuclear complex [{Rh(CO)2}2(μ-Cl)2] with an α-diimine ligand, 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (iPr2Ph-bian), produces square-planar [RhCl(CO)(iPr2Ph-bian)]. For the first time, 2:1 and 1:1 α-diimine/dimer reactions yielded the same product. The rigidity of iPr2Ph-bian together with its flexible electronic properties and steric requirements of the 2,6-diisopropyl substituents on the benzene rings allow rapid closure of a chelate bond and replacement of a CO ligand instead of chloride. A resonance Raman study of [RhCl(CO)(iPr2Ph-bian)] has revealed a predominant Rh-to-bian charge transfer (MLCT) character of electronic transitions in the visible spectral region. The stabilisation of [RhCl(CO)(iPr2Ph-bian)] in lower oxidation states by the π-acceptor iPr2Ph-bian ligand was investigated in situ by UV-VIS, IR and EPR spectroelectrochemistry at variable temperatures. The construction of the novel UV-VIS-NIR-IR low-temperature OTTLE cell used in these studies is described in the last part of the paper.
An optically transparent thin-layer electrochemical cell for the study of vibrational circular dichroism of chiral redox-active molecules Domingos, S.R.; Luyten, H.; van Anrooij, F.; Sanders, H. J.; Bakker, B.H.; Buma, W.J.; Hartl, F.; Woutersen, S.
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Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. An optically transparent thin-layer electrochemical (OTTLE) cell with a locally extended optical path has been developed in order to perform vibrational circular dichroism (VCD) spectroscopy on chiral molecules prepared in specific oxidation states by means of electrochemical reduction or oxidation. The new design of the electrochemical cell successfully addresses the technical challenges involved in achieving sufficient infrared absorption. The VCD-OTTLE cell proves to be a valuable tool for the investigation of chiral redox-active molecules.
The construction of a special cryogenic cell for spectroscopic and photochemical measurements in liquefied noble gases under pressure is described. The inner (sample) cell, withstanding a pressure of at least 700 psi, has no high-vacuum around it. It has two crossed IR and UV-visible optical pathways of 30 mm. The usefulness of these noble gases in vibrational spectroscopy is demonstrated for the following transition metal carbonyls, dissolved in liquid xenon (=LXe, pressure <150 psi, 170 < T < 240 K): [W(CO)6], [Mn2(CO)10l, and [Co2(CO)8]. The great advantage of LXe is its complete transparency over a wide spectral range. The limited solubility of many complexes in LXe in comparison with “normal” solvents is often compensated by the long optical pathway of the cell. Because of its complete inertness, reactive intermediates and products of photochemical reactions can be stabilized in LXe, even at moderate temperatures. The photochemical reaction is described of [W(CO)6] with a l,4-diaza-l,3-butadiene (=R-DAB; RN=CHCH=NR) ligand. During this reaction a photoproduct is identified as a stable complex which is so unstable in normal solvents that it can only be observed with rapid-scan FT-IR spectroscopy.
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