The first di-protonated [FeFe] hydrogenase model relevant to key intermediates in catalytic hydrogen production is reported. The complex bearing the S-proton and Fe-hydride is structurally and spectroscopically characterized as well as studied by DFT calculations. The results show that the thiolate sulfur can accept protons during the catalytic routes.

Both the reduced and the protonated states of diiron dithiolate complexes, which are key intermediate species for the electrocatalytic production of hydrogen, have been spectroscopically and theoretically investigated in this study. Five important states in the process of H 2 evolution have been characterized. In the presence of a superacid, protonation occurs onto the Fe−Fe vector of [(μ-xdt)Fe 2 (CO) 6 ] (xdt: pdt, 1,3-propanedithiolate; edt, 1,2-ethanedithiolate; bdt, 1,2-benzenedithiolate) to yield the cationic μ-H species (the C state). A single reduction at 193 K leads to the neutral species (the CE state), with similar structures for the pdt and edt bridgeheads. The CE species of the bdt analogue is unstable under the same conditions. An open structure resulting from the rupture of one Fe−S bond is suggested by DFT calculations. Subsequently, a second reduction induces a dramatic structural rearrangement in which the CEE state possesses an open structure exhibiting a μ-H and a μ-CO group. Protonation onto the terminal sulfur site of the CEE state affords the CEEC state, which readily converts to the parent hexacarbonyl complex accompanied by the liberation of H 2 at higher temperatures. In the presence of excess acid, the CEECC state is achieved and the third proton is coordinated to the Fe center. The S-proton and Fe-hydride have been characterized by 1 H and 2 D NMR spectroscopy. Electrocatalytic hydrogen production involving the CEEC and CEECC states has been investigated by DFT calculations. In combination with the spectroscopic results, this information allows us to construct the possible catalytic routes and study the plausible role of the triply protonated species least explored in biomimetic catalysis.

Divided wall columns (DWCs) can save energy and capital costs compared with traditional distillation columns; however, the design of DWCs is more difficult because there are more degrees of freedom. This paper describes a novel short-cut method that can be used to rapidly determine near-optimal values of important design parameters, including the reflux ratio, number of stages in all sections, and split liquid and vapor ratios for the three most common types of DWCs. The method is based on the development of a rational and efficient net flow model and the application of the methods of Fenske, Underwood, and Gilliland and the Kirkbride equation. The method is applied to two real systems, and the results are compared with results from rigorous simulations and optimization. The results show that the shortcut method leads to a process similar to a feasible actual process, and the total annual cost (TAC) based on the design method is close to the minimum (optimum) total annual cost. The results also show that the method also provides good initial values for rigorous optimization. The method is also applied to a fictitious process consisting of three components with constant relative volatilities, for different values of the ease of separation index (ESI), overall split difficulty, and feed composition. The results indicate that the method works well for a variety of process conditions and that the minimum vapor flow rate is a good surrogate for the total cost of process operation.

Light triggers the formation of HNO from a metal− nitrosyl species, facilitated by an intramolecular pendant thiol proton. Two {FeNO} 6 complexes (the Enemark−Felthan notation), [Fe(NO)( TMS PS2)( TMS PS2H)] (1, TMS PS2H 2 = 2,2′dimercapto-3,3′-bis(trimethylsilyl)diphenyl)phenylphosphine; H is a dissociable proton) with a pendant thiol and [Fe(NO)-( TMS PS2)( TMS PS2CH 3 )] (2) bearing a pendant thioether, are spectroscopically and structurally characterized. Both complexes are highly sensitive to visible light. Upon photolysis, complex 2 undergoes NO dissociation to yield a mononuclear Fe(III) complex, [Fe( TMS PS2)( TMS PS2CH 3 )] (3). In contrast, the pendant SH of 1 can act as a trap for the departing NO radical upon irradiation, resulting in the formation of an intermediate A with an intramolecular [SH•••ON−Fe] interaction. As suggested by computational results (density functional theory), the NO stretching frequency (ν NO ) is sensitive to the intramolecular interaction between the pendant ligand and the iron-bound NO, and a shift of ν NO from 1833 (1) to 1823 cm −1 (A) is observed experimentally. Subsequent photolysis of the intermediate A results in HNO production and a thiyl group that then coordinates to the Fe center for the formation of [Fe( TMS PS2) 2 ] (4). In contrast with the common acid−base coupling pathway, the HNO is not voluntarily yielded from 1 but rather is generated by the photopromoted pathway. The photogenerated HNO can further react with [Mn III ( TMS PS3)(DABCO)] ( TMS PS3H 3 = (2,2′2′′-trimercapto-3,3′,3′′tris(trimethylsilyl)triphenylphosphine; DABCO = 1,4-diazabicyclo[2.2.2]octane) in organic media to yield anionic [Mn(NO)-( TMS PS3)] − (5 − ) with a {MnNO} 6 electronic configuration, whereas [Mn III ( TMS PS3)(DABCO)] reacts with NO gas for the formation of a {MnNO} 5 species, [Mn(NO)( TMS PS3)] (6). Effective differentiation of the formation of HNO from complex 1 with the pendant SH versus NO from 2 with the pendant SMe is achieved by the employment of [Mn III ( TMS PS3)(DABCO)].

Hexa-peri-hexabenzocoronene (HBC) derivatives tend to form discotic columnar liquid crystalline (DCLC) phases capable of charge transport and anisotropic photoresponses. However, their noncovalently bonded molecular assemblies are prone to decompose upon heat or organic solvent treatment. Here we designed a series of cross-linkable HBC derivatives in which the HBC core was tethered with three diacetylene-containing side chains and three alkyl chains in alternating positions. Both film and solution states of these derivatives were found to aggregate into columns and undergo polymerization/cross-linking reaction by either UV-irradiation or thermal treatment, presumably due to reaction between the diacetylenic units. The DCLC characteristics and polymerization/cross-linking reactions have been investigated by differential scanning calorimetry, powder X-ray diffraction, Raman spectroscopy, and UV–vis spectroscopy. The optoelectronic measurements of the films were performed using the time-resolved microwave conductivity technique, which gave the largest signal for one of the derivatives, HBC-1,3,5-C8,9-DA-C4, indicating its potential use as an optoelectronic material.

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A direct catalytic asymmetric functionalization of 2-methyl-3-nitroindoles using organocatalysis has been developed.