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The implementation of the hydroformylation reaction for the conversion of long-chain alkenes into aldehydes still remains challenging on an industrial scale. One possible approach to overcoming this challenge is to apply tunable systems employing surfactants. Therefore, a novel process concept for the hydroformylation of long-chain alkenes to aldehydes in microemulsions is being investigated and developed at Technische Universität Berlin, Germany. To test the applicability of this concept for the hydroformylation in microemulsions on a larger scale, a miniplant has been constructed and operated. This contribution presents the proof of concept for hydroformylation in microemulsions carried out during a 200 h miniplant operation. Throughout the operation a stable aldehyde yield of 21% and a catalyst loss in the product phase below 0.1 ppm were achieved, which confirms previous lab scale findings. Additionally, solution strategies for a stable continuous operation to overcome challenges such as foaming, phase separation issues, and coalescence dynamics are discussed herein.

We investigate aqueous multiphase systems for catalytic gas/liquid reactions, namely, the rhodium-catalyzed hydroformylation of the long-chain olefin 1-dodecene. The multiphase system was formulated from 1-dodecene, water, and a nonionic surfactant, which increases the solubility between the two nonmiscible liquid phases. On the basis of these systems, we present in this paper a transfer of lab experiments (semibatch) to a successful operation of a miniplant in continuous mode. Under optimized conditions, the reaction showed turnover frequencies of ∼200 h–1 and high selectivity of 98:2 to the desired linear aldehyde. The miniplant was operated continuously for a total of 130 h. The control of the phase separation and catalyst recycling for product isolation for a long time period appeared to be challenging. Nevertheless, the separation was kept stable for over 24 h. The organic components in the product phase amounted to desired values between 95 and 99 wt %. The desired 99.99% of the catalyst remained in the aqueous catalyst phase.

Known for their stable structural and thermal properties, diamondoids and their radical cations are viable candidates as carriers for diffuse interstellar bands. 1 While previous diamondoid research has mainly focused on neutral molecules and their derivatives, little is known about their radical cations, which may form in interstellar environments by ionizing radiation. 2 We report the first experimental optical spectrum of the simplest diamondoid cation, the adamantane radical cation (C 10 H 16 + ), obtained via electronic photodissociation spectroscopy at 5 K between 310-1000 nm. The optical spectrum reveals a broad peak between 420-850 nm, assigned to the D 2 ( 2 E) ← D 0 ( 2 A 1 ) transition. This feature exhibits no vibrational structure, despite an experimental temperature below 20 K, due to lifetime broadening and/or Franck-Condon congestion. A second band system originating at 345 nm does reveal a vibrational progression and is attributed to the overlapping D 5 ( 2 A 1 )/D 6 ( 2 E) ← D 0 ( 2 A 1 ) transitions split by the Jahn-Teller effect. Comparison of the spectrum with known diffuse interstellar bands suggests that C 10 H 16 + is not likely to be a carrier. However, the strong absorption features in the UV to near IR show promise in the investigation of higher order diamondoid cations as potential candidates. 3

Cryogenic ion spectroscopy of metal–lumiflavin (M+LF) complexes at the level of vibrational resolution illustrates the large impact of alkali ions on the optical properties of this prototypical flavin molecule.

The photochemical properties of flavins depend sensitively on their environment and are strongly modified by coordination with metal ions. Herein, the electronic spectra of cold complexes of the smallest flavin molecule (lumichrome, LC, C12N4O2H10) with alkali ions (M+LC, M = Li-Cs) are measured by photodissociation in the visible range (VISPD) in a cryogenic ion trap coupled to a tandem mass spectrometer and an electrospray ionization source. The observed vibronic spectra of all ions are assigned to the optically bright S1 ← S0 (ππ*) transition of the most stable O4 isomer of M+LC by comparison with quantum chemical calculations at the PBE0/cc-pVDZ level coupled to multidimensional Franck-Condon simulations. The rich vibronic spectra indicate substantial geometry changes upon S1 excitation. Large red shifts of the S1 origins upon metal complexation and progressions in the intermolecular in-plane metal stretch and bend modes demonstrate that the strength of the metal-flavin interaction in M+LC(O4) strongly increases by S1 excitation. The stronger M+LC bond in the S1 state of M+LC(O4) is rationalized by the charge reorganization upon ππ* excitation of the LC chromophore. The computations confirm that the optical properties of LC can be strongly modulated by metalation via both the type and binding site of the metal ion.

The optical properties of flavins strongly depend on the charge and oxidation states as well as the environment. Herein, the electronic spectrum of cold protonated lumichrome, the smallest flavin molecule, is recorded by means of photodissociation in the visible range (VISPD) in a cryogenic ion trap tandem mass spectrometer coupled to an electrospray ionization source. The vibronic spectrum is assigned to the S ← S (ππ*) transition of the most stable N5-protonated isomer by comparison with quantum chemical calculations at the PBE0/cc-pVDZ level in combination with multidimensional Franck-Condon simulations. Analysis of the geometric and electronic structures of neutral and protonated lumichrome explains the large red shift of the band origin upon protonation (ΔS ∼ -6000 cm), which corresponds to the increase in proton affinity upon S excitation as a result of charge transfer. N5 protonation greatly modifies the structure of the central pyrazine ring of the chromophore. The orbitals involved in S ← S excitation include an important fraction of the probability at the central ring and they are, hence, largely influenced by the positive charge of the attached proton. The rich vibronic spectrum indicates the large geometry change upon S excitation. This combined experimental and computational approach is shown to be suitable to determine the optical properties of flavins as a function of oxidation, protonation, metalation, and microsolvation state.

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