Photon Equivalents as a Parameter for Scaling Photoredox Reactions in Flow: Translation of Photocatalytic C−N Cross‐Coupling from Lab Scale to Multikilogram Scale

With the development of new photocatalytic methods over recent decades, the translation of these chemical reactions to industrial‐production scales using continuous‐flow reactors has become a topic of increasing interest. In this context, we describe our studies toward elucidating an empirically derived parameter for scaling photocatalytic reactions in flow. By evaluating the performance of a photocatalytic C?N cross‐coupling reaction across multiple reactor sizes and geometries, it was demonstrated that expressing product yield as a function of the absorbed photon equivalents provides a predictive, empirical scaling parameter. Through the use of this scaling factor and characterization of the photonic flux within each reactor, the cross‐coupling was scaled successfully from the milligram scale in batch to a multi‐kilogram reaction in flow.     

Symmetric,Unsymmetrical, and Asymmetric [7]‐, [10]‐, and [13]Helicenes

Fully aromatic helicenes with more than one pitch‐length are illustrious synthetic targets with potential applications in advanced optical devices and nano‐electronics. The task of extending the length of fully conjugated helicenes past one pitch length is challenging. Now, the synthesis of a series of azaoxa[7]‐, [10]‐, and [13]helicenes is described. The synthesis is based on iterative oxidative furan formation between 3,6‐dihydroxycarbazoles and/or 2‐naphthols. The flexibility of the presented method allows the convenient and scalable synthesis of symmetric, unsymmetrical, and asymmetric homo‐chiral structures. The [13]helicenes can be synthetically functionalized both at the termini and the periphery. The full range of helicenes were characterized using NMR and optical spectroscopy (UV/Vis, fluorescence, and CD) along with single‐crystal X‐ray crystallography. The enantiomers of the [13]helicenes are the longest optically pure helicenes isolated to date.     

161Dy Time‐Domain Synchrotron Mössbauer Spectroscopy for Investigating Single‐Molecule Magnets Incorporating Dy Ions

Time‐domain synchrotron Mössbauer spectroscopy (SMS) based on the Mössbauer effect of ¹⁶¹Dy has been used to investigate the magnetic properties of a Dy^III‐based single‐molecule magnet (SMM). The magnetic hyperfine field of [Dy(Cy₃PO)₂(H₂O)₅]Br₃?2 (Cy₃PO)?2 H₂O?2 EtOH is with B₀=582.3(5) T significantly larger than that of the free‐ion Dy^III with a ⁶H_15/2 ground state. This difference is attributed to the influence of the coordinating ligands on the Fermi contact interaction between the s and 4f electrons of the Dy^III ion. This study demonstrates that ¹⁶¹Dy SMS is an effective local probe of the influence of the coordinating ligands on the magnetic structure of Dy‐containing compounds.     

A Structural View on Medicinal Chemistry Strategies against Drug Resistance

The natural phenomenon of drug resistance is a widespread issue that hampers the performance of drugs in many major clinical indications. Antibacterial and antifungal drugs are affected, as well as compounds for the treatment of cancer, viral infections, or parasitic diseases. Despite the very diverse set of biological targets and organisms involved in the development of drug resistance, the underlying molecular mechanisms have been identified to understand the emergence of resistance and to overcome this detrimental process. Detailed structural information on the root causes for drug resistance is nowadays frequently available, so next‐generation drugs can be designed that are anticipated to suffer less from resistance. This knowledge‐based approach is essential for fighting the inevitable occurrence of drug resistance.     

Monomeric Copper(II) Sites Supported on Alumina Selectively Convert Methane to Methanol

Monomeric Cu^II sites supported on alumina, prepared using surface organometallic chemistry, convert CH₄ to CH₃OH selectively. This reaction takes place by formation of CH₃O surface species with the concomitant reduction of two monomeric Cu^II sites to Cu^I, according to mass balance analysis, infrared, solid‐state nuclear magnetic resonance, X‐ray absorption, and electron paramagnetic resonance spectroscopy studies. This material contains a significant fraction of Cu active sites (22 %) and displays a selectivity for CH₃OH exceeding 83 %, based on the number of electrons involved in the transformation. These alumina‐supported Cu^II sites reveal that C?H bond activation, along with the formation of CH₃O‐ surface species, can occur on pairs of proximal monomeric Cu^II sites in a short reaction time.     

K6In2Q6 (Q = S,Se, Te): Missing Links in the Series of Alkali Chalcogenido Ditrielates(III)

The chalcogenido indates K₆In₂Q₆ (Q = S, Se, Te) were synthesized from melts of the pure elements at a maximum temperature of 700 °C. All three potassium salts contain dinuclear units [In₂Q₆]^6– of two edge-sharing [InQ₄] tetrahedra. The sulfido and the selenido indate are isotypic and crystallize in the K₆Mn₂O₆-type structure [monoclinic, space group P2₁/c, a = 784.32(9)/809.32(3), b = 1274.58(14)/1322.37(4), c = 836.48(9)/870.53(3) pm, β = 97.900(2)/97.5877(8)°, Z = 2, R₁ = 0.0123/0.0109; for Q = S/Se]. The tellurido indate K₆In₂Te₆ crystallizes in a new orthorhombic structure type [space group Pnma, a = 1793.70(12), b = 1491.55(11), c = 837.40(6) pm, Z = 4, R₁ = 0.0157]. In this structure, the telluride anions form a hexagonal close packing, in which K⁺ cations occupy all octahedral voids; the In³⁺ ions take 1/6 (but always adjacent) tetrahedral voids. This structure-chemical relation to the h.c.p. packing, which is similarly found for most of the sodium dimetallates (e.g. Na₆Fe₂S₆), is substantiated by a full crystallographic group-subgroup tree. The crystal chemistry of the new indates is discussed and compared with that of alkali chalcogenido metallates(III) of Fe, Al and Ga containing [M₂Q₆]^6– dimers, which overall form as many as ten different structure types. DFT band structure calculations of the three title compounds exhibit bandgaps, which continuously decrease from the S to the Te compound and which are also in accordance with the pale yellow (S), bright yellow (Se) and red-brown (Te) color of the compounds. The chemical bonding in the salts and within the metallate anion is discussed on the basis of the partial DOS and a Bader analysis of the calculated electron density.     

Stereoselective preparation of mono- and bis-derivatives of pentacyclo[6.3.0.02,6.03,10.05,9] undecane (D 3-trishomocubane)

The rearrangement of easily accessible Cookson’s diketone with chlorosulfonic acid in chloroform followed by the acidic hydrolysis gave 6-chloro-7-hydroxy-dichloropentacyclo[6.3.0.0^2,6.0^3,10.0^5,9]undecane-4-one, whose syn-stereochemistry was assigned through the X-ray crystal structure analysis. This key structure was used for the stereoselective synthesis of the D ₃-trishomocubane derivatives as well as for the preparation of potential drugs bearing hydroxy- and amino-functional groups. A new multigram preparative synthesis of D ₃-trishomocubane was developed.      

Physical properties and inclusion interactions of new stilbazolium salts: experimental versus theoretical study

The experimental and theoretical spectroscopic and spectrometric elucidation in solid-state and gas-phase on the interacting ionic species of applied oriented synthetic derivatives on the base of the stilbazolium salts as molecular template was reported. The correlation between the molecular structure, and vibrational properties within THz-regime (10-0.3 THz) was performed. The collective vibrations, and gas-phase stabilized ionic species were comprehensive studied by the Raman spectroscopy and matrix-assisted laser desorption/ionization mass spectrometry, using the embedded organic dyes in host matrixes. The performed solid-state quantum chemical calculations contributed to further understanding of the nature of the guest–host interacting systems as well as to explain the observed optical phenomena within the THz-region.     

Antiferromagnetic interactions in the quarter-filled organic conductor (EDO-TTF)2PF6

The ground state electronic structure of the high-temperature (HT) and the low-temperature (LT) phases of (EDO-TTF)(2)PF(6) is investigated using the embedded cluster approach in combination with the density functional method designed to describe the strong non-dynamic electron correlation. It is found that, in the HT phase, the unpaired electron spins located on pairs of neighbouring EDO-TTF molecules are antiferromagnetically coupled along the stacking direction with the Heisenberg exchange integral J = -655 cm(-1). In the LT phase, the unpaired spins located on the cationic EDO-TTF molecules are coupled antiferromagnetically with J values strongly alternating along the stacking axis of the crystal thus rendering it diamagnetic. The parameters of the extended Hubbard model are evaluated and the conductance properties of the two phases are estimated using these parameters. It is suggested to investigate the charge and spin excitations in the two phases of (EDO-TTF)(2)PF(6) with the use of angle-resolved photoemission spectroscopy.