Vitamin B12 -Photocatalyzed Cyclopropanation of Electron-Deficient Alkenes Using Dichloromethane as the Methylene Source.

The cyclopropyl group is of great importance in medicinal chemistry, as it can be leveraged to influence a range of pharmaceutical properties in drug molecules. This report describes a Vitamin B12 -photocatalyzed approach for the cyclopropanation of electron-deficient alkenes using dichloromethane (CH2 Cl2 ) as the methylene source. The reaction proceeds in good to excellent yields under mild conditions, has excellent functional group compatibility, and is highly chemoselective. The scope could also be extended to the preparation of D2 -cyclopropyl and methyl-substituted cyclopropyl adducts starting from CD2 Cl2 and 1,1-dichloroethane, respectively.

Recent Advances in Employing Catalytic Donors and Acceptors in Electron Donor-Acceptor Complex Photochemistry.

Electron donor-acceptor (EDA) complexes provide a means to initiate radical reactions under visible light irradiation using substrates that do not absorb visible light individually. Catalytic approaches to complex formation are vital for advancing this synthetic strategy as it decouples the complexation and photogeneration of radicals from substrate functionalization, a limitation inherent to stoichiometric approaches that restricts structural diversity. This Synopsis highlights recent developments in EDA complex photochemistry in which either the donor or acceptor are employed catalytically.

Synthesis and crystal structure of catena-poly[[tetra-µ-acetato-copper(II)]-µ-6-eth-oxy-N 2,N 4-bis-[2-(pyridin-2-yl)eth-yl]-1,3,5-triazine-2,4-di-amine].

The title compound, [Cu2(C19H23N7O)(C2H3O2)4] n , was obtained via reaction of copper(II) acetate with the coordinating ligand, 6-eth-oxy-N 2,N 4-bis-[2-(pyridin-2-yl)eth-yl]-1,3,5-triazine-2,4-di-amine. The crystallized product adopts the monoclinic P21/c space group. The metal core exhibits a paddle-wheel structure typical for dicopper tetra-acetate units, with triazine and pyridyl nitro-gen atoms from different ligands coordinating to the two axial positions of the paddle wheel in an asymmetric manner. This forms a coordination polymer with the segments of the polymer created by the c-glide of the P21/c setting of the space group. The resulting chains running along the c-axis direction are held together by intra-molecular N-H⋯O hydrogen bonding. These chains are further packed by dispersion forces, producing an extended three-dimensional structure.

Fe(III)-polyuronic acid photochemistry: radical chemistry in natural polysaccharide.

The photochemistry of Fe(III) coordinated to natural uronate-containing polysaccharides has been investigated quantitatively in aqueous solution. It is demonstrated that the photoreduction of the coordinated Fe(III) to Fe(II) and oxidative decarboxylation occurs in a variety of uronate-containing polysaccharides. The photochemistry of the Fe(III)-polyuronic acid system generated a radical species during the reaction which was studied using the spin trapping technique. The identity of the radical species from this reaction was confirmed as CO2•- indicating that both bond cleavage of the carboxylate and oxidative decarboxylation after ligand to metal charge transfer radical reactions may be taking place upon irradiation. Degradation of the polyuronic acid chain was investigated with dynamic light scattering, showing a decrease in the hydrodynamic radius of the polymer assemblies in solution after light irradiation that correlates with the Fe(II) generation. A decrease in viscosity of Fe(IIII)-alginate after light irradiation was also observed. Additionally, the photochemical reaction was investigated in plant root tissue (parsnip) demonstrating that Fe(III) coordination in these natural materials leads to photoreactivity that degrades the pectin component. These results highlight that this Fe(III)-polyuronic acid can occur in many natural systems and may play a role in biogeochemical cycling of iron and ferrous iron generation in plants with significant polyuronic acid content.

2D Arrays of Organic Qubit Candidates Embedded into a Pillared-Paddlewheel Metal-Organic Framework.

The creation of ordered arrays of qubits that can be interfaced from the macroscopic world is an essential challenge for the development of quantum information science (QIS) currently being explored by chemists and physicists. Recently, porous metal-organic frameworks (MOFs) have arisen as a promising solution to this challenge as they allow for atomic-level spatial control of the molecular subunits that comprise their structures. To date, no organic qubit candidates have been installed in MOFs despite their structural variability and promise for creating systems with adjustable properties. With this in mind, we report the development of a pillared-paddlewheel-type MOF structure that contains 4,7-bis(2-(4-pyridyl)-ethynyl) isoindoline N-oxide and 1,4-bis(2-(4-pyridyl)-ethynyl)-benzene pillars that connect 2D sheets of 9,10-dicarboxytriptycene struts and Zn2(CO2)4 secondary binding units. The design allows for the formation of ordered arrays of reorienting isoindoline nitroxide spin centers with variable concentrations through the use of mixed crystals containing the secondary 1,4-phenylene pillar. While solvent removal causes decomposition of the MOF, magnetometry measurements of the MOF containing only N-oxide pillars demonstrated magnetic interactions with changes in magnetic moment as a function of temperature between 150 and 5 K. Variable-temperature electron paramagnetic resonance (EPR) experiments show that the nitroxides couple to one another at distances as long as 2 nm, but act independently at distances of 10 nm or more. We also use a specially designed resonance microwave cavity to measure the face-dependent EPR spectra of the crystal, demonstrating that it has anisotropic interactions with impingent electromagnetic radiation.