Mn oxide as a kinetically dominant “true” catalyst for water oxidation

Nature uses an Mn cluster for water oxidation, and thus, water oxidation using Mn clusters is interesting when used in artificial water-splitting systems. An important question is whether an Mn cluster is a true catalyst for water oxidation or not. Herein, an Mn–K cluster was investigated for electrochemical water oxidation to find the true and the kinetically dominant catalyst using X-ray absorption spectroscopy, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and electrochemical methods. The experiments showed that conversion into nanosized Mn oxide occurred for the cluster, and the nanosized Mn oxides are the true catalyst for water oxidation

2-(5-Bromo-2-hydroxy­phen­yl)-1,2-dihydro­quinazolin-4(3H)-one

The asymmetric unit of the title compound, C14H11BrN2O2, contains two independent mol­ecules connected into a dimer by inter­molecular N—H⋯O hydrogen bonds involving the amine and carbonyl groups. The dimers are further connected by O—H⋯O hydrogen bonds, forming chains running parallel to the a axis, which are stabilized through π–π stacking inter­actions, with a centroid–centroid distance of 3.679 (8) Å. The dihedral angle between the two aromatic rings is 89.2 (4)°

2-[Bis(5-chloro-2-pyridylamino)methyl]pyridine monohydrate

In the title compound, the dihedral angles between the 2-amino-5-chloro­pyridyl rings and the pyridine ring are 56.26 (6)° and 78.83 (5)°; the angle between the 2-amino-5-chloro­pyridyl rings is 72.42 (5)°. The solvent water mol­ecules are linked to the organic compound by N—H⋯O, O—H⋯O, N—H⋯N and O—H⋯N hydrogen bonds. π⋯π Stacking inter­actions are also observed between the 2-amino-5-chloro­pyridyl rings (centroid⋯centroid distance = 3.243 Å)

Dopaminium perchlorate

In the title compound [systematic name: 2-(3,4-dihydroxy­phen­yl)ethanaminium perchlorate], C8H12NO2 +·ClO4 −, the cations and anions are linked into three-dimensional structure via inter­molecular N—H⋯O and O—H⋯O hydrogen bonds

Electrochemical alcohols oxidation mediated by N-hydroxyphthalimide on nickel foam surface

Alcohol to aldehyde conversion is a critical reaction in the industry. Herein, a new electrochemical method is introduced that converts 1 mmol of alcohols to aldehydes and ketones in the presence of N-hydroxyphthalimide (NHPI, 20 mol%) as a mediator; this conversion is achieved after 8.5 h at room temperature using a piece of Ni foam (1.0 cm2) and without adding an extra-base or a need for high temperature. Using this method, 10 mmol (1.08 g) of benzyl alcohol was also successfully oxidized to benzaldehyde (91%) without any by-products. This method was also used to oxidize other alcohols with high yield and selectivity. In the absence of a mediator, the surface of the nickel foam provided oxidation products at the lower yield. After the reaction was complete, nickel foam (anode) was characterized by a combination of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and spectroelectrochemistry, which pointed to the formation of nickel oxide on the surface of the electrode. On the other hand, using other electrodes such as Pt, Cu, Fe, and graphite resulted in a low yield for the alcohol to aldehyde conversion

new controversies and puzzles

Nature uses an Mn cluster for water oxidation, and thus, water oxidation using Mn clusters is interesting when used in artificial water-splitting systems. An important question is whether an Mn cluster is a true catalyst for water oxidation or not. Herein, an Mn–K cluster was investigated for electrochemical water oxidation to find the true and the kinetically dominant catalyst using X-ray absorption spectroscopy, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and electrochemical methods. The experiments showed that conversion into nanosized Mn oxide occurred for the cluster, and the nanosized Mn oxides are the true catalyst for water oxidation