Noncovalent carbon bonding, a recently explored σ-hole interaction, was hitherto supposed to be a weak and structure-guided interaction. Here, its role in the intramolecular stabilization of the cis conformation of the amide moiety in acylhydrazones is described. The calculations reveal an electron donation from the lone pair of the nitrogen atom to the empty antibonding C-N orbital [LP(N)→BD*(C-N)] with a concomitant stabilization energy of E(2) =1.2 kcal mol-1 .
Pyridinemethanol-carboxylate esters form octahedral complexes with Zn(NO3 )2 in aqueous DMF that subsequently undergo hydrolysis at elevated temperatures to form metal-carboxylate zwitterions. In situ deprotonation of the hydroxy group leads to thermally robust, neutral MOFs. This stepwise synthesis can be controlled by temperature and is made possible by the subtle difference in reactivity of the functional groups.
This month's cover is dedicated to the golden anniversary of Singapore by the collaborating groups of Wen-Hua Zhang of the IMRE, Singapore, and T. S. Andy Hor of the NUS, Singapore, and two more groups from Monash University, Malaysia, and Soochow University, P. R. China. In the cover picture the number "50" commemorates the 50th anniversary of Singapore, the Lion City. The photo on the top-right corner shows the modern skyline of Singapore. Underneath are the structures described in this article. Read the full text of the article at 10.1002/cplu.201500134.
A novel tetranuclear copper-based water oxidation catalyst was designed and synthesized by using a new multinucleating ligand containing two proton dissociation sites, 1,3-bis(6-hydroxy-2-pyridyl)-1H-pyrazole. The copper complex showed electrocatalytic activity for water oxidation reactions under aqueous basic conditions (pH 12.5) with an overpotential of approximately 500 mV. UV/Vis absorption and energy-dispersive X-ray (EDX) spectroscopic techniques coupled with electrochemical analyses of the catalyst system strongly suggest that the tetranuclear copper complex works as a homogeneous system under the conditions used. The results described here demonstrate the utility of a discrete tetranuclear copper complex in water oxidation reactions.
The incorporation of noble metals with metal-organic frameworks (MOFs) are conducive to the simultaneous electrochemical detection of analytes owing to multiple accessible reaction sites. Herein, Au@Cu-metal organic framework (Au@Cu-MOF) is successfully synthesized and modified as a screen-printed carbon electrode (SPCE), which serves as an excellent electrocatalyst for the oxidation of dopamine (DA) and uric acid (UA). The sensor shows a linear range from 10 μM to 1000 μM, with sensitivity and detection limit of 0.231 μA μM-1 cm-2 and 3.40 μM for DA, and 0.275 μA μM-1 cm-2 and 10.36 μM for UA. Au@Cu-MOF could realize the individual and simultaneous electrochemical sensing of DA and UA, with distinguishable oxidation peak potentials. Moreover, it exhibits reproducibility, repeatability, and stability. Ultimately, the sensor provides an avenue for an ultrasensitive label-free electrochemical detection of DA and UA.