Metal-Organic Frameworks via Emissive Metal-Carboxylate Zwitterion Intermediates.

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.

Metal-Organic Frameworks via Emissive Metal-Carboxylate Zwitterion Intermediates.

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.

Synthesis and structure of a ferric complex of 2,6-di(1H-pyrazol-3-yl)pyridine and its excellent performance in the redox-controlled living ring-opening polymerization of ε-caprolactone.

The reaction of FeCl3 with a pincer ligand, 2,6-di(1H-pyrazol-3-yl)pyridine (bppyH2), produced a mononuclear Fe(III) complex [Fe(bppyH2)Cl3] (1), which could be reduced to the corresponding Fe(II) dichloride complex [Fe(bppyH2)Cl2] (2) by suitable reducing agents such as Cp2Co or Fe powder. 1 and 2 exhibited a reversible transformation from each other with appropriate redox reagents. 1 could be utilized as a pre-catalyst to initiate the ring-opening polymerization of ε-caprolactone in the presence of alcohol but did not work. The 1/alcohol system displayed characteristics of a well-controlled polymerization with the resulting poly(ε-caprolactone) having low molecular weight distributions, a linear tendency of molecular weight evolution with conversion, and polymer growth observed for the sequential additions of ε-caprolactone monomer to the polymerization reaction. The polymerization was completely turned off by the in situ reduction of the catalytic Fe center via Cp2Co and then turned back upon the addition of [Cp2Fe]PF6. The rate of polymerization was modified by switching in situ between the Fe(III) and Fe(II) species.