On the Fate of Lithium Ions in Sol-Gel Derived Zinc Oxide Nanocrystals.

Among diverse chemical synthetic approaches to zinc oxide nanocrystals (ZnO NCs), ubiquitous inorganic sol-gel methodology proved crucial for advancements in ZnO-based nanoscience. Strikingly, unlike the exquisite level of control over morphology and size dispersity achieved in ZnO NC syntheses, the purity of the crystalline phase, as well as the understanding of the surface structure and the character of the inorganic-organic interface, have been limited to vague descriptors until very recently. Herein, ZnO NCs applying the standard sol-gel synthetic protocol are synthesized with zinc acetate and lithium hydroxide and tracked the integration of lithium (Li) cations into the interior and exterior of nanoparticles by combining various techniques, including advanced solid-state NMR methods. In contrast to common views, it is demonstrated that Li+ ions remain kinetically trapped in the inorganic core, enter into a shallow subsurface layer, and generate "swelling" of the surface and interface regions. Thus, this work enabled both the determination of the NCs' structural imperfections and an in-depth understanding of the unappreciated role of the Li+ ions in impacting the doping and the passivation of sol-gel-derived ZnO nanomaterials.

Towards Extended Zinc Ethylsulfinate Networks by Stepwise Insertion of Sulfur Dioxide into Zn-C Bonds.

Invited for the cover of this issue are the groups of Janusz Lewinski from Polish Academy of Sciences and Warsaw University of Technology. The image depicts how a zinc ethylsulfinate web can be woven by using diethylzinc and sulfur dioxide. Read the full text of the article at 10.1002/chem.201902733.

Towards Extended Zinc Ethylsulfinate Networks by Stepwise Insertion of Sulfur Dioxide into Zn-C Bonds.

The ability to utilize polluting gases in efficient metal-mediated transformations is one of the most pressing challenges of modern chemistry. Despite numerous studies on the insertion of SO2 into M-C bonds, the chemical reaction of SO2 with organozinc compounds remains little explored. To fill this gap, we report here the systematic study of the reaction of Et2 Zn towards SO2 as well as the influence of Lewis bases on the reaction course. Whereas the equimolar reaction provided a novel example of a structurally characterized organozinc ethylsulfinate compound of general formula [(EtSO2 )ZnEt]n , the utilization of an excess of SO2 led to the formation of the zinc(II) bis(ethylsulfinate) compound [(EtSO2 )2 Zn]n . Moreover, we have discovered that the presence of N-donor Lewis bases represents an efficient tool for the preparation of extended zinc ethylsulfinates, which in turn led to the formation of 1D [(EtSO2 ZnEt)2 (hmta)]n and 2D [((EtSO2 )2 Zn)2 (DABCO)]n ⋅solv (in which solv=THF or toluene, hmta= hexamethylenetetramine, and DABCO=1,4-diazabicyclo[2.2.2]octane) coordination polymers, respectively. The results of DFT calculations on the reactivity of SO2 towards selected Zn-C reactive species as well as the role of an N-donor Lewis base on the stabilization of the transition states complement the discussion.

From Well-Defined Alkylzinc Phosphinates to Quantum-Sized ZnO Nanocrystals.

Despite various applications of alkylzinc carboxylates in chemistry and materials science, the corresponding organozinc derivatives of organophosphorus compounds still represent an insufficiently explored area. To fill this gap, we report on the synthesis of alkylzinc phosphinates and their use as efficient precursors of phosphinate-coated ZnO nanocrystals in the quantum size regime. Examples of a series of alkylzinc phosphinates with the general formula [RZn(O2 PR'2 )] (R=tBu or Et) have been prepared through equimolar reactions between ZnR2 and a selected phosphinic acid, namely dimethylphosphinic acid (dmpha-H), methylphenylphosphinic acid (mppha-H), diphenylphosphinic acid (dppha-H), or bis(4-methoxyphenyl)phosphinic acid (dmppha-H). The reactivities of alkylzinc phosphinate complexes toward H2 O and O2 have also been investigated, which resulted in the isolation of two oxo-zinc phosphinate clusters, that is, [Zn4 (µ4 -O)(dppha)6 ] and [Zn4 (µ4 -O)(dmppha)6 ], as well as the unique alkoxy(oxo)zinc cluster [Zn4 (µ4 -O)(µ2 -OtBu)(dppha)5 ]. Analysis of the crystal structures has revealed that organozinc complexes incorporating phosphinate ligands exhibit a unique capacity for shape-driven self-assembly to produce extended networks, including noncovalent quasi-porous materials. Finally, monodispersed and quantum-sized ZnO NCs coated with phosphinate ligands have been prepared using a non-external-surfactant-assisted wet-chemical organometallic approach based on well-defined [RZn(O2 PR'2 )]-type compounds. The resulting brightly luminescent ZnO NCs exhibit average core sizes and hydrodynamic diameters in the ranges 2-4.5 nm and 5-8 nm, respectively. The size of the inorganic core is slightly affected by the character of the incorporated phosphinate ligand, being smallest for ZnO NCs coated by asymmetrically substituted mppha ligands. Regardless of whether or not various phosphinate coating ligands could be controllably applied on the ZnO NC surface, no significant differences were found in the luminescence profiles of the analyzed nanosystems.