From a Well-Defined Organozinc Precursor to Diverse Luminescent Coordination Polymers Based on Zn(II)-Quinolinate Building Units Interconnected by Mixed Ligand Systems.

Introduction of photoactive building blocks into mixed-ligand coordination polymers appears to be a promising way to produce new advanced luminescent materials. However, rational design and self-assembly of the multi-component supramolecular systems is challenging from both a conceptual and synthetic perspective. Here, we report exploratory studies that investigate the potential of [Zn(q)2]2[tBuZn(OH)]2 complex (q = deprotonated 8-hydroxyquinoline) as an organozinc precursor as well as a mixed-ligand synthetic strategy for the preparation of new luminescent coordination polymers (CPs). As a result we present three new 2D mixed-ligand Zn(II)-quinolinate coordination polymers which are based on various zinc quinolinate secondary building units interconnected by two different organic linker types, i.e., deprotonated 4,4'-oxybisbenzoic acid (H2obc) as a flexible dicarboxylate linker and/or selected bipyridines (bipy). Remarkably, using the title organozinc precursors in a combination with H2obc and 4,4'-bipyridine, a novel molecular zinc quinolinate building unit, [Zn4(q)6(bipy)2(obc)2], was obtained which self-assembled into a chain-type hydrogen-bonded network. The application of the organometallic precursor allowed for its direct reaction with the selected ligands at ambient temperature, avoiding the use of both solvothermal conditions and additional base reagents. In turn, the reaction involving Zn(NO3)2, as a classical inorganic precursor, in a combination with H2obc and bipy led to a novel 1D coordination polymer [Zn2(q)2(NO3)2(bipy)]. While the presence of H2obc was essential for the formation of this coordination polymer, this ditopic linker was not incorporated into the isolated product, which indicates its templating behavior. The reported compounds were characterized by single-crystal and powder X-ray diffraction, elemental analysis as well as UV-Vis and photoluminescence spectroscopy

A modular design approach to polymer-coated ZnO nanocrystals

Summary: Hybrid materials based on inorganic nanocrystals with organic polymers feature peculiar and fascinating properties and various applications. However, there is still a need for simple synthesis procedures that provide precise control over the polymer/nanocrystal microstructure of these materials. Herein, a novel organometallic approach to polymer-coated ZnO nanocrystals was developed. The presented method merges the initial ring-opening polymerization of ϵ-caprolactone mediated by an organozinc alkoxide initiator and an air-promoted transformation of the resulting macromolecular organozinc species. This one-pot procedure results in quantum-sized ZnO crystals with a core diameter of ca 3 nm coated by poly(ϵ-caprolactone) covalently bonded to the surface. Overall, the ability to create well-defined hybrid composites should provide a unique ability to access various nanosystems

Toward Factors Affecting the Degree of Zinc Alkyls Oxygenation: A Case of Organozinc Guanidinate Complexes

While extensive research has been carried out on the oxygenation of alkylzinc complexes for decades, this issue still remains unresolved and significant uncertainties concerning the mechanism of these reactions and the composition of the resulting products persist. These reactions are believed to proceed via the initial formation of ROOZn­(L) species, but studies on the oxygenation reactions have been substantially impeded by the low stability of the alkylperoxides. This report describes the oxygenation of a <i>tert</i>-butylzinc guanidinate, i.e. a <i>t</i>BuZn­(L)-type complex (L = deprotonated 1,4,6-triazabicyclo[3.3.0]­oct-4-ene), and the isolation and characterization of an unprecedented aggregate based on a combination of a ROOZn­(L) moiety and two parent <i>t</i>BuZn­(L) molecules, {[<i>t</i>BuZn­(L)]₂[<i>t</i>BuOOZn­(L)]}. Further study revealed that examined <i>tert</i>-butylzinc guanidinate molecules exhibit an ability to entrap other oxygenated species, which was demonstrated by an aggregate containing a <i>tert</i>-butylzinc <i>tert</i>-butylperoxide and two <i>t</i>BuZn­(L) molecules, {[<i>t</i>BuZn­(L)]₂[<i>t</i>BuOZn<i>t</i>Bu]}. Thus, the reported studies indicate that entrapment of the product of an oxygenation reaction by the parrent alkylzinc species is another important factor controlling the oxygenation of organometallics

A New Look at the Reactivity of TEMPO toward Diethylzinc

Reactions of diethylzinc with TEMPO were investigated. Dropwise addition of 1 equiv of TEMPO to Et₂Zn at −10 °C leads to the nitroxide complex EtZn­(TEMPO) in high yield, whereas upon addition of 2 equiv of TEMPO the corresponding homoleptic nitroxide compound Zn­(TEMPO)₂ is formed. Diffusion ordered NMR spectroscopy experiments revealed that both zinc nitroxide compounds exist in monomeric forms in solution, while single-crystal X-ray diffraction confirmed their dimeric structure in the solid state

Synthesis and Structure of Alkylzinc 3,5-Diphenylpyrazolates: Dramatic Influence of Steric and Solvent Effects

The reaction of R₂Zn (R = Et, ^<i>t</i>Bu) with 3,5-diphenylpyrazole results in the formation of three structurally diverse alkylzinc pyrazolates: a novel dinuclear tetrahydrofuran solvate, an unprecedented trimeric structure, and a spiro trinuclear aggregate. Structural analysis of the resulting complexes provides a new look at the aggregation and stabilization of alkylzinc species