From Well‐Defined Alkylzinc Phosphinates to Quantum‐Sized ZnO Nanocrystals

Abstract

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(O PR' )] (R=tBu or Et) have been prepared through equimolar reactions between ZnR 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 H O and O have also been investigated, which resulted in the isolation of two oxo-zinc phosphinate clusters, that is, [Zn (μ -O)(dppha) ] and [Zn (μ -O)(dmppha) ], as well as the unique alkoxy(oxo)zinc cluster [Zn (μ -O)(μ -OtBu)(dppha) ]. 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(O PR' )]-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.

Hydrolysis of organometallic and metal–amide precursors: synthesis routes to oxo-bridged heterometallic complexes, metal-oxo clusters and metal oxide nanoparticles

“…96, 173, 174, 176-179, 208, 209 Lewiński and co-workers employed a simple 'one-pot, two-step' strategy of exposing a THF solution of ligated precursor [ZnEtL]n (L = [RCO2] − , [R2PO2] − or aminoalcoholate) to air, producing small (~2-8 nm) ZnO@L NPs with a dense surface coverage of ligand. 176,178,179 This synthetic route yields ZnO NPs described as (ZnO)x(ZnL2)y(L)z (L = monoanionic ligand) with more than a single monolayer of ligands. This ligand shell is described as 'impermeable', and protects the ZnO core, which results in slow photoluminescence (electron-hole separation up to 2.2 μs) 180 , giving these NPs enhanced properties relative to ZnO from sol-gel techniques.…”

“…Different ligand precursors lead to NPs with a variety of properties and applications. [176][177][178][179][180][181][182][183] TEM micrograph reproduced with permission from the RSC. 177 the amount of ligand is helpful in forming composite materials, where excess ligand would affect the material properties, e.g.…”

Cu/M:ZnO (M = Mg, Al, Cu) colloidal nanocatalysts for the solution hydrogenation of carbon dioxide to methanol

“…ZnPh2, ZnCy2, ZnEt2), in the presence of an aqueous stable, anionic coordinating ligand (e.g. carboxylate or phosphinate), readily generates soluble ZnO nanoparticles, 48,[50][51][52][53][54][55][56][57] with a high density of surface defects, proposed to be beneficial for catalysis. 9,44,58 Hydrolytic syntheses provide straightforward control of ligand coverage and kinetic control over the growth of particles, allowing access to small ZnO nanoparticles (2-4 nm).…”

“…9,44,58 Hydrolytic syntheses provide straightforward control of ligand coverage and kinetic control over the growth of particles, allowing access to small ZnO nanoparticles (2-4 nm). 4,50,54,57 The methodology is potentially attractive for dopant incorporation since a second organometallic reagent can simply be added to the one-pot hydrolysis reaction. The synthesis of doped-ZnO nanoparticles via co-precipitation methods has allowed doping levels >10% (e.g.…”

Disclosing Interfaces of ZnO Nanocrystals Using Dynamic Nuclear Polarization: Sol‐Gel versus Organometallic Approach

“…[5d, 7] More recently,wehave elaborated the one-pot self-supporting organometallic (OSSOM) procedure based on the controlled exposition of a[ EtZn(X)]-type precursor (X = monoanionic organic ligand) to air leading to ZnO NCs coated with an organic shell composed of surface-anchored X-type ligands. [8] TheO SSOM process is thermodynamically controlled and affords stable,b io-safe [8e] and well-passivated ZnO NCs with ultra-long-lived luminescence. [8e,9] To gain ab etter understanding of how the interface between the inorganic core and the organic shell relates to observed synthetic procedure-driven properties,Z nO NCs coated with monoanionic diphenyl phosphate (DPP) ligands were prepared by both, the OSSOM and sol-gel methods as representative nanosystems (abbreviated as OM NCs and SG NCs,respectively;for experimental details see the Supporting Information).…”