Chromium containing zinc oxide materials from organobimetallic precursors

Abstract

Zinc oxide has become one of the most important semiconductor materials and it possesses a multitude of properties and applications. An even wider spectrum of properties can be envisioned if an additional element is introduced. On the cation side there is large interest in the combination of ZnO with paramagnetic metal centres like Cr(III). Two new single source precursors containing "ZnO" and chromium in the ratios 1 : 1 and 1 : 2 are presented. Advantages and disadvantages of using these precursors are reported. One of the advantages is that the geometric organization of the magnetic centres in the ZnO matrix can be preorganized on the molecular scale.

The use of mixed-metal single source precursors for the synthesis of complex metal oxides

“…30,[55][56][57][58] Many examples state the ability of SSPs to decompose and crystallise into CMOs at much lower temperatures than in traditional solid-state ceramic methods. 11,12,18,23,34,41,42,54,56,59 Decomposition of metal-organic species requires the release of gaseous organic decomposition products (and possibly solvent molecules), and the release of these gases may influence the particle size and porosity of the produced oxide. Higher organic content in precursors allows for greater porosity and smaller particle sizes in their decomposition products, attributed to greater gas escape during thermolysis.…”

“…46,87 Similarly, utilising the affinity of benzene rings to coordinate to the Cr(CO)3 fragment allows the formation of Zn-Cr precursors [MeZnOCH2PhCr(CO)3]4 and [MeZnOCH(PhCr(CO)3)2]2, useful for ZnCr2O4 synthesis. 18 The ferrocene unit is also a convenient group for including Fe into a molecule, examples include Fe-Sn precursors (C5H5)Fe(C5H4)C6H4CO2SnR3. 70 Inclusion of extra metals within counterions is another versatile approach, which creates a perfect distribution of the metals when crystallised in an ionic lattice and can allow a variety of secondary/tertiary metals to be incorporated into isostructural compounds.…”

“…This may be the case if different types of coordination mode are found within an SSP, For example, the Zn-Cr precursor [MeZnOCH2PhCr(CO)3]4 has been shown to thermally decompose initially to ZnO before forming a mixture of ZnO and ZnCr2O4. 18 This process is attributed to an initial loss of the Me and CO ligands at low temperatures (105-300 ᵒC) releasing Zn to form ZnO, followed by decomposition of the aryl groups which coordinate Cr at higher temperature (330 ᵒC), which then allows formation of the ZnCr2O4 spinel (Fig. 12) (still at much lower temperature than conventional ceramic methods, which may require 900 ᵒC).…”

“…We define this broad group of materials as complex metal oxides (CMOs) which include mixed-metal oxides (AxByOz), heterometal doped metal oxides (B:AxOy) or composite metal oxides with a mixture of oxide phases (AwOx/ByOz). Today, many types of mixed-metal oxides are accessible from SSPs including perovskites (ABO3), [10][11][12][13][14][15][16] pyrochlores (A2B2O7), 17 spinels (AB2O4), [18][19][20][21][22][23][24][25] metal vanadates [Mx(VO4)y], 26,27 feldspars (MAl2Si2O8) 28 and Aurivilius phases (Bi2O2)(An−1BnO3n+1). 29…”

From Ethanolamine Precursor Towards ZnO—How N Is Released from the Experimental and Theoretical Points of View

“…This would allow the filling of the vacant coordination position generated after the cleavage of the Zn–N1 bond, leading to compounds with higher nuclearity and bridging –OR ligands or acetato groups connecting two or three Zn(II) ions. Zn(II) complexes with μ 2 – and µ 3 –OR units are common [46,47,48,49,50,51,52,53,54,55,56,57,58,59]. They are present in a large amount of low-nuclearity compounds (i.e., dimers [46,48,49] or oligomers [46,50,51,52,53]), in the typical cubane-like “Zn 4 O 4 ” clusters [46,49,54,55,56,57] and also in more sophisticated Zn(II) complexes [46,58,59] such as tetrakis {(µ 3 –methoxo)(pentacarbonyl-manganese)}zinc(II) [46,59].…”