Synthetic and Structural Studies of Ethyl Zinc ß-Amidoenoates and ß-Ketoiminates.

A set of heteroleptic ethyl zinc ß-amidoenoates (1, 2) and ß-ketoiminates (3) of the form [LZnEt]2 with varying steric bulk have been synthesised via the reaction of diethylzinc with ß-aminoenoate ligands HL1 and HL2 and ß-ketoimine HL3. These complexes have been characterised via 1H and 13C NMR, mass spectrometry and single-crystal X-ray diffraction, which unambiguously determined all three structures as dimeric species in the solid state. We observe the unusual dimerisation of 1 and 2 through coordination of the central zinc atom to the methine carbon of the second monomer, which gives these complexes high reactivity. The thermal properties of complex 3 are explored via thermal gravimetric analysis (TGA), to investigate their potential as single-source precursors to zinc oxide, which shows that 3 has a significantly lower decomposition temperature as compared to its bis-ligated counterpart [Zn(L3)2], which gives 3 promise as a single-source precursor to zinc oxide.

Unraveling the Steric Link to Copper Precursor Decomposition: A Multi-Faceted Study for the Printing of Flexible Electronics.

The field of printed electronics strives for lower processing temperatures to move toward flexible substrates that have vast potential: from wearable medical devices to animal tagging. Typically, ink formulations are optimized using mass screening and elimination of failures; as such, there are no comprehensive studies on the fundamental chemistry at play. Herein, findings which describe the steric link to decomposition profile: combining density functional theory, crystallography, thermal decomposition, mass spectrometry, and inkjet printing, are reported. Through the reaction of copper(II) formate with excess alkanolamines of varying steric bulk, tris-co-ordinated copper precursor ions: "[CuL3 ]," each with a formate counter-ion (1-3) are isolated and their thermal decomposition mass spectrometry profiles are collected to assess their suitability for use in inks (I1-3 ). Spin coating and inkjet printing of I1,2 provides an easily up-scalable method toward the deposition of highly conductive copper device interconnects (ρ = 4.7-5.3 × 10-7 Ω m; ≈30% bulk) onto paper and polyimide substrates and forms functioning circuits that can power light-emitting diodes. The connection among ligand bulk, coordination number, and improved decomposition profile supports fundamental understanding which will direct future design.

Ethyl Zinc ß-Ketoiminates and ß-Amidoenoates: Influence of Precursor Design on the Properties of Highly Conductive Zinc Oxide Thin Films from Aerosol-Assisted Chemical Vapour Deposition.

Highly transparent (>85 %) and conductive (1.086×10-3 â€…Ω cm) zinc oxide thin films have been deposited from specifically selected precursors allowing us to establish a direct correlation between their molecular structure and the optoelectronic properties of the deposited films. Mono-ligated ethyl zinc compounds of varying steric bulk: [EtZn(OC(Me)CH(Me)N(i Pr))]2 (1), [EtZn(OC(OEt)CH(Me)N(i Pr))]2 (2) and [EtZn(OC(OEt)CH(CH3 )N(Dipp))]2 (3) were compared with the related bis-ligated zinc complexes [Zn(OC(Me)CH(Me)N(i Pr))2 ] (4), [Zn(OC(OEt)CH(Me)N(i Pr))2 ] (5) and [Zn(OC(OEt)CH(Me)N(Dipp))2 ] (6). In all cases bulkier ligands resulted in poorer electronic properties of deposited films, whilst all mono-ligated compounds were shown as superior precursors. All complexes were characterised by 1 H and 13 C{1 H} NMR and elemental analysis, with the structure of 6 determined by single crystal X-ray diffraction. Zinc oxide films were deposited from single and dual source (with methanol) reactions of these precursors, and analysed via XRD, XPS and EDX. Optoelectronic properties were investigated through UV/vis spectroscopy and Hall effect measurements, and morphology was examined via SEM. Tauc plots from UV/vis data indicated that Film A showed the lowest band gap of 3.31 eV. Varying the elemental composition of the precursors led to changes in the elemental composition of the resultant films, as well as changes in their structural and optoelectronic properties. Using this approach of precursor design, we have been able to tune single source precursors towards zinc oxide to deposit films with specific properties.

Synthesis, solution dynamics and chemical vapour deposition of heteroleptic zinc complexes via ethyl and amide zinc thioureides.

Ethyl and amide zinc thioureides [L1ZnEt]2 (1), [L1*ZnEt]2 (2) and [L1Zn(N(SiMe3)2)]2 (3) have been synthesised from the equimolar reaction of thiourea ligands (HL1 = iPrN(H)CSNMe2 and HL1* = PhN(H)CSNMe2) with diethyl zinc and zinc bis[bis(trimethylsilyl)amide] respectively. New routes towards heteroleptic complexes have been investigated through reactions of 1, 2 and 3 with ß-ketoiminates (HL2 = [(Me)CN(H){iPr}-CHC(Me)[double bond, length as m-dash]O]), bulky aryl substituted ß-diiminates (HL3 = [(Me)CN(H){Dipp}-CHC(Me)[double bond, length as m-dash]N{Dipp}] (Dipp = diisopropylphenyl) and HL3* = [(Me)CN(H){Dep}-CHC(Me)[double bond, length as m-dash]N{Dep}] (Dep = diethylphenyl)) and donor-functionalised alcohols (HL4 = Et2N(CH2)3OH and HL4* = Me2N(CH2)3OH) and have led to the formation of the heteroleptic complexes [L1*ZnL3*] (5), [L1ZnL4]2 (6), [L1ZnL4*]2 (7), [L1*ZnL4] (8) and [L1*ZnL4*] (9). All complexes have been characterised by 1H and 13C NMR, elemental analysis, and the X-ray structures of HL1*, 1, 2, 6 and 7 have been determined via single crystal X-ray diffraction. Variable temperature 1H, COSY and NOESY NMR experiments investigating the dynamic behaviour of 5, 6 and 7 have shown these molecules to be fluxional. On the basis of solution state fluxionality and thermogravimetric analysis (TGA), alkoxyzinc thioureides 6 and 7 were investigated as single-source precursors for the deposition of the ternary material zinc oxysulfide, Zn(O,S), a buffer layer used in thin film photovoltaic devices. The aerosol-assisted chemical vapour deposition (AACVD) reaction of 7 at 400 °C led to the deposition of the heterodichalcogenide material Zn(O,S), which was confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray analysis (EDX), with optical properties investigated using UV/vis spectroscopy, and surface morphology and film thickness examined using scanning electron microscopy (SEM).

Investigations into the structure, reactivity, and AACVD of aluminium and gallium amidoenoate complexes.

Amidoenoate (AME = {ethyl-3-(R-amido)but-2-enoate}) complexes of aluminium and gallium, of the type: [AlCl2(AMER)] R = iPr (1-Al); [AlCl(AMER)2] R = iPr (2-Al), Dip (3-Al); [GaCl2(AMER)] R = iPr (1-Ga) and [GaCl(AMER)2] R = iPr (2-Ga), Dip (3-Ga), have been synthesised (iPr = isopropyl, Dip = 2,6-diisopropylphenyl). The coordination chemistry of these complexes has been studied in relation to precursor suitability. Investigations into the reactivity of the aluminium and gallium amidoenoate complexes involved reactions with hydride sources including alkali metal hydride salts, alkylsilanes, and magnesium hydride species and magnesium(I) dimers. The isolation of alkyl metal amidoenoate precursors including an aluminium hydride amidoenoate, [AlH(AMEDip)2] (4-Al) and dimethyl gallium amidoenoates [GaMe2(AMEDip)] (4-Ga), [GaMe2(AMEiPr)] (5-Ga) concluded the synthetic studies. A selection of the isolated complexes were used as precursors for aerosol assisted chemical vapour deposition (AACVD) at 500 °C. Thin films of either amorphous Al2O3 or Ga2O3 were deposited and subsequently annealed at 1000 °C to improve the materials' crystallinity. The films were characterised by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-visible (UV-vis) spectroscopy and energy dispersive X-ray analysis (EDXA).