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Magic angle spinning nuclear magnetic resonance spectroscopy experiments are widely employed in the characterization of solid media. The approach is incredibly versatile but deleteriously suffers from low sensitivity, which may be alleviated by adopting dynamic nuclear polarization methods, resulting in large signal enhancements. Paramagnetic metal ions such as Gd

A reactive ink (Ink 1) containing Ti(OPr

[Ti(OR)4] (R = Pri or But) and their heteroleptic derivatives [Ti(OR)2(L)2] [L = bidentate donor-functionalized alkoxide: mmp (1-methoxy-2-methylpropan-2-olate) dmae (2-(dimethylamino)ethanoxide), dmop (2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)propan-2-olate) or dmom ((4,4-dimethyl-4,5-dihydrooxazol-2-yl)methoxide)] are investigated as single source precursors for liquid injection MOCVD of TiO2 on F-doped SnO2 substrates. The influence of the ligands on the phase and morphology of the deposited films is investigated, and [Ti(OPri)2(dmae)2] is found to be the most effective precursor for growth of nanostructured anatase. The identity of the monodentate alkoxide is found to have the greatest influence on the phase of the thin film: OPri-containing precursors deposit anatase under all conditions whereas OBut-containing precursors have a greater tendency to deposit rutile or mixed phases. The effect of film morphology on the photoinduced hydrophilic state is demonstrated. [Ti(OR)2(dmop)2] (R = Pri or But) have been characterised by single crystal X-ray diffraction.

This article summarizes the authors' experience of developing and delivering undergraduate modules in Science Communication. The modules address two needs: resourcing science outreach activities for children in Years 5-7, and developing transferable skills (oral and written communication, team working, time management) to enhance student employability and engagement.Keywords: Employability, outreach, transferable skills

A diverse range of chiral and achiral oxazolyl ligands, which have many applications including catalysis and luminescent devices, are synthesized simply in three steps from readily available and inexpensive phenol and amino alcohol starting materials. The method can be applied to ligands with electron-donating/-withdrawing and sterically demanding/undemanding substituents, and can conveniently be scaled up to >25 g of product.

TaN x thin films were grown at temperatures ranging from 200 to 375 °C using atomic layer deposition (ALD). Pentakis(dimethylamino)tantalum (PDMAT) was used as a tantalum source with either ammonia or monomethylhydrazine (MMH) as a nitrogen co-reactant. Self-limiting behaviour was observed for both ammonia and MMH processes, with growth rates of 0.6 and 0.4 A/cycle, respectively at 300 °C. Films deposited using ammonia were found to have a mono-nitride stoichiometry with resistivities as low as 70 mΩ cm. In contrast, films deposited using MMH were found to be nitrogen rich Ta 3 N 5 with high resistivities. A Quartz Crystal Microbalance (QCM) was used to measure mass gain and loss during the cyclic ALD processes and the data was used in combination with medium energy ion scattering (MEIS) to elucidate the PDMAT absorption mechanisms.

Cerium oxide dielectric thin films have been grown on n-type silicon by atomic layer deposition using a monomeric homoleptic Ce IV alkoxide precursor with water vapour. Herein we report the dielectric properties of CeO 2 films deposited from tetrakis(1-methoxy-2-methyl-2-propanolate)cerium. The resulting films exhibit permittivities in the range 25–42 at 1 MHz with a strong dependency on the deposition temperature. The microstructural origin of this behaviour has been investigated. The as-deposited films were found to be crystalline and they exhibited the cubic fluorite structure for deposition temperatures in the range 150 °C to 350 °C. Variations in the crystallite sizes are governed by the deposition temperature and have been estimated using a Debye–Scherrer analysis of the X-ray diffraction patterns. The changing crystallite size correlates with changes seen in the triply-degenerate F 2g first-order Raman line half-width at 465 cm − 1 . It is concluded that the frequency dependency of the film dielectric properties is strongly influenced by the crystallite size which in turn is governed by the growth temperature.

Ytterbium triflate, Yb(OTf) 3 , catalyzes the intermolecular reductive homocouplings of imines, aldehydes, and ketones at loadings of 5 mol % in the presence of Mg and Me 3 SiCl to give isolated yields of up to 95%. Diastereoselectivity of up to 4/96 ( dl / meso ) is achieved for aromatic aldehydes, up to 100% dl for aliphatic aldehydes, and 100% dl for an intramolecular imine coupling.

Thin films of lanthanum zirconium oxide, LaxZr1–xO2–δ (x = 0.09 – 0.77) are deposited by liquid injection metal-organic (MO)CVD and atomic layer deposition (ALD) using toluene solutions of the precursors [(iPrCp)3La] and [(MeCp)2ZrMe(OMe)]. Auger electron spectroscopy (AES) shows that LaxZr1–xO2–δ films grown by ALD at 300 °C contain carbon at levels of 3.2 – 5.4 at.- %, whilst films grown by MOCVD at 400 °C contain carbon levels of 2.4 – 10.5 at.- %. Analysis by X-ray diffraction (XRD) shows that films with lower La contents (x) of 0.09 and 0.22 crystallize into cubic lanthanum-stabilized zirconia phase on annealing at 700 °C, whereas films of higher La content (x = 0.35, 0.63) remain amorphous. In general, the onset of crystallization of these films increases with the lanthanum fraction. For x = 0.35, crystallization to the cubic phase of ZrO2 is observed between 800 and 900 °C. LaxZr1–xO2–δ films grown by ALD show good dielectric properties with low hysteresis voltages, negligible flatband voltage shifts, and k values ranging from 11 to 14. LaxZr1–xO2–δ films grown by ALD have leakage current densities of 2.6 × 10–6 – 5.3 × 10–7 A cm–2, while films grown by MOCVD have leakage current densities of between 1.1 × 10–6 A cm–2 and 8.3 × 10–7 A cm–2.

Metalorganic chemical vapour deposition (MOCVD) is an attractive technique for the deposition of dielectric and ferroelectric oxide thin films such as ZrO 2 , HfO 2 , Hf-aluminate and -silicate, lanthanide oxides, Pb(Zr,Ti)O 3 and SrBi 2 Ta 2 O 9 , which have a variety of applications in microelectronic devices. In this paper the molecular design of a range of new oxide precursors is described. It is shown how the careful selection and design of precursor ligands, such as alkoxides and β-diketonates, leads to precursors with improved physical properties and significantly enhanced MOCVD performance.

Thin films of praseodymium aluminate (PrAlOx) and neodymium aluminate (NdAlOx) have been deposited by liquid injection metalorganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD) using the bimetallic alkoxide precursors [PrAl(OPri)6(PriOH)]2 and [NdAl(OPri)6(PriOH)]2. Auger electron spectroscopy showed that all the films were high purity, with no carbon detectable (est. detection limit ≈ 0.5 at %). X-ray diffraction showed that the PrAlOx and NdAlOx films remained amorphous up to temperatures of 900 °C. Films grown by ALD were all Pr- or Nd-deficient (Pr/Al = 0.54−0.71; Nd/Al = 0.30−0.42), but near-stoichiometric films of PrAlOx (Pr/Al = 0.76) and NdAlOx (Nd/Al = 0.87) were obtained by MOCVD at deposition temperatures of 500 and 450 °C, respectively. The electrical properties of the films were assessed using C−V and I−V on MOS capacitors. Post-metalization annealing (PMA) in forming gas was effective in reducing charge levels in all films. Following PMA, the dielectric properties of N...

Atomic layer deposition (ALD) of lanthanum oxide on glass and silicon substrates was examined using lanthanum silylamide, La[N(SiMe 3 ) 2 ] 3 , and water as precursors in the substrate temperature range of 150-250 °C. The effect of pulse times and precursor evaporation temperature on the growth rate and refractive index was investigated. The films remained amorphous regardless of the deposition conditions. The resulting La 2 O 3 films contained noticeable amounts of hydrogen and silicon and were chemically unstable while stored in ambient air. Lanthanum aluminum oxide films were achieved with stoichiometry close to that of LaAlO 3 at 225°C from La[N(SiMe 3 ) 2 ] 3 , Al(CH 3 ) 3 , and H 2 O. The lanthanum β-diketonate precursor, La(thd) 3 , was used as the reference precursor.

Thin films of HiO 2 have been deposited by liquid injection metal-organic (MO)CVD using the new alkoxide precursor [Hf(dmop) 4 ] (dmop = 2-(4,4-dimethyloxazolinyl)-propanolate). The crystal structure of [Hf(dmop) 4 ] has been determined, and shows it to be a six-coordinate monomeric complex. [Hf(dmop) 4 ] is volatile and is significantly less reactive to air and moisture than simple Hf alkoxide complexes such as [Hf(O'Bu) 2 ]. The HfO 2 thin films were deposited over substrate temperatures ranging from 350 °C to 650 °C. Analysis by X-ray diffraction (XRD) shows that the films are amorphous at deposition temperatures of 400 °C and below. At substrate temperatures above 450 °C. the films adopt a monoclinic (α-HfO 2 ) phase with a fiber texture dependent upon growth temperature. Analysis by Auger electron spectroscopy (AES) shows that the films are non-stoichiometric and contain residual carbon (2.1 - 11.6 at.-%) and nitrogen (0.4 - 1.9 at.-%).

Complexes of lanthanide chlorides with pybox ligands catalyze the enantioselective silylcyanation of aromatic and aliphatic aldehydes with ee's of up to 91% under mild and convenient conditions. Studies of catalysts prepared with pybox ligands of varying enantiomeric purity show no marked nonlinear effects, indicating a monometallic transition state. A mechanism for the catalytic reaction is proposed. Crystal structures of [LnCl2(S-Pri-pybox)2][LnCl4(S-Pri-pybox)] (Ln = Eu, Yb) are reported. The structure of the related triflate complex [La(OTf)3(S-Pri-pybox)2] is also reported. Diastereoselectivity has been observed in the reactions of Ln(OTf)3 with racemic Pri-pybox: for Ln = Eu, a heterochiral product containing one R- and one S-pybox ligand is observed, whereas for Ln = Yb a racemic mixture of homochiral bis(pybox) complexes is formed.

A complex of samarium diiodide (SmI(2)) with tetraglyme catalyzes the intermolecular pinacol coupling of aromatic or aliphatic aldehydes at loadings of 10 mol % in the presence of Me(2)SiCl(2) and Mg. Diastereoselectivity of up to 95/5 (+/-/meso) has been achieved for aliphatic aldehydes and up to 19/81 (+/-/meso) for aromatic aldehydes. De values of up to 99% have been achieved in intramolecular pinacol coupling reactions using the SmI(2)/tetraglyme/Mg/Me(2)SiCl(2) catalytic system.

Lanthanide, or rare-earth oxides are currently being investigated as alternatives to SiO 2 as the dielectric insulating layer in sub-0.1 μm CMOS technology. Metalorganic chemical vapour deposition (MOCVD) and atomic layer deposition (ALD) are promising techniques for the deposition of these high- κ dielectric oxides and in this paper some of our recent research into the MOCVD and ALD of PrO x , La 2 O 3 , Gd 2 O 3 , Nd 2 O 3 and their related silicates are reviewed.

Thin films of hafnium oxide (HfO 2 ), gadolinium oxide (Gd 2 O 3 ), and praseodymium oxide (PrO x ) have been deposited by liquid injection atomic layer deposition (ALD) and for comparison, have also been deposited by thermal metal-organic (MO) CVD using the same reactor. The ALD-grown films were deposited on Si(100) over a range of substrate temperatures (150-450 °C) using alternate pulses of [Hf(mmp) 4 ], [Gd(rump) 3 ], or [Pr(mnip) 3 ] (mmp = OCMe 2 CH 2 OMe) and water vapor. X-ray> diffraction (XRD) analysis showed that as-grown films of HiO 2 were amorphous hut these crystallized into the monoclinic phase after annealing in air at 800 °C. XRD analysis showed that as-grown Gd 2 O 3 and PrO x films had some degree of crystallinity. Residual carbon (0.8-3.3 at.-%) was detected in the HfO 2 and PrO, films by Auger electron spectroscopy (AF-S). but not in the Gd 2 O 3 films. The self-limiting behavior of the precursors was investigated at 225 °C by varying the volume of precursor injected during each ALD cycle and, in each case, oxide growth was not fully self-limiting. We propose a mechanism for this involving β-hydride elimination of the mmp group, and also propose some general mechanistic principles which may influence the growth of oxides by ALD using other precursors.

Thin films of neodymium oxide (Nd2O3) have been deposited on Si(100) and GaAs(100) substrates by liquid injection MOCVD using the new neodymium alkoxide, [Nd(mmp)3] (mmp = 1-methoxy-2-methyl-2-propanolate, OCMe2CH2OMe). The films were grown over a wide range of substrate temperatures (250–550 °C) and were found to be of high purity, with no detectable carbon. The films exhibited the cubic C-type Nd2O3 phase or were amorphous depending on substrate temperature.

Amorphous PrOx based films were grown by atomic layer deposition in the temperature range 200−400 °C from Pr[N(SiMe3)2]3 and H2O on n-Si(100) and borosilicate glass substrates. The films contained considerable amounts of residual hydrogen and residual or diffused silicon. The refractive indexes of the films varied between 1.76 and 1.87. Crystallization took place after annealing at 900−1000 °C, and X-ray diffraction data indicated that the films were Pr9.33(SiO4)6O2. The effective permittivity of 70−100 nm thick films was in the range of 14−16. Annealing at 800 °C in nitrogen increased the effective permittivity to 15.6−21.0 and decreased the rechargeable trap density. Praseodymium silicate films may be applied after annealing as dielectric layers in capacitive structures.

A range of high-permittivity (κ) dielectric oxides are currently being investigated as alternatives to SiO2 as the dielectric insulating layer in sub-0.1 μm CMOS technology. Metalorganic chemical vapour deposition (MOCVD) and atomic layer deposition (ALD) are promising techniques for the deposition of these high-κ dielectric oxides. Some recent developments in precursors for the MOCVD and ALD of ZrO2, HfO2, Zr- and Hf-silicate and the rare earth oxides M2O3 (M = Pr, La, Gd, Nd) are discussed.

A novel series of modular chiral polyether podands derived from enantiomerically pure hydrobenzoin and binaphthol has been prepared using a NaH/15-crown-5 mediated Williamson ether synthesis. These new homochiral ligands form catalytically active complexes with lanthanide triflates, two of which have been characterised by X-ray diffraction.

This paper reviews our work with enantioselective lanthanide reagents and catalysts for organic synthesis. Heterometallic reagents M3[Ln(binol)3] (M=Li; Ln=lanthanide; H2binol=binaphthol) mediate the addition of RLi to aldehydes with ee's of up to 84%. Structural studies have been carried out where M=Li or Na, Ln=Eu, Y or Yb and with enantiomerically pure or racemic binol. There are important differences in coordination chemistry dependent on the ionic radius of M and Ln. [LnCl3(pybox)2] are effective catalysts for the silylcyanation of aldehydes, giving ee's of up to 89% under convenient reaction conditions. Structural studies have been undertaken on [Ln(OTf)3(Pri pybox)2] for Ln=La, Eu or Yb.

Anhydrous alkali metal lanthanide binaphtholates M3[Ln(binol)3] (M = Li, Na; Ln = lanthanide or yttrium; H2binol = binaphthol) are prepared by reaction of [Ln{N(SiMe3)2}3] with 3 equiv of MHbinol. Reaction of [Ln{N(SiMe3)2}3] (Ln = Y or Yb) with 3 equiv of rac-LiHbinol gives a racemic mixture of RRS- and SSR-Li3[Ln(binol)3] 2 as the only product. In contrast, reaction of [Ln{N(SiMe3)2}3] with 3 equiv of rac-NaHbinol gives a racemic mixture of RRR- and SSS-Na3[Ln(binol)3] when Ln = Y. When Ln = Yb, a 3:1 mixture of RRR-/SSS- and RRS-/SSR-Na3[Ln(binol)3] is formed. Complexes have been characterized in solution by NMR spectroscopy. The 3-proton of the unique binol ligand in RRS- and SSR-Li3[Y(binol)3] is shifted upfield by interaction with the π-system of a neighboring naphthyl ring. Analysis of paramagnetically induced 1H NMR shifts of Yb complexes shows them to be entirely dipolar in origin. X-ray crystal structures have been determined for the following compounds: rac-[Li(THF)2]3[Y(binol)3]·THF, 2a; rac-...

C2 symmetric chelating ligands can be used to prepare homochiral lanthanide complexes which act as enantioselective reagents and catalysts for synthetically important reactions. [LnCl3(pybox)2] (pybox is 2,6-bis(substituted-2-oxazolin-2-yl)pyridine) catalyse the enantioselective silylcyanation of aldehydes. [Li3Ln(binol)3] (H2binol is binaphthol) are reagents for the enantioselective addition of MeLi to aldehydes. [La(OTf)3(Pri-pybox)2] and [Li(THF)2]2[Li(Et2O)][Yb(R-binol)3] have been characterised by single crystal X-ray diffraction.

Lanthanide tris(silylamides) LnL3 reacted with 2/3 equivalents of the trisilanol (C6H11)7Si7O9(OH)31 in THF to give the lanthanide silasesquioxanes [(C6H11)7Si7O12Ln(THF)2] which are dimeric in solution at 233 K. Reaction of LnL3 with 1 equivalent of 1 in THF resulted in complete conversion of 1 into the trisilylated compound (C6H11)7Si7O9(OSiMe3)3 as does reaction of LnL3 with 2/3 equivalents of 1 in toluene. Reaction of [(C6H11)7Si7O12Ln(THF)2] with 1 equivalent of (Me2NCH2CH2)2NMe (PMDTA) gave the monomeric complex [(C6H11)7Si7O12Ln(PMDTA)]. The chloro-functionalised lanthanide silasesquioxane [(C6H11)7Si7O11(OSiMe3)LnCl(THF)] was formed by reaction of [(C6H11)7SiO7O12Ln(THF)2]with 1 equivalent of Me3SiCl. New compounds have been characterised by NMR spectroscopy and by elemental analysis.

Complexes formed between lanthanide trichlorides and 2,6-bis( substituted -2-oxazolin-2-yl)pyridine (pybox) ligands are effective catalysts for the enantioselective addition of trimethylsilylcyanide (TMSCN) to a range of aldehydes.

Addition of one equivalent of benzoic acid greatly enhances the efficiency of our ytterbium triflate catalyzed allylation of aldehydes with allyltributyltin in acetonitrile. Crucial modifications to reaction conditions result in a dramatically increased rate at remarkably low catalyst loading.

New complexes of lanthanide(III) triflates with polyethylene glycol (HO(CH 2 CH 2 O) n H; n =2, 3, 4) and polyethyleneglycol dimethylether (CH 3 O(CH 2 CH 2 O) n CH 3 ; n =2, 3, 4) ligands have been prepared and characterised by X-ray diffraction. These complexes are effective Lewis acid catalysts for the allylation of aldehydes with allyltributyltin, and for the Diels–Alder reaction. Complexes with new homochiral podand ligands have been synthesised and in one case characterised by X-ray diffraction, and their catalytic activity is under investigation.

Complexes of lanthanide triflates Ln(OTf)3 with polyether (MeO(CH2CH2O)nMe) and poly(ethylene glycol) (HO(CH2CH2O)nH) ligands (n = 2−4) have been prepared and characterized, and the activity of these complexes as Lewis acid catalysts has been investigated. The complexes [Ln(OTf)3(HO(CH2CH2O)nH)] have been shown to catalyze the allylation of a range of aldehydes with allyltributylstannane, and the complexes [Ln(OTf)3(MeO(CH2CH2O)nMe)] catalyze the Diels−Alder addition of N-crotonyloxazolidinone to cyclopentadiene. The single-crystal X-ray structures of [Dy(OTf)2(H2O)2(MeO(CH2CH2O)4Me)][OTf] and [La(OTf)3(THF)(HO(CH2CH2O)4H)] are reported.

15-crown-5 greatly facilitates Williamson ether synthesis when sodium hydride base is used in THF solvent. This mild yet versatile procedure has been employed in the synthesis of new homochiral polyether ligands and bis-allylic ethers which are inaccessible by conventional methods.

A series of homoleptic tris-chelate complexes ML3 (M = Al or rare earth; L = chiral or achiral oxazolyl phenolate or -naphtholate) is reported. In all cases, complexes crystallize as mer-isomers and complete diastereoselectivity is observed on crystallization of the complexes: ML3 crystallize with Λ-helicity at the metal where L = (S)-oxazolylphenolate. Complexes have been characterized in solution by NMR spectroscopy, demonstrating rapid ligand exchange at ambient temperature for rare earth complexes, and slow exchange on the NMR timescale for complexes of Al; in all cases the mer-isomer is observed exclusively. Crystal structures are reported for [YL3]2 (L = (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)-phenolate), mer-[YbL3] (L = (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)-6-methylphenolate) and mer-[AlL3] (L = (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)-6-methylphenolate, L = (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)-6-cyanophenolate), L = (S)-1-(4-isopropyl-4,5-dihydrooxazol-2-yl)naphthalen-2-olate, L = 1-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)naphthalen-2-olate).

In the presence of excess LiNiPr2, lanthanide tris(di-isopropylamides) Ln(NiPr2)3 form bimetallic complexes [Li(THF)Ln(NiPr2)4], which are common impurities in the synthesis of [Ln(NiPr2)3(THF)]. NMR studies show that at room temperature [Li(THF)Ln(NiPr2)4] consists of a tetrahedral array of four equivalent NiPr2 ligands on Ln, with the Li(THF) moiety migrating rapidly between them. At 223 K, a bimetallic structure [(THF)Li(μ-NiPr2)2Ln(NiPr2)2] is frozen out. [Ln(NiPr2)3(THF)] may be synthesized free of [Li(THF)Ln(NiPr2)4] impurity by reaction of LnCl3 with 2.5 equivalents of LiNiPr2.

Lanthanum triflate in combination with benzoic acid catalyses the allylation of aldehydes at low catalyst loading, without the need to activate the catalyst in advance.

Lanthanum triflate–benzoic acid catalyses the in situ formation and allylation of various imines from aldehydes and an aromatic amine.

Various 2-aryloxazoline ligands, especially o-hydroxyaryl-substituted ones, are prepared via conversion of arylaldehydes to the corresponding nitriles following by ZnCl2-catalyzed reaction with 2-amino alcohols.

Thin films of ceria (CeO(2)) have many applications, and their synthesis by liquid-injection MOCVD (metal-organic chemical vapor deposition) or ALD (atomic layer deposition) requires volatile precursor compounds. Here we report the synthesis of a series of homoleptic and heteroleptic Ce(IV) complexes with donor-functionalized alkoxide ligands mmp (1-methoxy-2-methylpropan-2-olate), dmap (1-(dimethylamino)propan-2-olate), and dmop (2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)propan-2-olate) and their potential as precursors for MOCVD and ALD of CeO(2). New complexes were synthesized by alcohol exchange reactions with [Ce(OBu(t))(4)]. [Ce(mmp)(4)] and [Ce(dmap)(4)] were both found to be excellent precursors for liquid-injection MOCVD of CeO(2), depositing high purity thin films with very low carbon contamination, and both have a large temperature window for diffusion controlled growth (350-600 °C for [Ce(mmp)(4)]; 300-600 °C for [Ce(dmap)(4)]). [Ce(mmp)(4)] is also an excellent precursor for liquid-injection ALD of CeO(2) using H(2)O as oxygen source and demonstrates self-limiting growth from 150 to 350 °C. [Ce(dmap)(4)] has lower thermal stability than [Ce(mmp)(4)] and does not show self-limiting growth in ALD. Heteroleptic complexes show a tendency to undergo ligand redistribution reactions to form mixtures in solution and are unsuitable as precursors for liquid-injection CVD.

Ytterbium triflate has been found to be an excellent Lewis acid catalyst for the reaction of aldehydes with allyltributylstannane.

15-crown-5 greatly facilitates Williamson ether synthesis when sodium hydride base is used in THF solvent. This mild yet versatile procedure has been employed in the synthesis of new homochiral polyether ligands and bis-allylic ethers which are inaccessible by conventional methods.