Catalyzing Singlet Fission by Transition Metals: Second versus Third Row Effects.

The synthesis and characterization of platinum(II) and palladium(II) complexes bearing two (dimers Pt(L)Cl and Pd(L)Cl), one (monomers Pt(L)(L)Cl and Pd(L)(L)Cl), or no (reference compounds Pt(L)Cl and Pd(L)Cl) pentacene-based pyridyl ligands are presented. Photophysical properties of the dimers are probed by means of steady-state and time-resolved transient absorption measurements in comparison to the monomer and model compounds. Our results document that despite enhanced spin-orbit coupling from the presence of heavy atoms, intramolecular singlet fission (iSF) is not challenged by intersystem crossing.

CVD Grown Tungsten Oxide for Low Temperature Hydrogen Sensing: Tuning Surface Characteristics via Materials Processing for Sensing Applications.

The intrinsic properties of semiconducting oxides having nanostructured morphology are highly appealing for gas sensing. In this study, the fabrication of nanostructured WO thin films with promising surface characteristics for hydrogen (H ) gas sensing applications is accomplished. This is enabled by developing a chemical vapor deposition (CVD) process employing a new and volatile tungsten precursor bis(diisopropylamido)-bis(tert-butylimido)-tungsten(VI), [W(N Bu) (N Pr ) ].

Low-temperature ALD/MLD growth of alucone and zincone thin films from non-pyrophoric precursors.

The combined atomic/molecular layer deposition (ALD/MLD) technique is emerging as a state-of-the-art synthesis route for new metal-organic thin-film materials with a multitude of properties by combining those of the inorganic and the organic material. A major part of the studies so far reported have focused on aluminum or zinc alkyls, so-called alucone and zincone films, typically grown from trimethyl aluminum (TMA) or diethyl zinc (DEZ) as the metal-bearing precursor, and a simple aliphatic bi-functional alcohol molecule such as ethylene glycol (EG) as the organic precursor. However, these common precursors possess certain disadvantages: both TMA and DEZ are pyrophoric, DEZ being additionally thermally unstable, while EG has a strong tendency for various unideal reaction modes.

Molecular Permeation in Freestanding Bilayer Silica.

Graphene and other single-layer structures are pursued as high-flux separation membranes, although imparting porosity endangers their crystalline integrity. In contrast, bilayer silica composed of corner-sharing (SiO) units is foreseen to be permeable for small molecules due to its intrinsic lattice openings. This study sheds light on the mass transport properties of freestanding 2D SiO upon using atomic layer deposition (ALD) to grow large-area films on Au/mica substrates followed by transfer onto SiN windows.

Influence of different ester side groups in polymers on the vapor phase infiltration with trimethyl aluminum.

The vapor phase infiltration (VPI) process of trimethyl aluminum (TMA) into poly(4-acetoxystyrene) (POAcSt), poly(nonyl methacrylate) (PNMA) and poly(-butyl methacrylate) (PtBMA) is reported. Depth-profiling X-ray photoelectron spectroscopy (XPS) measurements are used for the first time for VPI based hybrid materials to determine the aluminum content over the polymer film thickness. An understanding of the reaction mechanism on the interaction of TMA infiltrating into the different polymers was obtained through infrared (IR) spectroscopy supported by density functional theory (DFT) studies.

Dynamic Kinetic Sensitization of β-Dicarbonyl Compounds-Access to Medium-Sized Rings by De Mayo-Type Ring Expansion.

Herein, we present a photocatalyzed two-carbon ring expansion of β-dicarbonyl compounds with unactivated olefins that provides facile access to medium-sized rings. Selective sensitization of the substoichiometric enol tautomer enables reactivity of substrates incompatible with the classical De Mayo reaction conditions. Key to success is the identification of the metal-based sensitizer fac-[Ir(CF -pmb) ], which can be excited using common near-visible LEDs, and possesses a high triplet excited state energy of 73.

Rational Development of Guanidinate and Amidinate Based Cerium and Ytterbium Complexes as Atomic Layer Deposition Precursors: Synthesis, Modeling, and Application.

Owing to the limited availability of suitable precursors for vapor phase deposition of rare-earth containing thin-film materials, new or improved precursors are sought after. In this study, we explored new precursors for atomic layer deposition (ALD) of cerium (Ce) and ytterbium (Yb) containing thin films. A series of homoleptic tris-guanidinate and tris-amidinate complexes of cerium (Ce) and ytterbium (Yb) were synthesized and thoroughly characterized.

From Precursor Chemistry to Gas Sensors: Plasma-Enhanced Atomic Layer Deposition Process Engineering for Zinc Oxide Layers from a Nonpyrophoric Zinc Precursor for Gas Barrier and Sensor Applications.

The identification of bis-3-(N,N-dimethylamino)propyl zinc ([Zn(DMP) ], BDMPZ) as a safe and potential alternative to the highly pyrophoric diethyl zinc (DEZ) as atomic layer deposition (ALD) precursor for ZnO thin films is reported. Owing to the intramolecular stabilization, BDMPZ is a thermally stable, volatile, nonpyrophoric solid compound, however, it possesses a high reactivity due to the presence of Zn-C and Zn-N bonds in this complex. Employing this precursor, a new oxygen plasma enhanced (PE)ALD process in the deposition temperature range of 60 and 160 °C is developed.

Potential Precursor Alternatives to the Pyrophoric Trimethylaluminium for the Atomic Layer Deposition of Aluminium Oxide.

New precursor chemistries for the atomic layer deposition (ALD) of aluminium oxide are reported as potential alternatives to the pyrophoric trimethylaluminium (TMA) which is to date a widely used Al precursor. Combining the high reactivity of aluminium alkyls employing the 3-(dimethylamino)propyl (DMP) ligand with thermally stable amide ligands yielded three new heteroleptic, non-pyrophoric compounds [Al(NMe ) (DMP)] (2), [Al(NEt ) (DMP)] (3, BDEADA) and [Al(NiPr ) (DMP)] (4), which combine the properties of both ligand systems. The compounds were synthesized and thoroughly chemically characterized, showing the intramolecular stabilization of the DMP ligand as well as only reactive Al-C and Al-N bonds, which are the key factors for the thermal stability accompanied by a sufficient reactivity, both being crucial for ALD precursors.

Low-Temperature Plasma-Enhanced Atomic Layer Deposition of Tin(IV) Oxide from a Functionalized Alkyl Precursor: Fabrication and Evaluation of SnO-Based Thin-Film Transistor Devices.

A bottom-up process from precursor development for tin to plasma-enhanced atomic layer deposition (PEALD) for tin(IV) oxide and its successful implementation in a working thin-film transistor device is reported. PEALD of tin(IV) oxide thin films at low temperatures down to 60 °C employing tetrakis-(dimethylamino)propyl tin(IV) [Sn(DMP)] and oxygen plasma is demonstrated. The liquid precursor has been synthesized and thoroughly characterized with thermogravimetric analyses, revealing sufficient volatility and long-term thermal stability.

Synthesis of rare-earth metal and rare-earth metal-fluoride nanoparticles in ionic liquids and propylene carbonate.

Decomposition of rare-earth tris(,'-diisopropyl-2-methylamidinato)metal(III) complexes [RE{MeC(N(iPr))}] (RE(amd); RE = Pr(III), Gd(III), Er(III)) and tris(2,2,6,6-tetramethyl-3,5-heptanedionato)europium(III) (Eu(dpm)) induced by microwave heating in the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIm][NTf]) and in propylene carbonate (PC) yield oxide-free rare-earth metal nanoparticles (RE-NPs) in [BMIm][NTf] and PC for RE = Pr, Gd and Er or rare-earth metal-fluoride nanoparticles (REF-NPs) in the fluoride-donating IL [BMIm][BF] for RE = Pr, Eu, Gd and Er. The crystalline phases and the absence of significant oxide impurities in RE-NPs and REF-NPs were verified by powder X-ray diffraction (PXRD), selected area electron diffraction (SAED) and high-resolution X-ray photoelectron spectroscopy (XPS). The size distributions of the nanoparticles were determined by transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) to an average diameter of (11 ± 6) to (38 ± 17) nm for the REF-NPs from [BMIm][BF].

Water assisted atomic layer deposition of yttrium oxide using tris(,'-diisopropyl-2-dimethylamido-guanidinato) yttrium(iii): process development, film characterization and functional properties.

We report a new atomic layer deposition (ALD) process for yttrium oxide (YO) thin films using tris(,-diisopropyl-2-dimethylamido-guanidinato) yttrium(iii) [Y(DPDMG)] which possesses an optimal reactivity towards water that enabled the growth of high quality thin films. Saturative behavior of the precursor and a constant growth rate of 1.1 Å per cycle confirm the characteristic self-limiting ALD growth in a temperature range from 175 °C to 250 °C.

PEALD of SiO and AlO Thin Films on Polypropylene: Investigations of the Film Growth at the Interface, Stress, and Gas Barrier Properties of Dyads.

A study on the plasma-enhanced atomic layer deposition of amorphous inorganic oxides SiO and AlO on polypropylene (PP) was carried out with respect to growth taking place at the interface of the polymer substrate and the thin film employing in situ quartz-crystal microbalance (QCM) experiments. A model layer of spin-coated PP (scPP) was deposited on QCM crystals prior to depositions to allow a transfer of findings from QCM studies to industrially applied PP foil. The influence of precursor choice (trimethylaluminum (TMA) vs [3-(dimethylamino)propyl]-dimethyl aluminum (DMAD)) and of plasma pretreatment on the monitored QCM response was investigated.

Unearthing [3-(Dimethylamino)propyl]aluminium(III) Complexes as Novel Atomic Layer Deposition (ALD) Precursors for Al O : Synthesis, Characterization and ALD Process Development.

Identification and synthesis of intramolecularly donor-stabilized aluminium(III) complexes, which contain a 3-(dimethylamino)propyl (DMP) ligand, as novel atomic layer deposition (ALD) precursors has enabled the development of new and promising ALD processes for Al O thin films at low temperatures. Key for this promising outcome is the nature of the ligand combination that leads to heteroleptic Al complexes encompassing optimal volatility, thermal stability and reactivity. The first ever example of the application of this family of Al precursors for ALD is reported here.