Search results for "Bonding"

Titanium Complexes of Chelating, Dianionic O,S,O‐Bisphenolato Ligands: Syntheses, Characterisation, and Catalytic Activity

2005

Titanium complexes based on 2,2'-thiobis[4-(1,1,3,3-tetramethylbutyl)phenolato] (tbop) are prepared by reaction of TiCl 4 or Ti(NMe 2 ) 4 with the parent biphenol. Three new complexes are reported: [Ti 2 (μ-tbop-κ 3 O,S,O)(μ-tbop-κ 2 O,O)-(tbop-κ 3 O,S,O)Cl 2 ] (1).2CH 3 CN, [Ti 2 (μ-tbop-κ 3 O,S,O) 2 Cl 4 ] (2) and [Ti(tbop-κ 3 O,S,O) 2 ] (3). Substitution of the chlorides in 1 and 2 by 2,6-diisopropylphenolato and imido (NtBu) ligands generates the new compounds [Ti 2 (μ-tbop-κ 3 O,S,O) 2 -Cl 2 (dipp) 2 ] (4).Et 2 O and [Ti 2 (μ-tbop-κ 3 O,S,O) 2 (NtBu) 2 -(NH 2 tBu) 2 ] (5), respectively. Treatment of 5 with crude Me 3 -SiCl, containing Me 3 SiOH, produces [Ti(tbop-κ 3 O,S,O)Cl(O-SiMe 3 …

ChemInform Abstract: Luminescent Ionic Transition Metal Complexes for Light-Emitting Electrochemical Cells

2012

Higher efficiency in the end-use of energy requires substantial progress in lighting concepts. All the technologies under development are based on solid-state electroluminescent materials and belong to the general area of solid-state lighting (SSL). The two main technologies being developed in SSL are light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs), but in recent years, light-emitting electrochemical cells (LECs) have emerged as an alternative option. The luminescent materials in LECs are either luminescent polymers together with ionic salts or ionic species, such as ionic transition-metal complexes (iTMCs). Cyclometalated complexes of IrIII are by far the most utiliz…

Stable Green Electroluminescence from an Iridium Tris-Heteroleptic Ionic Complex

2012

An ionic tris-heteroleptic iridium complex gives green light-emitting electrochemical cells (LECs) with unprecedented performances for this part of the visible spectrum. The devices are very bright (>1000 cd m–2), efficient (∼3%), and stable (>55 h). The novel complex is prepared using a new and efficient synthetic procedure. We show that there is a mixed orbital formation originating from the two different orthometalating ligands resulting in photophysical properties that lie between those of its two bis-heteroleptic analogs. Therefore, tris-heteroleptic complexes provide new avenues for fine-tunning the emission properties and to bridge gaps between a series of bis-heteroleptic complexes.

Shear bond strength of metal brackets to ceramic surfaces using a universal bonding resin.

2017

BACKGROUND: Assure Plus is a recently introduced universal adhesive with the ability to bond to various restorations. This study compared the shear bond strength of brackets bonded to two types of ceramics using conventional bonding agent and Assure Plus. Surface damage caused by debonding was also evaluated. MATERIAL AND METHODS: In this in vitro study, 40 feldspathic and lithium disilicate ceramic discs were sandblasted, etched with 9.6% hydrofluoric acid and divided into two groups. In group 1, silane was applied and air-dried followed by application of Transbond XT primer, which was light-cured. In group 2, Assure Plus was applied and air-dried. In both groups, maxillary central incisor…

A theoretical study of the low-lying states of the anionic and protonated ionic forms of urocanic acid

2000

A multistate second-order perturbation theory (MS−CASPT2) study of the lowest lying states in the electronic spectra of urocanic acid in vacuo is presented. The anionic trans and cis isomers, as well as the biologically important trans protonated ionic structure, are considered. The vertical and 0−0 excitation spectra were computed for each system at the MS−CASPT2/ANO-L level, describing the lowest lying ππ* and nπ* singlet and triplet states. In all three systems, a weakly absorbing ππ* singlet state was observed at ∼4.0 eV in the vertical excitation spectrum, suggesting both a novel assignment and an alternative explanation for the previously described wavelength dependent photochemistry …

New light on an old debate: does the RCN–PtCl2 bond include any back-donation? RCN←PtCl2 backbonding vs. the IR νCN blue-shift dichotomy in organoni…

2019

For a series of organonitrile [RCN (R = Me, CF3, Ph, CH3Ph, CF3Ph)] ligands, the nature of the N–Pt bond in the related cis-/trans-(RCN)2PtCl2 complexes has been computationally investigated by Density Functional Theory. A fragment based bond analysis has been performed in the canonical Kohn–Sham molecular orbitals framework, and it has been ultimately assessed that this bond is characterized both by N→Pt σ and by N←Pt π contributions. Voronoi Deformation Density charges further confirms the occurrence of N←Pt π interactions. Moreover, the Energy Decomposition Analysis-Natural Orbital for Chemical Valence (EDA-NOCV) method shows that the strength of the N←Pt π interaction is not negligible …

Electronic Transitions in Tetrathiafulvalene and Its Radical Cation:  A Theoretical Contribution

2001

The low-lying electronic states of tetrathiafulvalene (TTF) and its radical cation (TTF+) have been studied using the multistate extension of a multiconfigurational second-order perturbation method (MS−CASPT2). The minimum-energy equilibrium geometries optimized at the CASSCF level have a boatlike conformation for the neutral molecule, with no significant barrier toward planarity. A more aromatic planar structure is, however, found for the ionic system. For TTF, the calculations of the vertical excitation energies comprise valence singlet and triplet states as well as the lowest members of the Rydberg series converging to the first ionization limit. Valence doublet states have been consider…

Design and setup of a Linear Friction Welding fixture

2011

300°C SiC Blocking Diodes for Solar Array Strings

2009

Silicon Carbide 300V-5A Ni and W Schottky diodes with high temperature operation capability (up to 300°C) have been fabricated. This paper reports on the stability tests (ESA space mission to Mercury, BepiColombo requirements) performed on these diodes. A DC current stress of 5A has been applied to these diodes at 270°C for 800 hours. These reliability tests revealed both, degradation at the Schottky interface (forward voltage drift) and at the diode top surface due to Aluminum diffusion (bond pull strength degradation). The use of W as Schottky metal allows eliminating the forward voltage drift producing stable metal–semiconductor interface properties. Nevertheless, SEM observations of the…

Improving the Quality Management of the Thermosonic Welding Process of Gold Wires in Automotive Industry

2018

Abstract This scientific paper conducts a study meant to improve the quality management of the thermosonic welding process of gold wires in the automotive industry. Within the large amount of electronic products manufactured worldwide, the gold wire bonding is the preferred technology for creating the needed interconnections in the microelectronic industry. In this paper, the quality management improving starts with an experimental research in the automotive industry, based on the gold wire thermosonic bonding, in terms of: conformal structuring, robustness and integrity of the electrical contacts. The experimental research is based on the processing parameters and on the independent variab…