Ga Bonds Research Articles

Gallium–Gallium Bonds As Effective Templates for the Generation of Macrocycles and Supramolecular Entities

Treatment of the tetraalkyldigallium(4) compound R2Ga–GaR2 [1; R = CH(SiMe3)2] with the highly functionalized acids 3- and 4-carboxyphenylthiourea, 7-azaindole-3-carboxylic acid, and 6-aminonicotinic acid afforded macrocyclic compounds in which two or four Ga–Ga bonds are bridged by the respective number of organic spacer ligands. In each reaction two equivalents of CH2(SiMe3)2 per formula unit of 1 were released. The Ga–Ga bonds of the products 2 to 5 are bridged by a carboxylato group and a chelating ligand containing two nitrogen donor atoms or the sulfur and nitrogen atoms of a thiourea group. The thiourea derivatives afforded different species with four or eight gallium atoms in the heterocycles (2 and 3) depending on their substitution patterns (1,3- versus 1,4-positions at the benzene rings). Supramolecular aggregates resulted that had up to 12 THF molecules encapsulated in the heterocycles or bonded to the surface of the molecules via hydrogen bonding or orthogonal dipolar interactions.

High quality Ge epitaxy on GaAs (100) grown by metal-organic chemical vapor deposition

High quality Ge epitaxy on a GaAs (100) substrate was grown by metal-organic chemical vapor deposition using germane. The effects of growth temperature and deposition rate on the quality of the Ge epitaxy are investigated. Significant improvement in surface root-mean-square roughness is observed with increasing Ge growth temperature or deposition rate, while keeping all other deposition parameters unchanged. Investigation of the Ge material quality grown after different GaAs surface preparation conditions shows that Ga rich surfaces are beneficial for smooth Ge surfaces, which is attributed to the formation of Ge–Ga bonds at the initiation of the Ge deposition. The good crystalline quality of grown Ge film was further confirmed by high-resolution X-ray diffraction and secondary ion mass spectrometry characterization.

The structural and electronic properties of type-I clathrates Ba8Cu x Ga16−x Sn30 from first-principle calculations

The effects of Cu–doping concentration on the structural and electronic properties of Ba8Cu x Ga16−x Sn30 (0 ≤ x ≤ 3) type-I clathrate compounds have been investigated by first-principle calculations. Starting with the stable structures of the type-I clathrate semiconductors Ba8Ga16Sn30 containing no Ga–Ga bonds, we have constructed unit cells of Ba8Cu x Ga16−x Sn30. The dependence of the structural and electronic properties of these compounds with x is discussed. The results reveal that the interaction between the rattler atom and the cage is affected by Cu doping, which suggests that Cu doping may play a role on the thermal conductivity. It is shown that the Ba8Ga16Sn30 is an intrinsic semiconductor, but Cu doping leads to p-type transport characteristics. Detailed analysis of the electronic structures for Cu-doped clathrates imply that Cu 3d electrons may display both itinerant and localized features and the electronic states near the top of the valence band are modified by the Cu 3d states. The number of states near the Fermi level is increased by the coupling of sp–d, which may lead to reduced stability of the structure.

Synthesis of Unsupported Ln–Ga Bonds by Salt Metathesis and Ga–Ga Bond Reduction

Three gallyl lanthanide complexes [{(dipp-Bian)Ga}2Ln(thf)4] (Ln = Sm, Eu, Yb; dipp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene), in which the lanthanide atoms are coordinated by only two {(dipp-Bian)Ga}− ligands and THF, are reported. Two unsupported Ln–Ga bonds are found in each compound. The gallyl lanthanide complexes have been obtained by two synthetic pathways: (1) reductive insertion of the lanthanide metals into the Ga–Ga bond of [{(dipp-Bian)Ga}]2 and (2) salt metathesis of [(dipp-Bian)GaK(thf)5] with LnI2. Moreover, the samarium compound [{(dipp-Bian)Ga}2Sm(thf)4] was additionally obtained in a reductive pathway from SmI3 and [(dipp-Bian)GaK(thf)5]. The length of the Ln–Ga bond strongly depends on packing effects. The reaction of TmI2(thf)5 and [(dipp-Bian)GaK(thf)5] gave the Tm(III) complex [{(dipp-Bian)Ga–Ga(dipp-Bian)}(C4H8O)TmI(thf)5], in which one THF ring was opened and reduced twice, forming the formal double negative charged anion (O-CH2-CH2-CH2-CH2)2–. This thulium compound...

Ab Initio Analysis of the Interactions of GaN Clusters with Oxygen and Water

We calculate the interactions of oxygen and water with the Ga-face of GaN clusters, which could be used as testbeds for the actual Ga-face on GaN crystals of importance in electronics; however, our additional goal is the analysis of the nanoclusters for several other applications in nanotechnology. Our results show that the local spin plays an important role in these interactions. It is found that the most stable interaction of O2 and the GaN clusters results in the complete dissociation of the O2 molecule to form two Ga–O–Ga bonds, while the most stable interaction between a H2O molecule and the GaN clusters is the complete dissociation of one of the O–H bonds to form a Ga–O–H bond and a Ga–H bond.

Structure and bonding analysis of dimethylgallyl complexes of cobalt, rhodium and iridium [Me(PMe3)2(Me3GaCl)M(GaMe2)] (M = Co, Rh, Ir) and [Me(PMe3)2ClIr(GaMe2)]: A theoretical study

Electronic, molecular structures and bonding analysis of the terminal neutral dimethylgallyl complexes of cobalt, rhodium and iridium [Me(PMe3)2(Me3GaCl)M(GaMe2)] (M = Co, Rh, Ir) and [Me(PMe3)2ClIr(GaMe2)] were investigated at the DFT/BP86/TZ2P/ZORA level of theory. The calculated geometry of dimethylgallyl iridium complex [Me(PMe3)2(Me3GaCl)M(GaMe2)] is in excellent agreement with structurally characterized iridium complex. Mayer bond order of the optimized structures shows that the M–Ga bonds in these complexes are essentially M–Ga single bond, which is also supported by the performed energy decomposition analysis. The orbital interactions between the metal and gallium arise mainly from M ← GaMe2 σ donation. In all complexes, the π-bonding contribution is relatively smaller. The absolute values of the ΔEPauli, ΔEint and ΔEelstat contributions to the M–Ga bonds increase according to M = Co < Rh < Ir.

Density functional theory simulations of amorphous high-κ oxides on a compound semiconductor alloy: a-Al2O3/InGaAs(100)-(4×2), a-HfO2/InGaAs(100)-(4×2), and a-ZrO2/InGaAs(100)-(4×2)

The structural properties of a-Al(2)O(3)∕In(0.5)Ga(0.5)As, a-HfO(2)∕In(0.5)Ga(0.5)As, and a-ZrO(2)∕In(0.5)Ga(0.5)As interfaces were investigated by density-functional theory (DFT) molecular dynamics (MD) simulations. Realistic amorphous a-Al(2)O(3), a-HfO(2), and a-ZrO(2) samples were generated using a hybrid classical-DFT MD "melt-and-quench" approach and tested against the experimental properties. For each stack type, two systems with different initial oxide cuts at the interfaces were investigated. All stacks were free of midgap states, but some had band-edge states which decreased the bandgaps by 0%-40%. The band-edge states were mainly produced by deformation, intermixing, and bond-breaking, thereby creating improperly bonded semiconductor atoms. The interfaces were dominated by metal-As and O-In∕Ga bonds which passivated the clean surface dangling bonds. The valence band-edge states were mainly localized at improperly bonded As atoms, while conduction band-edge states were mainly localized at improperly bonded In and Ga atoms. The DFT-MD simulations show that electronically passive interfaces can be formed between high-κ oxides dielectrics and InGaAs if the processing does not induce defects because on a short time scale the interface spontaneously forms electrically passive bonds as opposed to bonds with midgap states.

The nature of M–Ga in metal(I) gallyl complexes of copper, silver and gold: A theoretical study

Density Functional Theory calculations have been performed for the gallyl complexes [(NHC)M{Ga(N(Ph)C(H)) 2}] (NHC = :C(N(Ph)C(H)) 2; I M = Cu, II M = Ag, III M = Au) at the DFT/BP86/TZ2P/ZORA level of theory. The calculated geometries of the studied complexes are in good agreement with structurally characterized gallyl complexes of copper, silver and gold. The M–Ga bond distances as well as Pauling and Mayer bond orders of the M–Ga bonds suggest that the M–Ga bonds in these complexes are nearly M–Ga single bond. The π–bonding component of the total orbital contribution is significantly smaller than that of σ–bonding. Thus, in these complexes the Ga(N(Ph)C(H)) 2 ligand behaves predominantly as an σ–donor. The contributions of the electrostatic interaction terms ΔE elstat are significantly larger in all gallyl complexes than the covalent bonding ΔE orb term. The absolute values of the ΔE int and ΔE(De) contributions to the M–Ga bonds display a V-like trend, with a minimum at the silver complex.

ChemInform Abstract: Two New Cluster Ions, Ga[GaH3]5‐4 with a Neopentane Structure in Rb8Ga5H15 and [GaH2]n‐n with a Polyethylene Structure in Rbn(GaH2)n, Represent a New Class of Compounds with Direct Ga—Ga Bonds Mimicking Common Hydrocarbons.

AbstractThe title compounds are prepared from mixtures of Ga and Rb under 5 MPa H2 at 573 K and characterized by powder XRD and neutron powder diffraction.

Theoretical Study of Gallium Nitride Crystal Growth Reaction Mechanism

In this work, we investigate GaN(0001) crystal growth focusing on gas-phase and surface reactions from the viewpoint of metalorganic chemical vapor deposition (MOCVD) by ab initio calculations. We consider the adsorption of compounds of Ga and N atoms on a Ga-covered surface cluster model. For the adsorption of these compounds, it is found that Ga–Ga bonds undesirable for the steady growth appear for alkylgallium with amino group, and the compounds which have coordinate bonds with NH3 can be a solution for this problem, since they do not make Ga–Ga bonds.

Tuning Surface Wettability of InxGa(1–x)N Nanotip Arrays by Phosphonic Acid Modification and Photoillumination

We report a facile route to reversibly tune surface wettability of In(x)Ga((1-x))N (InGaN) nanotip arrays by octylphosphonic acid (OPA) modification and ultraviolet-visible (UV-vis) light illuminations. Well-aligned InGaN nanotip arrays were grown by chemical vapor deposition (CVD). OPA was covalently attached to the InGaN nanotip surface, which was initially oxidized in Piranha solution. Because of the high surface energy of polar groups, OPA-coated InGaN nanotip arrays demonstrated superhydrophobic properties (contact angle of 154°). Transitions between superhydrophobicity and hydrophilicity were obtained through OPA adsorption and UV-vis light illumination. The InGaN nanotip surface chemistry was further characterized by X-ray photoelectron spectroscopy (XPS), which suggested a scission mechanism at P-C and MO-P (M = In and Ga) bonds of bound OPA molecules. Meanwhile, no significant surface degradation was observed after the OPA modification and phototreatments.

Reactions of the Tetraalkyldigallium Compound R2Ga–GaR2 [R = CH(SiMe3)2] with Acidic Reagents, Retention vs. Cleavage of the Ga–Ga Bond and Formation of Supramolecular Aggregates via Hydrogen Bonding

AbstractTreatment of the tetraalkyldigallium compound R2Ga–GaR2 [1, R = CH(SiMe3)2] with two equivalents of carboxylic acid hydrazides (4‐trifluormethylbenzhydrazide, 2‐fuoric acid hydrazide and 2‐chlor‐6‐hydrazineisonicotinic acid hydrazide) afforded new digallium species by the release of CH2(SiMe3)2. The intact Ga–Ga bonds of the products (2 to 4) are terminally coordinated by two chelating hydrazide ligands via NH2 groups and the carbonyl oxygen atoms. Interesting supramolecular aggregates are formed in the solid state, which contain dimeric formula units of the digallium species connected via a complex system of hydrogen bonds. Two ether molecules are additionally coordinated to terminal N–H functions. Phenylphosphinic acid and 1 gave the analogous substituent replacement reaction with the formation of a dimeric tetragallium compound (5). Its two Ga–Ga bonds are in a perpendicular arrangement with four phosphinate ligands in the bridging positions. Oxidation of the gallium atoms and insertion of an N=N double bond into the Ga–Ga bond was observed upon treatment of 1 with azodicarbonamide.

PL and XPS study of radiation damage created by various slow highly charged heavy ions on GaN epitaxial layers

Photoluminescence (PL) spectrum, in conjunction with X-ray photoelectron spectroscopy (XPS) is used to evaluate the surface damage of GaN layer by highly-charged Xe q+ (18 ⩽ q ⩽ 30), Ar q+ (6 ⩽ q ⩽ 16) and Pb q+ ( q = 25,35) ions. The intensity of PL emission of GaN layer, including near band-edge peak and yellow luminescence, decreases with increasing fluence and charge state of the incident ions. Finally the PL emission is completely quenched after irradiation to high fluences at high charge state. A new peak at 450 nm appeared in PL spectra of the specimens irradiated with Xe 18+, Ar 6+ and Ar 11+, indicating that radioactive recombination within donor–acceptor pairs (DAPs) during irradiation. After irradiation, XPS spectra show N deficient or Ga rich on GaN surface and XPS spectra of Ga3d core levels indicate spectral peak evidently shifts from a Ga–N to Ga–Ga and Ga–O bond. The relative content of Ga–N bond decreases and the content of Ga–Ga bond increases with the increase of ion fluence and ion charge state. The binding energy of Ga3d 5/2 electron corresponding to Ga–Ga bond of the irradiated GaN film is found to be smaller than that of metallic Gallium (Ga 0), which can be attributed to irradiation damage.

Structure and bonding in haloarylgallyl complexes of iron, ruthenium and osmium [(η 5-C 5H 5)(CO) 2M{Ga(X)(Ph)}]: A theoretical study

Density Functional Theory calculations have been performed for the halophenylgallyl complexes of iron, ruthenium and osmium [(η 5-C 5H 5)(CO) 2M(Ga(X)Ph)] (M = Fe, Ru, Os; X = Cl, Br, I) at the DFT/BP86/TZ2P/ZORA level of theory. The calculated geometry of iron complexes [(η 5-C 5H 5)(CO) 2Fe(Ga(Cl)Ph)] and [(η 5-C 5H 5)(CO) 2Fe(Ga(I)Ph)] is in excellent agreement with structurally characterized complexes [(η 5-C 5H 5)(CO) 2Fe(Ga(Mes ∗)Cl)], [(η 5-C 5Me 5)(CO) 2Fe(Ga(Mes ∗)Cl)] and [(η 5-C 5Me 5)(CO) 2Fe(Ga(Mes)I)] (Mes = C 6H 2Me 3-2,4,6; Mes ∗ = C 6H 2 tBu 3-2,4,6). The M–Ga bond distances as well as Mayer bond order of the M–Ga bonds suggest that the M–Ga bonds in these complexes are nearly M–Ga single bond. The π-bonding component of the total orbital contribution is significantly smaller than that of σ-bonding. Thus, in these complexes the Ga(X)Ph ligand behaves predominantly as a σ-donor. The contributions of the electrostatic interaction terms Δ E elstat are significantly smaller in all gallyl complexes than the covalent bonding Δ E orb term. The absolute values of the Δ E Pauli, Δ E int and Δ E elstat contributions to the M–Ga bonds increase in both sets of complexes via the order Fe < Ru < Os. In the complexes [(η 5-C 5H 5)(Me 3P) 2Fe(Ga(X)Ph)] (X = Cl, Br, I), interaction energy as well as bond dissociation energy decrease upon going from X = Cl to X = I.

Structure and Bonding Analysis of Dimethylgallyl Complexes of Iron, Ruthenium, and Osmium [(η5-C5H5)(CO)2M(GaMe2)] and [(η5-C5H5)(Me3P)2M(GaMe2)

Density functional theory calculations have been performed for the dimethylgallyl complexes of iron, ruthenium, and osmium [(η(5)-C(5)H(5))(L)(2)M(GaMe(2)] (M = Fe, Ru, Os; L = CO, PMe(3)) at the DFT/BP86/TZ2P/ZORA level of theory. The calculated geometry of the iron complex [(η(5)-C(5)H(5))(CO)(2)Fe(GaMe(2))] is in excellent agreement with structurally characterized complex [(η(5)-C(5)H(5))(CO)(2)Fe(Ga(t)Bu(2))]. The Pauling bond order of the optimized structures shows that the M-Ga bonds in these complexes are nearly M-Ga single bond. Upon going from M = Fe to M = Os, the calculated M-Ga bond distance increases, while on substitution of the CO ligand by PMe(3), the calculated M-Ga bond distances decrease. The π-bonding component of the total orbital contribution is significantly smaller than that of σ-bonding. Thus, in these complexes the GaX(2) ligand behaves predominantly as a σ-donor. The contributions of the electrostatic interaction terms ΔE(elstat) are significantly smaller in all gallyl complexes than the covalent bonding ΔE(orb) term. The absolute values of the ΔE(Pauli), ΔE(int), and ΔE(elstat) contributions to the M-Ga bonds increases in both sets of complexes via the order Fe < Ru < Os. The Ga-C(CO) and Ga-P bond distances are smaller than the sum of van der Waal radii and, thus, suggest the presence of weak intermolecular Ga-C(CO) and Ga-P interactions.

Structure and bonding analysis of dihalogallyl and dimethylgallyl complexes of molybdenum and tungsten [(η 5-C 5H 5)(CO) 3M(GaX 2)] (M = Mo, W; X = Cl, Br, I, Me): A theoretical study

The electronic, molecular structures and bonding of the terminal neutral dihalogallyl and dimethylgallyl complexes of molybdenum and tungsten [(η 5-C 5H 5)(CO) 3M(GaX 2)] (M = Mo, W; X = Cl, Br, I, Me) were investigated at the DFT/BP86/TZ2P/ZORA level of theory. The calculated geometry of molybdenum complex [(η 5-C 5H 5)(CO) 3Mo(GaMe 2)] is in excellent agreement with structurally characterized complex [(η 5-C 5H 5)(CO) 3Mo(Ga tBu 2)]. The Pauling bond order of the optimized structures shows that the M–Ga bonds in these complexes are nearly M–Ga single bond. The gallium bound substituent exerts an influence on the length of the M–Ga bonds. The M–Ga bond distances are longer for dimethylgallyl complexes than the dihalogallyl complexes. The Mayer bond order of the M–Ga bonds decrease on going from X = Cl to Me, indicating progressive weakening of the M–Ga bond. The M–Ga σ bonding orbitals are significantly polarized towards the metal atom. The π-bonding component of the total orbital contributions is significantly smaller than that of σ-bonding. Thus, in these complexes the GaX 2 ligand behaves predominantly as a σ-donor. Orbital contributions for the interactions between neutral fragments [(η 5-C 5H 5)(CO) 3M] and [GaX 2] are larger while the electrostatic interactions, interaction energies and bond dissociation energies are significantly smaller than the values obtained for the interactions between ionic fragments [(η 5-C 5H 5)(CO) 3M] + and [GaX 2] − . The Ga–C(CO) bond distances are smaller than the sum of van der Waal radii (Ga–C(CO) = 2.60 Å) and thus, suggest the presence of weak inter-molecular Ga–C(CO) interactions.

Synthesis of a Large Functional Cage Compound Based on Four GaGa Single Bonds and Its Application as an Oligoacceptor: On the Way to Bio‐Organogallium Hybrid Molecules

The digallium compound R(2)Ga-GaR(2) (1; R=CH(SiMe(3))(2)) reacts with citracinic acid by the release of two equivalents of bis(trimethylsilyl)methane and the formation of a unique oligofunctional cage compound (2). Four Ga-Ga bonds in a tetrahedral arrangement are bridged by four spacer ligands that are located on the faces of the tetrahedron and bridge the gallium atoms of three different Ga-Ga bonds. Four pyridinium groups result from the shift of one of the three acidic protons of four citracinic acid molecules to the nitrogen atoms of the aromatic rings. The N-H groups are arranged in pairs and are capable of acting as chelating acceptors for the coordination of THF molecules (2(THF)(2)) or the nitrogen atoms of 1-deazapurine (3(OEt(2))(4)). In particular, the last reaction verifies the potential applicability of this relatively water- and air-resistant acceptor compound for the generation of bioorganometallic hybrid molecules.

Synthesis and structure of new compounds with Pt–Ga bonds: Insertion of the bulky gallium (I) bisimidinate Ga(DDP) into Pt–Cl bond

Reactions of the sterically bulky mono-valent group 13 bisimidinate gallium(I), Ga(DDP) ( 1) (DDP = 2-{(2, 6-diisopropylphenyl)amino}-4-{(2, 6-diisopropylphenyl)imino}-2-pentene, HC(CMeNC 6H 3-2,6- i Pr 2) 2) with olefin supported group 10 complexes, [(diene)PtCl 2] [diene = 1,5-cyclooctadiene (COD), endo-dicyclopentadiene (dcy)] and [(COD)Pd(Me)(OTf)] (OTf = O 3SCF 3) are reported. These reactions afforded [(COD)Pt(Cl){ClGa(DDP)}] ( 2), [(dcy)Pt(Cl){ClGa(DDP)}] ( 3) and [(DDP)Ga(Me)(OTf)] ( 4) in moderate yields. Compounds 2– 4 were characterized by elemental analysis, NMR ( 1H, 13C) spectroscopy and also by single crystal X-ray structural analysis. The solid state structures of complexes 2 and 3 reveal the oxidative insertion of Ga(DDP) into the Pt–Cl bond without altering the π-coordinated double bonds in the olefin.

Gallium–Gallium Bonds Bridged by Functionalized Carboxylato Ligands

AbstractTreatment of the tetraalkyldigallium compound R2Ga–GaR2 [R = CH(SiMe3)2] (1) with a large number of different functionalized carboxylic acids afforded dicarboxylatodigallium compounds R2Ga2(μ‐O2C–R)2, in which two carboxylato ligands bridge the Ga–Ga bonds. The chelating ligands have additional nitrogen, oxygen or phosphorus donor atoms and may be suitable to act as Lewis‐bases to yield supramolecular aggregates in future investigations. Four compounds have been characterized by crystal structure determinations. One gave unprecedented dimeric formula units in the solid state by Ga–N interactions. The similar reaction with isonicotinic acid resulted in the cleavage of the Ga–Ga bond. A tetragallium compound was formed in which four isolated metal atoms were bridged by four organic ligands to give a square molecular core.

Reaktionen der Digalliumverbindung R2Ga–GaR2 [R = CH(SiMe3)2] mit Wasser und Carbonsäuren – Synthese von μ‐Hydroxo‐μ‐carboxylatodigallium‐Verbindungen unter Erhalt der Ga–Ga‐Bindungen

AbstractTreatment of the digallium compound R2Ga–GaR2 [1, R = CH(SiMe3)2] with a broad variety of functionalized carboxylic acids in the presence of water yielded μ‐hydroxo‐μ‐carboxylatodigallium compounds (2–10) containing intact Ga–Ga bonds in high to moderate yields. The compounds form dimeric formula units in which the unsupported Ga–Ga bonds are bridged by two hydroxo and two carboxylato ligands. Each gallium atom is terminally coordinated by a bulky alkyl group. NMR spectroscopy revealed mixtures of two isomeric compounds in solution in all cases. The second component may show a different bridging mode with each Ga–Ga bond bridged by a bidentate carboxylato ligand to form Ga2O2C five‐membered heterocycles.