Gallium Acetylacetonate Research Articles

Novel gallium(III) complexes transported by MDR1 P-glycoprotein: potential PET imaging agents for probing P-glycoprotein-mediated transport activity in vivo

Background: Multidrug resistance (MDR) mediated by expression of MDR1 P-glycoprotein (Pgp) represents one of the best characterized barriers to chemotherapy in cancer patients. Positron emission tomography (PET) agents for analysis of Pgp-mediated drug transport activity in vivo would enable noninvasive assessment of chemotherapeutic regimens and MDR gene therapy. Results: Candidate Schiff-base phenolic gallium(III) complexes were synthesized from their heptadentate precursors and gallium(III)acetylacetonate. Crystal structures demonstrated a hexacoordinated central gallium with overall trans-pseudo-octahedral geometry. Radiolabeled 67Ga-complexes were obtained in high purity and screened in drug-sensitive (Pgp −) and MDR (Pgp +) tumor cells. Compared with control, lead compound 6 demonstrated antagonist-reversible 55-fold lower accumulation in Pgp-expressing MDR cells. Furthermore, compared with wild-type control, quantitative pharmacokinetic analysis showed markedly increased penetration and retention of 6 in brain and liver tissues of mdr1a/b (−/−) gene disrupted mice, correctly mapping Pgp-mediated transport activity at the capillary blood–brain barrier and hepatocellular biliary cannalicular surface in vivo. Conclusions: These results indicate that gallium(III) complex 6 is recognized by MDR1 Pgp as an avid transport substrate, thereby providing a useful scaffold to generate 68Ga radiopharmaceuticals for molecular imaging of Pgp transport activity in tumors and tissues in vivo using PET.

Synthesis of Rare‐Earth Gallium Garnets by the Glycothermal Method

Single‐phase rare‐earth gallium garnets were obtained by the reaction of stoichiometric mixtures of gallium acetylacetonate and rare‐earth (Nd‐Lu) acetates in 1,4‐butanediol at 300°C (glycothermal reaction). Particles of gadolinium gallium garnet (GGG) and other gallium garnets with rare‐earth elements larger than Gd were spherical with diameters of 0.5‐2 μm, while particles of garnets with smaller rare‐earth ions (Tb‐Lu and Y) were much smaller (100‐300 nm) with particle size distributed in a quite narrow range. TEM observation revealed that each particle was essentially a single crystal grown from one nucleus, but that defects frequently occurred during the crystal growth. Cerium and praseodymium gallium garnets were also formed when the reaction was carried out in the presence of GGG seed crystals. Hydrothermal reactions of the same starting materials under identical conditions yielded mixtures of gamma‐Ga2O3 and the garnet phase.

Gallium Phosphate Thin Films: Synthesis and Dielectric Properties

Deposits of dielectric gallium phosphate thin films on silicon and gallium arsenide semiconductors have been obtained by pyrolysis of an aerosol produced by ultrasonic spraying (“pyrosol” process) and containing the organometallic precursors gallium acetylacetonate and tributyl phosphate. The composition and microstructure of the layers are discussed with respect to the experimental conditions. For this paper, electrical properties were also studied. Using the metal–insulator–semiconductor structure, the behavior of conductivity under direct current, capacitance, and dielectric loss was studied in terms of frequency, temperature, and chemical composition. The sites involved in the conduction process are structural defects directly related to the oxygen excess present in deposits which leads to the formation ofM–O dangling bonds (M=Ga or P).

Growth of gallium oxide thin films from gallium acetylacetonate by atomic layer epitaxy

Gallium oxide thin films have been deposited by atomic layer epitaxy (ALE) using Ga(acac)3(acac = pentane-2,4-dionate) and either water or ozone as precursors. Films were grown on silicon (100), soda lime and Corning glass substrates. The influence of the deposition parameters (e.g. pulse duration, growth and source temperatures) on film growth were studied and by a proper choice of the parameters a self-controlled growth was demonstrated around 370°C. Spectrophotometry, X-ray diffraction (XRD), Rutherford back-scattering spectroscopy (RBS) and X-ray photoelectron spectroscopy (XPS) were used to determine the refractive index, thickness, crystallinity and stoichiometry of the films. All the films were amorphous and highly uniform with only small thickness variations. The films deposited with water contained a considerable amount of carbon as an impurity whereas ozone as an oxidizer gave stoichiometric Ga2O3 films.

Low temperature deposition of gallium phosphate amorphous dielectric thin films by aerosol CVD

Gallium phosphate thin films on silicon substrates have been made from gallium acetylacetonate and tributylphosphate precursors in solution by an aerosol chemical vapor deposition named ‘pyrosol’. Thin films produced are amorphous and a large range of chemical compositions with the experimental conditions can be observed. The X-ray absorption measurement results show that in these thin film structures there are Ga atoms in both tetrahedral and octahedral sites. Their electrical (resistivity) and dielectric (permittivity) characteristics are different to those of the crystallized gallium phosphate.

GaAs Quantum Dots

AbstractGaAs quantum dots have been prepared by reacting gallium acetylacetonate with trimethylsilylarsine in triethylene glycol ether at 216 K. The colloidal dispersion of GaAs nanocrystals has been characterized by transmission electron microscopy, electron diffraction, ultrafiltration, optical absorption and photoluminescence spectroscopy, and transient pump‐probe spectroscopy; the spectral data were also fitted to a model that accounts for the size‐dependent optical properties of a Gaussian distribution of particle sizes. Our results indicate that the spectral region above 470 nm can be assigned solely to GaAs nanocrystals having a mean diameter of 40.0 Å with a standard deviation of 9.7 Å. The origin of spectral features below 470 nm has not yet been determined conclusively.

Reactions of 15-crown-5 and bis-15-crown-5 ethers with metal acetylacetonate ions in the gas phase

1. A study was carried out on the ion-molecule reactions of ions arising in the dissociation of ferric, cobaltic, chromic, manganous, neodymium(II), gallium(III), and indium(III) acetylacetonates upon electron impact with 15-crown-5 and bis-15-crown-5. 2. The ratio of the yields of (acac)xM+L andx-1M+L ions (M is a metal, L is a macrocyclic ligand, and x=1 or 2) is determined by the case of reductionof M(x+1)+ to Mx+ and for (acac)3M complexes, this ratio decreases in the series Nd, In, Ga>Cr>Fe, Co. The rate constant for the formation of acacCoL+ ions is greater than for acacFeL+ ions. 3. The possibility of fixing transition metals in unstable oxidation states by crown ethers was demonstrated in the case of nickel.

Metal nucleus quadrupole coupling constants in aluminum, gallium, and indium acetylacetonates

The 13C spin-lattice relaxation times for the methine carbons of the ligand in the series of M( acac) 3 complexes where M = Al, Ga, In were measured at different temperatures and used to determine the rotational correlation times for the complexes. The linewidth measurements for the quadrupolar metal nuclei permitted, in combination with the correlation times from 13C measurements, the determination of the nuclear quadrupole coupling constants for 27Al, 69Ga, 71Ga, and 115In in the complexes in solution. All the quadrupole coupling constants were found to be temperature independent (within experimental accuracy) and consistent with slightly distorted octahedral structures. The trend in the quadrupole coupling constants as a function of the central atom in the series is discussed briefly.

Low temperature emission spectra of metal acetylacetonates

The phosphorescent properties of closed shell metal chelates have been studied in EPA at 77°K. The compounds investigated include the acetylacetonates of magnesium and Group III-A metal ions (Al, Ga, In) as well as the trifluoroacetylacetonate and hexafluoroacetylacetonate chelates of aluminum. The results indicate that although the metal center does not greatly affect the position or vibronic structure of the acetylacetonate luminescence it is important in both intersystem crossing and radiative coupling to the ground state in these systems. It is also concluded that there is little or no interaction between the ligand rings in the emitting triplet state. Altering the electron distribution in the ligand ring by successively replacing the −CH 3 groups with −CF 3 groups results in a red shift in the location of the emission and a marked alteration in the vibronic envelope. The luminescence of single crystals of aluminum, indium and gallium acetylacetonate has also been investigated. All three crystals exhibit a broad, short-lived emission which is assigned as fluorescence from an excimer-like configuration.

The partial resolution of certain inner complexes by means of a chromatographic technique

Adsorption of chromium(II) or cobalt(III) acetylacetonate on a column of d-lactose hydrate followed by elution with n-hexane-benzene or petroleum ether-benzene effects partial resolution into optically active fractions. Complete recovery of solute characterizes both systems. The same techniques yields only optically inactive fractions with iron(III), gallium(III), and indium(III) acetylacetonates.