Copper(I) complexes with tripodal nitrogen-containing neutral ligands such as tris(3,5-diisopropyl-1-pyrazolyl)methane (L1') and tris(3-tertiary-butyl-5-isopropyl-1-pyrazolyl)methane (L3'), and with corresponding anionic ligands such as hydrotris(3,5-diisopropyl-1-pyrazolyl)borate (L1-) and hydrotris(3-tertiary-butyl-5-isopropyl-1-pyrazolyl)borate (L3-) were synthesized and structurally characterized. Copper(I) complexes [Cu(L1')Cl] (1), [Cu(L1')(OClO3)] (2), [Cu(L1')(NCMe)](PF6) (3a), [Cu(L1')(NCMe)](ClO4) (3b), [Cu(L1')(CO)](PF6) (4a), and [Cu(L1')(CO)](ClO4) (4b) were prepared using the ligand L1'. Copper(I) complexes [Cu(L3')Cl] (5) and [Cu(L3')(NCMe)](PF6) (6) with the ligand L3' were also synthesized. Copper(I) complexes [Cu(L1)(NCMe)] (7) and [Cu(L1)(CO)] (8) were prepared using the anionic ligand L1-. Finally, copper(I) complexes with anionic ligand L3- and acetonitrile (9) and carbon monoxide (10) were synthesized. The complexes obtained were fully characterized by IR, far-IR, 1H NMR, and 13C NMR spectroscopy. The structures of both ligands, L1' and L3', and of complexes 1, 2, 3a, 3b, 4a, 4b, 5, 6, 7, and 10 were determined by X-ray crystallography. The effects of the differences in (a) the fourth ligand and the counteranion, (b) the steric hindrance at the third position of the pyrazolyl rings, and most importantly, (c) the charge of the N3 type ligands, on the structures, spectroscopic properties, and reactivities of the copper(I) complexes are discussed. The observed differences in the reactivities toward O2 of the copper(I) acetonitrile complexes are traced back to differences in the oxidation potentials determined by cyclic voltammetry. A special focus is set on the carbonyl complexes, where the 13C NMR and vibrational data are presented. Density functional theory (DFT) calculations are used to shed light on the differences in CO bonding in the compounds with neutral and anionic N3 ligands. In correlation with the vibrational and electrochemical data of these complexes, it is demonstrated that the C-O stretching vibration is a sensitive probe for the "electron richness" of copper(I) in these compounds.

It is widely accepted that immunoglobulin (Ig)E triggers immediate hypersensitivity responses by activating a cognate high-affinity receptor, FcεRI, leading to mast cell degranulation with release of vasoactive and proinflammatory mediators. This apparent specificity, however, is complicated by the ability of IgE to bind with low affinity to Fc receptors for IgG, FcγRII and III. We have addressed the in vivo significance of this interaction by studying IgE-mediated passive systemic anaphylaxis in FcγR-deficient mice. Mice deficient in the inhibitory receptor for IgG, FcγRIIB, display enhanced IgE-mediated anaphylactic responses, whereas mice deficient in an IgG activation receptor, FcγRIII, display a corresponding attenuation of IgE-mediated responses. Thus, in addition to modulating IgG-triggered hypersensitivity responses, FcγRII and III on mast cells are potent regulators of IgE-mediated responses and reveal the existence of a regulatory pathway for IgE triggering of effector cells through IgG Fc receptors that could contribute to the etiology of the atopic response.

High-molar-mass silsesquioxanes (SSQO) based on (3-glycidoxypropyl)trimethoxysilane (GPMS) and (3-methacryloxypropyl)trimethoxysilane (MPMS) were synthesized. The hydrolytic condensation of GPMS was performed using HCOOH (0.1 N) as catalyst, keeping the molar ratio H 2O/Si ) 3. A first step was performed in tetrahydrofuran (THF) at 50°C, followed by a second step in diglycidyl ether of bisphenol A (DGEBA), where temperature was increased in steps up to 140°C. The hydrolytic condensation of MPMS was performed in bulk with HCOOH 98%, at T ) 50 or 70°C, using molar ratios of HCOOH/Si ) 3 or 6. Homogeneous solutions were obtained for both silanes. The reaction was followed by size exclusion chromatography (SEC), and final products were characterized by matrix-assisted ultraviolet laser desorption/ionization time-of-flight mass spectrometry (UV-MALDI-TOF MS), FTIR, and 1 H and 29 Si NMR. Molar-mass distributions showed the presence of clusters corresponding to products formed in different generations. With the aid of UV-MALDI-TOF MS, the different species present in every cluster could be identified for one of the silsesquioxanes derived from MPMS. During the initial stage of the hydrolytic condensation, species with 7-12 Si atoms were produced. They mainly consisted of incompletely condensed polyhedra (species with 1-3 OH per molecule) and ladder-type structures (species with 4 OH per molecule). Species with more OH groups were condensed with a higher probability, giving place to a second generation of products. This process accounts for the presence of a cluster of species with 14-24 Si atoms and the enrichment of the first cluster in the more condensed structures (T 7(OH), T8(OH)2, and T9(OH)). Third and fourth generations of condensation products were also present. Structures of different species may be depicted as combinations of incompletely condensed polyhedra with ladder fragments.