The structures of a series of beryllium containing complexes have been optimized at the B3LYP/6-31G(d) level and their (9)Be magnetic shielding values have been determined using B3LYP/6-311G+g(2d,p) and the gauge-including atomic orbital (GIAO) method. The calculated chemical shifts are in excellent agreement with experimental values. The performance of a variety of NMR methods (SGO, IGAIM, CSGT) were also examined but were found to be inferior to the GIAO method at the chosen level of theory employed. The theoretical method has been utilized to predict the beryllium chemical shifts of structurally characterized complexes for which no measured (9)Be NMR spectrum exists, and to investigate a literature complex with an unusual (9)Be NMR chemical shift. A new standard for beryllium NMR in nonaqueous solvents has been suggested.
The convenient five-coordinate starting materials, Salen((t)Bu)AlCl (Salen((t)Bu) = N,N'-alkylene (or arylene) bis (3,5-di-tert-butyl-2-hydroxybenzylideneamine) (1-4) can be used in a wide range of reactions to form five-coordinate aluminum compounds. Herein, these reagents were used to produce new five-coordinate azides, LAlN(3) (L = Salen((t)Bu) (5), Salpen((t)Bu) (6), and Salomphen((t)Bu) (7)) through trimethylsilylhalide elimination. The decomposition of the azides produce first hydroxide (LAlOH (L = Salen((t)Bu) (8)) and, subsequently in the presence of chlorotrimethylsilane, the siloxide compounds, LAlOSiMe(3) (L = Salen((t)Bu) (9), Salpen((t)Bu) (10), and Salomphen((t)Bu) (11)). Alkane elimination reactions may also be used to access this type of compound as evidenced by the formation of Salomphen((t)Bu)AlOSiPh(3) (12). Additionally, the first structurally characterized five-coordinate monomeric amide, Salcen((t)Bu)AlN(SiMe(3))(2) (13), can prepared by a salt elimination utilizing Salcen((t)Bu)AlCl (4). The compounds were characterized by spectroscopic methods ((1)H and (27)Al NMR, MS, and IR) and, in the case of 2 (Salpen((t)Bu)AlCl), 3 (Salomphen((t)Bu)AlCl) 9, 11, 12, and 13, by X-ray analysis. Several of the compounds were explored as potential catalysts for the living polymerization of propylene oxide.
The Salen(tBu) ligand and its derivatives were used to prepare binuclear boron complexes. These compounds have the formula, L(BBr2)2 (L = Salpen(tBu) and Salben(tBu)). These are formed from the reaction of the corresponding L[B(OMe)2]2 with BBr3. They represent a new type of binuclear boron compound. These compounds are active towards the dealkylation of many phosphates. They are also catalytically active with a stoichiometric amount of BBr3 to trimethylphosphate.
Chronic beryllium disease is a lung disorder caused by beryllium exposure in the workplace and is characterized by granulomatous inflammation and the accumulation of beryllium-specific, HLA-DP2-restricted CD4+ T lymphocytes in the lung that proliferate and secrete Th1-type cytokines. To characterize the interaction among HLA-DP2, beryllium, and CD4+ T cells, we constructed rHLA-DP2 and rHLA-DP4 molecules consisting of the α-1 and β-1 domains of the HLA-DP molecules genetically linked into single polypeptide chains. Peptide binding to rHLA-DP2 and rHLA-DP4 was consistent with previously published peptide-binding motifs for these MHC class II molecules, with peptide binding dominated by aromatic residues in the P1 pocket. 9Be nuclear magnetic resonance spectroscopy showed that beryllium binds to the HLA-DP2-derived molecule, with no binding to the HLA-DP4 molecule that differs from DP2 by four amino acid residues. Using beryllium-specific CD4+ T cell lines derived from the lungs of chronic beryllium disease patients, beryllium presentation to those cells was independent of Ag processing because fixed APCs were capable of presenting BeSO4 and inducing T cell proliferation. Exposure of beryllium-specific CD4+ T cells to BeSO4-pulsed, plate-bound rHLA-DP2 molecules induced IFN-γ secretion. In addition, pretreatment of beryllium-specific CD4+ T cells with BeSO4-pulsed, plate-bound HLA-DP2 blocked proliferation and IL-2 secretion upon re-exposure to beryllium presented by APCs. Thus, the rHLA-DP2 molecules described herein provide a template for engineering variants that retain the ability to tolerize pathogenic CD4+ T cells, but do so in the absence of the beryllium Ag.
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