Design, Synthesis, and Chemistry of Sterically Nondemanding Primary Bisphosphines1

A General Strategy for Increasing the Air Stability of Phosphines Including Primary Phosphines

A general approach for increasing the air-stability of various primary phosphines in the absence of kinetic stabilization is presented that contrasts with previous interpretations, which were limited to specific phosphines. This contribution shows the synthesis of a series of air-stable primary phosphines Fc(CH2 )n PH2 , where n=0,1,2,3; and Fc=ferrocenyl, and their corresponding isolable primary phosphine oxides. It was demonstrated that the ferrocene moiety exerts an antioxidant effect on the primary phosphine group, which is intermolecular, solvent dependent and increases with the electron density on the ferrocene moiety. Furthermore, we demonstrated that the presence of ferrocene in solution also inhibits the oxidation of other secondary and tertiary phosphines in air. Together our findings suggest that quenching of singlet oxygen is the actual reason for the antioxidant effect; this was experimentally confirmed by using other established singlet oxygen quenchers, thus demonstrating a key role of singlet oxygen in the aerobic oxidation of phosphines.

Preparations of metal trichalcogenophosphonates from organophosphonate esters

A new method for the preparation of metal trichalcogenophosphonates is presented wherein organophosphonate esters are first reduced with LiAlH(4) and subsequently treated with an organometallic reagent and elemental sulfur or selenium to give the desired trichalcogenophosphonate complex. Using this synthetic protocol with (n)BuLi as the organometallic reagent, the lithium trithiophosphonate complexes [Li(2)(S(3)PCH(2)Ph)(THF)(TMEDA)](2) (1) and [Li(4)(S(3)P(n)Pr)(2)(TMEDA)(3)](∞) (3), where THF = tetrahydrofuran and TMEDA = N,N,N',N'-tetramethylethylenediamine, have been prepared. In both cases, the formation of byproducts is also evident, including, for 1, the tetrathiohypodiphosphonate complex [(PhCH(2)P(S(2)))(2)Li(2)(THF)(4)] (2), which has been structurally characterized. Replacement of (n)BuLi with (n)Bu(2)Mg as the metallating agent led to much cleaner products and improved yields, with the new trithio- and triselenoorganophosphonate complexes [Mg(S(3)PCH(2)Ph)(TMEDA)](2) (4) and [Mg(Se(3)P(n)Pr)(TMEDA)](2) (5) reported. All trichalcogenophosphonate complexes have been structurally characterized in the solid state: 1 adopts a dimer structure in which the [PhCH(2)PS(3)](2-) ligand exhibits a unique μ(3)-η(2),η(2),η(2)-coordination mode; 3 is polymeric comprising of [Li(4)(S(3)P(n)Pr)(2)(TMEDA)(2)] dimers linked via additional bridging bis(monodentate) TMEDA molecules; 4 and 5 both adopt dimeric motifs with μ(2)-η(2),η(2) coordination of the magnesium centers.

Design and synthesis of a bombesin peptide-conjugated tripodal phosphino dithioether ligand topology for the stabilization of the fac-[M(CO)3]+ core (M=(99 m)Tc or Re)

A new tumor-seeking tridentate topology consisting of a phosphino dithioether ((HOCH(2))(2)PCH(2)CH(2)S(CH(2))(n)CH(2)SR; PS(2)) ligand framework for the production of kinetically inert and in vivo stable facial [(99m)Tc(CO)(3)(PS(2))](+) or [Re(CO)(3)(PS(2))](+) is described. The X-ray crystal structure of fac-Re(CO)(3)(PS(2))PF(6) is reported. The bioconjugation strategies for incorporating bombesin (BBN) peptides on to the PS(2) tripodal framework and, thereby, de novo designing of GRP receptor-seeking Tc(PS(2)-BBN)(CO)(3) are developed.

Facile and General Method for Synthesis of Sugar Coated Gold Nanoparticles

This letter describes a general method for the preparation of carbohydrate coated gold nanoparticles. The generality of this method has been demonstrated by surface coating AuNPs with the following sugars: glucose (monosaccharide); sucrose, maltose, or lactose (disaccharides); raffinose (trisaccharide); and starch (polysaccharide). The non-toxic, water-soluble phosphino aminoacid P(CH(2)NHCH(CH(3)-)COOH)(3), THPAL, has been used as a reducing agent in this process. The sizes of sugar coated AuNPs that have been generated in this study are: 30 ± 8 nm (Glucose), 10 ± 6 nm (sucrose), 8 ± 2 nm (maltose), 3 ± 1 nm (lactose), 6 ± 2 nm (raffinose), and 39 ± 9 nm (starch).

Gum arabic as a phytochemical construct for the stabilization of gold nanoparticles: in vivo pharmacokinetics and X-ray-contrast-imaging studies

Gold nanoparticles (AuNPs) have exceptional stability against oxidation and therefore will play a significant role in the advancement of clinically useful diagnostic and therapeutic nanomedicines. Despite the huge potential for a new generation of AuNP-based nanomedicinal products, nontoxic AuNP constructs and formulations that can be readily administered site-specifically through the intravenous mode, for diagnostic imaging by computed tomography (CT) or for therapy via various modalities, are still rare. Herein, we report results encompassing: 1) the synthesis and stabilization of AuNPs within the nontoxic phytochemical gum-arabic matrix (GA-AuNPs); 2) detailed in vitro analysis and in vivo pharmacokinetics studies of GA-AuNPs in pigs to gain insight into the organ-specific localization of this new generation of AuNP vector, and 3) X-ray CT contrast measurements of GA-AuNP vectors for potential utility in molecular imaging. Our results demonstrate that naturally occurring GA can be used as a nontoxic phytochemical construct in the production of readily administrable biocompatible AuNPs for diagnostic and therapeutic applications in nanomedicine.

Nanocompatible Chemistry toward Fabrication of Target-Specific Gold Nanoparticles

Nanocompatible chemistry which utilizes a novel nontoxic phosphino amino acid as a reducing agent has resulted in the development of therapeutically useful gold nanoparticles under biologically benign media. Stabilization of gold nanoparticles by the edible gum arabic matrix has provided an effective pathway toward in vivo stable target-specific gold nanoparticles.