Effect of magnesium addition on the mechanical properties of metallic composite materials based on the eutectic Al-5.7% Ni alloy

The effect of Mg addns. on the mech. properties of dispersion hardening alloys, prepd. from the eutectic Al-5.7% Ni by casting and isostatic extrusion was detd. A small amt. of Mg increases significantly the tensile strength and fracture elongation, and esp. stabilizes the alloy structure for annealing at high tempinfo:eu-repo/semantics/publishe

Macromolecular ligands for gadolinium MRI contrast agents

Macromolecular ligands for gadolinium contrast agents (CAs) were prepared via a “grafting to” strategy. Copolymers of oligoethylene glycol methyl ether acrylate (OEGA) and an activated ester monomer, pentafluorophenyl acrylate (PFPA), were synthesized and modified with the 1-(5-amino-3-aza-2-oxypentyl)-4,7,10-tris(tert-butoxycarbonylmethyl)-1,4,7,10-tetraazacyclododecane (DO3A-tBu-NH2) chelate for the complexation of Gd3+. The relaxivity properties of the ligated Gd3+ agents were then studied to evaluate the effect of macromolecular architecture on their behavior as magnetic resonance imaging (MRI) CAs. Ligands made from linear and hyperbranched macromolecules showed a substantially increased relaxivity in comparison to existing commercial Gd3+ MRI contrast agents. In contrast, star nanogel polymers exhibited a slightly lower relaxivity per Gd3+ ion (but still substantially higher relaxivity than existing low molecular weight commercial CAs). This work shows that macromolecular ligands have the potential to serve as components of Gd MRI agents as there are enhanced effects on relaxivity, allowing for lower Gd concentrations to achieve contrast, while potentially imparting control over pharmacokinetics

Multimetallic complexes and functionalized gold nanoparticles based on a combination of d- and f-elements

The new DO3A-derived dithiocarbamate ligand, DO3A-tBu-CS2K, is formed by treatment of the ammonium salt [DO3A-tBu]HBr with K2CO3 and carbon disulfide. DO3A-tBu-CS2K reacts with the ruthenium complexes cis-[RuCl2(dppm)2] and [Ru(CH═CHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole) to yield [Ru(S2C-DO3A-tBu)(dppm)2]+ and [Ru(CH═CHC6H4Me-4)(S2C-DO3A-tBu)(CO)(PPh3)2], respectively. Similarly, the group 10 metal complexes [Pd(C,N-C6H4CH2NMe2)Cl]2 and [PtCl2(PPh3)2] form the dithiocarbamate compounds, [Pd(C,N-C6H4CH2NMe2)(S2C-DO3A-tBu)] and [Pt(S2C-DO3A-tBu)(PPh3)2]+, under the same conditions. The linear gold complexes [Au(S2C-DO3A-tBu)(PR3)] are formed by reaction of [AuCl(PR3)] (R = Ph, Cy) with DO3A-tBu-CS2K. However, on reaction with [AuCl(tht)] (tht = tetrahydrothiophene), the homoleptic digold complex [Au(S2C-DO3A-tBu)]2 is formed. Further homoleptic examples, [M(S2C-DO3A-tBu)2] (M = Ni, Cu) and [Co(S2C-DO3A-tBu)3], are formed from treatment of NiCl2·6H2O, Cu(OAc)2, or Co(OAc)2, respectively, with DO3A-tBu-CS2K. The molecular structure of [Ni(S2C-DO3A-tBu)2] was determined crystallographically. The tert-butyl ester protecting groups of [M(S2C-DO3A-tBu)2] (M = Ni, Cu) and [Co(S2C-DO3A-tBu)3] are cleaved by trifluoroacetic acid to afford the carboxylic acid products, [M(S2C-DO3A)2] (M = Ni, Cu) and [Co(S2C-DO3A)3]. Complexation with Gd(III) salts yields trimetallic [M(S2C-DO3A-Gd)2] (M = Ni, Cu) and tetrametallic [Co(S2C-DO3A-Gd)3], with r1 values of 11.5 (Co) and 11.0 (Cu) mM–1 s–1 per Gd center. DO3A-tBu-CS2K can also be used to prepare gold nanoparticles, Au@S2C-DO3A-tBu, by displacement of the surface units from citrate-stabilized nanoparticles. This material can be transformed into the carboxylic acid derivative Au@S2C-DO3A by treatment with trifluoroacetic acid. Complexation with Gd(OTf)3 or GdCl3 affords Au@S2C-DO3A-Gd with an r1 value of 4.7 mM–1 s–1 per chelate and 1500 mM–1 s–1 per object