Abstract | 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. |
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