Synthesis and structural characterization of complexes of a DO3A-conjugated triphenylphosphonium cation with diagnostically important metal ions.
To understand the coordination chemistry of a DO3A-conjugated triphenylphosphonium (TPP) cation, triphenyl(4-((4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl)methyl)benzyl)phosphonium (DO3A-xy-TPP), with diagnostically important metal ions, In(DO3A-xy-TPP)+, Ga(DO3A-xy-TPP)+, and Mn(DO3A-xy-TPP) were prepared by reacting DO3A-xy-TPP with 1 equiv of the respective metal salt. All three complexes have been characterized by elemental analysis, IR, ESI-MS, NMR methods (for In(DO3A-xy-TPP)+ and Ga(DO3A-xy-TPP)+), and X-ray crystallography. Results from HPLC concordance experiments show that (111)In(DO3A-xy-TPP)+ and In(DO3A-xy-TPP)+ have the same composition. The solid-state structures of In(DO3A-xy-TPP)+ and Mn(DO3A-xy-TPP) are very similar with DO3A being heptadentate in bonding to In(III) and Mn(II) in a monocapped octahedral coordination geometry. Because of the smaller size of Ga(III), the DO3A in Ga(DO3A-xy-TPP)+ is only hexadentate with four amine-N and two carboxylate-O atoms bonding to Ga(III). One carboxylic acid group in DO3A is deprotonated to balance the positive charge of Ga(III). The coordination geometry of Ga(DO3A-xy-TPP)+ is best described as a distorted octahedron. The NMR data shows that the coordinated DO3A in In(DO3A-xy-TPP)+ and Ga(DO3A-xy-TPP)+ is symmetrical in aqueous solution. There is no dissociation of the acetate chelating arms in In(DO3A-xy-TPP)+ and Ga(DO3A-xy-TPP)+, providing indirect evidence for the high solution stability of (111)In(DO3A-xy-TPP)+ and (68)Ga(DO3A-xy-TPP)+.
Yang
Chang-Tong
CT
School of Health Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
Li
Yongxin
Y
Liu
Shuang
S
D000085:Acetates / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry; D002412:Cations; D002621:Chemistry / Q000379:methods*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D018360:Crystallography, X-Ray / Q000379:methods; D007477:Ions; D009682:Magnetic Resonance Spectroscopy; D008670:Metals / Q000737:chemistry*; D008968:Molecular Conformation; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000737:chemistry*; D012492:Salts / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013055:Spectrophotometry, Infrared / Q000379:methods