title: Iron(II) complexes containing octadentate tetraazamacrocycles as paraCEST magnetic resonance imaging contrast agents.
abstract: Iron(II) complexes of the macrocyclic ligands 1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane (TCMC) and (1S,4S,7S,10S)-1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane (STHP) contain a highly stabilized Fe(II) center in the high-spin state, which is encapsulated by an octadentate macrocycle. The complexes are resistant to acid, metal cations, phosphate, carbonate, and oxygen in aqueous solution. [Fe(TCMC)](2+) contains exchangeable amide protons, and [Fe(STHP)](2+) contains exchangeable protons attributed to alcohol OH donors, which give chemical exchange saturation transfer (CEST) peaks at physiological pH and 37 °C at 50 and 54 ppm from bulk water, respectively. The distinct pH dependence of the CEST peak of the two complexes over the range of pH 6-8 shows that these two groups may be useful in the development of ratiometric pH sensors based on iron(II).
authors: Department of Chemistry, State University of New York, University at Buffalo, Amherst, New York 14260, USA.
authors: Sarina J
authors: SJ
authors: Dorazio
authors: Janet R
authors: JR
authors: Morrow
mesh_terms: D001372:Aza Compounds / Q000737:chemistry*; D003287:Contrast Media / Q000138:chemical synthesis / Q000737:chemistry*; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D047028:Macrocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D008279:Magnetic Resonance Imaging; D008968:Molecular Conformation
chemical_list: D001372:Aza Compounds; D003287:Contrast Media; D005296:Ferrous Compounds; D047028:Macrocyclic Compounds