Facile Access to the 12‐Membered Macrocyclic Ligand PCTA and Its Derivatives with Carboxylate, Amide, and Phosphinate Ligating Functionalities. Issue 15 (18th April 2018)

• Record Type: Journal Article
• Authors: Enel, Morgane; Leygue, Nadine; Saffon, Nathalie; Galaup, Chantal; Picard, Claude
• Is Part Of: European journal of organic chemistry. Issue 15(2018)
• Page Start: 1765
• Page End: 1773
• Publication Date: 2018-04-18
• Subjects: Lanthanides -- Luminescence -- Macrocyclic ligands -- Magnetic properties -- Template synthesis; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201800066
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract : We describe a convenient synthetic pathway to access the 12‐membered PCTA macrocycle, a polyaminocarboxylate ligand for which its M 2+ and M 3+ complexes are commonly associated with applications in biomedical diagnostics and radiotherapy. The synthetic pathway is based on the use of a linear tri‐ N ‐alkylated triamine synthon incorporating masked acetate arms and an efficient sodium template ion effect for the crucial macrocyclization step (87 % macrocyclization yield). This approach was then successfully applied to access three new PCTA[12] derivatives containing either a 4‐pyridol unit, an amide or a phosphinate coordinating function in the central arm. In all cases, the macrocyclization reactions were controlled by a sodium template ion effect, and the macrocyclization yields were in the range of 60 to 75 %. The luminescence and relaxometric properties of Eu III, Tb III, and Gd III complexes derived from PCTA derivatives with mixed coordinating arms were also investigated, making these complexes possible alternatives to PCTA[12]–Ln III complexes. Abstract : A convenient and efficient alternative to the classical Richman–Atkins methodology for obtaining PCTA and new derivatives is reported. The key macrocyclization step occurs in good yields as a result of a sodium template effect. The potentiality of lanthanide(III) complexes derived from these new PCTA ligands to act as paramagnetic contrastophores or luminophores is reported.