Monopicolinate-dipicolyl Derivative of Triazacyclononane for Stable Complexation of Cu²⁺and⁶⁴Cu²⁺

Abstract

The synthesis and characterization of Hno1pa2py, a new tacn-based ligand, is reported. The complexation process with Cu(2+) was proved to be very fast even in acidic medium. Potentiometric titrations allowed us to establish that Hno1pa2py exhibits an overall low basicity as well as a high selectivity for Cu(2+) over Zn(2+) cations. The copper(II) complex was synthesized and characterized using UV-vis and EPR spectroscopies and density functional theory (DFT) calculations. The studies clearly showed that the [Cu(no1pa2py)](+) complex is present in solution as a mixture of two isomers in which the ligand is coordinated to the metal center using a N5O donor set with the metal center in a distorted octahedral geometry. The very high kinetic inertness of the [Cu(no1pa2py)](+) complex was demonstrated by using acid-assisted dissociation assays as well as cyclic voltammetry. Preliminary investigations of (64)Cu complexation were performed to validate the potential use of such chelating agent for further application in nuclear medicine. The X-ray crystal structures of copper(II) complexes of L1, the ester derivative of Hno1pa2py, have been determined.

Lanthanide Complexes with Heteroditopic Ligands as Fluorescent Zinc Sensors

“…Compounds 4 and 5 have been obtained following our previously described procedures. [22,24] tert-Butyl 2,2Ј,2ЈЈ-(10-{[6-(Chloromethyl)pyridin-2-yl]methyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate (3): A solution of DO3AtBu 1 (1.00 g, 1.94 mmol) in distilled acetonitrile (120 mL) was added dropwise over 1 h to a stirred solution of 2 (1.70 g, 9.70 mmol, 5.0 equiv.) and potassium carbonate (1.30 g, 9.70 mmol, 5.0 equiv.)…”

“…Among the different pendant arms incorporated with TACN for this purpose are acetic acid, [19] methylenephosphinic [20] and picolyl [21,22] groups. In an attempt towards Ln 3+ -based responsive agents with potential application as luminescence and/or MRI probes, herein we report the heteroditopic ligands H 3 L1 and H 3 L2 (Scheme 1), which contain a DO3A unit for stable coordination of the Ln 3+ ions linked to a TACN moiety through a 2,6-dimethylpyridine unit.…”

“…[23] The synthesis of the ligands was achieved following our previously described strategies. [22,24] Ligands H 3 L1 and H 3 L2 were synthesized starting from precursor DO3AtBu (1). Condensation of the latter with an excess amount of 2,6-bis(chloromethyl)pyridine (2) in the presence of K 2 CO 3 led, after workup with column chromatography on alumina, to the functionalized DO3AtBu derivative 3 with 33 % yield.…”

“…[ 22] In the next step, the removal of the aminal bridge of the TACN moiety as well as the ester protection were performed in hydrochloric acid, which led to the deprotected compound H 3 L1 as the hydrochloride salt. Following an analogous synthetic route, compound 7 was obtained in 34 % yield from the condensation of 3 with di-N-functionalised TACN 5 followed by chromatographic purification.…”

Investigating the Complexation of the Pb2+/Bi3+ Pair with Dipicolinate Cyclen Ligands

“…The setup for potentiometric titrations has been described before. 64 The titrant was a carbonate-free KOH solution at ca. 0.50 M prepared from a commercial ampule of analytical grade, and the exact concentration was obtained by application of Gran's method 65 67 The terms E 0 and Q were determined by titration of a solution of known hydrogen-ion concentration at the same ionic strength.…”