Synthesis and X-ray structural characterisation of seven co-ordinate macrocyclic In<sup>3+</sup>complexes with relevance to radiopharmaceutical applications

Riesen, Andreas; Kaden, Thomas A.; Ritter, Walter; Mäcke, Helmut R.

doi:10.1039/c39890000460

Cited by 74 publications

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“…These two peaks are almost superimposed, indicating that the carboxylates bind to In3+, with leads to an averaged chemical surrounding. This is fully consistent with the results obtained by X-ray diffraction studies, which show that, beside the four N-atoms, also the three COO-are coordinated to In" [22].…”

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confidence: 93%

Metal complexes with macrocyclic ligands. Part XXXVI. Thermodynamic and kinetic studies of bivalent and trivalent metal ions with 1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid

Cai

Kaden

1994

Helvetica Chimica Acta

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NMR, potentiometric, and UVjVIS measurements were run to study the protonation and the In3+ and Cu2+ stability constants of 1,4,7,1O-tetraazacyclododecane-1,4,7-triacetic acid (do3a, L). The protonation of do3a follows the typical scheme with two high and several low log KH values. Between pH 11 and 13, the protonation mainly occurs at the N-atom, which is not substituted by an acetate side chain. The In3+ complex is not appreciably protonated even at low pH values (pH -1.7), whereas [CuL] can add up to three protons in acidic solution to give the species [CuLH], [CuLH2], and [CuLH,], the stability of which was determined. The formation rates of the Y3+, Gd3+, Ga3+, and In3+ complexes with do3a were measured using a pH-stat technique, whereas that of Cu2+, being faster, was followed on a stopped-flow spectrophotometer. In all cases, the reaction scheme implies the rapid formation of partially protonated intermediates, which rearrange themselves to the final product in the rate-determining process. Introduction. -The field of macrocyclic complexes has gone through a rapid expansion in different directions. One of these has been the functionalization, achieved by the introduction of side chains carrying a donor group, which can act as an additional ligand for the metal ion. These compounds show interesting properties with respect to their complexation ability, selectivity, coordination geometry, and have potential applications [2]. Some of them are among the strongest chelators known, thus making them useful for medical applications, for which kinetical inertness and thermodynamical stability are of paramount importance. So, applications of macrocyclic metal complexes as contrast agents in magnetic resonance imaging (MRI) [3] and for labelling monoclonal antibodies have been described [4].The Gd3+ complexes of dota ( = 1,4,7,10-tetraazdcyclododecane-1,4,7,10-tetraacetic acid) and of dtpa (diethylenetriaminepentaacetic acid) are two of the MRI contrast agents already in use [5]. To obtain new, stable, and nonionic Gd"' chelates, Tweed2 and

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confidence: 93%

Metal complexes with macrocyclic ligands. Part XXXVI. Thermodynamic and kinetic studies of bivalent and trivalent metal ions with 1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid

Cai

Kaden

1994

Helvetica Chimica Acta

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“…It is important to note that the most common coordination number for In(III) is 6 and/or 7 while the coordination number of Ga(III) is predominantly 6 due to its smaller ionic radius. 34,35,38,39,48 Therefore, it is reasonable to believe that the solution structure of Ga(DOTA-xy-TPP) + is the same as that in the solid state ( Figure 5) with one acetate chelating arm being uncoordinated.…”

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confidence: 96%

Synthesis and Structural Characterization of Complexes of a DO3A-Conjugated Triphenylphosphonium Cation with Diagnostically Important Metal Ions

Yang

Liu

2007

Inorg. Chem.

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“…5 12-(pNitrobenzy1)-1,4,7,1O-tetraazacyclotridecane-1,4,7-triacetic acid (L2) was obtained by statistical alkylation of 4 with 3.5 equiv bromoacetic acid at pH 9.5, 70 "C (3 h), and purification as above (yield 45%). Mass (18,14).…”

Section: Methodsmentioning

confidence: 99%

Synthesis and evaluation of two new bifunctional carboxymethylated tetraazamacrocyclic chelating agents for protein labeling with indium-111

Ruser¹,

Ritter²,

Maecke³

1990

Bioconjugate Chem.

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The synthesis of two new N- and C-functionalized tetraazamacrocyclic ligands intended to be covalently linked to biomolecules like monoclonal antibodies and to bind the gamma-emitting isotope indium-111 in a thermodynamically and/or kinetically inert way is described. 12-(p-Nitrobenzyl)-1,4,7,10-tetraazacyclotridecane-1,4,7,10-tetraa cetic acid (L1) was synthesized by means of bimolecular cyclization with the appropriate malonic acid diethyl ester and triethylenetetraamine, followed by reduction with diborane and alkylation of the cyclic tetraamine with bromoacetic acid. The corresponding triscarboxymethylated ligand L2 was made by statistical alkylation of the tetraamine. Both ligands fulfill the criteria for antibody labeling using the bifunctional chelate approach, namely fast chelate formation, high radiochemical yield, and high stability under physiological conditions. Surprisingly the heptadentate ligand L2 confers higher stability to In3+ and exhibits faster complex formation than octadentate L1. 13C NMR spectra in solution indicate that the difference in stability is not due to incomplete coordination of all four carboxylate groups in In-L1.

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Synthesis and X-ray structural characterisation of seven co-ordinate macrocyclic In³⁺complexes with relevance to radiopharmaceutical applications

Cited by 74 publications

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Metal complexes with macrocyclic ligands. Part XXXVI. Thermodynamic and kinetic studies of bivalent and trivalent metal ions with 1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid

Metal complexes with macrocyclic ligands. Part XXXVI. Thermodynamic and kinetic studies of bivalent and trivalent metal ions with 1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid

Synthesis and Structural Characterization of Complexes of a DO3A-Conjugated Triphenylphosphonium Cation with Diagnostically Important Metal Ions

Synthesis and evaluation of two new bifunctional carboxymethylated tetraazamacrocyclic chelating agents for protein labeling with indium-111

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Synthesis and X-ray structural characterisation of seven co-ordinate macrocyclic In3+complexes with relevance to radiopharmaceutical applications

Cited by 74 publications

References 0 publications

Metal complexes with macrocyclic ligands. Part XXXVI. Thermodynamic and kinetic studies of bivalent and trivalent metal ions with 1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid

Metal complexes with macrocyclic ligands. Part XXXVI. Thermodynamic and kinetic studies of bivalent and trivalent metal ions with 1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid

Synthesis and Structural Characterization of Complexes of a DO3A-Conjugated Triphenylphosphonium Cation with Diagnostically Important Metal Ions

Synthesis and evaluation of two new bifunctional carboxymethylated tetraazamacrocyclic chelating agents for protein labeling with indium-111

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Synthesis and X-ray structural characterisation of seven co-ordinate macrocyclic In³⁺complexes with relevance to radiopharmaceutical applications