Molecular Design of Tetraazamacrocyclic Derivatives Bearing a Spirobenzopyran and Three Carboxymethyl Moieties and Their Metal-Ion Complexing Behavior

Abstract

Tetraazacyclododecane and tetraazacyclotetradecane derivatives bearing a spirobenzopyran and three carboxymethyl moieties, 1 and 2, and a diethylenetriamine derivative bearing a spirobenzopyran and four carboxymethyl moieties 3 were synthesized. The isomerization behaviors based on the spirobenzopyran moiety of these ligands were studied by UVvisible spectrophotometry in aqueous solutions containing various metal ions at neutral pH. These ligands formed stable 1:1 complexes with lanthanide ions, while the spirobenzopyran moiety was isomerized to its corresponding merocyanine form even under dark conditions. In aqueous solutions containing a lanthanide ion, the absorption spectra of 1 or 2 showed remarkable blue shifts, while absorbances at the maximum absorption wavelengths in the visible region were enhanced; such changes are attributable to the isomerization to the merocyanine form of the spirobenzopyran moiety. These results suggest that the phenolate anion of the merocyanine moiety interacts very strongly with a lanthanide ion bound by the complexing moiety because of the high charge density of lanthanide ions. In contrast, the absorbance of merocyanine form was decreased by the complexation of the macrocyclic ligand with transition metal ions, such as Cu . This result indicates that macrocyclic ligands, 1 and 2, formed complexes with transition metal ions only by the aminocarboxylate moieties, and the phenolate ion of merocyanine moiety was not able to participate in the complexation. This conclusion was also demonstrated by density functional theory calculations.

Engineered Nonviral Protein Cages Modified for MR Imaging

“…Gd-C4-IA was synthesized as described in Figure , with characterization data for compounds 1 − 4 (Scheme S1) provided in Figures S1−S23. Literature conditions were followed to prepare tri- t Bu 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)­triacetate ( t BuDO3A) and benzyl acrylate. ,, Benzyl acrylate served as the foundation for the functional arm that was later used to covalently link Gd-C4-IA to the protein cages. t BuDO3A and benzyl acrylate were reacted via an aza-Michael addition.…”

In-depth Study of a Novel Class of Ditopic Gadolinium(III)-based MRI Probes Sensitive to Zwitterionic Neurotransmitters

“…The bromo fragment 2 was prepared in 4 steps, starting from cyclen. In the first step, cyclen was converted in DO3A tert -butyl ester in a one-step procedure (Machitani et al, 2008), followed by the subsequent N-alkylation with N -(3-bromopropyl)phtalimide and the mild deprotection of Phth with ethylenediamine (EDA) to afford the propyl amine derivative 1 . The amine 1 was coupled with bromoacetic acid in the presence of N, N '-dicyclohexylcarbodiimide (DCC) to furnish bromide 2 .…”

Ultrasmall Superparamagnetic Iron Oxide Nanoparticles with Europium(III) DO3A as a Bimodal Imaging Probe

“…The final design is depicted in Scheme and a thin layer of silane was used to couple the europium(III) complex to the IO nanoparticles. The europium(III) ion itself is toxic for the human body, but encapsulation in a macrocyclic DO3A structure has been used to firmly encapsulate the lanthanide ions in the cavity of the organic structure and the resulting complex is a convenient scaffold for further functionalization …”

“…The europium(III) ion itself is toxic for the human body,b ut encapsulation in am acrocyclic DO3A structure has been used to firmly encapsulate the lanthanide ions in the cavity of the organic structure and the resulting complex is ac onvenient scaffold forf urther functionalization. [23] In Scheme 2t he synthetic strategy to yield the Fe 3 O 4 -DO3A-Eu material 5 is presented. Starting with the synthesis of 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid 1 based on ar eported procedure, [24] standard nucleophilic substitution reaction generated 10-(3-buten-1-yl)-1,4,7-tris(1,1-dimethylethyl) ester 2 (DO3A-ene).…”