A new metallostar complex based on an aluminum(iii) 8-hydroxyquinoline core as a potential bimodal contrast agent?

Dalton Transactions Pub Date: 2012-07-25 DOI: 10.1039/C2DT30605K

Abstract

A ditopic DTPA monoamide derivative containing an 8-hydroxyquinoline moiety was synthesized and the corresponding gadolinium(III) complex ([Gd(H5)(H2O)]?) was prepared. After adding aluminum(III), the 8-hydroxyquinoline part self-assembled into a heteropolymetallic triscomplex [(Gd5)3Al(H2O)3]3?. The magnetic and optical properties of this metallostar compound were investigated in order to classify it as a potential in vitro bimodal contrast agent. The proton nuclear magnetic relaxation dispersion measurements indicated that the relaxivity r1 of [Gd(H5)(H2O)]? and [(Gd5)3Al(H2O)3]3? at 20 MHz and 310 K equaled 6.17 s?1 mM?1 and 10.9 s?1 mM?1 per Gd(III) ion respectively. This corresponds to a relaxivity value of 32.7 s?1 mM?1 for the supramolecular complex containing three Gd(III) ions. The high relaxivity value is prominently caused by an increase of the rotational tumbling time τR by a factor of 2.7 and 5.5 respectively, in comparison with the commercially used MRI contrast agent Gd(III)–DTPA (Magnevist?). Furthermore, upon UV irradiation, [(Gd5)3Al(H2O)3]3? exposes green broad-band emission with a maximum at 543 nm. Regarding the high relaxivity and the photophysical properties of the [(Gd5)3Al(H2O)3]3? metallostar compound, it can be considered as a lead compound for in vitro bimodal applications.

Graphical abstract: A new metallostar complex based on an aluminum(iii) 8-hydroxyquinoline core as a potential bimodal contrast agent
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