Highly stable and soluble bis-aqua Gd, Nd, Yb complexes as potential bimodal MRI/NIR imaging agents.

A tripodal ligand based on the 8-hydroxyquinolinate binding unit yields a soluble and highly stable bis-hydrated Gd(3+) complex in water (pGd = 19.2(3)) with relaxivity change in the pH range 4.5-7.4 and Nd(3+), Yb(3+) analogues with sizeable NIR emission upon excitation at 370 nm providing a new architecture for the development of bimodal agents.