Contents 1. Introduction 6009 2. Organic Groups Covalently Linked to Polyoxometalate Units via p-Block Elements 6011 2.1. Presentation and Generalities on the Functionalization of POMs 6011 2.1.1. Importance of the Anchorage Point 6011 2.1.2. Nature, Degree, and Localization of the Functionalization 6011 2.1.3. Influence of the Nature of the POM 6012 2.

Water-dispersible gold nanoparticles functionalized with paramagnetic gadolinium have been fully characterized, and the NMRD profiles show very high relaxivities up to 1.5 T. Characterization using TEM images and dynamic light scattering indicate a particle size distribution from 2 to 15 nm. The gold cores of the nanoparticles do not contribute significantly to the overall magnetic moment.