Distance measurements by pulsed electron paramagnetic resonance techniques (DEER, PELDOR) have become very useful tools to elucidate the structure of (bio)macromolecules and their assemblies in a disordered, native state. For this purpose the molecules of interest are twofold site-selectively spin labeled with radicals. Usually nitroxyl radicals are used. A significant advancement of DEER in terms of sensitivity, measurement time, measurable distance range, precision, and data evaluation is expected from the recent development of high field EPR spectrometers. To gain full advantage of the high field other labels than nitroxyl radicals are needed. A very promising candidate is gadolinium in the oxidation state 3. To sound its potential tailor-made compounds are needed. The development and preparation of such model compounds of the type Gd3+-spacer-Gd3+ and Gd3+-spacer-(nitroxyl radical) is a primary goal of this project. The distance between the unpaired electron of the label and their geometrical arrangement will be well-defined and will be deliberately varied. With substituting Gd3+ by Dy3+ in Gd3+-spacer-(nitroxyl radical) the demand for model compounds to explore relaxation enhancement of nitroxyl radicals as a complementary EPR tool for distance measurement will be addressed. Moreover the syntheses of the model compounds will provide a construction kit and an instruction which will be of general use to assemble compounds which will support the further exploration and development of EPR techniques.