In the present thesis we develop new strategies concerning the use of lanthanide cations as spectroscopic probes for the study of molecular structures in solution. A widespread interest for lanthanides is mainly centered in two large fields: organic synthesis and clinical practice. Systems containing lanthanides enjoy a very favorable situation, since these ions feature high coordination numbers, which assure rich binding chemistry, and at the same time they possess the right spectroscopic properties to monitor it. The present thesis develops the potentialities of electronic spectroscopy of lanthanide systems in solution. We point out and overcome the drawbacks which have mainly hampered this kind of study so far, namely: a sensivity problem, an instrumental problem and a calibration problem.