This thesis focuses on the bottom-up design, construction and operation of supramolecular systems capable of behaving as devices and machines on the molecular scale, which is a topic of great interest in nanoscience and a fascinating challenge in nanotechnology. In particular, the systems investigated here include: polyviologen dendrimers capable of behaving as hosts and chargestoring devices; molecular machines based on pseudorotaxanes/rotaxanes and operated by photoinduced proton transfer, or photoisomerization reactions; and a simple unimolecular multiplexer/demultiplexer. The systems have been characterized using a variety of techniques including absorption and emission spectra, laser flash photolysis, NMR spectroscopy, electrochemical experiments, stopped flow measurements. This research addresses a large number of open problems in the nanosciences, dealing with a wide range of the most advanced applications of supramolecular systems.