The kinetic and structural consequences of dimerisation as one of the main chemical follow-up reactions in electron transfer in organic molecules is very often not understood. As electrochemical methods result in an indirect description of dimerisation processes following electron transfer steps, spectroelectrochemical methods are needed for direct evidence of dimerisation. The triple in situ experimental technique for the simultaneous measurement of ESR and UV-vis-NIR spectra in electrochemical experiments at different temperatures, including a special TE102 optical ESR cavity and Bruker temperature control system, is presented in its application to redox reactions of dimeric structures and dimerisation reactions following an electron transfer. As redox systems, Wurster's reagent and thianthrene are used for reference work. The triple spectroelectrochemical method is successfully applied to extended organic pi -conjugated systems like end-capped quarter-thiophene and dimeric fullerene C-120 where the dimeric structures have been characterised in detail.