The two coordination compounds of cobalt were designed and synthesized. The substrates were carefully selected to allow gentle tuning of the molecular structure of the designed compounds. The crystal, molecular and supramolecular structure of studied compounds has been determined and discussed. The spectroscopic and thermal properties of designed coordination compounds have been studied and their application as precursors for the synthesis of cobalt oxide nanoparticles has been demonstrated. It was proven that not only are parameters of conversion of the precursor to nanoparticles important, but also small changes in molecular structure can considerably affect the size of formed particles. For unambiguous determination of the influence of compounds structure on their UV-Vis radiation absorption, density functional theory and time-dependent density functions theory calculations have been performed. The complexity of the correct ab-initio reflection of the open shell molecular system was outlined and discussed. The results obtained from density functional theory (DFT) calculations have been also employed for discussion of the bonding properties.