Metal nanoclusters (MNCs) emerged a massive interest due to their size-tunable photochemical properties such as HOMO-LUMO transitions, size-dependent photoluminescence, chirality and magnetism. The size-dependent properties can be tuned in situ by applying well-established synthetic protocols and by engineering the surface protective ligand shell ex situ. In this thesis, the ligand exchange reactions were applied to post-synthetically modify the protective ligand shell of atomically precise Au25(2-PET)18 and Au38(2-PET)24 clusters by choosing thiolated crown ether and helical ligands, respectively. The chiroptical properties of the clusters were changed upon ligand incorporation, which indicated the successful ligand exchange reactions on the cluster surface. We developed new synthetic strategies for preparing copper clusters soluble in aqueous media and organic phase. The prepared clusters showed dose-dependent antimicrobial properties.