Here, the properties of three highly water soluble Ru(ii) and Zn(ii) polypyridyl complexes as photosensitizers (PSs) were examined, including the one-photon and two-photon absorption (OPA and TPA) spectra, singlet-triplet energy gap (ΔH-L), TPA cross-section and spin-orbit coupling constant via Density Function Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT).