Eight new hydrazones derived from 2-pyridinecarbaldehyde 5-nitro-2-pyridylhydrazone (PA-5-NPH) were synthesized. Their properties, reactivities with metal ions and extractabilities of the complexes have been investigated and compared. It has been found that (1) the introduction of a nitro group to the 3-, 4- and/or 5-position of the pyridine ring in the aldehyde moiety of PA-5-NPH lowers the pKa values and causes remarkable bathochromic shifts in the absorption spectra of the hydrazone and its metal complexes, (2) the introduction of a nitro group to the 5-position of the pyridine ring brings about increases in molar absorptivities of the metal complexes, whereas introduction to the 4-position causes them to decrease, and (3) the introduction of electron-releasing groups to the 4-position of the pyridine ring, on the contrary, brings about increases in molar absorptivities of the metal complexes. Furthermore, considering the results reported already, it is concluded that the introduction of a nitro group to the 5-position of the pyridine ring in both the hydrazine and aldehyde moiety of 2-pyridinecarbaldehyde 2-pyridylhydrazone (PAPH) is very effective for increasing the molar absorptivity of the metal complexes.