Development of Highly Sensitive Hydrazones Forming Metal Complexes with Molar Absorptivities of the Order of 10^5

点击翻译按钮获取中文摘要

I found that the introduction of an electron-withdrawing nitro group at the 5-position of the pyridine ring in the hydrazine moiety of 2-pyridylhydrazone which has long conjugated double bonds in its molecule is very effective for increasing the molar absorptivity of its metal complexes. On the basis of this finding, 1 have succeeded, for the first time, in synthesizing hydrazone ligands which form metal complexes with molar absorptivities of the order of 10^5. The synthesized hydrazones are insoluble in water but soluble in organic solvents such as ethanol, dioxane, benzene, chloroform, etc. Every hydrazone reacts with Cu(II), Fe(II), Hg(II), Ni(II), Pd(II), Zn(II),etc.to form colored complexed extractable into organic solvents. Molar absorptivities of complexed of 5- and 3,5-PANPH, QANPH and PhANPH were almost same values (10^5) and about twice twice those of 3-PANPH complexes.These results indicate that (1) introduction of a electron-withdrawing nitro group at the 5-position of the hydrazine moiety of PAPH and its analogues is very effective for increasing molar absorptivities of their metal complexes,i.e., developing highly sensitive hydrazone reagents, (2) the introduction of a nitro group at the 3-position is ineffective for this purpose but effective for increasing the soludility of PANPH, 5-PANPH and their analogues in organic solvents and (3) the substitution of the pyridine ring of the aldehyde moiety of PAPH and its derivatives by a phenanthridine ring is also effective for developing hiphly sensitive hydrazone reagents. The reason why 2-(5-nitro and/or 3,5-dinitro)phridylhydrazone form metal complexes with extremely high molar absorptivities may be explained by the concept of the so called "charged quinone structure".