Photochemical Reactions of Aminonaphthols Caused by Laser Desorption/Ionization

Abstract

e formation of monomeric and dimeric ions of seven di erent aminonaphthols (ANLs) has been studied by using laser desorption/ionization (LDI) with a nitrogen laser. e positive-ion data of all the ANLs merely showed molecular ion M · + without protonated molecule [M+H] + , while 1-amino-2-naphthol (1,2-ANL) and 2-amino-1-naphthol (2,1-ANL) showed an intense dimeric ion [2 M−2H 2 O+H] + . e negativeion data showed deprotonated molecule [M−H] − in common, while the spectra of 1,2-ANL, 2,1-ANL and 8-amino-2-naphthol (8,2-ANL) accompanied an intense peak corresponding to negative molecular ion M · − and the 8,2-ANL and 4-amino-1-naphthol (4,1-ANL) accompanied dehydrogenated anion [M−2H] · − . e formation of monomeric ions was discussed from the standpoints of thermochemical properties such as ionization energy, gas-phase acidity, electron a nity, and bond dissociation energy. e formation of dimeric ions [2 M−2H 2 O+H] + observed in the 1,2-ANL and 2,1-ANL could be explained by the radical combination in the amino groups. An isomer 5-amino-1-naphthol (1-ANL) did not give any dimeric ions in the both positive-and negative-ion spectra. e in uence of laser uence upon the appearance of the monomeric ions such as M