Relative binding strength of terpyridine model complexes under matrix-assisted laser desorption/ionization mass spectrometry conditions

The relative binding strength of a series of terpyridine metal complexes of the type [(ML2)-L-II](+) was investigated by using variable laser intensities in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). A model terpyridine ligand, 4'-(1,4,7-trioxa-octyl)-2,2':6',2-terpyridine, was prepared and complexed with a series of transition metal ions including cadmium, cobalt, copper, iron, manganese, nickel and ruthenium. The relative binding strength of these complexes can be obtained by measuring MALDI mass spectra of the prepared compounds at different laser intensities. The ratio of the signal intensities belonging to the ligand [LH](+) and the complex [ML2](+) ([LH](+)/[ML2](+)) depends on the laser intensity utilized for the spectrum acquisition. By considering an [LH](+)/[ML2](+) ratio > 10 as the point of complete complex dissociation, it is possible to establish a row of complex stabilities depending on the kind of metal ion. Copyright (C) 2003 John Wiley Sons, Ltd.