The effect of metal salt treatment on the photoluminescence of DFO-treatedfingerprints

Ninhydrin developed fingerprints can be enhanced by treatment with a zinc o r cadmium salt. The resulting fingerprint luminescence has been attributed to the induced coplanarity of the bicyclic indanedione rings of Ruhemann's purple due to complexation with the metal ions. This paper explores whether this effect also occurs in the 1,8-diaza-9-fluorenone (DFO)-amino acid add uct (1), formed from the reaction of DFO with amino acids. Molecular modeli ng studies of (1) indicate a relatively small out-of-plane angle of 24 degr ees. H-1 NMR studies indicate (1) is asymmetric about the C2 axis in contra st to what has been previously reported. Little, if any, enhancement of lum inescence was observed with Zn, Cd, Ru or Eu treated DFO developed latent f ingerprints. This lack of enhancement was also borne out by solution lumine scence studies. Given this lack of enhancement of luminescence, solutions o f (I) and the four metal ions above were analyzed by electrospray mass spec trometry (ESMS). This indicated the formation of predominantly 1:1 complexe s of (1) with both Zn and Cd, and the 2:1 complex with ruthenium. No eviden ce of a Eu complex was found by ESMS. (C) 2001 Elsevier Science Ireland Ltd . All rights reserved.