Abstract:
Ninhydrin developed fingerprints can be enhanced by treatment with a zinc or 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-f1uorenone (DFO)-
amino acid adduct (I), formed from the reaction of DFO with amino acids. Molecular modeling studies of (I) indicate a
relatively small out-of-plane angle of 24°. ¹H NMR studies indicate (I) is asymmetric about the C2 axis in contrast to what has
been previously reported. Little, if any, enhancement of luminescence was observed with Zn, Cd, Ru or Eu treated DFO
developed latent fingerprints. This lack of enhancement was also borne out by solution luminescence studies. Given this lack
of enhancement of luminescence, solutions of (I) and the four metal ions above were analyzed by electrospray mass
spectrometry (ESMS). This indicated the formation of predominantly I: I complexes of (I) with both Zn and Cd, and the 2: I
complex with ruthenium. No evidence of a Eu complex was found by ESMS.
