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Mechanistic insight into the fluorescence activity of forensic fingerprinting reagents

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journal contribution
posted on 08.04.2021, 13:39 authored by Lily Hunnisett, Paul F. Kelly, S Bleay, Felix PlasserFelix Plasser, R King, B McMurchie, Pooja GoddardPooja Goddard
Fingerprint detection is still the primary investigative technique for deciphering criminal inquiries and identifying individuals. The main forensic fingerprinting reagents (FFRs) currently in use can require multiple treatment steps to produce fingerprints of sufficient quality. Therefore, the development of new, more effective FFRs that require minimal chemical treatment is of great interest in forensic chemistry. In this work, prudently crafted density functional theory and time-dependent density functional theory calculations are utilized to derive mechanistic insight into the optical activity of the non-fluorescent product of ninhydrin, diketohydrindylidenediketohydrindamine (DYDA), and fluorescent product of DFO (1,8-diazafluoren-9-one). We investigate various protonation sites to gain an understanding of isomeric preference in the solid-state material. A relaxed scan of a single torsion angle rotation in the S1 minimized geometry of the O-protonated DYDA isomer suggests a conical intersection upon ∼10○ rotation. We show that the absence of a rigid hydrogen-bonded network in the crystal structure of DYDA supports the hypothesis of torsion rotation, which leads de-excitation to occur readily. Conversely, for the fluorescent DFO product, our calculations support an avoided crossing suggestive of a non-radiative mechanism when the torsion angle is rotated by about ∼100○ . This mechanistic insight concurs with experimental observations of fluorescence activity in DFO and may aid the photophysical understanding of poorly visualized fingerprints due to weak fluorescence. We show that identifying suggestive avoided crossings via the method described here can be used to initialize thoughts toward the computational design of FFRs.

History

School

  • Science

Department

  • Chemistry

Published in

The Journal of Chemical Physics

Volume

154

Issue

12

Publisher

AIP Publishing

Version

VoR (Version of Record)

Rights holder

© The Authors

Publisher statement

This is an Open Access Article. It is published by AIP Publishing under the Creative Commons Attribution 4.0 International Licence (CC BY 4.0). Full details of this licence are available at: https://creativecommons.org/licenses/by/4.0/

Acceptance date

07/03/2021

Publication date

2021-03-31

Copyright date

2021

ISSN

0021-9606

eISSN

1089-7690

Language

en

Depositor

Dr Pooja Goddard. Deposit date: 1 April 2021

Article number

124313