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What Quantum Chemistry Can Do for Forensic Science

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Title: What Quantum Chemistry Can Do for Forensic Science


1
What Quantum Chemistry Can Do for Forensic Science
Amino Acid Alanine Reactivity with the
Fingerprint Reagent Ninhydrin.
H?E?
  • Danielle Sapse and Nicholas D. K. Petraco
  • John Jay College of Criminal Justice
  • City University of New York

2
Outline
  • How a Quantum Chemist can Help Forensic Science
  • History and Trivia on Fingerprints
  • Ninhydrin Alanine Gives Ruhemanns Purple
  • Results
  • Future Applications for Forensic Science
  • More fingerprints
  • Explosives detection
  • Probes for illegal drugs

3
Forensic Science Quantum Chemistry A Potential
Synergy
  • Opportunity to improve communication between
    theorists and (bio) analytical chemists and
    biologists
  • Computer speed always improving and big molecular
    systems can be treated
  • Theory can't replace the lab but can help!

4
What Can We Learn From Y?
  • Energy and Structures of Molecules
  • Molecular orbitals and relative energetics to
    help understand reactivity
  • Structures help us understand reactivity and
    design useful molecules such as materials, drugs
    and probes
  • Electronic Spectra
  • Vibrational, Rotational Spectra
  • NMR and ESR Spectra
  • Thermodynamic data from Statistical-Mechanics

5
A Forensic Science Classic Fingerprints!
  • Palm prints used for human identification in
    courts perhaps as early as 1st century Roman
    Empire
  • 7th century China, was perhaps the first
    documented use of fingerprints as means of
    identification.
  • It was probably Faulds (1880) who first proposed
    exploiting fingerprints for criminalistics in
    modern times.
  • As a means of identification, fingerprints are
    still par excellence.1

6
Fingerprint Amplification
  • Latent prints, only trace amounts of biomaterial
  • Very hard or impossible to see by themselves.
  • Solution Use some kind of developing agent.

7
Fingerprint Amplification
  • Fingerprint fluorescence is faint
  • Treat fingerprint with materials to obtain
    fluorescent or phosphorescent compounds

Menzel et al.
Before
8
Ninhydrin-Ruhemanns Purple System
  • Ninhydrin first suggested to develop latent
    fingerprints in 1950s.
  • Ninhydrin reacts with amino acids in fingerprints
    to produce Ruhemann's purple
  • Brightly colored and easy to identify by eye
  • Fluoresces slightly at the 582 nm and 407 nm when
    treated with a zinc or cadmium salts
  • Starting material, ninhydrin, is cheap

9
Motivation
  • Synthesize new compounds with properties superior
    to Ruhemann's purple.
  • No known chemical system which offers significant
    advantages in color to Ruhemanns purple.
  • Ultimately we want to help improve chromogenic
    and fluorogenic properties
  • An unequivocal understanding of the mechanism of
    formation for Ruhemanns purple is important!
  • The mechanism for the reaction between
    amino-acids and ninhydrin was never fully
    settled.
  • McCaldin Mechanism
  • Lamothe Mechanism
  • Friedman Mechanism
  • We have attempted to understand these mechanisms
    using ab-inito computations.

10
Computational Methods
  • Structures of all molecules in McCaldin, Lamothe
    and Friedman mechanisms optimized at RHF-SCF
    level using a 6-31G basis set and analytic
    derivative methods.
  • Gradients optimized to gt 0.0001 a.u.
  • Largest Abelian point groups used
  • Harmonic vibrational frequencies computed for all
    structures using finite difference of analytic
    gradients.
  • All computed structures found to be energetic
    minima
  • Benchmark structures for ninhydrin, alanine and
    Ruhemanns Purple were found using DFT B3LYP and
    a 6-31G.

11
DFT Benchmark Structures
Structure (Abelian point group) DFT 6-31G B3LYP Energy (hartree)
Ninhydrin (C2) -647.460616
Alanine (C1) -323.747976
Ruhemanns Purple isomer 1 (C1) -1046.957475
Ruhemanns Purple
ninhydrin
12
General Scheme for the Reaction of Ninhydrin with
a-amino acids to form Ruhemanns Purple
13
McCaldin Mechanism DE kcal/mol
a ninhydrin alanine ? 1 H2O 7.08
b 1 ? 2 H2O CO2 2.22
c 2 2 H ? 4 -4.35
d 2 H2O ? 3 acetald -9.55
e 4 H2O ? 3 acetald -5.20
f 3 H2O ? 6 NH3 3.50
g 3 H2O ? 7 NH3 -8.76
h 6 ? 7 -12.26
i 3 nin ? 5 H2O -8.42
j 7 nin 2 H ? 8 H2O 1.36
k 5 ? RP H2O H 28.94
14
Lamothe Mechanism DE kcal/mol
l 3 ninhydrin? 6 9 H2O 22.68
m 6 ninhydrin? 8 H2O -10.90
n 3 ninhydrin ? 5 H2O 8.62
o 6 9 ? RP H2O -2.16
p 5 ? RP H2O 11.90
15
Friedman Mechanism DE kcal/mol
r ninhydrin ? 10 H2O 17.95
s 10 alanine ? 1 -10.87
t 1 ? 11 H2O 9.21
u 11 ? 4 CO2 -11.34
v 4 ? 12 -8.19
w 12 H2O ? 3 acetald 2.99
q 3 ninhydrin ? RP 2 H2O 2 H 20.52
16
Our postulated mechanism at 25oC
17
New HF-6-31G Results on Substituted
Ninhydrin-Ruhemanns Purple Systems
Ruhemanns Purple Substitution DE kcal/mol
unsubs RP 17.52
RP-F (11) 17.12
RP-F (12) 17.55
RP-NH2 (13) 27.72
RP-NH2 (14) 19.66
RP-OCH3 (15) 22.34
RP-OCH3 (16) 28.27
RP-OH (17) 26.91
RP-OH (18) 19.94
Intermediate Structures DE kcal/mol
unsubs (19) 3.14
int.-F (20) -1.45
int.-F (21) 6.51
int.-NH2 (22) 6.50
int.-NH2 (23) 3.51
int.-OCH3 (24) 6.94
int.-OCH3 (25) 6.19
int.-OH (26) 8.24
int.-OH (27) 1.87
18
Forensic Science Quantum Chemistry
  • Future Projects
  • Compute low lying excited electronic and
    vibrational states to predict fluorescent/
    phosphorescent ability
  • Tailor molecules to cheap portable lasers!
  • Ruhemann's Purple-Transition Metal-Halide
  • Explore substituted ninhydrines
  • Derivatives of indanediones
  • Quantum Dots!
  • Clusters of Atoms
  • Exotic quantum properties
  • Phosphoresce well

19
Forensic Science Quantum Chemistry
  • Explosives Detection
  • Live in an age of terrorism
  • Many articles to examine
  • Ideally testing must be
  • Fast and user friendly
  • Portable
  • Safe and reliable
  • Lanthanide complexes
  • Have been useful for finger prints
  • Phosphoresce well
  • Coordinate well with explosives
  • Quantum Dots

20
Forensic Science Quantum Chemistry
  • Quantum Chemistry can help with design
  • Metal and Ligand excited states
  • Determine efficiency of metal-ligand energy
    transfer process
  • Indicate ligand structures to prevent binding of
    unwanted species
  • Metal-Ligand possibilities
  • Europium, Terbium
  • Derivatives of thenoyiltrifloroacetone and
    othrophanthrolene
  • Quantum dots
  • CdS, CdSe, GaAs, InAs

21
Forensic Science Quantum Chemistry
N
N
CF3
S
O
O
thenoyiltrifloroacetone
othrophanthrolene
22
Forensic Science Quantum Chemistry
  • Molecular Sensors
  • Miniaturization to the molecular level
  • Improve selectivity and detection limits
  • Widen range of detectable analytes
  • Sensor modeling allows optimization of response
    properties to analyte
  • Important factors
  • Molecular topology
  • Binding site geometry
  • Binding and stabilizing interactions
  • Few probes for illegal drugs, yet many binding
    sites

23
Forensic Science Quantum Chemistry
  • Molecular Sensors for canabinols and amphetamines
  • Species are of reasonable size

NH
OH
O
R
O
C5H11
O
Canabinol
3,4-Methylenedioxymethamph.
24
Forensic Science Quantum Chemistry
  • Ferrocene based barbiturate sensors

R
R
N
O
N
O
HN
HN
R
Fe
N
O
HN
R
Fe
O
N
HN
25
Acknowledgments
  • John Jay College of Criminal Justice
  • Our co-authors
  • Prof. Anne-Marie Sapse
  • Prof. Gloria Proni
  • Jennifer Jackiw
  • Our collaborators and colleagues
  • Prof. Thomas Kubic
  • Chris Chen
  • Chris Barden
  • Prof. Jon Riensrta-Kiracofe
  • Detective Nicholas Petraco (NYPD ret.)
  • Officer Patrick McLaughlin (NYPD)
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