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

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Fingerprint Amplification

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

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Fingerprint Amplification

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

Menzel et al.
Before
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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

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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.

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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.

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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
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General Scheme for the Reaction of Ninhydrin with
a-amino acids to form Ruhemanns Purple
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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
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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
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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

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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

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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)