Transcript What Quantum Chemistry Can Do for Forensic Science

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
Outline
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How a Quantum Chemist can Help Forensic
Science
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History and Trivia on Fingerprints
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Ninhydrin + Alanine Gives Ruhemann’s Purple
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Results
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Future Applications for Forensic Science
More fingerprints
Explosives detection
Probes for illegal drugs
Forensic Science – Quantum Chemistry
A Potential Synergy
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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!
What Can We Learn From ?
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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
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Electronic Spectra
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Vibrational, Rotational Spectra
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NMR and ESR Spectra
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Thermodynamic data from Statistical-Mechanics
A Forensic Science Classic: Fingerprints!
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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
Fingerprint Amplification
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Latent prints, only trace amounts of biomaterial
–
Very hard or impossible to see by themselves.
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Solution: Use some kind of developing agent.
Fluorescence, Phosphorescence
I.S.C.
Singlet
Exc. State
Fluorescence
Triplet
Exc. State
Phosphorescence
Laser
Closed Shell Ground State
Fingerprint Amplification
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Fingerprint fluorescence is faint
Treat fingerprint with materials to obtain fluorescent or
phosphorescent compounds
Menzel et al.
Before
Menzel et al.
After
Ninhydrin-Ruhemann’s Purple System
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Ninhydrin first suggested to develop latent fingerprints in
1950’s.
Ninhydrin reacts with amino acids in fingerprints to produce
Ruhemann's purple
o
Brightly colored and easy to identify by eye
o
Fluoresces slightly at the 582 nm and 407 nm when
treated with a zinc or cadmium salts
o
Starting material, ninhydrin, is cheap
O
O
OH
O
N
OH
O
ninhydrin
OH
O
Ruhemann’s purple
Motivation
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Synthesize new compounds with properties superior to
Ruhemann's purple.
No known chemical system which offers significant advantages
in color to Ruhemann’s purple.

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An unequivocal understanding of the mechanism of formation for
Ruhemann’s purple is important!

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Ultimately we want to help improve chromogenic and fluorogenic
The mechanism for the reaction between amino-acids and ninhydrin was
fully settled.
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McCaldin Mechanism

Lamothe Mechanism

Friedman Mechanism
We have attempted to understand these mechanisms using
ab-inito computations.
Computational Methods
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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 > 0.0001 a.u.

Largest Abelian point groups used
Harmonic vibrational frequencies computed for all
structures using finite difference of analytic gradients.

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All computed structures found to be energetic minima
Benchmark structures for ninhydrin, alanine and
Ruhemann’s Purple were found using DFT B3LYP and a 631G**.
DFT Benchmark Structures
Structure (Abelian point group)
DFT 6-31G** B3LYP Energy (hartree)
Ninhydrin (C2)
-647.460616
Alanine (C1)
-323.747976
Ruhemann’s Purple isomer 1 (C1)
-1046.957475
0.971
106.1
1.399
1.214
113.5
1.549
1.483
1.085
0.967
Ruhemann’s Purple
103.9
1.337
107.6
1.395
1.088
110.4
1.216
121.0
1.394
1.086
1.406
105.8
121.0
1.085
1.393
1.395
110.3
107.5
1.405
121.1
105.8
110.0
1.489
121.1
1.086
ninhydrin
118.0
1.368
122.5
122.0
1.491
118.0
1.376
1.512
43.3
1.475
111.0
107.7
107.5
1.387
1.286
1.513
1.218
1.406
1.503
105.6
108.1
1.379
121.0
1.405
121.0
118.0
1.395
1.086
1.404
1.085
121.1
121.5
1.506
1.214
1.407
118.1
120.7
1.085
1.086
1.393
118.1
120.6
1.408
1.085
General Scheme for the Reaction of Ninhydrin with a-amino
acids to form Ruhemann’s Purple
CO2
ninhydrin + a-amino acid
Strecker degradation
Strecker degradation
intermediate
aldehyde
hydrindantin and possible
side products
dehydration
and hydrolysis
several intermediates
Ruhemann’s Purple
O
O
OH
O
H2N CHC OH
CH3
+
OH
O
OH
- H2O
a
1
ninhydrin
O
N CHC OH
O H CH3
McCaldin
- H2O
- CO2
b
alanine
O
H
N CH CH3
O
2
d
+ H2O
f
+ H2O
- NH3
e
N CH CH3
+ H2O
OH
OH
4
i
g
O
+ ninhydrin
- H2O
O
O
O
h
OH
NH
HO
OH
OH
+ ninhydrin
j + 2H+
- H2O
6
O
O
O
O
5
7
- H+
k -H O
2
O
O
OH
O
O
O
O
Ruhemann's Purple
isomer 2
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
3 + nin  5 + H2O
j 7 + nin + 2 H+ 
-8.42
1.36
O
NH
N
H
b 1  2 + H2O + CO2
i
OH
O
Ruhemann's Purple
isomer 1
O
7.08
O
N
HO
O
8 O
a ninhydrin + alanine 
1 + H2O
O
NH2
3
kcal/mol
c + 2H+
O
HCOCH3 +
Mechanism
DE
O
8 + H2O
O
Ruhemann's Purple
isomer 3
k 5  RP + H2O + H+
28.94
O
O
OH
O
H2N CHC OH
CH3
+
OH
O
OH
- H2O
a
1
ninhydrin
O
N CHC OH
O H CH3
- H2O
- CO2
b
alanine
O
H
N CH CH3
Lamothe
O
2
Mechanism
c + 2H+
O
HCOCH3 +
l
e
NH2
3
N CH CH3
+ H2O
OH
- H2O
+ ninhydrin
O
OH
4
n
OH
O
9
- H2O
o
O
O
N
H
O
O
Ruhemann's Purple
isomer 2
8.62
o 6 + 9  RP + H2O
-2.16
p 5’  RP + H2O
11.90
p - H2O
O
OH
O
8
O
N
HO
O
5'
O
O
OH
-10.90
5’ + H2O
NH
HO
O
+ ninhydrin
m -H O
2
m 6 + ninhydrin
O
NH
6
22.68
6 + 9 + H2O
n 3 + ninhydrin 
+
OH
3 + ninhydrin
kcal/mol
8 + H2O
+ ninhydrin
- H2O
O
OH
O
l
O
DE
O
Ruhemann's Purple
isomer 1
O
O
NH
O
O
Ruhemann's Purple
isomer 3
O
O
O
OH
- H2O
OH
r
O
O
ninhydrin
O
O + H2N CHC OH
CH3
10
OH
O
N CHC OH
O H CH3
1
s
alanine
t - H2O
O
COOH
N CH CH3
O
11
Mechanism
u - CO2
O
HCOCH3 +
O
NH2
w
+ H2O
OH
+ H2O
g
- NH3
3
O
v
N CH CH3
+ ninhydrin
- 2H2O
q
- 2H+
N CH CH3
O
OH
12
4
O
O
O
7
+ ninhydrin
j + 2H+
- H2O
O
O
OH
HO
O
O
8
O
O
OH
OH
O
N
H
N
O
O
Ruhemann's Purple
isomer 1
O
Ruhemann's Purple
isomer 2
O
O
NH
O
O
Ruhemann's Purple
isomer 3
Friedman
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 
20.52
RP + 2 H2O + 2 H+
O
O
OH
O
H2N C HC OH
C H3
+
OH
O
OH
- H2O
a
1
ninhydrin
O
N C HC OH
O H C H3
b
alanine
- H2O
- CO2
O
H
N C H C H3
O
2
d
+ H2O
c
O
HCOCH3 +
f
O
e
N H2
3
+ H2O
- NH3
OH
4
+ ninhydrin
- H2O
i
O
O
h
OH
OH
6
N C H C H3
+ H2O
OH
g
O
+ 2H+
O
OH
+ ninhydrin
j + 2H+
- H2O
O
O
OH
NH
HO
O
7
n
O
+ ninhydrin
- H2O
5
OH
HO
O
O
O
O
N
H
O
O
NH
O
NH
HO
O
O
O
Ruhemann's Purple
isomer 2
5'
O
p - H2O
O
O
N
OH
O
O
Ruhemann's Purple
isomer 3
O
O
Ruhemann's Purple
isomer 1
Our postulated mechanism at 25oC
New HF-6-31G** Results on Substituted
Ninhydrin-Ruhemann’s Purple Systems
O
Ruhemann’s
Purple Substitution
DE
2
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
O
OH
R
OH
O
+
R
O
H2N CHC OH
CH3
O
+ H2N CHC OH
OH
CH3
OH
O
O
O
R
+ HCOCH3 + 3 H2O + CO2
N
R
OH
O
Intermediate
Structures
R= H
F
NH2
OCH3
OH
O
OH
R
O
N CHC OH
O H CH3
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
Forensic Science – Quantum Chemistry
●
Future Projects
Compute low lying excited electronic and vibrational
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
Forensic Science – Quantum Chemistry
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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
Forensic Science – Quantum Chemistry
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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
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Metal-Ligand possibilities
Europium, Terbium
Derivatives of thenoyiltrifloroacetone and
othrophanthrolene
●
Quantum dots
CdS, CdSe, GaAs, InAs
Forensic Science – Quantum Chemistry
N
N
CF3
S
O
O
thenoyiltrifloroacetone
othrophanthrolene
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
•
Forensic Science – Quantum Chemistry
●
Molecular Sensors for canabinols and amphetamines
Species are of reasonable size
NH
OH
O
R
O
O
Canabinol
C5H11
3,4-Methylenedioxymethamph.
Forensic Science – Quantum Chemistry
●
Ferrocene based barbiturate sensors
R
R
N
N
R
O
HN
N
HN
Fe
HN
Fe
O
HN
R
O
O
N
Acknowledgments
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John Jay College of Criminal Justice
●
Our co-authors:
●
o
Prof. Anne-Marie Sapse
o
Prof. Gloria Proni
o
Jennifer Jackiw
Our collaborators and colleagues:
o
Prof. Thomas Kubic
o
Chris Chen
o
Chris Barden
o
Prof. Jon Riensrta-Kiracofe
o
Detective Nicholas Petraco (NYPD ret.)
o
Officer Patrick McLaughlin (NYPD)