(1) and New York University (2)

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Molecular Recognition by PicolylamineBased Tripodal Ligands and Its Application
in Sensing and Asymmetric Catalysis
Amanda Mickley,1 Patrick Carney,1 Steven Lopez,2
Jennifer Lee,2 and Zhaohua Dai1,*
Chemistry Departments of Pace University (1) and New York University (2)
Objective
• Improve the selectivity in the detection of Hg(II) through a
stereochemical approach which systematically employs
chiral podand, piperidine bearing ligands sulfur atoms;
• Improve Hg(II) sensing sensitivity by using circularly
polarized fluorescence excitation (CPE);
• Systematically develope Fe(II) complexes of TPA-based
chiral podands, piperidines and quinuclidines as green
asymmetric catalysts for better product control and
prediction in alkane hydroxylation by H2O2. Elucidate its
mechanism
• Elucidate mechanism to facilitate the better understanding
of the interactions operating the above-mentioned
molecular recognition events
Chiroptical Fluorescence Sensors for Mercury
1st Genearation Sensor for Mercury
Ratiometric Fluorescent Sensor
Hg2+
Chiroptical Response
HgII
CuII
CH3
Pattern Recognition:
Signal Selectivity
Hg2+
O
S
HO
N
N
-1
N
Next Generation Sensors for Hg2+
O
HO
O
S
HO
N
N
HOOC
N
O
O
COOH
1
OH
O
O
OH
O
O
HOOC
OH
COOH
N
S
HO
N
Zn
0
1
2
3
2+
Total Zn (M)
0
-5
H
200 220 240 260 280 300 320 340
(n m )
2
+ (R,R)-2
-5
-10
-15
-20
Zn
-25
N
H
5
lysozyme
0
2+
F (V)
10
O
5
18
16
14
12
10
8
6
4
2
0
F307 (V)
d 15
F (V)
O
We intend to use these ligands
to further develop circularly
polarized fluorescence
excitation (CPE), which is
based on fluorescence-detected
circular dichroism, which gives
better contrast and eliminates
many spectral interferences.
(c)
2+
-30
200 220 240 260 280 300 320 340
 (nm)
I
O
S
O
O
+
N
O
N
N
AcO
O
OAc
O
S
O
N
N
N
O
O
O
O
O
hydrolysis
1.
O
O
O
O
O
O
O
Exact Mass: 1221.30
Molecular Weight: 1222.23
O
O
Alkane Hydroxylation
R1
Chiral-TPA Fe(II) Complexes
R1
*
CH2
R2
CH
H2O2
OH
R2
• Converting saturated C-H bonds directly into
alcohols
• Important to synthetic organic chemistry, fuel
industry and other industries using petrochemical
feed stock
• Helpful in modeling electron-transfer processes in
biological systems, and producing new catalysts
Fe(II)-TPA as Catalysts
Ligands: Achiral; Complexes: Octahedral
K. Chen and L. Que, Jr, JACS, 2001, 123, 6327
Products: Regio-selective, Diastereo-selective
•Not enantio-selective
Rigidification Enhances Enantiomeric
and Regional Selectivity
M. S. Chen, M. C. White. Science, 2007, 318, 783.
Our Approach
Make Chiral Ligands and use their Fe-(II) complexes as
catalysts
N
N
Systematically rigidify the chiral ligand to improve
enantio- and regio- selectivity
N
N
Put Br on ligands to increase reactivity according DFT
calculation
N
N
N
H
N
H
H
Chiral podand
N
N
H
N
H
N
N
piperidine
N
N
H
H
N
H
quinuclidine
Podand and Piperidine Ligands
Br
Br
N
N
N
N
H
H
C21H20Br2N4
Exact Mass: 486.01
Synthesis of Quinuclidines
HC COOC2H5
CH
+ H2C
H2C COOC2H5
COOC2H5
O
1) HCl, reflux
C2H5OH + Na
oxalyl chloride
HC CH2 C OH
COOC2H5
o
2) 190 C
3
Br
N
CH3NHOCH3
O
HC CH2 C Cl
O
Br
O
Li
CH3
HC CH2 C
HC CH2 C N
3
OCH3
3
3
Br
Br
Br
(+)DIP-Cl
Br
N
HC CH2 CH
3
OH
NH3
N
MsCl
HC CH2 CH
N
OMs
Br
N
N
H
N
H
N
o
3
50 C
H
29
SSS-29
Br
Br
Br
N
N
H
N
H
N
H
C22H19Br3N4
m/e: 577.91 (100.0%),
579.91 (97.6%), 575.92
(34.3%), 581.91 (31.9%),
SSS-29 Purity and Cu(II) Complex
Acknowledgement
• Prof. James Canary (NYU)
• Prof. Demosthenese Athanasoupolos (Pace)
• Kirill Grinberg (Midwood High School)
Funding:
ACS Petroleum Research Fund
Research Corporation for Science Advancement
Pace University Scholarly Research Fund
Pace University Kenan Faculty Development Fund