Molecular Recognition by Picolylamine-Based 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 MercuryRatiometric Fluorescent Sensor

Hg2+

Chiroptical Response

CH3

CuII

HgII

Pattern Recognition: Signal Selectivity

-1

Hg2+

N

S

O

HO

N N

Next Generation Sensors for Hg2+

N

SO

HO

N NO

O

HO

O

O

OH

HOOC

1COOH

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.

N

N N

H H

SO

HO

OO OH

HOOC

OO OH

2

COOH

200 220 240 260 280 300 320 340

-5

0

5

10

15dZn2+

F (V

)

(n m )

0 1 2 302468

1012141618

Total Zn2+ (M)

F

307 (V

)

200 220 240 260 280 300 320 340-30

-25

-20

-15

-10

-5

0

5

(c)

Zn2+

+ (R,R)-2

lysozyme

F (

V)

(nm)

N

S

O

O

NN

O OAcAcO

O

O

I

N

S

O

O

NN

O

O

O

O

O

O

O

OO O

OO

OO

Exact Mass: 1221.30Molecular Weight: 1222.23

+

hydrolysis1.

Alkane Hydroxylation

• 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

CH2

R1

R2

Chiral-TPA Fe(II) Complexes

H2O2

CH

R1

R2

OH*

Fe(II)-TPA as Catalysts

K. Chen and L. Que, Jr, JACS, 2001, 123, 6327

Ligands: Achiral; Complexes: Octahedral

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

N

N N

N

N

N N

N

H HH

H H

N NHN

H

HN

Make Chiral Ligands and use their Fe-(II) complexes as catalysts

Systematically rigidify the chiral ligand to improve enantio- and regio- selectivity

Put Br on ligands to increase reactivity according DFT calculation

N

NN

N

Chiral podand piperidine quinuclidine

Podand and Piperidine Ligands

N

NN

NBr Br

H H

C21H20Br2N4Exact Mass: 486.01

Synthesis of Quinuclidines

CH

HC

H2C

COOC2H5

COOC2H5

HC CH2 C Cl

O

H2CCOOC2H5

COOC2H5

CH3NHOCH3

HC CH2 C N

O CH3

OCH3

LiN

Br

HC CH2 C OH

O

N

N N

H

H

Br Br

H

N

Br

NH3

HC CH2 CHN

Br

OH

HC CH2 CN

BrO

HC CH2 CHN

Br

OMs

MsCl

3

33

3

oxalyl chloride

3

29

1) HCl, reflux

2) 190oC+

C2H5OH + Na

3

(+)DIP-Cl

50oC

SSS-29

N

N N

H

H

Br Br

H

N

Br

C22H19Br3N4m/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 FundResearch Corporation for Science AdvancementPace University Scholarly Research FundPace University Kenan Faculty Development Fund