Electronic Supporting Information · S1 Electronic Supporting Information A Fluorescence ‘turn-on’ chemodosimeter for selective detection of Nb5+ ions in mixed aqueous media Abhishek

S1

Electronic Supporting Information

A Fluorescence ‘turn-on’ chemodosimeter for selective detection of

Nb5+

ions in mixed aqueous media

Abhishek Kumar Gupta, Abhimanew Dhir, Chullikkattil P. Pradeep*

School of Basic Sciences, Indian Institute of Technology Mandi, Himachal Pradesh 175001, India

Email Address: [email protected]

S2 Instruments and experimental procedures

S3 Synthetic details of 3

S4 1H NMR spectrum of 3

S5 13

C NMR spectrum of 3

S6 Mass spectrum of 3

S7 Fluorescence spectra response of 3 (1 μM) upon addition of various metal ions (1 -

320 μM) in THF/H2O (95:5, v/v) solutions

S8 1H NMR spectra of 3 + Nb

5+ and 3 in DMSO-d6

S9 1H NMR spectrum of 1 in DMSO-d6

S10 Fluorescence emission spectrum of 1-aminopyrene 2(1 μM) in THF/H2O (95:5, v/v)

S11 – S12 Mechanism of acid catalyzed hydrolysis of 3

S13 – S14 Mechanism of metal catalyzed hydrolysis of imines

S15 – S16 Spectrofluorometric titration of 3 (1 μM) with addition of Nb5+

(1.0 - 320.0 equiv.) in

THF/H2O (90:10, v/v) & (80:20, v/v) solutions.

Electronic Supplementary Material (ESI) for Dalton TransactionsThis journal is © The Royal Society of Chemistry 2013

mailto:[email protected]

S2

Instruments and experimental procedures

All reagents were purchased from Sigma Aldrich and were used without further purification.

HPLC grade THF was used to perform analytical studies. All the fluorescence spectra were

recorded on Agilent Technologies Cary Eclipse fluorescence spectrometer. UV-Vis spectra were

recorded on Shimadzu UV-2450 spectrophotometer and FT-IR spectra were recorded on

PerkinElmer FT-IR spectrometer (Spectrum Two, Serial No:88689). ESI-MS spectra were

recorded by using Waters-Q-Tof Premier-HAB213 instrument. 1H and

13C NMR spectra were

recorded on Bruker Avance II 400 NMR spectrometer using CDCl3 or DMSO-d6 as solvents and

TMS as internal standard. Data are reported as follows: chemical shift in ppm (), multiplicity (s

= singlet, d = doublet, br = broad singlet, m = multiplet), coupling constant J (Hz), integration,

and interpretation. Solution of compound 3 and metal chlorides were prepared in THF/H2O

(95:5, v/v). The H2O used for making THF/H2O mixtures was buffered with HEPES, pH = 7.0.1

1. D. D. Perrin, B. Dempsey, Buffers for pH and Metal Ion Control; John Wiley & Sons:

New York, 1974.


S3

Synthesis of 3 (C26H19NO3)

First we dissolved ethyl-3-formyl-4-hydroxybenzoate (1) (1mmol, 0.19 g) in 10 mL of MeOH.

To this solution, 1-aminopyrene (2) (1mmol, 0.22 g) in 10 mL MeOH was added drop wise. The

resulting solution turned from dark green to orange in color within 10 min. After 6 h, orange

colored precipitates were formed which were filtered, washed with cold ethanol and dried under

vacuum to get 3 in 85% yield;m.p 170C. IR(KBr, cm

-1)max = 1711 (C=O, ester), 1610 (C=N);

1H NMR (CDCl3, 400 MHz): m, H, CH3], 4.40 [m, 2H, CH2], 7.15 [d, J = 8.0Hz, 1H,

Ar-H] , 7.82 [d, J = 8.0 Hz, 1H, Ar-H], 8.01 - 8.27 [m, 9H, pyrene], 8.48 [d, J = 12.0 Hz, 1H,

Ar-H], 8.92 [s, 1H, HC=N], 14.26 [s, 1H, OH]. 13

C NMR (CDCl3, 100MHz): 14.4[CH3],

60.9[OCH2], 115.6 [Ar-C], 117.5[Ar-C], 119.1 [Ar-C], 121.8 [Ar-C], 122.1 [Ar-C], 124.6 [Ar-

C], 125.1 [Ar-C], 125.3 [Ar-C], 125.5 [Ar-C], 125.6 [Ar-C], 125.6 [Ar-C], 126.4 [Ar-C], 127.1

[Ar-C], 127.6 [Ar-C], 128.3 [Ar-C], 130.6 [Ar-C], 131.2 [Ar-C], 131.4 [Ar-C], 134.5 [Ar-

C],134.6 [Ar-C], 141.5 [Ar-C], 162.8 [Ar-C], 165.1 [Ar-C], 165.9 [Ar-C=N] ppm. ESI-MS: m/z

= 394.14 [M + H]+.


S4

1H NMR spectrum of 3


S5

13C NMR spectrum of 3


S6

Mass spectrum of 3

The peak at m/z 394.14 corresponds to [3+H]+


S7

Figure S1. Fluorescence spectra of 3 (1M) upon addition of various metal ions (1320 M) in

THF/H2O (95:5, v/v) solutions, ex= 342 nm.

400 450 500 550 600

0

30

60

90

120

150

180

Ta5+

Nb5+

3

V3+

Cr2+

Mn2+

Fe2+

Co2+

Ni2+

Cu2+

Zn2+

Zr4+

Nb5+

Mo5+

Ru4+

Rh3+

Pd2+

Ag+

Cd2+

Ta5+

W6+

Au3+

Hg2+

Pb2+

em = 428 nm

W6+

Inte

nsity (

a.u

)

Wavelength (nm)


S8


S9

NMR of 1 in DMSO


S10

Figure S2. Fluorescence emission spectrum of 1-aminopyrene 2 (1 µM) in THF/H2O (95:5,

v/v),ex= 342 nm.

350 400 450 500 550 600

0

50

100

150

200

250

Inte

nsity (

a.u

)

Wavelength (nm)

em= 428 nm

1-aminopyrene, 2


S11

Mechanism of acid catalyzed hydrolysis of 3

The detailed steps involved in acid catalyzed hydrolysis of imines are known.2

Based on that, the

possible steps in the case of 3 are given below.

Scheme S1

COOEt

OH

N H+

COOEt

OH

N

H

+

(I) (II)

H H

COOEt

OH

N

H

+

(II)

COOEt

OH

N

H

+

(II b)

HH

H

OH

COOEt

OH

CN

HO

H +

COOEt

OH

N+

(II b)

H H

(III)

HH


S12

OH

CN

HO

H

H

(III)

-H+

COOEt

OH

CN

O

H

H H

(IV)

H

COOEt

2. A. S. Kirdant, B. K. Magar and T. K. Chondhekar, J. Chem. Bio. Phy. Sci. Sec. A, 2011-2012,

2, 147 – 153.

COOEt

OH

H2N

O

+

COOEt

OH

N

OH

H

H+

(V)

-H+

Products

H

COOEt

OH

N

OH

H

H+

COOEt

OH

CN

O

H

H

(IV)

H

H+

(V)

H


S13

Mechanismof metal catalyzed hydrolysis of imines

The following intermediates are proposed for metal assisted hydrolysis of imines, in which an

enhancement of the substrate reactivity after association with the metal ion is observed.3

Scheme S2

In an alternate arrangement, the role of the metal ion is to activate the attacking water molecule

by bringing it closer to the C=N bond as shown below.

Scheme S3

N

Ar

OH

H

Mz+

N

ArO

H

H

Mz+

(B)

NAr

Mz+

NAr

Mz+

OHHO

HH

(A)


S14

For compound 3, the intermediates (A) and (B) can be written as follows, where there will be an

extra stabilization for the association of the metal ion with the substrate due to the involvement

of ortho phenolic O‒

group .

Scheme S4

3. V. G. Machado, M. G. Nascimento and M. C. Rezende, J. Braz. Chem. Soc., 1993, 4, 76 – 79.

O

N

Nb5+

O

HH

+

N

O

ONb5+

H

H

+

EtOOC

EtOOC

(A) (B)


S15

Figure S3. Spectrofluorometric titration of 3 (1 μM) with addition of Nb5+

(1.0-320.0 equiv) in

THF/H2O (90:10, v/v); λex= 342 nm; buffered with HEPES.


S16

Figure S4. Spectrofluorimetric titration of 3 (1 μM) with addition of Nb5+

(1.0-320.0 equiv) in

THF/H2O (80:20, v/v); λex= 342 nm; buffered with HEPES.

______________


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Electronic Supporting Information · S1 Electronic Supporting Information A Fluorescence ‘turn-on’ chemodosimeter for selective detection of Nb5+ ions in mixed aqueous media Abhishek