NJC
Paper
and fluorescence experiments. Aliquots of the metal ions the progress of the reaction was monitored by TLC. After the
and amino acids under investigation were then injected into completion of the reaction, the reaction mixture was poured
the sample solution through a rubber septum in the cap. into 200 mL of water. The solution was neutralized with
The solutions were allowed to stabilize after each addition ammonium hydroxide to pH = 7 and was then cooled to room
and were then scanned.
temperature. The contents were filtered to yield crude precipitates,
which were then washed with large portions of water. Recrystalli-
zation of the crude product from a mixture of methanol and
General procedure for UV-vis and fluorescence experiments
UV-vis and fluorescence titrations were conducted on a 5 mM chloroform resulted in the formation of a pure product (1). Light
À1
solution of 1 in a 9 : 1 (v/v) aqueous acetonitrile (pH 7.0 HEPES yellow solid; 82% yield; m.p. (1C) 186; FT-IR (neat, n cm ): 3238
buffer) solution. All the UV-vis experiments were carried out on (O–Hstr.), 3019 (Ar-Hstr.), 1583 (Ar-CQCstr.), 1617 (–CQNstr.), 1234
1
a Shimadzu UV-240 spectrophotometer; while fluorescence (–C–Nstr.); H NMR (400 MHz, DMSO-d , ppm): 12.02 (brs, 2H,
6
spectra were recorded using a HITACHI-7000 spectrophoto- –NH, –OH), 8.21 (d, 1H, Ar-H, J = 8 Hz), 7.88 (d, 1H, Ar-H, J =
meter equipped with a 220–240 V Xe lamp with a quartz cell 8.2 Hz), 7.91 (d, 1H, Ar-H, J= 8.3 Hz), 7.59 (d, 4H, Ar-H), 7.50
1
3
of 1 cm width and 3.5 cm height. The excitation was carried out (td, J = 8 Hz, 1H, Ar-H), 7.41–7.29 (m, 8H, Ar-H); C NMR
at 350 nm for sensor 1 with 5 nm excitation and emission (100 MHz, DMSO-d , ppm): 154.5, 142.9, 132.2, 130.6, 128.4, 128.1,
slit widths in a fluorometer. The stock solution of sensor 1 127.9, 127.6, 127.1, 126.9, 124.4, 123.0, 118.3, 109.1; HRMS: m/z
6
À2
+
(
1 Â 10 M) was prepared in DMSO and was diluted with an (relative abundance (%), assignment) = 363.15 [100, (M + 1) ].
aqueous CH CN (v/v 9 : 1; pH = 7.0) solution for further different
3
spectroscopic experiments. All absorption scans were saved as
ACS II files and further processed in Excel(tm) to produce all Conflicts of interest
graphs shown.
There are no conflicts to declare.
1
General procedure for H NMR experiments
1
For H NMR titrations, two stock solutions were prepared
Acknowledgements
in DMSO-d
6
, one of them containing the host (1 of 3.94 Â
À2
1
0
M conc.) only and the other containing an appropriate
The authors are greatly thankful to the SAIF, Panjab University,
Chandigarh for recording the NMR spectra and are grateful to the
DST PURSE-II (Grant no. 48/RPC) for the financial assistance.
2
+
concentration of the guest (Hg ). Aliquots of the two solu-
tions were mixed directly in NMR tubes, which then were
diluted to 0.5 mL with DMSO-d if required.
6
General procedure for SPECFIT calculations
References
The spectral data obtained by UV-Vis or fluorescence titration
2
+
2+
3+
of the molecular probes with the analytes (Hg , Cu , Al and
cysteine) were analysed for their stoichiometries and binding
constant using SPECFIT programme version 3.0.36. The programme
was written by Robert A. Binstead, Andreas D. Zuberbuhler and
Bernhard Jung and was available commercially. The programme
performs global analysis of equilibrium and kinetic systems
with a singular value of decomposition and nonlinear-
regression modelling by the Levenberg–Marquardt method.
The programme simulates the absorption or fluorescence data
obtained experimentally. The spectra obtained using the UV-Vis
and fluorescence machines were converted to an ASCII file and
were transferred to MS-Excel spread sheets. These spread
sheets were converted to a text file. The file was imported into
SPECFIT/32 software and the data were simulated using different
stoichiometric models. The stoichiometry of the species formed,
distribution of the species and their association constants were
determined through a fit model.
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(
4
42 | New J. Chem., 2019, 43, 436--443
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