J Fluoresc
of Zn (II) ion due to its many advantageous as high selectivity
and sensitivity [31, 32].
Synthesis of (12E, 21E)-N1’,N3’-Bis(2-Hydroxybenzylidene)
Isophthalohydrazide
In the present study, we report a simple Isophthaloyl-based
highly selective and sensitive fluorescent receptor for Zn (II)
ion in presence of various metal ions such as Ag+, Al3+, Ca2+,
Cd2+, Co2+, Cu2+, Fe3+, Hg2+, K+, Mg2+, Na+ and Ni2+ in
CH3CN:H2O (1:1, v/v). The binding constant and stoichiometry
was computed with the Benesi–Hinderbrand plot and Job’s plot
respectively. The details characteristics of Receptor (1) have
been investigated by 1H NMR, 13CNMR, LC-MS and quantum
mechanical calculations at the level of density functional theory.
0.25 ml (1.02 mmol) of salicylaldehyde added drop wise to
the 200 mg (1.02 mmol) of Isophthaloyl dihydrazide dis-
solved in 25 ml of methanol with catalytic amount of acetic
acid, stirred at room temperature for 10–12 h gives1,3-
phenylenedi(carbonyl hydrazone) i.e. Receptor (1). The pre-
cipitate was filtered, washed with methanol and dried under
vacuum for 24 h (recrystallized from methanol) Yield 81%,
m.p. >270 °C.1H NMR (DMSO-d6,400 MHz, δ in ppm):δ
6.87—8.56 (m, 12H, ArH), 8.64 (s, 2H, N=CH), 11.34 (s,
2H, NH), 12.25 (s, 2H, OH) Fig. S3; 13C NMR (DMSO-
d6,400 MHz, in ppm): 162.16(–CONH–), 157.75 (-CH=N),
149.34 (-C-OH),133.03 (Ar), 131.11 (Ar), 130.84 (Ar),129.95
(Ar), 128.47 (Ar), 126.94 (Ar), 118.97 (Ar), 118.11 (Ar),
116.35 (Ar) Fig. S4; IR (KBr) ν(cm−1): 3309.85 (OH),
3078.39 (NH), 1666.50 (-NH-C=O), 1620.21 (C=O),
1573.91 (C=N), 1280.73 (N=CH) Fig. S5; Mass LC-MS
(ESI) m/z calc. For C22H18N4O4: 403.40112 [M + H]+, found:
403.14220 [M + H]+ Fig. S7.
Experimental
Chemicals and Instrumentation
All chemicals were purchased from sigma-Aldrich company.
All solvents and reagents used are of analytical grade and used
directly without purification. The UV-Vis spectra were obtain-
ed on Shimadzu UV 2450 spectrophotometer. Fluorescence
was recorded on Perkin Elmer model LS45 fluorescence spec-
trophotometer using a 1 cm path length quartz cuvette and
5 nm slit width. The fluorescence spectra were recorded from
400 nm to 700 nm at 390 nm excitation wavelength. Cyclic
voltametric (CV) measurements of the compounds in CH3CN
were conducted using K-Lyte 1.2 series electrochemical
analyser at room temperature. The electrolytic cell comprises
three electrodes, Pt as working electrode, Pt mesh auxiliary
electrode and Ag/AgCl as reference electrode (3 M KCl) sep-
arated from the sample solution by a salt bridge. The infrared
spectra were recorded on Shimadzu IR affinity spectropho-
Sample Preparation for Photo Physical Measurement
All the stock and working solutions were prepared in dou-
bled distilled water and analytical grade acetonitrile. The
nitrate salts of Ag+, Al3+, Ca2+, Cd2+, Co2+, Cu2+, Fe3+,
Hg2+, K+, Mg2+, Na+, Ni2+and Zn2+ were used to prepare
the stock solutions with concentration 1 × 10−3 M in water.
Synthesized receptor (1) was dissolved in mixed solution
of CH3CN:H2O (1:1, v/v) to give stock solution with con-
centration 1 × 10−2 M. The stock solutions were used after
appropriate dilution.
1
tometer using KBr. H NMR spectra were recorded on a
400 MHz spectrometer using tetramethylsilane (TMS) as an
internal standard. 13C NMR spectrums were recorded on a
400 MHz spectrometer in D6-DMSO.Mass spectrums were
obtained on water Q-TOF micro mass (LC-MS).
Results and Discussion
Synthesis of Receptor (1)
Fluorescence Spectral Measurement
Synthesis of Isophthaloyl Dihydrazide
In the present study receptor (1) was synthesized according to
Scheme 1. The photo-physical properties of receptor (1) were
discussed in detail. The photo-physical properties such as cat-
ion recognition ability of receptor (1) (1 × 10−5 M) was stud-
ied in CH3CN:H2O (1:1, v/v) for various metal ions (G = Ag+,
Al3+, Ca2+, Cd2+, Co2+, Cu2+, Fe3+, Hg2+, K+, Mg2+, Na+,
Ni2+ and Zn2+) (1 × 10−4 M) by fluorescence spectroscopy.
Receptor (1) bearing imine- N and hydroxyl–OH are well
known chelating group for transition metal ions. The possible
binding mechanism is based on two fundamental principles of
photo induced electron transfer (PET) and intra molecular
charge transfer (ICT).
Synthesis was carried out using 203 mg (1.0 mmol)
Isophthaloyl dichloride dissolved in 5 ml of dry methanol
along with catalytic amount of triethylamine and 0.12 ml
(2.2 mmol) hydrazine hydrate was added drop wise with con-
tinuous stirring at room temperature for 18 h gives
Isophthaloyl dihydrazide. Yield 84%, m.p. 222–5 °C, 1H
NMR (DMSO-d6,400 MHz, δ in ppm) δ: 9.82 s (2H, –
NH–); 8.24 t (H, –CH– Ar); 7.91 m (H, –CH– Ar); 7.51 t
(H,–CH– Ar); 4.53 s (4H, –NH2) Fig. S1; 13C NMR
(DMSO-d6, 100 MHz, in ppm): 165.41 (–CONH–); 133.49
(Ar); 129.26 (Ar); 128.40 (Ar); 126.00 (Ar) Fig. S2.