Supporting information for

Highly selective detection of Palladium and Picric acid by a

Luminescent MOF: A Dual functional fluorescent sensor

Suresh Sanda, Srinivasulu Parshamoni, Soumava Biswas and Sanjit Konar*

Department of Chemistry, IISER Bhopal, Bhopal-462066, India. Fax: +91-755-669-2392;

Tel: +91-755-6692339; E-mail: skonar@iiserb.ac.in

Experimental section:

Materials. All the reagents and solvents for synthesis were purchased from commercial sources and

used as supplied without further purification. Zn(NO3)2∙6H2O, 1,2,4,5,- Tetrakis (4-carboxyphenyl)

benzene (H4tcpb), Pd((NO3)2∙xH2O and all the nitro aromatic compounds and metal salts were

obtained from the Sigma-Aldrich Chemical Co. India.

Caution!: Picric acid is highly explosive and should be handled carefully and in small amounts.

Synthesis of ({[Zn(C34H18O8)0.5(C20N2H16)0.5]∙0.5(C20N2H16).2H2O]}n (1): 1,4-bis [2-(4-

pyridyl)ethenyl] benzene (bpeb) was synthesized by literature method.1 A mixture containing

Zn(NO3)2∙6H2O (41.4 mg, 0.14 mmol), 1,2,4,5-tcpb (40 mg, 0.07 mmol), bpeb (40.4 mg, 0.14 mmol)

dissolved in H2O (3 ml), DMF (3 ml), DMSO (2 ml) were placed in 15 ml Pressure tube and then 10

drops of NaOH (0.1 M) solution was added. The tube was properly sealed and kept at 150˚C for 12 h.

After cooling down the tube to room temperature, yellow colored X-ray quality crystals of compound

1 were obtained at the bottom of the tube (Yield = 20% based on metal). Elemental analysis: Anal.

Cald. C, 67.0%, N, 4.2%, H, 4.4%, Found: C, 67.8%, N, 4.9%, H, 3.9%. FT-IR (KBr pellet, cm-1

)

3459.4(br), 2912.1(s), 1667.8(s), 1441.4(m), 1412.6(w), 1392.2(s), 1255.7 (s), 1101.3 (s), 1064.3(w),

869.2(m).

Physical measurements: Thermo gravimetric analysis was recorded on Perkin-Elmer TGA 4000

instrument in the temperature range of 30-700˚C under N2 atmosphere with heating rate of 10˚C/min.

IR spectrum of the compound 1 was recorded on Perkin-Elmer FT-IR Spectrum BX using the KBr

pellets in the region 4000-400 cm-1

. Elemental analysis was carried out on Elementar Micro vario

Cube Elemental Analyzer. PXRD patterns were measured on PAnalytical EMPYRIAN instrument by

using Cu-Kα radiation. Absorption and emission spectra were recorded using a Carry 100 UV-vis

spectrophotometer (Agilent technologies) and a HORIBA JOBIN YVON made Fluoromax-4

spectrometer with stirring set up respectively. Life time measurements were performed on HORIBA

Scientific DeltaFlex TCSPC. Sorption analysis was performed using BelSorp-max.

Electronic Supplementary Material (ESI) for ChemComm.This journal is © The Royal Society of Chemistry 2015

Fluorescence experiments: In typical experimental setup, 1mg of compound 1 was dispersed in 1 ml

of DMF. In a 1 cm quartz cuvette, 3 mL solution of compound 1 in DMF was placed and the

fluorescence response upon excitation at 340 nm was measured in-situ after incremental addition of

freshly prepared analyte solutions in the range of 350-600 nm, while keeping 2 nm slit width for both

source and detector. To maintain homogeneity, solution was stirred at constant rate during

experiment.

Formula for calculating the percentage of Picric acid fluorescence intensity quenching:

(Io-I)/Io x 100%

Where, Io = initial fluorescence intensity,

I = intensity of 1 containing PA solution.

Reference: (a) S. Pramanik, C. Zheng, X. Zhang, T. J. Emge and J. Li, J. Am. Chem. Soc., 2011, 133,

4153; (b) D. Banerjee, Z. Hu and J. Li, Dalton Trans., 2014, 43, 10668.

Stern-Volmer equation:

I0/I = KSV[A] + 1

Where, I0 = fluorescent intensity of 1 before the addition of the analyte

I = fluorescent intensity after the addition of the respective analyte

KSV = Stern-Volmer constant

[A] = molar concentration of the analyte (M-1

).

For Pd2+

:

Figure S1: Fluorescence quenching of compound 1 by various concentration of Pd2+

, in which I0 and I

denote the intensity of the fluorescence signal of the sensing material in the absence and presence of

the analyte respectively. I0/I = KSV [Pd2+

] + 1 (Correlation coefficient, R2 = 0.98587).

Calculations for detection limit:

Figure S2: Fluorescence intensity as a function of Pd2+

ions concentration (Left), The change in

fluorescence intensity of compound 1 upon incremental addition of Pd2+

(1mM) solution in DMF

(Right).

The detection limit was calculated based on the fluorescence titration. The emission spectrum of

compound 1 was recorded by adding aliquots of Pd2+

solution in minimum concentrations and the

fluorescence intensity as a function of Pd2+

ions added was then plotted. So the detection limit was

calculated with the following equation: (Reference: (a) M. Kumar, N. Kumar and V. Bhalla, RSC

Adv., 2013, 3, 1097; (b) G. L. Long and J. D. Winefordner., Anal. Chem., 1983, 55, 712A, (c) B. Gole,

A. K. Bar and P. S. Mukherjee., Chem. Eur. J. 2014, 20, 2276; (d) B. Gole, A. K. Bar and P. S.

Mukherjee., Chem. Eur. J. 2014, 20, 13321).

Detection limit (DL) = Concentration of compound x Equiv. of Titrant at which change observed

Thus,

DL = 0.0015 x 2.2 x 10-4

= 3.3 x 10-7

mol = 0.03 ppm

Note: Although there is one more equation to determine the detection limit (i.e. Limit of Detection

(LOD) = 3Sigma/slope), but generally it has been used in the case of “enhancement in fluorescence

intensity”( References: (a) Chem. Commun., 2013, 49, 822. (b) RSC Adv., 2014, 4, 16104. (c)

Chem. Commun., 2011, 47, 8656). In this case above given equation was used to calculate detection

limit as the sensing occurs via fluoresce intensity quenching.

X-ray Single-Crystal structure Determination: Single crystal data for compound 1 was collected

on a Bruker APEX II diffractometer equipped with a graphite monochromator and Mo-Kα (λ=

0.71073 Å, 296 K) radiation. Data collection was performed using φ and ω scan. The structure was

solved using direct method followed by full matrix least square refinements against F2 (all data HKLF

4 format) using SHELXTL. Subsequent difference Fourier synthesis and least-square refinement

revealed the positions of the remaining nonhydrogen atoms. Determinations of the crystal system,

orientation matrix, and cell dimensions were performed according to the established procedures.

Lorentz polarization and multi-scan absorption correction were applied. Non-hydrogen atoms were

refined with independent anisotropic displacement parameters and hydrogen atoms were placed

geometrically and refined using the riding model. All calculations were carried out using SHELXL

97,2 PLATON 99,

3 and WinGXsystemVer-1.64.

4 During the final stages of refinement, some Q peaks

having high electron densities were found in compound 1 which probably correspond to highly

disordered solvent water molecules and are removed by SQUEEZE 4 program. From the TG analysis,

we have calculated that in compound 1 two guest water molecules are present and hence those are

included in the molecular formula. Data collection and structure refinement parameters and

crystallographic data for compound 1 is given in Table S1. Selected bond lengths and bond angles are

given in Table S2.

Figure S3. Asymmetric unit of compound 1. Color code: Zinc (green), Oxygen (red), Nitrogen (blue),

Carbon (grey). (Hydrogen atoms are omitted for clarity).

Figure S4: Co-ordination environment around the Zn (II) center. Color code: same as figure S3.

Figure S5: Connectivity between four SBUs through tcpb ligand on bc-plane. Color code: same as

figure S3.

Figure S6: Illustration of non-covalent interactions between free bpeb linker and coordinated ligands

inside the framework. Color code: same as figure S1.

Table S1: Summary of crystallographic data for compound 1

CCDC 1038426

Formula C37H29N2O6Zn

weight (g/mol) 662

Crystal shape Block

Colour Yellow

Size 0.45×0.34×0.25

Crystal system Triclinic

Space group P-1

Cell length a (Å) 9.8824(7)

Cell length b (Å) 11.5480(8)

Cell length c (Å) 15.6480(11)

Cell angle alpha (° ) 89.784(3)

Cell angle beta (° ) 76.441(3)

Cell angle gamma (° ) 75.603(3)

Cell volume V (Å3) 1678.67

Cell formula units Z 2

Temperature (K) 113(2)

λ (Mo Kα) (Å) 0.71073

μ (mm−1

) 0.771

Dc (g cm−3

) 1.240

crystal_F_000 646.0

Measured reflections 8032

Unique reflections 7138

R1[I>2σ(I)]a 0.040

Rw[I>2σ(I)]b 0.096

aR1 = Σ||Fo|−|Fc||/Σ|Fo,

bRw=[Σ{w(Fo

2−Fc

2)

2}/Σ{w(Fo

2)

2}]

1/2

Table S2: Selected bond lengths (Å) and bond angles (deg)

Bond Angle Bond length

O1-Zn1-N1 109.08(6) Zn1-O1 2.025(1)

O1-Zn1-O2 158.65(6) Zn1-N1 2.028(1)

O1-Zn1-O5 91.86(6) Zn1-O2 2.064(1)

O1-Zn1-O6 87.80(6) Zn1-O5 2.048(2)

N1-Zn1-O2 92.24(6) Zn1-O6 2.030(1)

N1-Zn1-O5 97.74(6)

N1-Zn1-O6 101.83(6)

O2-Zn1-O5 86.27(6)

O2-Zn1-O6 86.62(6)

O5-Zn1-O1 91.86(6)

O5-Zn1-O2 86.27(6)

O5-Zn1-O6 159.41(6)

O5-Zn1-N1 97.74(6)

O2-Zn1-N1 92.24(6)

O6-Zn1-N1 101.83(6)

Thermal and PXRD Analysis:

Thermogravimetric analysis (TGA) of compound 1 shows a first step weight loss of 5% in the range

of 90-130˚C could be due to the loss of guest H2O molecules and the de-solvated framework was

found to be stable up to 250˚C (Fig. S7). The powder XRD pattern of 1 is in very good

correspondence with the simulated pattern of the single crystal, indicating the phase purity of bulk

sample (Fig. S8).

Figure S7: TGA Plot of compound 1.

Figure S8: PXRD patterns of compound 1. Simulated (red), As-synthesized (black).

Figure S9: Emission spectrum of compound 1 dispersed in DMF upon excitation at 340 nm.

Figure S10: The change in fluorescence intensity of compound 1 upon incremental addition of NB

(1mM) solution in DMF.

Figure S11: The change in fluorescence intensity of compound 1 upon incremental addition of 2,6-

DNT (1mM) solution in DMF.

Figure S12: The change in fluorescence intensity of compound 1 upon incremental addition of 2,4-

DNT (1mM) solution in DMF.

Figure. S13: The change in fluorescence intensity of compound 1 upon incremental addition of 4-NT

(1mM) solution in DMF.

Figure. S14: The change in fluorescence intensity of compound 1 upon incremental addition of 1,2-

DNB (1mM) solution in DMF.

Figure. S15: The change in fluorescence intensity of compound 1 upon incremental addition of 1,3-

DNB (1mM) solution in DMF.

Figure. S16: The change in fluorescence intensity of compound 1 upon incremental addition of 1,4-

DNB (1mM) solution in DMF.

Figure. S17: Emission spectrum of compound 1 upon incremental addition of DMB (1mM) solution

in DMF.

Figure. S18: Emission spectrum of compound 1 upon incremental addition of BB (1mM) solution in

DMF.

Figure. S19: Emission spectrum of compound 1 upon incremental addition of 1,2-DAB (1mM)

solution in DMF.

Figure S20: Fluorescence decay profile of 1 in the presence and absence of picric acid. (IRF =

Instrument Response Function)..

Compound Life time (Sec)

1 5.11 x 10-10

1 + PA 4.96 x 10-10

Figure S21: UV-vis spectra of compound 1 upon gradual addition of PA showing spectral change with

the appearance of new band at 423 nm.

Figure S22: UV-vis spectra of compound 1 in the presence of different nitro analytes.

Figure. S23: The change in fluorescence intensity of compound 1 upon incremental addition of

Catechol (1mM) solution in DMF.

Figure. S24: The change in fluorescence intensity of compound 1 upon incremental addition of 4-Iodo

phenol (1mM) solution in DMF.

Figure. S25: The change in fluorescence intensity of compound 1 upon incremental addition of 4-

methoxy phenol (1mM) solution in DMF.

Figure. S26: The change in fluorescence intensity of compound 1 upon incremental addition of

Phloroglucinol (1mM) solution in DMF.

Figure S27: The change in fluorescence intensity of compound 1 upon addition of NB followed by

PA.

Figure S28: The change in fluorescence intensity of compound 1 upon addition of 2,6-DNT followed

by PA.

Figure S29: The change in fluorescence intensity of compound 1 upon addition of 2,4-DNT followed

by PA.

Figure S30: The change in fluorescence intensity of compound 1 upon addition of 4-NT followed by

PA.

Figure S31: The change in fluorescence intensity of compound 1 upon addition of 1,2-DNB followed

by PA.

Figure S32: The change in fluorescence intensity of compound 1 upon addition of 1,3-DNB followed

by PA.

Figure S33: The change in fluorescence intensity of compound 1 upon addition of 1,4-DNB followed

by PA.

Figure S34: N2 adsorption isotherm of compound 1.

Figure S35: HOMO and LUMO energy levels and shapes of the molecular orbitals considered for

nitroanalytes. (investigated by the B3LYP/6-31G** method).

Table S3:- HOMO and LUMO energies calculated for nitroanalytes at B3LYP/6- 31G* level of

theory.

Analytes HOMO (ev) LUMO (eV) Band gap (eV)

PA -8.327 -3.898 4.339

1,4-DNB -8.350 -3.496 4.854

1,3-DNB -8.412 -3.135 5.277

1,2-DNB -7.935 -3.034 4.901

2,4-DNT -8.113 -2.976 5.137

2,6-DNT -7.905 -2.861 5.044

NB -7.593 -2.431 5.162

4-NT -7.363 -2.317 5.046

Figure S36: Spectral overlap between normalized emission spectra of compound 1 and normalized

absorbance spectra of nitro analytes.

Figure S37: PXRD patterns of compound 1: asynthesized (black) and after immersion in Pd2+

solution

for 24 hrs (green).

Figure S38: Fluorescence decay profile of 1 in the presence and absence of Pd2+

solution. (IRF =

Instrument Response Function).

Figure S39: Emission spectrum of compound 1 upon incremental addition of Cr2+

(1mM) solution in

DMF.

Compound Life time (Sec)

1 5.11 x 10-10

1 + Pd2+

5.13 x 10-10

Figure S40: Emission spectrum of compound 1 upon incremental addition of Mn2+

(1mM) solution in

DMF.

Figure S41: Emission spectrum of compound 1 upon incremental addition of Co2+

(1mM) solution in

DMF.

Figure S42: Emission spectrum of compound 1 upon incremental addition of Ni2+

(1mM) solution in

DMF.

Figure S43: Emission spectrum of compound 1 upon incremental addition of Cu2+

(1mM) solution in

DMF.

Figure S44: Emission spectrum of compound 1 upon incremental addition of Ag2+

(1mM) solution in

DMF.

Figure S45: Emission spectrum of compound 1 upon incremental addition of Pt2+

(1mM) solution in

DMF.

Figure S46: Emission spectrum of compound 1 upon incremental addition of Pb2+

(1mM) solution in

DMF.

Figure S47: Emission spectrum of compound 1 upon incremental addition of Eu3+

(1mM) solution in

DMF.

Figure S48: The change in fluorescence intensity of compound 1 upon addition of Cr2+

solution

followed by Pd2+

solution.

Figure S49: The change in fluorescence intensity of compound 1 upon addition of Mn2+

solution

followed by Pd2+

solution.

Figure S50: The change in fluorescence intensity of compound 1 upon addition of Co2+

solution

followed by Pd2+

solution.

Figure S51: The change in fluorescence intensity of compound 1 upon addition of Ni2+

solution

followed by Pd2+

solution.

Figure S52: The change in fluorescence intensity of compound 1 upon addition of Cu2+

solution

followed by Pd2+

solution.

Figure S53: The change in fluorescence intensity of compound 1 upon addition of Ag2+

solution

followed by Pd2+

solution.

Figure S54: The change in fluorescence intensity of compound 1 upon addition of Pt2+

solution

followed by Pd2+

solution.

Figure S55: The change in fluorescence intensity of compound 1 upon addition of Pb2+

solution

followed by Pd2+

solution.

Figure S56: The change in fluorescence intensity of compound 1 upon addition of Eu3+

solution

followed by Pd2+

solution.

Figure S57: Increase in absorbance of compound 1 upon addition of Pd2+

solution.

Figure S58: UV-vis spectra of compound 1 in the presence of different metal ions.

Figure S59: Job’s plot of Compound 1 showing the 1:2 stoichiometry of the complex between Pd2+

ion

and compound 1. The total concentration of compound 1 and Pd2+

ion is 50 mM.

References:

1. A. V. Gutov, E. B. Rusanov, L. V. Chepeleva, S. G. Garasevich, A. B. Ryabitskii, A. N. Chernega

Russ. J. Gen. Chem. 2009, 79, 1513-1518.

2. G. M. Sheldrick,. SHELXL 97, Program for Crystal Structure Refinement; University of Gottingen:

Gottingen, Germany, 1997.

3. A. L. Spek, J. Appl. Crystallogr. 2003, 36, 7.

4. L. J. Farrugia,. J. Appl. Crystallogr. 1999, 32, 837.