SUPPORTING INFORMATION

Bis(Pyrrole-benzimidazole) conjugates as novel colorimetric sensors for anionsSANJEEV PRAN MAHANTAa,* and PRADEEPTA KUMAR PANDAb,*

aDepartment of Chemical Sciences, Tezpur University, Napaam, Assam, 784 028 IndiabSchool of Chemistry, University of Hyderabad, Hyderabad, Telengana, 500 046 India

Email: spm@tezu.ernet.in; pkpsc@uohyd.ernet.in*For Correspondence

Table of Contents

Materials and Methods

Materials and Methods

Synthesis of the PYBI conjugates

Spectral data

1H NMR and 13C NMRspectra of compounds

Absorption and Emission data

Anion Binding Study

Computational Study

4-nitro-o-phenylenediamine and tetrabutyl ammonium salts of anions studied were purchased

from sigma Aldrich and were used as received.Pyrrole, o-phenylenediamine, phosphorous

oxychloride, oxalyl chloride, nitro benzene were purchased from Sisco research laboratories.

Pyrrole, phosphorous oxychloride and solvents used in the synthesis were dried and distilled

prior to use. Spectroscopic grade DMSO (Merck) was used for recording all spectrophotometric

data.

Melting points were determined on MR-Vis+ visual melting point range apparatus from

LABINDIA instruments private limited. IR spectra were recorded on a JASCO FTIR model

5300 and NICOLET 5700 FT-IR spectrometer. NMR spectra were obtained on Bruker 400 MHz

FT-NMR spectrometer operating at ambient temperature. TMS was used as internal standard for 1H NMR spectra. LCMS were carried out by Shimadzu-LCMS-2010 mass spectrometer.

Elemental analyses were obtained through ThermoFinnigan Flash EA 1112 analyzer. UV-Vis

spectra were recorded on Perkin Elmer Lambda 35 UV-Vis spectrophotometer. Fluorescence

spectra were recorded on Horiba ZobinYovan Fluoromax-4 instrument.

The geometries of monomeric PYBI moieties 1a-b and their anion complexes (1a.F-, 1b.F-,

1b.CH3COO-, 1b.H2PO4-) were fully optimized at the B3LYP/6-311+G (d,p) level under the

polarizable continuum model (PCM) using DMSO as the solvent(ESI). The relative H-bonding

affinity of the two N-H donor units was studied with Natural Bond Orbital (NBO) analysis. All

calculations were performed with the Gaussian 09 program.S1

Synthesis of the PYBI conjugates:

To a solution of diamine derivative (1mmol) in nitrobenzene, aldehyde derivative (1 mmol) was

added. The reaction mixture was heated at 120°C for 24 h. The precipitated solid was filtered,

washed with first hexane and then diethyl ether and purified by column chromatography on silica

gel with 1% MeOH in CHCl3 as eluent. Subsequently, the product was recrystallized from 1:1

acetone and methanol mixture.

The precursor dialdehydes for the synthesis of 2 and 3 were prepared by following literature reported procedures.S2,S3

Scheme S1: Synthesis of 1a-b.

Scheme S2: Synthesis of 2a-b.

Scheme S3: Synthesis of 3.

Spectral data of compound 1a:Yield: 55 %; 1H-NMR (400 MHz, CDCl3) : δ 12.48 (s, 1H, NH), 11.79 (s, 1H, NH), 7.48 (d, br, 2H, CH), 7.12 (q, 2H, CH, 2.88 Hz), 6.92 (m, 1H, α-CH), 6.84 (m, 1H, β-CH), 6.19 (m, 1H, β-CH).13C-NMR (100 MHz, CDCl3) :δ 147.24, 123.13, 121.88, 121.79, 109.61, 109.50. LCMS m/z calcd. for C11H9N3 (M+H) 184.08, found 184.08; Elemental analysis: calcd. C: 72.11; H: 4.95; N: 22.94, found C: 72.26; H: 4.89; N: 22.85.

Spectral data of compound1b:Yield: 46 %; 1H-NMR (400 MHz, CDCl3) : δ 13.22 (s, br, 1H, NH), 12.04 (s, 1H, NH), 8.31 (s, 1H, CH), 8.08 (d, 1H, CH, 8.8 Hz), 7.65 (s, 1H, CH), 7.00 (d, 2H, β-CH), 6.25 (s, 1H, β-CH).13C-NMR (100 MHz, CDCl3) :δ 151.08,142.22, 123.04, 121.54, 117.7, 111.11, 109.84.

LCMS m/z calcd. for C11H8N4O2 (M+H) 229.06, found 229.07; Elemental analysis: calcd. C: 57.89; H: 3.53; N: 24.55, found C: 57.76; H: 3.45; N: 24.61.

Spectral data of compound 2a:Yield: 48%; 1H-NMR (400 MHz, CDCl3) : δ 12.43 (s, br, 2H, NH), 11.79 (s, 2H, NH), 7.55 (s, br, 4H, CH), 7.42 (s, 4H, CH), 7.12 (m, 2H, CH), 6.71 (s, 2H, β-CH), 1.78 (s, 6H, CH 3).13C-NMR (100 MHz, CDCl3) :δ 147.28, 143.18, 122.78, 121.84, 109.11, 105.68, 35.42, 28.26. LCMS m/z calcd. for C25H22N6 (M+H) 407.19, found 407.19; Elemental analysis: calcd. C: 73.87; H: 5.46; N: 20.67, found C: 73.69; H: 5.58; N: 20.42.

Spectral data of compound 2b:Yield: 41%; 1H-NMR (400 MHz, CDCl3): δ 13.15 (d, 2H, NH, 16 Hz), 11.97 (s, 2H, NH), 8.37 (s, 1H, CH), 8.25 (s, 1H, CH), 8.08 (d, 2H, CH, 8 Hz), 7.71 (s, 1H, CH), 7.69 (s, 1H, CH), 6.86 (d, 2H, β-CH, 12 Hz), 6.09 (t, 2H, β-CH, 4 Hz), 1.81 (s, 6H, CH3).13C-NMR (100 MHz, CDCl3) :δ 150.51, 144.03, 143.39, 142.42, 141.80, 139.76, 117.73, 112.96, 110.72, 106.82, 106.19, 35.21, 17.68. LCMS m/z calcd. for C25H20N8O4 (M+H) 497.16, found 497.17; Elemental analysis: calcd. C: 60.48; H: 4.06; N: 22.57, found C: 60.36; H: 4.12; N: 22.68.

Spectral data of compound3:Yield: 39%; 1H-NMR (400 MHz, CDCl3): δ 12.79 (s, 2H, NH), 12.08 (s, 2H, NH), 8.11 (m, 2H, CH), 7.82 (m, 2H, CH, 4 Hz), 7.56 (t, 4H, CH, 8 Hz), 7. 17 (s, 4H, CH), 6.96 (s, 2H, β-CH), 6.30 (d, 2H, β-CH, 4 Hz).13C-NMR (100 MHz, CDCl3): δ 146.13, 145.17, 140.30, 132.04, 130.41, 128.80, 125.79, 122.39, 113.14, 111.19. LCMS m/z calcd. for C30H20N8 (M+H) 493.18, found 493.18; Elemental analysis: calcd. C: 73.16; H: 4.09; N: 22.75, found C: 73.28; H: 4.15; N: 22.61.

FigureS1:1H NMR spectrum of compound 1a in DMSO-d6.

FigureS2:13C NMR spectrum of compound 1a in DMSO-d6.

FigureS3:1H NMR spectrum of compound 1b in DMSO-d6.

FigureS4:13C NMR spectrum of compound 1b in DMSO-d6.

FigureS5: 1H NMR spectrum of compound 2a in DMSO-d6.

FigureS6:13C NMR spectrum of compound 2a in DMSO-d6.

FigureS7:1H NMR spectrum of compound 2b in DMSO-d6.

FigureS8:13C NMR spectrum of compound 2b in DMSO-d6.

FigureS9:1H NMR spectrum of compound 3in DMSO-d6.

FigureS10:13C NMR spectrum of compound 3in DMSO-d6.

Figure S11: UV-Vis and fluorescence spectra of compound 1a-bin DMSO. Left: 1a(red: absorption, black: emission spectra, λexc = 313 nm). Right: 1b(absorption spectra).

FigureS12: UV-Vis and fluorescence spectra of compound 2a-bin DMSO. Left: 2a(red: absorption, black: emission spectra, λexc = 313 nm). Right: 2b(absorption spectra).

FigureS13: UV-Vis and fluorescence spectra of compound 3in DMSO(red: absorption, black: emission spectra, λexc = 421 nm).

Figure S14: UV-Vis spectra of 1a(20 μM)in DMSOin presence of different anions.

Figure S15: Evolution of UV-Vis spectra of 1a (20 μM)upon gradual addition of TBAF (0 to 15 mM).

Figure S16:Job’s plots for complexation of receptor 1a with fluoride ([1a] + [TBAF] = 40 μM).

Figure S17:Bensei-Hildebrand plot of 1/[A0-A] vs. 1/[TBAF] from the titration data for 1a.

Figure S18: Left: Fluorescence spectra of 1a (1 μM)in DMSO in presence of different anions; right: changes in the fluorescence spectra of 1a (1 μM) upon gradual addition of TBAF (0 to 1.5 mM).

Figure S19: Changes in the 1H NMR spectra of 1a (5 mM)inDMSO-d6upon gradual addition of TBAF (0 to 12 mM).

Scheme S4: Proton transfer process involved in 1a-.

FigureS20:Left: UV-Vis spectra of 1b(20 μM) in DMSOin presence of different anions; right: Naked eye view of the colour change while addition of different anions as its tetrabutyl ammonium salt to the solution of 1b in DMSO.

Figure S21: Evolution of UV-Vis spectra of 1b (20 μM) in DMSOupon gradual addition of TBAF (0 to 3.5 × 10-4 M).

Figure S22:Job’s plots for complexation of receptor 1bwith fluoride ([1b] + [TBAF] = 40 μM).

Figure S23:Bensei-Hildebrand plot of 1/[A0-A] vs. 1/[TBAF] from the titration data for 1b.

Figure S24: Changes in the 1H NMR spectra of 1b (5 mM)inDMSO-d6upon gradual addition of TBAF(0 to 30 mM).

Figure S25: Evolution of UV-Vis spectra of 1b (20 μM) in DMSOupon gradual addition of TBAOAc (0 to 4.3 × 10-4 M).

Figure S26: Job’s plots for complexation of receptor 1b with acetate ([1b] + [TBAOAc] = 40 μM).

Figure S27:Bensei-Hildebrand plot of 1/[A0-A] vs. 1/[TBAOAc] from the titration data for 1b.

Figure S28: Changes in the 1H NMR spectra of 1b (5 mM)inDMSO-d6upon gradual addition of TBAOAc(0 to 12 mM).

Figure S29:Probable coordination mode of 1b- with acetate ion.

Figure S30: Evolution of UV-Vis spectra of 1b (20 μM) in DMSOupon gradual addition of TBAPh (0 to 1.3 × 10-3 M).

Figure S31:Job’s plots for complexation of receptor 1b with phosphate ([1b] + [TBAPh] = 40 μM).

Figure S32:Bensei-Hildebrand plot of 1/[A0-A] vs. 1/[TBAPh] from the titration data for 1b.

Figure S33: UV-Vis spectra of 2a(20 μM)in DMSOin presence of different anions.

Figure S34:Evolution of UV-Vis spectra of 2a (20 μM)upon gradual addition of TBAF (0 to 12 mM).

Figure S35: Job’s plots for complexation of receptor 2a with fluoride ([2a] + [TBAF] = 40 μM).

Figure S36:Bensei-Hildebrand plot of 1/[A0-A] vs. 1/[TBAF] from the titration data for 2a.

Figure S37: Left: Fluorescence spectra of 2a (1 μM)in DMSOin presence of different anions; right: changes in the fluorescence spectra of 2a (1 μM) upon gradual addition of TBAF (0 to 2.0 mM).

FigureS38: Left: UV-Vis spectra of 2b (20 μM) in DMSOin presence of different anions; right: Naked eye view of the colour change while addition of different anions as its tetrabutyl ammonium salt to the solution of 2b in DMSO.

Figure S39: Evolution of UV-Vis spectra of 2b (20 μM) in DMSOupon gradual addition of TBAF (0 to 6.13 × 10-4 M).

Figure S40:Job’s plots for complexation of receptor 2bwith Fluoride ([2b] + [TBAF] = 40 μM).

Figure S41:Bensei-Hildebrand plot of 1/[A0-A] vs. 1/[TBAF] from the titration data for 2b.

Figure S42: Changes in the 1H NMR spectra of 2b (5 mM)in DMSO-d6upon gradual addition of TBAF (0 to 20 mM).

Figure S43: Evolution of UV-Vis spectra of 2b (20 μM) in DMSOupon gradual addition of TBAOAc (0 to 5.2 × 10-4 M).

Figure S44:Job’s plots for complexation of receptor 2b with acetate ([2b] + [TBAOAc] = 40 μM).

Figure S45:Bensei-Hildebrand plot of 1/[A0-A] vs. 1/[TBAOAc] from the titration data for 2b.

Figure S46: Changes in the 1H NMR spectra of 2b (5 mM)in DMSO-d6upon gradual addition of TBAOAc (0 to 16.5 mM).

Figure S47: Evolution of UV-Vis spectra of 2b (20 μM) in DMSOupon gradual addition of TBAPh (0 to 1.0 × 10-3 M).

Figure S48:Job’s plots for complexation of receptor 2b with phosphate ([2b] + [TBAPh] = 40 μM).

Figure S49:Bensei-Hildebrand plot of 1/[A0-A] vs. 1/[TBAPh] from the titration data for 2b.

FigureS50: Left: UV-Vis spectra of 3(20 μM) in DMSOin presence of different anions; right: Naked eye view of the color change while addition of different anions as its tetrabutyl ammonium salt to the solution of 3in DMSO.

Figure S51: Evolution of UV-Vis spectra of 3 (20 μM) in DMSOupon gradual addition of TBAF (0 to 2.2 × 10-4 M).

Figure S52:Job’s plots for complexation of receptor 3with fluoride ([3] + [TBAF] = 40 μM).

Figure S53:Bensei-Hildebrand plot of 1/[A0-A] vs. 1/[TBAF] from the titration data for 3.

Figure S54: Evolution of UV-Vis spectra of 3 (20 μM) in DMSOupon gradual addition of TBAOAc (0 to 6.3 × 10-4 M).

Figure S55:Job’s plots for complexation of receptor 3with acetate ([3] + [TBAOAc] = 40 μM).

Figure S56:Bensei-Hildebrand plot of 1/[A0-A] vs. 1/[TBAOAc] from the titration data for 3.

Figure S57: Evolution of UV-Vis spectra of 3 (20 μM) in DMSOupon gradual addition of TBAPh (0 to 1.3 × 10-3 M).

Figure S58:Job’s plots for complexation of receptor 3with phosphate ([3] + [TBAPh] = 40 μM).

Figure S59:Bensei-Hildebrand plot of 1/[A0-A] vs. 1/[TBAPh] from the titration data for 3.

Figure S60: Top left: Fluorescence spectra of 3 (1 μM)in DMSOin presence of different anions; top right: visual changes in the fluorescence of 3 upon addition of F-, H2PO4

-, CH3COO-; bottom left: changes in the fluorescence spectra of 3 (1 μM)upon gradual addition of TBAF (0 to 5 μM); bottom middle: changes in the fluorescence spectra of 3 (1 μM)upon gradual addition of TBAOAc (0 to 3.4 × 10-4 M); bottom right: changes in the fluorescence spectra of 3 (1 μM)upon gradual addition of TBAPh (0 to 4.2 × 10-4 M).

Figure S61: Changes in the 1H NMR spectra of 3 (5 mM)inDMSO-d6upon gradual addition of TBAF (0 to 22.5 mM).

Figure S62: Changes in the 1H NMR spectra of 3 (5 mM)inDMSO-d6upon gradual addition of TBAOAc (0 to 16 mM).

Figure S63: DFT optimized geometry of the two plausible tautomeric form of 1a (ΔE (Left-Right) = - 43.63 kj.mol-1).

Figure S64: DFT optimized geometry of the two plausible tautomeric form of 1b (ΔE (Left-Right) = - 22.24 kj.mol-1).

Figure S65: DFT optimized geometry H-bonded complexes with fluoride ion Left: 1a; right: 1b.

Figure S66: DFT optimized geometry H-bonded complexes of 1b with acetate ion.

Figure S67: DFT optimized geometry H-bonded complexes of 1b with dihydrogenphosphate ion.

References:S1. 14 M. J. Frisch, G.W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery, Jr. J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V.N. Staroverov, T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski and D. J. Fox, Gaussian, Inc., Wallingford CT, 2010.

S2. S. P. Mahanta, B. S. Kumar and P. K. Panda, Org. Lett., 2012, 14, 548.

S3. J. L.Sessler, H. Maeda, T. Mizuno, V. M. Lynch and H.Furuta, J. Am. Chem. Soc.,2002, 124 , 13474.