A detailed (1)H-NMR study of the anion binding properties of the 2-iodo-imidazolium receptor 1 in DMSO allows to fully attribute the observed affinities to strong charge-assisted C-IX(-) halogen bonding (XB). Stronger binding was observed for oxoanions over halides. Phosphate, in particular, binds to 1 with an association constant of ca. 10(3) M(-1), which is particularly high for a single X-bond. A remarkably short C-IO(-) contact is observed in the structure of the salt 1·H(2)PO(4)(-)

G. Resnati

G. Terraneo

K. Raatikainen

M. Cametti

P. Metrangolo

T. Pilati

CAMETTI, MASSIMO

METRANGOLO, PIERANGELO

PILATI, TULLIO MARIA

TERRANEO, GIANCARLO

RESNATI, GIUSEPPE

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ELECTRONIC SUPPLEMENTARY  INFORMATION (ESI) 2-Iodo-Imidazolium Receptor Binds Oxoanions via Charge-Assisted Halogen Bonding Massimo Cametti,a Kari Raatikainen,a Pierangelo Metrangolo,a,b* Tullio Pilati,a Giancarlo Terraneo,a,b and Giuseppe Resnatia,b*  a NFMLab – Department of Chemistry, Materials, and Chemical Engineering ‘‘Giulio Natta’’, Politecnico di Milano, via Mancinelli 7, I-20131 Milan, Italy b Center for Nano Science and Technology@Polimi, Istituto Italiano di Tecnologia, via Pascoli 70/3, I-20133 Milano, Italy   Table of content:   Synthetic procedures         S1 NMR titration experiments with relative plots     S2-S8 List of references for XB in 2-halo-imidazolium systems    S9 Crystallographic data (tables, plots...)        S10-S17      Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S1  Synthetic procedures  General Commercial HPLC-grade solvents were used without further purification. Starting materials were purchased from Sigma–Aldrich and used without further purification. Reactions in solution were carried out in oven-dried glassware under a nitrogen atmosphere. 1H NMR and 13C NMR spectra were recorded at ambient temperature with a Bruker 400 MHz spectrometer. DMSO-d6 was used as both solvent and internal standard in 1H and 13C NMR spectra. All chemical shift values are given in ppm. The mass spectra were recorded on a GC-MS AGILENT GC-MSD5975. Differential Scanning Calorimetry (DSC) analysis was performed on a Mettler Toledo DSC823e instrument, aluminium light 20 μl sample pans and Mettler STARe software for calculation. Melting points were also determined with Reichert instrument by observing the melting process through an optical microscope. ATR-FTIR spectra were obtained with a Nicolet Nexus FTIR spectrometer. The values were given in wave numbers and were rounded to 1 cm-1 upon automatic assignment (s-strong, m-medium, w-weak, br-broad).  Synthesis of compound 1·I-: Compound 2·I- (0.200 g , 0.48 mmol) is added to 20 mL of MeCN at 25°C. 0.110 g (2eq) of potassium tert-butoxide is added. A significant change from light yellow to gray-green colour is noted. After 30 min, 0,250 g of iodine (2 eq.) is added and a brown-red precipitate is formed. During the operation the vessel is maintained under argon atmosphere. The solution is left under stirring for 12-18 h. The precipitate is filtered. Crystallization by slow evaporation produce single crystals of 1. Yield 58 %. 1H-NMR (400MHz, DMSO-d6):  8.876 (s, 1H),  8.22 (m, 4H),  7.79  (d, 1H, J=2 Hz),  7.65 (m, 4H),  6.76 (d, 1H, J=2 Hz),  6.28 (s, 2H),  4.258 (q, 2H),  1.42 (t, 3H);  13C-NMR (100 MHz, DMSO-d6):  131.5, 130.8, 129.9, 128.3, 126.0, 124.9, 124.1, 123.8, 122.8, 104.8, 48.8, 47.5, 15.4. ESI-Mass: m/z calcd for [C20H18IN2]+ : 413.05; found : 413.    Synthesis of compound 3·I-: Compound 2·I- (125 mg, 0.302 mmol) was added to a solution of N-bromosuccinimide (110 mg, 0.618 mmol) in acetonitrile (5 mL). The solution was stirred at ambient temperature for 12 h whereupon the solution was concentrated by solvent evaporation to a volume of ca. 2 mL, from which 3 crystallized out as orange prisms. Yield 98 mg (66 %). 1H-NMR (400MHz, CD3CN):  8.82 (s, 1H),  8.21 (d, 2H, J1= 8.3Hz),  8.14  (d, 2H, J=8.8 Hz),  7.62 (m, 4H),  7.35 (d, 1H, J=2.3),  6.57 (d, 1H, J=2.3 Hz),  6.20 (s, 2H),  4.24 (q, 2H),  1.48 (t, 3H); (400 MHz, DMSO-d6) =  8.89 (s, 1H),  8.25 (t, 4H),  7.79 (d, 1H, J=2),  7.64 (m, 4H),   6.80 (d, 1H, J=2 Hz),  6.28 (s, 2H),  4.24 (q, 2H),  1.41 (t, 3H); 13C-NMR (100 MHz, CD3CN):  132.6, 132.4, 130.7, 129.2, 129.1, 126.8, 126.7, 124.4, 123.9, 123.8, 121.3, 48.1, 47.2, 14.6. ESI-Mass: m/z calcd for [C20H18BrN2]+ : 365.07, 367.06; found : 365, 367.  Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S2  (TBA)Br conc., M0.00 0.01 0.02 0.03 0.04 0.05 0.06, ppm6.656.706.756.807.707.757.80NMR titration experiments Typical NMR titration experimental procedure: Solution of Receptor 1·I-, 2·I-, and 3·I- in DMSO-d6, (concentration in the range 0.0075-0.010 M) were prepared. 0.6 ml of fresh receptor solution was placed in the NMR tube. Addition of small volumetric (1-2 L) aliquots of concentrated solution of the (TBA)X salts were then added via Hamilton syringe. All spectra were recorder on Bruker 400 and 500 MHz at 300 K. Relaxation delay = 5 sec; SW= 12 ppm; LB = 1 Hz; NS= 32. RG is adjusted at high TBA salt concentration.                 Figure 1S. 1H-NMR titration plot for receptor 1·I- (0.010 M solution in DMSO-d6 ) with (TBA)Br at 300 K. Best fitting curves are shown as full lines. (data: full circle = H4; empty circle = H5)     Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S3  (TBA)I conc., M0.00 0.01 0.02 0.03 0.04 0.05 0.06, ppm6.706.756.806.857.757.807.85(TBA)I conc., M0.00 0.01 0.02 0.03 0.04, ppm6.76.87.77.8                    Figure 2S. 1H-NMR titration plot for receptor 1·I- (0.010 M solution in DMSO-d6 ) with (TBA)I at 300 K. a) the initial concentration of iodide is considered explicitly; b) the initial concentration of iodide anion is not considered explicitly. Best fitting curves are shown as full lines. (data: full circle = H4; empty circle = H5). Best fit parameters (K, ∞ and extrapolated  at [I-] = 0 are also shown on the right side of the plot.    a) b) Parameter     Value StdErr CV(%) Dependencies ∞ H4 -7.418e-2  4.697e-3  6.332e+0  0.9365273 ∞ H5 -1.340e-1  6.820e-3  5.089e+0  0.9698927 H4 [I-]=0  7.811e+0  2.108e-3  2.698e-2  0.9514397 H5 [I-]=0  6.806e+0  3.251e-3  4.777e-2  0.9795941 K  3.887e+1  7.843e+0  2.017e+1  0.9939726 Parameter     Value StdErr CV(%) Dependencies ∞ H4 -5.751e-2  3.517e-3  6.117e+0  0.7931977 ∞ H5 -1.039e-1  5.883e-3  5.661e+0  0.9260622 K  3.442e+1  3.455e+0  1.004e+1  0.9423977 Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S4  (TBA)OAc conc., M0.00 0.01 0.02 0.03, ppm 6.656.706.756.807.707.757.80             Figure 3S. 1H-NMR titration plot for receptor 1·I- (0.010 M solution in DMSO-d6 ) with (TBA)AcO at 300 K. Best fitting curves are shown as full lines. (data: full circle = H4; empty circle = H5).            Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S5  (TBA)Cl conc., M0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07, ppm7.757.808.909.009.10             Figure 4S. 1H-NMR titration plot for receptor 2·I- (0.010 M solution in DMSO-d6 ) with (TBA)Cl at 300 K. Best fitting curves are shown as full lines. (data: full circle = H2; empty circle = H4).            Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S6  (TBA)OAc conc., M0.00 0.01 0.02 0.03 0.04, ppm7.67.89.09.29.4            Figure 5S. 1H-NMR titration plot for receptor 2·I- (0.010 M solution in DMSO-d6 ) with (TBA)OAc at 300 K. Best fitting curves are shown as lines. (data: full circle = H2; empty circle = H4; triangle =H5).             Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S7  (TBA)H2PO4 conc., M0.000 0.005 0.010 0.015 0.020 0.025 0.030 ppm7.507.758.759.009.259.50             Figure 6S. 1H-NMR titration plot for receptor 2·I- (0.010 M solution in DMSO-d6 ) with (TBA)H2PO4 at 300 K. Best fitting curves are shown as lines. (data: full circle = H2; empty circle = H4; triangles = H5)            Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S8  (TBA)Cl conc., M0.00 0.01 0.02 0.03 0.04 0.05H4, ppm 7.707.727.747.767.787.807.827.84(TBA)Cl conc., M0.00 0.01 0.02 0.03 0.04 0.05H5, ppm6.626.646.666.686.706.726.746.766.786.806.82(TBA)Cl conc., M0.00 0.01 0.02 0.03 0.04 0.05 0.06, ppm 6.7906.7956.8006.8057.7807.8007.8207.840                   Figure 7S. a) 1H-NMR titration plot for receptor 3·I- (0.010 M solution in DMSO-d6 ) with (TBA)Cl at 300 K. Best fitting curves are shown as full lines. (data: full circle = H4; empty circle = H5); b) Comparison between the chemical shift changes of 1 (full circles) and 3 (empty circle)  upon addition of (TBA)Cl in DMSO at 300K (1H-NMR, 400MHz).  As far as the Cl- binding properties with respect to 1 is concerned, 3 displays an association constant of approximately two order of magnitude less. The precision of the data is limited due to the small shift observed. Most importantly, given the downfield shift variation of H4 (figure which compares well with that of 2H in 2), the small associative forces responsible for the feeble binding most probably is H- bonding with the H4.    a) b) Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S9  List of references for XB in 2-halo-imidazolium systems  a) N. Kuhn, T. Kratz, G. Henkel, Chem. Commun. 1993, 1778; b) E. Fooladi, B. Dalhus, M. Tilset Dalton Trans. 2004, 3909; c) N. Kuhn, A. Abu-Rayyan, K. Eichele, S. Schwarz, M. Steimann Inorg. Chim. Acta 2004, 357, 1799; d) G. Laus, A. Schwarzler, P. Schuster, G. Bentivoglio, M. Hummel, K. Wurst, V. Kahlenberg, T. Lorting, J. Schutz, P. Peringer, G. Bonn, G. Nauer, H. Schottenberger, Z. Naturforsch., B: Chem. Sci. 2007, 62, 295; e) M. L. Cole, C. Jones, P. C. Junk, New J. Chem. 2002, 26, 1296; f) N. Kuhn, M. Richter, M. Steimann, M. Strobele, K. Sweidan, Z. Anorg. Allg. Chem. 2004, 630, 2054; g) N. Kuhn, J. Fahl, R. Fawzi, C. Maichle-Mossmer, M. Steimann, Z. Naturforsch., B: Chem. Sci. 1998, 53, 720; h) A. J. Arduengo, F. Davidson, H. V. R. Dias, J. R. Goerlich, D. Khasnis, W. J. Marshall, T. K. Prakasha; J. Am. Chem. Soc. 1997, 119, 12742; i) N. Kuhn, A. Abu-Rayyan, M. Gohner, M. Steimann, Z. Anorg. Allg. Chem. 2002, 628, 1721; j) A. J. Arduengo III, M. Kline, J. C. Calabrese, F. Davidson, J. Am. Chem. Soc. 1991, 113, 9704; k) N. Kuhn, A. Al-Sheikh, S. Schwarz, M. Steimann Z. Naturforsch., B: Chem. Sci. 2004, 59, l) 129; N. Kuhn, A. Abu-Rayyan, M. Strobele Z. Anorg. Allg. Chem. 2002, 628, 2251.           Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S10  Crystallographic data  Single crystal data collection, structure solution and refinement. Data were collected on a Bruker KAPPA APEX II diffractometer with Mo-Kα radiation and CCD detector. The structures were solved by SIR20021 and refined by SHELXL-972 programs, respectively. The refinement was carried on by full-matrix least-squares on F2. Hydrogen atoms were placed using standard geometric models and with their thermal parameters riding on those of their parent atoms. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.  Table S1. Single crystal data collection, structure solution and refinement. Structure 1·I- 1·Cl- 1·Br- 2·Cl- 1· H2PO4- Chemical formula (moiety) C20H18N2I+·I- C20H18N2I+·Cl-,  H2O  C20H18N2I+·Br-, CHCl3  C20H19N2+·Cl-,  H2O  C20H18N2I+·H2PO4-, C3H7NO  Chemical formula (total) C20H18I2N2 C20H20ClIN2O C21H19BrCl3IN2 C20H21ClN2O C23H27IN3O5P Formula weight 540.16 466.73 612.54 340.84 583.35 Temperature [K] 103(2) 103(2) 296(2) 90(2) 90(2) Radiation, wavelength [Å] MoKα, 0.71073 MoKα, 0.71073 MoKα, 0.71073 MoKα, 0.71073 MoKα, 0.71073 Crystal system,  space group Monoclinic, P 21/c Monoclinic, P 21/c Monoclinic, P 21/c Monoclinic, P 21/c Monoclinic, P 21/c a [Å] 8.2333(4) 12.3454(12) 7.0749(6) 9.7188(5) 16.8192(13) b [Å] 10.2275(6) 10.2075(10) 12.5777(15) 19.4850(5) 16.3863(13) c [Å] 21.9756(12) 15.1939(15) 26.548(3) 9.1908(5) 8.5845(6) [º] 90.00 90.00 90.00 90.00 90.00 [º] 92.507(2) 91.473(10) 90.531(12) 95.994(5) 90.086(3) [º] 90.00 90.00 90.00 90.00 90.00 Cell volume [Å3] 1848.71(17) 1914.0(3) 2362.3(4) 1201.1(3) 2365.9(3)                                                              1 M.C. Burla, M. Camalli, B. Carrozzini, G.L. Cascarano, C. Giacovazzo, G. Polidori, R. Spagna. SIR2002: J. Appl. Cryst. 2003, 36, 1103. 2 Sheldrick, G. M. Acta Cryst. A 2008, 64, 112-122. Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S11  calc [g cm-3] 1.941 1.620 1.722 1.308 1.638 Z 4 4 4 4 4 dimension [mm3] 0.05 x 0.16 x 0.36 0.08 x 0.14 x 0.20 0.15 x 0.26 x 0.42 0.02 x 0.12 x 0.20 0.02 x 0.05 x 0.35 μ(MoKα) [mm-1] 3.406 1.823 3.396 0.229 1.461 Tmin, Tmax 0.6092, 0.7468 0.6581, 0.7057 0.2463, 0.3171 0.66, 0.746 0.905, 1 F(000) 1032 928 1192 720 1176 Crystal colour and shape Brown Elongated Table Brown Block Yellow Block  Colourless Plate Colourless Needle θmax [°] 34.49 34.36 33.48 28.76 27.5 Data collected 55642 31778 23152 13942 29610 Unique data 6886 6582 6948 4394 29610 Rint 0.0267 0.0281 0.0203 0.078 0.0388 No. obs. data Io>2σ(Io)] 6520 5842 5282 2517 22598 no. parameters 219 306 254 230 204 No. Restrains. 0 21 0 2 175 Rall 0.0561 0.0277 0.0530 0.1043 0.0896 Robs 0.0532 0.0237 0.0354 0.042 0.0617 wRall 0.1482 0.0710 0.0989 0.0901 0.1559 wRobs 0.1467 0.0692 0.0904 0.0781 0.1398 Goodness-of-fit on F2 1.316 1.075 1.049 0.913 1.02 Δρmin,max [e Å-3] -2.434; 3.775 -0.577; 1.224 -1.157, 1.016 -0.255, 0.055 -2.143, 3.375 CCDC 828713 828715 828714 828716 828717  Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S12   Table S2. Halogen bonding and hydrogen bonding distances and angles in halide and phosphate salts of 1 and 2. Co-crystal name XB C-donor(D)...acceptor(A) Distance  D...A (Å) Angle C-D...A (deg) 1·I- C16-I2∙∙∙I1 3.2828(6) 171.93(18) 1·Cl- C1-I1∙∙∙Cl1a 3.0233(5) 174.14(10) 1·Br- C16-I1∙∙∙Br2b 3.0994(5) 178.46(13) 2·Cl- C1-H1∙∙∙Cl1 2.643(21) 158.89(10) 1· H2PO4- C2-I1∙∙∙ O3c 2.6024(23) 177.84(17) a: 1-x, -0.5+y, 1.5-z; b: -x, -0.5+y, 0.5-z; c: 1-x, -0.5+y, 0.5-z Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S13           Figure 8S. Halogen bonding and hydrogen bonding geometrical parameters for 1·I-: distance [I1...H17 x, 1+y, z)]: 3.051(3) Å.  Colour code: carbon: gray; nitrogen: blue; iodine: purple; and hydrogen: white. Interactions are highlighted as black dotted line.    Figure 9S. Halogen bonding, hydrogen bonding and other non covalent interactions geometrical parameters for 1·Cl-:  distance [H1A...Cl1(-x+1, -y+1, -z+1)]: 2.392(4) Å and [H1B...Cl1(x, y+1, z)]: 2.413(3) Å; angle  [O1-H1A...Cl1]: 169.91° and [O1-H1B...Cl1]: 168.64°, distance [C1...Cl1]: 3.4186(16) Å; distance [Cl1...H2(1-x, -0.5+y, 1.5-z)]: 2.7804(228) Å.  Colour code: carbon: gray; nitrogen: blue; oxygen: red; iodine: purple; chlorine: green and hydrogen: white. Interactions are highlighted as black dotted line.  Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S14    Figure 10S. Halogen bonding and hydrogen bonding interaction geometrical parameters for 1·Br-:  distance [H21...Br2(-1-x, -0.5+y, 0.5-z)]: 2.726(4) Å and [H12(-x,0.5+y, 0.5-z)...Br2(-1-x, -0.5+y, 0.5-z)]: 2.413(2) Å; angle [C-H21...Br2(-1-x, -0.5+y, 0.5-z)]: 170.47° and [C-H12(-1-x, -0.5+y, 0.5-z)...Br2(-1-x, -0.5+y, 0.5-z)]: 165.45°. Colour code: carbon: gray; nitrogen: blue; iodine: purple; chlorine: green; bromine: light brown and hydrogen: white. Interactions are highlighted as black dotted line.          Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S15  X-ray structure of 2·Cl-. X-ray study revealed same rectangular shaped HB pattern between two water molecules and chloride anion observed in 5, while the hydrogen atom 2H on imidazolium ring was found hydrogen bonded to chloride atom (see Figure S12). Further weak hydrogen bonds, mainly due to the crystal packing requirements, complete the coordination sphere of the Cl-.    Figure 11S. Hydrogen bonding geometrical parameters for 6. Left: distance [H1A...Cl1]: 2.366(20) Å and [H1B...Cl1]: 2.370(20) Å; angle [O1-H1A...Cl1]: 169.28(20)° and [O1-H1B...Cl1]: 174.03(20)°. Right: [H5...Cl1]: 2.635(5) Å, [H8A...Cl1]: 2.725(4) Å, [H8B...Cl1]: 2.857(5) Å.  Colour code: carbon: gray; nitrogen: blue; oxygen: red; chlorine: green and hydrogen: white. Interactions are highlighted as black dotted line.          Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S16             Figure 12S. Halogen bonding and hydrogen bonding interactions geometrical parameters for 1·H2PO4- distance [H4...O6(x, -y+0.5, z+0.5)]: 1.726(3) Å and [H5...O3(x, -y+0.5, z-0.5)]: 1.784(4) Å; angle [O4-H4...O6(x, -y+0.5, z+0.5)]: 164.87(4)° and [O5-H5...O3(x, -y+0.5, z-0.5)]: 164.22(3)°. Colour code: carbon: gray; nitrogen: blue; iodine: purple; oxygen: red; phosphorous: light brown and hydrogen: white. Interactions are highlighted as black dotted line. DMF molecule is omitted for clarity. Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011S17            Figure 13S. Hydrogen bonding and other non covalent interactions geometrical parameters for DMF molecule in 1·H2PO4-. Distance [H3A...O6]: 2.515(3) Å, [H4A1...O6]: 2.568(3) Å, [H5A3...O6]: 2.561(3) Å, [O1A...H12]: 2.678(3) Å and [O1A...C2]: 3.143(7) Å;  angle [C3A-H3A...O6]: 164.2(3)°,  [C4A-H4A1...O6]: 155.3(4)°,  [C5A-H5A3...O6]: 155.3(4)° and  [C12-H12...O1A]: 123.4(2). Colour code: carbon: gray; nitrogen: blue; iodine: purple; oxygen: red; phosphorous: light brown and hydrogen: white. Interactions are highlighted as black dotted line. Electronic Supplementary Material (ESI) for Organic & Biomolecular ChemistryThis journal is © The Royal Society of Chemistry 2011

2-Iodo-imidazolium receptor binds oxoanions via charge-assisted halogen bonding.

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2-Iodo-imidazolium receptor binds oxoanions via charge-assisted halogen bonding.

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