313Acta Chim. Slov. 2025, 72, 313–320 Pevec et al.: Structural Diversity of Different Aminomethylpyridinium ... DOI: 10.17344/acsi.2025.9194 Scientific paper Structural Diversity of Different Aminomethylpyridinium Hexafluoridosilicates Andrej Pevec Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia * Corresponding author: E-mail: andrej.pevec@fkkt.uni-lj.si Received: 02-07-2025 Abstract A series of new aminomethylpyridinium hexafluoridosilicate salts with the formula (RH)2[SiF6] (where R = 2-ami- no-3-methylpyridine (1), 2-amino-4-methylpyridine (2), 2-amino-5-methylpyridine (3) and 2-amino-6-methylpyridine (4)) were prepared by the reaction of various methyl-substituted 2-aminopyridines with hydrogen fluoride solution of silica. The crystal packing of these ionic salts is compared with respect to the position of the methyl group on the aro- matic ring. The crystal structures are dominated by the non-covalent interactions: the N–H···F hydrogen bonds and π-π interactions between aromatic rings. The potential of the corresponding ionic salts to enable supramolecular associations was investigated. Compounds 1–4 were also characterized by 1H, 19F NMR and IR spectroscopy. Keywords: hexafluoridosilicate, hydrogen bond, X-ray crystal structure, aminomethylpyridine, π-π interaction 1. Introduction Supramolecular chemistry is concerned with the re- search and utilization of non-covalent bonding forces. The interaction between charges is a well-known type of non-covalent interaction in common salts consisting of metal cations and halide anions. When an organic mole- cule plays the role of the cation and the anion is a polya- tomic species, the formation of ion pairs can be directional and not just involve interactions between spherical ions.1 In such systems, the mutual interaction of the reac- tion partners is controlled by non-covalent interactions. These interactions mainly include hydrogen bonds and π–π interactions between aromatic rings. It is known from crystallographic and ab initio studies that the hydrogen bonding of the pyridine nitrogen significantly influences the pyridine stacking interactions.2 The electrostatic attractive forces in ionic com- pounds with the formula (pyH)2[SiF6] between the cations of the protonated pyridines and the hexafluoridosilicate anions [SiF6]2– enable the formation of extensive N–H···F hydrogen bonds and π–π interactions. The overview of the crystal structures archived in the CSD (release November 2024, version 5.32)3 shows several hits for ionic com- pounds with the formula (RH)2[SiF6], where R stands for pyridine or pyridine- related compounds.4–9 Ionic hex- afluoridosilicates with methyl10, amino11,12, carboxy13,14, carboxymethyl15, hydroxymethyl16,17 and nicotinamide18 substituents on the pyridine ring are well documented in the literature. In some of them, pyridine is substituted with several substituents, one of which is a methyl group.19 Some pyridinium hexafluoridosilicates can be used as po- tential caries of prophylactic agents.20 In the present study, the crystal structures of hex- afluoridosilicates with methyl-substituted 2-aminopyrid- inium cations (Scheme 1) were determined and structur- ally compared. This was accompanied with the investigation of non-covalent interactions in these sys- Scheme 1. 314 Acta Chim. Slov. 2025, 72, 313–320 Pevec et al.: Structural Diversity of Different Aminomethylpyridinium ... tems to gain further insight into the effects of small struc- tural variations in closely related cations on crystal pack- ing. Two effects appear to be crucial for crystal packing: the N–H···F hydrogen bonding interactions between the charged species and the π–π stacking between the cation- ic units. Spectral data (NMR and IR) were also obtained for compounds 1–4. 2. Experimental General Experimental Procedures. The chemicals were used as purchased: HF (BDH Chemicals and Aris- tar), SiO2 (Carl Roth), aminomethylpyridines (Fluka). El- emental analyses (C, H, N) were performed using a Per- kin-Elmer 2400 Series II CHNS/O analyzer. NMR spectra were measured with a Bruker Avance III 500 spectrometer at 500 MHz (1H) and 471 MHz (19F). The chemical shifts are given on the δ scale (ppm). Infrared spectra (Nujol mull or solid sample support in Specac Golden Gate Dia- mond ATR) were recorded with a Perkin-Elmer Spectrum 100 FT-IR spectrometer. General Synthesis. Silicon dioxide (1.00 g; 16.6 mmol) was slowly added to a plastic beaker containing hy- drofluoric acid (20 mL, 48%) while stirring. After clarifica- tion of the solution aminometylpyridine (3.61 g, 33.3 mmol) was added slowly. The mixture was stirred for 2 hours and then filtered. After filtration, the solvent was slowly evaporated from the beaker to yield a colorless crys- talline product after a few days. The crystals were filtered from the mother liquor and dried in air. Bis(2-amino-3-methylpyridinium) hexafluoridosilicate (1). Yield 1.34 g, 22%. Anal. Calcd for C12H18F6N4Si: C, 39.99; H, 5.03; N, 15.55. Found: C, 39.71; H, 5.06; N, 15.47. 1H NMR (500 MHz, D2O) δ 7.76 (d, 1H, ArH), 7.67 (d, 1H, ArH), 6.84 (t, 1H, ArH), 2.20 (s, 3H, CH3) ppm. 19F NMR (471 MHz, D2O) δ –129.88 (s, SiF6) ppm. IR (Nujol) (cm–1): 3408, 3337, 3212, 3106 [ν(N+H), ν(NH2)], 1665, 1624, 1573 [δ(NH2)], 724 [ν(SiF)], 474, 452 [δ(SiF2)]. Bis(2-amino-4-methylpyridinium) hexafluoridosilicate (2). Yield 0.60 g, 10%. Anal. Calcd for C12H18F6N4Si: C, 39.99; H, 5.03; N, 15.55. Found: C, 39.93; H, 4.98; N, 15.55. 1H NMR (500 MHz, D2O) δ 7.63 (d, 1H, ArH), 6.79 (s, 1H, ArH), 6.75 (d, 1H, ArH), 2.35 (s, 3H, CH3) ppm. 19F NMR (471 MHz, D2O) δ –129.97 (s, SiF6) ppm. IR (Nujol) (cm–1): 3407, 3356, 3231, 3108 [ν(N+H), ν(NH2)], 1674, 1636 [δ(NH2)], 723 [ν(SiF)], 474, 452 [δ(SiF2)]. Bis(2-amino-5-methylpyridinium) hexafluoridosilicate (3). Yield 0.67 g, 11%. Anal. Calcd for C12H18F6N4Si: C, 39.99; H, 5.03; N, 15.55. Found: C, 40.10; H, 5.24; N, 15.72. 1H NMR (500 MHz, D2O) δ 7.77 (d, 1H, ArH), 7.57 (s, 1H, ArH), 6.92 (d, 1H, ArH), 2.19 (s, 3H, CH3) ppm. 19F NMR Table 1. Crystal data and structure refinement details for 1–4. 1 2 3 4 formula C12H18F6N4Si C12H18F6N4Si C12H18F6N4Si C12H18F6N4Si Fw (g mol–1) 360.39 360.39 360.39 360.39 crystal size (mm) 0.20 × 0.10 × 0.08 0.20 × 0.10 × 0.05 0.25 × 0.15 × 0.08 0.50 × 0.25 × 0.25 crystal color colourless colourless colourless colorless crystal system orthorhombic monoclinic monoclinic monoclinic space group P b c n C 2/c P 21/c C c a (Å) 14.4210(5) 8.728(5) 6.6383(2) 20.6043(4) b (Å) 7.4652(2) 12.658(5) 12.6481(5) 20.6970(4) c (Å) 13.9865(5) 14.892(5) 9.3048(3) 15.5669(3) β (º) 90 97.073(5) 99.129(2) 109.4270(10) V (Å3) 1505.73(9) 1632.7(13) 771.35(5) 6260.5(2) Z 4 4 2 16 F(000) 744 744 372 2976 no. of collected reflns 3177 3305 3432 13644 no. of independent reflns 1721 1728 1759 13636 Rint 0.0178 0.0264 0.0207 0.0118 no. of reflns observed 1292 1203 1377 8149 no. of parameters 116 117 116 910 R[I > 2σ (I)]a 0.0415 0.0451 0.0349 0.0477 wR2 (all data)b 0.1232 0.1225 0.0923 0.1164 Goof , Sc 1.038 1.054 1.045 1.036 Largest diff. peak/hole (e Å–3) +0.30/–0.33 +0.25/–0.21 +0.17/–0.26 +0.23/–0.23 a R = ∑||Fo| – |Fc||/∑|Fo|. b wR2 = {∑[w(Fo2 – Fc2)2]/∑[w(Fo2)2]}1/2. c S = {∑[w(Fo2 – Fc2)2]/(n–p)}1/2 where n is the number of reflections and p is the total number of parameters refined. 315Acta Chim. Slov. 2025, 72, 313–320 Pevec et al.: Structural Diversity of Different Aminomethylpyridinium ... (471 MHz, D2O) δ –129.93 (s, SiF6) ppm. IR (Nujol) (cm–1): 3355, 3198 [ν(N+H), ν(NH2)], 1674, 1629, 1559 [δ(NH2)], 722 [ν(SiF)], 469, 439 [δ(SiF2)]. Bis(2-amino-6-methylpyridinium) hexafluoridosilicate (4). Yield 1.41 g, 23%. Anal. Calcd for C12H18F6N4Si: C, 39.99; H, 5.03; N, 15.55. Found: C, 40.09; H, 5.15; N, 15.61. 1H NMR (500 MHz, D2O) δ 7.76 (t, 1H, ArH), 6.78 (d, 1H, ArH), 6.69 (d, 1H, ArH), 2.43 (s, 3H, CH3) ppm. 19F NMR (471 MHz, D2O) δ –129.77 (s, SiF6) ppm. IR (Nujol) (cm–1): 3397, 3363, 3227 [ν(N+H), ν(NH2)], 1680, 1637, [δ(NH2)], 750 [ν(SiF)], 475, 464 [δ(SiF2)]. X-ray Crystallography. The crystal data and refine- ment parameters of compounds 1–4 are listed in Table 1. X-ray intensity data were collected using a Nonius Kappa CCD diffractometer equipped with graphite‒monochro- mated MoKα radiation (λ = 0.71073 Å) at room tempera- ture. The data were processed using DENZO.21 The struc- tures were solved by direct methods using SHELXT22 and refined against F2 on all data by a full‒matrix least-squares procedure with SHELXL.23 All non‒hydrogen atoms were refined anisotropically. All hydrogen atoms bonded to car- bon were included in the model at geometrically calculat- ed positions and refined using a riding model. The hydro- gen atoms bound to nitrogen were localized in the difference map and refined with the distance restraints (DFIX) with N‒H = 0.86 and with Uiso(H) = 1.2Ueq(N). Compound 4 crystallizes in the non-centrosymmetric space group Cc. The value of the Flack parameter 0.44(5) indicates possible racemic twinning. 3. Results and Discussion The preparation of methy-substituted aminopyridin- ium hexafluoridosilicates were carried out in a simple manner by reacting the corresponding pyridine with sili- con dioxide in hydrofluoric acid. Hydrofluoric acid serves simultaneously as reagent and solvent in these reactions. The molar ratios between SiO2 and the corresponding methylaminopyridine were 1:2 in all cases (Scheme 2). In all cases, colorless crystalline products were obtained by slow evaporation of the solvent at room temperature. The crystal structures of these compounds consist of me- thyl-substituted 2-aminopyridinium cations and hex- afuoridosilicate anions. Selected bond lengths and angles for all compounds 1–4 are listed in Table 2. The Si–F dis- tances in the [SiF6]2– anions of compounds 1–4 are be- tween 1.65 and 1.69 Å, and the bond angles within the anions are close to 90° and 180°. Such an undistorted octa- hedral geometry is also found in some other ionic com- pounds with [SiF6]2– anion and heterocyclic nitrogen cati- on, e. g. pyrimidinium hexafluoridosilicates.24 The characteristic hydrogen bonds observed in 1–4 are listed in Table 3. These components are bound by a net- work of charge-assisted N–H···F hydrogen bonds. The pro- tonated nitrogen on the pyridine ring and the amino group are potential donors of one and two hydrogen bonds, re- spectively. All six fluorine atoms in hexafuoridosilicate an- ions are capable of accepting hydrogen bonds. 2-Aminopyridinium hexafluorosilicate has already been synthesized and crystallographically character- ized.11 When investigating the crystal structures with an additional methyl substituent on the pyridine rings, we can use the influence of the interionic hydrogen bonds on the structure as a model. We expected a different crystalline architecture due to supramolecular interac- tions in the structure of the corresponding hexafluori- dosilicate. Table 2. Selected bond lengths (Å) and angles (°) of compounds 1–4.a 1 Si1–F1 1.6934(10) F1–Si1–F2 89.19(5) Si1–F2 1.6856(11) F1–Si1–F3 90.22(5) Si1–F3 1.6773(11) F2–Si1–F3 179.02(6) 2 Si1–F1 1.6937(12) F1–Si1–F2 89.64(5) Si1–F2 1.6835(19) F1–Si1–F3 89.26(6) Si1–F3 1.6581(16) F1–Si1–F4 90.36(5) Si1–F4 1.6781(19) F2–Si1–F3 89.40(6) 3 Si1–F1 1.6927(9) F1–Si1–F2 90.03(5) Si1–F2 1.6774(9 F1–Si1–F3 90.60(5) Si1–F3 1.6778(9) F1–Si1–F1i 180.00(7) 4 Si1–F1 1.678(3) F1–Si1–F2 90.26(16) Si1–F2 1.683(3) F1–Si1–F3 179.4(2) Si1–F3 1.686(3) F1–Si1–F4 89.81(16) Si1–F4 1.684(3) F1–Si1–F5 90.39(19) Si1–F5 1.646(3) F1–Si1–F6 89.7(2) Si1–F6 1.658(3) F2–Si1–F4 179.14(19) a Symmetry transformation used to generate equivalent atoms: (i) –x+2, –y+1, –z+1. X-ray analysis of compound 1. Compound 1 with 2-amino-3-methypyridinium cation crystallizes in the or- thorhombic space group Pbcn (Figure 1). The asymmetric unit consists of one half of the [SiF6]2– anion which is lo- cated on a 2-fold rotation axis and one of 2-amino-3-meth- ylpyridinium cation. All fluorine atoms of each [SiF6]2– Scheme 2. 316 Acta Chim. Slov. 2025, 72, 313–320 Pevec et al.: Structural Diversity of Different Aminomethylpyridinium ... anion are involved in N–H···F hydrogen bonding. The protonated heterocyclic nitrogen atom, together with the amino nitrogen and one of the amino hydrogen atoms, forms eight-membered rings (N–C–N–H···F–Si–F···H) with two fluorine ligands from [SiF6]2– octahedron. This can be designated by the graph-set25 notation R22(8). Four fluorine ligands from each [SiF6]2– octahedron are in- volved in two eight-membered ring formations. The sec- ond hydrogen atom of the amino group is involved in N–H···F hydrogen bonding interactions, with the graph- set motif R88(24), where four [C6H9N2]2[SiF6] synthons linked to form a 24-membered ring, resulting in a two-di- mensional layer perpendicular to the c-axis of the crystal structure. The layer is stabilized by non-covalent π–π in- teractions with the centroid-to-centroid separation dis- tance of 3.741 Å (Table S1). X-ray analysis of compound 2. Changing the po- sition of the methyl group on the aromatic ring leads to drastic changes of hydrogen bonding interactions and crystal structure in compounds with hexafluoridosili- cate anion. Compound 2 crystallizes in the monoclinic space group C2/c, in which one silicon and two fluorine atoms of the [SiF6]2– anion are located in a special posi- tion of the 2-fold rotation axis. The protonated pyridine nitrogen atom and one of the amino hydrogen atoms are involved in N–H···F hydrogen-bonding interactions Table 3. Hydrogen bonding geometry for 1, 2, 3 and 4. D – H ··· A d(D – H)/ Å d(H ··· A)/ Å d(D ··· A)/ Å <(DHA)/ º Symmetry transformation for acceptors 1 N1–H1N∙∙∙F1 0.902(14) 1.851(15) 2.7231(16) 162.2(17) N2–H2E∙∙∙F2 0.867(15) 1.996(16) 2.8477(19) 167(2) N2–H2D∙∙∙F3 0.858(16) 2.211(17) 3.0172(19) 156.4(19) x–1/2, y–1/2, –z+3/2 2 N1–H1N∙∙∙F1 0.871(16) 1.894(17) 2.750(2) 167(2) N2–H2D∙∙∙F2 0.891(18) 2.14(2) 2.925(3) 146(3) N2–H2D∙∙∙F3 0.891(18) 2.31(2) 3.085(3) 145(3) N2–H2E∙∙∙F4 0.865(18) 1.97(2) 2.816(3) 166(3) x–1/2, y+1/2, z 3 N1–H1N∙∙∙F1 0.857(15) 1.892(15) 2.7452(16) 173.9(18) N2–H2D∙∙∙F2 0.879(15) 1.952(16) 2.8296(18) 177(2) N2–H2E∙∙∙F3 0.882(15) 1.985(15) 2.8576(17) 170(2) 4 N1–H1N∙∙∙F1 0.85(3) 1.90(3) 2.748(5) 171(5) N2–H2D∙∙∙F2 0.87(3) 2.06(4) 2.874(6) 154(6) N2–H2E∙∙∙F23 0.88(3) 2.02(3) 2.868(6) 163(6) x–1/2, y+1/2, z N3–H3N∙∙∙F3 0.88(3) 1.87(3) 2.740(5) 169(5) N4–H4D∙∙∙F4 0.87(3) 2.11(4) 2.875(6) 147(6) N4–H4E∙∙∙F11 0.88(3) 2.03(3) 2.861(5) 158(6) x–1/2, y+1/2, z N5–H5N∙∙∙F7 0.86(3) 1.91(3) 2.754(5) 168(5) N6–H6D∙∙∙F8 0.87(3) 2.21(4) 2.985(6) 149(6) N6–H6E∙∙∙F17 0.86(3) 1.98(3) 2.829(5) 171(6) N7–H7N∙∙∙F9 0.88(3) 1.87(3) 2.749(5) 174(5) N8–H8D∙∙∙F10 0.87(3) 2.21(3) 3.050(6) 160(6) N8–H8E∙∙∙F2 0.86(3) 1.96(3) 2.815(6) 171(6) N9–H9N∙∙∙F13 0.91(3) 1.85(3) 2.734(5) 166(4) N10–H10D∙∙∙F14 0.89(3) 2.38(3) 3.231(6) 161(5) N10–H10E∙∙∙F10 0.85(3) 2.11(3) 2.911(6) 158(6) x–1/2, y–1/2, z N11–H11N∙∙∙F15 0.89(3) 1.85(3) 2.729(5) 172(5) N12–H12D∙∙∙F18 0.87(3) 2.11(4) 2.896(6) 150(6) N12–H12E∙∙∙F20 0.88(3) 2.05(3) 2.911(6) 166(6) x–1/2, y+1/2, z N13–H13N∙∙∙F19 0.87(3) 1.87(3) 2.736(5) 175(5) N14–H14D∙∙∙F20 0.84(3) 2.28(3) 3.075(6) 158(6) N14–H14E∙∙∙F4 0.85(3) 1.97(3) 2.811(5) 173(6) x, y–1, z N15–H15N∙∙∙F21 0.85(3) 1.95(3) 2.777(5) 165(5) N16–H16D∙∙∙F22 0.87(3) 2.19(4) 2.984(6) 151(6) N16–H16E∙∙∙F17 0.84(3) 1.99(3) 2.833(5) 174(6) 317Acta Chim. Slov. 2025, 72, 313–320 Pevec et al.: Structural Diversity of Different Aminomethylpyridinium ... with three fluorine acceptors of the [SiF6]2– anion in the fac position (Figure 2). The nitrogen atom of the amino group is the donor of one bifurcated N–H···F hydrogen bond and one N–H···F hydrogen bond to the neighbor- ing [SiF6]2– anion, thus forming 20-membered rings [represented by graph-set notation R86(20)] and a 2D layer perpendicular to the c-axes. These layers are packed into a supramolecular 3D architecture by the as- sistance of non-covalent π–π interactions between the aromatic rings with two different centroid-to-centroid separation distances of 3.797 and 3.892 Å (Figure 3 and Table S1). X-ray analysis of compound 3. Compound 3 crys- tallizes in the monoclinic P21/c space group. The forma- tion of an eight-membered N–C–N–H···F–Si–F···H ring between one cation and one anion as well as 24-membered ring between four cations and four anions with the graph- set notations of R22(8) and R88(24) is reminiscent of the crystal structure of compound 1 (Figure 4). However, the N–H···F interactions of the 2-amino-5-methylpyridinium cations according to [SiF6]2– anion in 3 are in the trans po- sition. These hydrogen-bonding interactions lead to a two-dimensional zigzag layered network extending along the bc plane. The shortest distance between two aromatic rings is 4.863 Å and is too long for the interaction.26 Figure 1. Crystal structure of 1 showing the atom numbering scheme, the N–H···F hydrogen bonding interactions between cations and anions and the π–π stacking between pyridine rings. Figure 2. Layer formation in 2 by N–H···F hydrogen bonds. The hydrogen atoms on the aromatic rings and the methyl group have been removed for clarity. Figure 3. Fragment of crystal packing of 2 with π–π stacking be- tween pyridine rings. The hydrogen atoms on the aromatic rings and the methyl groups have been removed for clarity. 318 Acta Chim. Slov. 2025, 72, 313–320 Pevec et al.: Structural Diversity of Different Aminomethylpyridinium ... X-ray analysis of compound 4. Compound 4 crys- tallizes in the non-centrosymmetric space group Cc with four crystallographically different (C6H9N2)2[SiF6] formu- la units (Figure 5). Cations and anions are connected by intense N–H···F hydrogen bonds and π–π interactions forming 3D network. In all four crystallographically dif- ferent [SiF6]2– anions four fluorine atoms are acceptors of four N–H···F hydrogen bonds of two 2-amino-6-meth- ylpyridinium cations forming eight-membered N–C–N– H···F–Si–F···H rings with a graph-set motif R22(8). The amino group of the cations is responsible for the connec- tion of the (C6H9N2)2[SiF6] synthons. The arrangement of the 2-amino-6-methylpyridinium cations in an asymmet- ric unit suggests intense π–π interactions between the aro- matic rings in the range from 3.65 to 3.74 Å (Figure 6 and Table S1). NMR and IR spectra. The 1H and 19F NMR spectra of compounds 1–4 were recorded in D2O. The resonances for the nitrogen-bonded proton of the cations were not observed in the 1H NMR spectra due to rapid exchange with deuterons of the solvent in D2O solutions. The other 1H NMR resonances of the cations were observed as ex- pected. The 19F NMR spectrum of 1–4 shows a strong sin- glet signal at 130 ppm with two satellites due to the spin- spin interactions 29Si–19F J(SiF) =106 Hz. (See Figures S1–S8) The IR spectra of compounds 1–4 reveal two exten- sive regions for absorption bands of N–H stretching and N–H bending in cations from 3100 to 3500 cm–1 and about 1640 cm–1, respectively. Absorption bands for Si–F stretch- ing and bending can be found in the range of about 730 and 470 cm–1. Of the five normal vibrations expected for the [SiF6]2– anion, only two are infrared active.27 This is also in accordance with the other ammonium hexafluori- dosilicate salts.28 (See Figures S9–S16) Figure 4. Crystal structure of 3 showing the atom numbering scheme and the N–H···F hydrogen bonding interactions between cations and anions. Figure 5. Fragment of crystal packing in 4 with N–H···F hydrogen bond contacts. The hydrogen atoms on aromatic rings and methyl groups have been removed for clarity. 319Acta Chim. Slov. 2025, 72, 313–320 Pevec et al.: Structural Diversity of Different Aminomethylpyridinium ... 4. Conclusion In summary, four different crystalline compounds 1–4 were found in the product of the reactions between silicon dioxide and 2-aminomethylpyridine with the me- thyl substituent at different positions of the aromatic ring. The variations in the hydrogen bonds lead to the forma- tion of a supramolecular layered structure. The additional non-covalent π–π interactions enable a 3D network struc- ture. Each aminomethylpyridinium unit in compounds 1–4 functions as a two-connecting node, bridging two SIF62– anions, with the hydrogen-bonded layers adopting a square lattice (sql) network topology. However, two dis- tinct hydrogen-bonding synthons are observed. Synthon I contains an N(py)–H···F hydrogen bond (where the pyri- dine nitrogen is the donor) along with the single N–H···F hydrogen bond of the amino group whereas synthon II involves only an N–H···F hydrogen bond from the amino nitrogen. The NMR spectroscopy results for the 1–4 com- pounds showed their stability and purity in solution. Supplementary Material The Supporting Information is available: numerical parameters for π–π interactions, IR, 1H NMR and 19F NMR spectra of compunds 1–4. CCDC 2420167–2420170 contain the supplementa- ry crystallographic data for this paper. 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Atwood, J. Fluorine Chem. 2002, 115, 155–160 DOI:10.1016/S0022-1139(02)00046-5 Except when otherwise noted, articles in this journal are published under the terms and conditions of the  Creative Commons Attribution 4.0 International License Povzetek Pri reakcijah med silicijevim dioksidom, raztopljenim v fluorovodikovi kislini in štirimi različnimi 2-aminometilpirid- ini, kjer je metilna skupina na štirih različnih mestih piridinskega aromatskega obroča, so nastali štirje različni kristalin- ični ionski produkti. Sprememba položaja metilne skupine vpliva na arhitekturo vodikovih vezi med aminometilpirid- inijevimi kationi in heksafluoridosilikatnimi anioni. Tvorijo se lahko verižne strukture ali polimerne plasti. Dodatne nekovalentne π–π interakcije pa prispevajo k trodimenzionalni strukturi.