Inclusion of triphenylmethane derivatives by crown and linear O-containing molecules :  selective interactions and crystal structures

Abstract

The sulfamide derivative of triphenylmethanol, 3-[hydroxy(diphenyl)methyl]benzenesulfonamide (H₂NSO₂Ph)Ph₂COH was synthesized and, alongside with the parent triphenylmethanol and triphenylmethylamine, was investigated for selective interactions with crown ethers of different dimensionality (12-18-membered cycles). The molecule of 12-crown-4 (12C4) appeared to be the best candidate for Ph₃COH, Ph₃CNH₂ and Ph₃CNH₃·NCS, while (H₂NSO₂Ph)Ph₂COH forms the complex exclusively with 18-crown-6 (18C6). The triphenylammonia trifluoroacetate, Ph₃CNH₃·CF₃COO, selectively forms the complex only with 2-methoxyethanol. The crystalline products of the compositions (Ph₃COH)₂·12C4, (Ph₃CNH₂)₂·12C4, (Ph₃CNH₃·NCS)₂·12C4, [(H₂NSO₂Ph)Ph₂COH]₂·18C6 and Ph₃CNH₃·CF₃COO CH₃OCH₂CH₂OH were obtained and studied by X-ray single crystal diffraction.

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Introduction

Publication by Charles J. Pedersen of the synthesis of crown ethers and their property to form host–guest complexes with cations and comparatively small neutral guest molecules^1,2 has initiated the search and investigation of new, functionally isomorphous to crown ethers host molecules,^3–11 like cyclic cryptands, calixarenes and calixcrowns, cyclodextrines,¹² and acyclic molecules like aromatic diols,⁸ arylureas,^13,14 derivatives of triphenylmethane (tritane)^7,9,14etc. The numerous studies revealed the low selectivity of triphenylmethanol (tritanol, Ph₃COH) which binds in supramolecular complexes methanol, acetone, dimethyl formamide, dimethylsulfoxide, 1,4-dioxane, morpholine, piperidine, N-methylpiperazine, phenoxine,^9,15tetrahydrofurane.¹⁶Triphenylsilanol Ph₃SiOH, the precise analogue of triphenylmethanol, in its turn forms stable adducts with dimethylsulfoxide and 1,4-dioxane due to O–H⋯O and C–H⋯π(arene) interactions.^17,18 Similarly, triphenylmethanaminium chloride forms an inclusion compound with acetone.¹⁹ Now we are witnesses to the growing numbers of successful application of bulky host molecules. Thus, using excellent inclusion properties of bulky bisphenols Csöregh and co-workers²⁰ have stabilized carboxylic acid and ester molecules in a monomeric state for spectroscopic investigation. The recent research of Tohnai et al.²¹ has demonstrated the triphenymethylamine ability for an efficient and robust fabrication of [4 + 4] ion-pair clusters consisting of a wide range of sulfonic acids with an emphasis on the efficiency of the combination of sterically hindered triphenylmethylamine and sulfonate ions (complementarity in hydrogen bonding, steric effects of the substituents, acidity of the sulfonic acids). In 1998 Hayashi et al.²² showed on fluorosubstituted triphenylmethanol derivatives that the C–H⋯F(-C) interactions control the packing motif as well as the thermal stability of the crystal, in continuation in the hot CrystEngComm article Schollmeyer et al.²³ demonstrated that the trityl alcohols bearing three bromine or three iodine atoms at the para-positions of the aromatic units, as well as the fluorosubstituted derivatives of triphenylmethanol may be a very useful platform for analysing OH⋯π and halogen–π interactions as driving forces in crystal packing.

Surprisingly, apart from the two known examples of Ph₃SiOH²⁴ and Ph₃CSH²⁵ inclusion by 12-crown-4 (12C4), no systematic study of crown inclusion into the network of these bulky molecules has been carried out so far. This has motivated us to synthesize and study by X-ray diffraction the crystalline inclusion complexes of tritane derivatives with crown ethers of different dimensionality with an emphasis on the selectivity of interactions in these binary systems.

Experimental

Preparation of the crystalline inclusion compounds

It has been stated that spontaneous evaporation of solvents from the mixture of coronands I–III with triphenylmethanol (IVa), 1,1,1-triphenylmethanamine (IVb) and 1,1,1-triphenylmethanaminium thiocyanate (IVc) results in the crystalline molecular complexes of compositions (IVa)₂.I (complex VI), (IVb)₂.I (complex VII), (IVc)₂.I (complex VIII), respectively (Scheme 1).

Scheme 1 Formulae of the substances used.

The precipitation of VI from methanol solution indicates its higher stability in comparison with the triphenylmethanol complex with methanol.^9,15 The incorporation of the H-donor sulfamide group in the phenyl ring of IVa molecule yielding the 3-[hydroxy(diphenyl)methyl]benzenesulfonamideV drastically changes the mode of intermolecular recognition and results in the extraction of the largest 18C6 from the reaction mixture of I, II, III with the formation of the crystalline molecular complex of the composition (V)₂.III (complex IX). In previously reported studies no selectivity in the interaction of neutral molecules with the titled crown ethers was registered.⁴ Moreover, the bulky di(benzenesulfonyl)amine HN(SO₂C₆H₅)₂ yields crystalline molecular complexes both with I²⁶ and III.^27–29 The replacement of the thiocyanate anion (IVc) by trifluoroacetate (IVd) dramatically changes the complexation process. From the methanolic mixture of I, II, III, compound IVd is reverted in an invariable form, while from the solution IVd–I–methanol–2-methoxyethanol the crystalline complex of triphenylmethanaminium trifluoroacetate with 2-methoxyethanol (compound X) is precipitated selectively. Thus, herein for the first time the selective interaction of bulky triphenylmethane derivatives with crown ethers is described with an emphasis on the possibility of crown ethers' separation³⁰ similar to the procedure described earlier.^31,32

The initial chemicals were used as received from Aldrich without further purification. The ¹H NMR spectra were recorded with a Bruker AC 300 instrument at 300 MHz using tetramethylsilane as an internal reference. Thin-layer chromatography was conducted on Silufol plates with 1 : 8 methanol–chloroform as eluent and ninhydrin as developer. The crown ethers appeared as gray spots against a pink background.

Compound V, 3-[hydroxy(diphenyl)methyl]benzenesulfonamide: a mixture of 1,1′,1″-(chloromethanetriyl)tribenzene (2.788 g, 10 mmol) and chlorosulfonic acid (2.35 g, 20 mmol) was heated for 8 h at 150 °C and then cooled and poured onto 50 g of ice. The crystals were separated, placed into 40 ml of 25% aqueous ammonia, and heated with stirring for 12 h. The crystals that formed at 20 °C were washed with water, dried in air, and recrystallized from acetone–hexane (1 : 1). Yield: 1.80 g (53%), mp 188–190 °C, found, %: C 67.21; H 5.09; N 4.19; S 9.55, required for C₁₉H₁₇NO₃S: C 67.24; H 5.05; N 4.13; S 9.45. ¹H NMR (CDCl₃), δ, ppm: 7.27m, 7.44m (14H, CH).

Compound VI, triphenylmethanol–1,4,7,10-tetraoxacyclododecane, 2 : 1 : triphenylmethanol (260 mg, 1 mmol) and a mixture of 1,4,7,10-tetraoxacyclododecane (176 mg, 1 mmol), 1,4,7,10,13-pentaoxacyclopentadecane (220 mg, 1 mmol) and 1,4,7,10,13,16-hexaoxacyclooctadecane (264 mg, 1 mmol) were dissolved in methanol (10 ml) The colorless, transparent crystals were obtained by slow evaporation of solvents at room temperature for several days. Yield: 593 mg (85%), mp 147–148 °C, found, %: C 79.28; H 6.94, required for C₄₆H₄₈O₆: C 79.33; H 6.90. ¹H NMR (CDCl₃), δ, ppm: 1.62 (s 2H, OH), 3.70 (s, 16H, CH₂), 7.24–7.35 (m, 30H, CH).

Compound VII, 1,1,1-triphenylmethanamine–1,4,7,10-tetraoxacyclododecane, 2 : 1 : 1,1,1-triphenylmethanamine (259 mg, 1 mmol) and a mixture of 1,4,7,10-tetraoxacyclododecane (176 mg, 1 mmol), 1,4,7,10,13-pentaoxacyclopentadecane (220 mg, 1 mmol) and 1,4,7,10,13,16-hexaoxacyclooctadecane (264 mg, 1 mmol) were dissolved in a mixture of benzene/diethyl ether (1 : 2, 5 ml). The colorless, transparent crystals were obtained by slow evaporation of solvents at room temperature for several days. Yield: 495 mg (71%), mp 94–95 °C, found, %: C 79.51; H 7.25; N 4.03, required for C₄₆H₅₀N₂O₄: C 79.53; H 7.24; N 4.05. ¹H NMR (CDCl₃), δ, ppm: 1.86 (s, 4H, NH), 3.70 (s, 16H, CH₂), 7.20–7.32 (m, 30H, CH).

Compound VIII, triphenylmethanaminium thiocyanate–1,4,7,10-tetraoxacyclododecane, 2 : 1 : triphenylmethanaminium thiocyanate (318 mg, 1 mmol) and a mixture of 1,4,7,10-tetraoxacyclododecane (176 mg, 1 mmol), 1,4,7,10,13-pentaoxacyclopentadecane (220 mg, 1 mmol) and 1,4,7,10,13,16-hexaoxacyclooctadecane (264 mg, 1 mmol) were dissolved in methanol (15 ml). The colorless, transparent crystals were obtained by slow evaporation of solvents at room temperature for several days. Yield: 650 mg (80%), mp 170–172 °C, found, %: C 70.85; H 6.48; N 6.93; S 7.89, required for C₄₈H₅₂N₄O₄S₂: C 70.90; H 6.45; N 6.89; S 7.93. ¹H NMR (CDCl₃), δ, ppm: 3.70 (s, 16H, CH₂), 7.09–7.45 (m, 30H, CH).

Compound IX, 3-[hydroxy(diphenyl)methyl]benzenesulfonamide–1,4,7,10,13,16-hexaoxacyclooctadecane, 2 : 1 : 3-[hydroxy(diphenyl)methyl]benzenesulfonamide (340 mg, 1 mmol) and a mixture of 1,4,7,10-tetraoxacyclododecane (176 mg, 1 mmol), 1,4,7,10,13-pentaoxacyclopentadecane (220 mg, 1 mmol) and 1,4,7,10,13,16-hexaoxacyclooctadecane (264 mg, 1 mmol) were dissolved in a mixture of acetone/hexane (1 : 1, 15 ml). The colorless, transparent crystals were obtained by slow evaporation of solvents at room temperature for several days. Yield: 835 mg (98%), mp 174–176 °C, found, %: C 63.71; H 6.24; N 2.99; S 6.85, required for C₅₀H₅₈N₂O₁₂S₂: %: C 63.67; H 6.20; N 2.97; S 6.85. ¹H NMR (CD₃OD), δ, ppm: 3.62 (s, 24H, CH₂), 7.27–7.44 (m, 28H, CH).

Compound X, triphenylmethanaminium trifluoroacetate–2-methoxyethanol, 1 : 1 : triphenylmethanaminium trifluoroacetate (373 mg, 1 mmol) (373 mg, 1 mmol)) and 1,4,7,10-tetraoxacyclododecane (176 mg, 1 mmol) were dissolved in a mixture of methanol/2-methoxyethanol (1 : 1, 10 ml). The colorless, transparent crystals were obtained by slow evaporation of solvents at room temperature for several days. Yield: 380 mg (85%), mp 155–156 °C, found, %: C 64.13; H 5.80; N 3.19; F 12.64, required for C₂₄H₂₆F₃NO₄: %: C 64.18; H 5.83; N 3.12; F 12.68. ¹H NMR (DMSO), δ, ppm: 2.49 (s, 3H, CH₃), 3.49 (s, 4H, CH₂), 7.05–7.44 (m, 30H, CH).

Crystallographic studies

The X-ray intensity data for VI–X were recorded at room temperature on a Bruker SMART 1000 CCD area detector diffractometer employing graphite monochromatized Mo Kα radiation (λ = 0.71073 Å) in ϕ and ω scan mode. Final unit cell dimensions and positional data were obtained and refined on an entire data set. Integration and scaling resulted in a data set corrected for Lorentz and polarization effects using DENZO.³³ The scaling as well as global refinement of the crystal parameters were performed by SCALEPACK.³³ The absorption correction for VI, VIII, IX was applied using SADABS.³⁴ The structure solution and refinement proceeded similarly using SHELX-97 program package³⁵ for all structures. Direct methods yielded all non-hydrogen atoms of the asymmetric unit. Some disorder was found in IX and X: in IX the O6 and C24 atoms of the macrocyclic ring are disordered over two positions with partial occupancies of 0.90(1) and 0.10(1), and only the major component was refined in an anisotropic approximation. In X the triflate anion, CF₃COO⁻ and 2-methoxyethanol molecule were modeled in such a way that anionic F and O atoms and CH₃–O–CH₂–CH₂− fragment of the 2-methoxyethanol molecule were disordered over two positions with partial occupancies of 0.58(1) and 0.42(1), respectively; both positions were refined in an anisotropic approximation. In all structures C–bound H atoms were placed in calculated positions and were treated using a riding-model approximation, with U_iso(H) = 1.2U_eq(C). The O- and N-bound H-atoms were determined from a difference Fourier map and were then allowed to refine isotropically with U_iso(H) = 1.5U_eq(O,N). DFIX restraints were applied to the N–H distances (d = 0.86 Å) in VII and VIII. Crystal data together with further details of data collections and refinement calculations are given in Table 1. CCDC reference numbers 690773–690777.

Table 1 Summary of the crystal data of the five studied compounds, VI–X, and structure refinement parameters

Compound	VI	VII	VIII	IX	X
Composition	2C19H16O·C8H16O4	2C19H17N C8H16O4	2(C19H18N·NCS)·C8H16O4	2C19H17 NO3S·C12H24O6	C19H18N·C2F3O2 C3H8O2
CCDC number	690773	690777	690776	690775	690774
Formula weight	696.84	694.88	813.06	943.10	449.46
Crystal system	Triclinic	Triclinic	Monoclinic	Triclinic	Monoclinic
Space group	P1	P1	P21/c	P1	C2/c
a /Å	8.3614(7)	8.4675(8)	14.7301(15)	8.4707(6)	17.069(4)
b /Å	10.4963(9)	10.2973(13)	16.1984(16)	12.4699(9)	10.694(3)
c /Å	11.710(1)	11.943(2)	9.729(1)	12.8600(9)	26.520(7)
α/°	82.114(2)	84.058(9)	90.0	115.372(1)	90.0
β/°	86.716(2)	88.008(12)	103.97(2)	97.929(1)	107.367(5)
γ/°	66.740(2)	67.966(8)	90.0	99.540(1)	90.0
V /Å^3	935.25(14)	960.1(2)	2252.7(4)	1176.63(14)	4620(2)
Z	1	1	2	1	8
D c /Mg m^−3	1.237	1.202	1.199	1.331	1.292
μ(MoKα)/mm^−1	0.081	0.076	0.165	0.179	0.103
F(000)	372	372	864	500	1888
Reflections collected / unique	5310/ 3605 [R(int) = 0.020]	3625 / 3373 [R(int) = 0.026]	12820 / 4413 [R(int) = 0.043]	6829 / 4541 [R(int) = 0.015]	12877 / 4554 [R(int) = 0.024]
Reflections with I>2σ(I)	2978	2622	1462	3154	3066
Goodness-of-fit	1.060	1.042	0.831	0.925	1.011
R, wR [I>2σ(I)]	0.048, 0.138	0.041, 0.111	0.054, 0.117	0.039, 0.096	0.043, 0.121

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Results and discussion

Crystallographic description of the complexes

Compounds VI and VII crystallize in the same triclinic space group P1 and have close unit cell dimensions, as is evident from Table 1. For both compounds the asymmetric unit comprises one half of the 12C4 molecule that resides on an inversion center and one Ph₃COH or Ph₃CNH₂ molecule in general position (Fig. 1). The geometry of the Ph₃COH (Ph₃CNH₂) and 12C4 molecules is in agreement with the literature data.^{24,25,36–38} The components are associated in the 1 : 2 molecular complexes via two single OH⋯O (NH⋯O) hydrogen bonds (Table 2).

Table 2 Hydrogen bond distances (Å) and angles (°) for VI–X

D–H⋯A	d(D–H)	d(H⋯A)	d(D⋯A)	∠(DHA)	Symmetry transformation for acceptor
VI
O(3)–H(3A)⋯O(1)	0.89(2)	1.94(2)	2.814(2)	169(2)	x, y, z
C(19)-H(19A)⋯O(2)	0.93	2.61	3.380(2)	141	x, y, z
C(8)-H(8A)⋯O(2)	0.93	2.59	3.482(2)	162	x, y − 1, z
VII
N(1)–H(1N)⋯O(1)	0.89(2)	2.22(2)	3.087(2)	168(2)	x, y, z
C(19)-H(19A)⋯O(2)	0.93	2.66	3.426(2)	140	x, y, z
C(8)-H(8A)⋯O(2)	0.93	2.65	3.493(2)	152	x, y − 1, z
VIII
N(1)–H(2N)⋯O(1)	0.89(2)	1.92(2)	2.790(3)	166(3)	x, y, z
N(1)–H(3N)⋯N(2)	0.90(2)	2.01(2)	2.892(4)	166(3)	x, y, z
N(1)–H(1N)⋯S(1)	0.90(2)	2.35(2)	3.246(3)	170(3)	−x + 1, −y + 2, −z + 1
IX
O(3)–H(1O)⋯O(2)	0.77(2)	2.16(2)	2.917(2)	169(2)	–x, −y, –z
N(1)–H(1N)⋯O(5)	0.82(2)	2.37(2)	3.029(2)	138(2)	x, y − 1, z
N(1)–H(1N)⋯O(6)	0.82(2)	2.51(2)	3.086(2)	129(2)	x, y − 1, z
N(1)–H(2N)⋯O(4)	0.88(2)	2.25(2)	3.013(2)	145(2)	–x, −y, –z
N(1)–H(2N)⋯O(5)	0.88(2)	2.41(2)	3.135(2)	140(2)	–x, −y, –z
X
N1–H(2N)⋯O(1)	0.94(2)	1.95(2)	2.877(5)	174(2)	x, y, z
N1–H(2N)⋯O(1′)	0.94(2)	1.98(2)	2.886(6)	162(2)	x, y, z
N1–H(1N)⋯O(2)	0.93(2)	1.93(2)	2.862(2)	177(2)	−x, y, −z + 1/2
N1–H(3N)⋯O(3)	0.95(2)	1.80(2)	2.752(11)	179(2)	x, y, z
N1–H(3N)⋯O(3′)	0.95(2)	1.82(2)	2.766(14)	174(2)	x, y, z
O(2)–H(2B)⋯O(4)	0.95(2)	1.71(3)	2.658(10)	173(2)	x, y, z
O(2)–H(2B)⋯O(4′)	0.95(2)	1.69(3)	2.640(10)	171(2)	x, y, z

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Fig. 1 ORTEP drawing (a) for VI, (b) for VII with a partial numbering scheme. Thermal ellipsoids are drawn at 50% probability level.

The crystal packing in VI and VII is dictated by the combination of conventional OH⋯O (NH⋯O) hydrogen bonds that combine the molecules in the 1 : 2 complex, weak CH(arene)⋯O(crown) interactions that combine the complexes in the tape with the hydrophobic exterior formed by the phenyl rings (Fig. 2), and the concerted sextuple phenyl embrace (SPE)³⁹ between the Ph₃COH (Ph₃CNH₂) molecules in the neighboring tapes. Four host molecules surround each 12C4 molecule in the tape. The packing in VII is characterized by slightly increased distances analogous to those shown in Fig. 2a for VI with the second hydrogen of the amino group being free of any involvement in hydrogen bonding (very similar to the pure phase of Ph₃CNH₂).³⁷

Fig. 2 Crystal packing for VI and VII, (a) fragment of tape in VI with the shortest C–H⋯O distances shown by dashed lines, (b) fragments of adjacent tapes with SPE between two Ph₃COH molecules, (c) fragment of tape in VII with the shortest N–H⋯O and C–H⋯O distances shown by dashed lines.

This ordering function of 12C4 molecule in VI and VII is looking very amazing in confrontation with the relative although rather restrictive examples available in CSD:⁴⁰ thus, inclusion of a dioxane molecule in the network of isostructural Ph₃COH³⁶ or Ph₃SiOH¹⁷ molecules results in the 1 : 1 adduct in the first case and 1 : 2 adduct in the second one with pronounced changes in the crystal packing, although both compounds crystallize in the same triclinic crystal system. On the other hand, the same hosts yield the isostructural 2 : 1 aggregates with dimethylsulfoxide, both being crystallized in the same C2/c space group with close unit cell dimensions.^15,17 Ferguson and co-workers³⁶ analysing the series of the group 14 Ph₃MOH molecules (M = C, Si, Ge, Sn, Pb) revealed for them different crystal packing motifs: the C-, Si- and Ge-^17,41 derivatives represent hydrogen-bonded tetramers with the O-atoms in a flatten tetrahedral arrangement, while Sn- and Pb-containing molecules have structures consisting of zigzag chains of planar Ph₃M (M = Sn, Pb) groups joined by OH groups giving trigonal bipyramidal geometry at M,⁴² whilst in Ph₃CSH,⁴³ a precise analogue of Ph₃COH as well as in PhCNH₂,³⁷ being isoelectronic with Ph₃COH, there are no intermolecular hydrogen bonding despite the availability of potential H-donors (SH, NH₂groups) and H-acceptors (S, N-lone pair), and the structures consist of isolated molecules with no indication that the H-atoms take part in any hydrogen bonding. Concluding this section, the row of the relative crown-containing binary systems (Ph₃COH)₂.12C4 (VI), (Ph₃CNH₂)₂.12C4 (VII) (present work), (Ph₃SiOH)₂.12C4,²⁴ and (Ph₃CSH)₂.12C4²⁵ represents the isomorphous aggregates with close unit cell dimensions and a common structural motif. It permits to conclude the ordering and leveling function of the 12C4 molecule upon its inclusion.

The view of complex VIII is shown in Fig. 3. The ternary salt-like adduct VIII crystallizes in the centrosymmetric space groupP2₁/c and, similar to VI and VII, the 12C4 molecule resides on an inversion center. The components in the crystal are held together via the diverse system of charge-assisted hydrogen bonds, NH⁺⋯O(crown), NH⁺⋯N⁻(NCS⁻) and NH⁺⋯S⁻(NCS⁻) (Fig. 3, Table 2).

Fig. 3 ORTEP drawing for VIII with a partial numbering scheme. Thermal ellipsoids are drawn at 50% probability level.

The tetrahedral ammonia group provides one hydrogen for the NH⁺⋯O interaction with a crown molecule and two hydrogens for interionic NH⁺⋯N⁻(NCS⁻) and NH⁺⋯S(NCS⁻) interactions with two inversion-related NCS⁻ anions. Just as in the two previous structures, these concerted interactions combine the components in the tape propagated along the c axis in the crystal (Fig. 4). The neighboring tapes are packed in an antiparallel arrangement to maximize the SPE. The crystal architecture of VIII is very close to structure organization in tritylammonium chloride 1,4-dioxane solvate, Ph₃CNH₃Cl.(CH₂CH₂O)₂ (YAGSIJ refcode in CSD).⁴⁴

Fig. 4 Fragment of tape in VIII.

As was stressed above, incorporation of the amidosulfoxide group into the phenyl ring of IVa results in competition between the two donor groups (SO₂NH₂ and OH) of V for the crown's oxygens and following the Etter's rule⁴⁵ in a preferable interaction of the stronger H-donor, SO₂NH₂group with the macrocyclic oxygens via two bifurcated NH⋯O hydrogen bonds with the formation of 1 : 2 molecular complex IX (Fig. 5, Table 2). IX crystallizes in triclinic space group P1 where the 18C6 molecule resides on an inversion center. The hydroxyl group seeking for the next H-acceptor is responsible for the association of these complexes into tapes viaOH⋯O(SO₂) hydrogen bonds (Fig. 6, Table 2). Similar to the previous examples, the tape in IX is characterized by the hydrophilic interior saturated by hydrogen bonds and two external hydrophobic sides formed by the phenyl rings. Compound IX represents the first known example of the inclusion of spacious 18C6 molecule in the lattice of triphenylmethanol derivative. The common feature of the crystal packing for VI–IX is a ribbon motif with crown inclusion within the ribbon and the SPE formulated between the neighboring ribbons.

Fig. 5 ORTEP drawing for IX with a partial numbering scheme. Thermal ellipsoids are drawn at 50% probability level.

Fig. 6 Packing diagram for IX (a), fragment of tape (b), fragments of adjacent tapes with SPE between two V molecules.

Compound X of the 1 : 1 : 1 stoichiometry is formed as a result of the interaction of IVd with a linear 2-methoxyetanol molecule. X crystallizes in monoclinic space groupC2/c. The content of the asymmetric unit is shown in Fig. 7. Similar to VIII it is a ternary complex where two hydrogens of the same ammonia group are involved in the NH⁺⋯O(COO⁻) and NH⁺⋯O(2-methoxyethanol) contacts (Table 2). Furthermore, inside the complex the terminal hydroxyl group of the 2-methoxyethanol molecule participates in OH⋯O⁻(COO⁻) interaction with the second carboxyl oxygen. These three hydrogen bonds close the eleven-membered ring, R³₃(11) using a graph set notation.⁴⁵

Fig. 7 ORTEP drawing for X with the partial numbering scheme. Thermal ellipsoids are drawn at 50% probability level.

Contrary to VIII where each ammonia group interacts with two anions and one neutral crown molecule, in X the third ammonia hydrogen is involved into NH⁺⋯O interaction with the second 2-methoxyethanol molecule related by the two-fold axis with the basic one. These concerted interactions combine two complexes into a six-membered calix-like capsule stabilized by 8 charge-assisted hydrogen bonds within the hydrophilic core that is covered by the hydrophobic exterior formed by six phenyl rings of two tritylammonia cations and two terminal methyl groups of 2-methoxyethanol molecules (Fig. 8). The CH⋯F interactions^22,23,46 between triflate anion and 2-methoxyethanol molecule are responsible for the association of the 6-membered globules into tape running along the b direction in the crystal.

Fig. 8 Packing diagram for X: (a) network of hydrogen bonds shown by dashed lines within the six-membered cluster, (b) space-filling representation of the cluster, (c) column of clusters sustained by CH⋯F interactions, (d) the SPE between adjacent clusters.

Thus, the present study amplifies the scanty family of trytilammonia salts by two novel representatives. Contrary to the trytile sulfonates studied so far²¹ all of which represent binary adducts and formulate the well-defined [4 + 4] ion-pair clusters, VIII and X alongside the tritylammonium chloride acetone and tritylammonium chloride dioxane solvates [19,44] belong to the ternary compounds with the inclusion of the different O-containing neutral molecules (acetone, dioxane, 12C4, 2-methoxyethanol) in the ionic crystal lattice of the parent salt. The size and topology of these guests appear to be crucial for the final aggregates: linear acetone and 2-methoxyethanol molecules facilitate the formation of the isolated 6-membered clusters while the cyclic double-face 1,4-dioxane and 12C4 molecules provide extended 1D structures. In any closest environment [three anions,²¹ two anions and one neutral molecule^19,44 or one anion and two neutral molecules (present work)] all three ammonium hydrogens are involved in the hydrogen bonding system.

Conclusions

For the first time the approaches of supramolecular chemistry were used to estimate the preferable in size crown ethers (in the order of 12–18-membered CEs) for interaction with triphenylmethane derivatives. The 12C4 molecule has proven to be the best candidate as it is selectively included in the crystal lattice of neutral Ph₃COH and Ph₃CNH₂ in the 1 : 2 ratio and in the ionic network of Ph₃CNH₃NCS in the 1 : 1 : 1 ratio. Contrary to the pure forms of Ph₃COH, Ph₃SiOH, Ph₃CSH, and Ph₃CNH₂ which differ essentially by the crystal packing, the corresponding binary aggregates with 12C4 appear to be isomorphous and ordered with each macrocyclic molecule entrapping by four bulky host molecules. The functionalization of one of the phenyl rings in the Ph₃COH molecule by the H₂NSO₂-group provides its involvement in the interaction with 18C6 in a traditional manner and excludes the hydroxyl group from the host–guest interactions. The supramolecular architecture of the studied tritylammonium salts is dictated by the concerted effect of the topology of the anion and the included neutral molecule, being 1D structure for Ph₃CNH₃·NCS assimilating cyclic 12C4 molecule and the isolated six-membered capsule upon inclusion of linear 2-methoxyethanol molecules in the ionic lattice of Ph₃NH₃·CF₃COO. In all cases the common packing motif maximizes the SPE arrangement of the host molecules.

Acknowledgements

E.V.G. and W.J.W. are indebted to the National Science Council of Taiwan 94-2811-M-032 project for financial support.

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Footnote

† CCDC reference numbers 690773–690777. For crystallographic data in CIF or other electronic format see DOI :  10.1039/b810076d

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