Takashi
Takeda
*a,
Shin-ichiro
Noro
b,
Takayoshi
Nakamura
b,
Yasutaka
Suzuki
c,
Jun
Kawamata
c and
Tomoyuki
Akutagawa
*a
aInstitute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi 980-8577, Japan. E-mail: takeda@tagen.tohoku.ac.jp
bResearch Institute of Electronic Science, Hokkaido University, Sapporo, Hokkaido 060-0820, Japan
cGraduate School of Medicine, Yamaguchi University, Yamaguchi, Yamaguchi 753-8512, Japan
First published on 2nd November 2017
We report a series of crystal structures of arylsulfonamide-armed anthraquinones (AQs) (1–4). The arylsulfonamide-armed AQs formed orthogonal aromatic arrangements between the AQ unit and terminal aryl units due to well-defined intramolecular hydrogen bonding between the carbonyl units of AQs and the amino groups of sulfonamide units. Three disubstituted AQs 1–3 formed fundamental dimer structures, which were stabilized by intermolecular π–π interaction between AQs. Subtle differences in the dimer structures led to different packing structures. Among them, the 1,8-bis(arylsulfonamide) derivative (1) formed solvated crystals of 1·(MeCN), which exhibited reversible and selective MeCN and/or EtCN adsorption–desorption behavior. Tetra(arylsulfonamide) AQ (4) with four bulky substituents on its periphery formed various host–guest molecular crystals of 4·X2 (X = toluene, xylene, trimethylbenzenes, 1,2,3,5-tetramethylbenzene, anisole, and benzonitrile) with a rectangular zero-dimensional cage surrounded by the π-planes of 4.
Very recently, we reported the electrochemical and photophysical properties of arylsulfonamide-armed anthraquinones (AQs) 1–4.12 Noncovalent intramolecular hydrogen bonding affected the electron-accepting properties of 1–4 (Fig. 1). Preferential molecular arrangement with intramolecular hydrogen bonding between the quinone and amine units was achieved by steric-restriction of the rotation of amine units with bulky arylsulfone units, which was also demonstrated by an X-ray single-crystal structure analysis of 2. Based on the molecular geometry of 2, we expected that arylsulfonamide-armed anthraquinone derivatives would be good synthons for the construction of well-defined supramolecular assemblies governed by weak noncovalent interactions for the following reasons: (1) strong hydrogen bonding interactions are negated in an intramolecular fashion, and thus weak noncovalent interactions should govern crystal packing; (2) the rigid π frameworks of anthraquinone and terminal aryl units are arranged orthogonally via a sulfonamide spacer; (3) the electronically active anthraquinone unit and polar sulfone unit should significantly contribute to intermolecular connection.
In this work, we report the crystal structures of 1–4 and their functions. Subtle differences in the nature of the substitution lead to diverse crystal structures. Thanks to the rigid, orthogonal molecular framework of arylsulfonamide-armed AQs 1–4, weak noncovalent interactions such as π stacking, dipole–dipole interaction and intermolecular C–H⋯O interaction efficiently contribute to the determination of the crystal structures of 1–4. Significant dimer structures were formed in disubstituted AQs, which amplified the differences in the molecular structures to induce different crystal arrangements in 1–3. Among them, crystal 1 showed reversible solvent-selective adsorption and crystal 4 showed selective inclusion of substituted benzene derivatives.
1·(MeCN) | 1·(EtCN) | 2 | 3 | |
---|---|---|---|---|
Recryst. solvent | MeCN | EtCN | Toluene | MeCN |
Chemical formula | C30H25N3O6S2 | C31H27N3O6S2 | C28H22N2O6S2 | C34H34N2O6S2 |
Formula weight | 587.66 | 601.69 | 546.61 | 630.77 |
Space group | P (#2) | P (#2) | P (#2) | P21/c (#14) |
a, Å | 8.70878(16) | 8.62524(16) | 8.13783(15) | 11.6922(2) |
b, Å | 12.5376(2) | 12.5088(2) | 11.6634(2) | 20.8466(4) |
c, Å | 12.6766(2) | 13.0025(2) | 13.4980(3) | 13.0536(2) |
α, ° | 86.7619(9) | 87.7507(11) | 93.4739(9) | |
β, ° | 79.0870(8) | 79.5340(10) | 96.7310(10) | 101.5286(7) |
γ, ° | 86.3097(11) | 85.0219(11) | 103.8825(11) | |
V, Å3 | 1354.89(4) | 1373.92(4) | 1229.92(4) | 3117.55(10) |
Z | 2 | 2 | 2 | 4 |
D calc, g cm−1 | 1.441 | 1.454 | 1.476 | 1.344 |
μ, cm−1 | 22.14 | 21.97 | 23.81 | 19.49 |
Refls. meas. | 14710 | 15837 | 14160 | 34920 |
Indep. refls. | 4849 | 4941 | 4398 | 5692 |
Refls. used | 4849 | 4941 | 4398 | 5692 |
R 1 (all) | 0.0661 | 0.0683 | 0.1037 | 0.0501 |
wR2 (all) | 0.1506 | 0.1574 | 0.2066 | 0.1125 |
R 1 (>2σ) | 0.0514 | 0.0521 | 0.0703 | 0.0439 |
wR2 (>2σ) | 0.1429 | 0.1435 | 0.1761 | 0.1091 |
GOF | 1.104 | 1.072 | 1.043 | 1.062 |
CCDC no. | 1550096 | 1550093 | 1550105 | 1550102 |
4·(Toluene)2 | 4·(Anisole)2 | 4·(Fluorobenzene)2 | 4·(Benzonitrile)2 | 4·(Xylene)2 | |
---|---|---|---|---|---|
Recryst. solvent | Toluene | Anisole | Fluorobenzene | Benzonitrile | Xylene |
Chemical formula | C68H74N4O10S4 | C68H76N4O12S4 | C66H70F2N4O10S4 | C68H70N6O10S4 | C70H82N4O10S4 |
Formula weight | 1235.59 | 1269.61 | 1245.54 | 1259.58 | 1267.68 |
Space group | P (#2) | P (#2) | P (#2) | P (#2) | P (#2) |
a, Å | 10.9957(8) | 10.9459(2) | 10.9315(2) | 10.9203(2) | 11.2092(4) |
b, Å | 12.0694(11) | 12.1089(2) | 12.0707(2) | 11.9997(2) | 12.1810(4) |
c, Å | 12.8047(7) | 12.9588(3) | 12.7651(2) | 12.8965(2) | 12.8326(4) |
α, ° | 85.373(6) | 84.1094(13) | 84.8346(7) | 84.6483(10) | 85.5050(17) |
β, ° | 73.757(5) | 72.9530(13) | 72.9469(7) | 73.4045(9) | 74.8198(18) |
γ, ° | 75.131(5) | 74.0952(13) | 75.4678(7) | 75.8535(10) | 73.1335(18) |
V, Å3 | 1576.8(2) | 1578.80(5) | 1558.54(5) | 1569.95(5) | 1618.26(9) |
Z | 1 | 1 | 1 | 1 | 1 |
D calc, g cm−1 | 1.301 | 1.335 | 1.327 | 1.332 | 1.301 |
μ, cm−1 | 18.89 | 19.25 | 19.63 | 19.19 | 18.52 |
Refls. meas. | 18025 | 18093 | 18016 | 18017 | 18885 |
Indep. refls. | 5647 | 5678 | 5596 | 5643 | 5820 |
Refls. used | 5647 | 5678 | 5596 | 5643 | 5820 |
R 1 (all) | 0.0926 | 0.0696 | 0.0599 | 0.0499 | 0.1313 |
wR2 (all) | 0.1973 | 0.1753 | 0.1341 | 0.1254 | 0.3241 |
R 1 (>2σ) | 0.0601 | 0.0568 | 0.0473 | 0.0419 | 0.0966 |
wR2 (>2σ) | 0.1540 | 0.1685 | 0.1262 | 0.1131 | 0.2700 |
GOF | 1.011 | 1.140 | 1.094 | 1.098 | 1.097 |
CCDC no. | 1550147 | 1550148 | 1550149 | 1576397 | 1576399 |
4·(1,2,3-Trimethylbenzene)2 | 4·(1,2,4-Trimethylbenzene)2 | 4·(pentamethylbenzene)2·(CHCl3) | 4·(Hexamethylbenzene)2 | ||
---|---|---|---|---|---|
Recryst. solvent | 1,2,3-Trimethylbenzene | 1,2,4-Trimethylbenzene | CHCl3/EtOH | CHCl3/EtOH | |
Chemical formula | C72H84N4O10S4 | C72H84N4O10S4 | C77H93Cl3N4O10S4 | C78H96N4O10S4 | |
Formula weight | 1293.72 | 1293.72 | 1469.2 | 1377.88 | |
Space group | P (#2) | P (#2) | P (#2) | P21/n (#14) | |
a, Å | 11.4757(5) | 11.0418(5) | 14.1225(3) | 14.0762(3) | |
b, Å | 12.2489(5) | 12.4363(5) | 17.0279(3) | 11.0705(2) | |
c, Å | 12.7795(6) | 12.5998(5) | 17.4930(3) | 23.2945(5) | |
α, ° | 85.3743(19) | 88.953(2) | 81.2059(11) | ||
β, ° | 76.1090(18) | 77.1337(19) | 69.2791(11) | 92.1146(10) | |
γ, ° | 70.8493(19) | 77.137(2) | 72.4461(10) | ||
V, Å3 | 1647.30(13) | 1643.53(11) | 3746.31(13) | 3627.51(13) | |
Z | 1 | 1 | 2 | 2 | |
D calc, g cm−1 | 1.304 | 1.308 | 1.302 | 1.261 | |
μ, cm−1 | 18.30 | 18.34 | 26.33 | 16.92 | |
Refls. meas. | 19124 | 18879 | 42313 | 38367 | |
Indep. refls. | 5918 | 5879 | 13423 | 6571 | |
Refls. used | 5918 | 5879 | 13423 | 6571 | |
R 1 (all) | 0.2328 | 0.1382 | 0.1338 | 0.1221 | |
wR2 (all) | 0.4139 | 0.2879 | 0.2007 | 0.2324 | |
R 1 (>2σ) | 0.1230 | 0.0848 | 0.0818 | 0.0870 | |
wR2 (>2σ) | 0.3184 | 0.2278 | 0.1783 | 0.2155 | |
GOF | 1.062 | 1.102 | 0.825 | 0.994 | |
CCDC no. | 1576401 | 1576402 | 1576404 | 1550107 |
Crystals 1·(MeCN) showed reversible and selective molecular adsorption–desorption behavior. The thermogravimetry (TG) curve of 1·(MeCN) revealed an approximately 7% weight loss at around 160 °C (Fig. S4†), which corresponds to the quantitative desorption of MeCN from the 1·(MeCN) crystals. The possible adsorption behavior of the desolvated crystal 1 was systematically examined in a variety of solvents, such as alkyl nitriles, alkyl halides, an alcohol, water, and an alkane, with different polarities, dipole moments, and sizes (Table 3). Desolvated crystals 1 were prepared by the thermal annealing of crystals 1·(MeCN) at 160 °C for 10 minutes under ambient conditions, and then exposed to vapor of the solvents in separate closet-vials. After the samples were exposed to the vapor overnight, the solvent readsorption behavior was confirmed by TG measurements. The desolvated crystals 1 show reversible and quantitative adsorption behavior only for MeCN and EtCN, to give 1·(MeCN) and 1·(EtCN), respectively. Other solvents did not show such behavior. Large alkyl nitriles such as PrCN, BuCN, and PentCN, as well as EtOH, PrCl, PrBr, PrI, and H2O, also did not show adsorption behavior.
To the best of our knowledge, such MeCN- and EtCN-selective adsorption molecular crystalline materials have not yet been reported. While the adsorption of several alkyl nitriles with coordination polymers has been reported, including Cu(II)–1,2-bis(4-pyridyl)ethane,14 Zn(II)–(5-azido isophthalic acid)[1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene],15 and Mg(II)–bis(1,4-benzenedicarboxylate)(4,4′-dipyridyl-N,N′-dioxide),16 these materials also adsorb other organic solvents14 or long-chain nitrile derivatives.15,16
To evaluate the crystallinity and selectivity of adsorption behavior, powder X-ray diffraction (PXRD) was performed and solvent adsorption–desorption isotherms of MeCN and EtCN were examined for crystals 1. Fig. 3a summarizes the PXRD patterns of crystals 1·(MeCN), desolvated crystals 1 after thermal annealing, and the readsorbed sample of 1·(MeCN) and the simulated pattern of crystals 1·(MeCN) based on the single-crystal X-ray structural analysis. The thermal annealing of crystals 1·(MeCN) at 433 K revealed a shift and disappearance of Bragg diffraction peaks, which was consistent with a change in the packing structure from 1·(MeCN) to 1 while maintaining high crystallinity. After readsorption of the MeCN molecule, the PXRD pattern was completely consistent with that of as-grown 1·(MeCN), suggesting a reversible structural transformation between desolvated crystals 1 and solvated 1·(MeCN) upon the adsorption–desorption of MeCN. Fig. 3b shows the adsorption–desorption isotherms of desolvated crystals 1 for MeCN and EtCN along with those for MeOH and EtOH for comparison. The ratio of adsorption–desorption molecules (nads) to host molecule 1 was plotted with respect to a relative pressure P/P0. Gate-opening MeCN adsorption behavior appeared at P/P0 = ∼0.7 and the amount of saturated adsorption was similar to 1.0 mol mol−1. Once a MeCN molecule was adsorbed into crystal 1, the adsorption state was stably maintained until P/P0 ∼ 0.04 in the desorption process. A similar gate-opening adsorption behavior for EtCN was also observed at P/P0 ∼ 0.5 with an increase in nads, which was lower than the gate-opening pressure of MeCN. This gate-opening sorption mechanism with huge hysteresis for adsorption–desorption was characteristic of adsorption accompanied by a structural change. Both of the guest molecules MeCN and EtCN interacted by multiple weak van der Waals interactions within the 1D channel, as demonstrated by the single-crystal X-ray analysis of 1·(MeCN), and the structural transformation of flexible van der Waals crystals was a driving force to achieve gate-opening 1D channels. The origin of the selective adsorption of MeCN and EtCN could be accounted for by dipole moments to open the gate and the period length of the fundamental π-dimer. While nitriles with a greater dipole moment (3.92 D for MeCN)17 could open the gate, less polar solvents, such as alcohols (1.70 D for MeOH),17 could not interact with the host molecular framework efficiently enough to open the one-dimensional channel. DFT calculation supported the affirmative MeCN/EtCN adsorption of 1 (see the ESI† for details). The period cycle (6.75 Å) of the permanent dipole moment of the fundamental π-dimer makes it possible to sort alkyl nitriles. An alkyl nitrile longer than the period cycle length could not be accommodated in the dimer and only the shorter MeCN (3.0 Å) and EtCN (4.5 Å) could be included in the dimer to open the gate.
This solvent inclusion behavior is affected by the size of the benzene ring (Fig. 5a). When nonsubstituted benzene was used for recrystallization, unstable single crystals were obtained, the quality of which soon turned poor after removal from the solvent. Thus, a too small guest molecule destabilized the crystals of this host–guest complex. In contrast, flexible distortion of the crystalline cage enabled the formation of the same host–guest complexes even with bulky benzene derivatives including trimethylbenzenes and 1,2,3,5-tetramethylbenzene (Fig. S7†). The host rectangular cage unit transmuted to modulate the void space for guest molecules (368–470 Å for each cage) so that more bulky benzene derivatives could be accommodated. When the bulky benzenes were included, two modes of stretching were possible for this supramolecular cage: (a) stretching along the long axis consisting of sulfone units and tert-butylphenyl groups [observed in 4·(xylene)2 and 4·(1,2,3-trimethylbenzene)2] or (b) slanting of the rectangular cage [observed in 4·(1,2,4-trimethylbenzene)2]. Much more bulky guest molecules including durene, pentamethylbenzene, and hexamethylbenzene further modulated the guest inclusion cage itself to another type (Form B in Fig. 5b). The bulky benzene guest is stabilized by π–π interaction and also van der Waals interaction between tert-butyl groups of host molecule 4 in Form B. The balance of the size of the guest and van der Waals interactions between the host and the guest play important roles in determining the packing arrangement of 4·(arene)2 in the crystal. In contrast to Form A, the packing arrangement of host molecule 4 in Form B does not have enough flexibility to modulate the void space. Under recrystallization from durene and pentamethylbenzene, the corresponding solvated crystals were obtained, where the solvate molecules filled the spare void space.
Fig. 5 (a) Relationship between host–guest crystals of 4·(arene)2. (b) Packing arrangement of 4·(hexamethylbenzene) viewed along the b-axis. Hexamethylbenzene molecules are shown in a CPK model. |
We next examined selective inclusion of the solvent into the pillar space in crystal 4. We chose to examine methylbenzene derivatives because the selective inclusion of liquid molecules with a similar size and polarity is very challenging. Fig. 6 shows the 1H NMR spectrum of crystal 4 obtained by recrystallization from equal volumes of a solvent mixture of toluene, mesitylene, 1,2,3-trimethylbenzene, and 1,2,4-trimethylbenzene. As a result, significant preferential inclusion of 1,2,3-trimethylbenzene was observed. The ratio of guest molecules to host 4 decreased in the order of 1,2,3-trimethylbenzene (100%), 1,2,4-trimethylbenzene (33%), toluene (22%), and mesitylene (10%). Highly polarized 1,2,3-trimethylbenzene (0.62 D at the B3LYP/6-31G level with the optimized structure) was preferentially included in the cage of 4, suggesting that dipole–dipole interaction within the crystalline cage space plays an important role.
Designed soft organic crystals with adsorption/inclusion properties based on the control of weak noncovalent interactions should increase the scope of potential functional crystalline materials from rigid crystalline materials such as MOFs and COFs.
Footnote |
† Electronic supplementary information (ESI) available: ORTEP drawings of 1–4. Dimer structures and packing arrangements of 2 and 3. Crystal structure of 1·(EtCN). Thermogravimetry curve of 1·(MeCN) crystals. DFT energy calculation of 1·(MeCN) and 1·(EtCN). Packing arrangements of crystals 4·(xylene)2, 4·(anisole)2, 4·(fluorobenzene)2, 4·(benzonitrile)2 and 4·(trimethylbenzene)2. Gas adsorption experiment with crystals 1 and 3. CCDC 1550093, 1550096, 1550102, 1550105, 1550107, 1550147–1550149, 1576397, 1576399, 1576401, 1576402 and 1576404. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7ce01752a |
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