o-Bisguanidinobenzene, a Powerful Hydrogen Acceptor: Crystal Structures of Organic Complexes with Benzoic Acid, Phenol, and Benzyl Alcohol Masatoshi Kawahata,† Kentaro Yamaguchi,‡,§ and Tsutomu Ishikawa*,†
CRYSTAL GROWTH & DESIGN 2005 VOL. 5, NO. 1 373-377
Graduate School of Pharmaceutical Sciences and Chemical Analysis Center, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan Received April 10, 2004
ABSTRACT: An o-phenylenediamine-bisguanidine derivative, o-phenylenebis(N,N′-dimethyl-N,N′-ethylene)guanidine (BG), was designed as a powerful hydrogen acceptor. The complexation of BG with a variety of hydrogen donor aromatics carrying OH groups such as benzoic acid (BA), phenol (PH), and benzyl alcohol (BAL) led to the successful isolation of the expected 1 + 1 crystalline complexes, regardless of the acidity of the hydrogen donors. In the case of BA, additional 1 + 2 and 1 + 4 BG-BA crystalline complexes were formed under rigorous conditions of stoichiometry-controlled complexation. These crystals were fully characterized by X-ray crystallographic analysis, indicating that nonbonded interactions in addition to N-H hydrogen bonding play an important role during the crystallization process. Mutual interconversion among the BG-BA crystalline complexes was achieved by the addition of either component to the original complex. Thus, BG was found to act as a powerful hydrogen acceptor in hydrogen bond-based complexation with hydrogen donor aromatics. Introduction The creation of a desired architecture is one of the main goals in crystal engineering and solid state supramolecular chemistry.1 The role of hydrogen bonding for these purposes is well-established.2 It is known that guanidines are not only superbases due to their strong basicity3 but can also act as key units in the formation of supramolecules.4 Recently, we developed guanidine chemistry focusing on uncovering potential abilities of the guanidinyl functions such as chiral auxiliaries5 and designed a new o-phenylenediamine-bisguanidine derivative, o-phenylenebis(N,N′-dimethyl-N,N′-ethylene)guanidine (BG), as a potential hydrogen acceptor. Thus, 1 + 1 complexation of BG with a variety of hydrogen donor aromatics carrying an OH group such as benzoic acid (BA), phenol (PH), and benzyl alcohol (BAL) has led to the successful isolation of the expected crystalline complexes, regardless of the acidity of the hydrogen donors. Furthermore, by controlling the BG:BA molar ratio, additional 1 + 2 and 1 + 4 BG-BA crystalline complexes have been characterized. In the present paper, we describe the ability of BG as a powerful hydrogen acceptor for the formation of not only 1 + 1 organic crystalline complexes but also, in the case of BA, additional stoichiometry-controlled crystalline complexes. Results and Discussion BG is prepared by treatment of o-phenylenediamine with 2-chloro-1,3-dimethylimidazolinium chloride,6 according to our previously described method for guani* To whom correspondence should be addressed. Fax: +81-43-2902910. E-mail:
[email protected]. † Graduate School of Pharmaceutical Sciences. ‡ Chemical Analysis Center. § Present address: Faculty of Pharmaceutical Sciences at Kagawa Campus, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan.
Scheme 1. Expected Bidentate Type Structure of BG with Hydrogen Donor Molecules
dine compounds.7 We anticipated that the two guanidinyl functions in BG and the OH group of the hydrogen donor molecules would interact through a bidentate type hydrogen bonding similar to the proton sponge [1,8-bis(dimethylamino)naphthalene (DMAN)]8 to form a stable 1 + 1 system containing a five-membered ring as shown in Scheme 1. Crystal Structures of 1 + 1 Complexes. First, we tried complexation of BG with BA, a strong acid. A mixture of equimolar amounts of BG and BA in dichloromethane was stirred at room temperature for 3 h followed by slow evaporation of the solvent to afford crystalline compound, mp 110-111 °C, in 93% yield. The 1H NMR spectrum shows that the product is a 1 + 1 mixture of BG and BA molecules. However, the X-ray crystallographic analysis indicates that only one guanidyl function (G1: red color) of the BG component participates in an intermolecular N-H hydrogen bonding [N- - -O distance, 2.710(3) Å] with the carboxyl group of the BA component (yellow color) and that the remaining guanidyl function (G2: blue color) in the BG component is free from a hydrogen bond interaction (Figure 1). A Y-shaped conjugated structure of three guanidyl C-N bonds with nearly equal bond lengths (1.33-1.34 Å) is observed in the hydrogen-bonded G1 moiety. The carbonyl function of the carboxyl group in the BA component contributing to the N-H hydrogen bonding is found to interact with an aromatic hydrogen at the meta position of a neighboring BA molecule [O- - -C distance, 3.266(3) Å] as shown in Figure 1a.
10.1021/cg049864c CCC: $30.25 © 2005 American Chemical Society Published on Web 08/20/2004
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Figure 1. Interactions of the 1 + 1 BG-BA crystalline complex: (a) N-H (blue - - -) and O-H (pink - - -) hydrogen bondings, face-to-face (black T), and van der Waals (orange T) interactions are indicated; (b) N-H hydrogen bonding (blue - - -) and parallel face-to-face (black T) interactions are indicated.
These interactions give a complex architecture of a hydrogen bond network, in which the hydrogen-bonded G1 moiety shows nonbonded face-to-face interaction [C- - -C distance, 3.375(4) Å] with the benzene ring of the BA component of another pair of BG and BA in addition to a cross-linked van der Waals interaction [C- - -C distance, 3.436(4) Å] between the NMe group of the G1 moiety of BG and the NMe group of the G2 moiety of another BG (G1-NMe- - -MeN-G2) (Figure 1a). Furthermore, as shown in Figure 1b, the G2 moieties of two neighboring BG components are settled in a parallel face-to-face orientation with respect to each other. Next, a weak acid PH was used as a hydrogen donor in place of BA. The treatment of BG in toluene with PH similarly afforded a crystalline complex, mp 78-79 °C, in 95% yield. The X-ray crystallographic analysis indicates that complexation is built through a N-H hydrogen bond network [N- - -O distance, 2.698(5) Å] between one guanidyl (G1: red color) moiety of the BG component and the OH group of the PH component (yellow color) identical to the BG-BA crystalline complex (Figure 2). However, in this crystal, no Y-shaped conjugated structure of three guanidyl C-N bonds was observed, even in the presence of the hydrogen-bonded G1 moiety. A T-shaped CH-π interaction [C- - -C distance, 3.681(7) Å] between each benzene ring of the BG (CH unit) and the PH (π unit) components is observed (Figure 2a). Intermolecular van der Waals interactions [C- - -C distance, 3.39(1) Å] between the NMe groups of
Figure 2. Interactions of the 1 + 1 BG-PH crystalline complex: (a) N-H hydrogen bonding (blue - - -) and T-shape CH-π (green T) interactions are indicated; (b) N-H hydrogen bonding (blue - - -) and van der Waals (orange T) interactions are indicated.
the hydrogen bond-free guanidyl (G2: blue color) moieties with two neighboring BG components (G2-NMe- - MeN-G2) are observed (Figure 2b), different from the BG-BA crystalline complex in which the G1-NMe- - MeN-G2 interaction is formed. Finally, neutral BAL was added to BG under the same conditions as PH. The BG-BAL crystalline complex could also be quantitatively isolated as colorless prisms, mp 38-40 °C. Although the product was unstable, careful measurement of X-ray crystallographic analysis led to a successful data collection, showing that the complex is basically composed of the same N-H hydrogen bond interactions [N- - -O distance, 2.877(3) Å] (Figure 3). A T-shaped CH-π interaction [C- - -C distance, 3.740(4) Å] between the benzene rings of the BG (CH unit) and the BAL (π unit) components (Figure 3a) and cross-linked van der Waals interactions between NMe groups of two neighboring BG components [C- - -C distance, 3.471(4) Å] (Figure 3b) like in the case of the BG-BA crystalline complex are observed. Interestingly, it is found that the BG-BAL crystalline complex could be categorized as a dimer through not only the N-H hydrogen bonding but also the T-shaped CH-π interactions (Figure 3a).
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Figure 4. Interactions of the 1 + 2 BG-BA crystalline complex, in which N-H (blue - - -) and O-H (pink - - -) hydrogen bonding, parallel face-to-face (black T), and T-shape CH-π (green T) interactions are indicated.
Figure 3. Interactions of the 1 + 1 BG-BAL crystalline complex: (a) N-H hydrogen bonding (blue - - -) and T-shape CH-π (green T) interactions are indicated; (b) N-H hydrogen bonding (blue - - -) and van der Waals (orange T) interactions are indicated.
Stoichiometry-Controlled Crystalline Complexes. Temperature-dependent crystallization of complexes between hydrogen acceptors and hydrogen donors through hydrogen bonding with a different ratio of each component had been reported by Mootz et al., although without isolation of the product, when pyridine was treated with either hydrogen fluoride9 or formic acid10 under severe temperature-controlled conditions (from -110 to -40 °C). As mentioned above, one of the two cyclic guanidyl moieties in the BG component in all 1 + 1 crystalline complexes is free from N-H hydrogen bonding. This means that the hydrogen bond-free guanidyl moiety could logically act as an additional hydrogen acceptor for the formations of alternative crystalline complexes, leading us to attempt the preparation of crystalline complexes between the BG molecule and an excess amount of hydrogen donor aromatics in different molar ratios. Crystallization attempts with a weak acid PH and a neutral BAL as hydrogen donors have failed. However, two kinds of crystalline complexes were successfully obtained in the presence of a strong acid BA. According to the above operation for the preparation of the 1 + 1 BG-BA crystalline complex, BG was
treated with two equivalents of BA to smoothly afford a 1 + 2 BG-BA crystalline complex, mp 62-63 °C, in 97% yield. In this case, the X-ray crystallographic analysis (Figure 4) indicates that the first BA component [BA(1): yellow color], as expected, contributed to N-H hydrogen bond formation [N- - -O distance, 2.731(2) Å] through one guanidyl function (G1: red color) in the BG component, which interacted with the second BA [BA(2): pink color] with a parallel face-to-face interaction [C- - -C distance, 3.110(3) Å] albeit in a non-crosslinked structure. However, the BA(2) component acts as a hydrogen donor to the BA(1) component through an O-H hydrogen bonding [O- - -O distance, 2.491(2) Å]. A T-shaped CH-π interaction [C- - -C distance, 3.708(4) Å] between the benzene rings of two BA components is also observed. The crystal packing of the 1 + 2 BG-BA crystalline complex, in which one guanidinyl moiety of the BG component is free from N-H hydrogen bonding, led us to further examine the possibility of inserting more BA units. After several trials, a 1 + 4 BG-BA crystalline complex, mp 111-112 °C, was obtained in 75% yield. In contrast with the former two 1 + 1 and 1 + 2 BG-BA complexes, the X-ray crystallographic analysis shows that the 1 + 4 BG-BA crystalline complex is a C2-symmetrical architecture based on a key N-H hydrogen bonding [N- - -O distance, 2.778(4) Å] between the BG and the BA [BA(1): yellow color] components (Figure 5a) commonly observed in crystalline complexes mentioned above. A parallel face-to-face interaction [C- - -C distance, 3.204(6) Å] is observed between the cyclic guanidyl moiety of the BG component and the benzene ring of the N-H hydrogen-bonded BA(1) component (Figure 5a). A typical dimeric structure of a carboxylic acid through O-H hydrogen bonding is observed in the 1 + 4 BG-BA crystalline complex (Figure 5b), in which two N-H hydrogen bond-free BA(2) components [BA(2): pink color] contributed to the hydrogen bond formation [O- - -O distance, 2.455(8) Å], different from the BA(1)- - -BA(2) interaction in the 1 + 2 BG-BA crystalline complex as shown in Figure 4. Furthermore, the benzene protons of the BG component interact in two kinds of distorted T-shaped CH-π interactions [C- - -C distances, 3.677(7) and 3.701(9) Å]
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stoichiometry-controlled BG-BA crystalline complexes. Thus, it was found that BG acts as a powerful hydrogen acceptor in hydrogen bond-based complexation12 with OH-containing aromatics, albeit not in an expected bidentate type complexation.13 To our knowledge, these observations based on X-ray crystallography give the first experimental evidence for the possible diversity of molecular-molecular interactions caused by simply mixing acid and base components, potentially applicable to crystal engineering. In particular, the successful crystallization of stoichiometry-controlled complexes of BG with BA may lead to the preparation of desired crystalline complexes composed of multicomponents.14 Acknowledgment. This work was supported by Grants-in-Aid for Scientific Research (14370717 and 15659001) from the Ministry of Education, Culture, Sports, Science and Technology, Japan. We thank Dr. Burno Therrien, Chemical Analysis Center, Chiba University, for his kind discussion of this work. Supporting Information Available: Experimental procedure for the preparation of crystalline complexes and their spectral data. This material is available free of charge via the Internet at http://pubs.acs.org.
References
Figure 5. Interactions of the 1 + 4 BG-BA crystalline complex: (a) N-H hydrogen bonding (blue - - -), parallel face-to-face (black T), and distorted T-shape CH-π (green T) interactions are indicated; (b) O-H hydrogen bonding (pink - - -) and distorted T-shape CH-π (green T) interactions are indicated.
with the benzene rings of the N-H hydrogen bond-free BA components (Figure 5b). The stoichiometry-controlled crystallizations between BG and BA components led us to examine the interconversion among these crystalline complexes by addition of the calculated amount of the minor component to a solution of each complex in either dichloromethane or toluene. The addition of one and three molar amount(s) of the BA molecule to the 1 + 1 BG-BA complex smoothly afforded the 1 + 2 (86%) and the 1 + 4 BG-BA complexes (89%). Similar treatment of the 1 + 4 BG-BA complex with the BG molecule reversely yielded 1 + 2 (92%) and 1 + 1 BG-BA complexes (73%) dependent upon the amount of BG used. Furthermore, addition of either BA or BG to the 1 + 2 BG-BA complex gives the corresponding 1 + 4 (94%) or 1 + 1 BG-BA complexes (77%), respectively. Conclusions We successfully characterized 1 + 1 organic crystalline complexes of hydrogen acceptor BG molecules with three different types of hydrogen donors: BA, PH, and BAL.11 In the network system of each crystalline complex, different interactions are observed. Furthermore, BG was additionally cocrystallized with a strong acid BA in different composition ratios to provide
(1) (a) Desiraju, G. R. J. Mol. Struct. 2003, 656, 5-15. (b) Bond, A. D.; Jones, W. In Supramolecular Organization and Materials Design; Jones, W., Rao, C. N. R., Eds.; Cambridge University Press: Cambridge, 2002; pp 391-443. (c) Jones, W. Organic Molecular Solids: Properities and Applications; CRC Press: New York, 1997; pp 181-194. (d) Desiraju, G. R. Angew. Chem., Int. Ed. Engl. 1995, 34, 2311-2327. (2) For example: (a) Bensemann, I.; Gdaniec, M.; Lakomecka, K.; Milewska, M. J.; Polonski, T. Org. Biomol. Chem. 2003, 1, 1425-1434. (b) Shan, N.; Bond, A. D.; Jones, W. Tetrahedron Lett. 2002, 43, 3101-3104. (3) (a) Costa, M.; Chiusoli, G. P.; Taffurelli, D.; Dalmonego, G. J. Chem. Soc., Perkin Trans. 1 1998, 1541-1546. (b) Kovacevic, B.; Maksic, Z. B. Chem. Eur. J. 2002, 8, 16941702. (4) For example: Alcazar, V.; Segure, M.; Prados, P.; de Mendoza, J. Tetrahedron Lett. 1998, 39, 1033-1036. (5) (a) Isobe, T.; Fukuda, K.; Ishikawa, T. Tetrahedron: Asymmetry 1998, 9, 1729-1735. (b) Isobe, T.; Fukuda, K.; Araki, Y.; Ishikawa, T. Chem. Commun. 2001, 243-244. (c) Ishikawa, T.; Araki, Y.; Kumamoto, T.; Seki, H.; Fukuda, K.; Isobe, T. Chem. Commun. 2001, 245-246. (d) Hada, K.; Watanabe, T.; Isobe, T.; Ishikawa, T. J. Am. Chem. Soc. 2001, 123, 7705-7706. (e) Ishikawa, T.; Isobe, T. Chem. Eur. J. 2002, 8, 552-557. (6) (a) Isobe, T.; Ishikawa, T. J. Org. Chem. 1999, 64, 58325835. (b) Isobe, T.; Ishikawa, T. J. Org. Chem. 1999, 64, 6984-6988. (c) Isobe, T.; Ishikawa, T. J. Org. Chem. 1999, 64, 6989-6992. (7) Isobe, T.; Fukuda, K.; Ishikawa, T. J. Org. Chem. 2000, 65, 7770-7773. (8) Staab, H.; Saupe, T. Angew. Chem., Int. Ed. Engl. 1988, 27, 865-879. (9) Boenigk, D.; Mootz, D. J. Am. Chem. Soc. 1988, 110, 21352139. (10) Wiechert, D.; Mootz, D. Angew. Chem., Int. Ed. 1999, 38, 1974-1976. (11) During the course of our studies, Sundermeyer and Maksic et al. prepared 1,8-bis(tetramethylguanidino)naphthalene and 1,8-bis(dimethylethyleneguanidino)naphthalene under the same concept as ours and experimentally demonstrated that these bisguanidines were more basic than the corresponding diamine, DMAN, in the salt formation with fully dissociable inorganic acids such as HPF6. (a) Raab, V.;
o-Bisguanidinobenzene, a Powerful Hydrogen Acceptor Kipke, J.; Gschwind, R. M.; Sundermeyer, J. Chem. Eur. J. 2002, 8, 1682-1693. (b) Raab, V.; Harms, K.; Sundermeyer, J.; Kovacevic, B.; Maksic, Z. B. J. Org. Chem. 2003, 68, 8790-8797. (12) Anion inclusion by dithioureido functions on a 2,2′-bisnaphthalene skeleton was reported. Kondo, S.-I.; Nagamine, M.; Yano, S. Tetrahedron Lett. 2003, 44, 8801-8804. (13) We have observed that BG can form bidentate type complexes with some metal salts. These results will be published elsewhere soon.
Crystal Growth & Design, Vol. 5, No. 1, 2005 377 (14) Treatment of calix[4]arenes with a nitrogen heterocyle in an appropriate solvent led to the formation of complex crystals with more than three guests including the solvent as an additional component(s). (a) MacGillivary, L. R.; Atwood, J. L. J. Am. Chem. Soc. 1997, 119, 6931-6932. (b) MacGillivary, L. R.; Atwood, J. L. Chem. Commun. 1999, 181-182.
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