Noncovalent Derivatives of Hydroquinone: Complexes with Trigonal Planar Tris(N,N-dialkyl)trimesamides Amy S. Cannon,† Bruce M. Foxman,*,‡ Donna J. Guarrera,§ and John C. Warner*,† Green Chemistry Program, School of Health and the Environment, University of Massachusetts Lowell, 3 Solomont Way, Suite 4, Lowell, Massachusetts 01854, Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454-9110, and JEOL USA, Incorporated, 11 Dearborn Road, Peabody, Massachusetts 01960 Received August 26, 2004;
CRYSTAL GROWTH & DESIGN 2005 VOL. 5, NO. 2 407-411
Revised Manuscript Received December 8, 2004
ABSTRACT: The solid-state behavior of hydroquinone 1 with tris(N,N-diethyl)trimesamide 2 and tris(N,N-dimethyl)trimesamide 3 has been determined using phase diagrams and X-ray diffraction techniques. A 3:2 complex, 4, forms between 1 and the diethyl derivative 2, while a 2:1 complex, 5, forms between 1 and the dimethyl derivative 3. X-ray structure determinations of the cocrystals reveal that the structures both contain a persistent R44(30) hydrogen bond ring system. The packing of the ring depends on the differing steric requirements of the methyl and ethyl substituents on trimesamides 2 and 3. Introduction Noncovalent derivatization1 involves the control of physical properties of materials using crystal forces. By using the principles of molecular recognition and self-assembly as a design feature, the construction of materials can be an environmentally benign technique2 and an example of the utilization of the principles of green chemistry.3 We have been exploring the behavior of hydroquinone (1) in a variety of hydrogen bond donating environments. Studies of the phase behavior of 1 with bis[N,N-dialkyl]amides has revealed that hydrogen bonding dominates in the crystal packing of these systems. Specifically, the hydroquinone will function predominately as a bis-hydrogen bond donor in 1:1 systems with the bis amides such as bis[N,N-diethyl]terephthalamide, forming chains of alternating hydroquinones and terephthalamides [Figure 1].4 In these systems, the phenolic hydrogen atoms of the hydroquinone form hydrogen bonds to the oxygen atoms of the terephthalamide amides. To complete the three-dimensional structure, these alternating chains pack together through interactions between the amide alkyl substituents. We have shown that when the steric influence imposed by the alkyl group substituents on the amide nitrogens is minimized [as with bis[N,N-dimethyl]terephthalamide], the crystal packing [Figure 2] of these systems allows for the incorporation of an additional hydroquinone within the matrix. Since the lone pair of electrons on the oxygen atoms of the hydroquinone may serve as hydrogen bond acceptors, a 2:1 complex of hydroquinone with the methyl derivative of the terephthalamide forms.4 Bis(N,N-dialkyl)bicyclo[2.2.2]octane-1,4-dicarboxamides behave in a similar fashion, forming 1:1 complexes with the ethyl derivative and 2:1 complexes with the methyl derivative.5 The thermal phase behavior of these systems, as obtained by differential scanning calorimetry, confirms the stoichiometry of these systems.6 To better understand the influences of geometry and crystal packing motifs on physical properties in practical applications such as dissolution kinetics and diffusion control in thin films,7 we have extended this work to explore tris(N,N-dialkyl)trimesamides. The two trimesamide systems used in this study are tris(N,N-diethyl)† ‡ §
University of Massachusetts Lowell. Brandeis University. JEOL USA, Inc.
Figure 1. Crystal packing schematic of 1:1 hydroquinone-bis[N,N-diethyl]terephthalamide.
Figure 2. Crystal packing schematic of 2:1 hydroquinone-bis[N,N-dimethyl]terephthalamide.
trimesamide (2) and tris(N,N-dimethyl)trimesamide (3). These trimesamide systems provide a trigonal planar arrangement of the three hydrogen bond accepting amide functional groups around an aromatic ring.
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Figure 3. Phase diagram for the hydroquinone-tris(N,N-diethyl)trimesamide system. The eutectic compositions were not experimentally determined.
Table 1. Crystallographic Data compound
4
5
chemical formula formula weight crystal system space group T, K a, Å b, Å c, Å β V, Å3 Z Fcalcd, g cm-3 λ, Å µ, mm-1 trans coeff (empirical corr) unique reflections; no. obsd Rmerge R Rw SDU
C30H42N3O6 540.68 monoclinic P21/c 294 14.617(6) 12.448(5) 16.846(7) 95.14(4) 3053(2) 4 1.176 0.71073 0.082 0.96-0.97 3711; 2724 0.034 0.0618 0.0653 1.12
C27H33N3O7 511.58 monoclinic P21/c 294 10.142(6) 14.859(9) 17.662(11) 98.01(6) 2636(3) 4 1.289 0.71073 0.094 0.97-0.98 3213; 2082 0.014 0.0493 0.0480 1.18
Figure 4. Phase diagram for the hydroquinone-tris(N,N-dimethyl)trimesamide system. The eutectic compositions were not experimentally determined.
Experimental Section Hydroquinone 1 was purchased from Aldrich Chemical (Milwaukee, WI) and used without further purification. Tris(N,Ndiethyl)trimesamide 2 and tris(N,N-dimethyl)trimesamide 3 were prepared from 1,3,5-benzene tricarbonyl chloride (Aldrich) and the appropriate secondary amine. Crystallographic quality cocrystals 4 and 5 were prepared by dissolving the correct stoichiometric amounts of components in minimal hot acetonitrile and allowing the solutions to stand at room temperature for 24 h. Initial crystals were collected in 35% yield of 4 and 45% yield of 5. Further cooling of the filtrate to 5 °C allowed for nearly quantitative yields of both cocrystals. Phase diagrams were obtained by plotting endothermic thermal transitions of a number of ratios of components as a function of composition using a TA Instruments model 2920 modulated differential scanning calorimeter following procedures as described previously.6 X-ray Structure Determination of 4 and 5. Routine operations were performed as described previously (Syntex P21 diffractometer at Brandeis University).8 The structures were solved by direct methods (SIR92).9 Full-matrix least-squares refinement was carried out using the Oxford University Crystals for Windows system.10,11 The structures were refined by using anisotropic displacement parameters for N, O, and C atoms. H atoms, except those attached to O (refined by using isotropic displacement parameters), were fixed at calculated positions and updated after each round of least-squares refinement. Crystallographic data are
Figure 5. Molecular structure of 4, showing labeling scheme and 35% probability ellipsoids for atoms refined using anisotropic displacement parameters. The labeled atoms constitute the asymmetric unit (note that the hydroquinone bearing atom O6 is only half-labeled). presented in Table 1. CIF files are available as Supporting Information.
Results and Discussion Hydroquinone and tris(N,N-diethyl)trimesamide form a 3:2 solid-state complex 4 as shown by the phase diagram
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Figure 6. Crystal packing diagram of 3:2 hydroquinone-tris(N,N-diethyl)trimesamide 4. Table 2. Hydrogen Bonds X-H‚‚‚Y operation
D-H
H‚‚‚A
D‚‚‚A
D-H‚‚‚A
Compound 4 O(4)- -H(4)‚‚‚O(1) 0.86(4) 1.89(5) 2.740(4) 169(5) O(5)- -H(5)‚‚‚O(2) 0.96(6) 1.73(6) 2.684(4) 175(5) O(6)- -H(6)‚‚‚O(3) 0.93(6) 1.81(6) 2.727(4) 172(4) O(4)- -H(4)‚‚‚O(1) O(5)- -H(5)‚‚‚O(2) O(6)- -H(6)‚‚‚O(3) O(7)- -H(7)‚‚‚O(6)
1.02(7) 0.87(4) 1.02(7) 0.74(9)
Compound 5 1.73(7) 2.742(4) 1.92(4) 2.751(4) 1.66(7) 2.665(4) 2.10(9) 2.837(4)
170(5) 161(4) 169(5) 171(10)
symmetry
1-x, 1-y, 1-z
2-x, 1-y, -z
(Figure 3). A single unique phase is indicated by a maximum at 60% hydroquinone composition. When the ethyl substituents of the trimesamide are replaced by methyl groups, the phase diagram shows the formation of a 2:1 solid-state complex 5 (Figure 4). In this case, a single unique phase is observed at 66.6% hydroquinone composition. In these systems, similar to the linear bis-hydrogen bond acceptor systems described previously, the concept of steric accommodation appears to provide a significant influence on the packing environment and stoichiometry. Inspection of the structures of these complex systems helps to demonstrate and rationalize this behavior. The molecular structure and labeling scheme of the 3:2 cocrystal 4 of hydroquinone and tris(N,N-diethyl)trimesamide are shown in Figure 5; bond lengths and angles lie within normal
Figure 7. Molecular structure of 5, showing labeling scheme and 35% probability ellipsoids for atoms refined using anisotropic displacement parameters. The labeled atoms constitute the asymmetric unit (note that the hydroquinones bearing atoms O6 and O7 are only half-labeled).
ranges. The asymmetric unit consists of one trimesamide, one hydroquinone, and one half-hydroquinone moieties. The 3:2 assembly 4 is best viewed as a complex, extended hydrogen bond network (Table 2 and Figure 6). There are three unique, discrete hydrogen bonds between the hydroquinone moieties and the three acceptor oxygen atoms
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Figure 8. Crystal packing diagram of 2:1 hydroquinone-tris(N,N-dimethyl)trimesamide 5.
on the trimesamide group. The focal point is the secondary graph set ring, R44(30).12 The centrosymmetric ring is comprised of two hydroquinones and two trimesamides and includes two centrosymmetric pairs of hydrogen bonds (the first two entries in Table 2). Oxygen atoms O(1) and O(2) point toward the ring center. The R44(30) rings are linked in an infinite column along the [1 -1 0] direction by a pair of centrosymmetric O(6)-H(6)‚‚‚O(3) hydrogen bonds to the single trimesamide oxygen atom O(3) which is exo to the R44(30) ring. The molecular structure and labeling scheme of the 2:1 cocrystal 5 of hydroquinone and tris(N,N-dimethyl)trimesamide are shown in Figure 7; bond lengths and angles lie within normal ranges. The asymmetric unit consists of one trimesamide, one hydroquinone, and two half-hydroquinone moieties. Inspection of a packing diagram (Figure 8) first reveals the persistence of the R44(30) ring. The details of the ring construction are very similar to that in 4. Oxygen atoms O(1) and O(2) point toward the ring center and are linked through two centrosymmetric pairs of hydrogen bonds (the first two entries in Table 2, under compound 5). The R44(30) rings are linked in an infinite column along the c axis by a pair of centrosymmetric O(6)-H(6)‚‚‚O(3) hydrogen bonds to the single trimesamide oxygen atom O(3) which is exo to the R44(30) ring. However, there is an additional feature in this structure: owing to the reduced steric influence of the methyl group, an additional hydroquinone is incorporated within the crystalline matrix. As can be readily seen in Figure 8, there is an infinite chain of centrosymmetric O(7)-H(7)‚‚‚O(6) hydrogen bonds between hydroquinone groups along the b axis. The addition of the extra hydroquinone group allows the columnar repeat distance of the R44(30) ring system to be similar for 4 ([1 -1 0], 19.20 Å) and 5 (c, 17.66 Å). Finally, as expected, the full graph set matrices for 4 and 5 are very similar.13,14
The implications of these geometries on the physical properties and kinetics of formation are being investigated. It is hoped that by understanding the structure-activity relationships of these systems it will be possible to design and manipulate materials in a predictable and environmentally benign fashion. Acknowledgment. We thank the Environmental Protection Agency [J.C.W., R825327], Pfizer [J.C.W., 2002], and the National Science Foundation [B.M.F., DMR0089257] for financial support. Supporting Information Available: CIF files for structures of compounds 4 and 5. This material is available free of charge via the Internet at http://pubs.acs.org.
References (1) Warner, J. C. In Green Chemistry: Frontiers in Benign Chemical Synthesis and Processes; Anastas, P., Williamson, T., Eds.; Oxford University Press: London, 1998; pp 336346. (2) Cannon, A. S.; Warner, J. C. Cryst. Growth Des. 2002, 2, 255. (3) Anastas, P. T.; Warner, J. C.; Green Chemistry: Theory and Practice; Oxford University Press: London, 1998. (4) Foxman, B. M.; Guarrera, D. J.; Taylor, L. D.; van Engen, D.; Warner, J. C. Cryst. Eng. 1998, 1, 109. (5) Foxman, B. M.; Guarrera, D. J.; Pai, R.; Tassa, C.; Warner, J. C. Cryst. Eng. 1999, 2, 55. (6) Guarrera, D.; Taylor, L. D.; Warner, J. C. Chem. Mater. 1994, 6, 1293. (7) (a) Guarrera, D. J.; Kingsley, E.; Taylor, L. D.; Warner, J. C. Proceedings of the IS&T’s 50th Annual Conference. The Physics and Chemistry of Imaging Systems; Society for Imaging Science & Technology: Springfield, VA, 1997; p 537. (b) Taylor, L. D.; Warner, J. C. U.S. Patent 5,177,262, 1993. (c) Guarrera, D. J.; Taylor, L. D.; Warner, J. C.
Communications Proceedings of the 22nd NATAS Conference; 1993; p 496. (d) Taylor, L. D.; Warner, J. C. U.S. Patent 5,338,644, 1994. (8) (a) Foxman, B. M. Inorg. Chem. 1978, 17, 1932. (b) Foxman, B. M.; Mazurek, H. Inorg. Chem. 1979, 18, 113. (c) MolEN, An Interactive Structure Solution Procedure; Enraf-Nonius: Delft, The Netherlands, 1990. (9) Altomare, A.; Cascarano, G.; Giacovazzo, G.; Guagliardi, A.; Burla, M. C.; Polidori, G.; Camalli, M. J. Appl. Cryst. 1994, 27, 435. (10) Betteridge, P. W.; Carruthers, J. R.; Cooper, R. I.; Prout, K.; Watkin, D. J. J. Appl. Crystallogr. 2003, 36, 1487.
Crystal Growth & Design, Vol. 5, No. 2, 2005 411 (11) Watkin, D. J.; Prout, C. K.; Pierce, L. A. CAMERON; Chemical Crystallographic Laboratory, University of Oxford: Oxford, 1996. (12) Etter, M. C.; MacDonald, J. C.; Bernstein, J. Acta Crystallogr., Sect. B 1990, 46, 256. (13) Bernstein, J.; Davis, R. E.; Shimoni, L.; Chang, N. L. Angew. Chem., Int. Ed. 1995, 34, 1555. (14) Motherwell, W. D. S.; Shields, G. P.; Allen, F. H. Acta Crystallogr., Sect. B 2000, 56, 466.
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