Engineering Hydrogen-Bonded Molecular Crystals Built from1,3,5-Substituted Derivatives of Benzene:6,6′,6′′ -(1,3,5-Phenylene)tris-1,3,5-triazine-2,4-diamines

Fatima Helzy, Thierry Maris, and James D. Wuest*

Département de Chimie, UniVersité de Montréal, Montréal, Québec H3C 3J7 Canada

ReceiVed August 23, 2007; ReVised Manuscript ReceiVed January 31, 2008

ABSTRACT: In 6,6′,6′′ -(1,3,5-phenylene)tris-1,3,5-triazine-2,4-diamine, three trigonally directed diaminotriazinyl groups are attachedto the 1,3,5-positions of a phenyl core. This introduces a significant capacity for intermolecular hydrogen bonding, because eachdiaminotriazinyl group can normally interact with two others to form a total of four hydrogen bonds. Derivatives 3 and 4, whichhave alkyl groups at the 2,4,6-positions, are designed to favor a conformation in which the diaminotriazinyl groups are heldperpendicular to the phenyl core. This conformation is expected to direct the hydrogen bonding of each diaminotriazinyl group outof the plane of the phenyl core, leading to generation of a three-dimensional (3D) network in which each molecule is linked to sixneighbors by a total of 12 hydrogen bonds. In fact, the observed networks all show a lower degree of connectivity, possibly becausethe cores of compounds 3 and 4 are too compact to accommodate six fully hydrogen-bonded neighbors. Nevertheless, compounds3 and 4 have the following attractive features: (1) They have a well-defined molecular geometry that places multiple sites of hydrogenbonding in a predictable orientation, leading to the construction of 3D networks in which neighboring molecules are positionedlogically by directional forces; and (2) their topologies make efficient packing difficult and favor open networks with significantvolume available for the inclusion of guests. For these reasons, compounds with diaminotriazinyl groups attached to suitably substitutedaryl cores are promising subunits for engineering crystals and other ordered molecular materials with novel structures and properties.

Introduction

Crystal engineering, which seeks to control the structures andproperties of crystals, offers challenges and opportunities thatmake the field an exceptionally exciting area of contemporaryscience.1 In particular, crystal engineering is an increasinglypowerful tool for reaching the visionary goal articulated byFeynman almost 50 years ago: ”What would the properties ofmaterials be if we could really arrange the atoms the way wewant them? They would be very interesting to investigatetheoretically. I cannot see exactly what would happen, but Ican hardly doubt that when we have some control of thearrangement of things on a small scale we will get anenormously greater range of possible properties that substancescan have, and of different things that we can do.”2

Even after decades of research, however, predictions of thedetailed structures and properties of crystals by theoreticalmethods are not in general reliable.3–5 Nevertheless, importantalternative strategies have emerged for producing crystals bydesign. As summarized by Dunitz in a recent review,3 “From amore qualitative and descriptive viewpoint has come the notionthat certain groupings in organic molecules exercise attractiveintermolecular interactions and so guide the molecules intodistinctive patterns in their crystal structures. . .This has indeedbecome one of the tenets of crystal engineering.” An importantdegree of control over atomic arrangements can thereby beattained by building crystals from molecular subunits that havewell-defined geometries and an ability to hold neighboringmolecules in predetermined positions by engaging in strongdirectional interactions.6–8 Such subunits for planned molecularconstruction, which have been called tectons,9 can be madeconveniently by choosing functional groups that engage inreliable patterns of molecular association, which have beencalled supramolecular synthons,10 and then by attaching them

to cores that orient the sticky sites properly and introduce otherdesired features.

An archetypal tecton is 1,3,5-benzenetricarboxylic acid(1),11,12 which incorporates three COOH groups oriented

* Author to whom correspondence may be addressed: james.d.wuest@umontreal.ca.

Figure 1. Representation of the planar hexagonal network I built from1,3,5-benzenetricarboxylic acid (1), with 1,3,5-trisubstituted phenylgroups represented by triangles and hydrogen bonds shown as brokenlines.

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trigonally by a rigid core. Tecton 1 is programmed to generateplanar hexagonal network I (Figure 1) by normal intermolecularassociation of the -COOH groups as cyclic hydrogen-bondedpairs.

Although the architecture of the sheets typically arisesaccording to plan, the design has two notable shortcomings:(1) Each tecton participates in only six hydrogen bonds, so theresulting network is not highly robust; and (2) the relativeorientation of adjacent sheets is hard to foresee because it isnot controlled by strong directional forces.

To eliminate the first shortcoming, we decided to replace the-COOH groups of 1,3,5-benzenetricarboxylic acid (1) by 2,4-diamino-1,3,5-triazinyl groups, which are known to formmultiple hydrogen bonds according to motifs II-IV (Figure2).7 Motif II is the most frequently observed of these alterna-tives, presumably because it incorporates hydrogen bonds remote

Figure 2. Hydrogen-bonding motifs typically formed by diaminotri-azinyl groups.

Figure 3. View of the structure of crystals of tecton 3 grown fromDMSO/chlorobenzene. A central molecule of tecton 3 is shown in red,and the four neighboring molecules that engage in hydrogen bondingaccording to motif IV (Figure 2) are drawn with carbon atoms in gray,hydrogen atoms in white, and nitrogen atoms in blue. Hydrogen bondsare represented by broken lines. In all these bonds, the N · · ·H distancesare less than 2.6 Å.

Figure 4. Representation of the corrugated four-connected hydrogen-bonded sheets found in the structure of crystals of tecton 3 grown fromDMSO/chlorobenzene. The centroid of each molecule of tecton 3 isshown as a red or blue sphere, and the lines connecting each sphere tofour adjacent spheres correspond to the intertectonic hydrogen bondsshown in detail in Figure 3.

Figure 5. Side view of a single corrugated sheet in the structure ofcrystals of tecton 3 grown from DMSO/chlorobenzene, showing howdiaminotriazinyl groups not involved in intertectonic hydrogen bondingare oriented above and below the sheets in alternation. Molecules oftecton 3 are drawn with all atoms in red or in pink, and hydrogen bondsare represented by broken lines.

Figure 6. View of the structure of crystals of tecton 3 grown fromDMSO/chlorobenzene, showing how diaminotriazinyl groups notinvolved in direct intertectonic hydrogen bonding interact withincluded molecules of DMSO and H2O. A central molecule of tecton3 is shown in red, and hydrogen-bonded neighbors are drawn withcarbon atoms in gray, hydrogen atoms in white, nitrogen atoms inblue, oxygen atoms in red, and sulfur atoms in yellow. Hydrogenbonds are represented by broken lines.

1548 Crystal Growth & Design, Vol. 8, No. 5, 2008 Helzy et al.

from the sterically congested site where the diaminotriazinylgroup is attached to the molecular core. Overcoming the secondshortcoming cannot be achieved simply by attaching diamino-triazinyl groups in place of -COOH groups to create tris(di-aminotriazine) 2. 2-Phenyl-1,3,5-triazines are known to favorconformations in which the phenyl and triazinyl rings are nearlycoplanar,7 so we expected that the ability of tecton 2 to engagein multiple hydrogen bonds would be limited largely to a singleplane, thereby leading again to the formation of parallel sheetswith no dominant interconnections. We elected to solve thisproblem by making derivatives 3 and 4, in which substituentsare introduced at the 2,4,6-positions to force the neighboringtriazinyl groups out of the plane of the aromatic core, allowingthem to use part of their capacity for hydrogen bonding tocontrol cohesion of the primary sheets. In this way, we hopedto obtain three-dimensional (3D) hydrogen-bonded networksbuilt by interconnecting hexagonal sheets.

Results and Discussion

Synthesis of Tectons 3 and 4. Methyl- and ethyl-substitutedcompounds 3 and 4 were synthesized in 84 and 86% yields,

respectively, by treating the known trinitriles 513 and 612 withdicyandiamide and KOH under standard conditions.14

Structure of Crystals of Tecton 3 Grown from DMSO/Chlorobenzene. Exposing a solution of tecton 3 in DMSO tovapors of chlorobenzene induced the formation of crystals ofcomposition 3 ·4DMSO ·2H2O.15 The crystals proved to belongto the orthorhombic space group P212121. Views of the structureappear in Figures 3–7, and crystallographic details are providedin Table 1. As planned, tecton 3 adopts a conformation in whichthe average planes of the 1,3,5-trisubstituted phenyl core andthe three triazinyl rings are nearly orthogonal (84.2(2)°, 81.9(2)°,and 81.4(2)°). Unexpectedly, however, only two of the triazinylgroups engage in intertectonic hydrogen bonding, and they favormotif IV (Figure 2). In this way, each tecton forms a total ofeight hydrogen bonds with four neighboring tectons (Figure 3),thereby creating corrugated sheets (Figure 4). The third triazinylgroup of each tecton is directed perpendicular to the sheets, ina orientation opposite to that of the corresponding groups ofthe four hydrogen-bonded neighbors (Figure 5). Diaminotriazi-nyl groups not involved in the construction of sheets formhydrogen bonds with included DMSO and H2O (Figure 6),which separate adjacent sheets (Figure 7). Approximately 56%of the volume of the crystals is available for the inclusion ofguests, as estimated by standard methods.16,17 The large fractionof accessible volume in crystals of compound 3 reflects thetendency of tectons to respect the normal geometric preferencesof strong intermolecular interactions, even when they forcepacking to become inefficient. Removal of the crystals fromthe mother liquors led to rapid decomposition through loss ofincluded guests.

Structure of Crystals of Tecton 3 Grown from DMSO/Toluene. By exposing a solution of tecton 3 in DMSO to vaporsof toluene, we obtained crystals of approximate composition3 ·1DMSO ·2toluene ·g2H2O.15 The crystals were found tobelong to the triclinic space group P1j. Views of the structureappear in Figures 8–11, and crystallographic details are providedin Table 1. Again, tecton 3 adopts the expected conformation,with nearly orthogonal average planes of the 1,3,5-trisubstitutedphenyl core and the three triazinyl rings (68.2(1)°, 83.1(1)°, and80.5(1)°). Crystals grown from DMSO/chlorobenzene andDMSO/toluene proved to have similar compositions and relatedstructures, despite the difference in space groups. In crystals

Figure 7. View of the structure of crystals of tecton 3 grown from DMSO/chlorobenzene, showing three adjacent hydrogen-bonded sheets in red andblue. Included molecules of DMSO and H2O occupy spaces between thesheets. Atoms are represented by spheres of van der Waals radii.

Table 1. Crystallographic Data for Tectons 3 and 4

compound 3 ·4DMSO ·2H2O 3 ·2H2Oa 4 ·4DMSO ·3H2O

formula C26H49N15O6S4 C18H25N15O2 C29H57N15O7S4

MW 796.04 483.53 856.14crystal system orthorhombic triclinic triclinicspace group P212121 P1j P21

a (Å) 11.905(5) 10.8239(5) 11.8963(2)b (Å) 12.714(5) 12.0117(7) 13.2249(3)c (Å) 27.347(10) 15.8500(9) 14.5323(2)R (°) 90 79.084(4) 90� (°) 90 86.515(4) 102.435(1)γ (°) 90 69.273(3) 90V (Å3) 4139(3) 1892.4(2) 2232.69(7)Z 4 2 2T (K) 226(2) 223(2) 295(2)Fcalc (g cm-3) 1.277 0.849b 1.273λ (Cu KR Å) 1.54178 1.54178 1.54178µ (Cu KR mm-1) 2.577 0.511 2.441R1, I > 2σ(I) (all) 0.0684 (0.0931) 0.0766 (0.0920) 0.0687 (0.0892)wR2, I > 2σ(I) (all) 0.1624 (0.1743) 0.2099 (0.2256) 0.1803 (0.2134)measured reflections 47133 19111 26985independent reflections 8134 7419 4647

a Guests not identified unambiguously by crystallography are omitted from the composition; see Supporting Information. b Calculated withoutcontribution from guests.

6,6′,6′′ -(1,3,5-Phenylene)tris-1,3,5-triazine-2,4-diamines Crystal Growth & Design, Vol. 8, No. 5, 2008 1549

grown from DMSO/toluene, each molecule of tecton 3 againuses two of its three diaminotriazinyl groups to form eightnormal hydrogen bonds with four neighbors, thereby definingsheets similar to those observed in crystals grown from DMSO/chlorobenzene (Figure 8). In crystals grown from DMSO/toluene, however, each of the two diaminotriazinyl groupssimultaneously engages in hydrogen bonding according to motifsII and IV, whereas crystals grown from DMSO/chlorobenzeneshow only motif IV. Moreover, in crystals grown from DMSO/toluene, each molecule of tecton 3 uses the diaminotriazinyl

group not involved in the formation of sheets to donate anadditional single hydrogen bond to a triazinyl group in anadjacent sheet (Figure 9).18 This raises the total of intertectonichydrogen bonds per tecton to 10, and it links the individualsheets to form a 3D network (Figure 10). Approximately 52%of the volume of the crystals is available for the inclusion ofguests,16 which are highly disordered and occupy parallelchannels with cross sections that measure approximately 5 ×15 Å and run along the a-axis (Figure 11). Loss of these guestsoccurred readily when crystals were removed from their motherliquors.

Structures of Crystals of Tecton 4 Grown from DMSO/Toluene. Exposing a solution of ethyl-substituted tecton 4 inDMSO to vapors of toluene induced the formation of crystalsof composition 4 ·4DMSO ·3H2O.15 The crystals proved tobelong to the triclinic space group P21. Views of the structureappear in Figures 12 and 13, and crystallographic details areprovided in Table 1. Like methyl-substituted analogue 3, ethyl-substituted compound 4 favors a conformation in which theaverage planes of the 1,3,5-trisubstituted phenyl core and thethree triazinyl rings are approximately orthogonal (89.2(1)°,78.9(1)°, and 86.7(1)°). Two of the three diaminotriazinyl groupsof each molecule of tecton 4 form a total of eight hydrogenbonds with four neighbors according to motif IV (Figures 2and 12). This yields parallel corrugated four-connected sheetsessentially identical to those found in crystals of tecton 3 grownfrom DMSO/chlorobenzene (Figure 4). Diaminotriazinyl groupsnot involved in the construction of sheets form hydrogen bondswith included DMSO and H2O (Figure 13). Approximately 54%

Figure 8. View of the structure of crystals of tecton 3 grown from DMSO/toluene. A central molecule of tecton 3 is shown in red, two neighboringmolecules that engage in hydrogen bonding according to motif II (Figure 2) are drawn in green, and two other neighbors that form hydrogen bondsof type IV appear in yellow. Hydrogen bonds are represented by broken lines. In all these bonds, the N · · ·H distances are less than 2.6 Å.

Figure 9. View of the structure of crystals of tecton 3 grown from DMSO/toluene. A central molecule of tecton 3 is shown in red, and twoneighboring molecules in adjacent sheets that are connected to the central tecton by single hydrogen bonds are drawn in blue. Hydrogen bonds arerepresented by broken lines. In these bonds, the N · · ·H distances are less than 2.6 Å, and all other N · · ·H distances between the central tecton andits blue neighbors exceed 2.8 Å.

Figure 10. Representation of the six-connected 3D hydrogen-bondednetwork observed in crystals of tecton 3 grown from DMSO/toluene.The centroid of each molecule of tecton 3 is shown as a red or bluesphere. Red or blue lines corresponding to normal intertectonic hydrogenbonds of types II and IV (Figures 2 and 8) connect each sphere tofour adjacent spheres, thereby defining corrugated sheets similar to thoseshown in Figure 4. Lines that are half-red and half-blue represent singleintertectonic hydrogen bonds (Figure 9) and connect each sphere totwo others in adjacent sheets, creating a 3D network.

1550 Crystal Growth & Design, Vol. 8, No. 5, 2008 Helzy et al.

of the volume of the crystals is accessible to guests, as estimatedby standard methods.16

Conclusions

Tectons 3 and 4 are designed to hold trigonally directeddiaminotriazinyl groups perpendicular to an aromatic core. Inprinciple, this conformation should favor the assembly of 3D

hydrogen-bonded networks instead of 2D alternatives normallyfavored by planar trigonal tectons such as 1,3,5-benzenetricar-boxylic acid (1). As confirmed by analysis of crystals grownunder various conditions, tectons 3 and 4 reliably adopt theexpected conformation. This conformation, when combined withthe potential of each diaminotriazinyl group to participate infour hydrogen bonds according to established motifs II-IV(Figure 2), could give rise to 3D networks in which each tectonforms a total of 12 hydrogen bonds with six neighbors. In fact,the observed structures all show a lower degree of hydrogenbonding, possibly because the 1,3,5-trisubstituted phenyl coresof tectons 3 and 4 are too compact to accommodate six fullyhydrogen-bonded neighbors. Inclusion of DMSO and H2O inall structures presumably helps compensate by allowing diami-notriazinyl groups to form additional hydrogen bonds withmolecules smaller than tectons 3 and 4.

Tectons 3 and 4 fail to fully exploit their potential forhydrogen bonding according to motifs II-IV. Nevertheless,their behavior reveals the following attractive features: (1) Theyhave predictable molecular geometries; (2) they incorporatemultiple sites of association that are reliably directed above,below, and within the plane of the aryl core, thereby allowingthe construction of 3D networks in which neighboring moleculesare positioned by directional forces; and (3) their complexnonplanar topologies make efficient packing difficult, leadingto the formation of open networks with significant volumeavailable for the inclusion of guests. For these reasons, tectonswith diaminotriazinyl groups attached to suitably substituted arylcores are promising subunits for engineering crystals and otherordered molecular materials with novel structures and properties.

Experimental Section

6,6′,6′′ -(2,4,6-Trimethyl-1,3,5-phenylene)tris-1,3,5-triazine-2,4-di-amine (3). A mixture of 2,4,6-trimethyl-1,3,5-benzenetricarbonitrile (5;0.580 g, 2.97 mmol),13 dicyandiamide (3.03 g, 36.0 mmol), andpowdered KOH (0.396 g, 7.06 mmol) in 2-methoxyethanol (40 mL)

Figure 11. Representation of the structure of crystals of tecton 3 grownfrom DMSO/toluene, showing a 3 × 4 × 3 array of unit cells viewedapproximately along the a-axis. Guests are omitted for clarity, and atomsare represented by spheres of van der Waals radii to show the crosssections of channels. Atoms of hydrogen appear in white, carbon ingray, and nitrogen in blue.

Figure 12. View of the structure of crystals of tecton 4 grown from DMSO/toluene. A central molecule of tecton 4 is shown in red, and thefour neighboring molecules that engage in hydrogen bonding according to motif IV (Figure 2) are drawn with carbon atoms in gray, hydrogenatoms in white, and nitrogen atoms in blue. Hydrogen bonds are represented by broken lines. In all these bonds, the N · · ·H distances are lessthan 2.6 Å.

6,6′,6′′ -(1,3,5-Phenylene)tris-1,3,5-triazine-2,4-diamines Crystal Growth & Design, Vol. 8, No. 5, 2008 1551

was heated at reflux for 12 h. The resulting mixture was cooled, and asolid was separated by filtration. The solid was washed thoroughly withhot H2O, rinsed with CH3OH, and dried in vacuo to give a pure sampleof 6,6′,6′′ -(2,4,6-trimethyl-1,3,5-phenylene)tris-1,3,5-triazine-2,4-di-amine (3; 1.11 g, 2.48 mmol, 84%) as a colorless solid: IR (KBr) 3323,3184, 2980, 2880, 1637, 1541, 1445, 1365, 1253, 1122, 1080, 1034,997, 829, 787 cm-1; 1H NMR (400 MHz, DMSO-d6, 293 K) δ 6.66(s, 12H), 1.85 (s, 9H); 13C NMR (100.5 MHz, DMSO-d6, 293 K) δ175.72, 168.08, 138.09, 130.35, 17.57; HRMS (FAB, 3-nitrobenzylalcohol) calcd for C18H22N15 + H m/e 448.2183, found 448.2158.

6,6′,6′′ -(2,4,6-Triethyl-1,3,5-phenylene)tris-1,3,5-triazine-2,4-di-amine (4). An analogous reaction transformed 2,4,6-triethyl-1,3,5-benzenetricarbonitrile (6; 0.710 g, 2.99 mmol)12 into 6,6′,6′′ -(2,4,6-triethyl-1,3,5-phenylene)tris-1,3,5-triazine-2,4-diamine (4; 1.26 g, 2.57mmol, 86%), which was isolated as a colorless solid: IR (KBr) 3330,3140, 1641, 1531, 1450, 1360, 1258, 1026, 991, 906, 829 cm-1; 1HNMR (400 MHz, DMSO-d6, 293 K) δ 6.67 (s, 12H), 2.28 (q, 3J ) 7.4Hz, 6H), 0.95 (t, 3J ) 7.4 Hz, 9H); 13C NMR (100.5 MHz, DMSO-d6,293 K) δ 175.80, 167.78, 137.55, 137.09, 24.72, 16.39; HRMS (FAB,3-nitrobenzyl alcohol) calcd for C21H28N15 + H m/e 490.2652, found490.2673.

X-Ray Crystallographic Studies. Data were collected using aBruker AXS SMART 2K/Platform diffractometer. Structures weresolved by direct methods using SHELXS-97 and refined usingSHELXL-97.19 All non-hydrogen atoms were refined anisotropically,whereas hydrogen atoms were placed in ideal positions and defined asriding atoms.

Acknowledgment. We are grateful to the Natural Sciencesand Engineering Research Council of Canada, the Ministère del′Éducation du Québec, the Canada Foundation for Innovation,the Canada Research Chairs Program, and Université deMontréal for financial support.

Supporting Information Available: Additional crystallographicdetails, including ORTEP drawings and tables of structural data in CIFformat. This material is available free of charge via the Internet at http://pubs.acs.org.

References

(1) (a) Braga, D. Chem. Commun. 2003, 275, 1–2754. (b) Biradha, K.CrystEngComm 2003, 5, 374–384. (c) Hollingsworth, M. D. Science2002, 295, 2410–2413. (d) Crystal Engineering: From Molecules andCrystals to Materials; Braga, D.; Grepioni, F.; Orpen, A. G., Eds.;Kluwer: Dordrecht, Netherlands, 1999. (e) Desiraju, G. R. CrystalEngineering: The Design of Organic Solids; Elsevier: Amsterdam,1989.

(2) Taken from a lecture given by Richard Feynman on December 29,1959, at the annual meeting of the American Physical Society at theCalifornia Institute of Technology (Caltech). The lecture, entitled“There’s Plenty of Room at the Bottom: An Invitation to Enter a NewField of Physics”, was first published in the February 1960 issue ofCaltech’s Engineering and Science.

(3) Dunitz, J. D. Chem. Commun. 2003, 545–548.(4) (a) Desiraju, G. R. Nat. Mater. 2002, 1, 77–79. (b) Gavezzotti, A.

Acc. Chem. Res. 1994, 27, 309–314. (c) Maddox, J. Nature 1988, 335,201.

(5) For an example of recent progress, see Trolliet, C.; Poulet, G.; Tuel,A.; Wuest, J. D.; Sautet, P. J. Am. Chem. Soc. 2007, 129, 3621–3626.

(6) (a) For overviews of the strategy, see Wuest, J. D. Chem. Commun.2005, 5830–5837. (b) Hosseini, M. W. Acc. Chem. Res. 2005, 38,313–323.

(7) Maly, K. E.; Gagnon, E.; Maris, T.; Wuest, J. D. J. Am. Chem. Soc.2007, 129, 4306–4322.

(8) (a) For other recent references, see Roques, N.; Maspoch, D.; Wurst,K.; Ruiz-Molina, D.; Rovira, C.; Veciana, J. Chem. Eur. J. 2006, 12,9238–9253. (b) Sokolov, A. N.; Frišcic, T.; MacGillivray, L. R. J. Am.Chem. Soc. 2006, 128, 2806–2807. (c) Pigge, F. C.; Dighe, M. K.;Rath, N. P. Cryst. Growth Des. 2006, 6, 2732–2738. (d) Saha, B. K.;Nangia, A.; Nicoud, J.-F. Cryst. Growth Des. 2006, 6, 1278–1281.(e) Jayaraman, A.; Balasubramaniam, V.; Valiyaveettil, S. Cryst.Growth Des. 2006, 6, 636–642. (f) Suslick, K. S.; Bhyrappa, P.; Chou,J.-H.; Kosal, M. E.; Nakagaki, S.; Smithenry, D. W.; Wilson, S. R.Acc. Chem. Res. 2005, 38, 283–291. (g) Aakeröy, C. B.; Desper, J.;Urbina, J. F. Chem. Commun. 2005, 2820–2822. (h) Braga, D.;Brammer, L.; Champness, N. R. CrystEngComm 2005, 7, 1–19. (i)Sisson, A. L.; del Amo Sanchez, V.; Magro, G.; Griffin, A. M. E.;Shah, S.; Charmant, J. P. H.; Davis, A. P. Angew. Chem., Int. Ed.2005, 44, 6878–6881. (j) Malek, N.; Maris, T.; Perron, M.-È.; Wuest,J. D. Angew. Chem., Int. Ed. 2005, 44, 4021–4025. (k) Voogt, J. N.;Blanch, H. W. Cryst. Growth Des. 2005, 5, 1135–1144. (l) Lee, S.-O.; Shacklady, D. M.; Horner, M. J.; Ferlay, S.; Hosseini, M. W.;Ward, M. D. Cryst. Growth Des. 2005, 5, 995–1003. (m) Custelcean,R.; Gorbunova, M. G.; Bonnesen, P. V. Chem. Eur. J. 2005, 11, 1459–1466. (n) Moorthy, J. N.; Natarajan, R.; Venugopalan, P. J. Org. Chem.2005, 70, 8568–8571. (o) Saied, O.; Maris, T.; Wang, X.; Simard,M.; Wuest, J. D. J. Am. Chem. Soc. 2005, 127, 10008–10009. (p)Malek, N.; Maris, T.; Simard, M.; Wuest, J. D. J. Am. Chem. Soc.2005, 127, 5910–5916. (q) Soldatov, D. V.; Moudrakovski, I. L.;Ripmeester, J. A. Angew. Chem., Int. Ed. 2004, 43, 6308–6311. (r)Alshahateet, S. F.; Nakano, K.; Bishop, R.; Craig, D. C.; Harris,K. D. M.; Scudder, M. L. CrystEngComm 2004, 6, 5–10.

(9) Simard, M.; Su, D.; Wuest, J. D. J. Am. Chem. Soc. 1991, 113, 4696–4697.

(10) (a) Nangia, A.; Desiraju, G. R. Top. Curr. Chem. 1998, 198, 57–95.(b) Desiraju, G. R. Angew. Chem., Int. Ed. 1995, 34, 2311–2327.

(11) Herbstein, F. H. In ComprehensiVe Supramolecular Chemistry; At-wood, J. L., Davies, J. E. D., MacNicol, D. D., Vögtle, F., Eds.;Pergamon: Oxford, UK, 1996; Vol. 6, pp 61–83..

(12) Kolotuchin, S. V.; Thiessen, P. A.; Fenlon, E. E.; Wilson, S. R.;Loweth, C. J.; Zimmerman, S. C. Chem. Eur. J. 1999, 5, 2537–2547.

(13) (a) Hou, Z.; Stack, T. D. P.; Sunderland, C. J.; Raymond, K. N. Inorg.Chim. Acta 1997, 263, 341–355. (b) Gibson, G. K. J. Chem. Ind. 1981,649–650. (c) Weis, C. D. J. Org. Chem. 1962, 27, 2964–2965.

(14) Simons, J. K.; Saxton, M. R. Organic Syntheses; Wiley: New York,1963; Collect. Vol. IV, p 78.

(15) When guests were ordered, compositions were determined by X-raycrystallography and confirmed by 1H NMR spectroscopy ofdissolved samples. The composition of crystals containing disor-dered guests was estimated using crystallographic data but was notdetermined precisely.

Figure 13. View of the structure of crystals of tecton 4 grown fromDMSO/toluene, showing how diaminotriazinyl groups not involved indirect intertectonic hydrogen bonding interact with included moleculesof DMSO and H2O. A central molecule of tecton 4 is shown in red,and hydrogen-bonded neighbors are drawn with carbon atoms in gray,hydrogen atoms in white, nitrogen atoms in blue, oxygen atoms in red,and sulfur atoms in yellow. Hydrogen bonds are represented by brokenlines.

1552 Crystal Growth & Design, Vol. 8, No. 5, 2008 Helzy et al.

(16) The percentage of volume accessible to guests was estimated bythe PLATON program.17 PLATON calculates the accessible volumeby allowing a spherical probe of variable radius to roll over thevan der Waals surface of the network. PLATON uses a defaultvalue of 1.20 Å for the radius of the probe, which is an appropriatemodel for small guests such as water. The van der Waals radiiused to define surfaces for these calculations are C: 1.70 Å, H:1.20 Å, and N: 1.55 Å. The percentage of accessible volume isgiven by 100Vg/V, where V is the volume of the unit cell and Vg isthe guest-accessible volume as calculated by PLATON.

(17) (a) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool;Utrecht University: Utrecht, The Netherlands, 2001. (b) van der Sluis,P.; Spek, A. L. Acta Crystallogr. 1990, A46, 194–201.

(18) All other intermolecular N · · ·H distances exceed 2.8 Å and cannot beconsidered to involve hydrogen bonding.

(19) Sheldrick, G. M. Program for the Solution of Crystal Structures andSHELXL-97, Program for the Refinement of Crystal Structures;Universität Göttingen: Germany, 1997.

CG700798Z

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