Crystal structure of beta-cyclodextrin-dimethylsulfoxide inclusion complex

beta-Cyclodextrin (beta-CD) crystallizes from 27% DMSO-water as beta-CD.0.5DMSO.7.35H(2)O in the monoclinic space group P2(1) with unit cell constants: a=15.155(1), b=10.285(1), c=20.906(1) A, beta=109.86(1) degrees. Anisotropic refinement of 888 atomic parameters against 9,127 X-ray diffraction data converged at an R-factor of 0.055. The beta-CD macrocycle adopts a 'round' conformation stabilized by intramolecular, interglucose O-3(n) triplebond O-2(n+1) hydrogen bonds. In the beta-CD cavity, DMSO, water sites W-1, W-3 (occupancies 0.5, 0.25, 0.75) are not located concurrently with the water site W-2 because the interatomic distances to W-2 are too short (1.56-1.75 A). DMSO is placed in the beta-CD cavity such that its S-atom is shifted from the O-4 plane center to the beta-CD O-6-side ca. 0.9 A and the C-S bond which is inclined 13.6 degrees to the beta-CD molecular axis. It is maintained in position by hydrogen bonding to water site W-3 and the O-31-H group. 7.35 water molecules are extensively disordered in 13 positions both inside (W-1-W-4) and outside (W-5-W-13) the beta-CD cavity. They act as hydrogen bonding mediators contributing significantly to the stability of the crystal structure.     

Crystalline beta-cyclodextrin.12H2O reversibly dehydrates to beta-cyclodextrin.10.5 H2O under ambient conditions.

In contact with mother liquor, crystalline beta-cyclodextrin (beta-CD) hydrate has composition approximately beta-CD.12H2O. If crystals are dried at ambient conditions (18 degrees C, approximately 50% humidity), the unit cell volume diminishes approximately 30 to 50 A3. X-ray structure analysis of a dry crystal (0.89 A resolution, 4617 data, R = 0.059) showed the composition beta-CD.10.5 H2O, with approximately 5.5 water molecules in the beta-CD cavity (7 partially and 2 fully occupied sites) and approximately 5.0 between the beta-CD molecules. The positions of the beta-CD host and of most of the hydration waters are conserved during dehydration, but the occupancies of the waters in the beta-CD cavity diminish. Dry crystals put into solvent re-hydrate to the original form. The mechanism of de- and re-hydration is not evident.     

A new crystal form of beta-cyclodextrin-ethanol inclusion complex: channel-type structure without long guest molecules

A new crystal form of beta-cyclodextrin (beta-CD)[bond]ethanol[bond]dodecahydrate inclusion complex [(C(6)H(10)O(5))(7).0.3C(2)H(5)OH.12H(2)O] belongs to monoclinic space group C2 (form II) with unit cell constants a=19.292(1), b=24.691(1), c=15.884(1) A, beta=109.35(1) degrees. The beta-CD macrocycle is more circular than that of the complex in space group P2(1) [form I: J. Am. Chem. Soc. 113 (1991) 5676]. In form II, a disordered ethanol molecule (occupancy 0.3) is placed in the upper part of beta-CD cavity (above the O-4 plane) and is sustained by hydrogen bonding to water site W-2. In form I, an ethanol molecule located below the O-4-plane is well ordered because it hydrogen bonds to surrounding O-3[bond]H, O-6[bond]H groups of the symmetry-related beta-CD molecules. In the crystal lattice of form I, beta-CD macrocycles are stacked in a typical herringbone cage structure. By contrast, the packing structure of form II is a head-to-head channel that is stabilized at both O-2/O-3 and O-6 sides of each beta-CD by direct O(CD)...O(CD) and indirect O(CD)...O(W)...(O(W))...O(CD) hydrogen bonds. The 12 water molecules are disordered in 18 positions both inside the channel-like cavity of beta-CD dimer (W-1[bond]W-6) and in the interstices between the beta-CD macrocycles (W-7[bond]W-18). The latter forms a cluster that is hydrogen bonded together and to the neighboring beta-CD O[bond]H groups.     

Crystal form III of beta-cyclodextrin-ethanol inclusion complex: layer-type structure with dimeric motif

The crystal form III of the beta-cyclodextrin (beta-CD)-ethanol inclusion complex [2(C(6)H(10)O(5))(7).1.5C(2)H(5)OH.19H(2)O] belongs to the triclinic space group P1 with unit cell constants: a=15.430(1), b=15.455(1), c=17.996(1)A, alpha=99.30(1) degrees , beta=113.18(1) degrees , gamma=103.04(1) degrees . beta-CD forms dimers comprising two identical monomers that adopt a 'round' conformation stabilized by intramolecular, interglucose O-3(n)cdots, three dots, centeredO-2(n+1) hydrogen bonds. The two beta-CD monomers of form III are isostructural to that of form I in the monoclinic space group P2(1) [Steiner, T.; Mason, S. A.; Saenger, W. J. Am. Chem. Soc.1991, 113, 5676-5687], but exhibit a striking difference from that of form II in the monoclinic space group C2 [Aree, T.; Chaichit, N. Carbohydr. Res.2003, 338, 1581-1589]. The small guest EtOH molecule orients differently in the large beta-CD cavity. In form III, two disordered EtOH molecules are embedded in the beta-CD-dimer cavity. A half occupied EtOH molecule (#1) is located above the O-4 plane of beta-CD #1, whereas another doubly disordered EtOH molecule (#2, #3) is situated at about the middle of the beta-CD-dimer cavity. The three EtOH sites are maintained in positions by making van der Waals contacts to each other and to the surrounding water sites and beta-CD O-3-H group. The EtOH molecules disordered (occupancy 0.3) above the beta-CD O-4 plane in form I and fully occupied beneath the O-4 plane in form II are strongly held in positions by hydrogen bonding with the surrounding water site and beta-CD O-6-H, O-3-H groups. Occurrence of the beta-CD dimer as a structural motif of channel-type packing (form II) and layer-type packing (form III) is attributed to the higher tendency for self aggregation under the moderate acidic conditions. At weak acidic conditions, beta-CD prefers a herringbone mode (form I).     

Crystal structure of beta-cyclodextrin-benzoic acid inclusion complex

The inclusion complex of beta-cyclodextrin (beta-CD) with benzoic acid (BA) has been characterized crystallographically. Two beta-CDs cocrystallize with two BAs, 0.7 ethanol and 20.65 water molecules [2(C(6)H(10)O(5))(7).2(C(7)H(6)O(2)).0.7(C(2)H(6)O).20.65H(2)O] in the triclinic space group P1 with unit cell constants: a=15.210(1), b=15.678(1), c=15.687(1) A, alpha=89.13(1), beta=74.64(1), gamma=76.40(1) degrees. The anisotropic refinement of 1840 atomic parameters against 16,201 X-ray diffraction data converged at R=0.078. In the crystal lattice, beta-CD forms dimers stabilized by direct O-2(m)_1/O-3(m)_1...O-2(n)_2/O-3(n)_2 hydrogen bonds (intradimer) and by indirect O-6(m)_1...,O-6(n)_2 hydrogen bonds with one or two bridging water molecules joined in between (interdimer). These dimers are stacked like coins in a roll constructing endless channels where the guest molecules are included. The BA molecules protrude with their COOH groups at the beta-CD O-6-sides and are maintained in positions by hydrogen bonding to the surrounding O-6-H groups and water molecules. Water molecules (20.65) are distributed over 30 positions in the interstices between beta-CD molecules, except the water sites W-1, W-2 that are located in the channel of the beta-CD dimer. Water site W-2 is hydrogen bonded to the disordered ethanol molecule (occupancy 0.7).     

Structure and conformation of peptides involving prolyl residue. IV. L-Prolyl-L-leucine monohydrate

The dipeptide, L-prolyl-L-leucine monohydrate (C11H20N2O3.H2O, molecular weight, 246.3) crystallizes in the monoclinic space group P2(1), with cell constants: a = 6.492(2)A, b = 5.417(8)A, c = 20.491(5)A, beta = 96.59(2) degrees, Z = 2, Do = 1.15 g/cm3, and Dc = 1.142 g/cm3. The structure was solved by SHELX-86 and refined by full matrix least squares methods to a final R-factor of 0.081 for 660 unique reflections (I greater than 2 sigma (I)) measured on an Enraf Nonius CAD-4 diffractometer (CuK alpha, lambda = 1.5418 A, T = 293 K). The peptide linkage exists in the trans conformation. The pyrrolidine ring exists in the envelope conformation. The values of the sidechain torsion angles are: chi 1 = -59.3(13) degrees, chi 21 = -63.1(16) degrees and chi 22 = 174.8(15) degrees for leucine (C-terminal). The crystal structure is stabilised by a three-dimensional network of N-H ... O, O-H ... O, and C-H ... O hydrogen bonds.     

Crystal structure of the dimeric beta-cyclodextrin complex with 1,12-dodecanediol

The structure of the complex of beta-cyclodextrin (beta-CD) with 1,12-dodecanediol has been determined at 173 K and refined to a final R=0.0615 based on 22,386 independent reflections. The complex crystallizes in the triclinic space group P1; with a=17.926(4), b=15.399(3), c=15.416(3) A, alpha=103.425(4), beta=113.404(4), gamma=98.858(4) degrees, D(c)=1.362 Mg cm(-3) and V=3651.4(13) A(3) for Z=1. One molecule of the diol is located as a guest in the hydrophobic cavity of a beta-CD-dimer, forming a [3]pseudorotaxane. The guest molecule shows a disorder over two positions. The hydroxyl groups of the diol emerge from the primary faces of the beta-CD dimer and form several hydrogen bonds with water molecules lying in the interstitial space, similarly to dimeric complexes of beta-CD with other alpha,omega-bifunctional guests.     

Conformation and hydrogen bonding of N-formylmethionyl peptides. II. Crystal and molecular structure of N-formyl-L-methionyl-L-phenylalanine

Crystals of N-formyl-L-methionyl-L-phenylalanine (C15H20N2O4S), grown from aqueous methanol solution are orthorhombic, space group, P2(1)2(1)2(1), with cell parameters at 294K of a = 4.900(2), b = 17.947(4), c = 18.726(4)A, V = 1646.8A3, M.W. = 324.4, Z = 4 and Dm = 1.308 g/cc, and as expected, all nearly identical to that of N-f-D-Met-D-Phe studied by Jeffs, Heald, Chodosh & Eggleston (Int. J. Peptide Protein Res. 24, 442-446, 1984). The crystal structure was solved and refined using CAD-4 data (1095 reflections greater than or equal to 3 sigma) to a final R value of 0.042. Molecules related by the alpha-translation form a parallel beta-sheet rather than anti-parallel sheet as stated in the earlier study of Jeffs et al. The formation of the parallel rather than the anti-parallel beta-sheet structure, the use of the C-H ...O hydrogen bonds to stabilize the beta-sheet and the very short O-H ...O hydrogen bond between the carboxyl OH and the N-acyl oxygen atom emerge as the main structural features of the chemotactic N-formyl methionyl peptides.     

Conformation and hydrogen bonding of N-formylpeptides: crystal and molecular structure of N-formyl-L-alanyl-L-aspartic acid.

Crystals of N-formyl-L-alanyl-L-aspartic acid (C8H11N2O6) grown from aqueous methanol solution are orthorhombic, space group, P2(1)2(1)2(1) with cell parameters at 294K of a = 13.619(2), b = 8.567(2), c = 9.583(3)A, V = 1118.1A3, M.W. = 232.2, Z = 4, Dm = 1.38 g/cm3 and Dx = 1.378 g/cm3. The crystal structure was solved by the application of direct methods and refined to an R value of 0.075 for 1244 reflections with I greater than or equal to 3 sigma collected on a CAD-4 diffractometer. The structure contains two short intermolecular hydrogen bonds: (i) between the C-terminal carboxyl OH and the N-acyl oxygen (2.624(3)A), a characteristic feature found in many N-acyl peptides and (ii) between the aspartic carboxyl OH. and the peptide oxygen OP1 (2.623(3)A). The peptide is nonplanar (omega = 165.5(6) degrees). The molecule takes up a folded conformation in contrast to N-formyl peptides which form extended beta-sheets; the values of phi 1, psi 1, phi 2, psi 2(1), and psi 2(2) are, respectively -65.7(6), 152.0(5), -107.2(5), 30.9(5), and -150.3(6). The aspartic acid side chain conformation is g- with chi 1 = 73.1(5). The formyl group, as expected, is transplanar [OF-CF-N1-CA1 = -4.0(8) degrees]. The presence of the short O-H ... O hydrogen bond emerges as a structural feature common to this peptide and several other N-formyl peptides. There are no C-H ... O hydrogen bonds in this structure.     

Structure of the complex of beta-cyclodextrin with beta-naphthyloxyacetic acid in the solid state and in aqueous solution

The structure of the complex of beta-cyclodextrin (cyclomaltoheptaose) with beta-naphthyloxyacetic acid was studied in solid state by X-ray diffraction and in aqueous solution by 1H NMR spectroscopy. The complex crystallizes in the channel mode, space group C2, with a stoichiometry of 2:1; two beta-cyclodextrin molecules related by a twofold crystal axis form dimers, in the cavity of which one guest molecule is found on average. The above stoichiometry indicates one guest per beta-CD dimer statistically oriented over two positions or two guest molecules in pi-pi interactions in half of the beta-CD dimers and the rest of the beta-CD dimers empty. In addition, occupancy of 0.5 for the guest per every beta-CD dimer is in accord with the occupancy of the two disordered primary hydroxyls. These two hydroxyl groups, to which the carboxylic oxygen atoms of the guest are hydrogen bonded, point towards the interior of the beta-CD cavity. In aqueous solution, the 1H NMR spectroscopic study indicated that there is a mixture of complexes with host-guest stoichiometries both 1:1 and 2:1.     

Topography of the 1:1 alpha-cyclodextrin-nitromethane inclusion complex

Dissolution of alpha-cyclodextrin (alpha-CD) in 9:1 water-nitromethane smoothly generates the title compound, which crystallizes as the pentahydrate in the orthorhombic space group P2(1)2(1)2(1) with a = 9.452(4), b = 14.299(3), c = 37.380(10) A, and Z = 4. Its crystal structure analysis revealed the alpha-CD macrocycle in an unstrained conformation stabilized through a ring of O-2...O-3' hydrogen bonds between five of the six adjacent glucose residues. The nitromethane is located in the alpha-CD cavity in an orientation parallel to the plane of the macrocycle, and assumes two sites of equal population with the nitro group in excessive thermal motion; the guest is held by van der Waals contacts and C-H...O-type hydrogen bonds to the pyranose H-3 and H-5 protons. The packing of the macrocycles in the crystal lattice is of cage herringbone-type with an extensive intra- and intermolecular hydrogen bonding network. The ready formation of a nitromethane inclusion complex in aqueous nitromethane, and the subtleties of its molecular structure amply demonstrate the ease with which water is expelled from the alpha-CD cavity by a more hydrophobic co-solvent.     

Polymorphism in beta-cyclodextrin-benzoic acid inclusion complex: a kinetically controlled crystal growth according to the Ostwald's rule

Crystal form II of the beta-cyclodextrin-benzoic acid (beta-CD-BA) inclusion complex was obtained from the 1.5-year stored aqueous EtOH solution of beta-CD and BA as 2beta-CD.1.5BA.0.7EtOH.21H(2)O in the monoclinic space group C2 with unit cell constants: a=19.413(3), b=24.306(4), c=32.975(1)A, beta=104.41(1) degrees . By contrast, the desired crystal form I in the triclinic space group P1 that ever grew up from the fresh solution as 2beta-CD.2BA.0.7EtOH.20.65H(2)O was not reproducible any more [Aree, T.; Chaichit, N. Carbohydr. Res.2003, 338, 439-446]. In the two crystal forms, beta-CDs are isostructural with a 'round' conformation stabilized by intramolecular O-3(n)cdots, three dots, centeredO-2(n+1) hydrogen bonds. The BA inclusion geometries are similar with a preferred orientation, that is, BAs are situated above the O-4 plane, point their COOH groups to the beta-CD O-6 side, incline 52 degrees with respect to the O-4 plane and are mainly maintained in positions by hydrogen bonding with the surrounding water molecules. beta-CDs form dimers as structural motif of different packing modes: the screw-channel type in form II and the average of intermediate and tetrad types in form I. Polymorphism in the beta-CD-BA inclusion complex is a kinetically controlled crystal growth following the Ostwald's rule: the less stable crystal form I grew up first within one week from the fresh solution, whereas the more stable crystal form II appeared after 1.5-year storage.     

The crystal structure of 1,2,3,4,6-penta-O-benzoyl-alpha-D-mannopyranose: observation of C-H...pi interaction as a surrogate to O-H...O interaction of a free sugar

The crystal structure of the title compound was determined by X-ray crystallography. The compound crystallized in the orthorhombic space group P2(1)2(1)2(1) with four molecules in the unit cell with a=9.170(2), b=9.873 (2), c=38.831(8) A. The structure was refined to a R index of 0.041 for 7907 independent reflections. The mannopyranose unit adopts a distorted 4C1 conformation. The structure depicts unique network of C-H...pi interactions, very closely resembling the pattern of O-H...O interactions in free sugars. This intriguing and rare observation points to a notion that the supramolecular organization pertaining to a sugar is in-built in the pyranose ring itself.     

Conformation and hydrogen bonding of N-formylmethionyl peptides. Parallel beta-sheet in the crystal structure of N-formyl-L-methionyl-L-valine

Crystals of N-formyl-L-methionyl-L-valine (C11H20N2O)4S, M.W. = 276.3) are orthorhombic, space group )2(1)2(1)2(1) with cell constants at 294K of a = 4.851 (1), b = 14.925 (1), c = 19.745 (3) A, V = 1429.8 (1) A3, Z = 4 and observed (Dm) and calculated (Dx) of 1.49 and 1.488 g x cm-3, respectively. The crystal structure was solved using automatic diffractometer data (1260 reflections larger than or equal to 3 sigma) and refined to a final R-value of 0.035. This structure contains a short (2.626 (3) A) intermolecular hydrogen bond between the carboxyl OH and the N-acyl oxygen, a feature common to most N-acylamino acids and N-acylpeptides. The peptide is nearly planar (omega = 174.6 (5)); the values of psi 1, phi 2, psi 1T and psi 2T are, respectively, 131.8 (4) degrees, -139.9 (5) degrees, -39.3 (4) degrees and 142.1 (4) degrees. The methionine side chain is not zig-zag transplanar; the side chain torsion angles are: chi 1(1) = -60.0 (4) degrees, chi 2(1) = 176.0 (4) degrees and chi 3(1) = 71.8 (4) degrees. The two C gamma's for valine have psi 1-values of -64.4 (5) degrees and 173.7 (5) degrees. The formation of the parallel rather than antiparallel beta-sheet structure, the participation of the N-formyl group in the parallel beta-sheet and the use of C-H ... O hydrogen bonds to stabilize the beta-sheet are novel features found in this structure.     

The structure of [D-Hyi2,L-Hyi4]meso-valinomycin revealed by X-ray analysis

Direct x-ray analysis has been used to determine the crystal structure of [D-Hyi2, L-Hyi4]meso-valinomycin (cyclo[-D-Val-D-Hyi-L-Val-L-Hyi-(D-Val-L-Hyi-L-Val-D-+ ++Hyi)2-], C60H102N6O18), which crystallized from acetone with two solvent molecules. The crystals are trigonal, space group P32, number of molecules per unit cell Z = 3, cell parameters a = b = 15.2085 (8) A, c = 29.3250 (9) A, gamma = 120 degrees. The standard (R) and weighted (Rw) reliability factors after refinement of the atomic coordinates for C, N, and O atoms in the anisotropic thermal motion approximation, allowing for isotropic H atom contributions, were 0.070 and 0.082, respectively. The molecule adopts a distorted bracelet structure which is stabilized by six N-H ... O = C 4----1 type intramolecular hydrogen bonds. The side chains predominantly occupy external pseudoaxial positions relative to the cylindrical axis of the molecule. In contrast to meso-valinomycin, only four of the six Val carbonyl oxygen atoms are directed inwards to form a coordination centre for the molecule, and the carbonyl oxygen atoms of residues D-Val1 and L-Val3 are twisted outward and point away from the centre of the molecule. Although the analogue has a partially formed ion-binding center, it is inaccessible because the hydrophobic isopropyl groups of the D-Hyi2 and L-Hyi4 residues screen the molecular cavity on both sides.     

Complexation of trivalent lanthanide cations by galactitol in the solid state. The crystal structure and an FT-IR study of 2NdCl3.galactitol.14H2O

The crystal structure of 2NdCl3.galactitol.14H2O has been determined. The crystal system is triclinic, space group: -1, with unit-cell dimensions: a = 9.736(2), b = 10.396, c = 8.027 A; alpha = 108.05(3), beta = 92.68(3), gamma = 88.44(3) degrees, V= 771.6(3) A3, Z = 2. Each Nd atom is coordinated to nine oxygen atoms, three from the alditol and six from water molecules, with Nd-O distances from 2.461 to 2.552 A. The seventh water molecule is hydrogen-bonded by the hydroxyl hydrogen on O-1 (O-1-H-ll...O-10, 2.639 A). The FT-IR spectra of 2NdCl3.galactitol.14H2O and 2PrCl3.galactitol.14H2O are analogous, and show that Pr and Nd have the same coordination mode. The IR results are consistent with the crystal structures.     

Crystal structure of N-(benzyloxycarbonyl)aminoethyl-2,3,4,6-tetra-O-benzoyl-alpha-D-mannopyranoside: stabilization of the crystal lattice by a tandem network of N-H. . .O, C-H. . .O, and C-H. . .pi interactions

Single crystal X-ray analysis of an aminoethyl mannopyranoside, namely, N-(benzyloxycarbonyl)aminoethyl-2,3,4,6-tetra-O-benzoyl-alpha-D-mannopyranoside (1), shows that the compound crystallizes in the monoclinic space group P2(1), with two molecules in the unit cell. The mannopyranoside unit adopts a distorted 4C(1) conformation. An analysis of the intermolecular interactions reveals a tandem network of N-H. . .O, C-H. . .O, and C-H. . .pi interactions responsible for stabilizing the crystal lattice.     

Investigation of C-H...O=C and N-H...OC hydrogen-bonding interactions in crystalline thymine by DFT calculations of O-17, N-14 and H-2 NQR parameters

A computational study at the level of density functional theory (DFT) was carried out to investigate C-H...O=C and N-H...O=C hydrogen-bonding interactions (HBs) in the real crystalline cluster of thymine by O-17, N-14 and H-2 calculated nuclear quadrupole resonance (NQR) parameters. To perform the calculations, a hydrogen-bonded pentameric cluster of thymine was created using X-ray coordinates where the hydrogen atoms positions are optimized and the electric field gradient (EFG) tensors were calculated for the target molecule. Additional EFG calculations were also performed for crystalline monomer and an optimized isolated gas-phase thymine. The calculated EFG tensors at the level of B3LYP and B3PW91 DFT methods and 6-311++G**and CC-pVTZ basis sets were converted to those experimentally measurable NQR parameters, quadrupole coupling constants and asymmetry parameters. The results reveal that because of strong contribution to N-H...O=C HBs, NQR parameters of O2, N1 and N3 undergo significant changes from monomer to the target molecule in cluster. Furthermore, the NQR parameters of O2 also undergo some changes because of non-classical C-H...O=C HBs.     

Quantum-chemical analysis of C-H...O and C-H...N interactions in RNA base pairs--H-bond versus anti-H-bond pattern

Geometries and interaction energies of unusual UU and AA base pairs with one standard hydrogen bond (H-bond) and additional C-H...O or C-H...N contacts have been determined by quantum-chemical methods taking into account electron correlation. Whereas the C-H bond length in the UU C-H...O contact increases upon complex formation (H-bond pattern), the C-H bond of the AA C-H....N interaction is shortened (anti-H-bond pattern). The same properties are found for model complexes between U or A and formaldehyde that have intermolecular C-H...acceptor contacts but no standard H-bonds. Both the C-H...acceptor H-bond and anti-H-bond interactions are attractive. A possible influence of the donor CH group charge distribution on the interaction pattern is discussed.     

Crystal structure of hexakis(2,6-di-O-methyl)-alpha-cyclodextrin-acetonitrile dihydrate: a channel formed by methyl groups harbors a chain of five partially occupied water sites

Hexakis(2,6-di-O-methyl)-alpha-cyclodextrin (DIMEA) crystallizes from 1:1 water-acetonitrile as DIMEA-acetonetril-dihydrate in the orthorhombic space group P2(1)2(1)2(1), unit cell dimensions a = 14.2775(5), b = 15.7312(5), c = 31.1494(11) A. Refinement of the structure against 5540 X-ray diffraction data converged at an R factor of 0.083. The macrocycle exhibits a 'round' conformation and is stabilized by intramolecular, interglucose O-3-H(n)...O-2(n + 1) and C-6-H(n)...O-5(n + 1) hydrogen bonds. Acetonitrile is included in the central cavity of DIMEA and held in position by C-5-H...N interactions. The two water molecules in the asymmetric units are distributed over six sites. One is fully occupied due to hydrogen bonding to O-3 groups of two symmetry-related DIMEA molecules, whereas the five remaining sites show occupancies between 0.15 and 0.25. These sites are in hydrogen bonding contact with O...O distances between 2.59 and 3.50 A and are located in infinite, hydrophobic channels parallel to the alpha-axis, which are coated with methyl groups of symmetry-related DIMEA.