In this Viewpoint, the impact of the paper published by Gautam R. Desiraju and Angelo Gavezzotti (J. Chem. Soc., Chem. Commun., 1989, 621) upon the development of Crystal Engineering, now recognised a key discipline in contemporary chemical/pharmaceutical/materials science, is discussed.
Despite being disparaged for their malodorous and toxic demeanour, compounds of selenium, a bio-essential element, and tellurium, offer possibilities as therapeutic agents. Herein, their potential use as drugs, for example, as anti-viral, anti-microbial, anti-inflammatory agents, etc., will be surveyed along with a summary of the established biological functions of selenium. The natural biological functions of tellurium remain to be discovered.
The title supra-molecular polymer, [Cu(S(3)O(6))(H(2)O)(4)](n), features a tetra-gonally distorted octa-hedral Cu(II) centre within an O(6) donor set with the longer Cu-O bonds linking the dication and the trithio-nate dianion. Extensive O-H⋯O hydrogen-bonding inter-actions connect the supra-molecular chains into a three-dimensional network.
In the title compound, C14H8N4O6, the benzoxazin-4-one fused-ring system (r.m.s. deviation = 0.018 Å) is coplanar with the attached benzene ring [dihedral angle = 0.81 (4)°], there being an intra-molecular N-H⋯N hydrogen bond between them. Each nitro group is twisted out of the plane of the attached benzene ring [O-N-C-C torsion angles = 167.94 (11) and 170.38 (11)°]. In the crystal, amine-nitro N-H⋯O hydrogen bonds lead to centrosymmetric dimeric aggregates that are connected into a three-dimensional architecture by oxazin-yl-nitro C-H⋯O and π-π inter-actions [inter-centroid distance between the oxazinyl and terminal benzene rings = 3.5069 (7) Å].
The asymmetric unit of title co-crystal, C10H8N2·2C7H7NO2, comprises a centrosymmetric 4,4'-bi-pyridine mol-ecule, and a 2-amino-benzoic acid mol-ecule in a general position. The latter is effectively planar [C-C-C-O torsion angle = 5.0 (3)°] owing to an intra-molecular N-H⋯O(carbon-yl) hydrogen bond. Three-mol-ecule aggregates are formed via O-H⋯N(pyrid-yl) hydrogen bonds and these are connected into supra-molecular layers in the bc plane by N-H⋯O(carbon-yl) hydrogen bonds and π-π inter-actions between pyridyl and benzene rings [inter-centroid distance = 3.634 (2) Å]. Layers are connected along the a axis by weak π-π inter-actions between benzene rings [3.964 (2) Å].
The asymmetric unit of the title co-crystal, C10H6O8·2C8H10N4O2, comprises a centrosymmetric benzene-1,2,4,5-tetra-carb-oxy-lic acid (LH4) mol-ecule and a mol-ecule of caffeine in a general position. LH4 is nonplanar, with the dihedral angles between the ring and pendent carb-oxy-lic acid groups being 44.22 (7) and 49.74 (7)°. By contrast, the caffeine mol-ecule is planar (r.m.s. deviation = 0.040 Å). Supra-molecular layers parallel to (-1-10) are sustained by carb-oxy-lic acid O-H⋯O(carbon-yl) and O-H⋯N(imidazole) hydrogen bonds, as well as by meth-yl-carbonyl C-H⋯O inter-actions. These stack via π-π inter-actions between the benzene and imidazole rings [inter-centroid distance = 3.4503 (10) Å].
The asymmetric unit of the title co-crystal, C12H12N2·2C7H7NO2, comprises a centrosymmetric 4-[2-(pyridin-4-yl)eth-yl]pyridine mol-ecule and a 2-amino-benzoic acid mol-ecule in a general position. The acid has a small twist between the carb-oxy-lic acid residue and the ring [dihedral angle = 7.13 (6)°] despite the presence of an intra-molecular N-H⋯O(carbon-yl) hydrogen bond. Three-mol-ecule aggregates are formed via O-H⋯N(pyrid-yl) hydrogen bonds, and these are connected into supra-molecular layers in the bc plane by N-H⋯O(carbon-yl) hydrogen bonds and π-π inter-actions between pyridine and benzene rings [inter-centroid distance = 3.6332 (9) Å]. Layers are connected along the a axis by weak π-π inter-actions between benzene rings [3.9577 (10) Å].
The title compound, C(13)H(10)Cl(2)N(2)S, represents a monoclinic polymorph of the previously reported ortho-rhom-bic form [Ramnathan et al. (1996 ▶). Acta Cryst. C52, 134-136]. The mol-ecule is twisted with the dihedral angle between the benzene rings being 55.37 (7)°. The N-H atoms are syn to each other, which contrasts their anti disposition in the ortho-rhom-bic form. In the crystal, mol-ecules assemble into zigzag chains along the c axis via N-H⋯S hydrogen bonds. Chains are connected into layers via C-H⋯Cl inter-actions, and these stack along the a axis.
The asymmetric unit of the title compound, {(C34H28FeP2)[Au(C5H8NS2)]2}, comprises half a mol-ecule, with the full mol-ecule being generated by the application of a centre of inversion. The independent Au(I) atom is coordinated by thiol-ate S and phosphane P atoms that define an approximate linear geometry [S-Au-P = 169.35 (3)°]. The deviation from the ideal linear is traced to the close approach of the (intra-molecular) non-coordinating thione S atom [Au⋯S = 3.1538 (8) Å]. Supra-molecular layers parallel to (100) feature in the crystal packing, being sustained by phen-yl-thione C-H⋯S inter-actions, with the non-coordinating thione S atom in the role of a dual acceptor. Layers stack with no specific inter-actions between them.
The title compound, C15H24O2 [systematic name: (4S,4aR,6R,8aR)-4a-hy-droxy-4,8a-dimethyl-6-(prop-1-en-2-yl)octahydro-naphthalen-1(2H)-one], features two edge-shared six-membered rings with the hydroxyl and methyl substituents at this bridge being trans. One adopts a flattened chair conformation with the C atoms bearing the carbonyl and methyl substituents lying 0.5227 (16) and 0.6621 (15) Å, respectively, above and below the mean plane through the remaining four C atoms (r.m.s. deviation = 0.0145 Å). The second ring, bearing the prop-1-en-2-yl group, has a chair conformation. Supra-molecular helical chains along the b axis are found in the crystal packing, which are sustained by hy-droxy-carbonyl O-H⋯O hydrogen bonding.
Four independent mol-ecules (A-D) comprise the asymmetric unit of the title compound, C15H26O2, which differ only in the relative orientations of the terminal -C(Me)2OH groups [e.g. the range of Cmethyl-ene-Cmethine-Cquaternary-Ohy-droxy torsion angles is 52.7 (7)-57.1 (6)°, where the Cmethyl-ene atom is bound to an epoxide C atom]. The five-membered rings adopt envelope conformations, with the methyl-ene C atom adjacent to the methine C atom being the flap atom in each case. In each mol-ecule, the conformation of the seven-membered ring is a half-chair, with the Cmethyl-ene-Cmethine bond, flanked by methyl-ene C atoms, being the back of the chair. Supra-molecular helical chains along the b axis are found in the crystal packing, sustained by hy-droxy-epoxide O-H⋯O hydrogen bonding. Mol-ecules of A self-associate into a chain as do those of D. A third independent chain comprising B and C mol-ecules is also formed. The studied crystal is a pseudo-merohedral twin (minor component ca 21%).
The sulfa-thia-zole mol-ecule in the title 1:1 co-crystal, C9H9N3O2S2·C18H12N6, adopts an approximate L-shape [dihedral angle between the five- and six-membered rings = 86.20 (9)°] and features an intra-molecular hypervalent S⋯O inter-action [2.8666 (15) Å]. Overall, the triazine mol-ecule has the shape of a disk as the pendant pyridine rings are relatively close to coplanar with the central ring [dihedral angles = 18.35 (9), 6.12 (9) and 4.67 (9)°]. In the crystal packing, a linear supra-molecular chain aligned along [01-1] is formed as a result of amino-pyridyl N-H⋯N hydrogen bonding with syn-disposed pyridyl mol-ecules of one triazine, and amine-pyridyl N-H⋯N hydrogen bonding with the third pydridyl ring of a second triazine mol-ecule. A three-dimensional architecture arises as the chains are connected by C-H⋯O inter-actions.
The asymmetric unit of the title co-crystal, 2C14H13N2 (+)·C10H4O8 (2-)·2C14H12N2·C10H6O8, comprises a 2,9-dimethyl-1,10-phenanthrolin-1-ium cation (Me2PhenH(+)) and a 2,9-dimethyl-1,10-phenanthroline mol-ecule (Me2Phen), each in a general position, and half each of a 2,5-di-carb-oxy-benzene-1,4-di-carboxyl-ate dianion (LH2 (2-)) and a benzene-1,2,4,5-tetra-carb-oxy-lic acid mol-ecule (LH4), each being disposed about a centre of inversion. Small twists are evident in the dianion [the C-C-C-O torsion angles are 168.41 (18) and 16.2 (3)°], whereas a major twist is found for one carb-oxy-lic acid group in the neutral mol-ecule [C-C-C-O = 66.3 (2) and 18.2 (3)°]. The most prominent feature of the crystal packing is the formation of linear supra-molecular chains along [001] mediated by charge-assisted O-H⋯O(-) hydrogen bonding between alternating LH4 and LH2 (2-). These are connected to the Me2PhenH(+) and Me2Phen species by N-H⋯O and O-H⋯N hydrogen bonds, respectively. A three-dimensional architecture is formed by C-H⋯O and π-π inter-actions [inter-centroid distance = 3.5337 (17) Å].
In the title ethanol solvate, C29H20Cl2N2O·C2H5OH, the quinolinyl residues form a dihedral angle of 46.41 (4)° with each other, and each is inclined [Cp-C-C=O and C=C-C-Cp (p = pyridyl) torsion angles = 54.8 (2) and 144.44 (19)°, respectively] with respect to the almost planar bridging prop-2-en-1-one residue [O=C-C=C torsion angle = -4.1 (3)°]. The ethanol solvent mol-ecule is disordered over two positions of equal occupancy and is located close to a centre of inversion. These mol-ecules reside in cavities defined by the organic mol-ecules, which are connected into a three-dimensional architecture by C-H⋯Cl, C-H⋯O and C-H⋯N inter-actions, as well as π-π contacts [inter-centroid distances = 3.5853 (10) and 3.8268 (11) Å], each involving pyridyl rings.
The asymmetric unit of the title co-crystal, C12H14N4O2S·0.5C6H12N2, comprises the sulfonamide mol-ecule and half a mol-ecule of 1,4-di-aza-bicyclo-[2.2.2]octane (DABCO), the latter being disposed about a crystallographic twofold rotation axis. In the sulfonamide mol-ecule, the aromatic rings are almost perpendicular to one another [dihedral angle = 75.01 (8)°]. In the crystal, mol-ecules are connected into a three-mol-ecule aggregate via amide-DABCO N-H⋯N hydrogen bonds, and these are connected into a three-dimensional architecture via amino-DABCO N-H⋯O and amino-pyrimidine N-H⋯N hydrogen bonds.
The asymmetric unit of the title salt, C12H14N2 (2+)·2C7H3N2O6 (-), comprises half a 4-[2-(pyridin-1-ium-4-yl)eth-yl]pyridin-1-ium dication, being disposed about a centre of inversion, and a 2,6-di-nitro-benzoate anion, in a general position. In the anion, the carboxyl-ate group is inclined to the benzene ring [dihedral angle = 85.45 (9)°], whereas near-coplanar and twisted arrangements are found for the nitro groups [O-N-C-C torsion angles = 179.80 (14) and 20.2 (2)°]. In the crystal, three-component aggregates sustained by charge-assisted N(+)-H⋯O(-) hydrogen bonds are found and these are consolidated into a three-dimensional architecture by C-H⋯O and π-π [inter-centroid distances = 3.6796 (14) and 3.7064 (14) Å] inter-actions.
The title compound, C26H42N4O2S2, adopts a shallow U-shape as both pendant arms of the 1,3-substituted benzene ring are orientated in the same direction. The thione S atoms lie to the same side of the benzene ring and the carbonyl O atoms to the other. The most prominent feature of the crystal packing is the formation of inversion dimers mediated by N-H⋯S hydrogen bonds. One of the 2-methyl-propyl groups is statistically disordered over two positions.
The asymmetric unit of title salt co-crystal, [K(C9H11N2S2)(C12H24O6)], comprises a K(+) cation, an (-)S2CN(Et)py anion and a 18-crown-6 mol-ecule. Substantial delocalization of π-electron density is evident in the di-thio-carbamate anion, as indicated by the equivalent C-S bond lengths. The K(+) cation sits within an O6S2 donor set lying 0.7506 (6) Å out of the least-squares plane through the six O atoms (r.m.s. deviation = 0.1766 Å) of the 18-crown-6 mol-ecule with the two S atoms being on one side of this plane. Supra-molecular layers in the bc plane, sustained by C-H⋯O and C-H⋯π inter-actions, feature in the crystal packing.
In the title compound, C32H21ClN2O, an almost planar (r.m.s. deviation = 0.033 Å) prop-2-en-1-one bridge links quinolinyl and benzoquinolinyl residues; the latter are twisted out of the plane of the bridge [dihedral angles = 75.94 (5) and 20.20 (5)°, respectively]. In the crystal, a three-dimensional architecture arises as a result of C-H⋯O, C-H⋯π and π-π [centroid-centroid distances involving pyridine rings = 3.5806 (7)-3.7537 (7) Å] interactions.
Crystal structures of transition and main group element 1,1-dithiolates are shown to be partially sustained by C-H···π(chelate) interactions. For the planar binary bisdithiocarbamates, C-H···π(MS(2)C) interactions lead to aggregation patterns ranging from a 0-D four molecule aggregate to a 3-D architecture but with the majority of structures featuring 1-D or 2-D supramolecular assemblies.