Interactions In Crystal Engineering Research Articles

Sigma-Hole and Lone-Pair-Hole Site-Based Interactions of Seesaw Tetravalent Chalcogen-Bearing Molecules with Lewis Bases.

For the first time, sigma (σ)- and lone-pair (lp)-hole site-based interactions of SF4 and SeF4 molecules in seesaw geometry with NH3 and FH Lewis bases were herein comparatively investigated. The obtained findings from the electrostatic potential analysis outlined the emergence of sundry holes on the molecular entity of the SF4 and SeF4 molecules, dubbed the σ- and lp-holes. The energetic viewpoint announced splendid negative binding energy values for σ-hole site-based interactions succeeded by lp-hole analogues, which were found to be -9.21 and -0.50 kcal/mol, respectively, for SeF4···NH3 complex as a case study. Conspicuously, a proper concurrence between the strength of chalcogen σ-hole site-based interactions and the chalcogen's atomic size was obtained, whereas a reverse pattern was proclaimed for the lp-hole counterparts. Further, a higher preference for the YF4···NH3 complexes with elevated negative binding energy was promulgated over the YF4···FH ones, indicating the eminent role of Lewis basicity. The indications of the quantum theory of atoms in molecules generally asserted the closed-shell nature of all the considered interactions. The observation of symmetry-adapted perturbation theory revealed the substantial contributing role of the electrostatic forces beyond the occurrence of σ-hole site-based interactions. In comparison, the dispersion forces were specified to govern the lp-hole counterparts. Such emerging findings would be a gate for the fruitful forthcoming applications of chalcogen bonding interactions in crystal engineering and biological systems.

Unraveling the impact of hydrogen bonding and C‒H…π(CN) interactions in crystal engineering of cyclic aminobenzonitriles: A combined X-ray crystallographic and computational investigation

The essential role of organic crystals in drug development represents a significant research area and remains enduringly topical within the pharmaceutical industry. In the present study, four cyclic aminobenzonitriles 3a-d were prepared through the nucleophilic aromatic substitution reaction of 4-fluorobenzonitrile with various cyclic amines. The synthesized compounds were obtained in moderate to good yields and structurally characterized by FTIR, NMR spectroscopy, mass spectrometry and X-ray crystallography. The crystal packing of these compounds predominantly involves the use of hydrogen bonding interactions (C-H…N, C-H…S, C-H…O) and aromatic contacts (C-H…π(ring & CN), π…π) to govern the complex structural topology. These noncovalent interactions were further evaluated by molecular electrostatic potential (MEP) surface analysis and DFT energy calculations confirming the importance of π-stacking and CH…π interactions, either involving the arene or the π-system of the cyano groups. These interactions have been further characterized using the QTAIM/NCIplot computational tool.

Metal Centers as Nucleophiles: Oxymoron of Halogen Bond-Involving Crystal Engineering.

This review highlights recent studies discovering unconventional halogen bonding (HaB) that involves positively charged metal centers. These centers provide their filled d‐orbitals for HaB, and thus behave as nucleophilic components toward the noncovalent interaction. This role of some electron‐rich transition metal centers can be considered an oxymoron in the sense that the metal is, in most cases, formally cationic; consequently, its electron donor function is unexpected. The importance of Ha⋅⋅⋅d‐[M] (Ha=halogen; M is Group 9 (Rh, Ir), 10 (Ni, Pd, Pt), or 11 (Cu, Au)) interactions in crystal engineering is emphasized by showing remarkable examples (reported and uncovered by our processing of the Cambridge Structural Database), where this Ha⋅⋅⋅d‐[M] directional interaction guides the formation of solid supramolecular assemblies of different dimensionalities.

Engineering Crystals Using sp3 -C Centred Tetrel Bonding Interactions.

1,1,2,2‐Tetracyanocyclopropane derivatives 1 and 2 were designed and synthesized to probe the utility of sp3‐C centred tetrel bonding interactions in crystal engineering. The crystal packing of 1 and 2 and their 1,4‐dioxane cocrystals is dominated by sp3‐C(CN)2⋅⋅⋅O interactions, has significant C⋅⋅⋅O van der Waals overlap (≤0.266 Å) and DFT calculations indicate interaction energies of up to −11.0 kcal mol−1. A cocrystal of 2 with 1,4‐thioxane reveals that the cyclopropane synthon prefers interacting with O over S. Computational analyses revealed that the electropositive C2(CN)4 pocket in 1 and 2 can be seen as a strongly directional ‘tetrel‐bond donor’, similar to halogen bond or hydrogen bond donors. This disclosure is expected to have implications for the utility of such ‘tetrel bond donors’ in molecular disciplines such as crystal engineering, supramolecular chemistry, molecular recognition and medicinal chemistry.

Advances in ligand-unsupported argentophilic interactions in crystal engineering: an emerging platform for supramolecular architectures

Ligand-unsupported argentophilic interactions are described, emphasizing reticular design and recent developments in advanced synthetic strategies, and highlighting diverse interactions that are useful for the construction of unmitigated networks.

Towards design strategies for anion–π interactions in crystal engineering

This highlight article summarizes some of the fundamental aspects of the anion–π interaction leading to several design strategies for generating it in solids. In the main body we highlight some relevant examples that illustrate the viability of these strategies and the importance of anion–π interactions in crystal engineering.

The Power of Nonconventional Phenyl C–H···N Hydrogen Bonds: Supportive Crystal-Packing Force and Dominant Supramolecular Engineering Force

The role of phenyl C–H···N interactions in crystal engineering is explored with a variety of fluorinated phenyl-containing compounds. In particular, we show that this interaction can guide the formation of one-dimensional phenyl C–H···N hydrogen-bonded ribbons with, for example, 4-(2,3,5,6-tetrafluorophenylethynyl)pyridine. The interaction is shown to also control the formation of self-complementary homodimers with 3-(2,3,4,5-tetrafluorophenylethynyl)pyridine. We also demonstrate that the phenyl C–H···N hydrogen bond interaction is capable of enticing co-crystallization of molecules such as 2,3,5,6,2′,3′,5′,6′-octafluorobiphenyl and 4,4′-dipyridyl. Finally, we describe the use of an intramolecular scaffold to evaluate the effect of electron-withdrawing substituents on the strength of a phenyl C–H···N hydrogen bond.

Competing hydrogen bonding and halogen bonding interactions in crystal engineering: A case study of bi-functional donor molecules

Based on the recent determined co-crystals of a set of bi-functional donor molecules with two isomeric symmetric acceptors, the competition between hydrogen bonding and halogen bonding interactions in crystal engineering was investigated in this work using the M06-2x and ωB97XD methods. The preference of the occurrence of secondary weak interactions was observed in hydrogen-bonded complexes. Hydrogen bonding interactions are predicted to be much stronger than corresponding halogen bonding interactions. No obvious difference was found between the systems of the two acceptors under study. The model complexes, in which hydrogen bonds and halogen bonds coexist, show additivity. Finally, a comparison between theoretical results and experimental observations was presented, and the implications of the calculations on the supermolecular assemblies based on the two interactions were also discussed.

Comparison of the polymorphs and solvates of two analogous fungicides—a case study of the applicability of a supramolecular synthon approach in crystal engineering

The polymorphism and solvate formation of thiophanate-ethyl (TE), a fungicidal active, were investigated by solvent crystallization and compared to a close analogue, thiophanate-methyl (TM). Four polymorphs and seven solvates of TE were found and structurally compared with the previously found two polymorphs and fourteen solvates of TM by analyzing the hydrogen bonding patterns and using fingerprint plots, packing coefficients and lattice energies. TE and TM have the same functional groups that can build identical supramolecular synthons. Despite the strong similarities, the polymorphs and solvates of the two actives show significant differences in hydrogen bonding and packing. The results demonstrate the challenges in using a supramolecular synthon approach, and promote the importance in finding methods to also make use of packing effects and lipophilic interactions in crystal engineering.

Tripod molecules build molecular networks and open-dimer capsules by weak interactions

Three tripod molecules, tris(2-methoxy-5-nitrobenzyl)phosphine oxide (1), tris(2-butoxy-3-methyl-5-nitrobenzyl)phosphine oxide (2), and tris(3-nitrobenzyl)amine (TNBA), were synthesized and crystallized. The structures of 1, 2, and their comparison (TNBA) were determined by X-ray crystallography. It is noteworthy that compound 1 interacted with adjacent molecules via π-π stacking and C-H⋯π interactions to yield an open supramolecular network with the porosity P in 8.9%, whereas compound 2 gathered closely to form an open-dimer capsule by sixfold N-O⋯π and triple C-H⋯O interactions, which showed a rare example of a stable in, out-invertomer of phosphine inversion existing in open-dimers. A series of columns were built and arranged side by side by these weak interactions. By contrast, TNBA crystallized to form a 2D network maintained by C-H⋯O and C-H⋯π interactions. It seems minor changes of the chemical structure may cause large differences in the crystal structure and interactions in crystal engineering.

Reliability of π–π Stacking Interactions in Crystal Engineering: Synthesis and Structure of a Hemidirected Lead Complex

A new three-dimensional polymeric supramolecular PbII complex, {[Pb3(bpy)3(ip)3](H2O)}n, (bpy = 2,2′-bipyridine and ip = isophthalate), has been synthesised and characterised. Single-crystal analysis shows that {[Pb3(bpy)3(ip)3](H2O)}n contains a one-dimensional chain polymeric framework and all the Pb centres with a coordination number of six possess an electron lone pair. The coordination sphere is hemidirected which gives a highly distorted geometry. The arrangement of O- and N- atoms towards Pb atoms suggests a gap or hole in the coordination geometry around these atoms. Moreover, there are three types of π–π interactions between aromatic rings and the one-dimensional chains, which are connected by these interactions to form a three dimensional supramolecular network with the channels occupied by water molecules.

Arene–perfluoroarene interactions in crystal engineering. XV. Ferrocene–decafluorobiphenyl (1/1)

The title crystal, [Fe(C5H5)2].C12F10, comprises infinite chains of alternating component molecules, linked through face-to-face contacts of nearly parallel cyclopentadienyl and pentafluorophenyl rings. The decafluorobiphenyl molecule has a crystallographic twofold axis and the Fe atom of the ferrocene molecule is on a crystallographic inversion centre, with both cyclopentadienyl rings disordered.

Arene–perfluoroarene interactions in crystal engineering. Part 14. 1:1 Complexes of octafluoronaphthalene with fluorene and 9,10-dihydrophenanthrene

The 1:1 molecular complexes of octafluoronaphthalene (OFN) with fluorene (1) and with 9,10-dihydrophenanthrene (2) were prepared by cocrystallization of the components and characterized by single-crystal X-ray diffraction. The structure of 1 can be described as a mixed-stack or a laminar checkerboard motif of alternating OFN and fluorene molecules, whilst slanted mixed-stack, herringbone, and face-to-face heteromolecular dimer motifs can all be recognised in 2.Key words: single crystal, X-ray structure, π stacking, fluoroarene.

Inclusion Compounds of Hexakis(4-cyanophenyl)benzene: Open Networks Maintained by C−H···N Interactions

Hexakis(4-cyanophenyl)benzene (1) was crystallized from various solvents, and the structures were determined by X-ray crystallography. In all cases studied, inclusion compounds were obtained, and crystallization yielded networks held together primarily by C−H···N interactions. However, the resulting structures were diverse and depended strongly on the solvent used for crystallization. In certain cases, remarkably large fractions of the volumes of the crystals (up to 58%) are accessible to guests. The diversity of the structures obtained underscores the limitations of using C−H···N interactions in crystal engineering.

Arene–perfluoroarene interactions in crystal engineering. Part 10. Crystal structures of 1∶1 complexes of octafluoronaphthalene with biphenyl and biphenylene

Co-crystals of the 1 ∶ 1 molecular complexes of octafluoronaphthalene (OFN) with biphenyl and biphenylene have been grown from solutions containing both components. Their structures have been analysed by single-crystal X-ray diffraction techniques at low temperature, which show them to be composed of infinite columns of near parallel, alternating OFN and biphenyl or biphenylene molecules, indicating that the complexes are stabilised by the arene–perflouroarene interaction.

Arene-perfluoroarene interactions in crystal engineering: structural preferences in polyfluorinated tolans

The compounds 4-ROC6F4CCPh (4) where R = Me (a), Et (b), Prn (c), Pri (d), Bun (e), n-C5H11 (f), PhCH2 (g), PhCH2CH2 (h), 4-MeC6H4 (i), 4-EtC6H4 (j) and menthyl (k), have been prepared by reaction of C6F5CCPh (3) with ROH in the presence of KOH, and characterised by NMR (1H, 13C, 19F) and mass spectroscopy. The single-crystal structures of PhCCPh·C6F5CCC6F5 (1∶2), 3 and 4a,c,d,f,g,i have been determined by X-ray diffraction at 120–160 K, and that of 3 also calculated by an ab initio pseudo-potential DFT method. The tolan moiety is nearly planar in each molecule except 4a, which has a Ph/C6F5 dihedral angle of 25.8°. The R group adopts an out-of-plane orientation except in 4f, where the n-pentyl chain is nearly coplanar with the C6F5 group at the cost of severe distortion of the C(ar)–C(ar)–O angles (which differ by 13.5°). The structures of 1∶2, 3 (pseudo-isomorphous with 1∶2), 4a, 4g (disordered) and 4i contain stacks of alternating arene and perfluoroarene moieties; 4c and 4d form discrete centrosymmetric dimers with arene/perfluoroarene overlap, while 4f forms infinite stacks without such overlap. Differential thermal analysis and transmitted polarised light microscopy revealed no liquid-crystalline behaviour of 3 and 4.

On the Reliability of C−H···O Interactions in Crystal Engineering: Synthesis and Structure of Two Hydrogen Bonded Phosphonium Bis(aryloxide) Salts

Two related phosphonium aryloxides, [Ph3PCH3]+2[CH2(C6H2-3,5-tert-butyl-4-O)2]2-, 1a, and [Ph3PC2H5]+2[CH2(C6H2-3,5-tert-butyl-4-O)2]2-, 1b have been synthesized by protonation of nonstabilized phosphorus ylides with 4,4‘-methylenebis(2,6-di-tert-butylphenol) LH2. The crystal structures of 1a and 1b have been determined by single-crystal X-ray diffraction, and that of 1b has also been determined by low-temperature (20 K) neutron diffraction. Both crystallize as CH3CN solvates, and both exhibit polymeric supramolecular structures via extensive C−H···O hydrogen bonding. The predominant structural motif is chelation of the aryloxide oxygen atom of the anion by phosphonium alkyl and aryl C−H groups, such as has been previously observed for phosphonium monoaryloxide salts. The use of this motif as a supramolecular synthon in crystal engineering is explored. In the case of 1a, in addition to the expected intermolecular C−H···O hydrogen bonding pattern, C−H···π interactions between the anion and this solvent are observed. In the structure of 1b, C−H···π interactions between the cation and anion lead to an unpredicted supramolecular structure. The possible significance of this feature is discussed the context of the general use of weak hydrogen bonds in crystal engineering.

Arene-perfluoroarene interactions in crystal engineering 7 : single-crystal structures of 1:1 complexes of octafluoronaphthalene and hexafluorobenzene with acenaphthene

Co-crystals of the 1:1 molecular complexes formed between both octafluoronaphthalene and hexafluorobenzene with acenaphthene have been prepared and analysed by X-ray diffraction, which showed them to be composed of infinite stacks of alternating molecules, as is the case for other arene-perfluoroarene complexes.

Arene–perfluoroarene interactions in crystal engineering 8: structures of 1∶1 complexes of hexafluorobenzene with fused-ring polyaromatic hydrocarbons

A series of 1∶1 complexes of hexafluorobenzene (HFB) with naphthalene, anthracene, phenanthrene, pyrene and triphenylene were prepared and their X-ray crystal structures determined at low temperatures. Each structure contains infinite mixed stacks of alternating nearly-parallel molecules of HFB and arene, which display various ‘slip’ distortions and form different 3-dimensional motifs. The naphthalene, anthracene and pyrene complexes show polymorphism. Crystal packing of HFB complexes is compared with that of corresponding octafluoronaphthalene complexes. Ab initio DFT calculations on the infinite lattices give lattice parameters and ‘slip’ parameters in close agreement with the experimental crystal structures, while showing that intermolecular cohesion is predominantly of electrostatic, rather than van der Waals, origin.

Arene-perfluoroarene interactions in crystal engineering. 5. Octafluoronaphthalene-tetrathiafulvalene (1/1).

In the title complex, C(10)F(8) x C(6)H(4)S(4), planar centrosymmetric molecules of tetrathiafulvalene and octafluoronaphthalene, inclined to each other by 9.6 (1) degrees, form a mixed stack which does not exhibit charge transfer. Adjacent stacks pack in a herring-bone motif.