Theoretical investigation of tube-like supramolecular structures formed through bifurcated lithium bonds

The stability of three supramolecular naostructures, which are formed through the aggregation of identical belts of [12] arene containing p-nitrophenyllithium, 1,4-dilithiatedbenzene and 1,4-dinitrobenzene units, is investigated by density functional theory. The electrostatic potential calculations indicate the ability of these belts in forming bifurcated lithium bonds (BLBs) between the Li atoms of one belt and the oxygen atoms of the NO2 groups in the other belt, which is also confirmed by deformation density maps and quantum theory of atoms in molecules (QTAIM) analysis. Topological analysis and natural bond analysis (NBO) imply to ionic character for these BLBs with binding energies up to approximately - 60 kcal mol-1. The many-body interaction energy analysis shows the strong cooperativity belongs to the configuration with the highest symmetry (C4v) containing p-nitrophenyllithium fragments as the building unit. Therefore, it seems that this configuration could be a good candidate for designing a BLB-based supramolecular nanotube with infinite size in this study.

Crystal structure and Hirshfeld surface analysis of 4,5-di-bromo-2-(4-meth-oxy-phen-yl)-2,3,4,4a,5,6,7,7a-octa-hydro-1H-4,6-ep-oxy-1H-cyclo-penta-[c]pyridin-1-one

The mol-ecule of the title compound, C15H15Br2NO3, comprises a fused tricyclic system consisting of two five-membered rings (cyclo-pentane and tetra-hydro-furan) and one six-membered ring (tetra-hydro-pyridinone). Both five-membered rings of the tricyclic system have envelope conformations, and the conformation of the six-membered cycle is inter-mediate between chair and half-chair. In the crystal, the mol-ecules are linked by C-H⋯O hydrogen bonds and C-H⋯π, C-Br⋯π and C⋯O inter-actions into double layers. The layers are connected into a three-dimensional network by van der Waals inter-actions.

(3aS,4R,5R,6S,7aR)-4,5-Di-bromo-2-[4-(tri-fluoro-meth-yl)phen-yl]-2,3,3a,4,5,6,7,7a-octa-hydro-3a,6-ep-oxy-1H-isoindol-1-one: crystal structure and Hirshfeld surface analysis

The asymmetric unit of the title compound, C15H12Br2F3NO2, consists of two crystallographically independent mol-ecules. In both mol-ecules, the pyrrolidine and tetra-hydro-furan rings adopt an envelope conformation. In the crystal, mol-ecule pairs generate centrosymmetric rings with R 2 2(8) motifs linked by C-H⋯O hydrogen bonds. These pairs of mol-ecules form a tetra-meric supra-molecular motif, leading to mol-ecular layers parallel to the (100) plane by C-H⋯π and C-Br⋯π inter-actions. Inter-layer van der Waals and inter-halogen inter-actions stabilize mol-ecular packing. The F atoms of the CF3 groups of both mol-ecules are disordered over two sets of sites with refined site occupancies of 0.60 (3)/0.40 (3) and 0.640 (15)/0.360 (15). The most important contributions to the surface contacts of both mol-ecules are from H⋯H (23.8 and 22.4%), Br⋯H/H⋯Br (18.3 and 12.3%), O⋯H/H⋯O (14.3 and 9.7%) and F⋯H/H⋯F (10.4 and 19.1%) inter-actions, as concluded from a Hirshfeld surface analysis.

Crystal structure and Hirshfeld surface analysis of (RS)-3-hy-droxy-2-{[(3aRS,6RS,7aRS)-2-(4-methyl-phenyl-sulfon-yl)-2,3,3a,6,7,7a-hexa-hydro-3a,6-ep-oxy-1H-isoindol-6-yl]meth-yl}isoindolin-1-one

The title compound, C24H24N2O5S, crystallizes with two independent mol-ecules (A and B) in the asymmetric unit. In the central ring systems of both mol-ecules, the tetra-hydro-furan rings adopt envelope conformations, the pyrrolidine rings adopt a twisted-envelope conformation and the six-membered ring is in a boat conformation. In mol-ecules A and B, the nine-membered groups attached to the central ring system are essentially planar (r.m.s. deviations of 0.002 and 0.003 Å, respectively). They form dihedral angles of 64.97 (9) and 56.06 (10)°, respectively, with the phenyl rings. In the crystal, strong inter-molecular O-H⋯O hydrogen bonds and weak inter-molecular C-H⋯O contacts link the mol-ecules, forming a three-dimensional network. In addition weak π-π stacking inter-actions [centroid-to centroid distance = 3.7124 (13) Å] between the pyrrolidine rings of the nine-membered groups of A mol-ecules are observed. Hirshfeld surface analysis and two-dimensional fingerprint plots were used to qu-antify the inter-molecular inter-actions present in the crystal, indicating that the environments of the two mol-ecules are very similar. The most important contributions for the crystal packing are from H⋯H (55.8% for mol-ecule A and 53.5% for mol-ecule B), O⋯H/H⋯O (24.5% for mol-ecule A and 26.3% for mol-ecule B) and C⋯H/H⋯C (12.6% for mol-ecule A and 15.7% for mol-ecule B) inter-actions.

Crystal structure and Hirshfeld surface analysis of 2-benzyl-4,5-di-bromo-2,3,3a,4,5,6,7,7a-octa-hydro-3a,6-ep-oxy-1H-isoindol-1-one

The title compound, C15H15Br2NO2, crystallizes with two mol-ecules in the asymmetric unit of the unit cell. In both mol-ecules, the tetra-hydro-furan rings adopt an envelope conformation with the O atom as the flap and the pyrrolidine rings adopt an envelope conformation. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds, forming sheets lying parallel to the (002) plane. These sheets are connected only by weak van der Waals inter-actions. The most important contributions to the surface contacts are from H⋯H (44.6%), Br⋯H/H⋯Br (24.1%), O⋯H/H⋯O (13.5%) and C⋯H/H⋯C (11.2%) inter-actions, as concluded from a Hirshfeld surface analysis.

Crystal structure and Hirshfeld surface analysis of 4,5-di-bromo-6-methyl-2-phenyl-2,3,3a,4,5,6,7,7a-octa-hydro-3a,6-ep-oxy-1H-isoindol-1-one

In the title compound, C15H15Br2NO2, two bridged tetra-hydro-furan rings adopt envelope conformations with the O atom as the flap. The pyrrolidine ring also adopts an envelope conformation with the spiro C atom as the flap. In the crystal, the mol-ecules are linked into dimers by pairs of C-H⋯O hydrogen bonds, thus generating R 2 2(18) rings. The crystal packing is dominated by H⋯H, Br⋯H, H⋯π and Br⋯π inter-actions. One of the Br atoms is disordered over two sites with occupation ratio of 0.833 (8):0.167 (8).

Crystal structure and Hirshfeld surface analysis of ethyl (4R,4aS)-2-methyl-5,8-dioxo-6-phenyl-4a,5,6,7,7a,8-hexa-hydro-4H-furo[2,3-f]iso-indole-4-carboxyl-ate

In the title compound, C20H19NO5, the central six-membered ring has a slightly distorted half-chair conformation, with puckering parameters of Q T = 0.3387 (11) Å, θ = 49.11 (19)° and φ = 167.3 (2)°. The conformation of the fused pyrrolidine ring is that of an envelope. Mol-ecules are connected by inter-molecular C-H⋯O hydrogen bonds, C-H⋯π inter-actions and π-π stacking inter-actions [centroid-to-centroid distance = 3.9536 (11) Å, with a slippage of 2.047 Å], forming a three-dimensional network. The most important contributions to the surface contacts are from H⋯H (46.3%), O⋯H/H⋯O (31.5%) and C⋯H/H⋯C (17.3%) inter-actions, as concluded from a Hirshfeld surface analysis.

Stacking interactions of resonance-assisted hydrogen-bridged rings and C6-aromatic rings

Stacking interactions between six-membered resonance-assisted hydrogen-bridged (RAHB) rings and C6-aromatic rings were systematically studied by analyzing crystal structures in the Cambridge Structural Database (CSD). The interaction energies were calculated by quantum-chemical methods. Although the interactions are stronger than benzene/benzene stacking interactions (-2.7 kcal mol-1), the strongest calculated RAHB/benzene stacking interaction (-3.7 kcal mol-1) is significantly weaker than the strongest calculated RAHB/RAHB stacking interaction (-4.7 kcal mol-1), but for a particular composition of RAHB rings, RAHB/benzene stacking interactions can be weaker or stronger than the corresponding RAHB/RAHB stacking interactions. They are also weaker than the strongest calculated stacking interaction between five-membered saturated hydrogen-bridged rings and benzene (-4.4 kcal mol-1) and between two five-membered saturated hydrogen-bridged rings (-4.9 kcal mol-1). SAPT energy decomposition analyses show that the strongest attractive term in RAHB/benzene stacking interactions is dispersion, however, it is mostly canceled by a repulsive exchange term; hence the geometries of the most stable structures are determined by an electrostatic term.

Lead(ii) coordination polymers driven by pyridine-hydrazine donors: from anion-guided self-assembly to structural features

This work unveils an indispensable role of London dispersion forces and relativistic effects in tetrel and covalent bonds of the type Pb–X (X = O, N, S, I), which drives formation of extended architectures of lead(ii) coordination polymers.

Crystal structure and Hirshfeld surface analysis of di-iodido-{N'-[(E)-(phen-yl)(pyridin-2-yl-κN)methylidene]pyridine-2-carbohydrazide-κ2 N',O}cadmium(II)

In each of the two independent mol-ecules in the asymmetric unit of the title compound, [CdI2(C18H14N4O)], the N,O,N'-tridentate N'-[(E)-(phen-yl)(pyridin-2-yl-κN)methyl-idene]pyridine-2-carbohydrazide ligand and two iodide anions form an I2N2O penta-coordination sphere, with a distorted square-pyramidal geometry, with an I atom in the apical position. Both mol-ecules feature an intra-molecular N-H⋯N hydrogen bond. In the crystal, weak aromatic π-π stacking inter-actions [centroid-centroid separation = 3.830 (2) Å] link the mol-ecules into dimers.

Modulation of coordination in pincer-type isonicotinohydrazone Schiff base ligands by proton transfer

We report the synthesis and X-ray characterization and theoretical study of two Hg(ii) complexes with pincer-type isonicotinohydrazone Schiff base ligands to analyze chelate-ring π-stacked assemblies.

Diethylaminophenyl-based Schiff base Cu(ii) and V(iv) complexes: experimental and theoretical studies and cytotoxicity assays

A combined experimental and theoretical study and cytotoxicity assays of diethylaminophenyl-based Schiff base Cu(ii) and VO(iv) complexes are reported. The Cu(ii) complex shows interesting chelate ring⋯π interactions in the crystal structure.

Crystal structure of (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazineyl) terephthalic acid-dimethylsulfoxide (1/1), C18H15N3O6 ⋅ C2H6OS

C18H15N3O6 ⋅ C2H6OS, P21/c (no. 14), a = 15.762(9) Å, v = 6.013(4) Å, c = 22.264(11) Å, β = 103.522(19)°, V = 2052(2) Å3, Z = 4, Rgt(F) = 0.0484, wRref(F2) = 0.1348, T = 296(2) K.

Chelated metal ions modulate the strength and geometry of stacking interactions: energies and potential energy surfaces for chelate-chelate stacking

Quantum chemical calculations were performed on model systems of stacking interactions between the acac type chelate rings of nickel, palladium, and platinum. CCSD(T)/CBS calculations showed that chelate-chelate stacking interactions are significantly stronger than chelate-aryl and aryl-aryl stacking interactions. Interaction energy surfaces were calculated at the LC-ωPBE-D3BJ/aug-cc-pVDZ level, which gives energies in good agreement with CCSD(T)/CBS. The stacking of chelates in an antiparallel orientation is stronger than the stacking in a parallel orientation, which is in agreement with the larger number of antiparallel stacked chelates in crystal structures from the Cambridge Structural Database. The strongest antiparallel chelate-chelate stacking interaction is formed between two platinum chelates, with a CCSD(T)/CBS interaction energy of -9.70 kcal mol-1, while the strongest stacking between two palladium chelates and two nickel chelates has CCSD(T)/CBS energies of -9.21 kcal mol-1 and -9.50 kcal mol-1, respectively. The strongest parallel chelate-chelate stacking was found for palladium chelates, with a LC-ωPBE-D3BJ/aug-cc-pVDZ energy of -6.51 kcal mol-1. The geometries of the potential surface minima are not the same for the three metals. The geometries of the minima are governed by electrostatic interactions, which are the ones determining the positions of the energy minima. Electrostatic interactions are governed by different electrostatic potentials above the metals, which are very positive for nickel, slightly positive for palladium, and slightly negative for platinum.

Recurrent supramolecular motifs in discrete complexes and coordination polymers based on mercury halides: prevalence of chelate ring stacking and substituent effects

We report the synthesis, X-ray characterization and DFT study of five Hg(ii) complexes with Schiff bases containing a nicotinohydrazide core to explore the formation of chelate-ring π-stacking interactions.

Quantifying conventional C–H⋯π(aryl) and unconventional C–H⋯π(chelate) interactions in dinuclear Cu(ii) complexes: experimental observations, Hirshfeld surface and theoretical DFT study

Conventional C–H⋯π(aryl) and unconventional C–H⋯π(chelate) interactions are explored in detail.

Two zinc(II) coordination complexes based on an asymmetric multidentate ligand: syntheses, structures, selective fluorescence sensing of iron(III) ions and thermal analyses

The rational selection of ligands is vitally important in the construction of coordination complexes. Two novel ZnII complexes, namely bis(acetato-κO)bis[1-(1H-benzotriazol-1-ylmethyl)-2-propyl-1H-imidazole-κN 3]zinc(II) monohydrate, [Zn(C13H15N5)2(C2H3O2)2]·H2O, (1), and bis(azido-κN 1)bis[1-(1H-benzotriazol-1-ylmethyl)-2-propyl-1H-imidazole-κN 3]zinc(II), [Zn(C13H15N5)2(N3)2], (2), constructed from the asymmetric multidentate imidazole ligand, have been synthesized under mild conditions and characterized by elemental analyses, IR spectroscopy and single-crystal X-ray diffraction analysis. Both complexes exhibit a three-dimensional supramolecular network directed by different intermolecular interactions between discrete mononuclear units. The complexes were also investigated by fluorescence and thermal analyses. The experimental results show that (1) is a promising fluorescence sensor for detecting Fe3+ ions and (2) is effective as an accelerator of the thermal decomposition of ammonium perchlorate.

Crystal structures of di-bromido-{N-[(pyridin-2-yl-κN)methyl-idene]picolinohydrazide-κ2N',O}cadmium methanol monosolvate and di-iodido{N-[(pyridin-2-yl-κN)methyl-idene]picolinohydrazide-κ2N',O}cadmium

The title compounds, [CdBr2(C12H10N4O)]·CH3OH, (I), and [CdI2(C12H10N4O)], (II), are cadmium bromide and cadmium iodide complexes of the ligand (E)-N'-(pyridin-2-yl-methyl-ene)picolinohydrazide. Complex (I) crystallizes as the methanol monosolvate. In both compounds, the Cd2+ cation is ligated by one O atom and two N atoms of the tridentate ligand, and by two bromide anions forming a Br2N2O penta-coordination sphere for (I), and by two iodide anions forming an I2N2O penta-coordination sphere for (II), both with a distorted square-pyramidal geometry. In the crystal of complex (I), mol-ecules are linked by pairs of N-H⋯O and O-H⋯Br hydrogen bonds, involving the solvent mol-ecule, forming dimeric units, which are linked by C-H⋯Br hydrogen bonds forming layers parallel to (101). In the crystal of complex (II), mol-ecules are linked by N-H⋯I hydrogen bonds, forming chains propagating along [010]. In complex (II), measured at room temperature, the two iodide anions are each disordered over two sites; the refined occupancy ratio is 0.75 (2):0.25 (2).