Synthesis, crystal structure and Hirshfeld surface analysis of 2-phenyl-3-(prop-2-yn-1-yl-oxy)quin-oxaline

In the title compound, C17H12N2O, the quinoxaline moiety shows deviations of 0.0288 (7) to -0.0370 (7) Å from the mean plane (r.m.s. deviation of fitted atoms = 0.0223 Å). In the crystal, corrugated layers two mol-ecules thick are formed by C-H⋯N hydrogen bonds and π-stacking inter-actions.

Crystal structure and Hirshfeld surface analysis of ethyl 2-(7-chloro-3-methyl-2-oxo-1,2-di-hydro-quinoxalin-1-yl)acetate

The quinoxaline moiety in the title mol-ecule, C13H13ClN2O3, is almost planar (r.m.s. deviation of the fitted atoms = 0.033 Å). In the crystal, C-H⋯O hydrogen bonds plus slipped π-stacking and C-H⋯π(ring) inter-actions generate chains of mol-ecules extending along the b-axis direction. The chains are connected by additional C-H⋯O hydrogen bonds. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H⋯H (37.6%), H⋯O/O⋯H (22.7%) and H⋯Cl/Cl⋯H (13.1%) inter-actions.

Crystal structure and Hirshfeld surface analysis of 3-phenyl-1-{3-[(3-phenyl-quinoxalin-2-yl)-oxy]prop-yl}-1,2-di-hydro-quinoxalin-2-one

In the title compound, C31H24N4O2, the quinoxaline units are distinctly non-planar and twisted end-to-end. In the crystal, C-H⋯O and C-H⋯N hydrogen bonds link the mol-ecules into chains extending along the a-axis direction. The chains are linked through π-stacking inter-actions between inversion-related quinoxaline moieties.

Substitution reactions in the acenaphthene analog of quino[7,8-h]quinoline and an unusual synthesis of the corresponding acenaphthylenes by tele-elimination

The possibility of functionalization of dipyrido[3,2-e:2',3'-h]acenaphthene containing a quino[7,8-h]quinoline fragment and being a highly basic diazine analog of 1,8-bis(dimethylamino)naphthalene ("proton sponge") has been studied for the first time. In addition to the pronounced tendency of the title compound to form associates with an intramolecular hydrogen bond of the NHN type (new examples with the participation of pyridine rings, including self-associates are shown) and its inertness to amination reactions of the pyridine rings, the naphthalene core at positions 5(8) and the CH2CH2 bridge (dehydrogenation) undergo chemical modifications under mild conditions, giving the corresponding acenaphthylenes. The latter can also be obtained in an unusual way by tele-elimination from 5,8-dibromodipyridoacenaphthene by reaction with neutral or anionic bases.

Synthesis and crystal structure of a cadmium(II) coordination polymer based on 4,4'-(1H-1,2,4-triazole-3,5-di-yl)dibenzoate

The asymmetric unit of the title compound, catena-poly[[[aqua-bis-(pyridine-κN)cadmium(II)]-μ2-4,4'-(1H-1,2,4-triazole-3,5-di-yl)dibenzoato-κ4 O,O':O'',O'''] 4.5-hydrate], {[Cd(C16H9N3O4)(C5H5N)2(H2O)]·4.5H2O}n or {[Cd(bct)(py)2(H2O)]·4.5H2O}n (I), consists of a Cd2+ cation coordinated to one bct2- carboxyl-ate dianion, two mol-ecules of pyridine and a water mol-ecule as well as four and a half water mol-ecules of crystallization. The metal ion in I possesses a penta-gonal-bipyramidal environment with the four O atoms of the two bidentately coordinated carboxyl-ate groups and the N atom of a pyridine mol-ecule forming the O4N equatorial plane, while the N atom of another pyridine ligand and the O atom of the water mol-ecule occupy the axial positions. The bct2- bridging ligand connects two metal ions via its carb-oxy-lic groups, resulting in the formation of a parallel linear polymeric chain running along the [11] direction. The coordinated water mol-ecule of one chain forms a strong O-H⋯O hydrogen bond with the carboxyl-ate O atom of a neighboring chain, leading to the formation of double chains with a closest distance of 5.425 (7) Å between the cadmium ions belonging to different chains. Aromatic π-π stacking inter-actions between the benzene fragments of the anions as well as between the coordinated pyridine mol-ecules belonging to different chains results in the formation of sheets oriented parallel to the (01) plane. As a result of hydrogen-bonding inter-actions involving the water mol-ecules of crystallization, the sheets are joined together in a three-dimensional network.

Crystal structure, Hirshfeld surface analysis, crystal voids, inter-action energy calculations and energy frameworks, and DFT calculations of 1-(4-methyl-benz-yl)in-do-line-2,3-dione

The in-do-line portion of the title mol-ecule, C16H13NO2, is planar. In the crystal, a layer structure is generated by C-H⋯O hydrogen bonds and C-H⋯π(ring), π-stacking and C=O⋯π(ring) inter-actions. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (43.0%), H⋯C/C⋯H (25.0%) and H⋯O/O⋯H (22.8%) inter-actions. Hydrogen bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing. The volume of the crystal voids and the percentage of free space were calculated to be 120.52 Å3 and 9.64%, respectively, showing that there is no large cavity in the crystal packing. Evaluation of the electrostatic, dispersion and total energy frameworks indicate that the stabilization is dominated by the dispersion energy contributions in the title compound. Moreover, the DFT-optimized structure at the B3LYP/6-311G(d,p) level is compared with the experimentally determined mol-ecular structure in the solid state.

Crystal structure, Hirshfeld surface and crystal void analysis, inter-molecular inter-action energies, DFT calculations and energy frameworks of 2H-benzo[b][1,4]thia-zin-3(4H)-one 1,1-dioxide

In the title mol-ecule, C8H7NO3S, the nitro-gen atom has a planar environment, and the thia-zine ring exhibits a screw-boat conformation. In the crystal, corrugated layers of mol-ecules parallel to the ab plane are formed by N-H⋯O and C-H⋯O hydrogen bonds together with C-H⋯π(ring) and S=O⋯π(ring) inter-actions. The layers are connected by additional C-H⋯O hydrogen bonds and π-stacking inter-actions. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H⋯O/O⋯H (49.4%), H⋯H (23.0%) and H⋯C/C⋯H (14.1%) inter-actions. The volume of the crystal voids and the percentage of free space were calculated as 75.4 Å3 and 9.3%. Density functional theory (DFT) computations revealed N-H⋯O and C-H⋯O hydrogen-bonding energies of 43.3, 34.7 and 34.4 kJ mol-1, respectively. Evaluation of the electrostatic, dispersion and total energy frameworks indicate that the stabilization is dominated via the electrostatic energy contribution. Moreover, the DFT-optimized structure at the B3LYP/ 6-311 G(d,p) level is compared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

2-[4-(2-Chloro-benz-yl)-3-methyl-6-oxo-1,6-di-hydro-pyridazin-1-yl]-N-(4-fluoro-phen-yl)acetamide

The conformation of the title mol-ecule, C20H17ClFN3O2, is partly determined by an intra-molecular C-H⋯O hydrogen bond, which leads to a dihedral angle of 14.7 (4)° between the fluoro-benzene ring and the acetamide group. The 2-chloro-benzyl group is rotationally disordered over two orientations in a 0.656 (2): 0.344 (2) ratio. In the crystal, a layered structure is formed by N-H⋯O, C-H⋯O and C-H⋯F hydrogen bonds plus slipped π-π stacking inter-actions.

Crystal structure and Hirshfeld surface analysis of 3-eth-oxy-1-ethyl-6-nitro-quinoxalin-2(1H)-one

The asymmetric unit of the title compound, C12H13N3O4, consists of two mol-ecules differing to a small degree in their conformations. In the crystal, layers of mol-ecules are connected by weak C-H⋯O hydrogen bonds and slipped π-stacking inter-actions. These layers lie parallel to (10) and are stacked along the normal to that plane. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing arise from H⋯H (43.5%) and H⋯O/O⋯H (30.8%) contacts. The density functional theory (DFT) optimized structure of the title compound at the B3LYP/ 6-311 G(d,p) level agrees well with the experimentally determined mol-ecular structure in the solid state.

Crystal structure, Hirshfeld surface analysis, inter-action energy and energy framework calculations, as well as density functional theory (DFT) com-putation, of methyl 2-oxo-1-(prop-2-yn-yl)-1,2-di-hydro-quinoline-4-carboxyl-ate

In the title mol-ecule, C14H11NO3, the di-hydro-quinoline core deviates slightly from planarity, indicated by the dihedral angle of 1.07 (3)° between the two six-membered rings. In the crystal, layers of mol-ecules almost parallel to the bc plane are formed by C-H⋯O hydro-gen bonds. These are joined by π-π stacking inter-actions. A Hirshfeld surface analysis revealed that the most important contributions to the crystal packing are from H⋯H (36.0%), H⋯C/C⋯H (28.9%) and H⋯O/O⋯H (23.5%) inter-actions. The evaluation of the electrostatic, dispersion and total energy frameworks indicates that the stabilization is dominated by the dispersion energy contribution. Moreover, the mol-ecular structure optimized by density functional theory (DFT) at the B3LYP/6-311G(d,p) level is com-pared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

9,10-Bis(iodo-ethyn-yl)anthracene

The title compound, C18H8I2, is an ethynyl-substituted anthracene. The C-C-I bond angles deviate from 180°, being affected by inter-molecular I⋯π inter-actions. These inter-actions form a two-dimensional supra-molecular structure further supported by offset π-π stacking of neighboring anthracene moieties.

Synthesis, crystal structure and Hirshfeld surface analysis of bis-(caffeinium) hexa-chlorido-platinum(IV) in comparison with some related compounds

The mol-ecular and crystal structure of the title compound, (C8H11N4O2)2[PtCl6], synthesized from hexa-chloro-platinic acid and caffeine in methanol, was studied by single-crystal X-ray diffraction. The caffeinium cations form a double layer via hydrogen bonds and π-stacking inter-actions. The Hirshfeld surface analysis showed that the largest contribution to the crystal packing is made by H⋯H (31.2%), H⋯Cl/Cl⋯H (22.6%), O⋯H/H⋯O (21.9%) contacts for the cation and H⋯Cl/Cl⋯H (79.3%) contacts for the anion.

Crystal structures, Hirshfeld analysis, and energy framework analysis of two differently 3'-substituted 4-methylchalcones: 3'-(N=CHC6H4-p-CH3)-4-methylchalcone and 3'-(NHCOCH3)-4-methylchalcone

Two crystal structures of chalcones, or 1,3-diarylprop-2-en-1-ones, are presented; both contain a p-methyl substitution on the 3-Ring, but differ with respect to the m-substitution on the 1-Ring. Their systematic names are (2E)-3-(4-methylphenyl)-1-(3-{[(4-methylphenyl)methylidene]amino}phenyl)prop-2-en-1-one (C₂₄H₂₁NO) and N-{3-[(2E)-3-(4-methylphenyl)prop-2-enoyl]phenyl}acetamide (C₁₈H₁₇NO₂), which are abbreviated as 3'-(N=CHC₆H₄-p-CH₃)-4-methylchalcone and 3'-(NHCOCH₃)-4-methylchalcone, respectively. Both chalcones represent the first reported acetamide-substituted and imino-substituted chalcone crystal structures, adding to the robust library of chalcone structures within the Cambridge Structural Database. The crystal structure of 3'-(N=CHC₆H₄-p-CH₃)-4-methylchalcone exhibits close contacts between the enone O atom and the substituent arene ring, in addition to C...C interactions between the substituent arene rings. The structure of 3'-(NHCOCH₃)-4-methylchalcone exhibits a unique interaction between the enone O atom and the 1-Ring substituent, contributing to its antiparallel crystal packing. In addition, both structures exhibit π-stacking, which occurs between the 1-Ring and R-Ring for 3'-(N=CHC₆H₄-p-CH₃)-4-methylchalcone, and between the 1-Ring and 3-Ring for 3'-(NHCOCH₃)-4-methylchalcone.

Solvatochromism and solution π-stacking of N-(4-pyridyl)-1,8-naphthalimide and its corresponding triruthenium coordination complex

Due to the scarcity of spectroscopic studies on metal-coordinated naphthalimides, and aiming to investigate fundamental spectroscopic aspects, we have described here the aggregates of N-(4-pyridyl)-1,8-naphthalimide (NI-py) in solution as well as solvatochromism displayed by it and by the coordination compounds [Ru₃O(CH₃COO)₆(NI-py)₃]ⁿ, n = +1 or 0. Based both on theoretical calculations and luminescence spectra, we demonstrated that in aqueous media, the NI-py π-stacking is thermodynamically favored, suggesting a preferable conformation where the pyridine and naphthalene moieties of two NI-py molecules are parallel to each other, but are not co-planar within an individual molecule, due to steric hindrance. The NI-py ππ* band displayed positive solvatochromism, to which the major contribution was the Catalan's SP parameter (solvent polarizability). This observation is fully consistent with the extended π-electron cloud of the NI-py naphthalene ring. However, a secondary contribution of the SA (solvent acidity) was also observed, owing to the electron pairs available at the N-heteroatom of the pyridine rings and at the carbonyl-group oxygen atoms. Finally, the multiparametric solvent effect analysis indicated that the electronic coupling between coordinated NI-py and the metallic core is modulated by the charge of the [Ru₃O(CH₃COO)₆] core, being higher for the reduced species [Ru₃O(CH₃COO)₆(NI-py)]⁰. In addition, in this reduced species, there is no overlap between NI-py ππ* and the [Ru₃O(CH₃COO)₆] charge transfer (CT) transitions, leading to the observation of the dependence of the CT energy with the SdP parameter (solvent dipolarity) since the CT transition implies in a charge-separation state.

5,6,7,8-Tetra-hydro-[1,2,4]triazolo[5,1-b]quinazolin-9(4H)-one

The triazole ring in the title mol-ecule, C₉H₁₀N₄O, is not quite coplanar with the six-membered ring to which it is fused, the dihedral angle between the two least-squares planes being 2.52 (6)°. In the crystal, a layered structure is formed by N-H⋯N and C-H⋯O hydrogen bonds plus slipped π-stacking inter-actions, with the fused cyclo-hexene rings projecting to either side.

Synthesis, crystal structure and Hirshfeld surface analysis of (E)-benzo[d][1,3]dioxole-5-carbaldehyde oxime

The asymmetric unit of the title mol-ecule, C₈H₇NO₃, consists of two mol-ecules differing slightly in conformation and in their inter-molecular inter-actions in the solid. The dihedral angle between the benzene and dioxolane rings is 0.20 (7)° in one mol-ecule and 0.31 (7)° in the other. In the crystal, the two mol-ecules are linked into dimers through pairwise O-H⋯N hydrogen bonds, with these units being formed into stacks by two different sets of aromatic π-stacking inter-actions. The stacks are connected by C-H⋯O hydrogen bonds. A Hirshfeld surface analysis indicates that the most significant contacts in the crystal packing are H⋯O/O⋯H (36.7%), H⋯H (32.2%) and C⋯H/H⋯C (12.7%).

Design and Synthesis of Cofacially-Arrayed Polyfluorene Wires for Electron and Energy Transfer Studies

A study of cofacially arrayed π-systems is of particular importance for the design of functional materials for efficient long-range intra-chain charge transfer through the bulk semiconducting materials in the layers of photovoltaic devices. The effect of π-stacking between a pair of aromatic rings has been mainly studied in the form of cyclophanes, where aromatic rings are forced into a sandwich-like geometry, which extensively deforms the aromatic rings from planarity. The synthetic difficulties associated with the preparation of cyclophane-like structures has prevented the synthesis of many examples of their multi-layered analogues. Moreover, the few available multi-layered cyclophanes are not readily amenable to the structural modification required for the construction of D-spacer-A triads needed to explore mechanisms of electron and energy transfer. In this review, we recount how a detailed experimental and computational analysis of 1,3-diarylalkanes led to the design of a new class of cofacially arrayed polyfluorenes that retain their π-stacked structure. Thus, efficient synthetic strategies have been established for the ready preparation of monodisperse polyfluorenes with up to six π-stacked fluorenes, which afford ready access to D-spacer-A triads by linking donor and acceptor groups to the polyfluorene spacers via single methylenes. Detailed ¹H NMR spectroscopy, X-ray crystallography, electrochemistry, and He(I) photoelectron spectroscopy of F2-F6 have confirmed the rigid cofacial stacking of multiple fluorenes in F2-F6, despite the presence of rotatable C-C bonds. These polyfluorenes (F2-F6) form stable cation radicals in which a single hole is delocalized amongst the stacked fluorenes, as judged by the presence of intense charge-resonance transition in their optical spectra. Interestingly, these studies also discern that delocalization of a single cationic charge could occur over multiple fluorene rings in F2-F6, while the exciton is likely localized only onto two fluorenes in F2-F6. Facile synthesis of the D-spacer-A triads allowed us to demonstrate that efficient triplet energy transfer can occur through π-stacked polyfluorenes; the mechanism of energy transfer crosses over from tunneling to hopping with increasing number of fluorenes in the polyfluorene spacer. We suggest that the development of rigidly held π-stacked polyfluorenes, described herein, with well-defined redox and optoelectronic properties provides an ideal scaffold for the study of electron and energy transfer in D-spacer-A triads, where the Fn spacers serve as models for cofacially stacked π-systems.

π-Complexation and C-H hydrogen bonding in the formation of colored cocrystals

The present study evaluates the potential combination of charge-transfer electron-donor-acceptor π-π complexation and C-H hydrogen bonding to form colored cocrystals. The crystal structures of the red 1:1 cocrystals formed from the isomeric pyridines 4- and 3-{2-[4-(dimethylamino)phenyl]ethynyl}pyridine with 1-[2-(3,5-dinitrophenyl)ethynyl]-2,3,5,6-tetrafluorobenzene, both C₁₄H₄F₄N₂O₄·C₁₅H₁₄N₂, are reported. Intermolecular interaction energy calculations confirm that π-stacking interactions dominate the intermolecular interactions within each crystal structure. The close contacts revealed by Hirshfeld surface calculations are predominantly C-H interactions with N, O, and F atoms.

Oxanorbornene-Fused Phenazine-Pyrene Scaffolds with Different Configurations

New molecular scaffolds of C-, Z- and box-shaped configurations are constructed by fusing phenazine and pyrene units with oxanorbornene. As revealed by X-ray crystallography, the C-shaped molecules exhibit two interesting π-π stacking modes of phenazine depending on the substituting groups, and the box-shaped molecule accommodates two chloroform molecules in the cavity and forms H-bonds with another four molecules of chloroform. The C- and Z-shaped molecules as a pair of diastereomers exhibit almost the same charge transfer absorption and emission including positive solvatochromism, indicating that the intramolecular charge transfer between pyrene (π-donor) and phenazine (π-acceptor) is not dependent on the overall molecular geometry.

2-Bromo-6-hydrazinyl-pyridine

The title compound, C₅H₆BrN₃, crystallizes in the ortho-rhom-bic space group P2₁2₁2₁ with two mol-ecules with different conformations in the asymmetric unit. In the crystal, N-H⋯N and bifurcated N-H⋯(N,N) hydrogen bonds link the mol-ecules into [100] chains; a short Br⋯Br halogen bond and π-π stacking inter-actions are also observed.

Benzenetriimide-Based Molecular Conductor with Antiferro- to Ferromagnetic Switching Induced by Structural Change of π-stacked Array

Benzenetriimide (BTI) is a promising building block for materials chemistry due to its characteristic 3-fold symmetry and redox properties, whereas little is known about its conductive and magnetic properties. In this study, we synthesized three charge-transfer complexes based on N,N',N''-trimethylbenzenetriimide (BTI-Me). One of the complexes contains isolated dimers of BTI-Me radical anion (BTI-Me•-), while the other two have the infinite π-stacked array of BTI-Me with the formal charge of -0.5. The latter two complexes did not show metallic behavior but showed semiconducting behavior due to the characteristic insulation in one-dimensional electron system, so-called charge ordering and dimer-Mott insulation. The magnetic susceptibility of the complex in dimer-Mott state exhibits an unusual transition from antiferromagnetic to ferromagnetic spin states with the hysteresis loop of 15 K derived from the structural phase transition around 130 K. These properties were also supported by DFT calculations.

A first-order phase transition in Blatter's radical at high pressure

The crystal structure of Blatter's radical (1,3-diphenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl) has been investigated between ambient pressure and 6.07 GPa. The sample remains in a compressed form of the ambient-pressure phase up to 5.34 GPa, the largest direction of strain being parallel to the direction of π-stacking interactions. The bulk modulus is 7.4 (6) GPa, with a pressure derivative equal to 9.33 (11). As pressure increases, the phenyl groups attached to the N1 and C3 positions of the triazinyl moieties of neighbouring pairs of molecules approach each other, causing the former to begin to rotate between 3.42 to 5.34 GPa. The onset of this phenyl rotation may be interpreted as a second-order phase transition which introduces a new mode for accommodating pressure. It is premonitory to a first-order isosymmetric phase transition which occurs on increasing pressure from 5.34 to 5.54 GPa. Although the phase transition is driven by volume minimization, rather than relief of unfavourable contacts, it is accompanied by a sharp jump in the orientation of the rotation angle of the phenyl group. DFT calculations suggest that the adoption of a more planar conformation by the triazinyl moiety at the phase transition can be attributed to relief of intramolecular H...H contacts at the transition. Although no dimerization of the radicals occurs, the π-stacking interactions are compressed by 0.341 (3) Å between ambient pressure and 6.07 GPa.

Differences in thermal expansion and motion ability for herringbone and face-to-face π-stacked solids

A series of aromatic organic molecules functionalized with different halogen atoms (I/ Br), motion-capable groups (olefin, azo or imine) and molecular length were designed and synthesized. The molecules self-assemble in the solid state through halogen bonding and exhibit molecular packing sustained by either herringbone or face-to-face π-stacking, two common motifs in organic semiconductor molecules. Interestingly, dynamic pedal motion is only achieved in solids with herringbone packing. On average, solids with herringbone packing exhibit larger thermal expansion within the halogen-bonded sheets due to motion occurrence and molecular twisting, whereas molecules with face-to-face π-stacking do not undergo motion or twisting. Thermal expansion along the π-stacked direction is surprisingly similar, but slightly larger for the face-to-face π-stacked solids due to larger changes in π-stacking distances with temperature changes. The results speak to the importance of crystal packing and intermolecular interaction strength when designing aromatic-based solids for organic electronics applications.

Strong π-stacking causes unusually large anisotropic thermal expansion and thermochromism

π-stacking in ground-state dimers/trimers/tetramers of N-butoxyphenyl(naphthalene)diimide (BNDI) exceeds 50 kcal ⋅ mol^-1 in strength, drastically surpassing that for the ^*3[pyrene]₂ excimer (∼30 kcal ⋅ mol^-1; formal bond order = 1) and similar to other weak-to-moderate classical covalent bonds. Cooperative π-stacking in triclinic (BNDI-T) and monoclinic (BNDI-M) polymorphs effects unusually large linear thermal expansion coefficients (α _a , α _b , α _c , β) of (452, -16.8, -154, 273) × 10^-6 ⋅ K^-1 and (70.1, -44.7, 163, 177) × 10^-6 ⋅ K^-1, respectively. BNDI-T exhibits highly reversible thermochromism over a 300-K range, manifest by color changes from orange (ambient temperature) toward red (cryogenic temperatures) or yellow (375 K), with repeated thermal cycling sustained for over at least 2 y.

Unexpected Charge Effects Strengthen π-Stacking Pancake Bonding

Phenalenyls (PLYs) are important synthons in many functional and electronic materials, which often display favorable molecule-to-molecule overlap for electron or hole transport. They also serve as a prototype for π-stacking pancake bonding based on two-electron multicenter bonding (2e/mc). Unexpected near-doubling of the binding energy is obtained for the positively charged PLY2 + dimer with an effect similar to that seen for the positively charged olympicenyl (OPY) radical dimer. This charge effect is reversed for the perfluorinated (PF) dimers, and the negatively charged perfluorinated (PF) dimers PF-PLY2 - and PF-OPY2 - become strongly bound. Long-range interactions reflect these differences. Also surprising is that in this case the pancake bonding corresponds to single-electron (1e/mc) or a three-electron (3e/mc) multicenter bonding in contrast to the 2e/mc bonding that occurs for the neutral radical dimers. The strong preference for a large intermolecular overlap is maintained in these charged dimers. Importantly, the preference for π-bonding in the charged dimers compared to σ-bonding is strongly enhanced relative to the neutral PLY dimers.

Synthesis, Biological Evaluation, and Computational Analysis of Biaryl Side-Chain Analogs of Solithromycin

There is an urgent need for new antibiotics to mitigate the existential threat posed by antibiotic resistance. Within the ketolide class, solithromycin has emerged as one of the most promising candidates for further development. Crystallographic studies of bacterial ribosomes and ribosomal subunits complexed with solithromycin have shed light on the nature of molecular interactions (π-stacking and H-bonding) between from the biaryl side-chain of the drug and key residues in the 50S ribosomal subunit. We have designed and synthesized a library of solithromycin analogs to study their structure-activity relationships (SAR) in tandem with new computational studies. The biological activity of each analog was evaluated in terms of ribosomal affinity (K_d determined by fluorescence polarization), as well as minimum inhibitory concentration assays (MICs). Density functional theory (DFT) studies of a simple binding site model identify key H-bonding interactions that modulate the potency of solithromycin analogs.

π-Stacking Stopper-Macrocycle Stabilized Dynamically Interlocked [2]Rotaxanes

The synthesis of mechanically interlocked molecules is valuable due to their unique topologies. With π-stacking intercomponent interaction, e.g., phenanthroline and anthracene, novel [2]rotaxanes have been synthesized by dynamic imine clipping reaction. Their X-ray crystal structures indicate the π-stackings between the anthracene moiety (stopper) on the thread and the (hetero)aromatic rings at the macrocycle of the rotaxanes. Moreover, the length of glycol chains affects the extra π-stacking intercomponent interactions between the phenyl groups and the dimethoxy phenyl groups on the thread. Dynamic combinatorial library has shown at best 84% distribution of anthracene-threaded phenanthroline-based rotaxane, coinciding with the crystallography in that the additional π-stacking intercomponent interactions could increase the thermodynamic stability and selectivity of the rotaxanes.

Crystal structure, Hirshfeld surface analysis and inter-action energy calculation of 4-(furan-2-yl)-2-(6-methyl-2,4-dioxo-pyran-3-yl-idene)-2,3,4,5-tetra-hydro-1H-1,5-benzodiazepine

The title compound {systematic name: (S,E)-3-[4-(furan-2-yl)-2,3,4,5-tetra-hydro-1H-benzo[b][1,4]diazepin-2-yl-idene]-6-methyl-2H-pyran-2,4(3H)-dione}, C19H16N2O4, is constructed from a benzodiazepine ring system linked to furan and pendant di-hydro-pyran rings, where the benzene and furan rings are oriented at a dihedral angle of 48.7 (2)°. The pyran ring is modestly non-planar [largest deviation of 0.029 (4) Å from the least-squares plane] while the tetra-hydro-diazepine ring adopts a boat conformation. The rotational orientation of the pendant di-hydro-pyran ring is partially determined by an intra-molecular N-HDiazp⋯ODhydp (Diazp = diazepine and Dhydp = di-hydro-pyran) hydrogen bond. In the crystal, layers of mol-ecules parallel to the bc plane are formed by N-HDiazp⋯ODhydp hydrogen bonds and slipped π-π stacking inter-actions. The layers are connected by additional slipped π-π stacking inter-actions. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (46.8%), H⋯O/O⋯H (23.5%) and H⋯C/C⋯H (15.8%) inter-actions, indicating that van der Waals inter-actions are the dominant forces in the crystal packing. Computational chemistry indicates that in the crystal the N-H⋯O hydrogen-bond energy is 57.5 kJ mol-1.

Charge density studies of multicentre two-electron bonding of an anion radical at non-ambient temperature and pressure

The variation of charge density of two-electron multicentre bonding (pancake bonding) between semi-quinone radicals with pressure and temperature was studied on a salt of 5,6-di-chloro-2,3-di-cyano-semi-quinone radical anion (DDQ) with 4-cyano-N-methyl-pyridinium cation (4-CN) using the Transferable Aspheric Atom Model (TAAM) refinement. The pancake-bonded radical dimers are stacked by non-bonding π-interactions. With rising pressure, the covalent character of interactions between radicals increases, and above 2.55 GPa, the electron density indicates multicentric covalent interactions throughout the stack. The experimental charge densities were verified and corroborated by periodic DFT computations. The TAAM approach has been tested and validated for atomic resolution data measured at ambient pressure; this work shows this approach can also be applied to diffraction data obtained at pressures up to several gigapascals.

Crystal structure and Hirshfeld surface analysis of 2-(2-oxo-3-phenyl-1,2,3,8a-tetra-hydro-quinoxalin-1-yl)ethyl acetate

In the title mol-ecule, C18H16N2O3, the di-hydro-quinoxaline moiety, with the exception of the N atom is essentially planar with the inner part of the methyl-propano-ate group (CH2-CH2-O) nearly perpendicular to it. In the crystal, inversion dimers formed by C-H⋯O hydrogen bonds are connected into oblique stacks by π-stacking and C-H⋯π(ring) inter-actions.

Globular Aggregates Stemming from the Self-Assembly of an Amphiphilic N-Annulated Perylene Bisimide in Aqueous Media

Herein, we describe the synthesis of highly emissive amphiphilic N-annulated PBI 1 decorated with oligo ethylene glycol (OEG) side chains. These polar side chains allow the straightforward solubility of 1 in solvents of different polarity such as water, iPrOH, dioxane, or chloroform. Compound 1 self-assembles in aqueous media by π-stacking of the aromatic units and van der Waals interactions, favored by the hydrophobic effect. The hypo- and hypsochromic effect observed in the UV-Vis spectra of 1 in water in comparison to chloroform is diagnostic of H-type aggregation. Solvent denaturation experiments allow deriving the free Gibbs energy for the self-assembly process in aqueous media and the factor m that is indicative of the influence exerted by a good solvent in the stability of the final aggregates. The ability of compound 1 to self-assemble in water yields globular aggregates that have been visualized by TEM imaging.

Precise Distance Measurements in DNA G-Quadruplex Dimers and Sandwich Complexes by Pulsed Dipolar EPR Spectroscopy

DNA G-quadruplexes show a pronounced tendency to form higher-order structures, such as π-stacked dimers and aggregates with aromatic binding partners. Reliable methods for determining the structure of these non-covalent adducts are scarce. Here, we use artificial square-planar Cu(pyridine)4 complexes, covalently incorporated into tetramolecular G-quadruplexes, as rigid spin labels for detecting dimeric structures and measuring intermolecular Cu2+ -Cu2+ distances via pulsed dipolar EPR spectroscopy. A series of G-quadruplex dimers of different spatial dimensions, formed in tail-to-tail or head-to-head stacking mode, were unambiguously distinguished. Measured distances are in full agreement with results of molecular dynamics simulations. Furthermore, intercalation of two well-known G-quadruplex binders, PIPER and telomestatin, into G-quadruplex dimers resulting in sandwich complexes was investigated, and previously unknown binding modes were discovered. Additionally, we present evidence that free G-tetrads also intercalate into dimers. Our transition metal labeling approach, combined with pulsed EPR spectroscopy, opens new possibilities for examining structures of non-covalent DNA aggregates.

Near-Infrared Phosphorescence Emission of Binuclear Mn(II) Based Metal-Organic Framework for Efficient Photoelectric Conversion

The development of metal-organic framework (MOF) based room-temperature phosphorescence (RTP) materials has raised extensive concern owing to their widespread applications in the field of anti-counterfeiting, photovoltaics, photocatalytic reactions, and bio-imaging. Herein, one new binuclear Mn(II) based 3D MOF [Mn₂(L)(BMIB)·(H₂O)] (1) (H₅L = 3,5-bis(3,5-dicarboxylphenxoy) benzoic acid, BMIB = tran-4-bis(2-methylimidazolyl)butylene) has been synthesized by a facile hydrothermal process. In 1, the protonated BMIB cations show infinite π-stacking arrangement, residing in the channels of the 3D network extended by L ligand and binuclear Mn(II) units. The orderly and uniform host-guest system at molecular level emits intense white light fluorescence and long-lived near infrared phosphorescence under ambient conditions. These photophysical processes were well-studied by density functional theory (DFT) calculations. Photoelectron measurements reveal high photoelectron response behavior and incident photon-to-current efficiency (IPCE).

Five concomitant polymorphs of a green fluorescent protein chromophore (GFPc) analogue: understanding variations in photoluminescence with π-stacking interactions

The synthetically modified green fluorescent protein chromophore analogue 3,4,5-trimethoxybenzylidene imidazolinone (1) yielded five polymorphs (I, II, III, IV, V) concomitantly irrespective of the solvent used for crystallization. The pentamorphic modification of 1 is solely due to the interplay of iso-energetic weak intermolecular interactions in molecular associations as well as the conformational flexibility offered by a C-C single bond, which connects the electron-deficient moiety imidazolinone with the electron-rich trimethoxybenzylidene group. A common structural feature observed in all the polymorphs is the formation of a `zero-dimensional' centrosymmetric dimeric unit through a short and linear C-H...O hydrogen bond engaging phenyl C-H and imidazolinone carbonyl oxygen. However, the networking of these dimeric units showed a subtle difference in all the polymorphs. The 2D isostructurality was observed between polymorphs I, II and III, while the other two polymorphs IV and V revealed only `zero-dimensional' isostructurality. The different fluorescence emissions of Form I (blue) and Forms II to V (yellow) were attributed to the differences in π-stacking interactions. It shows that one can modulate the photophysical properties of these smart materials by slightly altering their crystal structure. Such an approach will aid in developing new multi-colour organic fluorescent materials of varying crystal structures for live-cell imaging and fluorescent sensing applications.

Tuning of Molecular Electrostatic Potential Enables Efficient Charge Transport in Crystalline Azaacenes: A Computational Study

The chemical versatility of organic semiconductors provides nearly unlimited opportunities for tuning their electronic properties. However, despite decades of research, the relationship between molecular structure, molecular packing and charge mobility in these materials remains poorly understood. This reduces the search for high-mobility organic semiconductors to the inefficient trial-and-error approach. For clarifying the abovementioned relationship, investigations of the effect of small changes in the chemical structure on organic semiconductor properties are particularly important. In this study, we computationally address the impact of the substitution of C-H atom pairs by nitrogen atoms (N-substitution) on the molecular properties, molecular packing and charge mobility of crystalline oligoacenes. We observe that besides decreasing frontier molecular orbital levels, N-substitution dramatically alters molecular electrostatic potential, yielding pronounced electron-rich and electron-deficient areas. These changes in the molecular electrostatic potential strengthen face-to-face and edge-to-edge interactions in the corresponding crystals and result in the crossover from the herringbone packing motif to π-stacking. When the electron-rich and electron-deficient areas are large, sharply defined and, probably, have a certain symmetry, calculated charge mobility increases up to 3-4 cm2V-1s-1. The results obtained highlight the potential of azaacenes for application in organic electronic devices and are expected to facilitate the rational design of organic semiconductors for the steady improvement of organic electronics.

Crystal structure, Hirshfeld surface analysis, inter-action energy and DFT studies of 4-[(4-allyl-2-meth-oxy-phen-oxy)meth-yl]-1-(4-meth-oxy-phen-yl)-1H-1,2,3-triazole

In the title mol-ecule, C20H21N3O3, the allyl substituent is rotated out of the plane of its attached phenyl ring [torsion angle 100.66 (15)°]. In the crystal, C-HMthphn⋯OMthphn (Mthphn = meth-oxy-phen-yl) hydrogen bonds lead to the formation of (100) layers that are connected into a three-dimensional network by C-H⋯π(ring) inter-actions, together with π-π stacking inter-actions [centroid-to-centroid distance = 3.7318 (10) Å] between parallel phenyl rings. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H⋯H (48.7%) and H⋯C/C⋯H (23.3%) inter-actions. Computational chemistry reveals that the C-HMthphn⋯OMthphn hydrogen bond energy is 47.1 kJ mol-1. The theoretical structure, optimized by density functional theory (DFT) at the B3LYP/ 6-311 G(d,p) level, is compared with the experimentally determined mol-ecular structure. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

Crystal structure, Hirshfeld surface analysis and DFT studies of 6-bromo-3-(12-bromo-dodec-yl)-2-(4-nitro-phen-yl)-4H-imidazo[4,5-b]pyridine

The title compound, C24H30Br2N4O2, consists of a 2-(4-nitro-phen-yl)-4H-imidazo[4,5-b]pyridine entity with a 12-bromo-dodecyl substituent attached to the pyridine N atom. The middle eight-carbon portion of the side chain is planar to within 0.09 (1) Å and makes a dihedral angle of 21.9 (8)° with the mean plane of the imidazolo-pyridine moiety, giving the mol-ecule a V-shape. In the crystal, the imidazolo-pyridine units are associated through slipped π-π stacking inter-actions together with weak C-HPyr⋯ONtr and C-HBrmdc-yl⋯ONtr (Pyr = pyridine, Ntr = nitro and Brmdcyl = bromo-dodec-yl) hydrogen bonds. The 12-bromo-dodecyl chains overlap with each other between the stacks. The terminal -CH2Br group of the side chain shows disorder over two resolved sites in a 0.902 (3):0.098 (3) ratio. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H⋯H (48.1%), H⋯Br/Br⋯H (15.0%) and H⋯O/O⋯H (12.8%) inter-actions. The optimized mol-ecular structure, using density functional theory at the B3LYP/ 6-311 G(d,p) level, is compared with the experimentally determined structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

Crystal structure and Hirshfeld surface analysis of hexyl 1-hexyl-2-oxo-1,2-di-hydro-quinoline-4-carboxyl-ate

The asymmetric unit of the title compound, C22H31NO3, comprises of one mol-ecule. The mol-ecule is not planar, with the carboxyl-ate ester group inclined by 33.47 (4)° to the heterocyclic ring. Individual mol-ecules are linked by aromaticC-H⋯Ocarbon-yl hydrogen bonds into chains running parallel to [001]. Slipped π-π stacking inter-actions between quinoline moieties link these chains into layers extending parallel to (100). Hirshfeld surface analysis, two-dimensional fingerprint plots and mol-ecular electrostatic potential surfaces were used to qu-antify the inter-molecular inter-actions present in the crystal, indicating that the most important contributions for the crystal packing are from H⋯H (72%), O⋯H/H⋯O (14.5%) and C⋯H/H⋯C (5.6%) inter-actions.

Crystal structure, Hirshfeld surface analysis and inter-action energy and DFT studies of 1-(1,3-benzo-thia-zol-2-yl)-3-(2-hy-droxy-eth-yl)imidazolidin-2-one

In the title mol-ecule, C12H13N3O2S, the benzo-thia-zine moiety is slightly non-planar, with the imidazolidine portion twisted only a few degrees out of the mean plane of the former. In the crystal, a layer structure parallel to the bc plane is formed by a combination of O-HHydethy⋯NThz hydrogen bonds and weak C-HImdz⋯OImdz and C-HBnz⋯OImdz (Hydethy = hy-droxy-ethyl, Thz = thia-zole, Imdz = imidazolidine and Bnz = benzene) inter-actions, together with C-HImdz⋯π(ring) and head-to-tail slipped π-stacking [centroid-to-centroid distances = 3.6507 (7) and 3.6866 (7) Å] inter-actions between thia-zole rings. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (47.0%), H⋯O/O⋯H (16.9%), H⋯C/C⋯H (8.0%) and H⋯S/S⋯H (7.6%) inter-actions. Hydrogen bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing. Computational chemistry indicates that in the crystal, C-H⋯N and C-H⋯O hydrogen-bond energies are 68.5 (for O-HHydethy⋯NThz), 60.1 (for C-HBnz⋯OImdz) and 41.8 kJ mol-1 (for C-HImdz⋯OImdz). Density functional theory (DFT) optimized structures at the B3LYP/6-311 G(d,p) level are compared with the experimentally determined mol-ecular structure in the solid state.

Crystal structure, Hirshfeld surface analysis, inter-action energy and DFT studies of (2Z)-2-(2,4-di-chloro-benzyl-idene)-4-nonyl-3,4-di-hydro-2H-1,4-benzo-thia-zin-3-one

The title compound, C24H27Cl2NOS, contains 1,4-benzo-thia-zine and 2,4-di-chloro-phenyl-methyl-idene units in which the di-hydro-thia-zine ring adopts a screw-boat conformation. In the crystal, inter-molecular C-HBnz⋯OThz (Bnz = benzene and Thz = thia-zine) hydrogen bonds form chains of mol-ecules extending along the a-axis direction, which are connected to their inversion-related counterparts by C-HBnz⋯ClDchlphy (Dchlphy = 2,4-di-chloro-phen-yl) hydrogen bonds and C-HDchlphy⋯π (ring) inter-actions. These double chains are further linked by C-HDchlphy⋯OThz hydrogen bonds, forming stepped layers approximately parallel to (012). The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (44.7%), C⋯H/H⋯C (23.7%), Cl⋯H/H⋯Cl (18.9%), O⋯H/H⋯O (5.0%) and S⋯H/H⋯S (4.8%) inter-actions. Hydrogen-bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing. Computational chemistry indicates that in the crystal, C-HDchlphy⋯OThz, C-HBnz⋯OThz and C-HBnz⋯ClDchlphy hydrogen-bond energies are 134.3, 71.2 and 34.4 kJ mol-1, respectively. Density functional theory (DFT) optimized structures at the B3LYP/6-311 G(d,p) level are compared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap. The two carbon atoms at the end of the nonyl chain are disordered in a 0.562 (4)/0.438 (4) ratio.

Crystal structure, Hirshfeld surface analysis and DFT studies of 1-benzyl-3-[(1-benzyl-1H-1,2,3-triazol-5-yl)meth-yl]-2,3-di-hydro-1H-1,3-benzo-diazol-2-one monohydrate

In the title mol-ecule, C24H21N5O·H2O, the di-hydro-benzo-diazole moiety is not quite planar, while the whole mol-ecule adopts a U-shaped conformation in which there is a close approach of the two benzyl groups. In the crystal, chains of alternating mol-ecules and lattice water extending along [201] are formed by O-HUncoordW⋯ODhyr and O-HUncoordW⋯NTrz (UncoordW = uncoordinated water, Dhyr = di-hydro and Trz = triazole) hydrogen bonds. The chains are connected into layers parallel to (010) by C-HTrz⋯OUncoordW hydrogen bonds with the di-hydro-benzo-diazole units in adjacent layers inter-calating to form head-to-tail π-stacking [centroid-to-centroid distance = 3.5694 (11) Å] inter-actions between them, which generates the overall three-dimensional structure. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H⋯H (52.1%), H⋯C/C⋯H (23.8%) and O⋯H/H⋯O (11.2%) inter-actions. Hydrogen-bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing. Density functional theory (DFT) optimized structures at the B3LYP/ 6-311 G(d,p) level are compared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

Crystal structure, Hirshfeld surface analysis and inter-action energy and DFT studies of 1-methyl-3-(prop-2-yn-1-yl)-2,3-di-hydro-1H-1,3-benzo-diazol-2-one

In the title mol-ecule, C11H10N2O, the di-hydro-benzimidazol-2-one moiety is essentially planar, with the prop-2-yn-1-yl substituent rotated well out of this plane. In the crystal, C-HMthy⋯π(ring) inter-actions and C-HProp⋯ODhyr (Mthy = methyl, Prop = prop-2-yn-1-yl and Dhyr = di-hydro) hydrogen bonds form corrugated layers parallel to (10), which are associated through additional C-HBnz⋯ODhyr (Bnz = benzene) hydrogen bonds and head-to-tail, slipped, π-stacking [centroid-to-centroid distance = 3.7712 (7) Å] inter-actions between di-hydro-benzimidazol-2-one moieties. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯H (44.1%), H⋯C/C⋯H (33.5%) and O⋯H/H⋯O (13.4%) inter-actions. Hydrogen-bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing. Computational chemistry calculations indicate that in the crystal, C-H⋯O hydrogen-bond energies are 46.8 and 32.5 (for C-HProp⋯ODhyr) and 20.2 (for C-HBnz⋯ODhyr) kJ mol-1. Density functional theory (DFT) optimized structures at the B3LYP/6-311 G(d,p) level are compared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

Crystal structure, Hirshfeld surface analysis and inter-action energy and DFT studies of (2Z)-4-benzyl-2-(2,4-di-chloro-benzyl-idene)-2H-1,4-benzo-thia-zin-3(4H)-one

The title compound, C22H15Cl2NOS, contains 1,4-benzo-thia-zine and 2,4-di--chloro-benzyl-idene units, where the di-hydro-thia-zine ring adopts a screw-boat conformation. In the crystal, inter-molecular C-HBnz⋯OThz (Bnz = benzene and Thz = thia-zine) hydrogen bonds form corrugated chains extending along the b-axis direction which are connected into layers parallel to the bc plane by inter-molecular C-HMethy⋯SThz (Methy = methyl-ene) hydrogen bonds, en-closing R 4 4(22) ring motifs. Offset π-stacking inter-actions between 2,4-di--chloro-phenyl rings [centroid-centroid = 3.7701 (8) Å] and π-inter-actions which are associated by C-HBnz⋯π(ring) and C-HDchlphy⋯π(ring) (Dchlphy = 2,4-di-chloro-phen-yl) inter-actions may be effective in the stabilization of the crystal structure. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (29.1%), H⋯C/C⋯H (27.5%), H⋯Cl/Cl⋯H (20.6%) and O⋯H/H⋯O (7.0%) inter-actions. Hydrogen-bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing. Computational chemistry indicates that in the crystal, the C-HBnz⋯OThz and C-HMethy⋯SThz hydrogen-bond energies are 55.0 and 27.1 kJ mol-1, respectively. Density functional theory (DFT) optimized structures at the B3LYP/6-311G(d,p) level are compared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

Crystal structure, Hirshfeld surface analysis and DFT studies of ethyl 2-{4-[(2-eth-oxy-2-oxoeth-yl)(phen-yl)carbamo-yl]-2-oxo-1,2-di-hydro-quinolin-1-yl}acetate

The title com-pound, C24H24N2O6, consists of ethyl 2-(1,2,3,4-tetra-hydro-2-oxo-quinolin-1-yl)acetate and 4-[(2-eth-oxy-2-oxoeth-yl)(phen-yl)carbomoyl] units, where the oxo-quinoline unit is almost planar and the acetate substituent is nearly perpendicular to its mean plane. In the crystal, C-HOxqn⋯OEthx and C-HPh-yl⋯OCarbx (Oxqn = oxoquinolin, Ethx = eth-oxy, Phyl = phenyl and Carbx = carboxyl-ate) weak hydrogen bonds link the mol-ecules into a three-dimensional network sturucture. A π-π inter-action between the constituent rings of the oxo-quinoline unit, with a centroid-centroid distance of 3.675 (1) Å may further stabilize the structure. Both terminal ethyl groups are disordered over two sets of sites. The ratios of the refined occupanies are 0.821 (8):0.179 (8) and 0.651 (18):0.349 (18). The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (53.9%), H⋯O/O⋯H (28.5%) and H⋯C/C⋯H (11.8%) inter-actions. Weak inter-molecular hydrogen-bond inter-actions and van der Waals inter-actions are the dominant inter-actions in the crystal packing. Density functional theory (DFT) geometric optimized structures at the B3LYP/6-311G(d,p) level are com-pared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO mol-ecular orbital behaviour was elucidated to determine the energy gap.

Crystal structures of two dimeric nickel di-phenyl-acetate com-plexes

The mol­ecular and crystal structures of μ-aqua-κ²O:O-di-μ-di­phenyl­acetato-κ⁴O:O′-bis­[(di­phenyl­acetato-κO)bis­(pyridine-κN)nickel(II)] and μ-aqua-κ²O:O-di-μ-di­phenyl­acetato-κ⁴O:O′-bis­[(2,2′-bi­pyridine-κ²N,N′)(di­phenyl­acetato-κO)nickel(II)]–aceto­nitrile–di­phenyl­acetic acid (1/2.5/1) are reported. Hirshfeld surface analysis of both com­pounds have been carried out.

In the crystal structures of the title com­pounds, namely μ-aqua-κ²O:O-di-μ-di­phenyl­acetato-κ⁴O:O′-bis­[(di­phenyl­acetato-κO)bis­(pyridine-κN)nickel(II)], [Ni₂(C₁₄H₁₁O₂)₄(C₅H₅N)₄(H₂O)] (1) and μ-aqua-κ²O:O-di-μ-di­phenyl­acetato-κ⁴O:O′-bis­[(2,2′-bi­pyridine-κ²N,N′)(di­phenyl­acetato-κO)nickel(II)]–aceto­nitrile–di­phenyl­acetic acid (1/2.5/1), [Ni₂(C₁₄H₁₁O₂)₄(C₁₀H₈N₂)₂(H₂O)]·2.5CH₃CN·C₁₄H₁₂O₂ (2), the com­plex units are stabilized by a variety of intra- and inter­molecular hydrogen bonds, as well as C—H⋯π and π–π contacts between the aromatic systems of the pyridine, dipyridyl and di­phenyl­acetate ligands. Despite the fact that the di­phenyl­acetate ligand is sterically bulky, this does not inter­fere with the formation of the described aqua-bridged dimeric core, even with a 2,2′-bi­pyridine ligand, which has a strong chelating effect.

Hooking Together Sigmoidal Monomers into Supramolecular Polymers

Supramolecular polymers show great potential in the development of new materials because of their inherent recyclability and their self-healing and stimuli-responsive properties. Supramolecular conductive polymers are generally obtained by the assembly of individual aromatic molecules into columnar arrays that provide an optimal channel for electronic transport. A new approach is reported to prepare supramolecular polymers by hooking together sigmoidal monomers into 1D arrays of π-stacked anthracene and acridine units, which gives rise to micrometer-sized fibrils that show pseudoconductivities in line with other conducting materials. This approach paves the way for the design of new supramolecular polymers constituted by acene derivatives with enhanced excitonic and electronic transporting properties.

Crystal structure, Hirshfeld surface analysis and inter-action energy and DFT studies of 2-chloro-ethyl 2-oxo-1-(prop-2-yn-1-yl)-1,2-di-hydro-quinoline-4-carboxyl-ate

The title compound, C15H12ClNO3, consists of a 1,2-di-hydro-quinoline-4-carb-oxyl-ate unit with 2-chloro-ethyl and propynyl substituents, where the quinoline moiety is almost planar and the propynyl substituent is nearly perpendicular to its mean plane. In the crystal, the mol-ecules form zigzag stacks along the a-axis direction through slightly offset π-stacking inter-actions between inversion-related quinoline moieties which are tied together by inter-molecular C-HPrpn-yl⋯OCarbx and C-HChlethy⋯OCarbx (Prpnyl = propynyl, Carbx = carboxyl-ate and Chlethy = chloro-eth-yl) hydrogen bonds. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (29.9%), H⋯O/O⋯H (21.4%), H⋯C/C⋯ H (19.4%), H⋯Cl/Cl⋯H (16.3%) and C⋯C (8.6%) inter-actions. Hydrogen bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing. Computational chemistry indicates that in the crystal, the C-HPrpn-yl⋯OCarbx and C-HChlethy⋯OCarbx hydrogen bond energies are 67.1 and 61.7 kJ mol-1, respectively. Density functional theory (DFT) optimized structures at the B3LYP/ 6-311 G(d,p) level are compared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

Crystal structure, Hirshfeld surface analysis and inter-action energy and DFT studies of 4-[(prop-2-en-1-yl-oxy)meth-yl]-3,6-bis-(pyridin-2-yl)pyridazine

The title compound, C18H16N4O, consists of a 3,6-bis-(pyridin-2-yl)pyridazine moiety linked to a 4-[(prop-2-en-1-yl-oxy)meth-yl] group. The pyridine-2-yl rings are oriented at a dihedral angle of 17.34 (4)° and are rotated slightly out of the plane of the pyridazine ring. In the crystal, C-HPyrd⋯NPyrdz (Pyrd = pyridine and Pyrdz = pyridazine) hydrogen bonds and C-HPrp-oxy⋯π (Prp-oxy = prop-2-en-1-yl-oxy) inter-actions link the mol-ecules, forming deeply corrugated layers approximately parallel to the bc plane and stacked along the a-axis direction. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H⋯H (48.5%), H⋯C/C⋯H (26.0%) and H⋯N/N⋯H (17.1%) contacts, hydrogen bonding and van der Waals inter-actions being the dominant inter-actions in the crystal packing. Computational chemistry indicates that in the crystal, the C-HPyrd⋯NPyrdz hydrogen-bond energy is 64.3 kJ mol-1. Density functional theory (DFT) optimized structures at the B3LYP/6-311 G(d,p) level are compared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

Crystal structure, DFT study and Hirshfeld surface analysis of 1-nonyl-2,3-di-hydro-1H-indole-2,3-dione

In the title mol-ecule, C17H23NO2, the di-hydro-indole portion is planar (r.m.s. deviation = 0.0157 Å) and the nonyl substituent is in an 'extended' conformation. In the crystal, the nonyl chains inter-calate and the di-hydro-indole-dione units are associated through C-H⋯O hydrogen bonds to form micellar blocks. Based on the Hirshfeld surface analysis, the most important inter-molecular inter-action is the H⋯H inter-action.

Crystal structure, Hirshfeld surface analysis and inter-action energy and DFT studies of 5,5-diphenyl-1,3-bis-(prop-2-yn-1-yl)imidazolidine-2,4-dione

The title mol­ecule consists of an imidazolidine unit linked to two phenyl rings and two prop-2-yn-1-yl moieties. The imidazolidine ring is oriented at dihedral angles of 79.10 (5) and 82.61 (5)° with respect to the phenyl rings, while the dihedral angle between the two phenyl rings is 62.06 (5)°. In the crystal, C—H_Prop⋯O_Imdzln (Prop = prop-2-yn-1-yl and Imdzln = imidazolidine) hydrogen bonds link the mol­ecules into infinite chains along the b-axis direction. Two weak C—H_Phen⋯π inter­actions are also observed.

The title compound, C₂₁H₁₆N₂O₂, consists of an imidazolidine unit linked to two phenyl rings and two prop-2-yn-1-yl moieties. The imidazolidine ring is oriented at dihedral angles of 79.10 (5) and 82.61 (5)° with respect to the phenyl rings, while the dihedral angle between the two phenyl rings is 62.06 (5)°. In the crystal, inter­molecular C—H_Prop⋯O_Imdzln (Prop = prop-2-yn-1-yl and Imdzln = imidazolidine) hydrogen bonds link the mol­ecules into infinite chains along the b-axis direction. Two weak C—H_Phen⋯π inter­actions are also observed. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (43.3%), H⋯C/C⋯H (37.8%) and H⋯O/O⋯H (18.0%) inter­actions. Hydrogen bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that the C—H_Prop⋯O_Imdzln hydrogen-bond energy in the crystal is −40.7 kJ mol⁻¹. Density functional theory (DFT) optimized structures at the B3LYP/6–311G(d,p) level are compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.