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White circularly polarized organic light‐emitting diodes (CP‐WOLEDs) are central to prospective 3D displays and lighting sources. However, owing to the unwanted charge trapping effect and inefficient chirality transfer, the development of CP‐WOLEDs with a high color rendering index (CRI) and large dissymmetry factor (gEL) is challenging. Herein, a pioneering strategy of chiral co‐assembly‐sensitized circularly polarized luminescence (CCS‐CPL) is proposed for improving the performance of white circularly polarized electroluminescence (CP‐EL). Chiral co‐assembled sensitizers ((S‐/R‐Cz)0.2‐(I‐P)0.8) are smartly developed using π–π stacking interactions between the chiral binaphthyl derivatives (S‐/R‐Cz) and achiral conjugated pyrene‐based polymer (I‐P) in a molar ratio of 1:4. Using the chiral co‐assembly‐sensitized strategy on achiral aggregation‐induced emission (AIE) dyes for emitting layers (EMLs) of OLEDs, full‐color achiral AIE‐active dyes can be sensitized by chiral co‐assembly (S‐/R‐Cz)0.2‐(I‐P)0.8. The color‐tunable white CP‐EL performance can be achieved at the CIE coordinates of (0.33, 0.33) with an ultrahigh CRI of 93 and a large gEL value up to 0.071. This study thus provides a valuable guidance for CCS‐type CP‐WOLEDs. [ABSTRACT FROM AUTHOR]

Gelatin-based hydrogels with excellent mechanical properties and conductivities are desirable, but their fabrication is challenging. In this work, an innovative approach for the preparation of gelatin-based conductive hydrogels is presented that improves the mechanical and conductive properties of hydrogels by integrating Z–Gln–Gly into gelatin polymers via enzymatic crosslinking. In these hydrogels (Gel–TG–ZQG), dynamic π–π stacking interactions are created by the introduction of carbobenzoxy groups, which can increase the elasticity and toughness of the hydrogel and improve the conductivity sensitivity by forming effective electronic pathways. Moreover, the mechanical properties and conductivity of the obtained hydrogel can be controlled by tuning the molar ratio of Z–Gln–Gly to the primary amino groups in gelatin. The hydrogel with the optimal mechanical properties (Gel–TG–ZQG (0.25)) exhibits a high storage modulus, compressive strength, tensile strength, and elongation at break of 7.8 MPa at 10 °C, 0.15 MPa at 80% strain, 0.343 MPa, and 218.30%, respectively. The obtained Gel–TG–ZQG (0.25) strain sensor exhibits a short response/recovery time (260.37 ms/130.02 ms) and high sensitivity (0.138 kPa−1) in small pressure ranges (0–2.3 kPa). The Gel–TG–ZQG (0.25) hydrogel-based sensors can detect full-range human activities, such as swallowing, fist clenching, knee bending and finger pressing, with high sensitivity and stability, yielding highly reproducible and repeatable sensor responses. Additionally, the Gel–TG–ZQG hydrogels are noncytotoxic. All the results demonstrate that the Gel–TG–ZQG hydrogel has potential as a biosensor for wearable devices and health-monitoring systems. [ABSTRACT FROM AUTHOR]

In the title compound, C10H8N4O3·C3H7NO, the asymmetric unit contains two crystallographically independent molecules A and B, each of which has one DMF solvate molecule. Molecules A and B both feature intramolecular N—H...O hydrogen bonds, forming S(6) ring motifs and consolidating the molecular configuration. In the crystal, N—H...O and O—H...O hydrogen bonds connect molecules A and B, forming R22(8) ring motifs. Weak C—H...O interactions link the molecules, forming layers parallel to the (\overline{2}12) plane. The DMF solvent molecules are also connected to the main molecules (A and B) by N—H...O hydrogen bonds. π–π stacking interactions [centroid-to-centroid distance = 3.8702 (17) Å] between the layers also increase the stability of the molecular structure in the third dimension. According to the Hirshfeld surface study, O...H/H...O interactions are the most significant contributors to the crystal packing (27.5% for molecule A and 25.1% for molecule B).

Soft ionic conductors hold great potential for soft ionotronics, such as ionic skin, human–machine interface and soft luminescent device. However, most hydrogel and ionogel‐based soft ionic conductors suffer from freezing, evaporation and liquid leakage problems, which limit their use in complex environments. Herein, a class of liquid‐free ionic conductive elastomers (ICEs) is reported as an alternative soft ionic conductor in soft ionotronics. These liquid‐free ICEs offer a combination of desirable properties, including extraordinary stretchability (up to 1913%), toughness (up to 1.08 MJ cm−3), Young's modulus (up to 0.67 MPa), rapid fully self‐healing capability at room temperature, and good conductivity (up to 1.01 × 10−5 S cm−1). The application of these ICEs is demonstrated by creating a wearable sensor that can detect and discriminate minimal deformations and human body movements, such as finger or elbow joint flexion, walking, running, etc. In addition, self‐healing soft ionotronic devices are demonstrated to confront mechanical breakdown, such as an ionic skin and an alternating‐current electroluminescent device that can reuse from damage. It is believed that these liquid‐free ICEs hold great promises for applications in wearable devices and soft ionotronics. [ABSTRACT FROM AUTHOR]

Gelatin-based hydrogels with excellent mechanical properties and conductivities are desirable, but their fabrication is challenging. In this work, an innovative approach for the preparation of gelatin-based conductive hydrogels is presented that improves the mechanical and conductive properties of hydrogels by integrating Z–Gln–Gly into gelatin polymers via enzymatic crosslinking. In these hydrogels (Gel–TG–ZQG), dynamic π–π stacking interactions are created by the introduction of carbobenzoxy groups, which can increase the elasticity and toughness of the hydrogel and improve the conductivity sensitivity by forming effective electronic pathways. Moreover, the mechanical properties and conductivity of the obtained hydrogel can be controlled by tuning the molar ratio of Z–Gln–Gly to the primary amino groups in gelatin. The hydrogel with the optimal mechanical properties (Gel–TG–ZQG (0.25)) exhibits a high storage modulus, compressive strength, tensile strength, and elongation at break of 7.8 MPa at 10 °C, 0.15 MPa at 80% strain, 0.343 MPa, and 218.30%, respectively. The obtained Gel–TG–ZQG (0.25) strain sensor exhibits a short response/recovery time (260.37 ms/130.02 ms) and high sensitivity (0.138 kPa−1) in small pressure ranges (0–2.3 kPa). The Gel–TG–ZQG (0.25) hydrogel-based sensors can detect full-range human activities, such as swallowing, fist clenching, knee bending and finger pressing, with high sensitivity and stability, yielding highly reproducible and repeatable sensor responses. Additionally, the Gel–TG–ZQG hydrogels are noncytotoxic. All the results demonstrate that the Gel–TG–ZQG hydrogel has potential as a biosensor for wearable devices and health-monitoring systems.

In the title compound, C23H17N3O9S2, C—H...O hydrogen bonds link adjacent molecules in a three-dimensional network, while π–π stacking interactions, with centroid–centroid distances of 3.8745 (9) Å, between the furan and an arene ring of one of the two (3-nitrophenyl)sulfonyl groups, result in chains parallel to the a axis. The Hirshfeld surface analysis indicates that O...H/H...O (40.1%), H...H (27.5%) and C...H/H...C (12.4%) interactions are the most significant contributors to the crystal packing.

The pyridazine ring is endowed with unique physicochemical properties, characterized by weak basicity, a high dipole moment that subtends π-π stacking interactions and robust, dual hydrogen-bonding capacity that can be of importance in drug-target interactions. These properties contribute to unique applications in molecular recognition while the inherent polarity, low cytochrome P450 inhibitory effects and potential to reduce interaction of a molecule with the cardiac hERG potassium channel add additional value in drug discovery and development. The recent approvals of the gonadotropin-releasing hormone receptor antagonist relugolix (24) and the allosteric tyrosine kinase 2 inhibitor deucravacitinib (25) represent the first examples of FDA-approved drugs that incorporate a pyridazine ring. In this review, the properties of the pyridazine ring are summarized in comparison to the other azines and its potential in drug discovery is illustrated through vignettes that explore applications that take advantage of the inherent physicochemical properties as an approach to solving challenges associated with candidate optimization. [ABSTRACT FROM AUTHOR]

In the title compound, C23H17N3O9S2, C-H...O hydrogen bonds link adjacent molecules in a three-dimensional network, while π-π stacking interactions, with centroid-centroid distances of 3.8745 (9) A °, between the furan and an arene ring of one of the two (3-nitrophenyl)sulfonyl groups, result in chains parallel to the a axis. The Hirshfeld surface analysis indicates that O...H/H...O (40.1%), H...H (27.5%) and C...H/H...C (12.4%) interactions are the most significant contributors to the crystal packing. [ABSTRACT FROM AUTHOR]

Three new styrylquinoline–chalcone hybrids have been synthesized using a three‐step pathway starting with Friedländer cyclocondensation between (2‐aminophenyl)chalcones and acetone to give 2‐methyl‐4‐styrylquinolines, followed by selective oxidation to the 2‐formyl analogues, and finally Claisen–Schmidt condensation between the formyl intermediates and 1‐acetylnaphthalene. All intermediates and the final products have been fully characterized by IR and 1H/13C NMR spectroscopy, and by high‐resolution mass spectrometry, and the three products have been characterized by single‐crystal X‐ray diffraction. The molecular conformations of (E)‐3‐{4‐[(E)‐2‐phenylethenyl]quinolin‐2‐yl}‐1‐(naphthalen‐1‐yl)prop‐2‐en‐1‐one, C30H21NO, (IVa), and (E)‐3‐{4‐[(E)‐2‐(4‐fluorophenyl)ethenyl]quinolin‐2‐yl}‐1‐(naphthalen‐1‐yl)prop‐2‐en‐1‐one, C30H20FNO, (IVb), are very similar. In each compound, the molecules are linked into a three‐dimensional array by hydrogen bonds, of the C—H...O and C—H...N types in (IVa), and of the C—H...O and C—H...π types in (IVb), and by two independent π–π stacking interactions. By contrast, the conformation of the chalcone unit in (E)‐3‐{4‐[(E)‐2‐(2‐chlorophenyl)ethenyl]quinolin‐2‐yl}‐1‐(naphthalen‐1‐yl)prop‐2‐en‐1‐one, C30H20ClNO, (IVc), differs from those in (IVa) and (IVb). There are only weak hydrogen bonds in the structure of (IVc), but a single rather weak π–π stacking interaction links the molecules into chains. Comparisons are made with some related structures. [ABSTRACT FROM AUTHOR]

In the title compound, C14H8Br2FN3O2, the 4-fluorophenyl ring and the nitro-substituted phenyl ring form a dihedral angle of 64.37 (10)°. Molecules in the crystal are connected by C—H...O and C—H...F hydrogen bonds into layers parallel to (011). The crystal packing is consolidated by C—Br...π and C—F...π interactions, as well as by π–π stacking interactions. According to a Hirshfeld surface analysis of the crystal structure, the most significant contributions to the crystal packing are from O...H/H...O (15.0%), H...H (14.3%), Br...H/H...Br (14.2%), C...H/H...C (10.1%), F...H/H...F (7.9%), Br...Br (7.2%) and Br...C/C...Br (5.8%) contacts.

The title compound, C11H8N4OS, crystallizes with two independent molecules in the asymmetric unit. In the crystal, the N—H...N and C—H...N hydrogen bonds connect the molecules, generating double layers parallel to the (001) plane. The layers are joined by C—H...π interactions to form a three-dimensional supramolecular structure.

Protein kinases are key enzymes that catalyze the covalent phosphorylation of substrates via the transfer of the γ-phosphate of ATP, playing a crucial role in cellular proliferation, differentiation, and various cell regulatory processes. Due to their pivotal cellular role, the aberrant function of kinases has been associated with cancers and many other diseases. Consequently, competitive inhibition of the ATP binding site of protein kinases has emerged as an effective means of curing these diseases. Decades of intense development of protein kinase inhibitors (PKIs) resulted in 71 FDA-approved PKI drugs that target dozens of protein kinases for the treatment of various diseases. How do FDA-approved protein kinase inhibitor PKI drugs compete with ATP in their own binding pocket? This is the central question we attempt to address in this work. Based on modes of non-bonded interactions and their calculated interaction strengths by means of the advanced double hybrid DFT method B2PLYP, the molecular recognition of PKI drugs in the ATP-binding pockets was systematically analyzed. It was found that (1) all the FDA-approved PKI drugs studied here form one or more hydrogen bond(s) with the backbone amide N, O atoms in the hinge region of the ATP binding site, mimicking the adenine base; (2) all the FDA-approved PKI drugs feature two or more aromatic rings. The latter reach far and deep into the hydrophobic regions I and II, forming multiple CH-π interactions with aliphatic residues L(3), V(11), A(15), V(36), G(51), L(77) and π-π stacking interactions with aromatic residues F(47) and F(82), but ATP itself does not utilize these regions extensively; (3) all FDA-approved PKI drugs studied here have one thing in common, i.e., they frequently formed non-bonded interactions with a total of 12 residues L(3),V(11), A(15), K(17), E(24),V(36),T(45), F(47), G(51), L(77), D(81) and F(82) in the ATP binding. Many of those 12 commonly involved residues are highly conserved residues with important structural and catalytic functional roles. K(17) and E(24) are the two highly conserved residues crucial for the catalytic function of kinases. D(81) and F(82) belong to the DFG motif; T(45) was dubbed the gate keeper residue. F(47) is located on the hinge region and G(51) sits on the linker that connects the hinge to the αD-helix. It is this targeting of highly conserved residues in protein kinases that led to promiscuous PKI drugs that lack selectivity. Although the formation of hydrogen bond(s) with the backbone of the hinge gives PKI drugs the added binding affinity and the much-needed directionality, selectivity is sacrificed. That is why so many FDA-approved PKI drugs are known to have multiple targets. Moreover, off-target-mediated toxicity caused by a lack of selectivity was one of the major challenges facing the PKI drug discovery community. This work suggests a road map for future PKI drug design, i.e., targeting non-conserved residues in the ATP binding pocket to gain better selectivity so as to avoid off-target-mediated toxicity. [ABSTRACT FROM AUTHOR]

• As the fraction of rings increases, the viscosity and glass transition temperature enhance. • The PSA-VF resin has a weaker diffusion ability compared to the PSA-V and PSNP-V resins. • The PSA-V resin exhibits a relatively discrete structure, whereas the PSNP-V and PSA-VF resins display an ordered structural stacking. • The interactions between the resins are typical π-π stacking interactions. Silicon-containing arylacetylene (PSA) resins are promising high-temperature resistant polymers. But their structure–property relationships at the atomic level are still unknown. In this study, the effects of π-π interactions on the rheological and heat-resistant behaviors of silicon-containing arylacetylene resins containing benzene unit (PSA-V), 2,7-diethynylnaphthalene unit (PSNP-V), and 2,7-diethynyl-9H-fluorene unit (PSA-VF) in main chains were explored using molecular dynamics. Compared to the PSA resin, the PSA-VF resin has stronger π-π stacking interactions, confirmed by interaction region indicator and energy decomposition analysis methods. When the resin has a higher fraction of aromatic ring, the mobility of the molecules decreases and so the diffusion capacity will be reduced. After analyzing the simulated trajectories for different resin systems, the face-to-face stacking between the resins was found. Compared with the PSA-V resin with relatively dispersed aggregate structure, the PSA-VF resin with larger-sized and more regular aggregate structure has higher viscosity and glass transition temperature due to stronger π-π interactions. These results provide a new perspective on the relationship between the π-π interactions and properties of the PSA resins. [ABSTRACT FROM AUTHOR]

Coiled carbon nanotube (CCNT) as a novel nanomaterial has the potential to enhance the thermomechanical properties of asphalt. In this study, three typical coiled carbon nanotubes are constructed to modify asphalt, and the thermomechanical properties of asphalt nanocomposites are investigated through molecular dynamics simulations. The results show that the structural deformations of CCNTs occur in the front loops during the pullout process and the initial shapes of CCNTs can be restored after the complete pullout. The anchoring effect is found to improve the shear resistance owing to the rotational structures of CCNTs. The asphalt molecules can attach to the rotational surfaces of CCNTs through the π-π stacking interactions during the pullout process, and saturate molecules can flexibly move into the space between different loops of the deformed CCNTs. CCNT3 nanocomposite has the highest shear capacity at all temperature ranges, and CCNT2 nanocomposite is more temperature susceptible than other nanocomposites. The existence of CCNTs can greatly restrict the mobility of asphalt molecules, and the effect of CCNTs on the deformation resistance at high temperature ranges is more effective than that of the low temperature ranges. The molecular interactions and reinforcing mechanisms between various CCNTs and asphalt components can be elucidated, promoting CCNTs as a new form of asphalt reinforcement and enhancing the long-term durability of asphalt pavement. [Display omitted] • Structural deformation occurs on the front loops of CCNTs during the pullout process. • The anchoring effect can be generated owing to the rotational structures of CCNTs. • Asphalt molecules can attach to the rotational surfaces of the CCNTs by the π-π stacking interactions. • CCNTs can greatly impede the mobility of asphalt molecules. • The shear resistance of asphalt nanocomposite decreases with the increasing temperature ranges. [ABSTRACT FROM AUTHOR]

In the title compound, C16H12F5N3O, the dihedral angle between the aromatic rings is 31.84 (8)°. In the crystal, the molecules are linked into dimers possessing crystallographic twofold symmetry by pairwise N—H...O hydrogen bonds and weak C—H...O hydrogen bonds and aromatic π–π stacking interactions link the dimers into a three-dimensional network. A Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from F...H/H...F (41.1%), H...H (21.8%), C...H/H...C (9.7%) C...C (7.1%) and O...H/H...O (7.1%) contacts. The contribution of some disordered solvent to the scattering was removed using the SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9–18] in PLATON. The solvent contribution was not included in the reported molecular weight and density.

Poly(glycerol sebacate) (PGS), a soft, tough elastomer with excellent biocompatibility, has been exploited successfully in many tissue engineering applications. Although tunable to some extent, the rapid in vivo degradation kinetics of PGS is not compatible with the healing rate of some tissues. The incorporation of L-glutamic acid into a PGS network with an aim to retard the degradation rate of PGS through the formation of peptide bonds was conducted in this study. A series of poly(glycerol sebacate glutamate) (PGSE) containing various molar ratios of sebacic acid/L-glutamic acid were synthesized. Two kinds of amino-protected glutamic acids, Boc-L-glutamic acid and Z-L-glutamic acid were used to prepare controls that consist of no peptide bonds, denoted as PGSE-B and PGSE-Z, respectively. The prepolymers were characterized using 1H-NMR spectroscopy. Cured elastomers were characterized using FT-IR, DSC, TGA, mechanical testing, and contact angle measurement. In vitro enzymatic degradation of PGSE over a period of 28 days was investigated. FT-IR spectroscopy confirmed the formation of peptide bonds. The glass transition temperature for the elastomer was found to increase as the ratio of sebacic acid/glutamic acid was increased to four. The decomposition temperature of the elastomer decreased as the amount of glutamic acid was increased. PGSE exhibited less stiffness and larger elongation at break as the ratio of sebacic acid/glutamic acid was decreased. Notably, PGSE-Z was stiffer and had smaller elongation at break than PGSE and PGSE-B at the same molar ratio of monomers. The results of in vitro enzymatic degradation demonstrated that PGSE has a lower degradation rate than does PGS, whereas PGSE-B and PGSE-Z degrade at a greater rate than does PGS. SEM images suggest that the degradation of these crosslinked elastomers is due to surface erosion. The cytocompatibility of PGSE was considered acceptable although slightly lower than that of PGS. The altered mechanical properties and retarded degradation kinetics for PGSE reflect the influence of peptide bonds formed by the introduction of L-glutamic acid. PGSE displaying a lower degradation rate compared to that for PGS can be used as a scaffold material for the repair or regeneration of tissues that are featured by a low healing rate. [ABSTRACT FROM AUTHOR]

In the title compound, C14H8Br2FN3O2, the 4-fluorophenyl ring and the nitro-substituted phenyl ring form a dihedral angle of 64.37 (10)°. Molecules in the crystal are connected by C--H⋯O and C--H⋯F hydrogen bonds into layers parallel to (011). The crystal packing is consolidated by C--Br⋯π and C--F⋯π interactions, as well as by n-n stacking interactions. According to a Hirshfeld surface analysis of the crystal structure, the most significant contributions to the crystal packing are from O⋯H/H⋯O (15.0%), H⋯H (14.3%), Br⋯H/H⋯Br (14.2%), C⋯H/H⋯C (10.1%), F⋯H/H⋯F (7.9%), Br⋯Br (7.2%) and Br⋯C/C⋯Br (5.8%) contacts. [ABSTRACT FROM AUTHOR]

The title compound, C19H13N, which crystallizes in the monoclinic C2/c space group with one half-molecule in the asymmetric unit, was synthesized by Suzuki–Miyaura cross-coupling reaction of 9-bromoanthracene with pyridin-4-ylboronic acid and purified by column chromatography on silica gel. Light-yellow crystals of 4-(anthracen-9-yl)-pyridine suitable for X-ray diffraction were collected by the solvent evaporation method. In the crystal, pairs of molecules are connected by intermolecular C—H...π (pyridine) interactions [d(H7...Cg) = 2.7391 (2) Å], forming cyclic centrosymmetric dimers, further resulting in an infinite one-dimensional linear chain along the c-axis direction. Weak face-to-face π–π stacking interactions [d(Cg...Cg) = 3.6061 (2) Å] link neighboring lamellar networks into the supramolecular structure.

Enzymatic hydrolysis prior to protein fibrillation was an effective way to facilitate the formation of nanofibrils. This study aimed to investigate the effects of molecular weights of hydrolysate on the kinetics, structures, and interactions of soy protein isolate (SPI) hydrolysate nanofibrils. The results showed that hydrolysate with molecular weight > 10 kDa showed a distinct fibrillation kinetics curve and a higher apparent rate constant (27.72) during fibrillation, indicating their vital role in determining the fibrillation. Hydrolysate with molecular weight > 10 kDa could form nanofibrils with higher radius gyration (17.11 ± 0.77 Å) due to stronger hydrophobic interaction, showing a stronger fibrillation ability. Hydrolysate with molecular weight within 5–10 kDa exhibited enhanced π-π stacking interactions during fibrillation, thereby promoting the extension of nanofibrils, and contributing to the formation of more nanofibrils. Hydrolysate with molecular weight < 5 kDa tended to randomly aggregate during fibrillation, resulting in a significant loss of cross-β structures in nanofibrils. Therefore, hydrolysate with different molecular weights exhibited synergistic effects during fibrillation. • Hydrolysate with molecular weight > 10 kDa determined the fibrillation rate. • Hydrolysate with molecular weight within 5–10 kDa promoted nanofibril formation. • Hydrolysate with molecular weight < 5 kDa tended to random aggregate. • Molecular weight affected hydrophobic interaction and π-π interaction of fibrillation. [ABSTRACT FROM AUTHOR]

In the title compound, C17H14Cl2N4, the dihedral angle between the aromatic rings is 50.09 (9). The central –N=N– unit shows an E configuration. In the crystal, C—H...N interactions, C—Cl...π and π-π stacking interactions [centroid-to-centroid distance = 3.7719 (14) A˚ ] link the molecules, forming molecular layers approximately parallel to the (002) plane. Additional weak van der Waals interactions between the layers consolidate the three-dimensional packing. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H...H (33.6%), N...H/ H...N (17.2%), Cl...H/H...Cl (14.1%) and C...H/H...C (14.1%) contacts. [ABSTRACT FROM AUTHOR]

In the crystal of the title compound, C7H5FN4S, the molecules are non-planar, with dihedral angle formed by least-squares planes of tetrazole and benzene rings of 59.94 (8) °. The crystal packing is formed by N—H...S hydrogen bonds, which link the molecules into centrosymmetric dimers with an R22(8) ring motif, and by the offset face-to-face π–π stacking interactions between the benzene rings, which join the dimers into layers parallel to (100). The Hirshfeld surface analysis shows that the most important contributions to the surface contacts are from N...H/H...N (21.9%), S...H/H...S (21.1%), H...H (14.6%), F...H/H...F (11.8%) and C...H/H...C (9.5%) interactions.

In the title compound, C29H22N4O3, the carbazole system forms a dihedral angle of 68.45 (3)° with the mean plane of the bipyridine ring system. The bipyridine ring system, with two methoxy substituents, is approximately planar (r.m.s. deviation = 0.0670 Å), with a dihedral angle of 7.91 (13)° between the planes of the two pyridine rings. Intramolecular C—H...O/N hydrogen bonds may promote the planarity of the bipyridyl ring system. In the pyridyl-substituted carbazole fragment, the pyridine ring is tilted by 56.65 (4)° with respect to the mean plane of the carbazole system (r.m.s. deviation = 0.0191 Å). In the crystal, adjacent molecules are connected via C—H...O/N hydrogen bonds and C—H...π interactions, resulting in the formation of a three-dimensional (3D) supramolecular network. In addition, the 3D structure contains intermolecular π–π stacking interactions, with centroid–centroid distances of 3.5634 (12) Å between pyridine rings. The title compound exhibits a high energy gap (3.48 eV) and triplet energy (2.64 eV), indicating that it could be a suitable host material in organic light-emitting diode (OLED) applications.

Protein kinases are key enzymes that catalyze the covalent phosphorylation of substrates via the transfer of the γ-phosphate of ATP, playing a crucial role in cellular proliferation, differentiation, and various cell regulatory processes. Due to their pivotal cellular role, the aberrant function of kinases has been associated with cancers and many other diseases. Consequently, competitive inhibition of the ATP binding site of protein kinases has emerged as an effective means of curing these diseases. Decades of intense development of protein kinase inhibitors (PKIs) resulted in 71 FDA-approved PKI drugs that target dozens of protein kinases for the treatment of various diseases. How do FDA-approved protein kinase inhibitor PKI drugs compete with ATP in their own binding pocket? This is the central question we attempt to address in this work. Based on modes of non-bonded interactions and their calculated interaction strengths by means of the advanced double hybrid DFT method B2PLYP, the molecular recognition of PKI drugs in the ATP-binding pockets was systematically analyzed. It was found that (1) all the FDA-approved PKI drugs studied here form one or more hydrogen bond(s) with the backbone amide N, O atoms in the hinge region of the ATP binding site, mimicking the adenine base; (2) all the FDA-approved PKI drugs feature two or more aromatic rings. The latter reach far and deep into the hydrophobic regions I and II, forming multiple CH-π interactions with aliphatic residues L(3), V(11), A(15), V(36), G(51), L(77) and π-π stacking interactions with aromatic residues F(47) and F(82), but ATP itself does not utilize these regions extensively; (3) all FDA-approved PKI drugs studied here have one thing in common, i.e., they frequently formed non-bonded interactions with a total of 12 residues L(3),V(11), A(15), K(17), E(24),V(36),T(45), F(47), G(51), L(77), D(81) and F(82) in the ATP binding. Many of those 12 commonly involved residues are highly conserved residues with important structural and catalytic functional roles. K(17) and E(24) are the two highly conserved residues crucial for the catalytic function of kinases. D(81) and F(82) belong to the DFG motif; T(45) was dubbed the gate keeper residue. F(47) is located on the hinge region and G(51) sits on the linker that connects the hinge to the αD-helix. It is this targeting of highly conserved residues in protein kinases that led to promiscuous PKI drugs that lack selectivity. Although the formation of hydrogen bond(s) with the backbone of the hinge gives PKI drugs the added binding affinity and the much-needed directionality, selectivity is sacrificed. That is why so many FDA-approved PKI drugs are known to have multiple targets. Moreover, off-target-mediated toxicity caused by a lack of selectivity was one of the major challenges facing the PKI drug discovery community. This work suggests a road map for future PKI drug design, i.e., targeting non-conserved residues in the ATP binding pocket to gain better selectivity so as to avoid off-target-mediated toxicity.

Two bis-carbamoylmethylphosphine oxide compounds, namely {[(3-{[2-(diphenylphosphinoyl)ethanamido]methyl}benzyl)carbamoyl]methyl}diphenylphosphine oxide, C36H34N2O4P2, (I), and diethyl [({2-[2-(diethoxyphosphinoyl)ethanamido]ethyl}carbamoyl)methyl]phosphonate, C14H30N2O8P2, (II), were synthesized via nucleophilic acyl substitution reactions between an ester and a primary amine. Hydrogen-bonding interactions are present in both crystals, but these interactions are intramolecular in the case of compound (I) and intermolecular in compound (II). Intramolecular π–π stacking interactions are also present in the crystal of compound (I) with a centroid–centroid distance of 3.9479 (12) Å and a dihedral angle of 9.56 (12)°. Intermolecular C—H...π interactions [C...centroid distance of 3.622 (2) Å, C—H...centroid angle of 146°] give rise to supramolecular sheets that lie in the ab plane. Key geometric features for compound (I) involve a nearly planar, trans-amide group with a C—N—C—C torsion angle of 169.12 (17)°, and a torsion angle of −108.39 (15)° between the phosphine oxide phosphorus atom and the amide nitrogen atom. For compound (II), the electron density corresponding to the phosphoryl group was disordered, and was modeled as two parts with a 0.7387 (19):0.2613 (19) occupancy ratio. Compound (II) also boasts a trans-amide group that approaches planarity with a C—N—C—C torsion angle of −176.50 (16)°. The hydrogen bonds in this structure are intermolecular, with a D...A distance of 2.883 (2) Å and a D—H...A angle of 175.0 (18)° between the amide hydrogen atom and the P=O oxygen atom. These non-covalent interactions create ribbons that run along the b-axis direction.

Poly(glycerol sebacate) (PGS), a soft, tough elastomer with excellent biocompatibility, has been exploited successfully in many tissue engineering applications. Although tunable to some extent, the rapid in vivo degradation kinetics of PGS is not compatible with the healing rate of some tissues. The incorporation of L-glutamic acid into a PGS network with an aim to retard the degradation rate of PGS through the formation of peptide bonds was conducted in this study. A series of poly(glycerol sebacate glutamate) (PGSE) containing various molar ratios of sebacic acid/L-glutamic acid were synthesized. Two kinds of amino-protected glutamic acids, Boc-L-glutamic acid and Z-L-glutamic acid were used to prepare controls that consist of no peptide bonds, denoted as PGSE-B and PGSE-Z, respectively. The prepolymers were characterized using 1H-NMR spectroscopy. Cured elastomers were characterized using FT-IR, DSC, TGA, mechanical testing, and contact angle measurement. In vitro enzymatic degradation of PGSE over a period of 28 days was investigated. FT-IR spectroscopy confirmed the formation of peptide bonds. The glass transition temperature for the elastomer was found to increase as the ratio of sebacic acid/glutamic acid was increased to four. The decomposition temperature of the elastomer decreased as the amount of glutamic acid was increased. PGSE exhibited less stiffness and larger elongation at break as the ratio of sebacic acid/glutamic acid was decreased. Notably, PGSE-Z was stiffer and had smaller elongation at break than PGSE and PGSE-B at the same molar ratio of monomers. The results of in vitro enzymatic degradation demonstrated that PGSE has a lower degradation rate than does PGS, whereas PGSE-B and PGSE-Z degrade at a greater rate than does PGS. SEM images suggest that the degradation of these crosslinked elastomers is due to surface erosion. The cytocompatibility of PGSE was considered acceptable although slightly lower than that of PGS. The altered mechanical properties and retarded degradation kinetics for PGSE reflect the influence of peptide bonds formed by the introduction of L-glutamic acid. PGSE displaying a lower degradation rate compared to that for PGS can be used as a scaffold material for the repair or regeneration of tissues that are featured by a low healing rate.

The title compound, C32H26F4N2O, crystallizes in the monoclinic space group P21/n with four molecules in the unit cell. The compound was prepared by the NaBH4 reduction of 4,8,9,10-tetrakis(4-fluorophenyl)-1,3-diazaadamantan-6-one in chloroform and ethanol as solvent. The piperidine rings exhibit chair and boat conformations, and all four fluorophenyl groups are oriented in the equatorial direction. The crystal structure features C—H...F hydrogen bonds, C—H...π, N—H...π and π–π interactions. Hirshfeld surface and two-dimensional fingerprint analysis show that van der Waals interactions constitute a major contribution to the intermolecular interactions, with H...H contacts accounting for 37.9% of the surface.

Semirigid organic ligands can adopt different conformations to construct coordination polymers with more diverse structures when compared to those constructed from rigid ligands. A new asymmetric semirigid organic ligand, 4‐{2‐[(pyridin‐3‐yl)methyl]‐2H‐tetrazol‐5‐yl}pyridine (L), has been prepared and used to synthesize three bimetallic macrocyclic complexes and one coordination polymer, namely, bis(μ‐4‐{2‐[(pyridin‐3‐yl)methyl]‐2H‐tetrazol‐5‐yl}pyridine)bis[dichloridozinc(II)] dichloromethane disolvate, [Zn2Cl4(C12H10N6)2]·2CH2Cl2, (I), the analogous chloroform monosolvate, [Zn2Cl4(C12H10N6)2]·CHCl3, (II), bis(μ‐4‐{2‐[(pyridin‐3‐yl)methyl]‐2H‐tetrazol‐5‐yl}pyridine)bis[diiodidozinc(II)] dichloromethane disolvate, [Zn2I4(C12H10N6)2]·2CH2Cl2, (III), and catena‐poly[[[diiodidozinc(II)]‐μ‐4‐{2‐[(pyridin‐3‐yl)methyl]‐2H‐tetrazol‐5‐yl}pyridine] chloroform monosolvate], {[ZnI2(C12H10N6)]·CHCl3}n, (IV), by solution reaction with ZnX2 (X = Cl and I) in a CH2Cl2/CH3OH or CHCl3/CH3OH mixed solvent system at room temperature. Complex (I) is isomorphic with complex (III) and has a bimetallic ring possessing similar coordination environments for both of the ZnII cations. Although complex (II) also contains a bimetallic ring, the two ZnII cations have different coordination environments. Under the influence of the I− anion and guest CHCl3 molecule, complex (IV) displays a significantly different structure with respect to complexes (I)–(III). C—H...Cl and C—H...N hydrogen bonds, and π–π stacking or C—Cl...π interactions exist in complexes (I)–(IV), and these weak interactions play an important role in the three‐dimensional structures of (I)–(IV) in the solid state. In addition, the fluorescence properties of L and complexes (I)–(IV) were investigated. [ABSTRACT FROM AUTHOR]

The title compound, C17H10BrCl2NO2, crystallizes in the monoclinic space group C2/c with a large cell volume of 6207 (3) Å3. The asymmetric unit of the title compound investigated at 120 K contains two crystallographically independent molecules (Z′ = 2). Each molecule demonstrates slight non-planarity in the solid state and a Z-configuration for the exocyclic C=C bond. The crystal packing reveals the presence of π-π stacking interactions between the substituted benzene rings [centroid–centroid distances of 3.836 (5) Å, shift distances in the range 1.272–1.843 Å].

In the title compound, [Cd(C16H16O3)2(C12H8N2)]·4H2O, the Cd ion lies on a twofold rotation axis and is chelated by two monodeprotonated residues of the l-tyrosine-derived ligand (S)-2-[(2-hydroxybenzyl)amino]-3-(4-hydroxyphenyl)propanoic acid (L) in a κ2N,O amino acid chelating mode, exhibiting an (N,N′)-trans disposition, and by 1,10-phenanthroline in a κ2N,N′ mode. The latter ligand is also located about the twofold rotation axis that bisects the central six-members ring. The phenolic groups remain protonated and non-coordinating and take part as acceptors in the intramolecular hydrogen bonds with the amino groups of the acido ligands. The Cd ion is six-coordinated in a distorted octahedral environment. In the crystal, O—H...O hydrogen bonds result in the formation of three-dimensional network structures. The title complex has also been characterized by IR and 1H NMR spectroscopy and DFT studies. The crystal studied was refined as an inversion twin.

The title compound, C12H6N4, crystallizes with four independent molecules (A, B, C and D) in the asymmetric unit. The dihedral angles between the two pyridine rings in each molecule are 25.25 (8)° in A, 5.51 (9)° in B, 11.11 (9)° in C and 16.24 (8)° in D. In the crystal, molecules A and B are linked by C—H...N hydrogen bonds to form layers extending parallel to the ab plane, while molecules C and D are linked by C—H...N hydrogen bonds forming –C–D–C–D– chains propagating along the b-axis direction. The layers and the chains are stacked alternately along the c axis through offset π–π and C[triple-bond]N...π [N-to-pyridine-centroid distance = 3.882 (2) Å] interactions, resulting in the formation of a supramolecular framework.

In the title compound, C16H9FO4, (I), the benzene ring is oriented at an acute angle of 59.03 (15)° relative to the coumarin plane (r.m.s deviation = 0.009 Å). This conformation of (I) is stabilized by an intramolecular C—H...O hydrogen bond, which closes a five-membering ring. In the crystal, molecules of (I) form infinite zigzag chains along the b-axis direction, linked by C—H...O hydrogen bonds. Furthermore, the crystal structure is supported by π–π stacking interactions between neighbouring pyrone and benzene or coumarin rings [centroid–centroid distances in the range 3.5758 (18)–3.6115 (16) Å], as well as C=O...π interactions [O...centroid distances in the range 3.266 (3)–3.567 (3) Å]. The theoretical data for (I) obtained from quantum chemical calculations are in good agreement with the observed structure, although the calculated C—O—C—C torsion angle between the coumarin fragment and the benzene ring (73.7°) is somewhat larger than the experimental value [63.4 (4)°]. Hirshfeld surface analysis has been used to confirm and quantify the supramolecular interactions.

The title compound, [Cu2(C9H7O4)4(C3H7NO)2]·2C3H7NO, crystallizes in the monoclinic P21/c space group, with the binuclear copper unit occupying a special position on an inversion center, i.e. the asymmetric unit of the crystal consists of one CuII ion, two 2-(methoxycarbonyl)benzoate ligands, and two DMF molecules (one coordinated and one solvate). The binuclear complex displays a paddle-wheel-shaped structure with the two copper atoms being in a Jahn–Teller-distorted octahedral coordination environment. Each 2-(methoxycarbonyl)benzoate substituent acts as a bridging ligand and links two Cu atoms with a Cu—Cu distance of 2.633 (1) Å. The carboxylate groups of the 2-(methoxycarbonyl)benzoate ligands adopt bidentate syn–syn bridging modes, with dihedral angles between the carboxylate planes and the aromatic rings of 18.427 (4) and 43.029 (6)°. In the crystal, adjacent DMF molecules coordinated to copper atoms are arranged in a mutual `head-to-tail' manner by offset face-to-face π–π stacking interactions, resulting in chains along the c-axis direction. The planes of the coordinated DMF molecules are parallel to each other, the distance between them being 3.33 (1) Å. A three-dimensional structure is assembled from the chains by weak C—H...O and C—H...π intermolecular interactions involving the DMF solvent molecules. One of the methyl ester groups is disordered over two sites with an occupancy ratio of 0.751 (12):0.249 (12).

In the title com­pound, C29H22N4O3, the carbazole system forms a dihedral angle of 68.45 (3)° with the mean plane of the bi­pyridine ring system. The bi­pyridine ring system, with two meth­oxy substituents, is approximately planar (r.m.s. deviation = 0.0670 Å), with a dihedral angle of 7.91 (13)° between the planes of the two pyridine rings. Intra­molecular C—H∙∙∙O/N hydrogen bonds may promote the planarity of the bipyridyl ring system. In the pyridyl-substituted carbazole fragment, the pyridine ring is tilted by 56.65 (4)° with respect to the mean plane of the carbazole system (r.m.s. deviation = 0.0191 Å). In the crystal, adjacent mol­ecules are connected via C—H∙∙∙O/N hydrogen bonds and C—H∙∙∙π inter­actions, resulting in the formation of a three-dimensional (3D) supra­molecular network. In addition, the 3D structure contains inter­molecular π–π stacking inter­actions, with centroid–centroid distances of 3.5634 (12) Å between pyridine rings. The title com­pound exhibits a high energy gap (3.48 eV) and triplet energy (2.64 eV), indicating that it could be a suitable host material in organic light-emitting diode (OLED) applications. [ABSTRACT FROM AUTHOR]

Highly cis-1,4 selective (up to 98%) coordination–insertion polymerization of 1,3-butadiene (BD) has been achieved herein using acenaphthene-based α-diimine cobalt complexes. Due to the presence of intra-ligand π-π stacking interactions, the complexes revealed high thermostability, affording polybutadiene products in high yields. Moreover, all of the obtained polymers possessed a relatively narrow molecular weight distribution as well as high molecular weight (up to 92.2 × 104 Dalton). The molecular weights of the resultant polybutadienes could be finely tuned by varying polymerization parameters, including temperature, Al/Co ratio, etc. Moreover, the copolymerization of butadiene with polar monomer 2-(4-methoxyphenyl)-1,3-butadiene (2-MOPB) was also successfully realized to produce a type of polar cis-1,4 polybutadiene (cis-1,4 content: up to 98.1%) with a range of 2-MOPB content (0.46–1.83%). Water contact angle measurements indicated that the insertion of a polar monomer into a polymer chain could significantly improve the polymer’s surface property.

Protein kinases are key enzymes in many signal transduction pathways, and play a crucial role in cellular proliferation, differentiation, and various cell regulatory processes. However, aberrant function of kinases has been associated with cancers and many other diseases. Consequently, competitive inhibition of the ATP binding site of protein kinases has emerged as an effective means of curing these diseases. Over the past three decades, thousands of protein kinase inhibitors (PKIs) with varying molecular frames have been developed. Large-scale data mining of the Protein Data Bank resulted in a database of 2139 non-redundant high-resolution X-ray crystal structures of PKIs bound to protein kinases. This provided us with a unique opportunity to study molecular determinants for the molecular recognition of PKIs. A chemoinformatic analysis of 2139 PKIs resulted in findings that PKIs are “flat” molecules with high aromatic ring counts and low fractions of sp3 carbon. All but one PKI possessed one or more aromatic rings. More importantly, it was found that the average weighted hydrogen bond count is inversely proportional to the number of aromatic rings. Based on this linear relationship, we put forward the exchange rule of hydrogen bonding interactions and non-bonded π-interactions. Specifically, a loss of binding affinity caused by a decrease in hydrogen bonding interactions is compensated by a gain in binding affinity acquired by an increase in aromatic ring-originated non-bonded interactions (i.e., π–π stacking interactions, CH–π interactions, cation–π interactions, etc.), and vice versa. The very existence of this inverse relationship strongly suggests that both hydrogen bonding and aromatic ring-originated non-bonded interactions are responsible for the molecular recognition of PKIs. As an illustration, two representative PKI–kinase complexes were employed to examine the relative importance of different modes of non-bonded interactions for the molecular recognition of PKIs. For this purpose, two FDA-approved PKI drugs, ibrutinib and lenvatinib, were chosen. The binding pockets of both PKIs were thoroughly examined to identify all non-bonded intermolecular interactions. Subsequently, the strengths of interaction energies between ibrutinib and its interacting residues in tyrosine kinase BTK were quantified by means of the double hybrid DFT method B2PLYP. The resulting energetics for the binding of ibrutinib in tyrosine kinase BTK showed that CH–π interactions and π–π stacking interactions between aromatic rings of the drug and hydrophobic residues in its binding pocket dominate the binding interactions. Thus, this work establishes that, in addition to hydrogen bonding, aromatic rings function as important molecular determinants for the molecular recognition of PKIs. In conclusion, our findings support the following pharmacophore model for ATP-competitive kinase inhibitors: a small molecule features a scaffold of one or more aromatic rings which is linked with one or more hydrophilic functional groups. The former has the structural role of acting as a scaffold and the functional role of participating in aromatic ring-originated non-bonded interactions with multiple hydrophobic regions in the ATP binding pocket of kinases. The latter ensure water solubility and form hydrogen bonds with the hinge region and other hydrophilic residues of the ATP binding pocket.

The title compound, C32H26F4N2O, crystallizes in the monoclinic space group P21/n with four mol­ecules in the unit cell. The compound was prepared by the NaBH4 reduction of 4,8,9,10-tetra­kis­(4-fluoro­phen­yl)-1,3-di­aza­adamantan-6-one in chloro­form and ethanol as solvent. The piperidine rings exhibit chair and boat conformations, and all four fluoro­phenyl groups are oriented in the equatorial direction. The crystal structure features C—H. . .F hydrogen bonds, C—H. . .π, N—H. . .π and π–π inter­actions. Hirshfeld surface and two-dimensional fingerprint analysis show that van der Waals inter­actions constitute a major contribution to the inter­molecular inter­actions, with H. . .H contacts accounting for 37.9% of the surface. [ABSTRACT FROM AUTHOR]

The synthesis, structural characterization and influence of solvents on the crystal packing of solvated complexes of ethacridine with phthalic acid: 6,9-diamino-2-ethoxyacridinium phthalate methanol solvate (1), 6,9-diamino-2-ethoxyacridinium phthalate ethanol solvate (2), 6,9-diamino-2-ethoxyacridinium phthalate isobutanol solvate (3), and 6,9-diamino-2-ethoxyacridinium phthalate tert-butanol solvate monohydrate (4) are described in this article. Single-crystal XRD measurements revealed that the compounds 1–4 crystallized in the triclinic P-1 space group, and the 6,9-diamino-2-ethoxyacridinium cations, phthalic acid anions and solvent molecules interact via strong N–H···O, O–H···O, C–H···O hydrogen bonds, and C–H···π and π–π interactions to form different types of basic structural motifs, such as: heterotetramer bis[···cation···anion···] in compound 1 and 2, heterohexamer bis[···cation···alcohol···anion···] in compound 3, and heterohexamer bis[···cation···water···anion···] in compound 4. Presence of solvents molecule(s) in the crystals causes different supramolecular synthons to be obtained and thus has an influence on the crystal packing of the compounds analyzed.

[Display omitted] • Hardwood lignin-based resins with different mechanical properties were prepared. • The lignin fractions were highly functionalized by using diallyl carbonate. • The 50% of the thiol conversion was reached in less than 3 h (except for one fraction). • Sandwich and T-shaped π-π stacking interactions were identified in all lignin samples. A series of different technical hardwood lignin-based resins have been successfully synthesized, characterized, and utilised to produce thiol-ene thermoset polymers. Firstly, technical lignin was fractionated and allylated, whereafter it was crosslinked with a trifunctional thiol. Structural and morphological characteristics of the lignin fractions were studied by 1H NMR, 31P NMR, SEC, FTIR, DSC, TGA, and WAXS. The hardwood lignin fractions have a high content of C 5 -substituted OH groups. The WAXS studies on lignin fractions revealed the presence of two π-π stacking conformations, sandwiched (4.08–4.25 Å) and T-shaped (6.52–6.91 Å). The presence of lignin superstructures with distances/sizes between 10.5 and 12.8 Å was also identified. The curing reaction of the thermosets was investigated by RT-FTIR. Almost all thermosets (excepting one fraction) reached 95% of the thiol conversion in less than 17 h, revealing the enhanced reactivity of the allylated hardwood lignin samples. The mechanical properties of the thermosets were investigated by DMA. The curing performance, as well as the final thermoset properties, have been correlated to variations in chemical composition and morphological differences of lignin fractions. The described results clearly demonstrate that technical hardwood lignins can be utilized for these applications, but also that significant differences compared to softwood lignins have to be considered for material design. [ABSTRACT FROM AUTHOR]

The title compound, C10H8N2O2·H2O, consists of an N-hydroxyquinoline-2-carboxamide molecule in the keto tautomeric form and a water molecule connected through an O—H...O hydrogen bond. The N-hydroxyquinoline-2-carboxamide molecule has a nearly planar structure [maximum deviation = 0.062 (1) Å] and only the hydroxy H atom deviates significantly from the molecule plane. In the crystal, π–π stacking between the aromatic rings [intercentroid distance = 3.887 (1) Å] and intermolecular O—H...O hydrogen bonds organize the crystal components into columns extending along the b-axis direction.

In order to determine the influence of halogen substituent on the self-assembly of the 6,9-diamino-2-ethoxyacridinium cations and 3-halobenzoate anions in the crystals formed from ethacridine and halobenzoic acids, the series of ethacridinium meta-halobenzoates dihydrates: ethacridinium 3-chlorobenzoate dihydrate (1), ethacridinium 3-bromobenzoate dihydrate (2), and ethacridinium 3-iodobenzoate dihydrate (3), were synthesized and structurally characterized. Single-crystal X-ray diffraction measurements showed that the title compounds crystallized in the monoclinic P21/c space group and are isostructural. In the crystals of title compounds, the ions and water molecules interact via N−H⋯O, O−H⋯O and C−H⋯O hydrogen bonds and π−π stacking interactions to produce blocks. The relationship between the distance X⋯O between the halogen atom (X=Cl, Br, I) of meta-halobenzoate anion and the O-atom from the ethoxy group of cation from neighbouring blocks and crystal packing is observed in the crystals of the title compounds.

In the title compound, [Ir(C11H8N)2(C18H14N)], the IrIII ion adopts a distorted octahedral coordination environment defined by three C,N-chelating ligands, one stemming from a 2-(4-phenyl-5-methylpyridin-2-yl)phenyl ligand and two from 2-(pyridin-2-yl)phenyl ligands, arranged in a facial manner. The IrIII ion lies almost in the equatorial plane [deviation = 0.0069 (15) Å]. In the crystal, intermolecular π–π stacking interactions, as well as intermolecular C—H...π interactions, are present, leading to a three-dimensional network.

The title compound, C17H18O2, crystallizes in two-dimensional sheets, in which the 2-(pentyloxy)dibenzo[b,d]furan molecules are arranged in a head-to-head and tail-to-tail fashion that enables hydrophobic interactions between fully extended 2-pentoxy chains and π–π stacking between dibenzofuran rings in adjacent rings. Nearest intermolecular π-π stacking contacts are 3.3731 (12) Å. The molecule is nearly planar with an r.m.s. deviation of 0.0803 Å from the mean plane defined by the nineteen non-hydrogen atoms.

In the title compound, C8H5ClN2Se, the dihedral angle between the planes of the selenadiazole and chlorophenyl rings is 16.6 (2)°. In the crystal, the packing of the molecules is consolidated by weak C—H...N hydrogen bonds, which generate [001] chains, and π–π stacking interactions are observed between the phenyl and selenadiazole rings, with a centroid–centroid distance of 3.884 (2) Å. There is also a short Se...Cl contact of 3.468 (1) Å

Polymorph I of the title compound, C7H5NO3, is approximately planar: the dihedral angle between the benzene ring and the nitro group is 10.41 (4)° and the aldehyde O atom deviates from the ring plane by 0.165 (1) Å. In the crystal, aromatic π–π stacking interactions are observed [centroid–centroid separation = 3.7363 (5) Å].

The molecular structure of the title compound, [FePt(CN)4(C14H8N2)2(H2O)2]n, consists of one-dimensional polymeric [–Fe–NC–Pt(CN)2–CN–]∞ chains. Two water molecules and two monodentate 1,4-bis(pyridin-4-yl)buta-1,3-diyne (bpb) ligand molecules complete the octahedral coordination sphere of the FeII atoms. The Fe—N(py) bond length (py is pyridine) is 2.2700 (15) Å, Fe—N(cyanide) is 2.1185 (16) Å and the Fe—O distance is 2.1275 (14) Å. The water molecules are hydrogen bonded to either bpb ligands or cyanide groups of the planar [Pt(CN)4]2− anion of adjacent polymeric chains. These O—H...N hydrogen bonds, in conjunction with offset and tilted π–π stacking interactions between bpb ligands and cyanide groups, extend the one-dimensional chains into a three-dimensional assembly.

The reaction of cuprous bromide with a mixture of 1,1-bis(diphenylphosphanyl)methane (dppm: C25H22P2) and N-allylthiourea (ATU: C4H8N2S) in acetonitrile yielded the title solvated dinuclear complex, [Cu2Br2(C4H8N2S)(C25H22P2)2]·2C2H3N or [Cu2Br2(ATU)(dppm)2]·2CH3CN. Both Cu+ ions adopt distorted tetrahedral geometries, being coordinated by one terminal Br atom, one μ2-S atom of the bridging ATU ligand and two P atoms of the bridging dppm ligands. Within the complex, intramolecular C—H...S, C—H...π, N—H...Br and π–π stacking interactions are observed. In the crystal, the components are linked by N—H...Br and C—H...N hydrogen bonds and weak π–π stacking interactions, generating chains propagating in the [100] direction.

The title compounds, 6-(2-hydroxybenzyl)-5H-thiazolo[3,2-a]pyrimidin-5-one, C13H8N2O3S, (1), and 6-(2-hydroxybenzyl)-3-methyl-5H-thiazolo[3,2-a]pyrimidin-5-one, C14H10N2O3S, (2), were synthesized when a chromone-3-carboxylic acid, activated with (benzotriazol-1-yloxy)tripyrrolidinylphosphonium hexafluoridophosphate (PyBOP), was reacted with a primary heteromamine. Instead of the expected amidation, the unusual title thiazolopyrimidine-5-one derivatives were obtained serendipitously and a mechanism of formation is proposed. Both compounds present an intramolecular O—H...O hydrogen bond, which generates an S(6) ring. The dihedral angles between the heterocyclic moiety and the 2-hydroxybenzoyl ring are 55.22 (5) and 46.83 (6)° for (1) and (2), respectively. In the crystals, the molecules are linked by weak C—H...O hydrogen bonds and π–π stacking interactions.

Both the 3-amino-2H,4H-1,2,4-triazolium cation and the pyrazine-2-carboxylate anion in the title salt, C2H5N4+·C5H3N2O2−, were formed by an unexpected decarboxylation reaction, from 5-amino-1H-1,2,4-triazole-3-carboxylic acid and pyrazine-2,3-dicarboxylic acid, respectively. The dihedral angle between the pyrazine ring (r.m.s. deviation = 0.008 Å) and the carboxylate group in the anion is 3.7 (3)°. The extended structure of the salt contains a supramolecular zigzag tape in which cations and anions are engaged in strong and highly directional N—H...N,O hydrogen bonds, forming R22(8) and R22(9) graph-set motifs. The packing between the tapes is mediated by π–π stacking interactions between the triazole and pyrazine rings.

In the molecules of the title compounds, methyl 5-bromo-2-[(2-chloroquinolin-3-yl)methoxy]benzoate, C18H13BrClNO3, (I), methyl 5-bromo-2-[(2-chloro-6-methylquinolin-3-yl)methoxy]benzoate, C19H15BrClNO3, (II), methyl 2-[(2-chloro-6-methylquinolin-3-yl)methoxy]benzoate, C19H16ClNO3, (III), which crystallizes with Z′ = 4 in space group P212121, and 2-chloro-3-[(naphthalen-1-yloxy)methyl]quinoline, C20H14ClNO, (IV), the non-H atoms are nearly coplanar, but in {5-[(2-chloroquinolin-3-yl)methoxy]-4-(hydroxymethyl)-6-methylpyridin-3-yl}methanol, C18H17ClN2O3, (V), the planes of the quinoline unit and of the unfused pyridine ring are almost parallel, although not coplanar. The molecules of (I) are linked by two independent π–π stacking interactions to form chains, but there are no hydrogen bonds present in the structure. In (II), the molecules are weakly linked into chains by a single type of π–π stacking interaction. In (III), three of the four independent molecules are linked by π–π stacking interactions but the other molecule does not participate in such interactions. Weak C—H...O hydrogen bonds link the molecules into three types of chains, two of which contain just one type of independent molecule while the third type of chain contains two types of molecule. The molecules of (IV) are linked into chains by a C—H...π(arene) hydrogen bond, but π–π stacking interactions are absent. In (V), there is an intramolecular O—H...O hydrogen bond, and molecules are linked into sheets by a combination of O—H...N hydrogen bonds and π–π stacking interactions.