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In the title compound, C19H17NO5S, the cyclohexene ring adopts nearly an envelope conformation. In the crystal, molecules are linked by C—H...O hydrogen bonds, forming a three-dimensional network. In addition, C—H...π interactions connect the molecules by forming layers parallel to the (010) plane. According to the Hirshfeld surface analysis, H...H (36.9%), O...H/H...O (31.0%), C...H/H...C (18.9%) and S...H/H...S (7.9%) interactions are the most significant contributors to the crystal packing.

In the title compound, C20H17BrO5S, molecules are connected by intermolecular C—H...S hydrogen bonds with R22(10) ring motifs, forming ribbons along the b-axis direction. C—H...π interactions consolidate the ribbon structure while van der Waals forces between the ribbons ensure the cohesion of the crystal structure. According to a Hirshfeld surface analysis, H...H (40.5%), O...H/H...O (27.0%), C...H/H...C (13.9%) and Br...H/H...Br (11.7%) interactions are the most significant contributors to the crystal packing. The thiophene ring and its adjacent dicarboxylate group and the three adjacent carbon atoms of the central hexene ring to which they are attached were refined as disordered over two sets of sites having occupancies of 0.8378 (15) and 0.1622 (15). The thiophene group is disordered by a rotation of 180° around one bond.

The asymmetric unit of the title compound, C25H18N6·H2O, comproses two molecules (I and II), together with a water molecule. The terminal phenyl groups attached to the methyl groups of the molecules I and II do not overlap completely, but are approximately perpendicular. In the crystal, the molecules are connected by N—H...N, C—H...N, O—H...N and N—H...O hydrogen bonds with each other directly and through water molecules, forming layers parallel to the (001) plane. C—H...π interactions between these layers ensure the cohesion of the crystal structure. A Hirshfeld surface analysis indicates that H...H (39.1% for molecule I; 40.0% for molecule II), C...H/H...C (26.6% for molecule I and 25.8% for molecule II) and N...H/H...N (24.3% for molecules I and II) interactions are the most important contributors to the crystal packing.

In the ten-membered 1,3,4,6-tetrahydro-2H-pyrido[1,2-a]pyrimidine ring system of the title compound, C17H15N5, the 1,2-dihydropyridine ring is essentially planar (r.m.s. deviation = 0.001 Å), while the 1,3-diazinane ring has a distorted twist-boat conformation. In the crystal, molecules are linked by N—H...N and C—H...N hydrogen bonds, forming a three-dimensional network. In addition, C—H...π interactions form layers parallel to the (100) plane. Thus, crystal-structure cohesion is ensured. According to a Hirshfeld surface study, H...H (40.4%), N...H/H...N (28.6%) and C...H/H...C (24.1%) interactions are the most important contributors to the crystal packing.

The asymmetric unit of the title compound, 2C31H28N2O4S·C2H6O, contains a parent molecule and a half molecule of ethanol solvent. The main compound stabilizes its molecular conformation by forming a ring with an R12(7) motif with the ethanol solvent molecule. In the crystal, molecules are connected by C—H...O and O—H...O hydrogen bonds, forming a three-dimensional network. In addition, C—H...π interactions also strengthen the molecular packing.

In the title compound, C21H15N5OS2, molecular pairs are linked by N—H...N hydrogen bonds along the c-axis direction and C—H...S and C—H...O hydrogen bonds along the b-axis direction, with R22(12) and R22(16) motifs, respectively, thus forming layers parallel to the (10\overline{4}) plane. In addition, C=S...π and C[triple-bond]N...π interactions between the layers ensure crystal cohesion. The Hirshfeld surface analysis indicates that the major contributions to the crystal packing are H...H (43.0%), C...H/H...C (16.9%), N...H/H...N (11.3%) and S...H/H...S (10.9%) interactions.

In the crystal of the title compound, C6H9ClN2O, molecular pairs form dimers with an R22(8) motif through N—H...O hydrogen bonds. These dimers are connect into ribbons parallel to the (100) plane with R44(10) motifs by N—H...O hydrogen bonds along the c-axis direction. In addition, π–π [centroid-to-centroid distance = 3.4635 (9) Å] and C—Cl...π interactions between the ribbons form layers parallel to the (100) plane. The three-dimensional consolidation of the crystal structure is also ensured by Cl...H and Cl...Cl interactions between these layers. According to a Hirshfeld surface study, H...H (43.3%), Cl...H/H...Cl (22.1%) and O...H/H...O (18.7%) interactions are the most significant contributors to the crystal packing.

The crystal structures and Hirshfeld surface analyses of three similar azo compounds are reported. Methyl 4-{2,2-dichloro-1-[(E)-phenyldiazenyl]ethenyl}benzoate, C16H12Cl2N2O2, (I), and methyl 4-{2,2-dichloro-1-[(E)-(4-methylphenyl)diazenyl]ethenyl}benzoate, C17H14Cl2N2O2, (II), crystallize in the space group P21/c with Z = 4, and methyl 4-{2,2-dichloro-1-[(E)-(3,4-dimethylphenyl)diazenyl]ethenyl}benzoate, C18H16Cl2N2O2, (III), in the space group P\overline{1} with Z = 2. In the crystal of (I), molecules are linked by C—H...N hydrogen bonds, forming chains with C(6) motifs parallel to the b axis. Short intermolecular Cl...O contacts of 2.8421 (16) Å and weak van der Waals interactions between these chains stabilize the crystal structure. In (II), molecules are linked by C—H...O hydrogen bonds and C—Cl...π interactions, forming layers parallel to (010). Weak van der Waals interactions between these layers consolidate the molecular packing. In (III), molecules are linked by C—H...π and C—Cl...π interactions forming chains parallel to [011]. Furthermore, these chains are connected by C—Cl...π interactions parallel to the a axis, forming (0\overline{1}1) layers. The stability of the molecular packing is ensured by van der Waals forces between these layers.

In the title compound, C20H18N2S, the asymmetric unit comprises two similar molecules (A and B). In molecule A, the central thiophene ring makes dihedral angles of 89.96 (12) and 57.39 (13)° with the 1H-pyrrole rings, which are bent at 83.22 (14)° relative to each other, and makes an angle of 85.98 (11)° with the phenyl ring. In molecule B, the corresponding dihedral angles are 89.49 (13), 54.64 (12)°, 83.62 (14)° and 85.67 (11)°, respectively. In the crystal, molecular pairs are bonded to each other by N—H...N interactions. N—H...π and C—H...π interactions further connect the molecules, forming a three-dimensional network. A Hirshfeld surface analysis indicates that H...H (57.1% for molecule A; 57.3% for molecule B), C...H/H...C (30.7% for molecules A and B) and S...H/H...S (6.2% for molecule A; 6.4% for molecule B) interactions are the most important contributors to the crystal packing.

In the title compound, C25H25NO7S, the molecular conformation is stabilized by intramolecular O—H...O and N—H...O hydrogen bonds, which form S(6) and S(8) ring motifs, respectively. The molecules are bent at the S atom with a C—SO2—NH—C torsion angle of −70.86 (11)°. In the crystal, molecules are linked by C—H...O and N—H...O hydrogen bonds, forming molecular layers parallel to the (100) plane. C—H...π interactions are observed between these layers.

We report the synthesis and single-crystal X-ray diffraction, magnetic, and luminescence measurements of a novel family of luminescent cage-like tetranuclear silsesquioxanes (PhSiO1.5)8(LnO1.5)4(O)(C5H8O2)6(EtOH)2(CH3CN)2⋅2CH3CN (where Ln = Tb, 1; Tb/Eu, 2; and Gd, 3), featuring seven-coordinated lanthanide ions arranged in a one-capped trigonal prism geometry. Compounds 1 and 2 exhibit characteristic Tb3+ and Tb3+/Eu3+-related emissions, respectively, sensitized by the chelating antenna acetylacetonate (acac) ligands upon excitation in the UV and visible spectral regions. Compound 3 is used to assess the energies of the triplet states of the acac ligand. For compound 1, theoretical calculations on the intramolecular energy transfer and multiphonon rates indicate a thermal balance between the 5D4 Stark components, while the mixed Tb3+/Eu3+ analog 2, with a Tb:Eu ratio of 3:1, showcases intra-cluster Tb3+-to-Eu3+ energy transfer, calculated theoretically as a function of temperature. By utilizing the intensity ratio between the 5D4→7F5 (Tb3+) and 5D0→7F2 (Eu3+) transitions in the range 11–373 K, we demonstrate the realization of a ratiometric luminescent thermometer with compound 2, operating in the range 11–373 K with a maximum relative sensitivity of 2.0% K−1 at 373 K. These findings highlight the potential of cage-like silsesquioxanes as versatile materials for optical sensing-enabled applications.

In the title compound, C16H13N7O2, the 3,5-dimethylphenyl and 4-nitrophenyl rings are inclined to the central 2H-1,2,3-triazole ring by 1.80 (7) and 1.79 (7)°, respectively, and to one another by 2.16 (7)°. In the crystal, the molecules are linked by C—H...N hydrogen bonds and π–π stacking interactions [centroid-to-centroid distances = 3.7295 (9) and 3.7971 (9) Å], forming ribbons along the b-axis direction. These ribbons are connected to each other by weak van der Waals interactions and the stability of the crystal structure is ensured. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H...H (31.5%), N...H/H...N (19.2%), O...H/H...O (14.5%), N...C/C...C (10.9%) and C...H/H...C (10.2%) contacts.

In the title compound, C16H13BrO, the planes of the aromatic rings are inclined at an angle of 23.49 (15)°, and the configuration about the C=C bond is E. In the crystal, the molecules are linked into chains by weak C—H...O interactions along the b axis. Successive chains form a zigzag structure along the c axis, and these chains are connected to each other by face-to-face π–π stacking interactions along the a axis. These layers, parallel to the (001) plane, are linked by van der Waals interactions, thus consolidating the crystal structure. Hirshfeld surface analysis showed that the most significant contacts in the structure are H...H (43.1%), C...H/H...C (17.4%), Br...H/H...Br (14.9%), C...C (11.9%) and O...H/H...O (9.8%).

The title compound, C15H14O2, adopts an E configuration about the C=C double bond. The furan ring is inclined to the phenyl ring by 12.03 (9)°. In the crystal, pairs of molecules are linked by C—H...O hydrogen bonds, forming dimers with R22(14) ring motifs. The molecules are connected via C—H...π interactions, forming a three dimensional network. No π–π interactions are observed.

In the title compound, C25H17N3O5S2, intramolecular π–π interactions [centroid-to-centroid distance = 3.5640 (9) Å] are observed between the furan and benzene rings of the 4-cyanophenyl group. In the crystal, molecules are connected via C—H...O and C—H...N hydrogen bonds, forming layers parallel to the (100) plane. These layers are interconnected by C—H...π interactions and weak van der Waals interactions. Hirshfeld surface analysis indicates that H...H (30.2%), N...H/H...N (22.3%), C...H/H...C (17.9%) and O...H/H...O (15.4%) interactions make the most significant contributions to the crystal packing.

The crystal structures and Hirshfeld surface analyses of four similar azo compounds are reported. (E)-1-[1-(4-tert-Butylphenyl)-2,2-dichloroethenyl]-2-phenyldiazene, C18H18Cl2N2, (I), and (E)-1-[1-(4-tert-butylphenyl)-2,2-dichloroethenyl]-2-(4-methylphenyl)diazene, C19H20Cl2N2, (II), crystallize in the monoclinic space group C2/c with Z = 8, and (E)-1-[1-(4-tert-butylphenyl)-2,2-dichloroethenyl]-2-(4-methoxyphenyl)diazene, C19H20Cl2N2O, (III), in the monoclinic space group P21/c with Z = 4. (E)-1-[1-(4-tert-Butylphenyl)-2,2-dichloroethenyl]-2-(3-methylphenyl)diazene, C19H20Cl2N2, (IV), crystallizes in the triclinic space group P\overline{1} with Z = 4 and comprises two molecules (A and B) in the asymmetric unit. In the crystal structures of (I) and (II), molecules are linked by C—H...π and C—Cl...π interactions, forming layers parallel to (\overline{2}02), while molecules of (III) are linked by C—H...O contacts, C—H...π and C—Cl...π interactions forming layers parallel to (\overline{3}02). The stability of the molecular packing is ensured by van der Waals forces between these layers. In the crystal structure of (IV), molecules are linked by C—H...π and C—Cl...π interactions, forming a tri-periodic network.

In the title compound, C20H12N6O·C2H6OS, the [1,2,4]triazolo[1,5-a]pyridine ring system is almost planar and makes dihedral angles of 16.33 (7) and 46.80 (7)°, respectively, with the phenylamino and phenyl rings. In the crystal, molecules are linked by intermolecular N—H...O and C—H...O hydrogen bonds into chains along the b-axis direction through the dimethyl sulfoxide solvent molecule, forming C(10)R21(6) motifs. These chains are connected via S—O...π interactions, π–π stacking interactions between the pyridine rings [centroid-to-centroid distance = 3.6662 (9) Å] and van der Waals interactions. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H...H (28.1%), C...H/H...C (27.2%), N...H/H...N (19.4%) and O...H/H...O (9.8%) interactions.

In the title compound, C19H15N5S, the thiophene ring is disordered in a 0.6:0.4 ratio by an approximate 180° rotation of the ring around the C—C bond linking it to the pyridine ring. In the crystal, the molecules are linked by N—H...N hydrogen bonds into dimers with an R22(12) motif, forming chains along the b-axis direction. These chains are connected to each other by further N—H...N hydrogen bonds, forming a three-dimensional network. Furthermore, N—H...π and π–π [centroid–centroid separations = 3.899 (8) and 3.7938 (12) Å] interactions also contribute to the crystal cohesion. A Hirshfeld surface analysis indicated that the most important contributions to the surface contacts are from H...H (46.1%), N...H/H...N (20.4%) and C...H/H...C (17.4%) interactions.

The asymmetric unit of the title compound, C11H7N5OS, contains two independent molecules (1 and 2). The thiophene ring in molecule 2 is rotationally disordered (flip disorder) by ca 180° (around the single C—C bond, to which it is attached) over two sites with the site-occupation factors of 0.9 and 0.1. These two orientations of the thiophene ring in molecule 2 are not equivalent. In the crystal, molecules are linked by intermolecular N—H...O and N—H...N hydrogen bonds into ribbons parallel to (022) along the a axis. Within the (022) planes, these ribbons are connected by van der Waals interactions and between the (022) planes by N—H...O hydrogen bonds. In molecule 1, Hirshfeld surface analysis showed that the most important contributions to the crystal packing are from N...H/H...N (27.1%), H...H (17.6%), C...H/H...C (13.6%) and O...H/H...O (9.3%) interactions, while in molecule 2, H...H (25.4%) interactions are the most significant contributors to the crystal packing.

In the title compound, C31H44O5, molecules are connected by O—H...O and C—H...O hydrogen bonds, forming hydrogen-bonded zigzag chains running along the b axis and parallel to the (001) plane. The molecular packing is stabilized by van der Waals interactions between these chains along the a and c axes. The intermolecular interactions in the crystal structure were quantified and analysed using Hirshfeld surface analysis.

In the title compound, C20H26O5, the two cyclohexane rings adopt boat and half-chair conformations. In the crystal, adjacent molecules are connected by intermolecular C—H...O hydrogen bonds, forming a three-dimensional network. According to a Hirshfeld surface study, H...H interactions are the most significant contributors to the crystal packing (63.0%).

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.

In the title compound, C32H29N5O2·C3H7NO, the bicyclo[3.3.1]nonane ring system adopts a half-chair/twist-boat conformation, with the phenyl rings in equatorial orientations with respect to the piperidine ring. The two oxane rings of the 2-oxabicyclo[2.2.2]octane ring system exhibit a distorted boat conformation. Intermolecular C—H...O and C—H...N hydrogen bonds connect the molecules in the crystal, generating layers extending parallel to (100). These layers are connected by C—H...π interactions. A Hirshfeld surface analysis was performed to quantify the contributions of the different intermolecular interactions, indicating that the most important contributions to the crystal packing are from H...H (52.5%), N...H/H...N (19.2%), C...H/H...C (18.8%) and O...H/H...O (8.3%) interactions.

The crystal used for structure determination contained, along with the title compound, C17H14BrN3O4, an admixture [0.0324 (11)] of its 7-bromo isomer. The 2,3-dihydro-1H-indole ring system is nearly planar, while the conformation of the 4H-pyran ring is close to a flattened boat. The mean planes of these fragments form a dihedral angle of 86.67 (9)°. The carboxylate group lies near the plane of 4H-pyran, its orientation is stabilized by an intramolecular C—H...O contact. In the crystal, the molecules are connected into layers by N—H...N and N—H...O hydrogen bonds. The most important contributions to the crystal packing are from H...H (33.1%), O...H/H...O (16.3%), N...H/H...N (12.1%), Br...H/H...Br (11.5%) and C...H/H...C (10.6%) interactions.

In the title compound, C19H13BrN2O, the pyridine ring is essentially planar [maximum deviation = 0.024 (4) Å for the N atom] and makes dihedral angles of 74.6 (2) and 65.8 (2)°, respectively, with the phenyl and bromophenyl rings, which subtend a dihedral angle of 63.1 (2)°. In the crystal, molecules are connected along the c-axis direction via C—Br...π interactions, generating zigzag chains parallel to the (010) plane. C—H...N and C—H...O hydrogen-bonding interactions further connect the molecules, forming a three-dimensional network and reinforcing the molecular packing. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H...H (36.2%), C...H/H...C (21.6%), N...H/H...N (12.2%), and Br...H/H...Br (10.8%) interactions.

In 2-amino-4-(4-bromophenyl)-6-oxo-1-phenyl-1,4,5,6-tetrahydropyridine-3-carbonitrile hemihydrate, C18H14BrN3O·0.5H2O, (I), pairs of molecules are linked by pairs of N—H...N hydrogen bonds, forming dimers with an R22(12) ring motif. The dimers are connected by N—H...Br and O—H...O hydrogen bonds, and C—Br...π interactions, forming layers parallel to the (010) plane. 1,6-Diamino-2-oxo-4-phenyl-1,2-dihydropyridine-3,5-dicarbonitrile, C13H9N5O, (II), crystallizes in the triclinic space group P\overline{1} with two independent molecules (IIA and IIB) in the asymmetric unit. In the crystal of (II), molecules IIA and IIB are linked by intermolecular N—H...N and N—H...O hydrogen bonds into layers parallel to (001). These layers are connected along the c-axis direction by weak C—H...N contacts. C—H...π and C—N...π interactions connect adjacent molecules, forming chains along the a-axis direction. In (I) and (II), the stability of the packing is ensured by van der Waals interactions between the layers. In (I), Hirshfeld surface analysis showed that the most important contributions to the crystal packing are from H...H (37.9%), C...H/H...C (18.4%), Br...H/H...Br (13.3%), N...H/H...N (11.5%) and O...H/H...O (10.0%) interactions, while in (II), H...H interactions are the most significant contributors to the crystal packing (27.6% for molecule IIA and 23.1% for molecule IIB).

A new polymorph of the title compound, C14H8Br3N3O2, (form-2) was obtained in the same manner as the previously reported form-1 [Akkurt et al. (2022). Acta Cryst. E78, 732–736]. The structure of the new polymorph is stabilized by a C—H...O hydrogen bond that links molecules into chains. These chains are linked by face-to-face π–π stacking interactions, resulting in a layered structure. Short inter-molecular Br...O contacts and van der Waals interactions between the layers aid in the cohesion of the crystal packing. In the previously reported form-1, C—H...Br interactions connect molecules into zigzag chains, which are linked by C—Br...π interactions into layers, whereas the van der Waals interactions between the layers stabilize the crystal packing of form-2. Hirshfeld molecular surface analysis was used to compare the intermolecular interactions of the polymorphs.

The whole molecule of the title compound, C22H19NO2, is generated by twofold rotational symmetry. The N atom exhibits a trigonal-planar geometry and is located on the twofold rotation axis. In the crystal, molecules are linked by C—H...O contacts with R22(12) ring motifs, and C—H...π interactions, resulting in ribbons along the c-axis direction. van der Waals interactions between these ribbons consolidate the molecular packing. Hirshfeld surface analysis indicates that the greatest contributions to the crystal packing are from H...H (45.5%), C...H/H...C (38.2%) and O...H/H...O (16.0%) interactions.

The title compound, C20H24BrNO2, is chiral at the carbon atoms on either side of the oxygen atom of the oxazolidine ring and crystallizes as a racemate. The 1,3-oxazolidine ring adopts an envelope conformation with the N atom in an endo position. The mean plane of the oxazolidine ring makes dihedral angles of 77.74 (10) and 45.50 (11)°, respectively, with the 4-bromophenol and 1,3,5-trimethylbenzene rings. In the crystal, adjacent molecules are connected via C—H...O hydrogen bonds and C—H...π interactions into layers parallel to the (200) plane. The packing is strengthened by van der Waals interactions between parallel molecular layers. A Hirshfeld surface analysis shows that H...H (58.2%), C...H/H...C (18.9%), and Br...H/H...Br (11.5%) interactions are the most abundant in the crystal packing.

The molecule of the title compound, C14H8Br3N3O2, consists of three almost planar groups: the central dibromoethenyldiazene fragment and two attached aromatic rings. The mean planes of these rings form dihedral angles with the plane of the central fragment of 26.35 (15) and 72.57 (14)° for bromine- and nitro-substituted rings, respectively. In the crystal, C—H...Br interactions connect molecules, generating zigzag C(8) chains along the [100] direction. These chains are linked by C—Br...π interactions into layers parallel to (001). van der Waals interactions between the layers aid in the cohesion of the crystal packing. The most substantial contributions to crystal packing, according to a Hirshfeld surface analysis, are from Br...H/H...Br (20.9%), C...H/H...C (15.2%), O...H/H...O (12.6%) and H...H (11.7%) contacts.

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, 2C16H27NO·H2O, crystallizes in the monoclinic P21/c space group with two independent molecules (A and B) in the asymmetric unit. In the crystal, molecules A and B are linked through the water molecules by intermolecular O—H...O and O—H...N hydrogen bonds, producing chains along the b-axis direction. These chains are linked with neighboring chains parallel to the (103) plane via C—H...π interactions, generating ribbons along the b-axis direction. The stability of the molecular packaging is ensured by van der Waals interactions between the ribbons. According to the Hirshfeld surface study, H...H interactions are the most significant contributors to the crystal packing (80.3% for molecule A and 84.8% for molecule B).

In the title compound, C14H8Br2FN3O2, the nitro-substituted benzene ring and the 4-fluorophenyl ring form a dihedral angle of 65.73 (7)°. In the crystal, molecules are linked into chains by C—H...O hydrogen bonds running parallel to the c-axis direction. The crystal packing is consolidated by C—F...π interactions and π–π stacking interactions, and short Br...O [2.9828 (13) Å] contacts are observed. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H...H (17.4%), O...H/H...O (16.3%), Br...H/H...Br (15.5%), Br...C/C...Br (10.1%) and F...H/H...F (8.1%) 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.

The central tetrahydropyridine ring of the title compound, C19H17N3O2, adopts a screw-boat conformation. In the crystal, strong C—H...O and N—H...N hydrogen bonds form dimers with R22(14) and R22(12) ring motifs, respectively, between consecutive molecules along the c-axis direction. Intermolecular N—H...O and C—H...O hydrogen bonds connect these dimers, forming a three-dimensional network. C—H...π interactions and π–π stacking interactions contribute to the stabilization of the molecular packing. A Hirshfeld surface analysis indicates that the contributions from the most prevalent interactions are H...H (47.1%), C...H/H...C (20.9%), O...H/H...O (15.3%) and N...H/H...N (11.4%).

The crystal structure of the title compound, C20H16BrN3O2, was determined using an inversion twin. Its asymmetric unit comprises two crystallographically independent molecules (A and B) being the stereoisomers. Both molecules are linked by pairs of N—H...O hydrogen bonds, forming a dimer with an R22(16) ring motif. The dimers are connected by further N—H...O and N—H...N hydrogen bonds, forming chains along the c-axis direction·C—Br...π interactions between these chains contribute to the stabilization of the molecular packing. Hirshfeld surface analysis showed that the most important contributions to the crystal packing are from H...H, C...H/H...C, O...H/H...O, Br...H/H...Br and N...H/H...N interactions.

The influence of Yb3+ cations substitution for Pr3+ on the structure and catalytic activity of (Pr1−xYbx)2Zr2O7 powders synthesized via coprecipitation followed by calcination is studied using a combination of long- (s-XRD), medium- (Raman, FT-IR, and SEM-EDS) and short-range (XAFS) sensitive methods, as well as adsorption and catalytic techniques. It is established that chemical composition and calcination temperature are the two major factors that govern the phase composition, crystallographic, and local-structure parameters of these polycrystalline materials. The crystallographic and local-structure parameters of (Pr1−xYbx)2Zr2O7 samples prepared at 1400 °C/3 h demonstrate a tight correlation with their catalytic activity towards propane cracking. The progressive replacement of Pr3+ with Yb3+ cations gives rise to an increase in the catalytic activity. A mechanism of the catalytic cracking of propane is proposed, which considers the geometrical match between the metal–oxygen (Pr–O, Yb–O, and Zr–O) bond lengths within the active sites and the size of adsorbed propane molecule to be the decisive factor governing the reaction route.

The molecular conformation of the title compound, C20H15Cl2N3O2, is stabilized by an intramolecular O—H...O hydrogen bond, forming an S(6) ring motif. The central pyridine ring is almost planar [maximum deviation = 0.074 (3) Å]. It subtends dihedral angles of 86.10 (15) and 87.17 (14)°, respectively, with the phenyl and dichlorophenyl rings, which are at an angle of 21.28 (15)° to each other. The =C(—OH)CH3 group is coplanar. In the crystal, molecules are linked by intermolecular N—H...N and C—H...N hydrogen bonds, and N—H...π and C—H...π interactions, forming a three-dimensional network. The most important contributions to the crystal packing are from H...H (33.1%), C...H/H...C (22.5%), Cl...H/H...Cl (14.1%), O...H/H...O (11.9%) and N...H/H...N (9.7%) interactions.

The molecular conformation of the title compound, C17H14ClN3O4, is stabilized by an intramolecular C—H...O contact, forming an S(6) ring motif. In the crystal, the molecules are connected by N—H...O hydrogen-bond pairs along the b-axis direction as dimers with R22(8) and R22(14) ring motifs and as ribbons formed by intermolecular C—H...N hydrogen bonds. There are weak van der Waals interactions between the ribbons. The most important contributions to the surface contacts are from H...H (34.9%), O...H/H...O (19.2%), C...H/H...C (11.9%), Cl...H/H...Cl (10.7%) and N...H/H...N (10.4%) interactions, as concluded from a Hirshfeld surface analysis.

In the title compound, C16H15N5, the 1,4-dihydropyridine ring has a shallow boat conformation, while the 1,3-diazinane ring adopts an envelope conformation. In the crystal, pairwise N—H...N hydrogen bonds generate centrosymmetric dimers featuring R22(12) motifs and C—H...N contacts connect these dimers to form double layers lying parallel to (001). Weak C—H...π and N—H...π interactions help to consolidate the double layers and van der Waals interactions occur between layers. A Hirshfeld surface analysis indicates that the most significant contributions to the crystal packing are from H...H (38.5%), N...H/H...N (33.3%) and C...H/H...C (27.3%) contacts.

In the molecular structure of the title compound, C16H13Cl2N5, the 1,4-dihydropyridine ring of the 1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrimidine ring system adopts a screw-boat conformation, while the 1,3-diazinane ring is puckered. In the crystal, intermolecular N—H...N and C—H...N hydrogen bonds form molecular sheets parallel to the (110) and (\overline{1}10) planes, crossing each other. Adjacent molecules are further linked by C—H...π interactions, which form zigzag chains propagating parallel to [100]. A Hirshfeld surface analysis indicates that the most significant contributions to the crystal packing are from N...H/H...N (28.4%), H...H (24.5%), C...H/H...C (21.4%) and Cl...H/H...Cl (16.1%) contacts.

In the title compound, C25H22N2O3S·0.04H2O, the central cyclohexane ring adopts a chair conformation. In the crystal, molecules are linked by N—H...O, C—H...O, and C—H...N hydrogen bonds, forming the molecular layers parallel to the bc plane, which interact by the van der Waals forces between them. A Hirshfeld surface analysis indicates that the contributions from the most prevalent interactions are H...H (41.2%), C...H/H...C (20.3%), O...H/H...O (17.8%) and N...H/H...N (10.6%).

The title compound, C23H19BrN4O2, is a product of an azo coupling reaction between 3,4-bis(4-methoxyphenyl)imidazole and 4-bromophenyldiazonium tetrafluoroborate. Its crystal structure was determined using data collected at 120 K. The molecule adopts a trans configuration with respect to the N=N double bond. The imidazole and aryl rings attached to the azo linkage are coplanar within 12.73 (14)°, which indicates significant electron delocalization within the molecule. In the crystal, the molecules form centrosymmetric dimers via pairs of N—H...O hydrogen bonds.

In the title compound, C28H21N3O, the 1,2-dihydropyridine ring of the 1,2,7,8-tetrahydroisoquinoline ring system is planar as expected, while the cyclohexa-1,3-diene ring has a twist-boat conformation, with Cremer–Pople parameters QT = 0.367 (2) A, θ = 117.3 (3)° and φ = 327.3 (4)°. The dihedral angles between the best planes through the isoquinoline ring system and the three phenyl rings are 81.69 (12), 82.45 (11) and 47.36 (10)°. In the crystal, molecules are linked via N—H...O and C—H...N hydrogen bonds, forming a three-dimensional network. Furthermore, the crystal packing is dominated by C—H...π bonds with a strong interaction involving the phenyl H atoms. The role of the intermolecular interactions in the crystal packing was clarified using Hirshfeld surface analysis, and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H...H (46.0%), C...H/H...C (35.1%) and N...H/H...N (10.5%) contacts.

The title compound, C27H24N2O5, is a product of the deamination reaction from aza-14-crown-4 ether containing the γ-piperidone subunit. The title molecule contains a 16-membered macrocycle with the conformation of the C—O—C—C—O—C—C—O—C polyether chain being t–g(-)–t–t–g(+)–t (t = trans, 180°; g = gauche, ±60°). The dihedral angle between the planes of the benzene rings fused to the aza-14-crown-4-ether moiety is 31.11 (14)°. The cavity size inside the macrocycle is 4.72 Å. The macrocycle is significantly flattened as a result of the extended conjugated system. Steric repulsion between the pyridylcarboxamide fragment and the benzene ring results in a slight deviation of macrocycle from planarity. The structure also features intramolecular hydrogen bonding, which results in a deviation of the angle between the planes of amide and pyridyl groups from planarity: this angle is 16.32 (18)°. In the crystal, the molecules are linked into infinite zigzag chains via intermolecular C—H...π contacts. The chains are bound into layers parallel to (100) by weak intermolecular C—H...O hydrogen bonds.

A family of unusual octacopper cage methylsilsesquioxanes 1–4 were prepared and characterized. Features of their cagelike (prismatic) structure were established using X-ray diffraction studies. Effects of distortion of prismatic cages 1–4 due to variation of (i) additional alkaline metal ions (K, Rb, or Cs), (ii) combination of solvating ligands, and (iii) nature of encapsulating species were found. Opportunities for the design of supramolecular 1D extended structures were found. These opportunities are based on (i) formate linkers between copper centers (in the case of Cu8K2-based compound 2) or (ii) crown ether-like contacts between cesium ions and siloxane cycles (in the case of Cu8Cs2-based compound 4). Cu8Cs2-complex 4 was evaluated in the catalysis of alkanes and alcohols. Complex 4 exhibits high catalytic activity. The yield of cyclohexane oxidation products is 35%. The presence of nitric acid is necessary as a co-catalyst. The oxidation of alcohols with the participation of complex 4 as a catalyst and tert-butyl hydroperoxide as an oxidizer also proceeds in high yields of up to 98%.

The series of substituted 1,2,4-selenodiazolium tetraphenylborate complexes were synthesized via cyclization between 2-pyridylselenylchloride, followed by the anion metathesis, and fully characterized. The utilization of tetraphenylborate anion, a strong π-electron donor via its phenyl rings, promoted the formation of assemblies exhibiting selenium–π interactions. The chalcogen bonding (ChB) interactions involving the π-systems of the tetraphenylborate anion were studied using density functional theory (DFT) calculations, where “mutated” anions were used to estimate the strength of the Se···π chalcogen bonds. Moreover, molecular electrostatic potential (MEP) surfaces were used to investigate the electron-rich and poor regions of the ion pairs. The quantum theory of atoms-in-molecules (QTAIM) and the noncovalent interaction (NCI) plot methods based on the topology of the electron density were used and combined to characterize the ChBs. The investigation reported herein disclosed that the formation of symmetrical dimers can be broken by the introduction of a stronger π-acceptor and, consequently, forming stronger Se···π contacts with selenodiazolium cations.

A series of phenylsilsesquioxane-benzoate heptacopper complexes 1–3 were synthesized and characterized by X-ray crystallography. Two parallel routes of toluene spontaneous oxidation (into benzyl alcohol and benzoate) assisted the formation of the cagelike structure 1. A unique multi-ligation of copper ions (from (i) silsesquioxane, (ii) benzoate, (iii) benzyl alcohol, (iv) pyridine, (v) dimethyl-formamide and (vi) water ligands) was found in 1. Directed self-assembly using benzoic acid as a reactant afforded complexes 2–3 with the same main structural features as for 1, namely heptanuclear core coordinated by (i) two distorted pentameric cyclic silsesquioxane and (ii) four benzoate ligands, but featuring other solvate surroundings. Complex 3 was evaluated as a catalyst for the oxidation of alkanes to alkyl hydroperoxides and alcohols to ketones with hydrogen peroxide and tert-butyl hydroperoxide, respectively, at 50 °C in acetonitrile. The maximum yield of cyclohexane oxidation products as high as 32% was attained. The oxidation reaction results in a mixture of cyclohexyl hydroperoxide, cyclohexanol, and cyclohexanone. Upon the addition of triphenylphosphine, the cyclohexyl hydroperoxide is completely converted to cyclohexanol. The specific regio- and chemoselectivity in the oxidation of n-heptane and methylcyclohexane, respectively, indicate the involvement of of hydroxyl radicals. Complex 3 exhibits a high activity in the oxidation of alcohols.

A practical method for the synthesis of 2-selenoxo-1,2,3,4-tetrahydro-4-quinazolinone was reported. The latter compounds were found to undergo facile oxidation with H2O2 into corresponding diselenides. Novel organoselenium derivatives were characterized by the 1H, 77Se, and 13C NMR spectroscopies, high-resolution electrospray ionization mass spectrometry, IR, elemental analyses (C, H, N), and X-ray diffraction analysis for several of them. Novel heterocycles exhibited multiple remarkable chalcogen bonding (ChB) interactions in the solid state, which were studied theoretically.