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Perchlorate compounds are well-known for their explosive and hazardous nature. Considering previously reported perchlorate crystals of salen-type manganese (III) complexes, our study aimed to identify the specific molecular/crystal structure responsible for their explosive properties. Employing deep learning, we conducted an analysis of the Hirschfeld surface for salen-type metal complexes within a crystal structure database. The results indicate that the salen-type complex site lacks distinctive structural features, attributing its explosive potential to the chemical bonding of the perchlorate ion and the surrounding intermolecular interactions.

The title copper(II) complex, [Cu(C18H19N3O3)(C3H4N2)], consists of a tridentate ligand synthesized from L-leucine and azobenzene-salicylaldehyde. One imidazole molecule is additionally coordinated to the copper(II) ion in the equatorial plane. The crystal structure features N—H...O hydrogen bonds. A Hirshfeld surface analysis indicates that the most important contributions to the packing are from H...H (52.0%) and C...H/H...C (17.9%) contacts.

The title copper(II) complex, [Cu(C16H13NO4)(C3H4N2)], consists of a tridentate ligand synthesized from L-tyrosine and salicylaldehyde. One imidazole molecule is additionally coordinating to the copper(II) ion. The crystal structure features N—H...O, O—H...O and C—H...O hydrogen bonds. The Hirshfeld surface analysis indicates that the most important contributions to the packing are from H...H (37.9%), C...H (28.2%) and O...H/H...O (21.2%) contacts.

The molecular structure of the title compound, [Cu(C12H13N2O3)(H2O)2]·[Cu(C12H13N2O3)(H2O)], consists of two different molecules in the asymmetric unit. Both of the structures consist of a tridentate ligand synthesized from l-valine and salicylaldehyde, and one water molecule or two water molecules coordinating to CuII. They have a square-planar (molecule 1) or a square-pyramidal (molecule 2) coordination geometry. In the crystal, the molecules form intra- and intermolecular O—H...O hydrogen bonds involving the coordinated water molecules and other sites. A Hirshfeld surface analysis indicated that the most important contributions to the packing are from H...H [52.9% (molecule 1) and 51.1% (molecule 2)] and H...O/ O...H [21.2% (molecule 1) and 25.8% (molecule 2)] contacts. In addition, an electrostatic potential map was also obtained from DFT calculations to support the discussion of the intermolecular interactions.

Since chemistry, materials science, and crystallography deal with three-dimensional structures, they use mathematics such as geometry and symmetry. In recent years, the application of topology and mathematics to material design has yielded remarkable results. It can also be seen that differential geometry has been applied to various fields of chemistry for a relatively long time. There is also the possibility of using new mathematics, such as the crystal structure database, which represents big data, for computational chemistry (Hirshfeld surface analysis). On the other hand, group theory (space group and point group) is useful for crystal structures, including determining their electronic properties and the symmetries of molecules with relatively high symmetry. However, these strengths are not exhibited in the low-symmetry molecules that are actually handled. A new use of mathematics for chemical research is required that is suitable for the age when computational chemistry and artificial intelligence can be used.

The compound, {6,6′-dimethoxy-2,2′-[(4-azaheptane-1,7-diyl)bis(nitrilomethanylidyne)]diphenolato}zinc(II) methanol monosolvate, [Zn(C22H27N3O4)]·CH3OH, at 298 K crystallizes in the orthorhombic space group Pna21. The Zn atom is coordinated by a pentadentate Schiff base ligand in a distorted trigonal–bipyramidal N3O2 geometry. The equatorial plane is formed by the two phenolic O and one amine N atom. The axial positions are occupied by two amine N atoms. The distorted bipyramidal geometry is also supported by the trigonality index (τ), which is found to be 0.85 for the molecule. In the crystal, methanol solvent molecule is connected to the complex molecule by an O—H...O hydrogen bond and the complex molecules are connected by weak supramolecular interactions, so achiral molecules generate a chiral crystal. The Hirshfeld surface analysis suggests that H...H contacts account for the largest percentage of all interactions.

In the title complex, [Sm(NO3)3(C30H28N2O4)], the Sm atom is surrounded by ten O atoms. The (S,S)-2,2′-{[(1,2-diphenylethane-1,2-diyl)bis[(azaniumylylidene)methanylylidene]}bis(6-methoxyphenolate) ligand, obtained from o-vanillin and (1S,2S)-(−)-1,2-diphenylethylenediamine, exhibits a slightly distorted planar arrangement of the four coordinated O atoms. In the crystal, the complex shows intramolecular N—H...O hydrogen bonds and weak intermolecular C—H...O hydrogen bonds. The Hirshfeld surface analysis indicates that the most important contributions to the packing are from H...H (33.5%), O...H (34.1%) and C...H (21.7%) contacts.

In the title complex molecule, [Cu(C11H11NO4)(CH4O)(H2O)], the Cu atom is coordinated in a distorted square-pyramidal geometry by a tridentate ligand synthesized from l-threonine and salicylaldehyde, one methanol molecule and one water molecule. In the crystal, the molecules show intra- and intermolecular O—H...O hydrogen bonds. The Hirshfeld surface analysis indicates that the most important contributions to the packing are H...H (49.4%) and H...O/O...H (31.3%) contacts.

Crystals of the title compound, (C5H8N3)3[VO2(C2O4)2]·2.5H2O, a mononuclear VV complex, were obtained by slow evaporation at room temperature of an aqueous solution containing vanadium pentoxide, oxalic acid and 2,6-diaminopyridine. The asymmetric unit contains one bis(oxalato)dioxovanadate(V) anionic complex, three 2,6-diaminopyridinium cations and two and a half uncoordinated water molecules. The mononuclear vanadium(V) anions are connected to the organic cations and water molecules through a strong N—H...O and O—H...O hydrogen-bond network, consolidated by π–π stacking interactions, to form a three-dimensional structure.

In each of the compounds 1-[(1,3-benzodioxol-5-yl)methyl]-4-(3-fluorobenzoyl)piperazine, C19H19FN2O3 (I), 1-[(1,3-benzodioxol-5-yl)methyl]-4-(2,6-difluorobenzoyl)piperazine, C19H18F2N2O3 (II), and 1-[(1,3-benzodioxol-5-yl)methyl]-4-(2,4-dichlorobenzoyl)piperazine, C19H19Cl2N2O3 (III), the piperazine rings adopt a chair conformation with the (1,3-benzodioxol-5-yl)methyl substituent occupying an equatorial site: the five-membered rings are all slightly folded across the O...O line leading to envelope conformations. The dihedral angle between the planar amidic fragment and the haloaryl ring is 62.97 (5)° in (I) but 77.72 (12)° and 75.50 (5)° in (II) and (III), respectively. Despite their similarity in constitution and conformation, the supramolecular interactions in (I)–(III) differ: in (I), a combination of C—H...O and C—H...π(arene) hydrogen bonds links the molecules into a three-dimensional framework structure, but there are no hydrogen bonds of any sort in either (II) or (III), although the structure of (III) contains a short Cl...Cl contact between inversion-related pairs of molecules.

Co-crystallization of racemic 1-cyclohexyl-1-phenyl-3-(piperidin-1-yl)propan-1-ol (trihexyphenidyl) with 3,5-dinitrobenzoic acid gives a simple 1:1 salt, namely 1-(3-cyclohexyl-3-hydroxy-3-phenylpropyl)piperidin-1-ium 3,5-dinitrobenzoate, C20H32NO+·C7H3N2O6−, (I), whereas a similar co-crystallization using (Z)-3-(2-chloro-9H-thioxanthen-9-yl)-N,N-dimethylpropan-1-amine (chlorprothixene) gives a 1:2 acid salt, namely (Z)-3-(2-chloro-9H-thioxanthen-9-yl)-N,N-dimethylpropan-1-aminium hydrogen bis(3,5-dinitrobenzoate), C18H19ClNS+·[H(C7H3N2O6)2]−, (II), the anion of which contains a very short O—H...O hydrogen bond, with dimensions O—H = 1.04 (3) Å, H...O = 1.41 (3) Å, O...O = 2.4197 (15) Å and O—H...O = 161 (3)°. In the cation of (I), the cyclohexyl and piperidyl rings both adopt chair conformations, whereas in the cation of (II), the central heterocyclic ring adopts a boat conformation, so that the dihedral angle between the two aryl rings is 41.56 (4)°. A combination of O—H...O, N—H...O and C—H...O hydrogen bonds links the ions of (I) into a complex chain of rings, and these chains are linked into sheets by π–π stacking interactions between inversion-related pairs of anions. In compound (II), a different combination of O—H...O, N—H...O and C—H...O hydrogen bonds links the ions into sheets. Comparisons are made with some related structures.

In 1-(2-iodobenzoyl)-4-(pyrimidin-2-yl)piperazine, C15H15IN4O, the central piperazine ring adopts an almost perfect chair conformation with the pyrimidine substituent in an equatorial site. The planar amide unit makes a dihedral angle of 80.44 (7)° with the phenyl ring. A combination of C—H...O and C—H...π(arene) hydrogen bonds links the molecules into a complex three-dimensional network structure, augmented by a π–π stacking interaction and an I...N halogen bond, all involving different pairs of inversion-related molecules. Comparisons are made with the structures of a number of related compounds.

The title azo compound, C16H16N4, was synthesized from 2,6-dimethylaniline. The diazenyl group adopts a trans (E) conformation, with an N=N bond length of 1.265 (4) Å. The pyrazole ring is approximately planar. In the crystal, zigzag chains along the b-axis direction with a C(3) is graph-set motif are formed by N—H...N hydrogen bonds involving the pyrazole moiety.

The title compound, C10H10O4, was synthesized from tetramethyl-1,4-benzoquinone. In the crystal, the almost planar molecule (r.m.s. deviation = 0.024 Å) forms intramolecular hydrogen bonds between the aldehyde and hydroxy groups and exhibits C2v symmetry. This achiral molecule crystallizes in the chiral space group P21 with intermolecular O—H...O and C—H...O hydrogen bonding and C—H...π and C=O...π interactions stabilizing the crystal packing.

The structure of the complex salt, cis-[Cr(NCS)2(cyclam)]2[Cr2O7]·H2O (cyclam = 1,4,8,11-tetraazacyclotetradecane, C10H24N4), has been determined from synchrotron data. The asymmetric unit comprises of one [Cr(NCS)2(cyclam)]+ cation, one half of a Cr2O72− anion (completed by inversion symmetry) and one half of a water molecule (completed by twofold rotation symmetry). The CrIII ion is coordinated by the four cyclam N atoms and by two N atoms of cis-arranged thiocyanate anions, displaying a distorted octahedral coordination sphere. The Cr—N(cyclam) bond lengths are in the range 2.080 (2) to 2.097 (2) Å while the average Cr—N(NCS) bond length is 1.985 (4) Å. The macrocyclic cyclam moiety adopts the cis-V conformation. The bridging O atom of the dichromate anion is disordered around an inversion centre, leading to a bending of the Cr—O—Cr bridging angle [157.7 (3)°]; the anion has a staggered conformation. The crystal structure is stabilized by intermolecular hydrogen bonds involving the cyclam N—H groups and water O—H groups as donor groups, and the O atoms of the Cr2O72− anion and water molecules as acceptor groups, giving rise to a three-dimensional network.

The title compound, C19H12N2O3, obtained as an intermediate in the synthesis of a pyrrole derivative, is composed of a five-membered heterocycle with substituted groups via double or triple bonds as well as single bonds, without an asymmetric carbon atom. An intramolecular O—H...O link occurs. In the crystal, O—H...N hydrogen bonds link the molecules.

The title indole derivative, C11H11NO2, was synthesized from 1-methyl-1H-indole-3-carboxylic acid and methanol. The molecule is planar as it is situated on a mirror plane present in the space group Pbcm. In the crystal, molecules form three kinds of intermolecular C—H...O hydrogen bonds, resulting in a sheet structure in the ab plane. Parallel sheets interact by C—H...π stacking, stabilizing the crystal packing.

Single crystals of two achiral and planar heterocyclic compounds, C9H8H3O(CA1) and C8H5NO2 (CA4), recrystallized from ethanol, were characterized by single crystal X-ray analysis, respectively, and chiral crystallization was observed only for CA1 as P212121 (# 19), whereas it was not observed for CA4P21/c (# 14). In CA1, as a monohydrate, the hydrogen bonds were pronounced around the water of crystallization (O4), and the planar cyclic sites were arranged in parallel to slightly tilted positions. On the other hand, an anhydride CA4 formed a dimer by hydrogen bonds between adjacent molecules in the crystal, which were aggregated by van der Waals forces and placed in parallel planar cyclic sites.

The title bromide salt, [Cr{CO(NH2)2}6](Cr2O7)Br·H2O, is isotypic to the corresponding chloride salt. Within the complex cation, the CrIII atom is coordinated by six O atoms of six urea ligands, displaying a slightly distorted octahedral coordination environment. The Cr—O bond lengths involving the urea ligands are in the range 1.9534 (13)–1.9776 (12) Å. The Cr2O72− anion has a nearly staggered conformation, with a bridging angle of 130.26 (10)°. The individual components are arranged in rows extending parallel to [100]. The Br− anion links the complex cation, as well as the solvent water molecule, through N—H...Br and O—H...Br hydrogen-bonding interactions. The supramolecular architecture also includes N—H...O and O—H...O hydrogen bonding between urea N—H and water O—H donor groups and the O atoms of the Cr2O72− anion as acceptor atoms, leading to a three-dimensional network structure.

The title salt, K+·C13H9O2−·H2O, was synthesized from 5-bromosalicylaldehyde and a phenylboronic acid derivative using the Suzuki–Miyaura cross-coupling reaction (Miyaura & Suzuki, 1979). In addition to the intermolecular interactions between the charged species, two O—H...O hydrogen bonds involving the isolated water molecules further stabilize the crystal packing of the title salt leading to the formation of a three-dimensional framework structure.

The title compound, C16H16N2O4·3H2O, was synthesized from (1R,2R)-1,2-bis(2-hydroxyphenyl)ethylenediamine and terephthalaldehydic acid. The compound crystallizes from water as a double zwitterion with protonated amine groups and deprotonated carboxylate groups. The dihedral angle formed by the aromatic rings is 3.86 (11)°. In the crystal, N—H...O and O—H...O hydrogen bonds link molecules into a three-dimensional network.

The title chiral photochromic Schiff base compound, C21H18BrN3O, was synthesized from (R)-(+)-1-(4-bromophenyl)ethylamine and the salicylaldehyde of an azobenzene derivative. The molecule corresponds to the phenol–imine tautomer, the C=N and N—C bond distances being 1.285 (3) and 1.470 (3) Å, respectively. The diazenyl group adopts a trans form, with an N=N distance of 1.256 (3) Å. The hydroxy group is involved in intramolecular O—H...N hydrogen bonding. In the crystal, C—H...π interactions consolidate the crystal packing of one-dimensional chains, which exhibits short intermolecular Br...C contacts of 3.400 (3) Å.

The title copper(II) complex, [Cu(C18H19N3O3)(C3H4N2)], consists of a tridentate ligand synthesized from l-leucine and azobenzene-salicylaldehyde. One imidazole molecule is additionally coordinated to the copper(II) ion in the equatorial plane. The crystal structure features N--H...O hydrogen bonds. A Hirshfeld surface analysis indicates that the most important contributions to the packing are from H...H (52.0%) and C...H/H...C (17.9%) contacts. [ABSTRACT FROM AUTHOR]

The title copper(II) complex, [Cu(C16H13NO4)(C3H4N2)], consists of a tridentate ligand synthesized from l-tyrosine and salicylaldehyde. One imidazole molecule is additionally coordinating to the copper(II) ion. The crystal structure features N--H--O, O--H--O and C--H--O hydrogen bonds. The Hirshfeld surface analysis indicates that the most important contributions to the packing are from H--H (37.9%), C--H (28.2%) and O--H/H--O (21.2%) contacts. [ABSTRACT FROM AUTHOR]

The title copper(II) complex, [Cu(C16H13NO4)(C3H4N2)], consists of a tridentate ligand synthesized from L-tyrosine and salicylaldehyde. One imidazole molecule is additionally coordinating to the copper(II) ion. The crystal structure features N--H⋯O, O--H⋯O and C--H⋯O hydrogen bonds. The Hirshfeld surface analysis indicates that the most important contributions to the packing are from H⋯H (37.9%), C⋯H (28.2%) and O⋯H/H⋯O (21.2%) contacts. [ABSTRACT FROM AUTHOR]

The molecular structure of the title compound, [Cu(C12H13N2O3)(H2O)2]·-[Cu(C12H13N2O3)(H2O)], consists of two different molecules in the asymmetric unit. Both of the structures consist of a tridentate ligand synthesized from l-valine and salicylaldehyde, and one water molecule or two water molecules coordinating to CuII. They have a square-planar (molecule 1) or a squarepyramidal (molecule 2) coordination geometry. In the crystal, the molecules form intra- and intermolecular O--H· · ·O hydrogen bonds involving the coordinated water molecules and other sites. A Hirshfeld surface analysis indicated that the most important contributions to the packing are from H· · ·H [52.9% (molecule 1) and 51.1% (molecule 2)] and H· · ·O/O· · ·H [21.2% (molecule 1) and 25.8% (molecule 2)] contacts. In addition, an electrostatic potential map was also obtained from DFT calculations to support the discussion of the intermolecular interactions. [ABSTRACT FROM AUTHOR]

In the title complex, [Sm(NO3)3(C30H28N2O4)], the Sm atom is surrounded by ten O atoms. The (S,S)-2,2′-{[(1,2-di­phenyl­ethane-1,2-di­yl)bis­[(aza­niumylyl­idene)methanylyl­idene]}bis­(6-meth­oxy­phenolate) ligand, obtained from o-vanillin and (1S,2S)-(−)-1,2-di­phenyl­ethyl­enedi­amine, exhibits a slightly distorted planar arrangement of the four coordinated O atoms. In the crystal, the complex shows intra­molecular N—H...O hydrogen bonds and weak inter­molecular C—H...O hydrogen bonds. The Hirshfeld surface analysis indicates that the most important contributions to the packing are from H...H (33.5%), O...H (34.1%) and C...H (21.7%) contacts. [ABSTRACT FROM AUTHOR]

In the title complex mol­ecule, [Cu(C11H11NO4)(CH4O)(H2O)], the Cu atom is coordinated in a distorted square-pyramidal geometry by a tridentate ligand synthesized from L-threonine and salicyl­aldehyde, one methanol mol­ecule and one water mol­ecule. In the crystal, the mol­ecules show intra- and inter­molecular O—H...O hydrogen bonds. The Hirshfeld surface analysis indicates that the most important contributions to the packing are H...H (49.4%) and H...O/O...H (31.3%) contacts. [ABSTRACT FROM AUTHOR]