knowledge. However, this compound was characterized by chemical analysis, vibrational spectroscopy and X-ray powder photography by Gantar & Rahten (1986), who determined the unit-cell parameters and the space group. We now describe the synthesis, single crystalstructure and Hirshfeldsurfaceanalysis of the title compound, (I), at room temperature.
4a-hydroxy-4,4,7,11b-tetramethyl-1,2,3,4,4a,5,6,6a,7,11,11a,11b-dodecahydrophen- anthro[3,2-b]furan-5-yl cinnamate], a natural diterpene known as pulcherrin J, was isolated from stem barks of medicinally important Caesalpinia pulcherrima (L.). The crystalstructure of pulcherrin J shows it to be composed of a central core of three trans-fused cyclohexane rings and a near planar five-membered furan ring, along with an axially oriented cinnamate moiety and an hydroxy substituent attached at positions 4a and 5 of the steroid ring system, respectively. The absolute structure was established with the use of Cu K radiation. In the crystal, molecules are linked by O—H O hydrogen bonds to generate  C(8) chains. Hirshfeldsurfaceanalysis indicates that the most significant contacts in packing are H H (67.5%), followed by C H (19.6%) and H O (12.9%).
Pyrimidine and aminopyrimidine derivatives have useful applications in many fields, for example as pesticides and pharmaceutical agents (Condon et al., 1993), while imazo- sulfuron, ethirmol and mepanipyrim have been commercia- lized as agrochemicals (Maeno et al., 1990). Pyrimidine derivatives have also been developed as antiviral agents, such as AZT, which is the most widely used anti-AIDS drug (Gilchrist, 1997). Hydrogen bonding plays a vital role in molecular recognition. It is significant to know the types of hydrogen bonds present to design new materials with highly specific features. Supramolecular chemistry plays a pivotal role in many biological systems and is involved in artificial systems. It refers to the specific relation between two or more molecules through non-covalent interactions such as hydrogen bonding, hydrophobic forces, van der Waals forces and – interactions. The origin of supramolecular architectures is correlated to the positions and properties of the active groups in molecules (Desiraju, 1989; Steiner, 2002). As part of our recent studies in this field, the synthesis, crystalstructure and Hirshfeldsurfaceanalysis of the title salt have been under- taken and are presented herein.
Carboxylates are employed in the synthesis of new transition- metal complexes because they can stabilize them and addi- tionally display different coordination modes such as mono- dendate, bidendate, bridging (syn–syn, syn–anti or anti–anti mode) and ionic. Copper(II) carboxylates have been used as single precursors for the preparation of copper(II) oxide nanoparticles (Karthik & Qadir, 2019). Copper(II) complexes containing ethylenediamine derivatives and carboxylate have shown antibacterial activity against pathogenic bacteria (Kumar et al., 2013). It has been reported that some copper(II) carboxylate complexes involving nitrogen donor ligands exhibit carbonic anhydrase inhibitory activity (Dilek et al., 2017). Ethylenediamine has good coordination and chelating ability, forming five-membered ring compounds with metal centers. Generally, these metallacycles display a twist confor- mation. Copper can take part in different biological processes. Thus, copper shows an important role in electron transfer, oxidation, and dioxygen transport (Mirica et al., 2004; Rosenzweig et al., 2006). In this paper, we report the synthesis, single crystalstructure determination and Hirshfeldsurfaceanalysis of a copper(II) complex containing ethylenediamine and 2-nitrobenzoate.
acids. There are seven known families of serotonin receptors which are tryptamine derivatives, and all of them are neuro- transmitters. Hallucinogens all have a high affinity for certain serotonin receptor subtypes and the relative hallucinogenic potencies of various drugs can be gauged by their affinities for these receptors (Glennon et al., 1984; Nichols & Sanders-Bush, 2001; Johnson et al., 1987; Krebs-Thomson et al., 1998). The structures of many hallucinogens are similar to serotonin and have a tryptamine core. Indole analogues, especially of tryp- tamine derivatives, have been found to be polyamine site antagonists at the N-methyldaspartate receptor (Worthen et al., 2001). Indole and its derivatives are secondary metabolites that are present in most plants (such as unripe bananas, broccoli and cloves), almost all flower oils (jasmine and orange blossoms) and coal tar (Waseem & Mark, 2005; Lee et al., 2003). In the pharmaceutical field, it has been discovered that it has antimicrobial and anti-inflammatory properties (Mohammad & Moutaery, 2005). The title compound, namely 2-(1H-indol-3-yl)ethanaminium acetate hemihydrate, was synthesized and its crystalstructure and Hirshfeldsurfaceanalysis are reported herein.
Schiff bases are nitrogen-containing compounds that were first obtained by the condensation reactions of aromatic amines and aldehydes (Schiff, 1864). A wide range of these compounds, with the general formula RHC NR1 (R and R1 can be alkyl, aryl, cycloalkyl or heterocyclic groups) have been synthesized. They are of great importance in the field of coordination chemistry as they are able to form stable complexes with many metal ions (Souza et al., 1985). The chemical and biological significance of Schiff bases can be attributed to the presence of a lone electron pair in the sp 2 - hybridized orbital of the nitrogen atom of the azomethine group (Singh et al., 1975). These compounds are used in the fields of organic synthesis, chemical catalysis, medicine and pharmacy as well as other new technologies (Tanaka et al., 2010). Schiff bases are also used as probes in investigating the structure of DNA (Tiwari et al., 2011) and have gained special attention in pharmacophore research and in the development of several bioactive lead molecules (Muralisankar et al., 2016). They also exhibit photochromic and thermochromic proper- ties and have been used in information storage, electronic display systems, optical switching devices, and ophthalmic glasses (Amimoto & Kawato, 2005). Herein, we report on the crystalstructure, the Hirshfeldsurfaceanalysis and the mol- ecular orbital analysis of the title compound, (E)-4-bromo-N 0 - (2,3-dichlorobenzylidene)benzohydrazide.
Hirshfeldsurfaceanalysis was used to investigate the presence of hydrogen bonds and intermolecular interactions in the crystalstructure and two-dimensional fingerprint plots were calculated using CrystalExplorer (Turner et al., 2017). The molecular Hirshfeld surfaces were performed using a standard (high) surface resolution with the three-dimensional d norm
which are based on molecular recognition processes (Rodrı´- guez-Cuamatzi et al., 2005; Madura et al., 2014; Herna´ndez- Paredes et al., 2015; Campos-Gaxiola et al., 2017; Pedireddi & Lekshmi, 2004; Vega et al., 2010; TalwelkarShimpi et al., 2016). As part of our ongoing studies in this area, we report herein on the molecular and crystal structures of 3-cyanophenylboronic acid, I. In addition, a Hirshfeldsurfaceanalysis was performed to visualize and quantify the intermolecular interactions in the crystalstructure of compound (I).
dimensional Hirshfeldsurface plotted over electrostatic potentials in the range 0.1028 to 0.1158 a.u. is shown in Fig. 6. The hydrogen-bond donors and acceptors are showed as blue and red regions around the atoms corresponding to positive and negative potentials, respectively.
The molecular structure of the title salt is shown in Fig. 1. Protonation on the N-atom site of the pyridine ring, atom N11, is confirmed by the elongated C—N bond distances [C11— N11 = 1.341 (8) A ˚ and C15—N11 = 1.357 (9) A˚] and the enlarged C11—N11—C15 bond angle of 122.3 (6) . The
metric distribution of points in the fingerprint plot delineated into S H/H S contacts for (II) in Fig. 8c is the result of the orientation of the cyclohexane rings with respect to the crys- tallographic mirror plane. The upper region, corresponding to donor H S contacts, contributes 4.7% to the surface cf. 6.5% in the lower region, corresponding to S H acceptor contacts. The similarity in the molecular packing of (I) and (II) is reflected in the similarity in the physiochemical data collated in Table 5 and calculated in Crystal Explorer (Wolff et al., 2012) and PLATON (Spek, 2009). While it is noted the values are very close for (I) and (II) (Table 5), the volume of the molecule in (I) is slightly greater than that in (II), as is the surface area. However, the molecule in (II) is marginally more globular and reflecting the lack of directional interactions between molecules, allowing a closer approach, the density is greater than in (I). Nevertheless, the packing efficiency is marginally greater in (I), probably reflecting the lack of symmetry in the molecule cf. (I).
under constant stirring for one h. The resulting solution was filtered to remove any undissolved solid. The filtrate was allowed to slowly evaporate at room temperature. After two weeks, colourless block-shaped crystals of the title salt (I) suitable for X-ray analysis were obtained.
(6) graph-set motif. The chains are further linked into a three- dimensional network by C—H interactions. A Hirshfeldsurfaceanalysis indicates that the most important contributions to the crystal packing are from C H (33.2%), H H (27.7%), Br H/H Br (14.2%) and O H/H O (13.6%) interactions. The title compound has also been characterized by frontier molecular orbital analysis.
crystal, molecules are linked by pairs of weak C—H O hydrogen bonds, forming inversion dimers. Hirshfeldsurfaceanalysis and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H H (77.5%), H C/C H (16%), H O/O H (3.1%) and H N/N H (1.7%) interactions.
therefore the O O contacts are electrostatically repulsive. Fig. 9 shows the voids (Wolff et al., 2012) in the crystalstructure of (I). These are based on the sum of spherical atomic electron densities at the appropriate nuclear positions (procrystal electron density). The crystal-void calculation (results under 0.002 a.u. isovalue) shows the void volume of title compound to be of the order of 469.14 A ˚ 3 and surface area in the order of 1334.82 A ˚ 2 . With the porosity, the calcu- lated void volume of (I) is 17%. There are no large cavities. We note that the electron-density isosurfaces are not completely closed around the components, but are open at those locations where interspecies approaches are found, e.g. N—H O.
Geometry . All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Nicotinamide (NA) is a derivative of nicotinic acid, also called niacin. A deficiency in this vitamin leads to loss of copper from the body, giving rise to a condition known as pellagra disease. Victims of pellagra show unusually high serum and urinary copper levels (Krishnamachari, 1974). The crystalstructure of NA was first determined in 1954 (Wright & King, 1954). The NA ring is the reactive part of nicotinamide adenine dinu- cleotide (NAD) and its phosphate (NADP), which are the major electron carriers in many biological oxidation–reduc- tion reactions (You et al., 1978). Another nicotinic acid deri- vative, N,N-diethylnicotinamide (DENA), is an important respiratory stimulant (Bigoli et al., 1972). Transition-metal complexes with ligands of biochemical interest, such as imidazole and some N-protected amino acids, often show interesting physical and/or chemical properties, which lead to applications in biological systems (Antolini et al., 1982). There have been many reports of the crystal structures of metal complexes with benzoic acid derivatives, which are of interest because of the number of different coordination modes exhibited by the carboxylic acid groups. These include Co and Cd complexes with 4-aminobenzoic acid (Chen & Chen, 2002; Amiraslanov et al., 1979; Hauptmann et al., 2000), Co complexes with benzoic acid (Catterick et al., 1974), 4-nitro-
The intermolecular contacts in the crystal of (I) were further analysed using an enrichment ratio (ER) descriptor, which is derived from the analysis of the Hirshfeldsurface (Jelsch et al., 2014). The ER relates the propensity of pair of chemical species to form a specific interaction in a crystal. The enrichment ratio, ER(X, Y), for a pair of elements (X, Y) is defined as the ratio between proportion of actual contacts in the crystal to the theoretical proportion of random contacts. This ratio is greater than unity for a pair of elements having a high likelihood to form contacts in a crystal, while it is less than one for a pair which tends to avoid contacts with each other. A listing of ER values for (I) is given in Table 4. The enrichment ratios greater than unity for the atom pairs (O, H)
set (Petersson et al., 1988), as implemented in Gaussian16 (Frisch et al., 2016), the gas-phase geometry-optimized struc- ture of (I) was calculated. As confirmed through a frequency analysis with zero imaginary frequency, the local minimum structure in the gas-phase was located in this study. The experimental and theoretical structures are superimposed (Macrae et al., 2006) in Fig. 2. The analysis shows that there are only minor differences between the molecules with the r.m.s. deviation between the conformations being only 0.015 A ˚ . The derived interatomic data for the geometry-optimized structure are included in Table 1 from which it can be seen there is a close correlation between the experimental and calculated geometries.
Two symmetry-related tapes are linked by a helical chain of hydrogen-bonded water molecules via water-O—H N(pyridyl) hydrogen bonds. The resulting aggregate is parallel to the b-axis direction. Links between these, via methylene- C—H O(water) and methylene-C—H (pyridyl) interactions, give rise to a layer parallel to (101); the layers stack without directional interactions between them. The analysis of the Hirshfeld surfaces point to the importance of the specified hydrogen-bonding interactions, and to the significant influence of the water molecule of crystallization upon the molecular packing. The analysis also indicates the contribution of methylene-C—H O(carbonyl) and pyridyl-C— H C(carbonyl) contacts to the stability of the inter-layer region. The calculated interaction energies are consistent with importance of significant electrostatic attractions in the crystal.