Independent Molecules Research Articles

Synthesis, Crystal Structure, Computational Investigation of Vanillin Azine Derivative as Potent Blocker of the N‐Terminal Ras‐Binding Domain (RBD) in Human a‐Raf Kinase

AbstractVanillin is the main component of natural vanilla extract and is responsible for its flavoring properties. Besides its well‐known applications as an additive in food and cosmetics. In this, we have synthesized a new vanillin derivative. Its structure was characterized by IR, MS, NMR and confirmed by single‐crystal X‐ray analysis. The asymmetric unit of the title molecule consists of two independent half molecules, each having crystallographically imposed centrosymmetry. Reticular layers approximately parallel to the bc plane are generated from one molecule through O−H⋅⋅⋅N hydrogen bonds. The layers are linked by the second molecule through O−H⋅⋅⋅O hydrogen bonds to form a 3‐D network structure. We carried out density functional investigations to understand the compound‘s molecular reactivity and chemical stability. Frontier molecular orbital (FMO) analysis, global reactivity, and Fukui parameters were calculated at the B3LYP/6‐31+G(d,p) method. In 20 % to 30 % of human malignancies, RAS genes are activated ontogenetically by point mutations. New strategies to block this oncogenic protein are needed since it has proven difficult to create efficient RAS inhibitors. The above‐titled compound shows better structural activity relationship studies against Ras‐binding domine, based on this molecular docking simulation as well as the drug‐likeness analysis carried out for our newly synthesized compound.

A hard sphere model for single-file water transport across biological membranes.

We use Gürsey's statistical mechanics of a one-dimensional fluid to find a formula for the ratio in the transport of hard spheres across a membrane through a narrow channel that can accommodate molecular movement only in single file. is the membrane permeability for osmotic flow and the permeability for exchange across the membrane in the absence of osmotic flow. The deviation of the ratio from unity indicates the degree of cooperative transport relative to ordinary diffusion of independent molecules. In contrast to an early idea that must be equal to the number of molecules in the channel, regardless of the physical nature of the interactions among the molecules, we find a functional dependence on the fractional occupancy of the length of the channel by the hard spheres. We also attempt a random walk calculation for individually, which gives a result for as well when combined with the ratio.

Synthesis, crystal structure and Hirshfeld analysis of N-ethyl-2-{3-methyl-2-[(2Z)-pent-2-en-1-yl]cyclopent-2-en-1-ylidene}hydrazinecarbothioamide

The title compound (C14H23N3S, common name: cis-jasmone 4-ethylthiosemicarbazone) was synthesized by the equimolar reaction of cis-jasmone and 4-ethylthiosemicarbazide in ethanol facilitated by acid catalysis. There is one crystallographically independent molecule in the asymmetric unit, which shows disorder of the terminal ethyl group of the jasmone carbon chain [site-occupancy ratio = 0.911 (5):0.089 (5)]. The thiosemicarbazone entity [N—N—C(=S)—N] is approximately planar, with the maximum deviation of the mean plane through the N/N/C/S/N atoms being 0.0331 (8) Å, while the maximum deviation of the mean plane through the five-membered ring of the jasmone fragment amounts to −0.0337 (8) Å. The dihedral angle between the two planes is 4.98 (7)°. The molecule is not planar due to this structural feature and the sp 3-hybridized atoms of the jasmone carbon chain. Additionally, one H...N intramolecular interaction is observed, with graph-set motif S(5). In the crystal, the molecules are connected through pairs of H...S interactions with R 2 2(8) and R 2 1(7) graph-set motifs into centrosymmetric dimers. The dimers are further connected by H...N interactions with graph-set motif R 2 2(12), which are related by an inversion centre, forming a mono-periodic hydrogen-bonded ribbon parallel to the b-axis. The crystal structure and the supramolecular assembly of the title compound are compared with four known cis-jasmone thiosemicarbazone derivatives (two crystalline modifications of the non-substituted form, the 4-methyl and the 4-phenyl derivatives). A Hirshfeld surface analysis indicates that the major contributions for the crystal cohesion are from H...H (70.7%), H...S/S...H (13.5%), H...C/C...H (8.8%), and H...N/N...H (6.6%) interfaces (only the disordered atoms with the highest s.o.f. were considered for the evaluation).

Pseudo-Polymorphism in 2-Pyridylmethoxy Cone Derivatives of p-tert-butylcalix[4]arene and p-tert-butylhomooxacalix[n]arenes

This paper investigates pseudo-polymorphism in 2-pyridylmethoxy derivatives of p-tert-butylcalix[4]arene (PyC4), p-tert-butyldihomooxa-calix[4]arenes (PyHOC4), and p-tert-butylhexahomotrioxacalix[3]arenes (PyHO3C3), presenting 11 crystal structures with 15 crystallographically independent molecules. The macrocycle of PyC4 is smaller and less flexible with respect to those of PyHOC4 and PyHO3C3, and in solution, the cone conformation of these three molecules exhibits different point symmetries: C4, Cs, and C3, respectively. A correlation is observed between the macrocycle’s structural rigidity and the number of pseudo-polymorphs formed. The more rigid PyC4 displays a higher number (six) of pseudo-polymorphs compared to PyHOC4 and PyHO3C3, which exhibit a smaller number of crystalline forms (three and two, respectively). The X-ray structures obtained show that the conformation of the macrorings is primarily influenced by the presence of an acetonitrile guest molecule within the cavity, with limited impact from crystal packing and intermolecular co-crystallized solvent molecules. Notably, both calix[4]arene derivatives produce a host–guest complex with acetonitrile, while the most flexible and less aromatic PyHO3C3 does not give crystals with acetonitrile as the guest. Intertwined 1D and 2D solvent channel networks were observed in the PyHOC4-hexane and in the PyHO3C3-H2O-MeOH crystal structures, respectively, while the other pseudopolymorphs of PyHOC4 and PyHO3C3 and all PyC4 crystal forms exhibit closely packed crystal structures without open channels.

A survey of supramolecular association involving the oxide-O atom in the crystals of triorganoamine N-oxide derivatives, RR′R″N(+)O(−)

Abstract Trimethylamine N-oxide, Me3N(+)O(−), is an important molecule in biology and medicine. Herein, a survey of the interactions involving the oxide-O atom in crystals containing derivatives of Me3N(+)O(−), namely RR′R″N(+)O(−), is presented; R,R′, R″ = alkyl and/or aryl. A total of 119 RR′R″N(+)O(−) molecules were analysed for the supramolecular interactions involving the oxide-O atom. Hydrates form the largest class of crystals, comprising over 40 % of the 91 crystals investigated, a value slightly higher than expectation. Over 80 % of molecules had at least one O–H⋯O(−)(oxide) hydrogen bond: 3, 45 and 33 % of all molecules had three, two or one O–H⋯O(−)(oxide) hydrogen bonds, respectively. Further, nearly 15 % of molecules formed at least one N–H⋯O(−)(oxide) hydrogen bond, sometimes operating in concert with O–H⋯O(−)(oxide) hydrogen bonds. The overwhelming majority of molecules featured inter- and/or intra-molecular supporting C–H⋯O(−)(oxide) contacts so that a diverse range of supramolecular interaction patterns is apparent, a situation made more complicated by the appearance of different supramolecular association patterns often observed for independent molecules in crystals with more than one molecule in the crystallographic asymmetric-unit. Of the 6 % of molecules devoid of conventional A–H⋯O(−)(oxide) hydrogen bonds, all formed three or four inter-/intra-molecular C–H⋯O(−)(oxide) contacts usually characterised by at least one short H⋯O(−)(oxide) distance.

Synthesis of a new hydrazone-based schiff base: Spectroscopy, single crystal, DNA binding and theoretical studies

A new thiosemicarbazide-based Schiff base (TSDHB) was synthesized from thiosemicarbazide and 2,3-dihydroxybenzaldehyde. The prepared thiosemicarbazone was characterized by elemental (CHN), FT-IR, 1H and 13C NMR techniques. Furthermore, the molecular structure was probed using the single-crystal X-ray diffraction (SC-XRD) technique, which confirmed the enol tautomeric form with two independent molecules in asymmetric unit. The dissimilarity between the molecular units was determined by molecular overlay plots. The various intermolecular interactions and solid-state assembly stabilization were explored by Hirshfeld surface analysis. Void analysis was executed to examine the mechanical stability of crystalline units. The bioactivity of thiosemicarbazone was probed with the help of its binding capacity with salmon sperm DNA (SS-DNA) by means of the absorption interaction method. Accompanied by biological activity, optoelectronic properties such as nonlinear optical properties of yielded crystal were also explored through the DFT approach at M06/6–311 G (d,p). For this, various kinds of investigations such as frontier molecular orbital (FMO), UV–Vis, global reactivity parameters (GRPs), transition density matrix (TDM), density of states (DOS), natural population analysis (NPA), and natural bond orbital analysis (NBO) were executed at M06 functional. A good agreement was examined between XRD and DFT findings of molecular geometric parameters. Notably, in comparison with urea, TSDHB demonstrated enhanced nonlinear optical properties (linear polarizability=4.766 × 10−23esu and third-order hyperpolarizability=5.939 × 10−35esu). These findings position TSDHB as a promising candidate for DNA binding as well as for photonic materials due to its unique molecular characteristics and enhanced nonlinear optical behavior.

Structure of a novel form of phosphopantetheine adenylyltransferase from Klebsiella pneumoniae at 2.59Å resolution.

Phosphopantetheine adenylyltransferase (EC. 2.7.7.3, PPAT) catalyzes the penultimate step of the multistep reaction in the coenzyme A (CoA) biosynthesis pathway. In this step, an adenylyl group from adenosine triphosphate (ATP) is transferred to 4'-phosphopantetheine (PNS) yielding 3'-dephospho-coenzyme A (dpCoA) and pyrophosphate (PPi). PPAT from strain C3 of Klebsiella pneumoniae (KpPPAT) was cloned, expressed and purified. It was crystallized using 0.1M HEPES buffer and PEG10000 at pH 7.5. The crystals belonged to tetragonal space group P41212 with cell dimensions of a = b = 72.82Å and c = 200.37Å. The structure was determined using the molecular replacement method and refined to values of 0.208 and 0.255 for Rcryst and Rfree factors, respectively. The structure determination showed the presence of three crystallographically independent molecules A, B and C in the asymmetric unit. The molecules A and B are observed in the form of a dimer in the asymmetric unit while molecule C belongs to the second dimer whose partner is related by crystallographic twofold symmetry. The polypeptide chain of KpPPAT folds into a β/α structure. The conformations of the side chains of several residues in the substrate binding site in KpPPAT are significantly different from those reported in other PPATs. As a result, the modes of binding of substrates, phosphopantetheine (PNS) and adenosine triphosphate (ATP) differ considerably. The binding studies using fluorescence spectroscopy indicated a KD value of 3.45 × 10-4M for ATP which is significantly lower than the corresponding values reported for PPAT from other species.

4-Fluoro-2-(phenyl-amino)-benzoic acid.

The title compound, C13H10FNO2, was obtained by the reaction of 2-bromo-4-fluoro-benzoic acid with aniline. There are two independent mol-ecules, A and B, in the asymmetric unit, with slight conformational differences: the dihedral angles between the aromatic rings are 55.63 (5) and 52.65 (5)°. Both mol-ecules feature an intra-molecular N-H⋯O hydrogen bond. In the crystal, the mol-ecules are linked by pairwise O-H⋯O hydrogen bonds to form A-B acid-acid dimers and weak C-H⋯F inter-actions further connect the dimers.

Discovery of indoleninyl-pyrazolo[3,4-b]pyridines as potent chemotherapeutic agents against colorectal cancer cells

A new series of indolenines decorated with pyrazolo[3,4-b]pyridines were designed and synthesized in up to 96% yield from the acid-catalyzed cyclocondensation of 1,3-dialdehydes with 3-aminopyrazoles. X-ray crystallography on a representative derivative, 5n, revealed two close to planar conformations whereby the N-atom of the pyridyl residue was syn or anti to the pyrrole-N atom in the two independent molecules of the asymmetric unit. The computational and DNA binding data suggest that 5n is a strong DNA intercalator with the results in agreement with its potent cytotoxicity against two colorectal cancer cell lines (HCT 116 and HT-29). In contrast to doxorubicin, compounds 5k-o have higher druggability (compliance to more criteria stated in Lipinski’s rule of five and Veber’s rule), higher bioavailability, and better medicinal chemistry properties, indicative of their potential application as chemotherapeutical agents.

Proposed crystal structure of carbadox, C11H10N4O4

A model for the crystal structure of carbadox has been generated and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Carbadox crystallizes in space group P21 (#4) with a = 13.8155(3), b = 21.4662(1), c = 16.3297(3) Å, β = 110.0931(7)°, V = 4548.10(3) Å3, and Z = 16. The crystal structure is characterized by approximately parallel stacking of the eight independent carbadox molecules parallel to the bc-plane. There are two different molecular configurations of the eight carbadox molecules; five are in the lower-energy configuration and three are in a ~10% higher-energy configuration. This arrangement likely achieves the lowest-energy crystalline packing via hydrogen bonding. Hydrogen bonds link the molecules both within and between the planes. Each of the amino groups forms a N–H⋯O hydrogen bond to an oxygen atom of the 1,4-dioxidoquinoxaline ring system of another molecule. The result is four pairs of hydrogen-bonded molecules, which form rings with graph set R2,2(14). Variation in specimen preparation can affect the preferred orientation of particles considerably. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®).

Prop-2-ynyl 3-meth-oxy-4-(prop-2-yn-yloxy)benzoate.

The title compound, C14H12O4, comprises of two crystallographically independent mol-ecules in the asymmetric unit, linked via C-H⋯O inter-actions to form dimeric entities. The allylic groups are twisted out of the phenyl planes with dihedral angles varying between 7.92 (13) and 25.42 (8)°. In the crystal, the packing follows a zigzag pattern along the c-axis direction. The absolute configuration of the sample could not be determined reliably.

Crystal structure of anthraquinone-2-carboxylic acid, C15H8O4

The crystal structure of anthraquinone-2-carboxylic acid has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Anthraquinone-2-carboxylic acid crystallizes in space group P-1 (#2) with a = 3.7942(2), b = 13.266(5), c = 22.835(15) Å, α = 73.355(30), β = 89.486(6), γ = 86.061(1)°, V = 1098.50(7) Å3, and Z = 4. The crystal structure contains two independent molecules of anthraquinone-2-carboxylic acid. Although the expected hydrogen-bonded dimers are present, the dimers are not centrosymmetric. The dimer contains one molecule of each planar low-energy conformation. The crystal structure consists of a herringbone array of centrosymmetric pairs of molecules parallel to the bc-plane. The molecules stack along the short a-axis. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

Epiregulin: A new prognostic molecule in non-Hodgkin lymphoma.

Epiregulin is a molecule that plays a role in cell proliferation, tumor development, inflammation, and angiogenesis in malignant diseases. Our study aims to reveal, for the first time, the predictive value of this molecule in non-Hodgkin lymphoma (NHL) and its association with disease stage, cell type, and extranodal involvement. The study is an observational case-control trial involving 60 newly diagnosed NHL patients and 60 healthy individuals (control group) between 18 and 75years old. Demographic characteristics of all volunteers, stages of patients' illnesses and lymphoma cell types, hemogram, biochemistry tests, beta 2-microglobulin, C-reactive protein (CRP), and epiregulin levels were measured and statistically evaluated. Epiregulin levels were significantly higher in NHL patients compared to the control group (P < 0.0001). Similarly, a significant increase in epiregulin levels was observed in advanced NHL patients. Furthermore, the most common NHL subgroup within the NHL group, diffuse Large B Cell Lymphoma (DLBCL), and the subgroup with extranodal involvement also had significantly higher levels of epiregulin. A positive correlation was found between the epiregulin molecule and CRP, beta 2-microglobulin, and lactate dehydrogenase (LDH) levels in NHL patients. Our study suggests that serum epiregulin levels, discovered to increase in NHL patients for the first time, may be an independent predictive molecule in an advanced stage, extranodal involvement, and the DLBCL subtype of this disease. Epiregulin positively correlates with prognostic molecules such as beta 2-microglobulin, LDH, and CRP. Illuminating its potential role in NHL pathogenesis could make epiregulin a vital drug target for treatment.

N-Methyl-2-{3-methyl-2-[(2Z)-pent-2-en-1-yl]cyclo-pent-2-en-1-yl-idene}hydrazinecarbo-thio-amide.

The equimolar and hydro-chloric acid-catalysed reaction between cis-jasmone and 4-methyl-thio-semicarbazide in ethano-lic solution yields the title compound, C13H21N3S (common name: cis-jasmone 4-methyl-thio-semicarbazone). Two mol-ecules with all atoms in general positions are present in the asymmetric unit. In one of them, the carbon chain is disordered [site occupancy ratio = 0.821 (3):0.179 (3)]. The thio-semicarbazone entities [N-N-C(=S)-N] are approximately planar, with the maximum deviation from the mean plane through the selected atoms being -0.0115 (16) Å (r.m.s.d. = 0.0078 Å) for the non-disordered mol-ecule and 0.0052 (14) Å (r.m.s.d. = 0.0031 Å) for the disordered one. The mol-ecules are not planar, since the jasmone groups have a chain with sp 3-hybridized carbon atoms and, in addition, the thio-semicarbazone fragments are attached to the respective carbon five-membered rings and the dihedral angles between them for each mol-ecule amount to 8.9 (1) and 6.3 (1)°. In the crystal, the mol-ecules are connected through pairs of N-H⋯S and C-H⋯S inter-actions into crystallographically independent centrosymmetric dimers, in which rings of graph-set motifs R 2 2(8) and R 2 1(7) are observed. A Hirshfeld surface analysis indicates that the major contributions for the crystal cohesion are from H⋯H (70.6%), H⋯S/S⋯H (16.7%), H⋯C/C⋯H (7.5%) and H⋯N/N⋯H (4.9%) inter-actions [considering the two crystallographically independent mol-ecules and only the disordered atoms with the highest s.o.f. for the evaluation].

5,6-Di-methyl-benzo[d][1,3]oxatellurole.

The structure of the title compound, C9H10OTe, at 100 K has ortho-rhom-bic (P21212) symmetry with two independent mol-ecules in the asymmetric unit (Z' = 2). The mol-ecules are folded along their Te⋯O axes, with their Te-C-O planes angled at an average of 25.1° with respect to the remaining non-H atoms, which are almost coplanar (average deviation from planarity = 0.04 Å). A Hirshfeld plot shows weak inter-molecular inter-actions between the two Te atoms located in each asymmetric mol-ecule, with a Te⋯Te distance of 3.7191 (4) Å. The structure is strongly pseudosymmetric to the space group Pccn with Z' = 1. The crystal chosen for data collection was found to be was an inversion twin.

Crystal structure and Hirshfeld surface analysis of (E)-2-[2-(2-amino-1-cyano-2-oxoethylidene)hydrazin-1-yl]benzoic acid N,N-dimethylformamide monosolvate

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 R 2 2(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).

STRUCTURAL INVESTIGATION AND HIRSHFELD SURFACE ANALYSIS OF TWO [ONO]-TYPE SCHIFF BASES

Two novel [ONO]-type tridentate Schiff base compounds namely (E)-2-(((2-hydroxyphenyl)imino)methyl)-4,5-dimethoxyphenol, C15H15NO4 (1), and (E)-2-(((5-chloro-2-hydroxyphenyl)imino)methyl)-4,5-dimethoxyphenol, C15H14ClNO4 (2) were synthesized. These compounds were characterized using various spectroscopic techniques, including single crystal X-ray diffraction (XRD), infrared (IR), proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR), and UV-Vis spectroscopy. The X-ray crystallographic analysis revealed that both compounds 1 and 2 contain two independent molecules within the asymmetric unit. Compound 1 crystallizes in the orthorhombic system with the Pna21 space group, while compound 2 crystallizes in the monoclinic system with the P21/c space group. An important feature observed in the crystal structure of compound 1 is the presence of O–H···N and O–H···O hydrogen bonds. In compound 2, the hydrogen bonding interactions involve C–H···O, O–H···O and O–H···N. Additionally, both compounds exhibit C–H···π interactions. To further understand the bonding interactions in compounds 1 and 2, Hirshfeld surface analyses and 2D fingerprint graphs were performed. The results indicate that the Hirshfeld surfaces are predominantly influenced by H⋯H, O⋯H, and C⋯H contacts.

Temperature-dependent solid-state phase transition with twinning in the crystal structure of 4-meth-oxy-anilinium chloride.

At room temperature, the title salt, C7H10NO+·Cl-, is ortho-rhom-bic, space group Pbca with Z' = 1, as previously reported [Zhao (2009 ▸). Acta Cryst. E65, o2378]. Between 250 and 200 K, there is a solid-state phase transition to a twinned monoclinic P21/c structure with Z' = 2. We report the high temperature structure at 250 K and the low-temperature structure at 100 K. In the low-temperature structure, the -NH3 hydrogen atoms are ordered and this group has a different orientation in each independent mol-ecule, in keeping with optimizing N-H⋯Cl hydrogen bonding, some of which are bifurcated: these hydrogen bonds have N⋯Cl distances in the range 3.1201 (8)-3.4047 (8) Å. In the single cation of the high-temperature structure, the NH hydrogen atoms are disordered into the average of the two low-temperature positions and the N⋯Cl hydrogen bond distances are in the range 3.1570 (15)-3.3323 (18) Å. At both temperatures, the meth-oxy group is nearly coplanar with the rest of the mol-ecule, with the C-C-O-C torsion angles being -7.0 (2)° at 250 K and -6.94 (12) and -9.35 (12)° at 100 K. In the extended ortho-rhom-bic structure, (001) hydrogen-bonded sheets occur; in the monoclinic structure, the sheets propagate in the (010) plane.

Crystal structure of 2-[(5-amino-1-tosyl-1H-pyrazol-3-yl)-oxy]-1-(4-meth-oxy-phen-yl)ethan-1-one 1,4-dioxane monosolvate.

In the structure of the title compound, C19H19N3O5S·C4H8O2, the two independent dioxane mol-ecules each display inversion symmetry. The pyrazole ring is approximately parallel to the aromatic ring of the oxy-ethanone group and approximately perpendicular to the tolyl ring of the sulfonyl substituent. An extensive system of classical and 'weak' hydrogen bonds connects the residues to form a layer structure parallel to (201), within which dimeric subunits are conspicuous; neighbouring layers are connected by classical hydrogen bonds to dioxanes and by 'weak' hydrogen bonds from Htol-yl donors.

Crystal structures of sixteen phosphane chalcogenide complexes of gold(I) chloride, bromide and iodide.

The structures of 16 phosphane chalcogenide complexes of gold(I) halides, with the general formula R 1 3- nR 2 nPEAuX (R 1 = t-butyl; R 2 = isopropyl; n = 0 to 3; E = S or Se; X = Cl, Br or I), are presented. The eight possible chlorido derivatives are: 1a, n = 3, E = S; 2a, n = 2, E = S; 3a, n = 1, E = S; 4a, n = 0, E = S; 5a, n = 3, E = Se; 6a, n = 2, E = Se; 7a, n = 1, E = Se; and 8a, n = 0, E = Se, and the corresponding bromido derivatives are 1b-8b in the same order. However, 2a and 2b were badly disordered and 8a was not obtained. The iodido derivatives are 2c, 6c and 7c (numbered as for the series a and b). All structures are solvent-free and all have Z' = 1 except for 6b and 6c (Z' = 2). All mol-ecules show the expected linear geometry at gold and approximately tetra-hedral angles P-E-Au. The presence of bulky ligands forces some short intra-molecular contacts, in particular H⋯Au and H⋯E. The Au-E bond lengths have a slight but consistent tendency to be longer when trans to a softer X ligand, and vice versa. The five compounds 1a, 5a, 6a, 1b and 5b form an isotypic set, despite the different alkyl groups in 6a. Compounds 3a/3b, 4b/8b and 6b/6c form isotypic pairs. The crystal packing can be analysed in terms of various types of secondary inter-actions, of which the most frequent are 'weak' hydrogen bonds from methine hydrogen atoms to the halogenido ligands. For the structure type 1a, H⋯X and H⋯E contacts combine to form a layer structure. For 3a/3b, the packing is almost featureless, but can be described in terms of a double-layer structure involving borderline H⋯Cl/Br and H⋯S contacts. In 4a and 4b/8b, which lack methine groups, Cmeth-yl-H⋯X contacts combine to form layer structures. In 7a/7b, short C-H⋯X inter-actions form chains of mol-ecules that are further linked by association of short Au⋯Se contacts to form a layer structure. The packing of compound 6b/6c can conveniently be analysed for each independent mol-ecule separately, because they occupy different regions of the cell. Mol-ecule 1 forms chains in which the mol-ecules are linked by a Cmethine⋯Au contact. The mol-ecules 2 associate via a short Se⋯Se contact and a short H⋯X contact to form a layer structure. The packing of compound 2c can be described in terms of two short Cmethine-H⋯I contacts, which combine to form a corrugated ribbon structure. Compound 7c is the only compound in this paper to feature Au⋯Au contacts, which lead to twofold-symmetric dimers. Apart from this, the packing is almost featureless, consisting of layers with only translation symmetry except for two very borderline Au⋯H contacts.