Synthesis, crystal structure and Hirshfeld surface analysis of 4-{(1E)-1-[(car-bamo-thioyl-amino)-imino]-eth-yl}phenyl propano-ate.

The title compound, C12H15N3O2S, adopts an E configuration with respect to the C=N bond. The propionate group adopts an anti-periplanar (ap) conformation. There are short intra-molecular N-H⋯N and C-H⋯O contacts, forming S(5) and S(6) ring motifs, respectively. In the crystal, mol-ecules are connected into ribbons extending parallel to [010] by pairs of N-H⋯S inter-actions, forming rings with R 2 2(8) graph-set motifs, and by pairs of C-H⋯S inter-actions, where rings with the graph-set motif R 2 1(7) are observed. The O atom of the carbonyl group is disordered over two positions, with a refined occupancy ratio of 0.27 (2):0.73 (2). The studied crystal consisted of two domains.

Ligand recognition by peptidoglycan recognition protein-S (PGRP-S): structure of the complex of camel PGRP-S with heptanoic acid at 2.15 Å resolution.

Peptidoglycan recognition proteins (PGRPs) are important components of the innate immune system which provide the first line of defense against invading microbes. There are four members in the family of PGRPs in animals of which PGRP-S is a common domain. It is responsible for the binding to microbial cell wall molecules. In order to understand the mode of binding of PGRP-S to the components of the bacterial cell wall, the structure of the complex of camel PGRP-S (CPGRP-S) with heptanoic acid has been determined at 2.15 Å resolution. The structure determination showed the presence of four crystallographically independent protein molecules which are designated as A, B, C, and D. These four protein molecules associate in the form of two homodimers which are represented as A-B and C-D dimers. The association between molecules A and B gives rise to a shallow cleft on the surface at one end of the dimeric interface. One molecule of heptanoic acid is observed at this binding site in the A-B dimer. The association of C and D molecules results in the formation of a long zig-zag tunnel along with the C-D interface. In the cleft at the C-D interface, three molecules of hydrogen peroxide along with other non-water solvent molecules have been observed. The analysis of the several complexes of CPGRP-S with fatty acids and non-fatty acids such as peptidoglycan, lipopolysaccharide, and lipoteichoic acid shows that the fatty acids bind at the A-B site while non-fatty acids interact through C-D interface.

Crystal structures and Hirshfeld surface analyses of 4,4'-{[1,3-phenyl-enebis(methyl-ene)]bis-(-oxy)}bis-(3-meth-oxy-benzaldehyde) and 4,4'-{[(1,4-phenyl-ene-bis(methyl-ene)]bis-(-oxy)}bis-(3-meth-oxy-benzalde-hyde).

The title compounds, C24H22O6 (I) and C24H22O6 (II), each crystallize with half a mol-ecule in the asymmetric unit. The whole mol-ecule of compound (I) is generated by twofold rotation symmetry, the twofold axis bis-ecting the central benzene ring. The whole mol-ecule of compound (II) is generated by inversion symmetry, the central benzene ring being located on an inversion center. In (I), the outer benzene rings are inclined to each other by 59.96 (10)° and by 36.74 (9)° to the central benzene ring. The corresponding dihedral angles in (II) are 0.0 and 89.87 (12)°. In the crystal of (I), mol-ecules are linked by C-H⋯O hydrogen bonds and C-H⋯π inter-actions, forming ribbons propagating along the [10] direction. In the crystal of (II), mol-ecules are linked by C-H⋯O hydrogen bonds, forming a supra-molecular framework. The Hirshfeld surface analyses indicate that for both compounds the H⋯H contacts are the most significant, followed by O⋯H/H⋯O and C⋯H/H⋯C contacts.

Crystal structures and Hirshfeld surface analyses of 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(pyridin-2-yl)acetamide and 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(pyrazin-2-yl)acetamide.

In the title compounds, C11H12N6OS (I) and C10H11N7OS (II), the di-amino-pyrimidine ring makes dihedral angles of 71.10 (9)° with the pyridine ring in (I) and 62.93 (15)° with the pyrazine ring in (II). The ethanamine group, -CH2-C(=O)-NH- lies in the plane of the pyridine and pyrazine rings in compounds (I) and (II), respectively. In both compounds, there is an intra-molecular N-H⋯N hydrogen bond forming an S(7) ring motif and a short C-H⋯O inter-action forming an S(6) loop. In the crystals of both compounds, mol-ecules are linked by pairs of N-H⋯N hydrogen bonds, forming inversion dimers with R22(8) ring motifs. In (I), the dimers are linked by N-H⋯O and N-H⋯N hydrogen bonds, forming layers parallel to (1[Formula: see text] [Formula: see text]). The layers are linked by offset π-π inter-actions [inter-centroid distance = 3.777 (1) Å], forming a three-dimensional supra-molecular structure. In (II), the dimers are linked by N-H⋯O, N-H⋯N and C-H⋯O hydrogen bonds, also forming a three-dimensional supra-molecular structure.

In vitro and in vivo anti-proliferative evaluation of bis(4'-(4-tolyl)-2,2':6',2″-terpyridine)copper(II) complex against Ehrlich ascites carcinoma tumors.

The bis(4'-(4-tolyl)-2,2':6',2″-terpyridine)copper(II) complex [Cu(ttpy)2]Cl2 was synthesized and authenticated by single crystal analysis, which shows distorted octahedral geometry around copper(II) ion. The crystal packing is stabilized by C-H···π inter and intramolecular interactions. The complex was found to be lipophilic as determined by shake-flask method. In vitro cytotoxicity of the complex was tested against Ehrlich ascites carcinoma (EAC) and L6 myotube cell lines. The complex exhibit potent cytotoxicity with respect to the commercially available anticancer drug cisplatin. Hoechst 33258, AO/EB and PI (flow cytometry) staining methods suggest that the complex can induce apoptosis in EAC cells. Cell cycle analyses also support the induced apoptosis. Cellular uptake studies revealed that the complex can go into the cytoplasm and accumulate in the cell nuclei. The complex induces EAC cell apoptosis through a ROS-mediated mitochondrial pathway by activating caspase 3 and caspase 7 and regulates the Bcl-2 family proteins. In vivo study of the complex was validated against the animal tumor growth (EAC) cell in Swiss albino mice. The bis(4'-(4-tolyl)-2,2':6',2″-terpyridine)copper(II) complex induces EAC cell apoptosis through a ROS-mediated mitochondrial pathway and significantly reduced the body weight and solid tumor volume in Swiss albino mice.

Crystal structures of 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(2,4-di-methyl-phen-yl)acetamide and 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(3-meth-oxy-phen-yl)acetamide.

In the title compounds, C14H17N5OS (I) and C13H15N5O2S (II), the dihedral angle between the pyrimidine and benzene rings is 58.64 (8)° in (I) and 78.33 (9)° in (II). In both compounds, there is an intra-molecular C-H⋯O hydrogen bond, and in (II) there is also an intra-molecular N-H⋯N hydrogen bond present. In the crystals of both compounds, a pair of N-H⋯N hydrogen bonds links the individual mol-ecules to form inversion dimers with R22(8) ring motifs. In (I), the dimers are linked by N-H⋯O and C-H⋯O hydrogen bonds, enclosing R21(14), R21(11) and R21(7) ring motifs, forming layers parallel to the (100) plane. There is also an N-H⋯π inter-action present within the layer. In (II), the inversion dimers are linked by N-H⋯O hydrogen bonds enclosing an R44(18) ring motif. The presence of N-H⋯O and C-H⋯O hydrogen bonds generate an R21(6) ring motif. The combination of these various hydrogen bonds results in the formation of layers parallel to the (1-11) plane.

Crystal structures of N-(4-chloro-phen-yl)-2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]acetamide and N-(3-chloro-phen-yl)-2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]acetamide.

The title compounds, C12H12ClN5OS, (I), and C12H12ClN5OS, (II), are 2-[(di-amino-pyrimidin-2-yl)sulfan-yl]acetamides. Compound (II), crystallizes with two independent mol-ecules (A and B) in the asymmetric unit. In each of the mol-ecules, in both (I) and (II), an intra-molecular N-H⋯N hydrogen bond forms an S(7) ring motif. The pyrimidine ring is inclined to the benzene ring by 42.25 (14)° in (I), and by 59.70 (16) and 62.18 (15)° in mol-ecules A and B, respectively, of compound (II). In the crystal of (I), mol-ecules are linked by pairs of N-H⋯N hydrogen bonds, forming inversion dimers with an R22(8) ring motif. The dimers are linked via bifurcated N-H⋯O and C-H⋯O hydrogen bonds, forming corrugated layers parallel to the ac plane. In the crystal of (II), the A mol-ecules are linked through N-H⋯O and N-H⋯Cl hydrogen bonds, forming layers parallel to (100). The B mol-ecules are also linked by N-H⋯O and N-H⋯Cl hydrogen bonds, also forming layers parallel to (100). The parallel layers of A and B mol-ecules are linked via N-H⋯N hydrogen bonds, forming a three-dimensional structure.

Crystal structures of 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(naphthalen-1-yl)acetamide and 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(4-fluoro-phen-yl)acetamide.

The title compounds, C16H15N5OS, (I), and C12H12FN5OS, (II), are [(di-amino-pyrimidine)-sulfan-yl]acetamide derivatives. In (I), the pyrimidine ring is inclined to the naphthalene ring system by 55.5 (1)°, while in (II), the pyrimidine ring is inclined to the benzene ring by 58.93 (8)°. In (II), there is an intra-molecular N-H⋯N hydrogen bond and a short C-H⋯O contact. In the crystals of (I) and (II), mol-ecules are linked by pairs of N-H⋯N hydrogen bonds, forming inversion dimers with R22(8) ring motifs. In the crystal of (I), the dimers are linked by bifurcated N-H⋯(O,O) and C-H⋯O hydrogen bonds, forming layers parallel to (100). In the crystal of (II), the dimers are linked by N-H⋯O hydrogen bonds, also forming layers parallel to (100). The layers are linked by C-H⋯F hydrogen bonds, forming a three-dimensional architecture.

Crystal structures of (E)-4-[1-(2-carbamo-thio-yl-hydrazinyl-idene)eth-yl]phenyl acetate and (E)-4-[1-(2-carbamo-thio-ylhydrazinyl-idene)eth-yl]phenyl benzoate.

In the title compounds, C11H13N3O2S, (I), and C16H15N3O2S, (II), the thio-semicarbazone group adopts an extended conformation. The acetate ester (I) crystallizes with two independent mol-ecules in the asymmetric unit. In the benzoate ester (II), the planes of the two aryl rings are inclined to one another by 46.70 (7)°. In both compounds, there is a short intra-molecular N-H⋯N contact present, forming an S(5) ring motif. In the crystals of both compounds, mol-ecules are linked via pairs of N-H⋯S hydrogen bonds, forming dimers with R22(8) ring motifs. The dimers are linked by N-H⋯S and N-H⋯O hydrogen bonds, forming slabs parallel to (01-1). In (I), there are N-H⋯π and C-H⋯π inter-actions present within the slabs, while in (II), there are only N-H⋯π inter-actions present.

Crystal structures of two substituted thia-zolidine derivatives.

In the first of the compounds reported herein, namely 6'-ferrocenyl-6a'-nitro-6',6a',6b',7',9',11a'-hexa-hydro-2H-spiro-[ace-naphthyl-ene-1,11'-chromeno[3',4':3,4]pyrrolo-[1,2-c]thia-zol]-2-one, [Fe(C5H5)(C29H21N2O4S)], (I), the thia-zolidine ring adopts a twist conformation on the methine N-C atoms. In the second compound, viz. 6'-(4-methoxy-phen-yl)-6a'-nitro-6',6a',6b',7',9',11a'-hexa-hydro-2H-spiro-[ace-naphthyl-ene-1,11'-chromeno[3',4':3,4]pyrrolo-[1,2-c]thia-zol]-2-one, [Fe(C5H5)(C26H19N2O5S)], (II), the thia-zolidine ring adopts an envelope conformation with a methine C atom as the flap. In both compounds, the pyrrolidine ring adopts a twist conformation on the thia-zolidine and tetra-hydro-pyran C atoms. The mean planes of the thia-zolidine and pyrrolidine rings subtend angles of 67.30 (1) and 62.95 (7)° in (I) and (II), respectively, while the mean plane of the pyrrolidine ring makes dihedral angles of 76.53 (1) and 87.74 (7)° with the ace-naphthyl-ene ring system in (I) and (II), respectively. In both compounds, an intra-molecular C-H⋯O hydrogen bond forms an S(7) ring motif. In the crystal of (I), mol-ecules are linked via two different C-H⋯O hydrogen bonds, forming chains along [001] and [100]. In (II), they are linked through C-H⋯O hydrogen bonds, forming dimers with an R 2 (2)(10) ring motif while C-H⋯π inter-actions link the mol-ecules in a head-to-tail fashion, forming chains along the a-axis direction.

Targeting of DNA molecules, BSA/c-Met tyrosine kinase receptors and anti-proliferative activity of bis(terpyridine)copper(ii) complexes.

A series of homoleptic bis(terpyridine)copper(ii) complexes of the type [Cu(L(1-5))2]Cl2 (), where L(1-5) = 4'-(4-substituted)-2,2':6',2''-terpyridines, have been synthesized and characterized. The molecular structure of complex was confirmed by the single crystal XRD technique, and the geometry of the complexes is best described as distorted octahedral. Structural parameters from the crystallographic and DFT studies are in good agreement with each other. The small HOMO-LUMO energy gap supports bioefficacy of the complexes. DNA binding studies show high intrinsic binding constant values 1.53 ± 0.15, 1.62 ± 0.08 and 3.09 ± 0.12 × 10(5) M(-1) for complexes , and , respectively, with intercalative mode of binding to CT-DNA. The binding results were further supported by molecular docking studies. The experimental results indicate that the interaction between the complexes and BSA protein involves a static quenching mechanism. The molecular docking studies with c-Met tyrosine kinase receptors show hydrophobic and π-π interactions. All the complexes bring about hydroxyl radical mediated DNA cleavage in the presence of H2O2. In vitro cytotoxicities of the complexes () were tested against three cancerous cell lines, namely human breast adenocarcinoma (MCF-7), epithelioma (Hep-2) and cervical (HeLa) cell lines, and one non-tumorigenic human dermal fibroblast (NHDF) cell line by MTT reduction assay. The morphological assessment data obtained using Hoechst 33258 staining revealed that complex induces apoptosis much more effectively than the other complexes.

Crystal structure of ethyl 6-chloro-methyl-2-oxo-4-(2,3,4-tri-meth-oxy-phen-yl)-1,2,3,4-tetra-hydro-pyrimidine-5-carboxyl-ate.

In the title compound, C17H21ClN2O6, the di-hydro-pyrimidine ring adopts a flattened envelope conformation, with the sp (3)-hybridized C atom forming the flap. The dihedral angle between the least-squares planes of the benzene and di-hydro-pyrimidine rings is 88.09 (6)°. An intra-molecular C-H⋯O hydrogen bond generates an S(6) ring. In the crystal, mol-ecules are linked via pairs of N-H⋯O hydrogen bonds, forming inversion dimers with an R 2 (2)(8) ring motif, and the dimers are linked via further pairs of N-H⋯O hydrogen bonds, forming R 2 (2)(14) rings and chains of mol-ecules along [111]. Pairs of inversion-related chains are linked via weak C-H⋯π inter-actions.

Crystal structures of two triazola-dioxola-benzena-cyclo-nona-phanes.

In the title compounds, C25H29BrN5O7, (I) [systematic name: (Z)-1(5)-bromo-3(2),3(2)-dimethyl-2(1)-nitro-2(2),2(3),2(5),2(6),2(7),2(7a),3(3a),3(5),3(6),3(6a)-deca-hydro-2(1) H,6(1) H-4,9-dioxa-2(3,2)-pyrrolizina-6(4,1)-triazola-3(5,6)-furo[2,3-d][1,3]dioxola-1(1,2)-benzena-cyclo-nona-phane], and C24H29N5O7S, (II) [systematic name: (Z)-3(2),3(2)-dimethyl-2(7)-nitro-2(5),2(6),2(7),2(7a),3(3a),3(5),3(6),3(6a)-octa-hydro-2(1) H,2(3) H,6(1) H-4,9-dioxa-2(5,6)-pyrrolo-[1,2-c]thia-zola-6(4,1)-triazola-3(5,6)-furo[2,3-d][1,3]dioxola-1(1,2)-benzena-cyclo-nona-phane], the triazole rings adopt almost planar conformations. In (I), the fused pyrrolidine rings adopt envelope conformations with the C atoms opposite the fused N-C bond as the flap in each ring, and their mean planes are inclined to one another by 52.8 (3)°. In (II), the pyrrolidine and thia-zole rings are both twisted on the fused N-C bond, and their mean planes are inclined to one another by 70.8 (2)°. In both (I) and (II), the furan ring adopts an envelope conformation with the adjacent C atom of the macrocycle as the flap. In the crystal of (I), mol-ecules are linked via C-H⋯N and C-H⋯O hydrogen bonds, forming sheets parallel to (10-1), while in (II), mol-ecules are linked via C-H⋯N and C-H⋯O hydrogen bonds, forming helical chains propagating along [010], which are linked via C-H⋯S hydrogen bonds, forming slabs parallel to (001).

Crystal structure of 2-(4-fluoro-3-methyl-phen-yl)-5-{[(naphthalen-1-yl)-oxy]meth-yl}-1,3,4-oxa-diazole.

The title compound, C20H15FN2O2, adopts an almost planar conformation. The oxa-diazole ring makes dihedral angles of 13.90 (1) and 7.93 (1)° with the naphthalene ring system and benzene ring, respectively, while the naphthalene ring system and benzene ring are inclined to one another by 6.35 (1)°. In the crystal, adjacent mol-ecules are linked via C-H⋯N hydrogen bonds, forming chains propagating along [100]. There are also π-π inter-actions present [inter-centroid distances = 3.5754 (9) and 3.7191 (12) Å], linking the chains to form ribbons lying parallel to (011).

Crystal structure of ethyl 6-methyl-2-sulfanyl-idene-4-(thio-phen-2-yl)-1,2,3,4-tetra-hydro-pyrimidine-5-carboxyl-ate.

In the title compound, C12H14N2O2S2, the di-hydro-pyrimidine ring adopts a sofa conformation, with the C atom bearing the thienyl ring lying above the plane of the five remaining approximately coplanar (r.m.s. deviation = 0.0405 Å) atoms of the ring. The dihedral angle between the five near coplanar atoms of the ring and the thienyl ring is 89.78 (11)°. In the crystal, mol-ecules are linked into a supra-molecular chain along [100] via N-H⋯O(carbon-yl) hydrogen bonds. Inversion-related chains are linked into double chains via N-H⋯S(thione) hydrogen bonds. The three-dimensional architecture also features meth-yl-thienyl C-H⋯π inter-actions.

Crystal structure of 2-{[(naphthalen-1-yl)oxy]meth-yl}-5-(2,4,5-tri-fluoro-phen-yl)-1,3,4-oxa-diazole.

In the title compound C19H11F3N2O2, the oxa-diazole ring and the naphthalene ring system are approximately planar (r.m.s. deviations of 0.001 and 0.020 Å, respectively) and the oxa-diazole ring makes dihedral angles of 13.11 (1) and 7.59 (1)° with the naphthalene ring system and the tri-fluoro-phenyl ring, respectively. In the crystal, C-H⋯N hydrogen bonds link mol-ecules into chains along the a-axis direction, while C-H⋯F contacts form additional chains along the ac diagonal. These contacts generate sheets of mol-ecules approximately parallel to the (011) plane.

Crystal structure of (E)-4-{1-[2-(car-bamo-thio-yl)hydrazin-1-yl-idene]ethyl}phenyl 4-methyl-benzoate.

The asymmetric unit of the title compound, C17H17N3O2S, consists of two independent mol-ecules, A and B, with different conformations: in mol-ecule A, the dihedral angles between the central benzene ring and the pendant tolyl and carbamo-thio-ylhydrazono groups are 71.12 (9) and 5.95 (8)°, respectively. The corresponding angles in mol-ecule B are 50.56 (12) and 26.43 (11)°, respectively. Both mol-ecules feature an intra-molecular N-H⋯N hydrogen bond, which closes an S(5) ring. In the crystal, mol-ecules are linked by N-H⋯O, N-H⋯S and C-H⋯O hydrogen bonds, generating a three-dimensional network.

Crystal structures of two 2,9-di-thia-13-aza-dispiro-[4.1.4(7).3(5)]tetra-decan-6-ones.

In the title compounds 4,11-dihy-droxy-13-methyl-1,8-di-p-tolyl-2,9-di-thia-13- aza-dispiro-[4.1.4(7).3(5)]tetra-decan-6-one, C26H31NO3S2, (I), and 13-benzyl-4,11-dihy-droxy-1,8-bis-(4-methyl-phen-yl)-2,9-di-thia-13-aza-dispiro-[4.1.4(7).3(5)]tetradecan-6-one, C32H35NO3S2, (II), the piperidine rings adopt distorted chair conformations. The thio-phene rings in (I) have envelope conformations, with the spiro C atoms as the flaps. In (II), one thio-phene ring (D) has an envelope conformation, with the hy-droxy-substituted C atom as the flap, while the other thio-phene ring (E) has a twisted conformation on the C-C bond involving the spiro C atom and the toluyl-substituted C atom. In (I), the mean plane of the piperidine ring makes dihedral angles of 75.16 (9) and 73.33 (8)° with the mean planes of the thio-phene rings (D and E), respectively. In (II), the corresponding dihedral angles are 70.95 (11) and 77.43 (12)°. In both compounds, there is an intra-molecular O-H⋯O hydrogen bond forming an S(6) ring motif. In the crystal of (I), mol-ecules are linked via O-H⋯N and C-H⋯O hydrogen bonds, forming chains along [010]. There are also π-π inter-actions present involving inversion-related benzene rings, linking the chains to form slabs parallel to (100). In the crystal of (II), mol-ecules are linked via O-H⋯O hydrogen bonds, forming inversion dimers with an R 4 (4)(8) ring motif. The dimers are linked by C-H⋯π inter-actions, forming slabs parallel to (001).

Crystal structure of 4'-(2-meth-oxy-quinolin-3-yl)-1'-methyl-dispiro-[indan-2,2'-pyrrolidine-3',3''-indoline]-1,3,2''-trione.

In the title compound, C30H23N3O4, the central 1-methyl-pyrrolidine ring adopts a twist conformation on the N-CH2 bond. The pyrrolidin-2-one ring of the indolin-2-one ring system also has a twist conformation on the C-C bond involving the spiro C atom and the carbonyl C atom. The five-membered ring of the indene-1,3-dione moiety has an envelope conformation with the spiro C atom as the flap. The quinoline ring system adopts an almost planar conformation (r.m.s. deviation = 0.04 Å). The mean planes of the indolin-2-one ring system, the indene-1,3-dione ring system and the the quinoline ring system are inclined to the mean plane of the central 1-methyl-pyrrolidine ring by 77.97 (7), 86.98 (7) and 46.58 (6)°, respectively. In the crystal, mol-ecules are linked via N-H⋯N hydrogen bonds, forming chains along the b axis. The chains are linked via a number of C-H⋯O hydrogen bonds, and C-H⋯π and π-π inter-actions [inter-centroid distance = 3.7404 (9) Å], forming a three-dimensional network.

Crystal structure of 15-(2-chloro-phen-yl)-6b-hy-droxy-17-methyl-6b,7,16,17-tetra-hydro-7,14a-methanona-phtho[1',8':1,2,3]pyrrolo-[3',2':8,8a]azuleno[5,6-b]quinolin-14(15H)-one.

In the title compound, C34H25ClN2O2, the fused pyrrolidine ring adopts an envelope conformation with the N atom as the flap. The two adjacent cyclo-pentane rings also adopt envelope conformations. The mean plane of the pyrrolidine ring makes dihedral angles of 40.53 (10) and 80.23 (10)° with the mean planes of the cyclo-pentane rings. The dihedral angle between the mean planes of the cyclo-pentane rings is 46.71 (9)°. An intra-molecular O-H⋯N hydrogen bond is observed. In the crystal, mol-ecules are linked by C-H⋯O, C-H⋯N and C-H⋯π inter-actions, forming a layer parallel to (10-2).