The complete molecule of the title compound, C18H20N2O4, is generated by inversion symmetry. The conformation around the C=N bond is E. With the exception of the eth­oxy substituent, the mol­ecule is essentially planar with an r.m.s. deviation of 0.0455 Å. In the crystal, mol­ecules are linked by O—H⋯N hydrogen bonds into a two-dimensional supra­molecular network parallel to the bc plane.

The mol­ecule of the title compound, C20H16N2O2, is centrosymmetric, the inversion center being located at the mid-point of the central azine bond. The conformation around the C=N bond is E. The whole mol­ecule (except for the H atoms) is essentially planar, with an r.m.s. deviation of 0.07 Å. In the crystal, mol­ecules are linked head-to-tail by pairs of C—H⋯O hydrogen bonds, forming inversion dimers, and resulting in the formation of chains propagating along [011].

The mol­ecule of the title compound, C20H16N2O2, is centrosymmetric with the mid-point of the central N—N bond located on an inversion center. The configuration around the C=N bond is E. The whole mol­ecule (except for the H atoms) is approximately planar, with an r.m.s. deviation of 0.07 Å. In the crystal, the presence of weak inter­molecular C—H⋯O hydrogen bonding involving each acetyl­ene H atom and the adjacent phen­oxy O atom results in the formation of supra­molecular chains.

In the title compound, C22H19N3O2, the phenol ring forms dihedral angles of 88.93 (10) and 87.95 (12)° with the benzimidazole system and the quinazoline benzene ring, respectively. In the crystal, mol­ecules are linked via O—H⋯N hydrogen bonds into infinite chains along [100]. An intra­molecular N—H⋯O hydrogen bond generates an S(6) ring.

In the zwitterionic title compound, C18H16N2O4, the dihedral angle between the planes of the benzene and indole rings is 26.38 (10)°. An intra­molecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, mol­ecules are linked through N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds into infinite chains propagating in [010].

In the zwitterionic title compound, C18H16N2O4·H2O, the dihedral angle between the planes of the benzene and indole rings is 39.20 (8)°. An intra­molecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, inter­molecular hy­droxy and water O—H⋯O(carboxyl­ate) and N+—H⋯O(carboxyl­ate) and indole N—H⋯O(water) hydrogen bonds give a three-dimensional structure.

In the title carboxyl­ate-bridged polymer, [Sn(C7H7)3(C7H5O3)]n, the SnIV atom exists in a distorted trans-C3SnO2 trigonal–bipyramidal geometry. The polymer propagates as a chain along the a axis. There are two independent formula units in the asymmetric unit; the furyl ring of one of the anions is disordered over two positions in a 0.630 (8):0.370 (8) ratio. The crystal studied was a non-merohedral twin with a minor twin domain of 37.3 (1)%.

In the title compound, [Cu(C7H5O3)2(C5H5N)2], the Cu atom is located on an inversion center and is coordinated by the N atoms of the two pyridine ligands, trans to each other, and to the carboxyl­ate O atoms of two bidentate 4-hy­droxy­benzoate ligands [Cu—O = 1.9706 (10) and 2.5204 (11) Å]. Hydrogen bonding between hy­droxy H and carboxyl­ate O atoms results in a layer structure parallel to the ab plane.

In the title salt, [C6H5N(CH3)3][Sn2Br5(C7H6Br)4], the SnIV atoms of the dinuclear anion are bridged by a Br atom; the Sn—Brbridge bond lengths are 2.9818 (5) and 3.0470 (5) Å. Both Sn atoms show a distorted cis-trigonal–bipyramidal coordination geometry that is distorted towards a square pyramid. In the crystal, weak C—H⋯π inter­actions occur between anions and cations.

The dinuclear compound, [V2(C12H11BrN2O2)2(CH3O)2O2], lies on a center of inversion. The doubly-deprotonated Schiff base O,N,O′-chelates to the VV atom; two metal atoms are bridged by the methoxide units. The coordination geometry is a distorted octa­hedron. Weak inter­molecular C—H⋯N hydrogen bonding is present in the crystal structure. The bromo­phenyl unit is disordered over two positions, with the major component being in a 0.909 (6) proportion.

The coordination geometry at the MoVI atom in the title compound, [Mo(C16H14N2O4)O2(C2H6OS)], is distorted octa­hedral. The phenolate O, imino N, oxide O from the enolized carbonyl group and one of the terminal O atoms form the equatorial plane; the axial positions are occupied by the other terminal O atom of the dioxidomolybdenum group and the donor O atom of DMSO. The O=Mo=O angle is 105.31 (6)°. An intra­molecular O—H⋯N hydrogen bond and weak inter­molecular C—H⋯O hydrogen bonds are present in the structure.

In the title tribenzyl­chloridotin–triphenyl­phosphine adduct, [Sn(C7H7)3Cl(C18H15OP)], the SnIV atom is in a trans-C3SnClO trigonal–bipyramidal geometry and is displaced out of the C3Sn girdle in the direction of the axial Cl atom by 0.112 (1) in one independent mol­ecule and by 0.167 (1) Å in the other. The phenyl ring of one of the six benzyl units was refined as equally disordered over two sets of sites.

The VV atom in the polymeric title compound, [NaV(C15H13N3O3)O2(H2O)2]n, is O,N,O′-chelated by the Schiff base dianion and is five-coordinated in a trigonal–bipramidal coordination geometry. The oxide O atoms occupy the equatorial sites and one oxide O atom is connected to the NaI atom. The ligand simultaneously O,O′-chelates to the water-coordinated NaI atom; its coordination number is seven owing to an Na⋯Npyrid­yl bond. The two independent formula units, which are disposed about a false center of inversion, are connected into a layer. Adjacent layers are consolidated into a three-dimensional network by O—H⋯O and O—H⋯N hydrogen bonds.

In the title Schiff base mol­ecule, C13H11ClN2O, the non-H atoms are approximately coplanar (r.m.s. deviation = 0.115 Å) and the two benzene rings are twisted by 9.36 (3)° with respect to each other. The hy­droxy group is hydrogen bonded to the azomethine N atom. In the crystal, an N—H⋯π inter­action is observed between the imino group and the hy­droxy­benzene ring of an adjacent mol­ecule.

In the title compound, C10H12ClN3OS, the –C=N–N–C– chain bridging the ethyl­imino group and the benzene ring adopts an extended conformation with a C—N—N—C torsion angle of −171.98 (11)°. The imino H atom of the chain is a hydrogen-bond donor to the S atom of an inversion-related mol­ecule, forming a supra­molecular dimer. The hy­droxy H atom is intra­molecularly hydrogen bonded to the azomethine N atom.

In the title co-crystal, [Mo(C14H9ClN2O4)O2(CH3OH)]·C10H8N2, the deprotonated Schiff base O,N,O′-chelates to the MoVI atom, the three atoms involved in chelation comprising the fac sites of the octa­hedron surrounding the methanol-coordinated metal atom. The methanol mol­ecule forms an O—H⋯N hydrogen bond to an N atom of the 4,4′-bipyridine solvent mol­ecule; the hy­droxy group of the Schiff base forms an O—H⋯N hydrogen bond to the other N atom of another mol­ecule. The two hydrogen bonds leading to the formation of a helical chain running along the b axis.

The MnIII atom in the title complex, [Mn(C18H18N2O4)(CHO2)(H2O)]·2H2O, is O,N,N′,O′-chelated by the deproton­ated Schiff base; the four chelating atoms form an approximate square, with the O atoms of the water mol­ecule and the formate ion in axial positions above and below the square plane. Two metal-bearing mol­ecules are linked by an O—Hwater⋯O hydrogen bond about a center of inversion, generating a hydrogen-bonded dinuclear species; adjacent dinuclear units are linked through the lattice water mol­ecules, forming a three-dimensional network.

The MoVI atom in the title co-crystal, [Mo(C14H12N2O4)O2(H2O)]·0.5C10H8N2, is O,N,O′-chelated by the deprotonated Schiff base and coordinated by the oxide and water O atoms in an octa­hedral geometry. The five-membered chelate ring is planar (r.m.s. deviation = 0.019 Å), but the six-membered chelate ring is puckered (r.m.s. deviation = 0.108 Å). Two mononuclear mol­ecules are linked across a center of inversion by an O—Hwater⋯O hydrogen bond; adjacent dinuclear units are linked by an water–4,4′-bipyridine O—H⋯N hydrogen bond, generating a linear chain structure. The 4,4′-bipyridine mol­ecule is disordered over two positions in a 1:1 ratio.

The SnIV atom in the title carboxyl­ate-bridged polymer, [Sn(C7H7)3(C9H7O2)]n, exists in a trans-C3SnO2 trigonal–bipyramidal geometry (average covalent Sn—O = 2.167 Å, average dative Sn—O = 2.361 Å and average O—Sn—O = 169.6°). The polymer propagates as a helical chain along the b axis with a repeat distance that is half the b-axial length. There are four independent formula units in the asymmetric unit; two are disposed about a false center of inversion with respect to the other two so that the space group emulates a centric space group.

The six-coordinate SnIV atom in the title compound, [Sn(C7H6F)2Cl2(C10H8N2)], shows a trans-C2SnN2Cl2 octa­hedral coordination [C—Sn—C = 174.81 (10) and 176.71 (9)° in the two independent mol­ecules in the asymmetric unit]; the Cl atoms are cis to each other as are the N atoms of the chelating N-heterocycle.

The six-coordinate SnIV atom in the title compound, [SnCl4(C14H14OS)2], exists in a cis-SnCl4O2 octa­hedral geometry. Of the four Cl atoms, two are close to adjacent S atoms [Cl⋯S = 3.320 (1) and 3.376 (1) Å]; the Sn—Cl bonds involving these two Cl atoms are longer than the other two Sn—Cl bonds.

In the title mol­ecule, [Sn(C7H6Cl)2(C6H4NO2)2(H2O)], the O atoms of the two chelating nicotinate groups and the O atom of the coordinated water mol­ecule comprise the penta­gonal plane of the trans-C2SnO5 penta­gonal–bipyramid [C—Sn—C = 178.62 (11) °] surrounding the SnIV atom. In the crystal, adjacent mol­ecules are linked by O—H⋯N hydrogen bonds, generating a chain running along the body diagonal of the triclinic unit cell.

The O-C6H4-CH=N–C6H4-O dianion of the title compound, [Mn(C13H9NO2)(C7H5O2)(C2H6OS)], acts as an O,N,O′-chelate to bind to the MnIII atom, and the three atoms constitute three points [O—Mn—O = 174.43 (11)°] of an octa­hedron around the metal atom. The azomethine linkage is disordered over two positions in a 0.657 (13):0.343 (13) ratio. The deprotonated salicyldehyde anion acts as an O,O′-chelate; the sixth coordination site is represented by the O atom of the dimethyl sulfoxide mol­ecule. The crystal studied was a non-merohedral twin with a minor twin component of 14.2 (3)%.

The dinuclear title complex, [Sn2(C7H6Cl)4(C9H16NO2S2)4], lies on a center of inversion. The SnIV atoms are chelated by one of the two carboxyl­ate ions; the other carboxyl­ate ion bridges two metal atoms. The geometry of the six-coordinate SnIV atom is a distorted trans-C2SnO4 octa­hedron [C—Sn—C = 155.32 (8)°].

The six-coordinate SnIV atom in the title compound, [Sn(C8H9)Cl3(C3H4N2)2], shows an octa­hedral coordination. The N atoms of the N-heterocycle are cis to each other. The Sn—N bond that is trans to the Sn—C bond is shorter than the Sn—N bond trans to the Sn—Cl bond. Weak N—H⋯Cl hydrogen bonds link adjacent mol­ecules, generating a double chain running along the c axis.