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The title compound C13H12N4OS (I) is synthetized from isonicotinic hydrazide and isothiocynate. Compounds C13H11N4OCl (II) and C13H10N4S (III) where obtained upon reaction of (I) with Fe(II) or Mn(II) salts. Compound (II) is heterocyclic 1,3,4-oxadiazole while compound (III) is heterocyclic 1,2,4-triazole. The 1,3,4-oxadiazol derivative is almost planar with dihedral angle of 2.66 (8) and 5.14 (8)° between 1,3,4-oxadiazole ring and phenyl and pyridinium rings respectively; the dihedral angle between the phenyl and pyridinium rings is 3.92 (8)°. The 1,2,4-triazole derivative is non-planar. The phenyl and pyridyl rings form dihedral angles of 58.35 (5) and 58.33 (5)°, respectively, with the 1,2,4-triazole ring; the dihedral angle between the phenyl and pyridyl rings is 36.85 (4)°. In the compound (II) intramolecular hydrogen bonds of type N—H···Cl, C—H···N and C—H···Cl resulting in S(6) ring stabilize the structure. Intermolecular hydrogen bonds of type N—H···N, C—H···N, C—4···Cl link the molecule thus forming a three-dimensional network. In the structure of compound (III), intermolecular hydrogen bonds of type N—H···N, C—H···N, C—H···S1,link the monomer in a three-dimensional network.

In the title compound, [Tb(H2L)2(H2O)3].3Cl.4(H2O).(C2H5OH), the Tb3+ is nine-coordinated in a distorted monocapped square antiprismgeometry by four nitrogen atoms, two oxygen atoms from the ligand molecules of the tridentate N,N'-1,5-bis(pyridylmethylidene) carbonohydrazone) (H2L) and three oxygen atoms of coordinating water molecules. The structure of the complex was elucidated by X-ray diffraction analysis. Suitable crystals were grown by slow evaporation of ethanol solution. The compound crystallizes in the triclinic crystal system with a space group of Pī. The asymmetric unit of the compound contains two neutral ligand molecules, oneterbium ion, three coordinated water molecules, five and half uncoordinated water molecules and one uncoordinated ethanol molecule. In the crystal, the complex cations are linked by hydrogen bonds into layers. These layers, chloride anions and non-coordinating water molecules are connected by O—H···O, O—H···N, O—H···Cl, N—H···O, N—H···Cl and C—H···Cl hydrogen bonds into a three-dimensional structure.

The present investigation describes the synthesis and structural study of the ligand 2-((1H-imidazol-2-yl)methyleneamino)phenol, which was used to generate three dimensio-nal supramolecular complex formulated as {[Ni(HL)2]2.[Ni(H2L)2]2.(Cl)4.(H2O)5}. The title compound crystallizes in the orthorhombic space group Fddd with the following unit cell parameters: a = 13.9269(4) Å, b = 29.5295(16) Å, c = 43.1739(15) Å, V = 17755.5(12) Å3, Z = 8, R1 = 0.043 and wR2 = 0.129. For this compound, the structure reveals that one neutral mononuclear unit [Ni(HL)2] and one cationic mononuclear unit [Ni(H2L)2]2+. In the neutral unit, the organic molecule acts as a tridentate through one imino nitrogen atom, one nitrogen atom from the imidazole ring and one phenolate oxygen atom. In the cationic unit, it acts as tridentate through one imino nitrogen atom, one nitrogen atom from the imidazole ring and one oxygen atom of non-deprotonated phenol group. In both units the nickel(II) ion is hexacoordinated and the coordination environment can be described as distorted octahedral geometry. Numerous hydrogen bonds link the molecules into three dimensional network.

The use of 2-{[2-(2-hydroxybenzylideneamino)phenylimino]methyl}phenol (H2L) in metal transition chemistry has yielded a co-crystal which is composed by one neutral mononuclear, one cationic dinuclear and one perchlorate anion. During the formation of the complex, one of the salicylaldimine groups of one of the molecules of the H2L ligand hydrolyzed to form an asymmetrical ligand with an amino group leading to the molecule (2-((2-aminophenylimino)methyl)phenol (HL'). The complex was formulated as {[Cu(L)].[Cu2(L)(L')]}.(ClO4). The structure of the complex was solved by single crystal X-ray crystallography. In the mononuclear unit, the Cu2+ atom is coordinated by one dideprotonated molecule of the ligand acting in tetradentate fashion. In the dinuclear unit, one the Cu2+ atom is coordinated by one dideprotonated molecule of the ligand acting in tetradentate fashion and the other Cu2+ is coordinated by the monodeprotonated (2-((2-aminophenylimino)methyl)phenol (HL') acting in tridentate fashion. The two Cu2+ are bridged by the two phenoxo oxygen atoms of the dideprotonated molecule of the ligand. The complex crystallizes in the triclinic space group Pī with the following parameters: a = 13.8864 (3) Å, b = 14.2078 (4) Å, c = 14.5007 (4)) Å, α = 64.593 (3), β = 71.353 (2), γ = 71.707 (2)°, V = 2395.80 (13) Å3, Z = 2, R1 = 0.037, wR2 = 0.041. The supramolecular structures are consolidated by multiple hydrogen bonds.

Herein we reported the binuclear complexes of the 1-(pyridin-2-yl)-2-(pyridin-2-ylmethylene)hydrazine ligand (HL) [Ln2(HL)2(CH3COO)6].n(H2O) (Ln = Y, Pr, Gd and Er). The binuclear complexes are characterized by IR and physical measurement. Spectroscopic evidence indicated that the Schiff base HL behave an N3 coordination tridentate ligand. The complexes are formulated as [{Ln(1-(pyridin-2-ylmethylidene-kN)-2-(pyridin-2-yl-kN)hydrazine-kN1)(h2-OOCH3)2}{h1:h2:m2-OOCH3}2{Ln(1-(pyridin-2-ylmethylidene-kN)-2-(pyridin-2-yl-kN)hydrazine-kN1))(h2-OOCH3)2}].n(H2O). The structure of the praseodymium complex was elucidated by X-ray diffraction analysis. Suitable crystals were grown by slow evaporation of methanol solution. The asymmetric unit of the compound contains two neutral ligand molecules, two Pr3+ ions, four acetate anions acting in h2-OOCH3 mode, two acetate anions acting in h1:h2:m2-OOCH3 mode, and three uncoordinated water molecules. The praseodymium atom is ten coordinated and the coordination sphere is best described as a distorted bicapped square antiprism. The PrIII···PrIII distance is 4.2777(6) Å and the bridging angle Pr—O—Pr and O—Pr—O are respectively 115.8(3)° and 64.2(3)°. The structure is consolidated by intra and intermolecular hydrogen bond.

The use of N'–(1–(pyridin–2–yl)ethylidene)nicotinohydrazide (HL) in lanthanide(III) chemistry has yielded one mononuclear and one dinuclear complexes. The 1:1 Nd(NO3)3.6H2O or Pr(CH3COO)3.6H2O/HL in methanol afforded the complexes [Nd (HL)2(NO3)2(H2O)2].(NO3) (1) and {[Pr(L)(h2–OOCCH3)(H2O)](h1:h2:m–OOCCH3)2[Pr (L)(h2–OOCCH3)(H2O)]} (2). The structures of the complexes were solved by single crystal X–ray crystallography. In the mononuclear complex, the Nd3+ atom is coordinated by two neutral molecules of ligand acting in tridentate fashion, two nitrate anions acting in bidentate manner and two coordinated water molecules yielding a twelve–coordinated Nd atom. In the complex (2) the Pr3+ atoms are doubly bridged by two acetates anions and each metal ion is coordinated by one tridentate monodeprotonated molecule ligand, one bidentate acetate group and one coordinated water molecule. Each Pr3+ atom is nine–coordinated with an environment best described as a tricapped prismatic geometry. Complex 1 crystallizes in the monoclinic space group C2/c with the following parameters: a = 22.7657(8) Å, b = 8.4276(3) Å, c = 18.0831(7) Å, b = 114.851(2)°, V = 3148.2(2) Å3, Z = 4, R1 = 0.032, wR2 = 0.098. Complex 2 crystallizes in the monoclinic space group P21/n with the following parameters: a = 11.5388(6) Å, b = 14.1087(8) Å, c = 12.2833(6) Å, b = 102.211(2)°, V = 1954.45(18) Å3, Z = 2, R1 = 0.029, wR2 = 0.066. The supramolecular structures are consolidated by multiple hydrogen bonds.