The compounds (E)-2-amino-N'-(1-(2-hydroxyphenyl)ethylidene)-2-oxoacetohydrazide (I) and (E)-N'-(2hydroxy-3-methoxybenzylidene)-2-amino-2-oxoacetohydrazide (II) were synthetized by the 1:1 ratio condensation reaction of oxamic hydrazide and 2-hydroxyacetophenone or o-vanillin respectively. The two compounds were characterized by physico-chemical analyses, elemental analysis, FTIR, 1 H and 13 C NMR spectroscopies techniques. The structure of the compound (I) was determined by single-crystal X-ray diffraction study. The compound (I) (C 10 H 11 N 3 O 3 ) crystallises in the triclinic space group P-1 with the following unit cell parameters:
The use of 1,5-bis (phenyl (pyridin-2-yl) methylene) carbonohydrazide (H 2 L) in the coordination chemistry of lanthanides (III) yielded complexes in which two ligand molecules are present. The synthesis was carried out using a Ln/H 2 L ratio of 1/2 to lead mononuclear complexes of [Ln(H 2 L) 2 (η 2 -NO 3 ) 3-x ](NO 3 ) x (Ln=La (1), Sm (4), Gd (6) and Yb (7)), [Ln(H 2 L) 2 (NO 3 ) 3 ] (Ln=Pr(2), Eu(5) and a co-crystal {[Nd(H 2 L) 2 (η 2 -NO 3 ) 2 (η 1 -NO 3 )], [Nd(H 2 L) 2 (η 2 -NO 3 )(h 1 -NO 3 )(H 2 O)]} . (NO 3 ) . 2CH 3 OH} (3). The structures of the complexes (2) and (3)were solved by X-ray crystallography on a single crystal. In the mononuclear complex of Pr III , two neutral ligand molecules act in tridentate fashion. In the co-crystal complex, one of the Nd III atom is coordinated by two ligand molecules acting tridentately in neutral form and three nitrate anions acting in bidentate fashion while the second Nd III atom is coordinated by two ligand molecules acting tridentately in neutral form, one monodentate nitrate anion, one bidentate nitrate anion and one water molecule. The neutrality of the complex is ensured by one free nitrate anion. Two free methanol molecules are present. Complex (2) crystallizes in the triclinic space group P-1 with the following parameters: a=10.128 (2) Å, b=12.2285 (19) Å, c=20.816 (5) Å, α=85.634 (4), β=81.870 (4)°, γ=87.210 (5)°, V=2542.9 (9) Å 3 , Z=2, R 1 =0.0640, wR 2 =0.1377. Complex (3) crystallizes in the monoclinic space group P2 1 /c with the following parameters: a=10.4554 (12) Å, b=44.089 (6) Å, c=23.212 (3) Å, β=90.851 (2)°, V=10699 (2) Å 3 , Z=4, R 1 =0.0630, wR 2 =0.1690. The coordination sphere of the twelve-coordinated Pr III atom is best described as distorted icosahedron. In the co-crystal one of the Nd III atom is eleven-coordinated while the second Nd III atom is ten-coordinated. The environments around the Nd III atoms are respectively best described as distorted pentacapped trigonal prism and a distorted bicapped square antiprism, respectively. Supramolecular structures are consolidated by numerous hydrogen bonds.
Following the discovery of an unprecedented transamination reaction between primary alkylamines and a quinonoid molecule of the type C6H2(NHCH2R)2(=O)2 (I), obtained from commercially available diaminoresorcinol.2HCl, we have extended this method to the use of primary arylamines and found that, in contrast, secondary amines led to a different outcome. Whereas functionalized molecules of type I, which are best described as 6π +6π zwitterions, were obtained with aniline or 4-methoxyaniline, no transamination was observed with tBuNH2 in ethanol. However, a reaction which afforded salt 2-methylpropan-2-aminium 4-(methylamino)-3,6-dioxocyclohexa-1,4-dien-1olate (2b) took place in water and resulted from hydrolysis of the imine group and deprotonation of 5-hydroxy-2-(methylamino)-4-(methylimino)-cyclohexa-2,5-dienone (1a). Under similar conditions, secondary amines led to comparable results. The cations associated with the anionic quinonoid are readily exchanged in the presence of a primary amine. Whereas for the transamination reaction, basic amines react under mild conditions, slightly harsher conditions are needed for less basic amines such as piperidine, diisopropylamine, or diethylamine. Transamination reactions were also performed with 5-hydroxy-2-(methylamino)-4-(methylimino)-cyclohexa-2,5-dienone (1a), which is more soluble in organic solvents than 2-amino-5-hydroxy-4-iminocyclohexa-2,5-dienone (compound I) This led to the first examples of quinonoidal zwitterions functionalized with different alkyl groups on the nitrogen atoms. A number of compounds were characterized by X-ray diffraction, which allowed a better understanding of their electronic situation, and in many cases, the presence of multiple hydrogen-bond donors and acceptors results in crystal packings dominated by these interactions.
The present investigation describes the synthesis and structural study of the ligand N'-(phenyl(pyridin-2-yl)methylene)nicotinohydrazide (HL), which was used to generate two type complexes formulated as [Ln(HL)2(NO3)2(H2O)].(NO3) (Ln = La (1) and Pr (2)) and [Ln(HL)2(NO3)(H2O)2].(NO3)2 (Ln = Nd (3), Sm (4), Gd (5) and Tb (6)). The ligand and the complexes are characterized by NMR, UV-Visible and FTIR spectroscopies, conductivity measurements and room temperature magnetic moment measurements. The [La(HL)2(NO3)2(H2O)].(NO3) compound crystallizes in the orthorhombic space group Pbcn with the following unit cell parameters: a = 16.8634(8) Å, b = 8.0615(4) Å, c = 30.2833(15) Å, V = 4116.8(3) Å3, Z = 8, R1 = 0.049 and wR2 = 0.120. The structure reveals that two neutral ligand molecules in η3-mode, two bidentate nitrate groups in η2-mode and one water molecule coordinate the central La3+. Each organic molecules acts through one carbonyl oxygen atom, one azomethine nitrogen atom and one nitrogen atom from a pyridine ring. The lanthanide ion has a coordination number of 11 and the coordination environment can be described as distorted pentacapped trigonal prism. Numerous hydrogen bonds link the molecules into three-dimensional network.
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