Synthesis, structural and biological studies of two new Co(III) complexes with tridentate hydrazone ligand derived from the antihypertensive drug hydralazine

Methylene spacer regulated variation in molecular and crystalline architectures of cobalt(iii) complexes with reduced Schiff base ligands: a combined experimental and theoretical study

Two heteronuclear cobalt(iii)/sodium complexes, [(H₂O)₂Co(H₂L¹)Na(N₃)₂] (1) and (μ-N₃)₂[(N₃)Co(H₂L²)Na]₂ (2) have been synthesized by the reaction of two compartmental reduced Schiff bases, H₂L¹ [(1,2-propanediyl)bis(iminomethylene)bis(6-ethoxyphenol)] and H₂L² [(2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-ethoxyphenol)], with cobalt(ii) nitrate hexahydrate in methanol. Structures of both the complexes have been confirmed by single crystal X-ray diffraction analysis. In each complex, cobalt(iii) is located in the inner N₂O₂ compartment and sodium is placed in the outer O₂O'₂ compartment of the respective ligands. In complex 1, the saturated five-membered chelate ring assumes a half-chair conformation, thereby facilitating the anti-orientations of two N-H bonds, which in turn favours the formation of very strong hydrogen bonds forming an infinite one-dimensional assembly. Formation of this one-dimensional chain is also supported by C-Hπ (arene) interactions. On the other hand, the best hydrogen bond donor NH groups are in syn disposition (as the saturated chelate ring is six-membered and assumes a chair conformation) and do not participate in the crystal packing in complex 2. However, very strong C-Hπ(N₃) interactions have been established in complex 2, where the π-system of the bridging azide ligand participates as the π-donor. A search in the Cambridge structural database (CSD) has also been carried out to investigate the abundance and directionality of the interaction using different pseudohalides. Energies of all these supramolecular interactions were estimated by DFT calculations including Grimme's dispersion correction and characterized by the NCI plot index computational tool.

Microwave Irradiation Assists the Synthesis of a Novel Series of bis-Arm s-Triazine Oxy-Schiff Base and Oxybenzylidene Barbiturate Derivatives

A novel series of s-triazines incorporating 4-hydroxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde was prepared and fully characterized. The reaction was carried out via stepwise nucleophilic aromatic substitution of chlorine atoms in cyanuric chloride. The first chlorine was substituted by different amines (morpholine, piperidine, or diethylamine) to afford 2,4-dichloro-6-substituted-1,3,5-triazine. The second and third chlorines were substituted by benzaldehyde derivatives in the presence of Na₂CO₃ as a HCl scavenger to afford the target products: s-triazine oxyaldehyde derivatives (dipodal). The dipodal derivatives were reacted with acid hydrazide, hydralazine, barbituric, or thiobarbituric acid derivatives using conventional heating or microwave irradiation to afford the di-arm s-triazine oxy-Schiff base and oxybenzylidene barbiturate derivatives in good yields. Microwave irradiation done in less solvent afforded the target product in less reaction time with good yield and purity. These types of derivatives might have special interest in coordination and medicinal chemistry.

Heteronuclear cobalt(iii)/sodium complexes with salen type compartmental Schiff base ligands: methylene spacer regulated variation in nuclearity

Three unique heteronuclear cobalt(iii)/sodium Schiff base complexes have been synthesized and characterized. Nuclearity of these complexes changes as a result of alteration of the steric hindrance in the ligand moiety.