Novel half-sandwich ruthenium(II) nicotinic hydrazone complexes: An efficient class of catalyst for the N-alkylation of amines with benzyl alcohol via transfer hydrogen mechanism and effective antibacterial agents

• Published in: Journal of molecular structure 2024-08, Vol.1309, p.138179, Article 138179
• Main Authors: Gunasekaran, Jayapratha, Muthuselvan, Sudha, Annadurai, Dhivya, Christopher Leslee, Denzil Britto, Venkatesan, Narmatha, Murthy, Sangeetha, Ramasamy, Balagurunathan, Alves, Luis G., Martins, Ana M., Kuppannan, Shanmuga Bharathi
• Format: Article
• Language: English
• Subjects: Antibacterial activity; N-alkylation; Nicotinic hydrazone; Ruthenium complex; Schiff base; Transfer hydrogen methodology
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2024.138179

•Novel half-sandwich Ru(II) nicotinic hydrazone complexes.•N-alkylation of amine using benzyl alcohol through transfer hydrogen mechanism.•Effective N-alkylation of amine against a wide range of substrates that includes anilines bearing electron withdrawing/electron donating group, fused aromatic, heteroaromatic, alicyclic and aliphatic amines.•Efficient antibacterial activity against both gram positive (S. aureus and E. faecalis) and gram negative bacteria (E. coli and K. pneumoniae). A new series of half sandwich ruthenium(II) complexes supported by nicotinic acid hydrazone derivatives of general formula [Ru(ɳ6-p-cymene)(Cl)(L)], where L represents N’-benzylidenenicotinohydrazide (HL1), N’-(naphthalen-1-ylmethylene)nicotinohydrazide (HL2) or N’-(pyren-1-ylmethylene)nicotinohydrazide (HL3) were synthesized and fully characterized. The solid-state molecular structures of ligands and complexes were elucidated with single-crystal X-ray diffraction. The ligands HL1 and HL2 possess monoclinic crystal system with P21/c and C2/c space groups respectively, whereas all the three Ru(II) complexes C1–3 are typical three-legged piano-stool geometries with orthorhombic(Aba2) (C1) and triclinic(P-1) (C2–3) systems respectively. The catalytic activities of these ruthenium complexes in the synthesis of N-alkylated amines were explored. Under optimal reaction condition, the complex C3 was found to be the most efficient catalyst for the N-alkylation of primary to secondary amines using benzyl alcohol. A wide range of substrates have been studied that includes anilines bearing electron withdrawing/electron donating group, fused aromatic, heteroaromatic, alicyclic and aliphatic amines with good to excellent yield. In addition, the antibacterial activity of the complexes were tested against different human pathogenic bacteria, among them C2 complex with naphthyl moiety was found to be the most active one against both Gram-positive (S. aureus and E. faecalis) and Gram-negative (E. coli and K. pneumoniae) bacteria. These two different studies demonstrate the catalytic and biological importance of our newly prepared Ruthenium complex. Novel Ruthenium nicotinic hydrazone series of complexes were successfully prepared. [Ru(ɳ6-p-cymene)(Cl)(L)](C3) complex has showed excellent catalytic activity in N-alkylation of amines through transfer hydrogenation. In addition, these complexes have also demonstrates good antibacterial activities against gram positive and gram negative bacteria.