Syntheses and Structural Investigations of Penta-Coordinated Co(II) Complexes with Bis-Pyrazolo-S-Triazine Pincer Ligands, and Evaluation of Their Antimicrobial and Antioxidant Activities

Abstract

Two penta-coordinated [Co(MorphBPT)Cl2]; 1 and [Co(PipBPT)Cl2]; 2 complexes with the bis-pyrazolyl-s-triazine pincer ligands MorphBPT and PipBPT were synthesized and characterized. Both MorphBPT and PipBPT act as NNN-tridentate pincer chelates coordinating the Co(II) center with one short Co-N(s-triazine) and two longer Co-N(pyrazole) bonds. The coordination number of Co(II) is five in both complexes, and the geometry around Co(II) ion is a distorted square pyramidal in 1, while 2 shows more distortion. In both complexes, the packing is dominated by Cl…H, C-H…π, and Cl…C (anion-π stacking) interactions in addition to O…H interactions, which are found only in 1. The UV-Vis spectral band at 564 nm was assigned to metal–ligand charge transfer transitions based on TD-DFT calculations. Complexes 1 and 2 showed higher antimicrobial activity compared to the respective free ligand MorphBPT and PipBPT, which were not active. MIC values indicated that 2 had better activity against S. aureus, B. subtilis, and P. vulgaris than 1. DPPH free radical scavenging assay revealed that all the studied compounds showed weak to moderate antioxidant activity where the nature of the substituent at the s-triazine core has a significant impact on the antioxidant activity.

A Novel Na(I) Coordination Complex with s-Triazine Pincer Ligand: Synthesis, X-ray Structure, Hirshfeld Analysis, and Antimicrobial Activity

“…The bpmt ligand can be easily prepared with a high yield, and it is classified as a tridentate N-pincer ligand with different coordination behaviors. In addition, its metal complexes exhibit remarkable biological activities compared to the free bpmt ligand [4,48,[51][52][53]55,56,58]. The pincer complexes of bpmt are stable and can be simply synthesized via the self-assembly of the functional ligand (bpmt) with a metal salt [54,57].…”

A New 1D Ni (II) Coordination Polymer of s-Triazine Type Ligand and Thiocyanate as Linker via Unexpected Hydrolysis of 2,4-Bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine

“…In our previous work with s-triazine pincer ligands comprising two pyrazolyl arms, we reported the molecular and supramolecular structures of different metal pincer complexes with a bis-pyrazolyl-s-triazine ligand [3,6,20,[23][24][25][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Many homoleptic and heteroleptic complexes of this type with pincer ligands and divalent and trivalent metal ions were reported to have coordination numbers ranging from five to eight.…”

“…It is noted that the coordination behavior of the pincer bis-pyrazolyl-s-triazine ligand (BPT) depends on many factors, such as the type of metal ion, reaction conditions such as medium and temperature, as well as the nature of the counter anion. In the majority of cases, the discrete pincer complexes of the bis-pyrazolyl-s-triazine ligand were obtained [3,6,20,[23][24][25]29,30,[34][35][36][37][38]41,42]. In some instances, the ligand underwent hydrolysis, either catalyzed by the medium acidity of an external acid [31] or by the Lewis acidity of the metal ion [23,[31][32][33].…”

“…Many homoleptic and heteroleptic complexes of this type with pincer ligands and divalent and trivalent metal ions were reported to have coordination numbers ranging from five to eight. 2,4-Bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine is an interesting N-pincer ligand that continues to receive the interest of our research group (BPT; Figure 1) and was used for the synthesis of a large number of polymeric and discrete metal (II) complexes [29][30][31][32][33][34][35][36][37][38][39][40][41][42]. It is noted that the coordination behavior of the pincer bis-pyrazolyl-s-triazine ligand (BPT) depends on many factors, such as the type of metal ion, reaction conditions such as medium and temperature, as well as the nature of the counter anion.…”

Deciphering the Mechanism of MRSA Targeting Copper(II) Complexes of NN2 Pincer-Type Ligands

“…Furthermore, the utilization of pincer complexes has risen during the past few years in different fields due to their unique orientation and stability. , Many pincer complexes are employed with different transition metals such as Au, Pt, Cu, Co, Fe, Ni, Mn, Pd, V, and Zn for their excellent antimicrobial activity. − Among them, copper complexes always showed enhanced activity. − Consider a copper pincer complex with a pyridine-based tridentate acyclic ligand that exhibited good activity against fungus and bacteria [zone of inhibition (ZoI), Candida albicans (C. albicans), 20 mm/mg] .…”