Abstract
Two penta-coordinated [Co((BPT)-B-Morph)Cl-2]; 1 and [Co((BPT)-B-Pip)Cl-2]; 2 complexes with the bis-pyrazolyl-s-triazine pincer ligands (BPT)-B-Morph and (BPT)-B-Pip were synthesized and characterized. Both (BPT)-B-Morph and (BPT)-B-Pip 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 horizontal ellipsis H, C-H horizontal ellipsis pi, and Cl horizontal ellipsis C (anion-pi stacking) interactions in addition to O horizontal ellipsis 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 (BPT)-B-Morph and (BPT)-B-Pip, 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.