Synthesis, crystal structure, and BSA interaction with a new Co(II) complex based on 5-(trifluoromethyl)pyridine-2-carboxylic acid

Abstract

A new complex, Co(Htpc)₂(H₂O)₂ (1) (Htpc = 5-(trifluoromethyl)pyridine-2-carboxylic acid), has been synthesized and characterized by X-ray single-crystal diffraction, elemental analysis, infrared spectral analysis, and thermogravimetric analysis. Meanwhile, the optimized geometric structure of the ligand was determined using the M06-2X functional of density functional theory (DFT) with the 6-311 + G(d, p) basis set. The gap energies ΔE between the frontier molecular orbitals were computed in different solvent media (water, methanol and ethanol) using the time dependent density functional theory (TD-DFT)/M06-2X by applying the Polarizable Continuum Model (PCM). The coordination sphere around Co(II) is distorted octahedral with two chelating tpc^- ligands and two coordinated water molecules. Bovine serum albumin (BSA) binding properties of the ligand, CoCl₂·6H₂O and 1 were investigated by fluorescence and UV–Vis absorption spectroscopy, revealing 1 exhibits higher binding affinity with BSA than free ligand and CoCl₂·6H₂O. ΔG, ΔH and ΔS at 298 and 308 K manifested that van der Waals interactions and hydrogen bonds were the main forces in the binding process.

Graphical Abstract

Keywords:

• 5-(Trifluoromethyl)pyridine-2-carboxylic acid
• DFT
• TD-DFT
• crystal structure
• bovine serum albumin

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by the Scientific Research Foundation of Higher Education Institutions of Ningxia (No. NGY2017004), the National Natural Science Foundation of China (Nos. 21763022 and 50564043) and the Major Innovation Projects for Building First-class Universities in China's Western Region (No. ZKZD2017003).