Investigate Solute-Solvent Interaction at Different Concentrations and Different Temperature of Substituted Pyrazole Ligands

The current study examines the solute–solvent and solute solute interactions of three substituted pyrazole ligands (BCHPP, CNHPP, and CCHPP) at different concentrations and temperatures in a 70% dioxane–water mixture. A pyknometer and an Ostwald viscometer were used to measure densities and viscosities, respectively. The Jones-Dole equation was used to analyze the data and determine the A- and B-coefficients. Increased solute–solvent interactions were confirmed by the relative viscosity rising with increasing ligand concentration. All ligands exhibit structure-breaking behavior in the mixed solvent system when their B-coefficients are negative. Thermodynamic parameters (ΔG, ΔH, and ΔS) that shed light on the energetics of ligand–solvent interactions were determined through temperature-dependent viscosity measurements. The results indicate that because of the nitro group's strong electron-withdrawing properties, CNHPP has the largest free energy change. Positive entropy values indicate spontaneous processes that are dominated by solvent structural reorganization. The type and degree of molecular interactions in substituted pyrazole ligand systems are generally revealed by viscosity and thermodynamic analyses.