Synthesis, Characterization, and Solvatochromic Behavior of a Mixed-Chelate Copper(II) Complex

This study presents the design, synthesis, and characterization of a mixed-chelate copper(II) complex, [Cu(L)(acac)(ClO4)]ClO4, where L = 2-[(2-diisopropylamino-ethylamino)-methyl]-pyridine. Various analytical techniques, including elemental analysis, infrared (IR) spectroscopy, single-crystal X-ray diffraction, and molar conductivity measurements, were employed to elucidate the structural attributes of the complex, confirming its deviated square pyramidal geometry. Additionally, the solvatochromic behavior of the complex was investigated. The absorption spectrum revealed a broad, structureless band in the visible region, exhibiting a significant bathochromic shift (red shift) upon changing the solvent. This observation indicates a positive solvatochromic effect, which is ascribed to interactions between the solvent molecules and the weakly bound perchlorate anion in the coordination sphere of the complex. A statistical analysis utilizing the stepwise multiple linear regression (SMLR) method identified the Gutmann donor number (DN) of the solvent as the most influential factor in the observed solvatochromism. Specifically, an increase in the DN value corresponded to a red shift in the absorption of the complex spectrum, indicative of stronger interactions with donor solvents. These findings suggest the potential utility of this complex as a chromogenic sensor for assessing solvent polarity.