solvatochromism

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.

The synthesis and characterization of a dinuclear [LCu(m-OH)2CuL](ClO4)2, complex with a tridentate N,N-diisopropyl,N'-3-propylamide-ethylenediamine hemilabile ligand (abbreviated L) is reported. The dinuclear complex was characterized by elemental analysis, molar conductance, thermal analysis, and spectral studies. In the complex, both copper centers are 5-coordinated and bridged through two hydroxo groups.  Thermo- and solvatochromic behaviors of the complex were investigated by visible spectroscopy. Its reversible thermochromism (blue ↔ green) in acetonitrile solution is due to dissociation and re-coordination of Cu-O(amide) moiety. The solvent-dependent absorption maxima, lmax, was studied by a Stepwise Multiple Linear Regression (SMLR) analysis to determine the best model describing the resulting positive solvatochromism.  The statistical results demonstrated that among different solvent parameters, Donor Number (DN) is a dominant parameter that is responsible for the redshift in the d-d absorption band of the complex by increasing its values.

Three new heteroleptic copper(II) complexes, [(tmen)Cu(dike)H2O]X where tmen = N,N,N',N'-tetramethylethylenediamine, dike = 2-acetylcyclopentanone anion and X= ClO4- (1), Cl- (2) and Br- (3) are prepared and characterized by elemental analyses, molar conductance measurements and IR and UV-Vis spectroscopy techniques. The complex 1 is fairly soluble in various organic solvents and demonstrates distinctive solvatochromism. However, the solubility of complexes 2 and 3 is less than 1 and their color changes are limited to polar solvents. The influence of the solvent polarity and counter ions on the wave length maxima, max values of the d-d bands of the complexes have been investigated by visible spectroscopy. A multi-parametric equation has been utilized to explain the solvent effect on the d-d transition of [(tmen)Cu(dike H2O)]ClO4 using SPSS/PC software. The stepwise multiple linear regression (SMLR) method demonstrated that the donor power of the solvent plays the most important role in the observed negative solvatochromism of the compound.

Bicyclic aziridines show exclusive photochromic behavior. Here, we summarize the results of optical and electrochemical properties, such as photochemical, solvatochromic, electrochromic andkinetic behavior of bicyclic aziridines linked to chalcone moieties. The photochromic process for conversion of closed photoisomers to open photoisomers for compounds 1-10 followed zero-order kinetics. For considering the solvatochromic properties of compounds 1,3,5,7 and 9, photochromic properties of these compounds in different solvents were investigated and the negative solvatochromism were observed. The redox behavior of several derivatives of bicyclic aziridines by cyclic voltammetry was examined for compounds 1,3,5 and 6, and irreversible oxidation was observed.