Unusual solvatochromism of the 4,4′‐bis(dimethylamino)benzophenone (Michler's ketone)–tetracyanoethene electron donor–acceptor complex

Abstract

The transition energy of the charge-transfer UV/Vis absorption maxima (# max, CT ) and the structure of the Michler's ketone (MK)-tetracyanoethene (TCNE) electron donor-acceptor (EDA) complex are remarkably solvent dependent. The UV/Vis spectra of the MK-TCNE complex were measured in 20 non-protic and seven protic solvents. In non-protic solvents, # max, CT of the EDA complex is quantitatively described by a multiple LSE relationship using the Kamlet-Taft dipolarity/polarizability (p*) and basicity (b) parameters of the solvents. The influence of the two terms b and p* on # max, CT is opposite, indicating a qualitatively different solvent-induced stabilization of the electronic ground and excited states of the complex. As expected, increasing dipolarity/ dipolarizability of the solvent causes a bathochromic band shift (positive solvatochromism), whereas the basicity of solvents is responsible for a hypsochromic band shift due to specific solvation of the TCNE site. In protic solvents, the complex formation is associated with the formation of an ionic species (n max = 19 800 cm À1 ) derived from Michler's ketone due to coordination of TCNE at the carbonyl oxygen of MK (called an n-complex). The solvent-induced switching of the p-complex into the n-complex is demonstrated for mixtures of DCE with protic solvents and for silica surfaces.

Synthesis and Antibacterial Studies of Metal Complexes of Cu(II), Ni(II) and Co(II) with Tetradentate Ligand

“…In recent times, transition metal complexes of Schiff base ligands have gained considerable attention, not only due to their spectroscopic properties and applications [2] but also due to their remarkable antifungal, antibacterial and antitumor activities [3]. Schiff bases have a vital position in metal coordination chemistry even almost a century since their discovery.…”

Principles and Applications of Solvatochromism

“…The Z-scale is strongly correlated with the E T (30) scale. Other interesting solvatochromic probes that hav e been investigated in clud e Michler's ketone (charge transfer ab-sorption), 62 Nile red, 63 phenol blue, 64 and dithienyl polyenes. 65 Inorganic Dyes.…”

Coordination compounds of some transition metal ions with new Schiff base ligand derived from dibenzoyl methane. Structural characterization, thermal behavior, molecular structure, antimicrobial, anticancer activity and molecular docking studies

“…Their complexes attracted the attention of many researchers as they had high stability in different oxidation states resulting in their wide range of application such as applications in the biological, analytical, clinical, and industrial areas . Metal complexes of Schiff base ligands have gained considerable attention as the results of their spectroscopic properties and remarkable antifungal, antibacterial and antitumor activities applications . Nowadays Schiff bases are considered privileged ligands due to their ability to stabilize many different metals in various oxidation states, controlling the performance of metals in a large variety of useful applications in industrial fields together with their important roles in catalysis and organic synthesis …”