Deciphering the Interaction of a Macrocyclic Tetranuclear Zn(II) complex with Biomimicking Surfactant: A Case Study using Cetyltrimethylammonium Bromide

Abstract

The detection of various biologically important cationic and anionic species has led to the synthesis of various Zinc (II) Schiff base complexes, which bear a large application in catalysis and sensors. A recently reported study has indicated a synthesis of a 48 membered macrocyclic Zn(II) Schiff base complex, which functions as a dual anion sensor (DAS) containing a protonated amine group. In the present investigation, an attempt has been made to study the interaction of the Zn tetranuclear complex (Zn-TCom), a neutral complex, with a cationic surfactant cetyltrimethylammonium bromide (CTAB), employing steady-state absorption and fluorescence studies. The change in the photophysical properties of the fluorophore is studied on binding with the surfactant. The steady-state absorption and emission studies reveal that the polarity of the surrounding of the fluorophore has been modified upon binding with CTAB. A study on the alteration of polarity during the interaction of Zn-TCom with the surfactant is studied by comparing the fluorescence behavior of the probes in a micro heterogeneous environment in a mixture of dioxane and water of varying composition. The binding constant magnitude (analyzed using the Hildebrand equation) manifests that the Schiff base binds to the micellar compartment. These results are manifested to enhance the potential application of the macrocyclic complex in the field of biochemistry. Furthermore, quantum chemical calculations are undertaken to correlate the molecular structure of Zn-TCom with the associated frontier molecular orbitals. The parameters like the energy of HOMO, LUMO and the associated Mulliken charges with respect to individual elements are computed using the single point geometry. The studied reports are correlated with the feasibility of binding with bio mimicking environment or bio proteins for selective application as drug carriers.