Aza-phenol Based Macrocyclic Probes Design for "CHEF-on" Multi Analytes Sensor: Crystal Structure Elucidation and Application in Biological Cell Imaging

Mohafuza Khatun; Pravat Ghorai; Jayanta Mandal; Sougata Ghosh Chowdhury; Parimal Karmakar; Salvador Blasco; Enrique García-España; Amrita Saha

doi:10.1021/acsomega.2c06549

Aza-phenol Based Macrocyclic Probes Design for "CHEF-on" Multi Analytes Sensor: Crystal Structure Elucidation and Application in Biological Cell Imaging

ACS Omega. 2023 Feb 13;8(8):7479-7491. doi: 10.1021/acsomega.2c06549. eCollection 2023 Feb 28.

Authors

Mohafuza Khatun¹, Pravat Ghorai¹, Jayanta Mandal¹, Sougata Ghosh Chowdhury², Parimal Karmakar², Salvador Blasco³, Enrique García-España³, Amrita Saha¹

Affiliations

¹ Department of Chemistry, Jadavpur University, Kolkata 700032, India.
² Department of Life Science and Biotechnology, Jadavpur University, Kolkata 700032, India.
³ Institute of Molecular Sciences, Universitat de València, C/Catedrático José Beltrán Martínez, 2, Paterna, Valencia 46980, Spain.

Abstract

Metal bound macrocyclic compounds found in biological systems inspired us to design and synthesize two Robson-type macrocyclic Schiff-base chemosensors, H ₂ L1 (H ₂ L1=1,11-dimethyl-6,16-dithia-3,9,13,19-tetraaza-1,11(1,3)-dibenzenacycloicosaphane-2,9,12,19-tetraene-1,11-diol) and H ₂ L2 (H ₂ L2=1,11-dimethyl-6,16-dioxa-3,9,13,19-tetraaza-1,11(1,3)-dibenzenacycloicosaphane-2,9,12,19-tetraene-1,11-diol). Both the chemosensors have been characterized with different spectroscopic techniques. They act as multianalyte sensor and exhibit "turn-on" fluorescence toward different metal ions in 1X PBS (Phosphate Buffered Saline) solution. In presence of Zn²⁺, Al³⁺, Cr³⁺ and Fe³⁺ ions, H ₂ L1 exhibits ∼6-fold enhancement of emission intensity, while H ₂ L2 shows ∼6-fold enhancement of emission intensity in the presence of Zn²⁺, Al³⁺ and Cr³⁺ ions. The interaction between the different metal ion and chemosensor have been examined by absorption, emission, and ¹H NMR spectroscopy as well as by ESI-MS⁺ analysis. We have successfully isolated and solved the crystal structure of the complex [Zn(H ₂ L1)(NO₃)]NO₃ (1) by X-ray crystallography. The crystal structure of 1 shows 1:1 metal:ligand stoichiometry and helps to understand the observed PET-Off-CHEF-On sensing mechanism. LOD values of H ₂ L1 and H ₂ L2 toward metal ions are found to be ∼10^-8 and ∼10^-7 M, respectively. Large Stokes shifts of the probes against analytes (∼100 nm) make them a suitable candidate for biological cell imaging studies. Robson type phenol based macrocyclic fluorescence sensors are very scarce in the literature. Therefore, the tuning of structural parameters as the number and nature of donor atoms, their relative locations and presence of rigid aromatic groups can lead to the design of new chemosensors, which can accommodate different charged/neutral guest(s) inside its cavity. The study of the spectroscopic properties of this type of macrocyclic ligands and their complexes might open a new avenue of chemosensors.