Issue 10, 2018

ESIPT-capable 2,6-di(1H-imidazol-2-yl)phenols with very strong fluorescent sensing signals towards Cr(iii), Zn(ii), and Cd(ii): molecular variation effects on turn-on efficiency

Abstract

A series of structurally and electronically varied 2,6-di(1H-imidazol-2-yl)phenols that are ESIPT-capable (1–12) as well as the ESIPT-incapable 4,5-diphenyl-2-(3-(4,5-diphenyl-1H-imidazol-2-yl)phenyl)-1H-imidazole (13) were designed and comparatively studied for their molecular effects on their sensitivity and selectivity characteristics as fluorescent chemosensors of Cr3+, Zn2+, and Cd2+. Their single-crystal structures revealed a desired chain of intramolecular hydrogen bonding (ligand 12) as well as possible coordination modes. Probes 1–4 demonstrated very high turn-on sensitivity and selectivity as double fluorescent sensors for Cr3+ and Zn2+ at their different emission wavelengths (blue-shifted in the case of Zn2+). A remarkable 106-fold emission turn-on by Cr3+ was recorded for molecule 2, which, to the best of our knowledge, is an unheard of magnitude for Cr3+ sensitivity. The results suggested that a Cd2+ sensor could be developed by further derivatization of these probes. The possession of symmetrical substitution on both imidazole rings, multiple active protons involved in hydrogen intramolecular bonding relays, and the consequent ESIPT capability of the studied molecules were found to be very beneficial to their successful outcomes as high fluorescent turn-on chemosensors. Modification of the sensor properties, such as sensitivity and selectivity, was achieved through substituent manipulations at certain peripheral positions. Thus, deliberate molecular derivatization was found to be a tool for manipulating the interference and selectivity profiles. The Job plot, single-crystal results, and sustained large Stoke's shift in the presence of Cr3+ suggest a one-pocket N^O coordination in a 1 : 1 stoichiometry rather than a binuclear N^O^N two-pocket coordination. Quantum mechanical calculations on the model structures suggested that the successful turn-on results may be associated with the coplanarity settings of the imidazole and phenol rings.

Graphical abstract: ESIPT-capable 2,6-di(1H-imidazol-2-yl)phenols with very strong fluorescent sensing signals towards Cr(iii), Zn(ii), and Cd(ii): molecular variation effects on turn-on efficiency

Supplementary files

Article information

Article type
Paper
Submitted
14 मार्च 2018
Accepted
09 अप्रैल 2018
First published
10 अप्रैल 2018

New J. Chem., 2018,42, 7884-7900

ESIPT-capable 2,6-di(1H-imidazol-2-yl)phenols with very strong fluorescent sensing signals towards Cr(III), Zn(II), and Cd(II): molecular variation effects on turn-on efficiency

A. O. Eseola, H. Görls, M. Bangesh and W. Plass, New J. Chem., 2018, 42, 7884 DOI: 10.1039/C8NJ01265B

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements