A simple structural hydrazide-based gelator as a fluoride ion colorimetric sensor

Abstract

A 4-nitrobenzohydrazide derivative, N-(3,4,5-octyloxybenzoyl)-N'-(4'-nitrobenzoyl)hydrazine (C8), was synthesized. It could form stable gels in some of the tested organic solvents. The wide-angle X-ray diffraction analysis showed that the xerogels exhibited a layered structure. SEM images revealed that the molecules self-assembled into fibrous aggregates in the xerogels. FT-IR studies confirmed that the intermolecular hydrogen bonding between C=O and N-H groups was the major driving force for the formation of self-assembling gel processes. The gel is utilized for a 'naked eye' detection of fluoride ions, through a reversible gel-sol transition, which is associated with a color change from colorless to red. An extended conjugated system formed through the phenyl group and a five-membered ring based on intramolecular hydrogen bonding between the oxygen atom near the deprotonation nitrogen atom and the other NH, which is responsible for the dramatic color change upon addition of fluoride ions.

Anion response of dimeric hydrazide derivatives: Dependence on the nature of terminal substituents

“…7). So we can conclude that only a stable hydrogen-bond complex is produced in response to These results are also consistent with those of hydrazide derivatives C8 [17].…”

“…5). These results of the 1 H NMR upon the addition of F − are the same as that of hydrazide derivative C8 [17], it can be considered that the F − response mechanism of dimeric hydrazide derivatives is the same as that of the reported hydrazide derivatives, although the number of hydrazide groups is different. Upon the addition of the lower equiv.…”

“…F − , the base becomes very strong, and F − exhibits a large affinity toward H + , which induce the deprotonation of the complex to form the very stable [HF 2 ] − dimer. Meanwhile the chargetransfer [21] might result in a five-membered ring based on intramolecular hydrogen bonding between the oxygen atom nearby deprotonation nitrogen atom and the other NH could thus be formed [17].…”

“…Recently, we reported the anion responsive behavior of the 4-nitrobenzohydrazide derivative C8 (Scheme 1) (containing one hydrazide per molecule) and proposed the possible mechanism for the F − responsive process [17]. In order to study the influence of the number of hydrazide groups, we synthesized the dimeric 4-nitrobenzohydrazide derivative (containing two hydrazide groups per molecule) with more target sites for forming H-bond with anions, namely, 1,6-Bis[N-(4-nitrobenzoyl)-N′-(benzoyl-4′-oxy)hydrazine]hexane (N6).…”

Chromogenic and fluorescent ‘turn‐on’ chemodosimeter for fluoride based on a F–‐triggered cascade reaction

“…Over‐intake of fluoride can cause fluorosis and lead to nephrotoxic changes and urolithiasis in humans . Therefore, the development of novel chemosensors for the detection of fluoride ions , particularly sensors with interesting sensing mechanisms , has currently attracted much attention in supramolecular chemistry. Besides the conventional fluoride–hydrogen bonding and deprotonation approaches, recently, the most popular strategy has been to utilize the high affinity of fluoride for silica for the construction of sensors with Si–O or Si–C bonds .…”