Exploiting the INHIBIT-ESIPT mechanism for the design of fluorescent chemosensor with a large blue-shift in emission

Sulfonamides as Optical Chemosensors

Sulfonamides are auspicious chemosensors which are capable to bind with ionic species through various ways like complexation, charge transfer, proton transfer etc. and produce a detection signal in the form of an optical change either in visible or UV-light and for electronic as well as fluorimetric spectra. Sulfonamides have gained much attention of analytical chemists these days as these are inexpensive, robust, green in nature and some what sensitive and selective to many anionic and cationic species. Due to their promising versatility in sensing properties, these are under great consideration in forensic, environmental, analytical and biochemistry laboratories. This review narrates how sulfonamides are being used to optically sense ionic species.

A new highly selective “off–on” typical chemosensor of Al3+, 1-((Z)-((E)-(3,5-dichloro-2-hydroxybenzylidene)hydrazono)methyl) naphthalene-2-ol, an experimental and in silico study

A new promising fluorescent chemosensor based on a 2-hydroxynaphthaldehyde skeleton was successfully synthesized through double imine formation as a yellow solid with an overall chemical yield of 63%. The compound showed UV/Visible maxima of at 394 nm in DMSO. Based on spectroscopic data of FTIR, ToF-HRMS, ¹H-NMR, and ¹³C-NMR, the product was characterized as 1-((Z)-((E)-(3,5-dichloro-2-hydroxybenzilydine)hydrazono)methyl)naphthalene-2-ol. Upon experimental study, the compound was confirmed as a highly selective and reversible off–on typical chemosensor against Al³⁺ with an emission quantum yield of 0.203 ± 0.009. The Job's plot analysis revealed that a highly stable 1:1 complex was formed with an association constant of 8.73 × 10⁵ M⁻¹. A pH-dependent study showed that the sensor was potentially applicable at physiological conditions (pH 7–8) in a mixture of DMSO : H₂O (99 : 1, v/v). The LoD and LoQ of the chemosensor towards Al³⁺ in DMSO were found to be 0.04 and 0.14 μM respectively. Based on DFT and TD-DFT calculation (B3LYP hybrid method/basis set of 6-311+G(d,p)), the sensing mechanism of the chemosensor to the ion was discovered as inhibition of excited-state intramolecular proton transfer (ESIPT).

A new promising fluorescent chemosensor of Al³⁺ based on a 2-hydroxynaphthaldehyde skeleton was successfully synthesized through double imine formation and demonstrated excellent sensing properties through the ESIPT inhibition mechanism.

Cascade recognition of Hg2+ and cysteine using a naphthalene based ESIPT sensor and its application in a set/reset memorized device

An optical ESIPT sensor for Hg²⁺ and cysteine based on a naphthalene platform (1) was designed and synthesized by a one step reaction and characterized by using common spectroscopic techniques.

Synthesis, fluorescence-sensing and molecular logic of two water-soluble 1,8-naphthalimides

Two novel highly water-soluble fluorescence sensing 1,8-naphthalimides are synthesized and investigated. The novel compounds are designed on the "fluorophore-receptor₁-spacer-receptor₂" model as a molecular fluorescence probe for determination of cations and anions in 100% aqueous media. The novel probes comprising N-imide and N-phenylpiperazine or morpholine substituents are capable to operate simultaneously via ICT and PET signaling mechanism as a function of pH and to recognize selectively Cu²⁺ and Hg²⁺ over the other representative metal ions. Due to the remarkable fluorescence changes in the presence of protons, hydroxyl anions, Hg²⁺ and Cu²⁺, INH and doubly disabled INH logic gates are executed and the systems are able to act as a single output combinatorial logic circuit with four chemical inputs.