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[Display omitted] • Novel three functionalized bromosulfonamide-based azomethine compounds have been synthesized and characterized. • Under daylight and UV light, fluorescent chemosensor and calorimetrically anion probing of Schiff bases were observed. • TAS experiments revealed that Schiff bases incorporated iodo atom naphthalene unit demonstrate ISC upon photoexcitation. In this work, we have experimentally synthesized bromosulfonamide-based azomethine compounds through the reaction of 4-bromobenzenesulfonamide with 2-hydroxy-5-iodobenzaldehyde, 2-hydroxy-5-nitrobenzaldehyde, and 2-hydroxy-1-naphthaldehyde. We have also characterized the molecular structure of the investigated compounds with MS, 1H NMR, FTIR and UV–vis spectra. Theoretically, using DFT and TD-DFT methods, we computed frontier molecular orbitals (FMOs) energies and UV–vis spectra as well. We have also obtained the electron localization function (ELF) maps to identify electrophilic substitution sites in the molecules and density of states (DOS) diagrams to show the composition of the fragment orbitals that contribute to the molecular orbitals. We have investigated steady-state absorption, emission features, and excited state dynamics to better understand the photophysical process of bromosulfonamide-based azomethines. It has been demonstrated that by adding a naphthalene unit, the absorption properties of azomethine into two branches. Besides, azomethine, including heavy iodo atoms, presents a slight decrement in the fluorescence intensity. According to thorough calculations of charge transfer dynamics using femtosecond transient absorption spectra, the bromosulfonamide-based azomethines with iodo atoms and incorporating naphthalene units exhibit an intersystem crossing mechanism following photoexcitation. The colorimetric response of the compounds in DMSO to the addition of the equivalent amount of anions (F−, Br−, I−, CN−, SCN−, ClO 4 −, HSO 4 −, AcO−, H 2 PO 4 −, N 3 − and OH−) was investigated. In this regard, while the addition of F−, CN−, AcO−, H 2 PO 4 − and OH− anions into the solution containing the compounds resulted in a significant color change, the addition of Br−, I−, SCN−, ClO 4 −, HSO 4 − and N 3 −anions resulted in no color change. [ABSTRACT FROM AUTHOR]

• Schiff Base with methoxy and both methoxy - bromine showed higher antioxidant activity. • All studied compounds are a colorimetric sensor for F−, CN−, AcO−, H 2 PO 4 − and OH− anions under UV lamp and daylight. • Performed fluorescence measurements showed that the compounds ligand and including NO 2 group showed emission signal. • The triplet state of studied compounds ligand and with methoxy and with NO 2 group individually is observed. In this study, a new series of Schiff base benzothiazole derivatives were synthesized and their structures were characterized by elemental analysis, FTIR, UV–VIS and NMR spectroscopy. The biological, sensory and photophysical properties of the benzothiazole derivatives were investigated. The sensing properties of the compounds were investigated UV–VIS spectroscopically, calorimetrically and theoretically. All compounds showed colorimetric, fluorometric and spectroscopic sensor properties for F−, CN−, AcO−, H 2 PO 4 − and OH− anions. Furthermore, DNA binding, DNA cleavage and antioxidant activities of compounds 1 - 4 were investigated. All compounds affected pBR322 DNA both hydrolytically and oxidatively, interacted with DNA in electrostatic mode, and also compounds 1 and 2 exhibited antioxidant activity close to standard BHT. In addition, the effects of electron donating and accepting substituents on the emission properties and charge transfer dynamics were investigated by fluorescence and femtosecond transient absorption spectroscopy measurements, respectively. According to fluorescence measurements, compounds 3 and 4 showed emission signal, while compounds 1 and 2 showed fluorescence quenching and weaker emission signal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel three functionalized 3-amino-4-hydroxybenzenesulfonic acid-based Schiff bases have been synthesized and characterized. • Schiff Base incorporated NO 2 unit showed low stability, high chemical reactivity and greater energy gain due to having smaller HOMO-LUMO energy gap. • The antioxidant activity of Schiff Base with methyl group is high compared to BHT and stable with increased concentration. • Schiff Base with heavy bromine atom has fluorescent sensor ability for F−, CN–, AcO−, H 2 PO 4 − and OH– anions at 254 nm. • Performed femtosecond transient absorption spectroscopy experiments revealed that Schiff bases incorporated NO 2 unit and bromine atom demonstrate intersystem crossing mechanism upon photoexcitation. A new series of aminobenzene sulfonic acid-based Schiff bases (1 – 3) were synthesized from the reaction of 3-amino-4-hydroxybenzenesulfonic acid with 5-methyl, 5-nitro and 5-bromo-salicylaldehyde. The colorimetric and UV–Vis spectroscopic responses of compounds in DMSO to addition of equivalent number of anions (F−, Br−, I−, CN–, SCN−, ClO 4 −, HSO 4 −, AcO−, H 2 PO 4 −, N 3 – and OH–) were investigated. Additionally, biological activities of the compounds; antimicrobial and DNA binding properties, were investigated. A DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) free radical method was used to measure antioxidant activity, and 4-hydroxy-3-(2-hydroxy-5-methylbenzylideneamino)benzene sulfonic acid (1) displayed greater antioxidant activity than butylated hydroxytoluene (BHT). Studied compounds demonstrated emission properties over a wide range of visible spectrum, and compound 4-hydroxy-3-(2-hydroxy-5-nitrobenzylideneamino)benzenesulfonic acid (2) has hypsochromic shift by incorporating NO 2 in comparison with other compounds. Femtosecond transient absorption spectroscopy measurements showed that compounds 4-hydroxy-3-(2-hydroxy-5-nitrobenzylideneamino)benzenesulfonic acid (2) and 3-(5-bromo-2-hydroxybenzylideneamino)-4-hydroxybenzenesulfonic acid (3) , incorporated nitro and bromine groups and possessing electron accepting features have fast triplet transition. This study provides a novel design strategy for biological activity and colorimetric probing features of aminobenzene sulfonic acid-based Schiff bases. [ABSTRACT FROM AUTHOR]

• Novel 2-formylbenzenesulfonic acid sodium salt based Schiff bases were synthesized. • Studied compounds were investigated spectroscopically and theoretically. • F − and CN− anions were colorimetrically sensed by studied compounds. • Schiff Base with chlorine group hydrolytically cleaved pBR322 DNA. • Schiff Bases can be used as antioxidants as they are more active than standard BHT. In this study, 2-formylbenzenesulfonic acid sodium salt-based Schiff bases were synthesized from the reactions of 2-formylbenzenesulfonic acid sodium salt with 2-amino-4-chlorophenol and 2-amino-4-methylphenol. The structure of the compounds was determined by FTIR, UV–Vis and NMR spectroscopy methods using both experimental and DFT methods. The anion sensor properties of the compounds were investigated both UV–Vis spectroscopically and calorimetrically. In addition, the antimicrobial activities, interactions with DNA, DNA cleavage and antioxidant activities of Schiff bases were investigated. Additionally, the effects of group electronegativity on the spectroscopic, biological, chromogenic sensing and optical properties of chlorine and methyl side groups and sodium 2-sulfobenzalidene-aminophenol-based Schiff bases were investigated. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, synthesis, spectroscopic, density functional theory (DFT) and photophysical studies of the three conjugated benzenesulfonamide Schiff bases were reported. We also calculated the energies of the frontier molecular orbitals (FMOs) and UV–Vis spectra of Schiff bases theoretically using the DFT and TD-DFT methods. Additionally, photophysical properties were investigated by UV–Vis and fluorescence spectroscopy techniques. The ground state interactions show that the absorption band has been separated into two branches and bathochromatically tuned to the visible region, and fluorescence intensity decreased in the case of the Schiff base incorporated naphthalene unit. Furthermore, the charge transfer dynamics of the compounds were analyzed using femtosecond transient absorption spectroscopy measurements proving the triplet-triplet transitions via intersystem crossing mechanism. Based on the ultrafast pump-probe experimental results, as well as decay kinetics of the compounds, the Schiff base with naphthalene unit, showed a fast transition to the triplet state (1.2 ps) as compared to Schiff bases including methyl (4 ps) and chloro (2.7 ps) units. However, upon the addition of various anions, the molecule structure gains anion sensing and fluorescence switching capabilities under daylight and UV light. The obtained experimental results pointed out that the modification of Schiff base molecules with methyl, chlorine and naphthalene units affected its photophysical properties as well as excited-state dynamics significantly. [Display omitted] • Novel three conjugated benzene sulfonamide Schiff bases have been synthesized and characterized. • Calorimetrically anion probing features of newly synthesized Schiff bases under daylight and UV light were observed. [ABSTRACT FROM AUTHOR]

A new Schiff base bearing sulfonamide group was synthesized and characterized by spectroscopic techniques. Its spectroscopic properties were investigated through density functional theory (DFT/B3LYP) method with the 6−311++G(d,p) basis set theoretically and the zwitterion ⇌ enol tautomerization was studied using IEF-PCM approximation. The thermodynamic (entropy, enthalpy and Gibbs free energy changes) and energetic quantities of the zwitterion ⇌ enol tautomerization indicate that the migration of single proton between zwitterion ⇌ enol tautomer's is unfavored for both directions in all phases. During the change from the water phase to the gas phase, the tautomeric energy barrier increases for the proton transfer reaction from the zwitterion form to the enol form, while the barrier decreases from the enol form to the zwitterion form. On the other hand, experimental studies (UV–vis. and NMR spectroscopies) release that there are two tautomeric species which are the zwitterion form in polar and the enol form in apolar solvents for the soluted compound. Furthermore, the antibacterial effect of the compound was investigated in two different solvents (DMSO and THF) to demonstrate the effect of dominant tautomeric species. The results indicate that the solution in which the enol form is dominant than the zwitterionic form has more antimicrobial efficiency for all bacterial species. Image 1 • A new Schiff base containing sulfonate ester group synthesized and characterized. • Zwitterion ⇌ enol tautomerization of synthesized compound experimentally and theoretically investigated. • Antibacterial properties of synthesized compounds have been screened. • The enol form of synthesized compound exhibited higher biological activities than zwitterion form. [ABSTRACT FROM AUTHOR]