Emission Spectral Studies Research Articles

An Insight Into Experimental and Theoretical Investigation of Structure, Photophysical Property by ESIPT Processes and Biological Activities of Schiff Base Copper Complex

ABSTRACTA novel Schiff base (BSSMO) and its copper complex have been synthesized, and their structure was delineated using single crystal XRD studies. Computational techniques were used to design and evaluate BSSMO‐based luminophores, revealing a significant intramolecular hydrogen bond within the molecule. Understanding ESIPT is crucial for optimizing photophysical and luminophore properties of organic molecules, especially for advancing optoelectronic devices. The study also explored the mechanisms of GSIPT and ESIPT for these BSSMO‐based luminophores using transition state theory, charge distribution, molecular orbital analysis, and quantum theory of atoms in molecules. Results advocated that BSSMO‐L2 exhibits higher absorption compared with BSSMO‐L1 and the same trend is observed in emission spectral studies. However, the intensity of enol emissions in BSSMO‐L2 is lower than that of keto (BSSMO‐L3) emissions and the S1 (Keto form) emission of BSSMO‐L3 shows significantly larger values, making it attractive for optoelectronic devices. The findings offer valuable insights for the development of ESIPT emitters with distinct photophysical properties. The in silico antidiabetic study of BSSMO‐L2 explores the interaction with PPAR‐γ protein, revealing a moderate affinity and stable complex, enhancing its bio‐potential for future applications. The in vitro anticancer study of Cu‐BSSMO‐L2 complex shows a potential anticancer effect through mitochondrial and extrinsic death receptor mediated pathways. These insights contribute to the design of novel benzenesulfonamide‐based bioactive molecules.

Benzothiazole-based Schiff base for sensing Ca2+ ions: Synthesis, DFT studies, toxicity evaluation in zebrafish embryo and in silico analysis of MMP-9 inhibition

A new heterocyclic Schiff base, 2-(2-benzo(d)thiazol-2yl)hydrazono)methyl)phenol (BTAZ) synthesized from 2-hydrazinobenzothaizole and salicyclaldehyde was characterized by spectral, mass and single crystal XRD data and subjected to sense Ca2+ ions in methanol–water mixture (1:1, v/v) using UV–visible absorption and fluorescence emission spectral studies. The probe BTAZ showed specific detection of Ca2+ ions in a solution containing various metal ions with a detection limit as low as 5.1 × 10−6 M via photo-induced electron transfer (PET) pathway. The binding stoichiometry between BTAZ and Ca2+ was determined to be 2:1 by Job’s plot method. The stoichiometry and optical properties of both BTAZ and BTAZ-Ca2+ complex showed good correlation with theoretical results based on DFT and TD-DFT calculations. The pharmacological evaluation of the probe BTAZ against bacterial and fungal stains also demonstrated its notable efficacy to control their growth in vitro along with anti-oxidant capabilities. Further, toxicity assay of the probe BTAZ against zebrafish embryo did demonstrate that it is non-toxic to the test model in vivo. Ability of the probe BTAZ to inhibit matrix metalloproteinase-9 (MMP-9) enzyme was analyzed in detail using in silico experiments.

One-Pot Sequential Synthesis of Alkenylated Dihydroquinolinones and Hexahydroacridinones in Deep Eutectic Solvent Medium.

The sequential synthesis of N-heterocycles from saturated ketones poses significant challenges and has rarely been reported. Herein, an efficient synthesis of alkenylated dihydroquinolinones 7 and hexahydroacridinones 8 is achieved from saturated ketones 1 or 2 via dehydrogenation, cyclization, oxidation, and α-alkenylation in choline chloride-based deep eutectic solvent (DES) medium. This strategy provides alkenylated dihydroquinolinones 7 and hexahydroacridinones 8 in excellent yield from low-cost, readily available starting materials under environmentally benign conditions. Furthermore, the synthesized compounds (4, 5, 7, and 8) were investigated for their photophysical properties through absorption and emission spectral studies.

An Indole-based Chromofluorogenic Probe for Detection of Trivalent Al3+, Ga3+, In3+ and Fe3+ Ions.

An easily synthesizable indole-derived chromofluorogenic probe InNS has been demonstrated for recognition of trivalent metal ions (i. e., Al3+, Ga3+, In3+ and Fe3+). Both UV-Vis and emission spectral studies have been employed to assess the cation sensing ability of InNS in semi-aqueous medium. This probe exhibited a chromogenic response for these metal ions, and the related change was accompanied with the appearance of a new absorption near 376 nm. An obvious color change from pale yellow to dark yellow could also be noticed upon addition of the aforementioned metal ions to the probe's solution. Distinctively from the UV-Vis analysis, the fluorescence behavior of InNS was completely different; it displayed a 'turn-on' fluorescence response for only Al3+ among all the studied cations. The detection limit and the association constant (Ka) for Al3+ were determined to be 12.5 nM and 6.85×106 M-1, respectively. A potential 1 : 1 binding mode of Al3+-InNS has been established based on Job's plot, 1H NMR and DFT analyses. The reversibility experiment was conducted using strongly chelating EDTA ion, and a corresponding logic gate has been devised. In terms of practical applications, the InNS has been utilized to detect Al3+ in human breast carcinoma (MCF-7) cell lines displaying promising 'turn-on' bioimaging experiments.

Synthesis, vibrational analysis, absorption and emission spectral studies, topology and molecular docking studies on sulfadiazine derivative

AbstractA new class of (N‐(pyrimidin‐2‐yl)‐4‐((1,7,7‐trimethylbicyclo [2.2.1] heptan‐2‐ylidene) amino) benzenesulfonamide (CDA) was synthesized from commercially available camphor and sulfadiazine. The synthesized Schiff‐base was characterized by FT‐IR, 1H and 13C NMR spectroscopic analyses. The HOMO, LUMO, MEP, chemical reactivity parameters, and NBO were calculated using the WB97XD/cc‐pVDZ basis set. For better understanding, the electronic absorption and emission of the compound were recorded using UV‐Vis and fluorescence spectra. Molecular docking simulations were investigated between ligand (compound) and target protein. The computational results correlate well with observed values. The frontier molecular orbital energy gap (3.78 eV) revealed that the studied molecule has higher polarizability and chemical reactivity with lower kinetic stability. In addition, compound showed the highest binding score −5.72 kcal/mol, which was confirmed by a molecular docking simulation.

One-pot domino synthesis of 1,2,4-triazolo [3,4-b][1,3,4] 6-amino thiadiazines and their CT-DNA binding study

A facile one-pot three component domino protocol has been successfully developed for the combinatorial synthesis of novel Schiff bases of 3-(2-(6-amino-7H- [1,2,4]-triazolo[3,4-b] [1,3,4]thiadiazin-3-yl)hydrazineylidene)indolin-2-ones 4, 5. This protocol utilizes readily available starting materials, leads to produce high yields (79–92 %).This domino reaction involves the formation of three new bonds (two CN and one C–S bond) and one heterocyclic ring in a single step. Notably, this reaction shows several remarkable features, such as short reaction time, eliminating the requirement for extensive workup and column chromatographic purification. In addition to this, the reaction demonstrates good scalability, producing satisfactory yields even on a gram -scale. Further, all the compounds were screened for their electronic absorption and fluorescence emission spectral studies by using CT-DNA. Compounds 5l, 5m, 5r, 5o, 5s have shown greater binding affinity with CT-DNA. In fluorescence emission spectra 5l, 5o, 5s demonstrate good quenching constant values with CT-DNA. And also, molecular docking studies were carried out for all the synthesized compounds.

A Solid-state reaction based study, synthesis and characterization for CuAl2O4 nanocrystalline powder

The crystalline nanopowder of Copper Aluminium Oxide (CuAl2O4) was synthesized through a solid-state reaction method, on the application of optoelectronic and catalytic activity of different compositions based on the weight percent of materials. These novel formulated compound samples were studied for their structural properties through powder X-ray diffraction and it was found that they possessed the cubic phase structure. The samples which were developed have crystallite sizes ranging between 16 nm and 79 nm. Debye Scherrer formula was employed to observe the prepared sample's crystallinity range, just to identify that the range was between 55% and 66%. The surface morphology and chemical composition were also investigated and observed in the prepared samples. The optical properties were studied using diffuse reflectance spectroscopy through the Kubelka-Munk function and it was inferred that an energy bandgap between 1.46 eV and 1.86 eV existed in the samples. The emergence of ultraviolet, violet, and blue emission peaks in CuAl2O4 was revealed by a PL emission spectral study.

NIR emission and up-conversion spectral studies of Er/Yb co-doped B2O3-Bi2O3-NaF-BaF2 glasses for optical amplifiers and laser applications

Er-singly and Er/Yb-codoped oxyfluoride glasses were prepared by conventional melt-quenching technique. Structural, optical, steady-state and time-resolved spectroscopy studies were performed. The down-conversion (DC) and up-conversion (UC) mechanisms in the Er3+, Yb3+ (single) and Er3+/Yb3+ (co-doped) systems were investigated under 980 nm laser excitation and the energy transfers involved in the emissions of Er3+ and Yb3+ ions were discussed. Judd-Ofelt intensity and radiative factors such as absorption cross-section (σabs) and emission cross-sections (σemi) were evaluated and an enhanced σemi was observed for the co-doped (1 mol% Er/1 mol% Yb) glasses. Gain cross-section profiles were estimated based on σabs and σemi from McCumber theory for the 4I13/2 ↔ 4I15/2 transitions. At the same time, the studied glasses also exhibited intense UC transitions from the excited states of 2H11/2, 4S3/2, and 4F9/2 to the 4I15/2 ground state of Er3+ ions and covered the strong green and red spectral regions. Time-resolved spectroscopic measurements are extended for NIR and UC emission transitions were discussed in detail.

Electronic Absorption, Emission Spectral, and Electrochemical Studies of [Cu(OBTTAP)] Linked (bpy)2RuII, (phen)2RuII, and (PPh3)CpRuII Complexes

Electronic Absorption, Emission Spectral, and Electrochemical Studies of [Cu(OBTTAP)] Linked (bpy)2RuII, (phen)2RuII, and (PPh3)CpRuII Complexes

Deciphering the binding site and mechanism of new methylene blue with serum albumins: A multispectroscopic and computational investigation

Herein, the interaction mechanism of new methylene blue (NMB) with human serum albumin (HSA) and bovine serum albumin (BSA) was carefully investigated both experimentally and conceptually, employing experimental and insilico analysis. The steady-state emission spectral studies showed that the emission intensity of HSA and BSA was quenched significantly by NMB. The findings of the Stern–Volmer and double logarithmic plot revealed that the observed emission quenching process was through a static quenching mechanism and the measured binding constant values (Kb) for HSA–NMB and BSA–NMB are 2.766 and 1.187 × 105 dm3 mol−1 respectively. The time-resolved fluorescence lifetime measurement and UV–vis absorption investigation further verify the complex formation between NMB and HSA/BSA. The assessment of thermodynamic parameters disclosed the binding process was spontaneous driven by hydrogen bonds (H-bond) and van der Waals interactions, which contributed a significant role in the complexation. Moreover, the secondary structural conformation and microenvironment of HSA/BSA were modified in the presence of NMB, as evidenced by circular dichroism and synchronous fluorescence data. Molecular docking study predicted a plausible binding mode of NMB inside the binding pocket of HSA and BSA. These results demonstrated that the stabilized NMB is found at the Subdomain IIA (site I) of both the proteins and the results were correlated well with the competitive binding assay. Additionally, the principal components analysis revealed less variation of docked poses for HSA, while, more dispersed docked poses were observed for the BSA model. This also highlights the effects of docking towards a modeled protein (BSA). Molecular dynamic (MD) simulation based binding free energy (ΔGmmgbsa) estimation obtained at 298, 303, 308 and 313 K, were in good agreement with our experimental (ΔGbind) values.

Sulfonamide functionalized silica nano-composite: characterization and fluorescence "turn-on" detection of Fe3+ ions in aqueous samples.

We have synthesized novel sulfonamide-based nano-composite (SAN) for selective and sensitive detection of Fe3+ ions in aqueous samples. Morphological characterization of SAN was carried out with TGA, FT-IR, UV-Vis, ninhydrin assay, FE-SEM, pXRD, BET, EDX, and elemental analysis. The sensing nature, effect of pH, sensor concentration and response time analysis were accomplished with the help of emission spectral studies and SAN was assessed as "turn-on" emission detector for the biologically important Fe3+ ions. Here, the LOD and LOQ were computed to be 26.68nM and 88.93nM, respectively, and it was found to be much lower than the permissible limit of Fe3+ ions in drinking water. The accuracy of the sensor (SAN) was determined by testing the aqueous samples spiked with known concentrations of Fe3+ ions and results demonstrated 98.00-99.66% recovery, which made SAN a reliable, selective and sensitive chemosensor for the quantification of Fe3+ ions in fully aqueous media.

Experimental and Computational Characterisation of the Molecular Interactions between 1‐Butyl‐1‐methyl‐pyrrolidin‐1‐ium bis(trifluoromethanesulphonyl)imide and Human Serum Albumin

AbstractRecently, ionic liquids (ILs) have emerged as a therapeutic agent for industrial‐based pharmacology. In this regard, the current study highlights the key aspects of IL, (1‐butyl‐1‐methyl‐pyrrolidine‐1‐ium bis(trifluoromethanesulphonyl)imide), [Pyr C4 NTf3−] such as pharmacodynamics and pharmacokinetics. We performed a detailed experimental and computational analysis of [Pyr C4 NTf3−] with human serum albumin (HSA) using various spectroscopic techniques viz. UV‐vis, steady‐state fluorescence, synchronous fluorescence, time‐resolved fluorescence, steady‐state anisotropy and tensiometry study along with molecular docking. Absorption and emission spectral studies revealed the complex formation between [Pyr C4 NTf3−] and HSA where the binding constant (Kb) was found to be 5.5×103 Lmol−1. Thermodynamic parameters, Gibb's free energy change (ΔG), molar enthalpy change (ΔH), and molar entropy change (ΔS) revealed that the complex formation process is spontaneous, and enthalpy driven where involvement of hydrogen bond and van der Waal forces play a major role. Further, CD spectroscopy and ANS experiment showed the stability of HSA in presence of [Pyr C4 NTf3−]. A site marker study suggested that the binding of [Pyr C4 NTf3−] occurred at site II in HSA which is well supported by a molecular docking study. Also, MD simulation was done which revealed the stability of the complex formed between HSA and [Pyr C4 NTf3−]. The study might help in utilizing [Pyr C4 NTf3−], IL as a therapeutic agent in the pharmaceutical industries.

Synthesis, Structural Characterization and Investigation of DNA/BSA Binding Properties of a Homo-disulphide Schiff Base Compound Carrying Oxo Propargyl Group

In this work, a new homo-disulphide Schiff base compound (HDSB) was prepared and its structure was characterised by common spectroscopic and analytical methods. The compound was obatined from the condensation reaction of 2-aminothiophenol and 2-hydroxy-4-(prop-2-yn-1-yloxy)benzaldehyde in benzene. In the reaction, both Schiff base condensation and oxidation of thiols into disulphide formed. The isolated compound was structurally characterized by single crystal X-ray diffraction experiment. The homo-disulphide Schiff base compound (HDSB) was screened for its DNA/BSA binding properties using UV-Vis absorption and emission spectral studies. The compound showed considerable binding affinity to double-stranded fish sperm DNA (FSds-DNA) with binding constant of 4.1 × 104 M-1. Spectral measurements suggest that HDSB interacts with DNA in a minor groove binding mode. The compound also showed binding properties towards BSA (bovine serum albumin). The incremental addition of HDSB to the BSA solution resulted in a significant decrease in the characteristic emission band of BSA in the range of 320-500 nm (λexc: 280 nm) showing the binding interactions between HDSB and BSA.

Linear and non-linear photoluminescence studies of Ho3+/Yb3+ co-doped titanate phosphors for photonic applications

This work presents the morphological and photoluminescence (PL) studies of the single ion Ho3+ doped and Ho3+/Yb3+ co-doped Ba3−x-yMoTiO8:xHo3+/yYb3+ phosphors synthesized by conventional solid-state reaction method. Phase confirmation of all the as-prepared samples was done by X-Ray Diffraction (XRD) patterns. The morphological behavior and vibrational frequency bands were studied by Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FT-IR) techniques respectively. Diffuse Reflectance Spectra (DRS) has been recorded for the singly doped and co-doped samples to find out the optical bandgap. The linear and non-linear emission spectral studies under 448 and 980 nm excitation wavelengths respectively showed three bands in the green, red, and blue regions. A relatively more intense band observed in the green region under 980 nm excitation shows promising usage of the titled phosphor for non-linear applications. A plot drawn between non-linear luminescence emission intensity Vs pump power reveals the information pertaining to the number of photons involved in the process. In addition, Commission Internationale de I′Eclairage (CIE) coordinates calculated from the emission spectral features lie in the green region. All the studies show the broad application of the as-prepared phosphors in linear and non-linear luminescence process-based green emitting diodes, display devices, security inks, phototherapy, and solid-state lighting (SSL) applications.

Decrypting the interaction pattern of Piperlongumine with calf thymus DNA and dodecamer d(CGCGAATTCGCG)2 B-DNA: Biophysical and molecular docking analysis

The mechanisms of interaction of DNA with pharmacological molecules are critical to understanding their therapeutic actions on physiological systems. Piperlongumine is widely studied for its anticancer potential. Multi-spectrometry, calorimetry and in silico studies were employed to study the interaction of piperlongumine and calf thymus DNA. UV–Vis spectroscopy illustrated a hyperchromic pattern in spectra of the calf thymus DNA-piperlongumine complex, while fluorescent quenching was observed in emission spectral studies. Competitive displacement assay demonstrated higher displacement and binding constant for DNA-rhodamine B complex by piperlongumine than DNA-methylene blue complex. Differential scanning calorimetry presented non-significant changes in melting temperature and molecular docking presented the precise interaction site of piperlongumine with calf thymus DNA at minor groove. Further, piperlongumine treatment did not result in pBluescript KS plasmid DNA cleavage as revealed from the DNA topology assay. All these experiments confirmed the binding of piperlongumine with DNA through minor groove binding mode.

A Fluorene based Fluorogenic ''Turn-off'' Chemosensor for the Recognition of Cu2+ and Fe2+: Computational Modeling and Living-cell Application

Background: The traditional methods for the detection and quantification of Cu2+ and Fe3+ heavy metal ions are usually troublesome in terms of high-cost, non-portable, time-consuming, specialized personnel and complicated tools, so their applications in practical analyses is limited. Therefore, the development of cheap, fast and simple-use techniques/instruments with high sensitivity/selectivity for the detection of heavy metal ions is highly demanded and studied. Methods: In this study, a fluorene-based fluorescent ''turn-off'' sensor, methyl 2-(2-((((9H-fluoren-9- yl)methoxy)carbonyl)amino)-3- phenylpropanamido) acetate (probe FLPG) was synthesized via onepot reaction and characterized by 1H-NMR, 13C-APT-NMR, HETCOR, ATR-FTIR and elemental analysis in detailed. All emission spectral studies of the probe FLPG have been performed in CH3CN/HEPES (9/1, v/v, pH=7.4) media at rt. The quantum (Φ) yield of probe FLPG decreased considerably in the presence of Cu2+ and Fe3+. The theoretical computation of probe FLPG and its complexes were also performed using density functional theory (DFT). Furthermore, bio-imaging experiments of the probe FLPG was successfully carried out for Cu2+ and Fe3+ monitoring in living-cells. Results: The probe FLPG could sense Cu2+ and Fe3+ with high selectivity and sensitivity, and quantitative correlations (R2>0.9000) between the Cu2+/Fe3+ concentrations (0.0−10.0 equiv). The limits of detection for Cu2+ and Fe3+ were found as 25.07 nM and 37.80 nM, respectively. The fluorescence quenching in the sensor is managed by ligand-to-metal charge transfer (LMCT) mechanism. Job’s plot was used to determine the binding stoichiometry (1:2) of the probe FLPG towards Cu2+ and Fe3+. The binding constants with strongly interacting Cu2+ and Fe3+ were determined as 4.56×108 M-2 and 2.02×1010 M-2, respectively, via the fluorescence titration experiments. The outcomes of the computational study supported the fluorescence data. Moreover, the practical application of the probe FLPG was successfully performed for living cells. Conclusion: This simple chemosensor system offers a highly selective and sensitive sensing platform for the routine detection of Cu2+ and Fe3+, and it keeps away from the usage of costly and sophisticated analysis systems.

SYTHESIS OF RUTHENIUM(II) COMPLEXES WITH CARBOXAMIDE DERIVATIVES: SPECTROSCOPIC CHARACTERISATION AND STUDIES ON DNA AND BSA INTERACTION

Two new mononuclear ruthenium(II) complexes of two new carboxamide derivatives formulated as [Ru(bpy)2(L7 )](ClO4)2 (1) and [Ru(bpy)2(L8 )](ClO4)2 have been isolated as pure materials from the reaction of HL 7 and HL 8 [where HL 7= N-(furan-2-ylmethyl)-2 pyridinecarboxamide and HL 8 = N-(thiophen-2-ylmethyl)-2- pyridinecarboxamide] with Ru(bpy)2Cl2. All the complexes were characterized by physico-chemical and spectroscopic tools. The interaction of the complexes with calf thymus DNA (CT-DNA) using absorption, emission spectral and viscosity studies have been used to determine the binding constant, Kb and the linear Stern-Volmer quenching constant, KSV. The results indicate that the ruthenium(II) complexes interact with CT-DNA strongly in a groove binding mode. The interactions of bovine serum albumin (BSA) with the complexes were also investigated with the help of absorption spectroscopy tools. Absorption spectroscopy proved the formation of a ground state BSA- [Ru(L)(bpy)2](ClO4)2 complex.

Selective Detection of Picric Acid and Pyrosulfate Ion by Nickel Complexes Offering a Hydrogen-Bonding-Based Cavity.

This work describes the synthesis and characterization of three mononuclear nickel complexes supported with amide-based pincer ligands. All three complexes presented an H-bonding-based cavity due to the migration of amidic protons to the appended heterocyclic rings that formed H-bonds with the metal-ligated solvent molecule(s). These complexes functioned as the nanomolar chemosensors for the detection of picric acid and pyrosulfate ion as inferred by the detailed absorption and emission spectral studies while further supported with FTIR, NMR, and mass spectra of the isolated products. We also illustrate a few practical detection methods for the sensing of picric acid in the solution state as the naked-eye colorimetric methods and in the solid state by employing polystyrene films.

Physical and spectroscopic studies of Sm3+ ions doped Alumino Tungsten Borate glasses for photonic applications

Trivalent samarium ion doped glasses with molar composition 10MgO–10WO3–10Al2O3–BaF2-(60-X) B2O3- XSm2O3 (where X = 0.5, 1.0, 1.5, 2.0, 2.5 mol %) are prepared by melt quenching method. These glasses are characterized by various spectroscopic techniques such as optical absorption, excitation, emission and decay spectral studies. The amorphous nature is confirmed by XRD studies. From the absorption spectra, oscillator strengths and the Judd-Ofelt (J-O) intensity parameters (Ω2, Ω4, Ω6) are calculated. The measured emission spectra exhibit four transitions 4G5/2 → 6H5/2, 6H7/2, 6H9/2 and 6H11/2 at 565 nm, 602 nm, 650 nm and 709 nm. Various radiative parameters such as branch ratio (βR), transition probability (AR), radiative lifetime (τR), effective bandwidth (Δλp) and stimulated emission cross-section (σse) have been calculated. The photoluminescence decay measurements are carried out at 4G5/2 fluorescent level of Sm3+ ion doped AlWB glasses under 402 nm excitation wavelength. From decay curve analysis, quantum efficiencies of the as prepared glasses are calculated. The CIE Chromaticity coordinates are evaluated from the emission spectra which establishes the reddish orange emission from the prepared glasses. From the above luminescent properties, it is understood that the prepared glasses are suitable for reddish orange laser applications especially in opto-electronic devices.

A highly selective coumarin-based chemosensor for naked-eye detection of cyanide anions via nucleophilic addition in pure aqueous environment

A coumarin-based naked-eye colorimetric sensor IC has been developed for the highly selective detection of CN− over other common anions in pure aqueous solution. The nucleophilic addition of CN− inhibits ICT progress in IC, which is attributed to the color change from purple to colorless. The lowest detection limit for cyanide ion was estimated to be 1.3 and 0.8 µM based on absorption and emission spectral studies, respectively. The theoretical studies were also supported the optical responses of IC towards CN− was due to the interruption of π-conjugation and blocking ICT progress in IC. For more convenience, paper-based test strips displayed remarkable and easy-to-use naked-eye colorimetric detection of CN− in pure water as low as 25 ppm.