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A new rhodamine 6G-based chemosensor (L3) exhibits excellent CHEF-based recognition of trivalent metal ions M3+ (M = Fe, Al, and Cr) over mono and di- and other trivalent metal ions with applications in combinational logic circuits and memory devices.

Abnormal levels (high/low) of urinary human serum albumin (HSA) are associated with a number of diseases and thus act as an essential biomarker for quick therapeutic monitoring and biomedical diagnosis, entailing the urgent development of an effective chemosensor to quantify the albumin levels. Herein, we have rationally designed and developed a small fluorogenic molecular probe, (Z)-2-(5-((8-hydroxy-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-9-yl) methylene)-4-oxo-2-thioxothiazolidin-3-yl) acetic acid (HJRA) with a twisted intramolecular charge transfer (TICT) property, which can easily self-assemble into nonfluorescent nanoaggregates in aqueous solution. However, HJRA nanoaggregates can selectively bind with serum albumin proteins (HSA/BSA) in ∼100% PBS medium, thereby facilitating the disassembly of nanoaggregates into monomers, exhibiting a clear turn-on red fluorescent response toward HSA and BSA. Analysis of the specific binding mechanism between HJRA and HSA using a site-selective fluorescence displacement assay and molecular docking simulations indicates that a variety of noncovalent interactions are responsible for the disassembly of nanoaggregates with the concomitant trapping of the HJRA monomer at site I in HSA, yielding a substantial red emission caused by the inhibition of intramolecular rotation of HJRA probe inside the hydrophobic cavity of HSA. The limit of detection (LOD) determined by the 3σ/slope method was found to be 1.13 nM, which is substantially below the normal HSA concentration level in healthy urine, signifying the very high sensitivity of the probe toward HSA. The comparable results and quick response toward quantification of HSA in urine by HJRA with respect to the Bradford method clearly point toward the superiority of this method compared to the existing ones and may lead to biomedical applications for HSA quantification in urine. It may also find potential application in live-cell imaging of HSA.

The reaction of MeO-salox (4-methoxy salicylaldehyde-oxime) with Mn(OAc)2·4H2O in a 1 : 1 molar ratio in methanol medium and in the presence of tetrabutylammonium hydroxide yields the hexanuclear complex [Mn6O2(4-MeO-salox)6(N3)2(MeOH)2(H2O)2·2H2O]n (1). Single crystal X-ray diffraction reveals that complex 1 adopts a 1D chain network facilitated by two EE-azido bridges. BSA binding studies reveal that complex 1 causes fluorescence quenching of BSA through both static and dynamic mechanisms. A 1 : 1 binding mode is established through a Benesi–Hildebrand plot with an intrinsic binding constant of (3.40 ± 0.01) × 104 M−1. The circular dichroism studies indicate variation of the secondary structure of BSA upon binding with complex 1. The site-selective binding and molecular docking studies reveal the probable binding site of complex 1 is at the mouth of site I in subdomain IIA of BSA.

The foremost objective of the present study was to develop and validate a new LC-QTOF-MS/MS method for the identification and quantitative determination of 4,6-dichloro-5-nitro-2-(propylthio)pyrimidine (DPP) genotoxic impurity through the derivatization process in ticagrelor active pharmaceutical ingredient (API). Owing to the low response of DPP at the specification level, DPP was converted to 4,6-dibenzylamino-5-nitro-2-(propylthio)pyrimidine (DPP derivative) by addition of benzyl amine, then analyzed using mass spectrometry with a time-of-flight analyzer, and good separation was accomplished under the experimental conditions described. The effective separation of DPP derivative was achieved using an Acquity UPLC BEH C

Here, we present a detailed investigation on the interaction of 4-chloro-7-nitro-1,2,3-benzoxadiazole (NBD) embedded olanzapine derivative (OLA-NBD) with a model transport protein, human serum albumin (HSA). The thermodynamic parameters, Δ

We report a novel phenazine-embedded fluorescent probe (2-[2-(pyridin-2-ylmethoxy)-phenyl]-1H-imidazo[4,5-b]phenazine, PIP), which upon complexation with Cu(II)-ion-forming [(PIP)CuII(Cl)] becomes ...

Fluorescence spectroscopy is a significant bio-analytical technique for specific detection of nitric oxide (NO) and for broadcasting the in vitro and in vivo biological activities of this gasotransmitter. Herein, a benzo-coumarin embedded smart molecular probe (BCM) is employed for NO sensing through detailed fluorescence studies in purely aqueous medium. All the spectroscopic analysis and literature reports clearly validate the mechanistic insight of this sensing strategy i.e., the initial formation of 1,2,3,4-oxatriazole on treatment of the probe with NO which finally converted to its carboxylic acid derivative. This oxatriazole formation results in a drastic enhancement in fluoroscence intensity due to the photoinduced electron transfer (PET) effect. The kinetic investigation unveils the second and first-order dependency on [NO] and [BCM] respectively. The very low detection limit (16 nM), high fluorescence enhancement (123 fold) in aqueous medium and good formation constant (Kf = (4.33 ± 0.48) × 104 M−1) along with pH invariability, non-cytotoxicity, biocompatibility and cell permeability make this probe a very effective one for tracking NO intracellularly.

A fluorescein hydrazone based conjugate (H2L3) was synthesized by coupling fluorescein hydrazide (L1) with 2-(pyridin-2-ylmethoxy)-naphthalene-1-carbaldehyde (L2). H2L3 was well characterized by several spectroscopic methods such as IR, 1H, 13C-NMR and ESI-MS. The probe H2L3 exhibited high selectivity and high sensitivity towards toxic Hg2+ ions in semi-aqueous medium (pH 7.2, 10 mM HEPES) over other metal ions. The significant enhancement in fluorescence emission centered at 520 nm was attributed to the Hg2+-induced ring opening of the spirolactam moiety in the fluorescein structure. The 1 : 1 binding of H2L3 to Hg2+ was established by Job's method and confirmed by ESI-MS+ (m/z) studies and the binding constant was calculated as (0.43 ± 0.04) × 104 M−1 with a detection limit of 1.24 μM. Then again, the [Hg(HL3)]+ ensemble could be utilized as a reversible fluorescent sensor for S2−. On addition of S2− to the [Hg(HL3)]+ complex, the fluorescence intensity was totally quenched because Hg2+ in the complex was grabbed by S2− because of the stronger binding force between Hg2+ and S2−. The tentative coordination environment in the [Hg(HL3)]+ complex was established by DFT studies. The fluorescence “OFF–ON–OFF” mode of H2L3 was examined in the presence of Hg2+ and S2− and finds applications in devices with logic gate functions. H2L3 also exhibits bio-compatibility and negligible cytotoxicity and is suitable for fluorescence cell imaging of Hg2+ ions in live HepG2 cells.

[MnIII3(μ3-O)]7+ based μ2-nitrato-bridged discrete asymmetric complex [Mn3O(5-Br-salox)3(NO3)(H2O)4] (1) (5-Br-saloxH2 = 2-hydroxy-5-bromo-benzaldehyde oxime) has been synthesized in methanol by the reaction between 5-Br-salox and Mn(NO3)2·6H2O in 1:1 M ratio in the presence of triethylamine (TEA) and characterized by single crystal X-ray diffraction analysis. DNA binding studies reveal that complex 1 interacts with double stranded CT-DNA through groove binding mode and the intrinsic binding constant was determined by spectroscopic studies to be (1.63 ± 0.04) × 106 M−1.

In this article, we have designed and synthesized a new, convenient and efficient phenanthroquinone-pyridoxal based fluorogenic probe PQPY, highly suitable for the selective and sensitive detection of nitric oxide in an aerated aqueous (7 : 3/H2O : MeCN) medium at pH 7.0 (10 mM HEPES buffer). Upon addition of nitric oxide, this probe exhibits emission in the green region (λem = 505 nm) which is ascribed to ICT (intramolecular charge transfer) from the phenanthroquinone moiety to the imidazole -N-N[double bond, length as m-dash]O fragment. The apparent formation constant, Kf, of the NO product of the ligand is (1.00 ± 0.2) × 105 M-1 and the LOD is 78 nM. The substantial enhancement of the life-time of the ligand (τ0 = 2.68 ns) occurs due to binding with nitric oxide (τ0 = 3.96 ns). This probe is low cytotoxicity, cell permeable and suitable for living cell imaging application.

Two dinuclear oxidovanadium(V) complexes [LiVVO(µ2-O)VVO(Li)] (i = 1, H2L1, complex 1 and i = 2 for H2L2, complex 2) of two ONNO donor amine-bis(phenolate) ligands have been synthesized and characterized by X-ray diffraction studies which exhibited distorted octahedral geometry around each V center. In MeCN the complexes exist as dimers as indicated by HRMS studies, however, in the presence of 2 or more equivalents of H+ the dimers turned into monomers, ([LiVV = O]+ which exists in equilibrium with ([LiVV = OH]2+ and evidenced from the shift in λmax from 685 nm to 765 nm for complex 1 and 600 to 765 nm for complex 2. The complexes 1 and 2 efficiently catalyze the oxidative bromination of salicylaldehyde in the presence of H2O2 to produce 5-bromo-salicylaldehyde as the major product with TONs 405 and 450, respectively in the mixed solvent system (H2O:MeOH:THF = 4:3:2, v/v). The kinetic analysis of the bromide ion oxidation reaction indicates a mechanism which is first order in peroxidovanadium complex and bromide ion and limiting first-order on [H+]. The evaluated kBr and kH values are (8.82 ± 0.35) and (65.0 ± 2.23) M−1 s−1 for complex 1 and (6.74 ± 0.19) and (61.87 ± 2.27) M−1 s−1 for complex 2, respectively. The Ka of protonated species ([LiVV = OH]2+ are: Ka = (4.3 ± 0.40) × 10−3 (pKa = 2.37) and (4.7 ± 0.50) × 10−3 (pKa = 2.33) for complex 1 and 2 respectively. On the basis of the chemistry displayed by these model compounds, a mechanism of bromide oxidation and a tentative catalytic cycle have been framed which might be relevant to vanadium haloperoxidase enzymes and supported by DFT calculations.

A hydrazone-based conjugate Nap-hyz-pyz (H3L3) with potential N2O2 donor atoms was found to act as a dual channel (colori- and fluori-metric) sensor towards Al3+ and PPi in H2O-MeOH (6 : 4, v/v) at pH 7.2 (40 mM HEPES buffer) at 25 °C. The formation constants, Kf = (3.49 ± 1.77) × 104 and (3.78 ± 0.1) × 104 M-1, of the sensor towards Al3+ were determined by absorption and fluorescence titrations, respectively. The 1 : 1 stoichiometry of the reaction was determined by Job's method and confirmed by ESI-MS+ (m/z) studies. The LOD for Al3+, as determined by the 3σ method, was found to be 114.54 nM. Most strikingly, the addition of ∼115 μM PPi to the Nap-hyz-pyz-Al3+ ensemble (20 μM ligand and 74 μM Al3+) leads to complete quenching of fluorescence. The fluorescence response of Nap-hyz-pyz towards Al3+ was not perturbed by the presence of 5 equivalents or more of other ions and inorganic anions. The structure of the [Al(L3)(H2O)] complex was delineated by DFT calculations. TD-DFT studies were performed to investigate various spectral transitions. Based on changes in the fluorescence intensities of Nap-hyz-pyz in the presence of Al3+ and PPi at 487 nm, INHIBIT and molecular logic gates were constructed and interpreted. The probe was found to be bio-compatible and cell permeable with no or negligible cytotoxicity; thus, it provides a good opportunity for in vitro cell imaging studies of these ions. The presence of ATP or Pi did not interfere with the fluorescent detection of PPi. Thus, these evident and excellent sensing capabilities of Nap-hyz-pyz towards Al3+ and PPi were further scrutinized in HepG2 cell lines.

A Cu(II) based sensor (1) prepared by the complexation between (quinolin-8-ylamino)-acetic acid hydrazide (L2) and Cu2+ ions has been developed for a highly sensitive and selective recognition of HNO and S2− over other biologically abundant anions with prominent enhancement in absorption and emission intensities. The sensor (1) shows weak fluorescence due to ET (electron transfer) but upon addition of HNO and S2− a large enhancement in the fluorescence intensity (F.I.) was observed over other possible competitive anions on the basis of reduction of Cu(II) to Cu(I) and formation of CuS, respectively. The 1 : 1 complexation was characterized by mass spectrometry (MS), elemental analysis and Job's plot. The corresponding Kf value was evaluated to be (4.934 ± 0.05) × 104 M−1 for Cu2+ from UV-Vis absorption titration. Quantum yields of L2 and [Cu-L2 + S2−] and [Cu-L2 + HNO] complexes in acetonitrile (CH3CN) are found to be 0.107, 0.09 and 0.07, respectively, using quinine sulphate as the standard.

A novel manganese(III)-Schiff base complex anchored SBA-15 based heterogeneous catalyst SBA-15-SB-Mn was synthesized and characterized by various physicochemical techniques. The catalyst was found to exhibit excellent green catalysis for the aerial oxidation of 3,5-di-tert-butyl catechol (3,5-DTBC) to the corresponding 3,5-di-tert-butylcatechol-1,2-benzoquinone (3,5-DTBQ) with 83.17% conversion (TON = 515) within 1 h at room temperature and relevant to catechol oxidase behavior.

[MnIII3(μ3-O)]7+ based EE-azido-bridged 1D chains [{Mn3O(5-Br-salox)3(N3)(H2O)4}·3H2O]n(1) and [{Mn3O(5-Br-salox)3(N3)(H2O)3(DMF)}·2H2O·DMF]n(2) (5-Br-saloxH2 = 2-hydroxy-5-bromo-benzaldehyde oxime) have been synthesized and characterized by single crystal X-ray diffraction analysis. The complex 1 was synthesized by the reaction between ligand and metal precursor in the presence of azide ion in MeOH, while complex 2 can be obtained in two ways: in the first method, the same reaction as in 1, with only difference in solvent composition – a mixture of solvents DMF/MeOH (2:3/v/v) was used. In another method, 2 was isolated simply by the recrystallization of 1 from DMF. Magnetic studies on these complexes reveal that both 1 (ΔE = 45. 9 K; τ0 = 6.6 × 10−10) and 2 (ΔE = 54 and 49.7 K; τ0 = 1.4 × 10−12 s and 7.6 × 10−12 s) exhibit SCM behavior with a slight difference in magnetic properties due to the only difference in coordinated/non-coordinated solvents.

Methodological synthesis of a new biocompatible bi-compartmental rhodamine based probe (L3) provides a multi-inputs and multi-outputs molecular logic circuit based on simple chemosensing phenomena. Spectroscopic responses of Cu2+ and Hg2+ towards L3 together with reversible binding of S2- with L3-Cu2+ and L3-Hg2+ complexes help us to construct a thee-input molecular circuit on their control and sequential addition to a solution of L3 in a mixed organo-aqueous medium. We have further successfully encoded binary digits out of these inputs and outputs which may convert a three-digit input string into a two-digit output string resulting a simple monomolecular logic circuit. Such a molecular ‘Boolean’ logic operation may improve the complexity of logic gate circuitry and computational speed and may be useful to employ in potential biocompatible molecular logic platforms.

Reaction of a symmetric compartmental Schiff-base ligand, (H2L) with nickel(II) perchlorate hexahydrate in 1:1 M ratio in methanol gives rise to a mononuclear nickel(II) compound, NiL (1). The compound has been characterized by C, H, N microanalyses and UV–Vis spectra. The single crystal X-ray diffraction studies reveal a square planar geometry around the Ni(II) center. The compound crystallizes in monoclinic system with space group C2/c with a = 21.6425(6), b = 9.9481(3), c = 13.1958(4) A, β = 107.728(2)°, V = 2706.16(14) A3 and Z = 4. Ground state DFT optimization and TDDFT calculations on the ligand and complex were performed to get their UV–Vis spectral pattern.