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The spontaneous aggregation of infectious or misfolded forms of prion protein is known to be responsible for neurotoxicity in brain cells, which ultimately leads to the progression of prion disorders. Bovine spongiform encephalopathy (BSE) in animals and Creutzfeldt–Jakob disease (CJD) in humans are glaring examples in this regard. Square-planar complexes with labile ligands and indole-based compounds are found to be efficiently inhibitory against protein aggregation. Herein, we report the synthesis of an indole-based cyclometallated palladium complex. The ligand and complex were characterized by various spectroscopic techniques such as UV-visible, NMR, IR, and HRMS. The molecular structure of the complex was confirmed by single-crystal X-ray crystallography. The interaction of the complex with PrP106–126 was studied using UV-visible spectroscopy, CD spectroscopy, MALDI-TOF MS, and molecular docking. The inhibition effects of the complex on the PrP106–126 aggregation, fibrillization and amyloid formation phenomena were analysed through the ThT assay, CD, TEM and AFM. The effect of the complex on the aggregation process of PrP106–126 was determined kinetically through the ThT assay. The complex presented high binding affinity with the peptide and influenced the peptide's conformation and aggregation in different modes of binding. Furthermore, the MTT assay on neuronal HT-22 cells showed considerable protective properties of the complex against PrP106–126-mediated cytotoxicity. These findings suggest that the compound influences peptide aggregation in different ways, and the anti-aggregation action is primarily associated with the metal's physicochemical properties and the reactivity rather than the ligand. As a result, we propose that this compound be investigated as a potential therapeutic molecule in metallopharmaceutical research to treat prion disease (PD). [ABSTRACT FROM AUTHOR]

This report describes the synthesis of a seventeen-membered macrocyclic ring containing ligand (L1) by the reaction of 1,8-bis(2-(chloromethyl)phenoxy)octane with selenium powder. The trans-palladium dichloride complex (C1) of the macrocyclic selenium ligand was synthesized from its reaction with the Pd(CH3CN)2Cl2 precursor. The formation of the ligand and complex was authenticated with the help of various analytical techniques like 1H and 13C{1H} NMR, HRMS, FTIR, UV-visible spectroscopy, and elemental analysis. The structure of the ligand and its coordination mode with the palladium precursor were authenticated with the help of single crystal X-ray diffraction. The complex possesses a distorted square planar geometry around the palladium center. The new ligand and complex are air and moisture insensitive and stable at room temperature for over three months. The variable temperature NMR data and computational studies suggest selenium inversion in the palladium complex (C1) with an inversion barrier of ∼22.6 kcal mol−1. The palladium complex C1 was used as a catalyst for the dehydroxymethylation of long alkyl chain containing dihydroxy compounds. Generally, two separate catalysts are used for dehydroxymethylation (one for the oxidation of the alcohol and the other for the decarbonylation of the aldehyde). Here a single catalyst shows the dual action of dehydroxymethylation with up to 91% yield under only 5.0 mol% catalyst loading. A broad substrate scope can be achieved with good functional group tolerance. The PPh3 and Hg poisoning tests suggest the homogeneous nature of the reaction. Interestingly, the same long alkyl chain containing dihydroxy compounds were reported to undergo macrolactonization when reacted with a ruthenium catalyst. [ABSTRACT FROM AUTHOR]

The chemotherapeutic potential of ruthenium(II) complexes has recently attracted researchers' interest as antibacterial and anticancer agents. In this study, two novel half-sandwich imine-based Ru complexes ([Ru(p-cymene)Cl(L-1)][PF6] (Ru-1) and [Ru(p-cymene)Cl(L-2)][PF6] (Ru-2)) were reported for their deoxyribonucleic acid (DNA) binding and antitubercular, antibacterial, and anticancer activities. The molecular structure of Ru-2 was obtained by single-crystal X-ray crystallography. DNA interaction studies were conducted by UV-Vis absorbance and fluorescence spectral titration which gave rise to DNA binding constants (Kb) of 1.32 × 106 and 1.82 × 106 for Ru-1 and Ru-2, respectively and the Stern–Volmer binding constant (KSV) values for Ru-1 and Ru-2 were 1.7763 × 104 M−1 and 7.6 × 103 M−1, respectively. The in vitro antitubercular activity was evaluated against Mycobacterium tuberculosis H37Ra. The antibacterial potential of both the Ru-complexes was examined against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus and Bacillus subtilis) bacteria. The half-maximal inhibitory concentration (IC50) values for the antitubercular activity of Ru-1 and Ru-2 were 4.87 ± 1.32 μM and 5.78 ± 0.54 μM, respectively. A cytotoxic study of these complexes was performed against the human breast cancer cell line (MCF-7) and the human embryonic kidney cell line (HEK293) (normal cells). The study revealed meaningful activity of the Ru-1 complex against (cancer) MCF-7 cells, while the viability of HEK293 (normal) cells in the presence of Ru-2 was higher as compared to a reference drug 5FU. We suggest that these kinds of Ru-complexes could have potential for application in metallopharmaceuticals. [ABSTRACT FROM AUTHOR]

Selective identification of metal ions as well as their removal is possible when a sensing unit is anchored to a solid support. In this paper, functionalized mesoporous silica with a pendant rhodamine 6G moiety (R6FMS) has been obtained by successive grafting of an aldehyde derivative of bisphenol A followed by rhodamine 6G over a 3-aminopropyl anchored mesoporous silica framework. The materials have been characterized by powder X-ray diffraction, nitrogen sorption and electron microscopy studies, FT-IR and solid state MAS NMR spectral studies, and thermal analysis. In ethanol, the colorless silica material gives pink coloration in the presence of Al3+, Cr3+, Fe3+ and Cu2+ which is also clearly evident from the generation of an absorption peak at 525 nm. Upon excitation at 500 nm, the fluorescence intensity of the probe increases by 36-, 17-, 40- and 89-fold in the presence of Al3+, Cr3+, Fe3+ and Cu2+ ions, respectively. This suggests that R6FMS is a colorimetric and fluorescent chemosensor for these cations in ethanol. However, when the solvent is changed from ethanol to water, it becomes a selective chemosensor only for Cu2+ and Hg2+, by the generation of a pink color and strong fluorescence at ca. 550 nm, thereby discriminating the trivalent cations. Cations induce the opening of the spirolactam ring resulting in pink coloration and strong fluorescence. The quantum yield and lifetime of the probe have been increased considerably in the presence of these cations in ethanol as well as in aqueous media. The detection limit values for these cations range from 10−6 to 10−8 M. R6FMS has been used to remove Hg2+ and Cu2+ from their aqueous solution with a maximum adsorption capacity of 35 mg g−1 and 148 mg g−1 for Cu2+ and Hg2+, respectively. [ABSTRACT FROM AUTHOR]

Detection of Al3+ has become important as it is related to several health issues and other problems. Different fluorophoric platforms, such as naphthalene, benzene, rhodamine, etc., have been explored to sense Al3+ and a good number of research articles are being published. This article focuses on the synthesis of recently reported aluminum sensors constructed from 2-hydroxy-1-naphthaldehyde, salicylaldehyde, rhodamine, coumarin and different metal based-MOFs. [ABSTRACT FROM AUTHOR]

Detection of Al3+ has become important as it is related to several health issues and other problems. Different fluorophoric platforms, such as naphthalene, benzene, rhodamine, etc., have been explored to sense Al3+ and a good number of research articles are being published. This article focuses on the synthesis of recently reported aluminum sensors constructed from 2-hydroxy-1-naphthaldehyde, salicylaldehyde, rhodamine, coumarin and different metal based-MOFs. [ABSTRACT FROM AUTHOR]

A reaction of copper(I) halides (X = I, Br, Cl) and silver(I) halides with 9-anthraldehyde thiosemicarbazone (9-Hanttsc, H1L) and triphenylphosphine produced halogen-bridged dinuclear complexes, [M2(μ2-X)2(η1-S-9-Hanttsc)2(Ph3P)2] (M = Cu, X = Cl, 1; Br, 2; I, 3; M = Ag, X = Cl, 4; Br, 5). A similar reaction of 9-anthraldehyde-N1-methyl thiosemicarbazone (9-Hanttsc-N1-Me, H2L) with Ph3P and silver(I) halides yielded sulfur-bridged dimers, [Ag2X2(μ2-S-9-Hanttsc-N1-Me)2(Ph3P)2] (X = Cl, 9; Br, 10), however with copper(I) halides insoluble compounds were formed, which upon the addition of one extra mole of Ph3P gave mononuclear complexes of the formula [CuX(η1-S-9-Hanttsc-N1-Me)(Ph3P)2] (X = Cl, 6; Br, 7; I, 8). All of the complexes have been characterized by elemental analysis, NMR (1H, 13C) spectroscopy and single crystal X-ray crystallography (2, 5, 6, and 9). Both the ligands (H1L and H2L) and their complexes (1–10) were tested for their anti-tubercular and anticancer activities. The interactions of the ligands and their complexes (copper and silver) with calf thymus DNA (ct-DNA) and human serum albumin (HSA) were examined through UV-visible and fluorescence spectroscopy. Results showed that copper complex 2 displayed strong interactions with ct-DNA and HSA having binding constant values of 6.66 × 104 M−1 and 3.28 × 104 M−1, respectively, followed by silver complex 10 which gave binding constant values of 4.60 × 104 M−1 and 3.06 × 104 M−1, respectively. All of the complexes also showed good interactions with DNA in docking studies. [ABSTRACT FROM AUTHOR]

A rhodamine based chemosensor, 3-(((2-(3′,6′-bis(ethylamino)-2′,7′-dimethyl-3-oxospiro[isoindoline-1,9′-xanthen]-2-yl)ethyl)imino)methyl)-2-hydroxy-5-methylbenzaldehyde (HL-CHO), has been developed for the detection of Al3+, Cr3+ and Fe3+ ions. The absorbance of HL-CHO at 528 nm increases significantly in HEPES buffer in methanol : water (9 : 1, v/v) (pH 7.4) in the presence of Al3+, Cr3+ and Fe3+ ions with the alteration of solution color from colorless to pink. The fluorescence intensity of the probe at 550 nm enhances by 1465, 588 and 800 fold in the presence of Al3+, Cr3+ and Fe3+ ions, respectively. To the best of our knowledge, this huge increase in fluorescence intensity with Al3+ and Cr3+ has not been observed for other rhodamine based chemosensing systems. The weak fluorescence and no coloration of the probe are due to the existence of a spirolactam ring. The trivalent cations induce the opening of the spirolactam ring and consequently change the color and the fluorescence intensity followed by the 1 : 1 complex formation with HL-CHO which are evident from Job's analysis, ESI mass spectral analysis and elemental analysis. The quantum yield and lifetime of HL-CHO have increased considerably in the presence of the trivalent cations. The high sensitivity of the probe towards all the cations is evident from the nM order of LOD values. This has been used in living cell imaging studies with the human neuroblastoma SH-SY5Y cell line. Having appended –CHO groups for Schiff-base condensation with other amines, HL-CHO could be a potential precursor for future chemosensors. [ABSTRACT FROM AUTHOR]

Two positional isomers, 4-methyl-2-((quinolin-6-ylimino)methyl)phenol (6-QMP) and 4-methyl-2-((quinolin-2-ylimino)methyl)phenol (2-QMP), have been synthesized to compare their fluorescence sensing properties. 6-QMP and 2-QMP have been synthesized by Schiff-base condensation between 2-hydroxy-5-methylbenzaldehyde and the respective amine (6-aminoquinoline for 6-QMP and 2-aminoquinoline for 2-QMP) under mild conditions. These compounds have been characterized by standard methods. 6-QMP and 2-QMP have been found to be dual fluorescence chemosensors for Al3+ and Zn2+ ions but the increment of fluorescence intensity varies. 6-QMP can detect Al3+ (emission at 543 nm) and Zn2+ (emission at 525 nm) by the enhancement of emission intensity by 97 and 79 fold, respectively, with the same excitation wavelength at 415 nm. However, 2-QMP shows two different excitation and emission wavelengths for the detection of Al3+ (emission at 376 nm; λex = 330 nm) and Zn2+ (emission at 550 nm; λex = 435 nm). The increase in emission intensity is low (4.5 fold for Al3+ and 35 fold for Zn2+) compared to that with 6-QMP. The enhancement of intensity may be explained by the PET mechanism. Both the probes form a 1 : 1 complex with both the metal ions as indicated by the elemental and different spectral analysis. 6-QMP shows better sensitivity towards both the metal ions than 2-QMP. Both the probes are able to detect Al3+ and Zn2+ ions by producing distinct color changes that can be observed by the naked eye. Some theoretical calculations have been performed to investigate spectral transitions of the probes along with their aluminum and zinc compounds. These compounds have been used for living cell imaging studies. A comparison with the recently published studies has been made. [ABSTRACT FROM AUTHOR]

A compartmental chemosensor probe HL has been designed and synthesized for the selective recognition of zinc ions over other transition metal ions via fluorescence “ON” strategy. The chemosensing behaviour of HL was demonstrated through fluorescence, absorption and NMR spectroscopic techniques. The molecular structure of the zinc complex derived from HL was determined by X-ray crystallography. A probable mechanism of this selective sensing behavior was described on the basis of spectroscopic results and theoretical studies by density functional theory (DFT). The biological applicability of the chemosensor HL was examined via cell imaging on HeLa cells. The HL-zinc complex served as a secondary fluorescent probe responding to the pyrophosphate anion specifically over other anions. The fluorescence enhancement of HL in association with Zn2+ ions was quenched in the presence of pyrophosphate (PPi). Thus, a dual response was established based on “OFF–ON–OFF” strategy for detection of both cation and anion. This phenomenon was utilized in the construction of a “INHIBIT” logic gate. [ABSTRACT FROM AUTHOR]

A Cd(ii) based 2D metal–organic framework (MOF), [Cd(4-bpd)(SCN)2]n (1) where 4-bpd = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, has been synthesized and characterized by standard methods including single crystal X-ray diffraction analysis. When it is sandwiched between ITO coated glass and Al, 1 shows interesting conduction properties. The I–V characteristics of the ITO/1/Al configuration measured in the dark and under illumination of incident light exhibit a highly non-linear rectifying behavior, which signifies its Schottky diode character. The conductivity of the configuration is 2.90 × 10−4 S m−1 and 7.16 × 10−4 S m−1 under dark and photoirradiation conditions, respectively. Different parameters have been analyzed and these indicate that 1 can be a promising candidate for light sensing electronic devices. This material has good sensitivity to the light source when switched on/off. Theoretical calculations have been performed to understand the reason for the enhancement of conductivity under illumination of incident light. It has been found that upon irradiation, slight changes in the bond distances of 4-bpd in 1 occur. These changes are related to the considerable decrease in the energy needed for the allowed electronic transition. This may influence the increase of conductivity along with other factors. [ABSTRACT FROM AUTHOR]

Mesoporous silica functionalized with a 2-hydroxy-naphthyl moiety has been synthesized and characterized by standard techniques like powder X-ray diffraction, N2 adsorption/desorption studies, transmission electron microscopy and spectral studies like FT-IR, UV-visible, fluorescence and 13C and 29Si solid state NMR. The functionalized silica material showed significant enhancement in its emission intensity in the presence of Al3+ ions whereas other metal ions could not bring about any increase in its emission intensity. They either quench the emission or do not alter the intensity significantly making the functionalized material a fluorescence chemosensor for Al3+. The sensitivity of the probe towards Al3+ has been determined to be high with a low limit of detection value. As functionalized silica is not soluble in common solvents, it has been effectively used to bind and remove Al3+ from a solution. Theoretical calculations on a model system have been performed to investigate the electronic spectral transitions. [ABSTRACT FROM AUTHOR]

The uncoordinated sulfur atom of the thiocyanato ligand of a 3D metallo-organic framework (MOF), [Ni(3-bpd)2(NCS)2]n (1), where 3-bpd is 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene, has been explored for selective visual detection and effective removal of Hg2+ in aqueous medium. [Ni(3-bpd)2(NCS)2]n has been synthesized under ambient conditions and characterized by elemental analysis, FT-IR spectroscopy, UV-vis spectroscopy, FE-SEM and EDX, XPS and X-ray single crystal diffraction analysis. 1 shows two thiocyanato moieties bound to the hexacoordinated metal center with N atoms whereas the sulfur end remains uncoordinated. The strategy for binding and removal of Hg2+ is very simple. Hg2+ is known for its affinity for strong bond formation with the soft center, S. The sulfur atoms form bonds with this heavy metal ion. The color of 1 changes from green to grey as Hg atoms form coordinate bonds with S atoms of the SCN− group. It has been found that Hg is present in grey materials in a 2 : 1 ratio (Hg/Ni). 1 is selective for Hg as other metals/metalloids, including heavy metal ions, present in water are unable to change the color of 1 as they do not form any bond with it. Binding of Hg with the S end of the thiocyanato moiety has been confirmed by a number of techniques, e.g. IR and UV-vis spectra, FESEM, EDX, and XPS. Simple filtration is done to separate grey materials for the removal of Hg2+ ion from the water medium. A theoretical calculation has been performed to rationalize the fact. [ABSTRACT FROM AUTHOR]

A novel cadmium(ii) based metal organic framework, [Cd(3-bpd)(SCN)2]n (1) where 3-bpd = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene has been synthesized and characterized by elemental analysis, various spectroscopic techniques, TGA and single crystal X-ray diffraction analysis. X-ray analysis shows the formation of an undulated polymeric two-dimensional network parallel to the (0 −1 1) plane. Current conduction properties of 1 have been explored in the dark and in the presence of light. The study shows that current conduction of the complex increases with the increase of the incident light intensity. On progression of intensity of glancing radiation the photosensitivity of 1 has been increased. The time dependent light response on charge carrier conduction reveals that complex 1 may uncover new ground to explore in optoelectronic switching applications. [ABSTRACT FROM AUTHOR]

Three new Cu(ii) complexes, [Cu4(O)(Ln)2(CH3COO)4] where HL1= 4-methyl-2,6-bis(2-fluoroethyliminomethyl) phenol for complex 1, HL2= 4-methyl-2,6-bis(2-chloroethyliminomethyl) phenol for complex 2·0.25CH3CNand HL3= 4-methyl-2,6-bis(2-bromoethyliminomethyl) phenol for complex 3have been synthesized and characterized by elemental analysis, FTIR, UV-vis spectroscopy, and electrospray ionization mass spectroscopy. The structure of complex 2·0.25CH3CNhas also been confirmed by single crystal X-ray diffraction analysis. These complexes have been found to be active catalysts for the oxidation of cyclohexane and toluene in the presence of hydrogen peroxide as the oxidant under mild conditions. Cyclohexane is oxidized to yield cyclohexanol and cyclohexanone, whereas toluene is oxidized to benzyl alcohol and benzaldehyde. [ABSTRACT FROM AUTHOR]