Click-generated triazole based ferrocene-carbohydrate bioconjugates: a highly selective multisignalling probe for Cu(II) ions

Two Cu2+-specific colorimetric sensors, based on ferrocene-carbohydrate bioconjugates, 2, C46H56O20N6Fe and 3, C28H33O10N3Fe were designed and synthesized in good yields. Both the compounds, 2 and 3, behave as very selective and sensitive chromogenic and electrochemical chemosensor for Cu2+ ion in aqueous environment (CH3CN/H2O (2:8, v/v). The analytical detection limit (ADL) for receptor 2 was 7.5 × 10−7 M. The considerable changes in their absorption spectra of 2 and 3 are accompanied by the appearance of a new low energy (LE) peak at 630 nm (2: ε = 1600 M−1 cm−1 and 3: 822 M−1 cm−1). This is further accompanied by a strong colour change from yellow to dark green that allows the prospective for ‘naked eye’ detection of Cu2+ ion

Resonant transport in a highly conducting single molecular junction via metal-metal covalent bond

Achieving highly transmitting molecular junctions through resonant transport at low bias is key to the next-generation low-power molecular devices. Although, resonant transport in molecular junctions was observed by connecting a molecule between the metal electrodes via chemical anchors by applying a high source-drain bias (> 1V), the conductance was limited to < 0.1 G$_0$, G$_0$ being the quantum of conductance. Here, we report electronic transport measurements by directly connecting a Ferrocene molecule between Au electrodes at the ambient condition in a mechanically controllable break junction setup (MCBJ), revealing a conductance peak at ~ 0.2 G$_0$ in the conductance histogram. A similar experiment was repeated for Ferrocene terminated with amine (-NH2) and cyano (-CN) anchors, where conductance histograms exhibit an extended low conductance feature including the sharp high conductance peak, similar to pristine ferrocene. Statistical analysis of the data along with density functional theory-based transport calculation suggests the possible molecular conformation with a strong hybridization between the Au electrodes and Fe atom of Ferrocene molecule is responsible for a near-perfect transmission in the vicinity of the Fermi energy, leading to the resonant transport at a small applied bias (< 0.5V). Moreover, calculations including Van der Waals/dispersion corrections reveal a covalent like organometallic bonding between Au and the central Fe atom of Ferrocene, having bond energies of ~ 660 meV. Overall, our study not only demonstrates the realization of an air-stable highly transmitting molecular junction, but also provides an important insight about the nature of chemical bonding at the metal/organo-metallic interface.Comment: 23 pages, 6 figures, supplementary include

A highly selective redox, chromogenic, and fluorescent chemosensor for Hg²⁺ in aqueous solution based on ferrocene–glycine bioconjugates

The synthesis, electrochemical, optical, and metal-cation-sensing properties of ferrocene–glycine conjugates C₃₀H₃₈O₈N₈Fe (2) and C₂₀H₂₄O₄N₄Fe (3) have been documented. Both compounds 2 and 3 behave as very selective redox (ΔE_1/2 = 217 mV for 2 and ΔE_1/2 = 160 mV for 3), chromogenic, and fluorescent chemosensors for Hg²⁺ cations in an aqueous environment. The considerable changes in their absorption spectra are accompanied by the appearance of a new low-energy peak at 630 nm (2, ε = 1600 M^–1cm^–1; 3, ε = 822 M^–1cm^–1). This is also accompanied by a strong color change from yellow to purple, which allows a prospective for the “naked eye” detection of Hg²⁺ cations. These chemosensors present immense brightness and fluorescence enhancement (chelation-enhanced fluorescence = 91 for 2 and 42 for 3) following Hg²⁺ coordination within the limit of detection for Hg²⁺ at 7.5 parts per billion

A triazole tethered triferrocene derivative as a selective chemosensor for mercury(II) in aqueous environment

The synthesis, electrochemical, optical and cation-sensing properties of two triazole tethered ferrocene derivatives, C₂₅H₂₅ON₃Fe₂, 2 and C₄₀H₄₀O₂N₆Fe₃, 3 are presented. The solid state structure of compound 2 has been established by X-ray diffraction analysis which reveals that the unit cell of molecule 2 consists of 3-D helical chain formed via CH⋯N interaction and π⋯π stacking. The complexation properties of the receptors can be inferred either from redox shift or visual output response (colorimetric) for Hg²⁺ and Cu²⁺ cations. The common structural feature of these ligands is the presence of other ferrocene moiety as redox unit. Interestingly, the redox and colorimetric responses, towards Hg²⁺ are preserved in the presence of water (CH₃CN/H₂O, 2/8), which can be used for the selective colorimetric detection of Hg²⁺ in aqueous environment over other competitor cations. The changes in the absorption spectra are accompanied by the appearance of a new low energy (LE) peak at ca. 626 nm for 2 and 632 nm for 3 (2: ε = 669 M⁻¹ cm⁻¹ and 3: ε = 1150 M⁻¹ cm⁻¹), due to the change in color from yellow to purple for Hg2+ cations in CH₃CN/H₂O (2:8)

An Efficient Ferrocene Derivative as a Chromogenic, Optical, and Electrochemical Receptor for Selective Recognition of Mercury(II) in an Aqueous Environment

The synthesis, electrochemical, optical, and cation-sensing properties of two triazole-tethered ferrocenyl benzylacetate derivatives, C₃₆H₃₆O₆N₆Fe (<b>2</b>) and C₂₃H₂₃O₃N₃Fe (<b>3</b>), are presented. The binding event of both the receptors can be inferred either from a redox shift (<b>2</b>, Δ<i>E</i>_1/2 = 106 mV for Hg²⁺ and Δ<i>E</i>_1/2 = 187 mV for Ni²⁺; <b>3</b>, Δ<i>E</i>_1/2 = 167 mV for Hg²⁺ and Δ<i>E</i>_1/2 = 136 mV for Ni²⁺) or a highly visual output response (colorimetric) for Hg²⁺, Ni²⁺, and Cu²⁺ cations. Remarkably, the redox and colorimetric responses toward Hg²⁺ are preserved in the presence of water (CH₃CN/H₂O, 2/8), which can be used for the selective colorimetric detection of Hg²⁺ in an aqueous environment over Ni²⁺ and Cu²⁺ cations. The changes in the absorption spectra are accompanied by the appearance of a new low-energy (LE) peak at 625 nm for both compounds <b>2</b> and <b>3</b> (<b>2</b>, ε = 2500 M^–1 cm^–1; <b>3</b>, ε = 1370 M^–1 cm^–1), due to a change in color from yellow to purple for Hg²⁺ cations in CH₃CN/H₂O (2/8)

An Efficient Ferrocene Derivative as a Chromogenic, Optical, and Electrochemical Receptor for Selective Recognition of Mercury(II) in an Aqueous Environment

The synthesis, electrochemical, optical, and cation-sensing properties of two triazole-tethered ferrocenyl benzylacetate derivatives, C₃₆H₃₆O₆N₆Fe (<b>2</b>) and C₂₃H₂₃O₃N₃Fe (<b>3</b>), are presented. The binding event of both the receptors can be inferred either from a redox shift (<b>2</b>, Δ<i>E</i>_1/2 = 106 mV for Hg²⁺ and Δ<i>E</i>_1/2 = 187 mV for Ni²⁺; <b>3</b>, Δ<i>E</i>_1/2 = 167 mV for Hg²⁺ and Δ<i>E</i>_1/2 = 136 mV for Ni²⁺) or a highly visual output response (colorimetric) for Hg²⁺, Ni²⁺, and Cu²⁺ cations. Remarkably, the redox and colorimetric responses toward Hg²⁺ are preserved in the presence of water (CH₃CN/H₂O, 2/8), which can be used for the selective colorimetric detection of Hg²⁺ in an aqueous environment over Ni²⁺ and Cu²⁺ cations. The changes in the absorption spectra are accompanied by the appearance of a new low-energy (LE) peak at 625 nm for both compounds <b>2</b> and <b>3</b> (<b>2</b>, ε = 2500 M^–1 cm^–1; <b>3</b>, ε = 1370 M^–1 cm^–1), due to a change in color from yellow to purple for Hg²⁺ cations in CH₃CN/H₂O (2/8)

A triazole based triferrocene derivative as a multiresponsive chemosensor for Hg(II) ion and a redox chemosensor for H₂PO₄⁻ ion

A triazole tethered triferrocene receptor, C₄₀H₄₀O₂N₆Fe₃ 3, has been synthesized from the reaction of mono-alkynyl substituted ferrocene, 1 and 1,1′-bis-(azidomethyl)ferrocene, 2. Consequently the cation and anion sensing properties of 3 have been examined. The receptor 3 was found to be highly selective electrochemical [Math Processing Error], optical and chromogenic chemosensor for Hg²⁺ ion in aqueous environment. The substantial changes in its absorption spectra are accompanied by the appearance of a new low-energy peak at 631 nm (ɛ = 3400 M⁻¹ cm⁻¹). This is also accompanied by a strong color change from yellow to purple, that allows a prospective for the “naked eye” detection of Hg²⁺ ion over other competitor cations such as Pb²⁺, Cd²⁺, Zn²⁺, etc. In addition, among various anions, 3 shows a distinct electrochemical recognition of dihydrogen phosphate anion by its multiple H-bonding (C–H⋯O), which is supported by electrochemical (large cathodic shift ΔE_1/2 = −175 mV) and ¹H NMR titration results

Novel class of heterometallic cubane and boride clusters containing heavier group 16 elements

Thermolysis of an in situ generated intermediate, produced from the reaction of [Cp*MoCl4] (Cp* = η5-C5Me5) and [LiBH4.THF], with excess Te powder yielded isomeric [(Cp*Mo)2B4TeH5Cl] (2 and 3), [(Cp*Mo)2B4(μ3-OEt)TeH3Cl] (4), and [(Cp*Mo)4B4H4(μ4-BH)3] (5). Cluster 4 is a notable example of a dimolybdaoxatelluraborane cluster where both oxygen and tellurium are contiguously bound to molybdenum and boron. Cluster 5 represents an unprecedented metal-rich metallaborane cluster with a cubane core. The dimolybdaheteroborane 2 was found to be very reactive toward metal carbonyl compounds, and as a result, mild pyrolysis of 2 with [Fe2(CO)9] yielded distorted cubane cluster [(Cp*Mo)2(BH)4(μ3-Te){Fe(CO)3}] (6) and with [Co2(CO)8] produced the bicapped pentagonal bipyramid [(Cp*MoCo)2B3H2(μ3-Te)(μ-CO){Co3(CO)6}] (7) and pentacapped trigonal prism [(Cp*MoCo)2B3H2(μ3-Te)(μ-CO)4{Co6(CO)8}] (8). The geometry of 8 is an example of a heterometallic boride cluster in which five Co and one Mo atom define a trigonal prismatic framework. The resultant trigonal prism core is in turn capped by two boron, one Te, and one Co atom. In the pentacapped trigonal prism unit of 8, one of the boron atoms is completely encapsulated and bonded to one molybdenum, one boron, and five cobalt atoms. All the new compounds have been characterized in solution by IR, 1H, 11B, and 13C NMR spectroscopy, and the structural types were unambiguously established by crystallographic analysis of 2 and 4–8

A new synthetic route to Lindqvist type clusters [(n-Bu₄N)x][M′M₅O₁₉] [when x = 2, M′ = M = Mo or W; x = 3, M′ = Mo, M = W] from metal carbonyl precursors [(CO)₅ML] [M = Mo, W; L= CO, C(OMe)(Me)]

Two fully oxidized [(n-Bu4N)2][Mo6O19], 7 and [(n-Bu4N)2][W6O19], 8 and one mixed-metal, mixed-valence one electron reduced [(n-Bu4N)3][MoW5O19], 9 cluster have been synthesized under biphasic reaction conditions from group VI metal carbonyls or Fischer carbene complexes, [(CO)5M[double bond, length as m-dash]C(OMe)Me] (M = Mo, W) in yields of 73, 77 and 71% respectively. All the clusters have been characterized by IR, 1H and 13C NMR spectra, and crystal structure determinations. Additionally, the composition of 9 has also been supported by mass spectrometry (MALDI-TOF), inductively coupled plasma (ICP) and energy-dispersive X-ray (EDX) analysis. This novel and mild route offers distinct improvements over earlier methods of synthesis for Lindqvist type mixed-valence mixed-metal polyoxometalate cluster

Catecholboryl-functionalized ferrocene based Lewis acid system: a selective probe for fluoride ion through multiple channels

The design and synthesis of two new receptors, C₂₀H₁₉O₃BFe and C₂₀H₂₁O₃BFe and their anion sensing properties through multiple channels are reported. Both the receptors, having chelating boronic ester Lewis acidic centre as the sole binding site, selectively bind fluoride ion in micromolar concentration. The binding constant of C₂₀H₁₉O₃BFe with the fluoride ion has been found to be quite high [K = 106 M⁻¹], whereas it displays a negligible affinity towards other effective competitors, for example acetate and cyanide (K = 10 M₋₁) and no sensitivity towards other halide ions. Upon selective recognition of F⁻ in acetonitrile, the redox potential of C₂₀H₁₉O₃BFe shifted by ΔE = 200 mV and the fluorescence emission was quenched drastically. The considerable changes in their absorption spectra are accompanied by the appearance of a new low energy (LE) peak at 566 nm and by a strong colour change from yellow to deep green which allows the prospective for “naked eye” detection of F⁻ anion