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)

Combined Experimental and Theoretical Investigations of Group 6 Dimetallaboranes [(Cp*M)₂B₄H₁₀] (M = Mo and W)

Thermolysis of mono metal carbonyl fragment, [M′(CO)₅·thf, M′ = Mo and W, thf = tetrahydrofuran] with an <i>in situ</i> generated intermediate, obtained from the reaction of [Cp*MCl₄] (M = Mo and W, Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) with [LiBH₄·thf], yielded dimetallaboranes, <b>1</b> and <b>2</b>. Isolations of [{Cp*M­(CO)}₂B₄H₆] (M = Mo (<b>1</b>) and W­(<b>2</b>)) provide direct evidence for the existence of saturated molybdaborane and tungstaborane clusters, [(Cp*M)₂B₄H₁₀]. Our extensive theoretical studies together with the experimental observation suggests that the intermediate may be a saturated cluster [(Cp^#M)₂B₄H₁₀], not unsaturated [(Cp^#M)₂B₄H₈] (Cp^# = Cp or Cp*), which was proposed earlier by Fehlner. Furthermore, in order to concrete our findings, we isolated and structurally characterized analogous clusters [(Cp*Mo)₂(CO)­(μ-Cl)­B₃H₄W­(CO)₄] (<b>3</b>) and [(Cp*WCO)₂(μ-H)₂B₃H₃W­(CO)₄] (<b>4</b>). All the compounds have been characterized by solution-state ¹H, ¹¹B, IR, and ¹³C NMR spectroscopy, mass spectrometry, and the structural architectures of <b>1</b>, <b>3</b>, and <b>4</b> were unequivocally established by X-ray crystallographic analysis. The density functional theory calculations yielded geometries that are in close agreement with the observed structures. Both the Fenske–Hall and Kohn–Sham molecular orbital analyses showed an increased thermodynamic stability for [(Cp^#M)₂B₄H₁₀] compared to [(Cp^#M)₂B₄H₈]. Furthermore, large HOMO–LUMO gap and significant cross cluster M–M bonding have been observed for clusters <b>1</b>–<b>4</b>

Sensitive and Selective Redox, Chromogenic, and “Turn-On” Fluorescent Probe for Pb(II) in Aqueous Environment

The electrochemical, optical, and metal cation sensing properties of the triazole-tethered ferrocene–anthracene conjugates, C₄₈H₄₀FeO₂N₆ (<b>3</b>) and C₅₂H₄₀FeO₂N₆ (<b>4</b>), and the ferrocene–pyrene conjugates, C₂₉H₂₅FeON₃ (<b>5</b>) and C₃₁H₂₅FeON₃ (<b>6</b>), have been documented. All the compounds <b>3</b>–<b>6</b> behave as very selective redox, chromogenic, and “turn-on” fluorescent probes for Pb²⁺ ion in an aqueous environment (CH₃CN/H₂O, 2/8). The significant changes in their absorption spectra are accompanied by a strong color change from yellow to greenish blue, which allows a prospective use for the “naked eye” detection of Pb²⁺ ion over other competitor cations such as Hg²⁺ and Cd²⁺. These chemosensors present immense brightness and fluorescence enhancement (chelation-enhanced fluorescence = 85 for <b>3</b> and 92 for <b>4</b>) following Pb²⁺ coordination within the limit of detection at 2 ppb. Interestingly, their fluorescence, redox, and colorimetric responses are preserved in presence of water, which can be used for the selective colorimetric detection of Pb²⁺ ion in aqueous environment over Hg²⁺ and Cd²⁺ cations. All the compounds have been characterized by ¹H, ¹³C NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS) spectrometric analysis, and the solid-state structures of <b>5</b> and <b>6</b> have been unequivocally established by X-ray diffraction analysis

Synthesis and Characterization of Novel Ruthenaferracarboranes from Photoinsertion of Alkynes into a Ruthenaferraborane

Photolysis of [{(μ₃-BH)­(Cp*Ru)­Fe­(CO)₃}₂(μ-CO)] (<b>1</b>; Cp* = η⁵-C₅Me₅) in the presence of various alkynes such as 1,2-diphenylethyne, 1-phenyl-1-propyne, 2-butyne, and 1-(diphenylphosphino)-2-phenylacetylene led to the formation of four types of novel heterometallic metallacarboranes, [1,1,1-(CO)₃-μ-2,3-(CO)-2,3-(Cp*)₂-4,6-Ph₂-<i>closo</i>-1,2,3,4,6-FeRu₂C₂BH] (<b>2</b>), [1,8-(Cp*)₂-2,2,7,7-(CO)₄-μ-2,8-(CO)-μ-7,8-(CO)-4-Me-5-Ph-<i>pileo</i>-1,2,7,4,5-RuFe₂C₂(BH)₂] (<b>3</b>), [1,8-(Cp*)₂-2,2,7,7-(CO)₄-μ-2,8-(CO)-μ-7,8-(CO)-4,5-Me₂-<i>pileo</i>-1,2,7,4,5-RuFe₂C₂(BH)₂] (<b>4</b>), and [1,2-(Cp*)₂-6,6,7,7-(CO)₄-μ-2,7-(CO)-<i>exo</i>-μ-5,6-(PPh₂)-μ₃-1,2,6-(BH)-4-Ph-<i>pileo</i>-1,2,6,7,4,5-Ru₂Fe₂C₂BH] (<b>5</b>). Cluster compound <b>2</b> exhibits an octahedral structure with adjacent carbon atoms consistent with its skeletal electron pair (sep) count of 7. The cage geometry of <b>3</b> and <b>4</b> is based on a pentagonal bipyramid with one additional {Cp*Ru} vertex capping one of its faces. The solid-state X-ray diffraction results of <b>5</b> suggest that the core geometry is a capped pentagonal bipyramid, with an Fe–C bridging PPh₂ group. All the cluster compounds <b>2</b>–<b>5</b> have been characterized by IR and ¹H, ¹¹B, and ¹³C NMR spectroscopy, and the geometries of the structures were unequivocally established by crystallographic analysis

Ferrocene and Triazole-Appended Rhodamine Based Multisignaling Sensors for Hg²⁺ and Their Application in Live Cell Imaging

Two triazole-appended ferrocene–rhodamine conjugates, C₄₇H₄₅N₇O₃Fe (<b>2</b>) and C₄₉H₄₉N₇O₃Fe (<b>3</b>), have been synthesized, and their electrochemical, optical, and metal cation sensing properties have been explored in aqueous medium. The newly synthesized receptors are simple, easily synthesizable, and display very high “turn on” fluorescence response for Hg²⁺ as well as I^– in an aqueous environment. Quantification of the absorption titration analysis shows that the receptors <b>2</b> and <b>3</b> can detect the presence of Hg²⁺ even at very low concentrations (∼3 ppb). The mode of metal coordination has been studied by DFT calculations. Furthermore, the receptors <b>2</b> and <b>3</b> are less toxic toward MCF-7 cells and could detect intracellular Hg²⁺ by fluorescent imaging studies

Ferrocene and Triazole-Appended Rhodamine Based Multisignaling Sensors for Hg²⁺ and Their Application in Live Cell Imaging

Two triazole-appended ferrocene–rhodamine conjugates, C₄₇H₄₅N₇O₃Fe (<b>2</b>) and C₄₉H₄₉N₇O₃Fe (<b>3</b>), have been synthesized, and their electrochemical, optical, and metal cation sensing properties have been explored in aqueous medium. The newly synthesized receptors are simple, easily synthesizable, and display very high “turn on” fluorescence response for Hg²⁺ as well as I^– in an aqueous environment. Quantification of the absorption titration analysis shows that the receptors <b>2</b> and <b>3</b> can detect the presence of Hg²⁺ even at very low concentrations (∼3 ppb). The mode of metal coordination has been studied by DFT calculations. Furthermore, the receptors <b>2</b> and <b>3</b> are less toxic toward MCF-7 cells and could detect intracellular Hg²⁺ by fluorescent imaging studies

Combined Experimental and Theoretical Investigations of Group 6 Dimetallaboranes [(Cp*M)₂B₄H₁₀] (M = Mo and W)

Thermolysis of mono metal carbonyl fragment, [M′(CO)₅·thf, M′ = Mo and W, thf = tetrahydrofuran] with an <i>in situ</i> generated intermediate, obtained from the reaction of [Cp*MCl₄] (M = Mo and W, Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) with [LiBH₄·thf], yielded dimetallaboranes, <b>1</b> and <b>2</b>. Isolations of [{Cp*M­(CO)}₂B₄H₆] (M = Mo (<b>1</b>) and W­(<b>2</b>)) provide direct evidence for the existence of saturated molybdaborane and tungstaborane clusters, [(Cp*M)₂B₄H₁₀]. Our extensive theoretical studies together with the experimental observation suggests that the intermediate may be a saturated cluster [(Cp^#M)₂B₄H₁₀], not unsaturated [(Cp^#M)₂B₄H₈] (Cp^# = Cp or Cp*), which was proposed earlier by Fehlner. Furthermore, in order to concrete our findings, we isolated and structurally characterized analogous clusters [(Cp*Mo)₂(CO)­(μ-Cl)­B₃H₄W­(CO)₄] (<b>3</b>) and [(Cp*WCO)₂(μ-H)₂B₃H₃W­(CO)₄] (<b>4</b>). All the compounds have been characterized by solution-state ¹H, ¹¹B, IR, and ¹³C NMR spectroscopy, mass spectrometry, and the structural architectures of <b>1</b>, <b>3</b>, and <b>4</b> were unequivocally established by X-ray crystallographic analysis. The density functional theory calculations yielded geometries that are in close agreement with the observed structures. Both the Fenske–Hall and Kohn–Sham molecular orbital analyses showed an increased thermodynamic stability for [(Cp^#M)₂B₄H₁₀] compared to [(Cp^#M)₂B₄H₈]. Furthermore, large HOMO–LUMO gap and significant cross cluster M–M bonding have been observed for clusters <b>1</b>–<b>4</b>

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] (<b>2</b> and <b>3</b>), [(Cp*Mo)₂B₄(μ₃-OEt)­TeH₃Cl] (<b>4</b>), and [(Cp*Mo)₄B₄H₄(μ₄-BH)₃] (<b>5</b>). Cluster <b>4</b> is a notable example of a dimolybdaoxatelluraborane cluster where both oxygen and tellurium are contiguously bound to molybdenum and boron. Cluster <b>5</b> represents an unprecedented metal-rich metallaborane cluster with a cubane core. The dimolybdaheteroborane <b>2</b> was found to be very reactive toward metal carbonyl compounds, and as a result, mild pyrolysis of <b>2</b> with [Fe₂(CO)₉] yielded distorted cubane cluster [(Cp*Mo)₂(BH)₄(μ₃-Te)­{Fe­(CO)₃}] (<b>6</b>) and with [Co₂(CO)₈] produced the bicapped pentagonal bipyramid [(Cp*MoCo)₂B₃H₂(μ₃-Te)­(μ-CO)­{Co₃(CO)₆}] (<b>7</b>) and pentacapped trigonal prism [(Cp*MoCo)₂B₃H₂(μ₃-Te)­(μ-CO)₄{Co₆(CO)₈}] (<b>8</b>). The geometry of <b>8</b> 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 <b>8</b>, 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 <b>2</b> and <b>4</b>–<b>8</b

Reactivity of Dirhodium Analogues of Octaborane-12 and Decaborane-14 towards Transition-Metal Moieties

Building upon the key results of our earlier work on rhodaboranes, we continue to explore the chemistry of two <i>nido</i>-rhodaborane clusters, [(Cp*Rh)₂B₈H₁₂] (<b>1</b>) and [(Cp*Rh)₂B₆H₁₀] (<b>2</b>) with [Au­(PPh₃)­Cl] that yielded [(Cp*Rh)₂(AuPPh₃)₂B₈H₁₀] (<b>3</b>) and isomeric [(Cp*Rh)₂(AuPPh₃)₂B₆H₈] (<b>4a</b>,<b>b</b>) respectively. The reactivity of <b>2</b> with [Au­(PPh₃)­Cl] was rather unusual. In <b>3</b> Au exhibits a regular μ₂-bonding mode, while in <b>4a</b>,<b>b</b> there is a μ₃-bonding with a Au–Rh bond. Further, the reactivity of <b>2</b> was performed with [Fe₂(CO)₉] that permitted the isolation of 12-vertex [(Cp*Rh)₂B₆H₆{Fe­(CO)₂}₂{Fe­(CO)₃}₂] (<b>5</b>), 7-vertex [(Cp*Rh)₂{Fe­(CO)₃}₂B₃H₃] (<b>6</b>), and the heterometallic compound [(Cp*Rh)₂{Fe­(CO)₃}₂(μ₃-CO)₂] (<b>7</b>) in moderate to good yields. The cluster core of <b>5</b> consists of a 10-vertex isocloso geometry with two additional {Fe­(CO)₃} vertices capping two trigonal faces. Cluster <b>6</b> contains a capped-octahedral geometry, where one of the boron atoms is in the capping position. All of the compounds have been characterized by IR and ¹H, ¹¹B, and ¹³C NMR spectroscopy in solution, and the solid-state structures were established by crystallographic analysis of <b>3</b>–<b>7</b>