Formation of Hydroxyindenyl and Vinylidene Ligands by Reaction of Internal Alkynes with Cp*Fe(CO)(NCMe)Ph

The reactivity of Cp*Fe­(CO)­(NCMe)­Ph (<b>1</b>) (Cp* = pentamethyl­cyclopentadienyl) with internal alkynes has been studied. Reactions of <b>1</b> with dihydrocarbyl-substituted alkynes result in the formation of pentamethyl­cyclopentadienyl hydroxyindenyl sandwich complexes. A divergent reaction pathway is observed in the case of bis­(trimethylsilyl)­acetylene, where a neutral Fe vinylidene is isolated. The reactions of hydrocarbyl trimethylsilyl-substituted alkynes with complex <b>1</b> result in the formation of the pentamethyl­cyclopentadienyl hydroxyindenyl sandwich complexes. This reactivity suggests the necessity of two trimethylsilyl groups for vinylidene formation

Visible Light Sensitization of TiO₂ Nanotubes by Bacteriochlorophyll‑C Dyes for Photoelectrochemical Solar Cells

Biomimetic sensitizers have evolved over millions of years to absorb and utilize sunlight and therefore are highly desirable to produce efficient, low cost, dye-sensitized photoelectrochemical solar cells. We report on the sensitization of TiO₂ nanotubes by bacteriochlorophyll-c (BChl <i>c</i>) extracted from photosynthetic bacteria. BChl <i>c</i> is notable for its high conversion efficiency inside the bacteria, which makes it a promising candidate for a naturally derived sensitizer for TiO₂. A photocurrent conversion efficiency of 0.1% was observed at 600–800 nm, corresponding to the absorption peak in BChl <i>c</i>; a photoanode efficiency of 0.23% was measured at around −0.1 V_SCE. Stability tests under simulated sunlight showed stable photocurrents over the course of 14 min. Mechanisms that currently limit the efficiency include the formation of BChl <i>c</i> aggregates on TiO₂, which may increase recombination, and possibly interface defects, which decrease charge injection to the nanotubes and trapping of photogenerated charges

Camera Method for Monitoring a Mechanochromic Luminescent β‑Diketone Dye with Rapid Recovery

Mechanochromic luminescent (ML) materials, which show a change in emission due to an applied mechanical stimulus, are useful components in a variety of applications, including organic light-emitting diodes, force sensors, optical memory storage, and next-generation lighting materials. While there are many different ML active derivatives, few show room temperature self-erasing. Thin films of the methoxy substituted β-diketone, gbmOMe, initially exhibited blue (428 nm) emission; however, green (478 nm) emission was observed after smearing. The mechanically generated smeared state recovered so rapidly that characterization of its emission was difficult at room temperature using traditional luminescence techniques. Thus, a new complementary metal oxide semiconductor camera imaging method was developed and used to calculate the decay time of the mechanically generated smeared state (i.e., smeared-state decay; τ_SM) for gbmOMe thin films. Additionally, this method was used to evaluate substrate and film thickness effects on ML recovery for glass and weighing paper films. The recovery behavior of gbmOMe was largely substrate-independent for the indicated matrixes; however, thickness effects were observed. Thus, film thickness may be the main factor in determining ML recovery behavior and must be accounted for when comparing the recovery dynamics of different ML materials. Moreover, when heated above the melting point (<i>T</i>_m = 119 °C), bulk gbmOMe powders assumed a metastable state that eventually crystallized after a few minutes at room temperature. However, melted thin films remained in an amorphous state indefinitely despite annealing at different temperatures (50–110 °C). The amorphous phase was identified as a supercooled liquid via changing the rate of cooling in differential scanning calorimetry thermograms

Camera Method for Monitoring a Mechanochromic Luminescent β‑Diketone Dye with Rapid Recovery

Mechanochromic luminescent (ML) materials, which show a change in emission due to an applied mechanical stimulus, are useful components in a variety of applications, including organic light-emitting diodes, force sensors, optical memory storage, and next-generation lighting materials. While there are many different ML active derivatives, few show room temperature self-erasing. Thin films of the methoxy substituted β-diketone, gbmOMe, initially exhibited blue (428 nm) emission; however, green (478 nm) emission was observed after smearing. The mechanically generated smeared state recovered so rapidly that characterization of its emission was difficult at room temperature using traditional luminescence techniques. Thus, a new complementary metal oxide semiconductor camera imaging method was developed and used to calculate the decay time of the mechanically generated smeared state (i.e., smeared-state decay; τ_SM) for gbmOMe thin films. Additionally, this method was used to evaluate substrate and film thickness effects on ML recovery for glass and weighing paper films. The recovery behavior of gbmOMe was largely substrate-independent for the indicated matrixes; however, thickness effects were observed. Thus, film thickness may be the main factor in determining ML recovery behavior and must be accounted for when comparing the recovery dynamics of different ML materials. Moreover, when heated above the melting point (<i>T</i>_m = 119 °C), bulk gbmOMe powders assumed a metastable state that eventually crystallized after a few minutes at room temperature. However, melted thin films remained in an amorphous state indefinitely despite annealing at different temperatures (50–110 °C). The amorphous phase was identified as a supercooled liquid via changing the rate of cooling in differential scanning calorimetry thermograms

Electrocatalytic Reduction of CO₂ to Formate by an Iron Schiff Base Complex

The synthesis, structural characterization, and reactivity of an iron­(III) chloride compound of 6,6′-di­(3,5-di-<i>tert</i>-butyl-2-hydroxybenzene)-2,2′-bipyridine (Fe­(^tbudhbpy)­Cl), under electrochemically reducing conditions is reported. In the presence of carbon dioxide (CO₂) under anhydrous conditions in <i>N,N</i>-dimethylformamide (DMF), this complex mediates the 2e^– reductive disproportionation of two equivalents of CO₂ to carbon monoxide (CO) and carbonate (CO₃^2–). Upon addition of phenol (PhOH) as a proton source under CO₂ saturation, catalytic current is observed; product analysis from controlled potential electrolysis experiments shows the majority product is formate (68 ± 4% Faradaic efficiency), with H₂ as a minor product (30 ± 10% Faradaic efficiency) and minimal CO (1.1 ± 0.3% Faradaic efficiency). On the basis of data obtained from cyclic voltammetry and infrared spectroelectrochemistry (IR-SEC), the release of CO from intermediate Fe carbonyl species is extremely slow and undergoes competitive degradation, limiting the activity and lifetime of this catalyst. Mechanistic studies also indicate the phenolate moieties coordinated to Fe are sensitive to protonation in the reduced state, suggesting the possibility of cooperative pendent proton interactions being involved in CO₂ reduction

Camera Method for Monitoring a Mechanochromic Luminescent β‑Diketone Dye with Rapid Recovery

Mechanochromic luminescent (ML) materials, which show a change in emission due to an applied mechanical stimulus, are useful components in a variety of applications, including organic light-emitting diodes, force sensors, optical memory storage, and next-generation lighting materials. While there are many different ML active derivatives, few show room temperature self-erasing. Thin films of the methoxy substituted β-diketone, gbmOMe, initially exhibited blue (428 nm) emission; however, green (478 nm) emission was observed after smearing. The mechanically generated smeared state recovered so rapidly that characterization of its emission was difficult at room temperature using traditional luminescence techniques. Thus, a new complementary metal oxide semiconductor camera imaging method was developed and used to calculate the decay time of the mechanically generated smeared state (i.e., smeared-state decay; τ_SM) for gbmOMe thin films. Additionally, this method was used to evaluate substrate and film thickness effects on ML recovery for glass and weighing paper films. The recovery behavior of gbmOMe was largely substrate-independent for the indicated matrixes; however, thickness effects were observed. Thus, film thickness may be the main factor in determining ML recovery behavior and must be accounted for when comparing the recovery dynamics of different ML materials. Moreover, when heated above the melting point (<i>T</i>_m = 119 °C), bulk gbmOMe powders assumed a metastable state that eventually crystallized after a few minutes at room temperature. However, melted thin films remained in an amorphous state indefinitely despite annealing at different temperatures (50–110 °C). The amorphous phase was identified as a supercooled liquid via changing the rate of cooling in differential scanning calorimetry thermograms

Combined Furan C–H Activation and Furyl Ring-Opening by an Iron(II) Complex

Cp*Fe­[P­(OCH₂)₃CEt]₂Ph (Cp* = η⁵-1,2,3,4,5-pentamethylcyclopentadienyl, P­(OCH₂)₃CEt = 2,6,7-trioxa-1-phosphabicyclo­[2,2,1]­heptane) reacts with furan and 2-methylfuran under photolytic conditions to selectively activate the α-C–H bond to produce Cp*Fe­[P­(OCH₂)₃CEt]₂(2-furyl) and Cp*Fe­[P­(OCH₂)₃CEt]₂[2-(5-methylfuryl)], respectively. Cp*Fe­[P­(OCH₂)₃CEt]₂(2-furyl) reacts with internal alkynes (2-butyne, 3-hexyne, 1-phenyl-1-propyne) under photolytic conditions to produce sandwich complexes of the type Cp*Fe­[η⁵-C₅R₄(CHCHCHO)] (R = alkyl and/or aryl). Experimental data suggest a mechanism that involves phosphite dissociation and successive alkyne insertions into the Fe–furyl bond followed by furyl ring opening. Similarly, the methylfuryl analogue Cp*Fe­[P­(OCH₂)₃CEt]₂[2-(5-methylfuryl)] reacts with 2-butyne to produce Cp*Fe­[η⁵-C₅Me₄(CHCHCOCH₃)]

Camera Method for Monitoring a Mechanochromic Luminescent β‑Diketone Dye with Rapid Recovery

Mechanochromic luminescent (ML) materials, which show a change in emission due to an applied mechanical stimulus, are useful components in a variety of applications, including organic light-emitting diodes, force sensors, optical memory storage, and next-generation lighting materials. While there are many different ML active derivatives, few show room temperature self-erasing. Thin films of the methoxy substituted β-diketone, gbmOMe, initially exhibited blue (428 nm) emission; however, green (478 nm) emission was observed after smearing. The mechanically generated smeared state recovered so rapidly that characterization of its emission was difficult at room temperature using traditional luminescence techniques. Thus, a new complementary metal oxide semiconductor camera imaging method was developed and used to calculate the decay time of the mechanically generated smeared state (i.e., smeared-state decay; τ_SM) for gbmOMe thin films. Additionally, this method was used to evaluate substrate and film thickness effects on ML recovery for glass and weighing paper films. The recovery behavior of gbmOMe was largely substrate-independent for the indicated matrixes; however, thickness effects were observed. Thus, film thickness may be the main factor in determining ML recovery behavior and must be accounted for when comparing the recovery dynamics of different ML materials. Moreover, when heated above the melting point (<i>T</i>_m = 119 °C), bulk gbmOMe powders assumed a metastable state that eventually crystallized after a few minutes at room temperature. However, melted thin films remained in an amorphous state indefinitely despite annealing at different temperatures (50–110 °C). The amorphous phase was identified as a supercooled liquid via changing the rate of cooling in differential scanning calorimetry thermograms

2,2,2-Tris(pyrazolyl)ethoxide (Ep^OX) Ruthenium(II) Complexes, (Ep^OX)RuCl(L)(L′): Synthesis, Structure, and Reactivity

Treatment of RuCl₂(PPh₃)₃ with sodium 2,2,2-tris­(pyrazolyl)­ethoxide [NaOCH₂C­(pz)₃; pz = pyrazolyl] affords the asymmetric heteroscorpionate complex <i>cis</i>-(Ep^OX)­RuCl­(PPh₃)₂ (<b>1</b>), (Ep^OX = κ³-<i>N,N,O-</i>OCH₂C­(pz)₃), which can be converted to Ru­(II) compounds (<b>2</b>–<b>6</b>), (Ep^OX)­RuCl­(L)­(L′) [(<b>2</b>) L = PPh₃, L′ = P­(OCH₂)₃CEt; (<b>3</b>) L = L′ = P­(OCH₂)₃CEt; (<b>5</b>) L, L′ = PPh₃, CO; (<b>6</b>) L = L′ = CO]. Compounds <b>1</b> and <b>3</b> react with CHCl₃ at 60 and 100 °C, respectively, to yield cationic tris­(pyrazolyl)­methane Ru­(II) complexes, [(κ³-<i>N</i>,<i>N</i>,<i>N</i>-Mp)­RuCl­(L)₂]Cl [Mp = HC­(pz)₃; (<b>7</b>) L = PPh₃; (<b>8</b>) L = P­(OCH₂)₃CEt]. The complexes have been characterized by ¹H, ¹³C, and ³¹P­{¹H} NMR spectroscopy, elemental analysis, high resolution mass spectrometry, and cyclic voltammetry. Complexes <b>1</b> and <b>3</b> have also been characterized by single crystal X-ray analysis

Molecular Recognition of Aliphatic Diamines by 3,3′-Di(trifluoroacetyl)-1,1′-bi-2-naphthol

The fluorescent responses of 3,3′-di­(trifluoroacetyl)-1,1′-bi-2-naphthol toward a variety of amines have been studied. It was found that the aliphatic primary 1,2- and 1,5-diamines can greatly enhance the fluorescence of this compound, but under the same conditions, primary, secondary, and tertiary monoamines cannot turn on the fluorescence of this compound. In addition, this compound was shown to be an enantioselective and diastereoselective fluorescent sensor for chiral diamines. UV absorption and NMR spectroscopic methods have been used to study the interaction of the sensor with amines. These studies have demonstrated that the intramolecular OH···OC hydrogen bonding of the sensor is important for both the reactivity of its trifluoroacetyl group with the amines and its fluorescent responses. The interaction of both of the two amine groups of a diamine molecule with the sensor is essential for the observed fluorescent sensitivity and selectivity