Numerically Exact Simulation of Photodoped Mott Insulators.

A description of long-lived photodoped states in Mott insulators is challenging, as it needs to address exponentially separated timescales. We demonstrate how properties of such states can be computed using numerically exact steady state techniques, in particular, the quantum Monte Carlo algorithm, by using a time-local ansatz for the distribution function with separate Fermi functions for the electron and hole quasiparticles. The simulations show that the Mott gap remains robust to large photodoping, and the photodoped state has hole and electron quasiparticles with strongly renormalized properties.

Titanium(IV) Surface Complexes Bearing Chelating Catecholato Ligands for Enhanced Band-Gap Reduction.

Protonolysis reactions between dimethylamido titanium(IV) catecholate [Ti(CAT)(NMe2)2]2 and neopentanol or tris(tert-butoxy)silanol gave catecholato-bridged dimers [(Ti(CAT)(OCH2tBu)2)(HNMe2)]2 and [Ti(CAT){OSi(OtBu)3}2(HNMe2)2]2, respectively. Analogous reactions using the dimeric dimethylamido titanium(IV) (3,6-di-tert-butyl)catecholate [Ti(CATtBu2-3,6)(NMe2)2]2 yielded the monomeric Ti(CATtBu2-3,6)(OCH2tBu)2(HNMe2)2 and Ti(CATtBu2-3,6)[OSi(OtBu)3]2(HNMe2)2. The neopentoxide complex Ti(CATtBu2-3,6)(OCH2tBu)2(HNMe2)2 engaged in further protonolysis reactions with Si-OH groups and was consequentially used for grafting onto mesoporous silica KIT-6. Upon immobilization, the surface complex [Ti(CATtBu2-3,6)(OCH2tBu)2(HNMe2)2]@[KIT-6] retained the bidentate chelating geometry of the catecholato ligand. This convergent grafting strategy was compared with a sequential and an aqueous approach, which gave either a mixture of bidentate chelating species with a bipodally anchored Ti(IV) center along with other physisorbed surface species or not clearly identifiable surface species. Extension of the convergent and aqueous approaches to anatase mesoporous titania (m-TiO2) enabled optical and electronic investigations of the corresponding surface species, revealing that the band-gap reduction is more pronounced for the bidentate chelating species (convergent approach) than for that obtained via the aqueous approach. The applied methods include X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and solid-state UV/vis spectroscopy. The energy-level alignment for the surface species from the aqueous approach, calculated from experimental data, accounts for the well-known type II excitation mechanism, whereas the findings indicate a distinct excitation mechanism for the bidentate chelating surface species of the material [Ti(CATtBu2-3,6)(OCH2tBu)2(HNMe2)2]@[m-TiO2].

Ontogeny of a tessellated surface: Carapace growth of the longhorn cowfish Lactoria cornuta.

Biological armors derive their mechanical integrity in part from their geometric architectures, often involving tessellations: individual structural elements tiled together to form surface shells. The carapace of boxfish, for example, is composed of mineralized polygonal plates, called scutes, arranged in a complex geometric pattern and nearly completely encasing the body. In contrast to artificial armors, the boxfish exoskeleton grows with the fish; the relationship between the tessellation and the gross structure of the armor is therefore critical to sustained protection throughout growth. To clarify whether or how the boxfish tessellation is maintained or altered with age, we quantify architectural aspects of the tessellated carapace of the longhorn cowfish Lactoria cornuta through ontogeny (across nearly an order of magnitude in standard length) and in a high-throughput fashion, using high-resolution microCT data and segmentation algorithms to characterize the hundreds of scutes that cover each individual. We show that carapace growth is canalized with little variability across individuals: rather than continually adding scutes to enlarge the carapace surface, the number of scutes is surprisingly constant, with scutes increasing in volume, thickness, and especially width with age. As cowfish and their scutes grow, scutes become comparatively thinner, with the scutes at the edges (weak points in a boxy architecture) being some of the thickest and most reinforced in younger animals and thinning most slowly across ontogeny. In contrast, smaller scutes with more variable curvature were found in the limited areas of more complex topology (e.g., around fin insertions, mouth, and anus). Measurements of Gaussian and mean curvature illustrate that cowfish are essentially tessellated boxes throughout life: predominantly zero curvature surfaces comprised of mostly flat scutes, and with scutes with sharp bends used sparingly to form box edges. Since growth of a curved, tiled surface with a fixed number of tiles would require tile restructuring to accommodate the surface's changing radius of curvature, our results therefore illustrate a previously unappreciated advantage of the odd boxfish morphology: by having predominantly flat surfaces, it is the box-like body form that in fact permits a relatively straightforward growth system of this tessellated architecture (i.e., where material is added to scute edges). Our characterization of the ontogeny and maintenance of the carapace tessellation provides insights into the potentially conflicting mechanical, geometric, and developmental constraints of this species but also perspectives into natural strategies for constructing mutable tiled architectures.

Anthraquinone and its derivatives as sustainable materials for electrochemical applications - a joint experimental and theoretical investigation of the redox potential in solution.

Anthraquinone (AQ) has long been identified as a highly promising lead structure for various applications in organic electronics. Considering the enormous number of possible substitution patterns of the AQ lead structure, with only a minority being commercially available, a systematic experimental screening of the associated electrochemical potentials represents a highly challenging and time consuming task, which can be greatly enhanced via suitable virtual pre-screening techniques. In this work the calculated electrochemical reduction potentials of pristine AQ and 12 hydroxy- or/and amino-substituted AQ derivatives in N,N-dimethylformamide have been correlated against newly measured experimental data. In addition to the calculations performed using density functional theory (DFT), the performance of different semi-empirical density functional tight binding (DFTB) approaches has been critically assessed. It was shown that the SCC DFTB/3ob parametrization in conjunction with the COSMO solvation model provides a highly adequate description of the electrochemical potentials also in the case of the two-fold reduced species. While the quality in the correlation against the experimental data proved to be slightly inferior compared to the employed DFT approach, the highly advantageous cost-accuracy ratio of the SCC DFTB/3ob/COSMO framework has important implications in the formulation of hierarchical screening strategies for materials associated with organic electronics. Based on the observed performance, the low-cost method provides sufficiently accurate results to execute efficient pre-screening protocols, which may then be followed by a DFT-based refinement of the best candidate structures to facilitate a systematic search for new, high-performance organic electronic materials.

Structure and Composition of the Eggshell of a Passerine Bird, Setophaga ruticilla (Linnaeus, 1758).

The mineral composition of eggshells is assumed to be a conserved phylogenetic feature. Avian eggshells are composed of calcite, whereas those of taxa within Chelonia are aragonitic. Yet, the eggshells of a passerine bird were reported to be made of aragonite. Here, we report a new study of the same bird eggshells using a combination of in situ microscopy and chemical techniques. A microstructural analysis finds a similar arrangement to other avian eggshells, despite their very thin and fragile nature. Fourier transform infrared spectrometry (FTIR) and electron backscatter diffraction (EBSD) results also confirm that the eggshells are entirely composed of calcite. Our findings demonstrate that passerine eggshells are not an exception and similar to other birds and reinforce the phylogenetic placement of this bird species.

Beyond Takai's Olefination Reagent: Persistent Dehalogenation Emerges in a Chromium(III)-µ3 -Methylidyne Complex.

Reaction of CHI3 with six equivalents of CrCl2 in THF at low temperatures affords [Cr3 Cl3 (µ2 -Cl)3 (µ3 -CH)(thf)6 ] as the first isolable high-yield CrIII µ3 -methylidyne complex. Substitution of the terminal chlorido ligands via salt metathesis with alkali-metal cyclopentadienides generates isostructural half-sandwich chromium(III)-µ3 -methylidynes [CpR 3 Cr3 (µ2 -Cl)3 (µ3 -CH)] (CpR =C5 H5 , C5 Me5 , C5 H4 SiMe3 ). Side and decomposition products of the Cl/CpR exchange reactions were identified and structurally characterized for [Cr4 (µ2 -Cl)4 (µ2 -I)2 (µ4 -O)(thf)4 ] and [(η5 -C5 H4 SiMe3 )CrCl(µ2 -Cl)2 Li(thf)2 ]. The Cl/CpR exchange drastically changed the ambient-temperature effective magnetic moment µeff from 9.30/9.11 µB (solution/solid) to 3.63/4.32 µB (CpR =C5 Me5 ). Reactions of [Cr3 Cl3 (µ2 -Cl)3 (µ3 -CH)(thf)6 ] with aldehydes and ketones produce intricate mixtures of species through oxy/methylidyne exchange, which were partially identified as radical recombination products through GC/MS analysis and 1 H NMR spectroscopy.

webKnossos: efficient online 3D data annotation for connectomics.

We report webKnossos, an in-browser annotation tool for 3D electron microscopic data. webKnossos provides flight mode, a single-view egocentric reconstruction method enabling trained annotator crowds to reconstruct at a speed of 1.5 ± 0.6 mm/h for axons and 2.1 ± 0.9 mm/h for dendrites in 3D electron microscopic data from mammalian cortex. webKnossos accelerates neurite reconstruction for connectomics by 4- to 13-fold compared with current state-of-the-art tools, thus extending the range of connectomes that can realistically be mapped in the future.

Emergence of a New [NNN] Pincer Ligand via Si-H Bond Activation and ß-Hydride Abstraction at Tetravalent Cerium.

The cerium(IV) pyrazolate complexes [Ce(Me2 pz)4 ]2 and [Ce(Me2 pz)4 (thf)] initiate ß-hydride abstraction of the bis(dimethylsilyl)amido moiety, to afford a heteroleptic cerium(IV) species containing a dimethylpyrazolyl-substituted silylamido ligand, namely [Ce(Me2 pz)3 (bpsa)] (bpsa=bis((3,5-dimethylpyrazol-1-yl)dimethylsilyl)amido; Me2 pz =3,5-dimethylpyrazolato), along with some cerium(III) species. Remarkably, the nucleophilic attack of the pyrazolyl at the silicon atom and concomitant Si-H-bond cleavage is restricted to the tetravalent cerium oxidation state and appears to proceed via the formation of a transient cerium(IV) hydride, which engages in immediate redox chemistry. When [Ce(Me2 pz)4 ]2 is treated with [Li{N(SiMe3 )2 }], that is, in the absence of the SiH functionality, any redox chemistry did not occur. Instead, the ceric ate complex [LiCe2 (Me2 pz)9 ] and the stable mixed-ligand ceric species [Ce(Me2 pz)2 {N(SiMe3 )2 }2 ] were obtained.

Perylenetetracarboxylic Diimide as Diffusion-Less Electrode Material for High-Rate Organic Na-Ion Batteries.

In this work 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) is investigated as electrode material for organic Na-ion batteries. Since PTCDI is a widely used industrial pigment, it may turn out to be a cost-effective, abundant, and environmentally benign cathode material for secondary Na-ion batteries. Among other carbonyl pigments, PTCDI is especially interesting due to its high Na-storage capacity in combination with remarkable high rate capabilities. The detailed analysis of cyclic voltammetry measurements reveals a diffusion-less mechanism, suggesting that Na-ion storage in the PTCDI film allows for exceptionally fast charging/discharging rates. This finding is further corroborated by galvanostatic sodiation measurements at high rates of 17 C (2.3 A g-1 ), showing that 57 % of the theoretically possible capacity of PTCDI, or 78 mAh g-1 , are attained in only 3.5 min charging time.

Oligoanalgesia in Patients With an Initial Glasgow Coma Scale Score ≥8 in a Physician-Staffed Helicopter Emergency Medical Service: A Multicentric Secondary Data Analysis of >100,000 Out-of-Hospital Emergency Missions.

BACKGROUND: Oligoanalgesia, as well as adverse events related to the initiated pain therapy, is prevalent in out-of-hospital emergency medicine, even when a physician is present. We sought to identify factors involved in insufficient pain therapy of patients presenting with an initial Glasgow Coma Scale (GCS) score of ≥8 in the out-of-hospital phase, when therapy is provided by a physician-staffed helicopter emergency medical service (p-HEMS). METHODS: This was a multicenter, secondary data analysis of conscious patients treated in primary p-HEMS missions between January 1, 2005, and December 31, 2017. Patients with a numeric rating scale (NRS) pain score ≥4, GCS score ≥8 on the scene, without cardiopulmonary resuscitation (CPR), and a National Advisory Committee for Aeronautics (NACA) score

Effective and Reversible Carbon Dioxide Insertion into Cerium Pyrazolates.

The homoleptic pyrazolate complexes [CeIII 4 (Me2 pz)12 ] and [CeIV (Me2 pz)4 ]2 quantitatively insert CO2 to give [CeIII 4 (Me2 pz⋅CO2 )12 ] and [CeIV (Me2 pz⋅CO2 )4 ], respectively (Me2 pz=3,5-dimethylpyrazolato). This process is reversible for both complexes, as observed by in situ IR and NMR spectroscopy in solution and by TGA in the solid state. By adjusting the molar ratio, one molecule of CO2 per [CeIV (Me2 pz)4 ] complex could be inserted to give trimetallic [Ce3 (Me2 pz)9 (Me2 pz⋅CO2 )3 (thf)]. Both the cerous and ceric insertion products catalyze the formation of cyclic carbonates from epoxides and CO2 under mild conditions. In the absence of epoxide, the ceric catalyst is prone to reduction by the co-catalyst tetra-n-butylammonium bromide (TBAB).

Trapping CS22- and S32- between Two Ytterbium Formamidinates.

Treatment of [YbII(DippForm)2(thf) n] ( n = 2 (1aYb), n = 1 (1bYb); DippForm = N, N'-bis(2,6-diisopropylphenyl)formamidinate), with either excess CS2 or S8 gives [YbIII2(DippForm)4(CS2)] (3) and [YbIII2(DippForm)4(S2)0.5/(S3)0.5] (4) respectively. 3 is a new addition to an exclusive class of compounds containing the CS22- dianion, and 4 is the first crystallographically characterized example of a rare-earth trisulfide complex.

C-H-Bond Activation and Isoprene Polymerization Studies Applying Pentamethylcyclopentadienyl-Supported Rare-Earth-Metal Bis(Tetramethylaluminate) and Dimethyl Complexes.

As previously shown for lutetium and yttrium, 1,2,3,4,5-pentamethylcyclopentadienyl (C5Me5 = Cp*)-bearing rare-earth metal dimethyl half-sandwich complexes [Cp*LnMe2]3 are now also accessible for holmium, dysprosium, and terbium via tetramethylaluminato cleavage of [Cp*Ln(AlMe4)2] with diethyl ether (Ho, Dy) and tert-butyl methyl ether (TBME) (Tb). C-H-bond activation and ligand redistribution reactions are observed in case of terbium and are dominant for the next larger-sized gadolinium, as evidenced by the formation of mixed methyl/methylidene clusters [(Cp*Ln)5(CH2)(Me)8] and metallocene dimers [Cp*2Ln(AlMe4)]2 (Ln = Tb, Gd). Applying TBME as a "cleaving" reagent can result in both TBME deprotonation and ether cleavage, as shown for the formation of the 24-membered macrocycle [(Cp*Gd)2(Me)(CH2OtBu)2(AlMe4)]4 or monolanthanum complex [Cp*La(AlMe4){Me3Al(CH2)OtBu}] and monoyttrium complex [Cp*Y(AlMe4)(Me3AlOtBu)], respectively. Complexes [Cp*Ln(AlMe4)2] (Ln = Ho, Dy, Tb, Gd) and [Cp*LnMe2]3 (Ln = Ho, Dy) are applied in isoprene and 1,3-butadiene polymerization, upon activation with borates [Ph3C][B(C6F5)4] and [PhNHMe2][B(C6F5)4], as well as borane B(C6F5)3. The trans-directing effect of AlMe3 in the binary systems [Cp*Ln(AlMe4)2]/borate is revealed and further corroborated by the fabrication of high-cis-1,4 polybutadiene (97%) with "aluminum-free" [Cp*DyMe2]3/[Ph3C][B(C6F5)4]. The formation of multimetallic active species is supported by the polymerization activity of pre-isolated cluster [(Cp*Ho)3Me4(CH2)(thf)2].

Unveiling the Takai Olefination Reagent via Tris( tert-butoxy)siloxy Variants.

The elusive Takai olefination reagent, namely, the iodo-methylidene Cr(III) complex [Cr2Cl4(CHI)(thf)4], has been isolated by careful handling of the reaction between CrCl2 and CHI3 in THF at -35 °C. Alternatively, treatment of [Cr(OSi(O tBu)3)2] with CHI3 gave the mixed-valent dihalido-methanide complex [CrII/III2I2(OSi(O tBu)3)2(CHI2)], featuring a Cr(III)-CHI2 moiety. In the presence of TMEDA nucleophilic attack at CHI2 occurred generating the zwitterionic species [CrIII(OSi(O tBu)3)2(tmeda-CHI)][I]. Complexes [Cr2Cl4(CHI)(thf)4] and [CrII/III2I2(OSi(O tBu)3)2(CHI2)] were screened for their ability to induce monohalido olefination of benzaldehyde. Remarkably, both complexes promote olefination, with [Cr2Cl4(CHI)(thf)4] accomplishing the same E selectivity as Takai 's original mixture. Complex [CrII/III2I2(OSi(O tBu)3)2(CHI2)], however, appeared to give preferentially Z isomer, corroborating the monoiodo-methylidene species Cr(III)-CHI-Cr(III) as the active olefination component of the original in situ generated Takai reagent mixture.

Blood glucose concentrations in prehospital trauma patients with traumatic shock: A retrospective analysis.

BACKGROUND: Deranged glucose metabolism after moderate to severe trauma with either high or low concentrations of blood glucose is associated with poorer outcome. Data on prehospital blood glucose concentrations and trauma are scarce. OBJECTIVES: The primary aim was to describe the relationship between traumatic shock and prehospital blood glucose concentrations. The secondary aim was to determine the additional predictive value of prehospital blood glucose concentration for traumatic shock when compared with vital parameters alone. DESIGN: Retrospective analysis of the predefined, observational database of a nationwide Helicopter Emergency Medical Service (34 bases). SETTING: Emergency trauma patients treated by Helicopter Emergency Medical Service between 2005 and 2013 were investigated. PATIENTS: All adult trauma patients (≥18 years) with recorded blood glucose concentrations were enrolled. OUTCOMES: Primary outcome: upper and lower thresholds of blood glucose concentration more commonly associated with traumatic shock. Secondary outcome: additional predictive value of prehospital blood glucose concentrations when compared with vital parameters alone. RESULTS: Of 51 936 trauma patients, 20 177 were included. In total, 220 (1.1%) patients died on scene. Hypoglycaemia (blood glucose concentration 2.8 mmol l or less) was observed in 132 (0.7%) patients, hyperglycaemia (blood glucose concentration exceeding 15 mmol l) was observed in 265 patients (1.3%). Blood glucose concentrations more than 10 mmol l (n = 1308 (6.5%)) and 2.8 mmol l or less were more common in patients with traumatic shock (P < 0.0001). The Youden index for traumatic shock ((sensitivity + specificity) - 1) was highest when blood glucose concentration was 3.35 mmol l (P < 0.001) for patients with low blood glucose concentrations and 7.75 mmol l (P < 0.001) for those with high blood glucose concentrations. In logistic regression analysis of patients with spontaneous circulation on scene, prehospital blood glucose concentrations (together with common vital parameters: Glasgow Coma Scale, heart rate, blood pressure, breathing frequency) significantly improved the prediction of traumatic shock in comparison with prediction by common vital parameters alone (P < 0.0001). CONCLUSION: In adult trauma patients, low and high blood glucose concentrations were more common in patients with traumatic shock. Prehospital blood glucose concentration measurements in addition to common vital parameters may help identify patients at risk of traumatic shock.

Bulky Ytterbium Formamidinates Stabilise Complexes with Radical Ligands, and Related Samarium "Tetracyclone" Chemistry.

Divalent [Yb(DippForm)2 (thf)n ] (n=2 (1 a), or 1 (1 b), DippForm=N,N'-bis(2,6-diisopropylphenyl)formamidinate) complexes were treated with the ketones: 9-fluorenone (fn), or 2,3,4,5-tetraphenylcyclopentadienone (tpc, tetracyclone), giving ketyl complexes: [Yb(DippForm)2 (fn. -O)(thf)] (2), and [Yb(DippForm)2 (tpc. -O)] (3), respectively (ketyl=a radical anion containing a C. -O(-) group. By contrast, when perfluorobenzophenone (pfb) was treated with either 1 a or 1 b, transitory ketyl formation was followed by rapid decomposition through a C-F activation pathway, giving [YbF(DippForm)2 (thf)] (4 a) and a highly unusual fluoride/oxide-bridged species: [Yb5 F6 O2 (DippForm)5 ] (4 b). The reduction of diketones: 3,5-di-tert-butyl-1,2-benzoquinone (tbbq), 9,10-phenanthrenequinone (phen), or 1,2-acenaphthenequinone (acen), was also examined giving ketyl complexes: [Yb(DippForm)2 (tbbq. -O2 )] (5), [Yb(DippForm)2 (phen. -O2 )] (6), and [Yb(DippForm)2 (acen. -O2 )(thf)] (7). An unsolvated derivative of 7, namely [Yb(DippForm)2 (acen. -O2 )] (8), was obtained from PhMe. All ketyl complexes had suitably elongated C. -O bonds, were stable in both polar and non-polar solvents-an uncommon trait for rare-earth ketyl complexes-and, with the exception of 3, showed radical signals in ESR spectra. To investigate the reactivity of the tpc. -O ketyl complex, 3 was treated with oxidants (CS2 , Se) and reducing agents (Mg0 , KH, or [SmI2 (thf)2 ]). Thus 3 was oxidised to tpc by Se. Treatment of 3 with KH led to a ligand exchange process giving an unusual diketyl species [Yb(DippForm)(tpc. -O)2 (thf)2 ] (10), which has two cisoid tpc. -O- ligands in very close proximity. When treated with [SmI2 (thf)2 ], the tpc. -O ketyl was further reduced to a dianion (1-oxido-2,3,4,5-tetraphenylcyclopentadianide2- ), ({C5 Ph4 }-O)2- by [SmI2 (thf)2 ], giving dimeric [{SmI({C5 Ph4 }-O)(thf)2 }2 ] (Sm11) and monomeric complexes [YbI(DippForm)2 (thf)] (11 b) and [YbI2 (DippForm)(thf)2 ] (11 c). Activated Sm metal reduced neutral tetracyclone to the dianion, ({C5 Ph4 }-O)2- , in THF, giving tetranuclear [{SmII2 ({C5 Ph4 }-O)2 (thf)3 }2 ] (Sm13). Treatment of Sm13 with iodine in situ provided access to [{SmI({C5 Ph4 }-O)(thf)2 }2 ] (Sm11), in good yield.

Enhancing the Value of Free Metals in the Synthesis of Lanthanoid Formamidinates: Is a Co-oxidant Needed?

Treatment of N,N'-bis(aryl)formamidines (ArFormH), N,N'-bis(2,6-difluorophenyl)formamidine (DFFormH) or N,N'-bis(2,6-diisopropylphenyl)formamidine (DippFormH), with europium metal in CH3 CN is an efficient synthesis of the divalent complexes: [{Eu(DFForm)2 (CH3 CN)2 }2 ] (Eu1) or [Eu(DippForm)2 (CH3 CN)4 ] (Eu2). The synthetic method was extended to ytterbium, but the metal required activation by addition of Hg(0) . With DFFormH in CH3 CN, [{Yb(DFForm)2 (CH3 CN)}2 ] (Yb1) was obtained in good yield, and [Yb(DFForm)2 (thf)3 ] (Yb3) was obtained from a synthesis in CH3 CN/THF. Thus, this synthetic method completely circumvents the use of either salt metathesis, or redox transmetallation/protolysis (RTP) protocols to prepare divalent rare-earth formamidinates. Heating Yb1 in PhMe/C6 D6 resulted in decomposition to trivalent products, including one from a CH3 CN activation process. For a synthetic comparison, divalent ytterbium DFForm and DippForm complexes were synthesised by RTP reactions between Yb(0) , Hg(R)2 (R=Ph, C6 F5 ), and ArFormH in THF, leading to the isolation of either [Yb(DFForm)2 (thf)3 ] (Yb3), or the first five coordinate rare-earth formamidinate complex [Yb(DippForm)2 (thf)] (Yb4 b), and, from adjustment of the stoichiometry, trivalent [Yb(DFForm)3 (thf)] (Yb6). Oxidation of Yb3 with benzophenone (bp), or halogenating agents (TiCl4 (thf)2 , Ph3 CCl, C2 Cl6 ) gave [Yb(DFForm)3 (bp)] or [Yb(DFForm)2 Cl(thf)2 ], respectively. Furthermore, the structural chemistry of divalent ArForm complexes has been substantially broadened. Not only have the highest and lowest coordination numbers for divalent rare-earth ArForm complexes been achieved in Eu2 and Yb4 b, respectively, but also dimeric Eu1 and Yb1 have highly unusual ArForm bridging coordination modes, either perpendicular µ-1κ(N:N'):2κ(N:N') in Eu1, or the twisted µ-1κ(N:N'):2κ(N':F') DFForm coordination in Yb1, both unprecedented in divalent rare-earth ArForm chemistry and in the wider divalent rare-earth amidinate field.

Cerium(III/IV) formamidinate chemistry, and a stable cerium(IV) diolate.

Four new cerium(III) formamidinate complexes comprising [Ce(p-TolForm)3 ], [Ce(DFForm)3 (thf)2 ], [Ce(DFForm)3 ], and [Ce(EtForm)3 ] were synthesized by protonolysis reactions using [Ce{N(SiMe3 )2 }3 ] and formamidines of varying functionality, namely N,N'-bis(4-methylphenyl)formamidine (p-TolFormH), N,N'-bis(2,6-difluorophenyl)formamidine (DFFormH), and the sterically more demanding N,N'-bis(2,6-diethylphenyl)formamidine (EtFormH). The bimetallic cerium lithium complex [LiCe(DFForm)4 ] was synthesized by treating a mixture of [Ce{N(SiHMe2 )2 }3 (thf)2 ] and [Li{N(SiHMe2 )2 }] with four equivalents of DFFormH in toluene. Oxidation of the trivalent cerium(III) formamidinate complexes by trityl chloride (Ph3 CCl) caused dramatic color changes, although the cerium(IV) species appeared transient and reformed cerium(III) complexes and N'-trityl-N,N'-diarylformamidines shortly after oxidation. The first structurally characterized homoleptic cerium(IV) formamidinate complex [Ce(p-TolForm)4 ] was obtained through a protonolysis reaction between [Ce{N(SiHMe2 )2 }4 ] and four equivalents of p-TolFormH. [Ce{N(SiHMe2 )2 }4 ] was also treated with DFFormH and EtFormH, but the resulting cerium(IV) complexes decomposed before isolation was possible. The new cerium(IV) silylamide complex [Ce{N(SiMe3 )2 }3 (bda)0.5 ]2 (bda=1,4-benzenediolato) was synthesized by treatment of [Ce{N(SiMe3 )2 }3 ] with half an equivalent of 1,4-benzoquinone, and showed remarkable resistance towards protonolysis or reduction.

Picosecond-to-nanosecond dynamics of plasmonic nanobubbles from pump-probe spectral measurements of aqueous colloidal gold nanoparticles.

The photothermal generation of nanoscale vapor bubbles around noble metal nanoparticles is of significant interest, not only in understanding the underlying mechanisms responsible for photothermal effects, but also to optimize photothermal effects in applications such as photothermal cancer therapies. Here, we describe the dynamics in the 400-900 nm regime of the formation and evolution of nanobubbles around colloidal gold nanoparticles using picosecond pump-probe optical measurements. From excitations of 20-150 nm colloidal gold nanoparticles with a 355 nm, 15 ps laser, time-dependent optical extinction signals corresponding to nanobubble formation were recorded. The extinction spectra associated with nanobubbles of different diameters were simulated by considering a concentric spherical core-shell model within the Mie theory framework. In the simulations, we assumed an increase in particle temperature. From temporal changes in the experimental data of transient extinctions, we estimated the temporal evolution of the nanobubble diameter. Corrections to bubble-free temperature effects on the transient extinction decays were applied in these experiments by suppressing bubble formation using pressures as high as 60 MPa. The results of this study suggest that the nanobubbles generated around a 60 nm-diameter gold nanoparticle using a fluence of 5.2 mJ cm(-2) had a maximum diameter of 260 ± 40 nm, and a lifetime of approximately 10 ns. The combination of fast transient extinction spectral measurements and spectral simulations provides insights into plasmonic nanobubble dynamics.

Reactivity of bulky formamidinatosamarium(II or III) complexes with C═O and C═S bonds.

The preparation of a new heterobimetallic samarium(II) formamidinate complex and selected reactions of samarium(II) complexes and one samarium(III) formamidinate complex with benzophenone or CS2 are discussed. Treatment of the tris(formamidinato)samarium(III) complex [Sm(DippForm)3] 1 (DippForm = N,N'-bis(2,6-diisopropylphenyl)formamidinate, (CH(NC6H3-(i)Pr2-2,6)2) with potassium graphite in toluene yielded the dark brown heterobimetallic formamidinatosamarium(II)/potassium complex [KSm(DippForm)3]n 2. Divalent 2, a Lewis base solvent free homoleptic species, differs significantly from the related heteroleptic formamidinatosamarium(II) complex [Sm(DippForm)2(thf)2] 3 with respect to its constitution, structure, and reactivity toward benzophenone. While 2 reacts giving complex 1, the reaction of 3 with benzophenone generates the highly unusual [Sm(DippForm)2(thf){µ-OC(Ph)═(C6H5)C(Ph)2O}Sm(DippForm)2] (C6H5 = 1,4-cyclohexadiene-3-yl-6-ylidene) 4. The formation of 4 highlights a rare C-C coupling between a carbonyl carbon and the carbon at the para position of a phenyl group of the OCPh2 fragment. An analogous reaction of [Yb(DippForm)2(thf)2] gives an isostructural complex 4Yb. 3 reacts with carbon disulfide forming a light green dinuclear formamidinatosamarium(III) complex [{Sm(DippForm)2(thf)}2(µ-η(2)(C,S):κ(S',S″)-SCSCS2)] 5 through an unusual C-S coupling induced by an amidinatolanthanoid species giving the thioformylcarbonotrithioate ligand. The trivalent organometallic [Sm(DippForm)2(CCPh)(thf)] complex activates the C═O bond of benzophenone by an insertion reaction, forming the light yellow [Sm(DippForm)2{OC(Ph)2C2Ph}(thf)] 6 as a major product and light yellow unsolvated [Sm(DippForm)2{OC(Ph)2C2Ph}] 7 as a minor product. Molecular structures of complexes (2, 4-7) show that κ(N,N') bonding between a DippForm and samarium atom exists in all compounds, but in 2, DippForm also bridges K and Sm by 1κ(N):2κ(N') bonding and two 2,6-diisopropylphenyl groups are η(6)-bonded to potassium.