Au Distance Research Articles

Jupiter’s Formation in the Vicinity of the Amorphous Ice Snowline

Abstract Argon, krypton, xenon, carbon, nitrogen, sulfur, and phosphorus have all been measured and found to be enriched by a quasi uniform factor in the 2–4 range, compared to their protosolar values, in the atmosphere of Jupiter. To elucidate the origin of these volatile enrichments, we investigate the possibility of an inward drift of particles made of amorphous ice and adsorbed volatiles, and their ability to enrich in heavy elements the gas phase of the protosolar nebula, once they cross the amorphous-to-crystalline ice transition zone, following the original idea formulated by Monga & Desch. To do so, we use a simple accretion disk model coupled to modules depicting the radial evolution of icy particles and vapors, assuming growth, fragmentation, and crystallization of amorphous grains. We show that it is possible to accrete supersolar gas from the nebula onto proto-Jupiter’s core to form its envelope, and allowing it to match the observed volatile enrichments. Our calculations suggest that nebular gas, with a metallicity similar to that measured in Jupiter, can be accreted by its envelope if the planet is formed in the ∼0.5–2 Myr time range and in the 0.5–20 au distance range from the Sun, depending on the adopted viscosity parameter of the disk. These values match a wide range of Jupiter’s formation scenarios, including in situ formation and migration/formation models.

An estimate of the k2 Love number of WASP-18Ab from its radial velocity measurements

Context. Increasing our knowledge of the interior structure, composition, and density distribution of exoplanets is crucial to make progress in the understanding of exoplanetary formation, migration and habitability. However, the directly measurable mass and radius values offer little constraint on interior structure, because the inverse problem is highly degenerate. Therefore, there is a clear need for a third observable of exoplanet interiors. This third observable can be the k2 fluid Love number which measures the central mass concentration of an exoplanet. Aims. The aims of this paper are (i) to develop a basic model to fit the long-term radial velocity and TTV variations caused by tidal interactions, (ii) to apply the model to the WASP-18Ab system, and (iii) to estimate the Love number of the planet. Methods. Archival radial velocity, transit and occultation timing data were collected and fitted using the model introduced here. Results. The best model fit to the archival radial velocity and timing data of WASP-18Ab was obtained with a Love number of the massive (~10 MJup) hot Jupiter WASP-18Ab: k2,Love = 0.62−0.19+0.55. This causes apsidal motion in the system, at a rate of ~0.0087 ± 0.0033°∕days ≊ 31.3 ± 11.8 arcsec day−1. When checking possible causes of periastron precession, other than the relativistic term or the non-spherical shape of the components, we found a companion star to the WASP-18 system, named WASP-18B which is a probable M6.5V dwarf with ~0.1 M⊙ at 3519 AU distance from the transit host star. We also find that small orbital eccentricities may be real, rather than an apparent effect caused by the non-spherical stellar shape.

4-Pyridylisocyanide gold(i) and gold(i)-plus-silver(i) luminescent and mechanochromic materials: the silver role.

Crystallographic and DFT examination of the metalloligands [AuAr(CNPy-4)] (Ar = C6F5 (1), C6F3Cl2-3,5 (2)) and their silver complexes [Ag[AuAr(CNPy-4)]2](BF4) (3 and 4) support that the marked luminescence red-shifts observed on moving from 1 to 2, from 1,2 to 3,4, or upon grinding, are not caused by electronic differences (either by changing the aryls C6F5/C6F3Cl2, or by N coordination to silver), nor by non-existent AuAg interactions. They are always due to structural changes disturbing stronger π-π stackings in order to allow for shorter AuAu interactions.

Heliospheric modulation of the interstellar dust flow on to Earth

Aims. Based on measurements by the Ulysses spacecraft and high-resolution modelling of the motion of interstellar dust (ISD) through the heliosphere we predict the ISD flow in the inner planetary system and on to the Earth. This is the third paper in a series of three about the flow and filtering of the ISD. Methods. Micrometer- and sub-micrometer-sized dust particles are subject to solar gravity and radiation pressure as well as to interactions with the interplanetary magnetic field that result in a complex size-dependent flow pattern of ISD in the planetary system. With high-resolution dynamical modelling we study the time-resolved flux and mass distribution of ISD and assess the necessary requirements for detection of ISD near the Earth. Results. Along the Earth orbit the density, speed, and flow direction of ISD depend strongly on the Earth’s position and the size of the interstellar grains. A broad maximum of the ISD flux (~2 × 10−4 m−2 s−1 of particles with radii ≳0.3 μm) occurs in March when the Earth moves against the ISD flow. During this time period the relative speed with respect to the Earth is highest (~60 km s-1), whereas in September when the Earth moves with the ISD flow, both the flux and the speed are lowest (≲10 km s-1). The mean ISD mass flow on to the Earth is approximately 100 kg yr-1 with the highest flux of ~3.5 kg day-1 occurring for about 2 weeks close to the end of the year when the Earth passes near the narrow gravitational focus region of the incoming ISD flow, downstream from the Sun. The phase of the 22-year solar wind cycle has a strong effect on the number density and flow of sub-micrometer-sized ISD particles. During the years of maximum electromagnetic focussing (year 2031 +/− 3) there is a chance that ISD particles with sizes even below 0.1 μm can reach the Earth. Conclusions. We demonstrate that ISD can be effectively detected, analysed, and even collected by space probes at 1 AU distance from the Sun.

Modelling mid-infrared molecular emission lines from T Tauri stars

We introduce a new modelling framework including the Fast Line Tracer (FLITS) to simulate infrared line emission spectra from protoplanetary discs. This paper focusses on the mid-IR spectral region between 9.7 and 40 μm for T Tauri stars. The generated spectra contain several tens of thousands of molecular emission lines of H2O, OH, CO, CO2, HCN, C2H2, H2, and a few other molecules, as well as the forbidden atomic emission lines of S I, S II, S III, Si II, Fe II, Ne II, Ne III, Ar II, and Ar III. In contrast to previously published works, we do not treat the abundances of the molecules nor the temperature in the disc as free parameters, but use the complex results of detailed 2D PRODIMO disc models concerning gas and dust temperature structure, and molecular concentrations. FLITS computes the line emission spectra by ray tracing in an efficient, fast, and reliable way. The results are broadly consistent with R = 600 Spitzer/IRS observational data of T Tauri stars concerning line strengths, colour, and line ratios. In order to achieve that agreement, however, we need to assume either a high gas/dust mass ratio of order 1000, or the presence of illuminated disc walls at distances of a few au, for example, due to disc–planet interactions. These walls are irradiated and heated by the star which causes the molecules to emit strongly in the mid-IR. The molecules in the walls cannot be photodissociated easily by UV because of the large densities in the walls favouring their re-formation. Most observable molecular emission lines are found to be optically thick. An abundance analysis is hence not straightforward, and the results of simple slab models concerning molecular column densities can be misleading. We find that the difference between gas and dust temperatures in the disc surface is important for the line formation. The mid-IR emission features of different molecules probe the gas temperature at different depths in the disc, along the following sequence: OH (highest)–CO–H2O and CO2–HCN–C2H2 (deepest), just where these molecules start to become abundant. We briefly discuss the effects of C/O ratio and choice of chemical rate network on these results. Our analysis offers new ways to infer the chemical and temperature structure of T Tauri discs from future James Webb Space Telescope (JWST)/MIRI observations, and to possibly detect secondary illuminated disc walls based on their specific mid-IR molecular signature.

The Influence of Planet Nine on the Orbits of Distant TNOs: The Case for a Low-perihelion Planet

Abstract The hypothesis of an additional planet in the outer solar system has gained new support as a result of the confinement noted in the angular orbital elements of distant trans-Neptunian objects. Orbital parameters proposed for the external perturber suggest semimajor axes between 500 and 1000 au, perihelion distances between 200 and 400 au for masses between 10 and 20 M ⊕. In this paper, we study the possibility that lower perihelion distances for the additional planet can lead to angular confinements as observed in the population of objects with semimajor axes greater than 250 au and perihelion distances higher than 40 au. We performed numerical integrations of a set of particles subjected to the influence of the Sun, the known giant planets, and the putative perturber during the age of the solar system and compared our outputs with the observed population through a statistical analysis. Our investigations showed that lower perihelion distances from the outer planet usually lead to more substantial confinements than higher ones, while retaining the Classical Kuiper Belt as well as the ratio of the number of detached with perihelion distances higher than 42 au to scattering objects in the range of semimajor axes from 100 to 200 au.

A Fruit of a Different Kind: 2015 BP519 as an Outlier Among the Extreme Trans-neptunian Objects

A number of intriguing patterns have been identified in the distributions of the orbital elements of the known extreme trans-Neptunian objects or ETNOs --those with semimajor axis greater than 150 au and perihelion distance greater than 30 au. The announcement of the discovery of 2015 BP519, also known as Caju, has been hailed by some as a consistent piece of robust evidence for the existence of a yet-to-be-discovered massive planet far beyond the trans-Neptunian belt. In this Note, we use the latest data available to provide evidence against 2015 BP519 having followed the same dynamical pathway that placed other ETNOs where they are now. As an statistical outlier within the 29 known ETNOs, 2015 BP519 cannot be used as a reference to further support the trends perhaps present for other ETNOs. Asteroid 2015 BP519 represents a case of extreme dynamical anticorrelation within the ETNO orbital realm and the value of the distance to its descending node, nearly 700 au from the Sun, is the largest of any known ETNO.

Particle accretion onto planets in discs with hydrodynamic turbulence

The growth process of protoplanets can be sped up by accreting a large number of solid, pebble-sized objects that are still present in the protoplanetary disc. It is still an open question on how efficient this process works in realistic turbulent discs. We investigate the accretion of pebbles in turbulent discs that are driven by the purely hydrodynamical vertical shear instability (VSI). For this purpose, we performed global 3D simulations of locally isothermal, VSI turbulent discs that have embedded protoplanetary cores from 5 to 100 M⊕, which are placed at 5.2 au distance from the star. In addition, we followed the evolution of a swarm of embedded pebbles of different sizes under the action of drag forces between gas and particles in this turbulent flow. Simultaneously, we performed a set of comparison simulations for laminar viscous discs where the particles experience stochastic kicks. For both cases, we measured the accretion rate onto the cores as a function of core mass and Stokes number (τs) of the particles and compared these values to recent magneto-rotational instability (MRI) turbulence simulations. Overall the dynamic is very similar for the particles in the VSI turbulent disc and the laminar case with stochastic kicks. For small mass planets (i.e. 5–10 M⊕), well-coupled particles with τs = 1, which have a size of about 1 m at this location, we find an accretion efficiency (rate of particles accreted over drifting inwards) of about 1.6−3%. For smaller and larger particles, this efficiency is higher. However, the fast inwards drift for τs = 1 particles makes them the most effective for rapid growth, leading to mass doubling times of about 20 000 yr. For masses between 10 and 30 M⊕ the core reaches the pebble isolation mass and the particles are trapped at the pressure maximum just outside of the planet, shutting off further particle accretion.

V1094 Scorpii: A rare giant multi-ringed disk around a T Tauri star

Context. A wide variety of ring-like dust structures have been detected in protoplanetary disks, but their origin and frequency are still unclear. Aims. We aim to characterize the structure of an extended, multi-ringed disk discovered serendipitously in the Atacama Large Millimeter/submillimeter Array (ALMA) Lupus disk survey and put it in the context of the Lupus disk population. Methods. ALMA observations in Band 6 at 234 GHz and Band 7 at 328 GHz at 0.3″ resolution toward the K6 star V1094 Sco in Lupus III are presented, and its disk structure analyzed. The spectral index αmm is determined in the inner 150 AU of the disk. Results. The ALMA continuum data show a very extended disk with two gap-ring pairs. The gaps are located at 100 AU and 170 AU, the bright rings at 130 AU and 220 AU. Continuum emission is detected out to a 300 AU distance, similar to IM Lup but a factor of five larger than typically found for Lupus disks at this sensitivity and resolution. The bright central region of the disk (within 35 AU) is possibly optically thick at 1 mm wavelengths, and has a brightness temperature of only 13 K. The spectral index increases between the inner disk and the first ring at the location of the first gap. Conclusions. Due to the low temperature of the disk midplane, snow lines can be excluded as the drivers behind the ring and gap formation in this disk. Disks the size of V1094 Sco are rare, and only 2.1 ± 1.5% of disks in Lupus show continuum emission beyond 200 AU. Possible connections between the large primordial disk population, transition disks, and exoplanets are discussed.

Controlling the solid-state luminescence of gold(I) N-heterocyclic carbene complexes through changes in the structure of molecular aggregates

Thermally stable, solid-state luminescent organic materials are highly desired for the development of practical applications. Herein we synthesized new gold(I) complexes with N -heterocyclic carbene ligands, which have the ability to form strong metal-organic bond. Consequently, their thermochemical stability is enhanced at temperatures around 300 °C. Precise design of the molecular structure of the ligands, with a focus on ensuring low steric hindrance around Au atoms in order to limit disturbances to Au/Au interactions, provided a complex with a densely packed crystal with a shorter intermolecular Au–Au distance (3.17 A) than the typical distance. In the solid state, this complex exhibited strong aurophilic interactions, which generated intense phosphorescence even in air at room temperature (quantum yield=16%) in spite of absence of any phosphorescence in solution. This behavior is characteristic for solid-state luminescence referred to as aggregation-controlled emission. Furthermore, the gold(I) complex displays capacity for mechano- and vapo-chromism—that is, the ability to change color reversibly in response to the application of external stimuli. We believe that the proposed design framework, which involves controlling thermal stability and luminescence property separately, provides a new opportunity for the development of practical applications using solid-state luminescent organic molecules.

Gold(I) Complexes Containing Phosphanyl- and Arsanylborane Ligands.

The structural and photophysical properties of a series of new AuI compounds have been studied. The reactions of AuCl(tht) with the phosphanyl- and arsanylboranes RR' EBH2 NMe3 (E=P, As; R=H, Ph; R'=H, Ph, tBu) afford the complexes [AuCl(RR' EBH2 NMe3 )]. In the solid state, [AuCl(H2 PBH2 NMe3 )]2 (2 a) is a dimer showing unsupported intermolecular aurophilic interactions with short Au⋅⋅⋅Au distances. In contrast, [AuCl(H2 AsBH2 NMe3 )]n (2 b) aggregates to form 1D chains. Organic substituents on the pnictogen atoms lead to discrete molecules in [AuCl(RR' PBH2 NMe3 )] (2 c: R=H, R'=tBu; 2 d: R=R'=Ph). To increase the aurophilicity, the ionic homoleptic complexes [Au(RR' EBH2 NMe3 )2 ][AlCl4 ] (3 a-d) have been synthesized, for which 3 a,b form chains in the solid state and exhibit luminescence. The emissions show a drastic redshift with temperature decrease, correlating with decreasing Au⋅⋅⋅Au distances. DFT calculations provide insight into the bonding situation of the products.

A tail like no other

Context. The Rosetta Plasma Consortium (RPC) magnetometer (MAG) data during the tail excursion in March–April 2016 are used to investigate the magnetic structure of and activity in the tail region of the weakly outgassing comet 67P/Churyumov–Gerasimenko (67P). Aims. The goal of this study is to compare the large scale (near) tail structure with that of earlier missions to strong outgassing comets, and the small scale turbulent energy cascade (un)related to the singing comet phenomenon. Methods. The usual methods of space plasma physics are used to analyse the magnetometer data, such as minimum variance analysis, spectral analysis, and power law fitting. Also the cone angle and clock angle of the magnetic field are calculated to interpret the data. Results. It is found that comet 67P does not have a classical draped magnetic field and no bi-lobal tail structure at this late stage of the mission when the comet is already at 2.7 AU distance from the Sun. The main magnetic field direction seems to be more across the tail direction, which may implicate an asymmetric pick-up cloud. During periods of singing comet activity the propagation direction of the waves is at large angles with respect to the magnetic field and to the radial direction towards the comet. Turbulent cascade of magnetic energy from large to small scales is different in the presence of singing as without it.

Formation of Dinuclear AuII and AuI/AuIII Mixed‐Valence Complexes is Directed by Structural Constraints Imposed by Cyclophane‐NHC Ligands

The oxidation of dinuclear AuI complexes containing cyclophane‐bis(NHC) ligands by SOCl2, Br2 and I2 has been investigated. The outcome of the oxidation was dependent on the nature of the cyclophane‐NHC framework. The new complexes were fully characterised by X‐ray diffraction and 1H and 13C NMR spectroscopy. When the AuI complex contained an ortho‐cyclophane framework (dictating short intra‐cation Au···Au distances), oxidation resulted in dinuclear AuII complexes of the form X–AuII(NHC)2–AuII(NHC)2–X (X = Cl, Br, I), the Au···Au distance being in the range 2.6055(3)–2.6501(1) Å. These AuII complexes are strongly luminescent. When the AuI complex contained an meta‐cyclophane framework (dictating longer intra‐cation Au···Au distances), oxidation with SOCl2 or Br2 resulted in dinuclear complexes containing AuI and AuIII centres of the form X–AuIII(NHC)2–X–AuI(NHC)2. NMR studies showed that interconversion of the AuI and AuIII sites within the complexes occurred at rates comparable to the NMR timescale.

A Jupiter-mass planet around the K0 giant HD 208897

For over 10 years, we have carried out a precise radial velocity (RV) survey to find substellar companions around evolved G,K-type stars to extend our knowledge of planet formation and evolution. We performed high precision RV measurements for the giant star HD 208897 using an iodine (I2) absorption cell. The measurements were made at T\"UB\.ITAK National Observatory (TUG, RTT150) and Okayama Astrophysical Observatory (OAO). For the origin of the periodic variation seen in the RV data of the star, we adopted a Keplerian motion caused by an unseen companion. We found that the star hosts a planet with a minimum mass of m2sini=1.40MJ, which is relatively low compared to those of known planets orbiting evolved intermediate-mass stars. The planet is in a nearly circular orbit with a period of P=353 days at about 1 AU distance from the host star. The star is metal rich and located at the early phase of ascent along the red giant branch. The photometric observations of the star at Ankara University Kreiken Observatory (AUKR) and the HIPPARCOS photometry show no sign of variation with periods associated with the RV variation. Neither bisector velocity analysis nor analysis of the Ca II and Halpha lines shows any correlation with the RV measurements.

Gold(I) Alkynyls Supported by Mono- and Bidentate NHC Ligands: Luminescence and Isolation of Unprecedented Ionic Complexes.

Reactions of NHC·HX (NHC = 1-benzyl-3-methylbenzimidazol-2-ylidene, X = Br-, PF6-) and (AuC≡CR)n (R = Ph, C3H6OH) in the presence of Cs2CO3 initially afford compounds of the general formula [(NHC)2Au]2[(RC2)2Au]X, which can be isolated by crystallization. With increased reaction time, only the expected mononuclear complexes of the type [NHCAuC≡CR] are produced. The crystal structure of [(NHC)2Au]2[(PhC2)2Au]PF6 reveals an unprecedented triple-decker array upheld by a remarkably short (2.9375(7) Å) unsupported Au···Au···Au contact. The mononuclear complex [NHCAuC≡CPh] was found to crystallize as three distinct polymorphs and a pseudopolymorph, which depending on the intermolecular Au···Au distances emit blue, green, or yellow light. Two synthetic approaches were employed for the preparation of a series of dinuclear NHC-ligated Au(I) alkynyl complexes of the general formula [NHC-(CH2)n-NHC(AuC≡CR)2], where NHC = N-benzylbenzimidazol-2-ylidene, R = Ph, C3H6OH, C6H10OH, and n = 1-3. In solution, the complexes with aliphatic substituents on the alkynyl fragment are nonemissive, whereas their phenyl-bearing congeners demonstrate characteristic metal-perturbed 3[IL(C≡CPh)] emission. In the solid state, a clear correlation between intermolecular aurophilic interactions and luminescence was established, including their role in the luminescent thermochromism of the phenylalkynyl complexes. The relationship between the Au···Au distance and emission energy was found to be inverse: i.e., the shorter the aurophilic contact, the higher the emission energy. We tentatively attribute this behavior to a smaller extent of excited-state distortion for a structure with a shorter Au···Au separation.

Measuring molecular abundances in comet C/2014 Q2 (Lovejoy) using the APEX telescope.

Comet composition provides critical information on the chemical and physical processes that took place during the formation of the Solar System. We report here on millimeter spectroscopic observations of the long-period bright comet C/2014 Q2 (Lovejoy) using the Atacama Pathfinder Experiment (APEX) band 1 receiver between UT 16.948 to 18.120 January 2015, when the comet was at heliocentric distance of 1.30 au and geocentric distance of 0.53 au. Bright comets allow for sensitive observations of gaseous volatiles that sublimate in their coma. These observations allowed us to detect HCN, CH3OH (multiple transitions), H2CO and CO, and to measure precise molecular production rates. Additionally, sensitive upper limits were derived on the complex molecules acetaldehyde (CH3CHO) and formamide (NH2CHO) based on the average of the strongest lines in the targeted spectral range to improve the signal-to-noise ratio. Gas production rates are derived using a non-LTE molecular excitation calculation involving collisions with H2O and radiative pumping that becomes important in the outer coma due to solar radiation. We find a depletion of CO in C/2014 Q2 (Lovejoy) with a production rate relative to water of 2.0 %, and relatively low abundances of Q(HCN)/Q (H2O),0.1%, and Q (H2CO)/Q (H2O), 0.2 %. In contrast the CH3OH relative abundance Q (CH3OH)/Q (H2O),2.2 %, is close to the mean value observed in other comets. The measured production rates are consistent with values derived for this object from other facilities at similar wavelengths taking into account the difference in the fields of view. Based on the observed mixing ratios of organic molecules in four bright comets including C/2014 Q2, we find some support for atom addition reactions on cold dust being the origin of some of the molecules.

Detection of a new methanol maser line with ALMA

Aims. We aimed at investigating the structure and kinematics of the gaseous disk and outflows around the massive YSO S255 NIRS3 in the S255IR-SMA1 dense clump. Methods. Observations of the S255IR region were carried out with ALMA at two epochs in the compact and extended configurations. Results. We serendipitously detected a new, never predicted, bright maser line at about 349.1 GHz, which most probably represents the CH$_3$OH $14_{1} - 14_{0}$ A$^{- +}$ transition. The emission covers most of the 6.7 GHz methanol maser emission area of almost 1$^{\prime\prime}$ in size and shows a velocity gradient in the same sense as the disk rotation. No variability was found on the time interval of several months. It is classified as Class II maser and probably originates in a ring at a distance of several hundreds AU from the central star.

Probing Conformational Variation in Luminescent Dinuclear Gold(I) N‐Heterocyclic Carbene Complexes

A series of six dinuclear AuI complexes bearing arene‐bridged bidentate imidazolylidene (N‐heterocyclic carbene, NHC) ligands have been synthesized and characterized. The ligand arene linkers (benzene, pyridine, pyrazine) and NHC‐wingtip R‐groups (methyl, benzyl) were modified to investigate the influence of these groups on the preference for two distinct conformational isomeric forms. These two conformations differ in their Au···Au distances; an open form with an Au···Au separation of ca. 7 Å and a twisted conformation with a short Au···Au distance of ca. 3 Å. Five of the complexes were structurally characterized using X‐ray crystallography. Photophysical studies on the complex with a pyridyl linker group and benzyl wingtip groups showed that the twisted conformation resulted in a low‐energy (LE) photoluminescence emission that is associated with the intermolecular aurophilic interaction. In contrast, no room temperature (r.t.) photoluminescence was observed for the open conformation in the solid state, while a high‐energy (HE) emission was observed at 77 K. The pyridyl linked complexes were non‐emissive in solution at room temp., but upon freezing to form a glassy matrix at 77 K, dual HE and LE emissions were observed that closely match the solid‐state spectra for open and twisted complexes, respectively. These observations, in combination with a thorough theoretical investigation, provide important insights into the conformational behavior of complexes of this type. The use of low temperature frozen glasses to trap individual components of conformationally diverse samples for photoluminescence investigations represents a novel approach to study the dynamic and conformational behavior of dinuclear AuI complexes in solution.

Cupriphication of gold to sensitize d10–d10 metal–metal bonds and near-unity phosphorescence quantum yields

Outer-shell s0/p0 orbital mixing with d10 orbitals and symmetry reduction upon cupriphication of cyclic trinuclear trigonal-planar gold(I) complexes are found to sensitize ground-state Cu(I)-Au(I) covalent bonds and near-unity phosphorescence quantum yields. Heterobimetallic Au4Cu2 {[Au4(μ-C2,N3-EtIm)4Cu2(µ-3,5-(CF3)2Pz)2], (4a)}, Au2Cu {[Au2(μ-C2,N3-BzIm)2Cu(µ-3,5-(CF3)2Pz)], (1) and [Au2(μ-C2,N3-MeIm)2Cu(µ-3,5-(CF3)2Pz)], (3a)}, AuCu2 {[Au(μ-C2,N3-MeIm)Cu2(µ-3,5-(CF3)2Pz)2], (3b) and [Au(μ-C2,N3-EtIm)Cu2(µ-3,5-(CF3)2Pz)2], (4b)} and stacked Au3/Cu3 {[Au(μ-C2,N3-BzIm)]3[Cu(µ-3,5-(CF3)2Pz)]3, (2)} form upon reacting Au3 {[Au(μ-C2,N3-(N-R)Im)]3 ((N-R)Im = imidazolate; R = benzyl/methyl/ethyl = BzIm/MeIm/EtIm)} with Cu3 {[Cu(μ-3,5-(CF3)2Pz)]3 (3,5-(CF3)2Pz = 3,5-bis(trifluoromethyl)pyrazolate)}. The crystal structures of 1 and 3a reveal stair-step infinite chains whereby adjacent dimer-of-trimer units are noncovalently packed via two Au(I)⋯Cu(I) metallophilic interactions, whereas 4a exhibits a hexanuclear cluster structure wherein two monomer-of-trimer units are linked by a genuine d10-d10 polar-covalent bond with ligand-unassisted Cu(I)-Au(I) distances of 2.8750(8) Å each-the shortest such an intermolecular distance ever reported between any two d10 centers so as to deem it a "metal-metal bond" vis-à-vis "metallophilic interaction." Density-functional calculations estimate 35-43 kcal/mol binding energy, akin to typical M-M single-bond energies. Congruently, FTIR spectra of 4a show multiple far-IR bands within 65-200 cm-1, assignable to vCu-Au as validated by both the Harvey-Gray method of crystallographic-distance-to-force-constant correlation and dispersive density functional theory computations. Notably, the heterobimetallic complexes herein exhibit photophysical properties that are favorable to those for their homometallic congeners, due to threefold-to-twofold symmetry reduction, resulting in cuprophilic sensitization in extinction coefficient and solid-state photoluminescence quantum yields approaching unity (ΦPL = 0.90-0.97 vs. 0-0.83 for Au3 and Cu3 precursors), which bodes well for potential future utilization in inorganic and/or organic LED applications.

Origin of the wide-orbit circumbinary giant planet HD 106906

Context. A giant planet has been recently resolved at a projected distance of 730 au from the tight pair of young (~13 Myr) intermediate-mass stars HD 106906AB in the Lower Centaurus Crux (LCC) group. The stars are surrounded by a debris disk which displays a ring-like morphology and strong asymmetries at multiple scales. Aims. We aim to study the likelihood of a scenario where the planet formed closer to the stars in the disk, underwent inward disk-induced migration, and got scattered away by the binary star before being stabilized by a close encounter (fly-by). Methods. We performed semi-analytical calculations and numerical simulations (Swift_HJS package) to model the interactions between the planet and the two stars. We accounted for the migration as a simple force. We studied the LCC kinematics to set constraints on the local density of stars, and therefore on the fly-by likelihood. We performed N-body simulations to determine the effects of the planet trajectories (ejection and secular effects) onto the disk morphology. Results. The combination of the migration and mean-motion resonances with the binary star (often 1:6) can eject the planet. Nonetheless, we estimate that the fly-by hypothesis decreases the scenario probability to less than 10-7 for a derived local density of stars of 0.11 stars/pc3. We show that the concomitant effect of the planet and stars trajectories induce spiral-features in the disk which may correspond to the observed asymmetries. Moreover, the present disk shape suggests that the planet is on an eccentric orbit. Conclusions. The scenario we explored is a natural hypothesis if the planet formed within a disk. Conversely, its low probability of occurrence and the fact that HD 106906 b shares some characteristics with other systems in Sco-Cen (e.g., HIP 78530, in terms of mass ratio and separation) may indicate an alternative formation pathway for those objects.