A combined quantum-chemical and matrix-isolation study on molecular manganese fluorides

Molecular manganese fluorides were studied using quantum-chemical calculations at DFT and CCSD(T) levels and experimentally by matrix-isolation techniques. They were prepared by co-deposition of IR-laser ablated elemental manganese or manganese trifluoride with F2 in an excess of Ne, Ar, or N2 or with neat F2 at 5–12 K. New IR bands in the Mn–F stretching region are detected and assigned to matrix-isolated molecular MnFx (x = 1–3)

A matrix isolation and computational study of molecular palladium fluorides : does PdF₆ exist?

Palladium atoms generated by thermal evaporation and laser ablation were reacted with and trapped in F₂ /Ar, F₂ /Ne, and neat F₂ matrices. The products were characterized by electronic absorption and infrared spectroscopy, together with relativistic density functional theory calculations as well as coupled cluster calculations. Vibrational modes at 540 and 617 cm⁻¹ in argon matrices were assigned to molecular PdF and PdF₂ , and a band at 692 cm⁻¹ was assigned to molecular PdF₄ . A band at 624 cm⁻¹ can be assigned to either PdF₃ or PdF₆, with the former preferred from experimental considerations. Although calculations might support the latter assignment, our conclusion is that in these detailed experiments there is no convincing evidence for PdF₆

Matrix-isolation as well as IR-spectroscopic and quantum-chemical investigation of molecular fluorides prepared from IR-laser ablated manganese, palladium, copper, silver, gold and elemental fluorine

Molekulare Fluoride von Pd, Cu, Ag, Au und Mn wurden in festem Ne, Ar, N2 oder reinen Fluormatrizen isoliert und IR-spektroskopisch sowie quantenchemisch auf dem DFT- und CCSD(T)-Niveau untersucht. Sie wurden durch IR-Laserablation der Metalle bzw. von MnF3 und anschließender Co-Kondensation mit in Ne, Ar oder N2 verdünntem oder reinem F2 bei 5 – 12 K hergestellt. Beim Einsatz von metallischem Mn oder kristallinem MnF3 wurden neue Banden im Bereich der Mn-F-Streckschwingungen beobachtet und molekularen Manganfluoriden MnFx (x = 1 – 3) zugeordnet. Im Falle von Palladium wurden in festem Ar IR-Banden bei 540 und 617 cm-1 molekularem PdF und PdF2 und eine Bande bei 692 cm-1 molekularem PdF4 zugeordnet. Eine weitere Bande bei 624 cm−1 wurde schließlich PdF3 zugeordnet, wobei quantenchemischen Rechnungen zufolge eine Zuordnung dieser Bande zu molekularem PdF6 nicht ausgeschlossen werden kann. Die Reaktionen von IR-laserverdampften Münzmetallen (M = Au, Ag, Cu) mit F2 in überschüssigem Ar und Ne lieferten neue Absorptionen im Bereich der M-F-Streckschwingungen. Für Gold wurde die Bildung von Ng-AuF (Ng = Ne, Ar) in Ne, Ar und 1% Ar in Ne nachgewiesen. Die Ng-MF-Komplexe mit Ag (Ng = Ar, Ne) und Cu (Ng = Ar) mit schwächeren Ng-M-Bindungen als die in Ng-AuF wurden auch beobachtet. Zusätzlich wurden molekulares MF2 und MF3 über die Isotopenaufspaltung ihrer M-F-Streckschwingung (M = Ag, Cu), einen Vergleich der Schwingungsfrequenzen der drei Metallfluoride und gestützt durch quantenchemische Rechnungen nachgewiesen. Molekulares AuF5 wurde anhand der stärksten Schwingungsbande und theoretischer Frequenzrechnungen identifiziert. Die Verwendung von reinem Fluor als Matrixgas und die Bildung von Polyfluoridmonoanionen [Fn]− (n = 3, 5) unter Tieftemperaturbedingungen wird geschildert. Reinigungsverfahren und spektroskopische Daten von Fluor werden beschrieben und die Matrix-Shifts ausgewählter Moleküle und Verunreinigungen in festem Fluor mit denen in gebräuchlichen Matrixgasen (Ne, Ar, Kr, N2) verglichen. Die Reaktion von unverdünntem Fluor mit IR-laserverdampften Metallatomen zur Bildung von Fluoriden der Edelmetalle Palladium (PdF2) und Gold (AuF5) wurde untersucht. Die Fluoride wurden IR-spektroskopisch in festem Fluor bei 5 K charakterisiert. Die Bildung des [F5]−-Anions bei der Laserablation von Metallen in Gegenwart von F2 wurde in dieser Arbeit durch IR-Laserablation von Platin mit 3% F2 in Ne nachgewiesen und erstmals über zwei charakteristische Schwingungsbanden bei 850,7 und 1805,0 cm−1 in einer Ne-Matrix bei 5 K und sein Photolyseverhalten charakterisiert.Molecular transition metal fluorides of manganese, palladium, copper, silver and gold were studied using matrix-isolation techniques, IR-spectroscopy and quantum-chemical calculations at DFT and CCSD(T) levels. They were prepared by co-deposition of the IR-laser ablated elemental metals with F2 in an excess of Ne, Ar, or N2 or with neat F2 at 5 – 12 K. Laser ablation of metallic manganese or crystalline manganese trifluoride provided new IR bands in the Mn F stretching region, which were assigned to matrix-isolated molecular MnFx (x = 1 – 3) species. In case of palladium vibrational modes at 540 and 617 cm-1 in argon matrices have been assigned to molecular PdF and PdF2 and a band at 692 cm-1 has been assigned to molecular PdF4. A further band appeared at 624 cm−1, which is finally assigned to PdF3, although, based on calculations, we cannot exclude the formation of molecular PdF6 instead. The reactions of laser-ablated noble metal (M = Au, Ag, Cu) atoms with F2 in excess of argon or neon gave new absorptions in the M-F stretching region. For gold, the formation of Ng-AuF was proved in Ne, Ar and 1% Ar in Ne. The Ng-MF complexes with M = Ag (Ng = Ar, Ne) and Cu (Ng = Ar) were also detected, however, these Ng-M bonds are much weaker than those of Ng-AuF. In addition, molecular MF2 and MF3 were identified from the isotopic splitting of M-F stretching bands (M = Ag, Cu) and by comparison of the frequencies of the three metal fluorides as well as theoretical frequency calculations. The AuF5 molecule was characterized by its strongest stretching mode and theoretical frequency calculations. The formation of molecular Au2F6 was also observed. The use of neat fluorine in matrix-isolation is reported, as well as the formation of polyfluoride monoanions [Fn]− (n = 3, 5) at cryogenic conditions. Purification procedures and spectroscopic data of fluorine are described, and matrix shifts of selected molecules and impurities in solid fluorine are compared to those of common matrix gases (Ar, Kr, N2, Ne). The reaction of neat fluorine and IR- laser ablated metal atoms to yield fluorides of palladium (PdF2) and gold (AuF5) has been investigated. The fluorides have been characterized in solid fluorine by IR spectroscopy at 5 K. The formation of the [F5]− anion by IR- laser ablation of metals in the presence of fluorine has been verified in this work by IR-laser ablation of platinum in the presence of fluorine and for the first time proved by two characteristic vibrational bands at 850.7 and 1805.0 cm−1 in a Ne matrix at 5 K and by its photo-behavior

New Evidence in an Old Case: The Question of Chromium Hexafluoride Reinvestigated

The question of whether or not the chromium hexafluoride molecule has been synthesized and characterized has been widely discussed in the literature and cannot, in spite of many efforts, yet be answered beyond doubt. New matrix-isolation experiments can now show, together with state-of-the-art quantum-chemical calculations, that the compound previously isolated in inert gas matrixes, was CrF₅ and not CrF₆. New bands in the matrix IR spectra can be assigned to the Cr₂F₁₀ dimer, and furthermore evidence was found in the spectra for a photodissociation or reversible excitation of CrF₅ under UV irradiation. However, even if CrF₆ is not stable at ambient conditions, its formation under high fluorine pressures in autoclave reactions cannot be excluded completely

A Matrix Isolation and Computational Study of Molecular Palladium Fluorides: Does PdF₆ Exist?

Palladium atoms generated by thermal evaporation and laser ablation were reacted with and trapped in F₂/Ar, F₂/Ne, and neat F₂ matrices. The products were characterized by electronic absorption and infrared spectroscopy, together with relativistic density functional theory calculations as well as coupled cluster calculations. Vibrational modes at 540 and 617 cm^–1 in argon matrices were assigned to molecular PdF and PdF₂, and a band at 692 cm^–1 was assigned to molecular PdF₄. A band at 624 cm^–1 can be assigned to either PdF₃ or PdF₆, with the former preferred from experimental considerations. Although calculations might support the latter assignment, our conclusion is that in these detailed experiments there is no convincing evidence for PdF₆

FragSAD : A database of diversity and species abundance distributions from habitat fragments

Habitat destruction is the single greatest anthropogenic threat to biodiversity. Decades of research on this issue have led to the accumulation of hundreds of data sets comparing species assemblages in larger, intact, habitats to smaller, more fragmented, habitats. Despite this, little synthesis or consensus has been achieved, primarily because of non-standardized sampling methodology and analyses of notoriously scale-dependent response variables (i.e., species richness). To be able to compare and contrast the results of habitat fragmentation on species' assemblages, it is necessary to have the underlying data on species abundances and sampling intensity, so that standardization can be achieved. To accomplish this, we systematically searched the literature for studies where abundances of species in assemblages (of any taxa) were sampled from many habitat patches that varied in size. From these, we extracted data from several studies, and contacted authors of studies where appropriate data were collected but not published, giving us 117 studies that compared species assemblages among habitat fragments that varied in area. Less than one-half (41) of studies came from tropical forests of Central and South America, but there were many studies from temperate forests and grasslands from all continents except Antarctica. Fifty-four of the studies were on invertebrates (mostly insects), but there were several studies on plants (15), birds (16), mammals (19), and reptiles and amphibians (13). We also collected qualitative information on the length of time since fragmentation. With data on total and relative abundances (and identities) of species, sampling effort, and affiliated meta-data about the study sites, these data can be used to more definitively test hypotheses about the role of habitat fragmentation in altering patterns of biodiversity. There are no copyright restrictions. Please cite this data paper and the associated Dryad data set if the data are used in publications.Peer reviewe