Matrix Isolation Spectroscopic and Relativistic Quantum Chemical Study of Molecular Platinum Fluorides PtF_n (n=1–6) Reveals Magnetic Bistability of PtF₄

Abstract

Molecular platinum fluorides PtFn, n=1–6, are prepared by two different routes, photo‐initiated fluorine elimination from PtF6 embedded in solid noble‐gas matrices, and the reaction of elemental fluorine with laser‐ablated platinum atoms. IR spectra of the reaction products isolated in rare‐gas matrices under cryogenic conditions provide, for the first time, experimental vibrational frequencies of molecular PtF3, PtF4 and PtF5. Photolysis of PtF6 enabled a highly efficient and almost quantitative formation of molecular PtF4, whereas both PtF5 and PtF3 were formed simultaneously by subsequent UV irradiation of PtF4. The vibrational spectra of these molecular platinum fluorides were assigned with the help of one‐ and two‐component quasirelativistic DFT computation to account for scalar relativistic and spin–orbit coupling effects. Competing Jahn‐Teller and spin–orbit coupling effects result in a magnetic bistability of PtF4, for which a spin‐triplet (3B2g, D2h) coexists with an electronic singlet state (1A1g, D4h) in solid neon matrices.

Investigation of Molecular Iridium Fluorides IrFn (n=1–6): A Combined Matrix‐Isolation and Quantum‐Chemical Study

“…The assignment to this molecule is based on the basis of our experimental observations. For a tetrahedral structure, only a single infrared active absorption would be expected in the Ir−F stretching vibration region, as recently discussed in detail for the analogous PtF 4 molecule [21] . Formation of IrF 5 and IrF 4 is evident after short irradiation of IrF 6 with 278 nm.…”

“…The species IrF n (n = 1-5) were produced for the first time under the cryogenic conditions, and their formation in the laser ablation experiments depends on the noble gas host, similar to the chemistry of platinum fluorides. [21] However, efficient formation of IrF 5 together with minor IrF 3 products was achieved by irradiation into the absorption maxima of IrF 6 in the UV region (λ = 365 nm), while subsequent irradiation (λ = 278 nm) leads to almost quantitative formation of IrF 4 in both neon and argon matrices. Further irradiation into the absorption maxima of IrF 4 (λ = 266 nm) leads to the formation of IrF 6 , IrF 5 , IrF 3 and IrF 2 in neon matrices by addition and elimination of fluorine radicals and/or molecular fluorine.…”

“…For a tetrahedral structure, only a single infrared active absorption would be expected in the IrÀ F stretching vibration region, as recently discussed in detail for the analogous PtF 4 molecule. [21] Formation of IrF 5 and IrF 4 is evident after short irradiation of IrF 6 with 278 nm. However, the efficient formation of IrF 4 and the depletion of the initially generated IrF 5 under prolonged 278 nm irradiation indicate the formation of IrF 4 as photolysis product of IrF 5 instead of as a product of F 2elimination from IrF 6 .…”

“…Alternatively, the binary iridium fluorides were synthesized by the reaction of laser-ablated iridium atoms with fluorine diluted in excess neon and argon under cryo-conditions at 6 K. This method has also been used successfully for the synthesis of other metal fluorides in our group. [15,21] Figure 6 shows spectra obtained after deposition of laser-ablated iridium atoms with 1 % fluorine in solid neon followed by irradiation at different wavelengths. This experiment supported our assignments obtained from the photolysis of IrF 6 : five groups of absorptions were observed, four of which above have been assigned to IrF 5 , IrF 4 , IrF 3 and IrF 2 , whereas an additional band observed at 643.6 cm À 1 was unknown before.…”

“…The technique of matrix-isolation infrared (IR) spectroscopy and laser-ablation apparatus have been described in detail in previous works. [15,21] Matrix samples were prepared by co-deposition of laserablated iridium atoms with 0.5 % and 1 % elemental fluorine diluted in neon (99.999 %, Air Liquide) or argon (99.999 %, Sauerstoffwerk [d] The enthalpies at CCSD(T) level were calculated by adding the enthalpy corrections (B3LYP) to electronic energy changes.…”