Darstellung und spektroskopische Charakterisierung des Clusteranions [(Mo₆Cl₈ⁱ)(CF₃COO)₆^a]²⁻

Abstract

Bei der Umsetzung von [(Mo6Cl 8i)Cl 6a]2− in Dichlormethan mit Trifluoressigsäure entsteht in der Siedehitze unter Freisetzung von HCl das neue stabile Clusteranion [(Mo6Cl 8i)(CF3COO) 6a]2−. Die zentrale (Mo6Cl8i)‐Gruppe wird bei der Reaktion nicht angegriffen. Bei der 19FNMR‐Messung zeigt ein im Vergleich zum freien CF3COO− tieffeldverschobenes Singulett die Äquivalenz aller Trifluoracetatliganden an, deren einzähnige Koordination am Cluster aus charakteristischen Lagen der IR‐Frequenzen der Carboxylgruppen folgt. Das intensivste Maximum im IR‐Spektrum bei 501 cm−1 wird der antisymmetrischen MoOa‐Valenzschwingung, die stärkste polarisierte Raman‐Linie bei 319 cm−1 als Atmungsschwingung des Cl 8i‐Kubus zugeordnet.

Ligand Influence on the Photophysical Properties and Electronic Structures of Tungsten Iodide Clusters

“…The excitation spectrum recorded for this emission band (monitored at λ = 635 nm) reveals several bands with maxima at λ = 280 (4.43 eV), 335 (3.70 eV), 435 (2.85 eV), and 490 nm (2.53 eV). These emission‐band profiles and the large Stokes shift of 1.27 eV of (TBA) 2 [W 6 I 8 (O 3 SC 7 H 7 ) 6 ] are similar to those reported for (TBA) 2 [W 6 I 8 (CF 3 COO) 6 ] and the corresponding Mo cluster compounds , …”

“…Solution reactions of (TBA) 2 [Mo 6 Cl i 8 Cl a 6 ] (TBA = tetrabutylammonium) revealed that the outer ligands are more loosely bound to the cluster than the inner (face‐capping) ones. As a consequence, they can be exchanged readily in transmetalation reactions with silver salts, as has been shown for (TBA) 2 [Mo 6 Cl 8 (CF 3 COO) 6 ] . More recently, several molybdenum iodide compounds, for example, (TBA) 2 [Mo 6 I 8 (C 3 F 7 COO) 6 ] and (TBA) 2 [Mo 6 I 8 (CF 3 COO) 6 ], were reported to show remarkably enhanced photophysical properties.…”

“…[18a] This solution was layered with n-pentane, and orange crystals ( Figure 3) were obtained and identified as (TBA) 2 [24] and the corresponding Mo cluster compounds. [5,25] The emission spectra recorded for microcrystalline (TBA) 2 [W 6 I 8 (O 3 SC 7 H 7 ) 6 ] as a function of the oxygen partial pressure reveal effective quenching by molecular O 2 , as shown in Figure 6. The peak intensity and integral of the phosphorescence band as well as the decay time decrease with increasing oxygen partial pressure.…”

“…as has been shown for (TBA) 2 [Mo 6 Cl 8 (CF 3 COO) 6 ]. [5] More recently, several molybdenum iodide compounds, for example, (TBA) 2 [Mo 6 I 8 (C 3 F 7 COO) 6 ] [6] and (TBA) 2 [Mo 6 I 8 (CF 3 COO) 6 ], [7] were reported to show remarkably enhanced photophysical properties.…”

“…The electronic structures were analyzed through photoelectron spectroscopy to expose differences in the electronic situations of the compounds.as has been shown for (TBA) 2 [Mo 6 Cl 8 (CF 3 COO) 6 ]. [5] More recently, several molybdenum iodide compounds, for example, (TBA) 2 [Mo 6 I 8 (C 3 F 7 COO) 6 ] [6] and (TBA) 2 [Mo 6 I 8 (CF 3 COO) 6 ], [7] were reported to show remarkably enhanced photophysical properties.The photophysical properties of compounds containing the [M 6 I 8 L 6 ] 2ion (M = Mo, W) are dependent on the nature of the ligands (L). The photoexcitation of the ground state (S) with UV/Vis radiation generates excited states (S n ), and subsequent energy transfer by intersystem crossing (ICS) into triplet states (T n ) then results in broad red phosphorescence.…”