Octahedral molybdenum cluster complexes with aromatic sulfonate ligands

Abstract

This article describes the synthesis, structures and systematic study of the spectroscopic and redox properties of a series of octahedral molybdenum metal cluster complexes with aromatic sulfonate ligands (BuN)[{MoX}(OTs)] and (BuN)[{MoX}(PhSO)] (where X is Cl, Br or I; OTs is p-toluenesulfonate and PhSO is benzenesulfonate). All the complexes demonstrated photoluminescence in the red region and an ability to generate singlet oxygen. Notably, the highest quantum yields (>0.6) and narrowest emission bands were found for complexes with a {MoI} cluster core. Moreover, cyclic voltammetric studies revealed that (BuN)[{MoX}(OTs)] and (BuN)[{MoX}(PhSO)] confer enhanced stability towards electrochemical oxidation relative to corresponding starting complexes (BuN)[{MoX}X].

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

“…Our reference compound (TBA) 2 [Mo 6 I 8 (O 3 SC 7 H 7 ) 6 ] shows an emission maximum at λ em,max = 670 nm (1.85 eV) with an FWHM of 0.30 eV. This result is in line with the data reported previously for (TBA) 2 [Mo 6 I 8 (O 3 SC 7 H 7 ) 6 ] . The quenching behavior of microcrystalline (TBA) 2 [Mo 6 I 8 (O 3 SC 7 H 7 ) 6 ] is represented by a decrease of the phosphorescence intensity to 40 % if the surrounding atmosphere is switched from nitrogen to oxygen, and the decay time ( τ ) decreases from 147 µs in pure nitrogen to 64 µs in pure oxygen (Supporting Information).…”

“…The compounds studied herein (shown in the blue frame in Figure ) show increasing decay times of τ = 15, 27, and 133 µs from (TBA) 2 [W 6 I 8 I 6 ] to (TBA) 2 [W 6 I 8 (O 3 SC 7 H 7 ) 6 ] and (TBA) 2 [Mo 6 I 8 (O 3 SC 7 H 7 ) 6 ] in the solid state. This tendency is in line with the luminescence quantum yields; Φ Δ increases from 0.02 (Cl) to 0.15 (Br) and 0.39 (I) for [W 6 X 8 X 6 ] and then to 0.65 for (TBA) 2 [Mo 6 I 8 (O 3 SC 7 H 7 ) 6 ] (in acetonitrile).…”

Complexes of {W6I8}4+ Clusters with Carboxylates: Preparation, Electrochemistry, and Luminescence

“…One of the motivations behind the synthesis of the hexatungsten carboxylate iodide cluster complexes was the extraordinary luminescence properties of {Mo 6 I 8 } 4+ ‐based complexes with terminal carboxylate ligands . The substitution of the terminal iodide ligands in [{Mo 6 I 8 }I 6 ] 2– by various carboxylates as well as by other ligands such as methyl propiolate, aromatic sulfonates, and nitrate leads to a significant narrowing and blueshift of the luminescence along with a large increase in the emission quantum yield ( ϕ em ) and lifetime ( τ em ) , , , , . Therefore, we were keen to ascertain whether the emission characteristics observed for [{Mo 6 I 8 }L 6 ] 2– are maintained for [{W 6 I 8 }L 6 ] 2– .…”

“…Octahedral halide cluster complexes of Mo II and W II , [{M 6 (µ 3 ‐X) 8 }L 6 ] (M = Mo or W; X = Cl, Br or I; L = neutral or anionic ligands), are chemically robust constructions with outstanding photophysical properties; therefore, they are potentially useful for various applications . The most studied are the derivatives of molybdenum chloride and bromide (M = Mo; X = Cl, Br).…”

“…The most studied are the derivatives of molybdenum chloride and bromide (M = Mo; X = Cl, Br). However, the less studied iodide Mo 6 clusters (X = I) stand out owing to their superior emission lifetimes and quantum yields as well as their narrow and blueshifted emission spectra in comparison with those of the other members of the {M 6 X 8 } cluster family with 24 cluster skeleton electrons , , . The tungsten clusters are less studied; in particular, very little is known about the chemistry of [{W 6 (µ 3 ‐I) 8 }L 6 ] clusters.…”