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].

Octahedral metal cluster complexes have high potential for biomedical applications. In order to evaluate the benefits of these moieties for combined CT/X-ray luminescence computed tomography, this paper compares photoluminescence, radiodensity and X-ray induced luminescence properties of eight related octahedral molybdenum and tungsten cluster complexes [{MI}L] (where M is Mo or W and L is I, NO, OTs or OH/HO). This article demonstrates that despite the fact that molybdenum cluster complexes are better photoluminescence emitters, tungsten cluster complexes, in particular (BuN)[{WI}I], demonstrate significantly higher X-ray induced luminescence due to a combination of relatively good photoluminescence properties and high X-ray attenuation. Additionally, photo-degradation of [{MI}(NO)] was evaluated.

This article reports the synthesis, crystal structure of new molybdenum hexaazide cluster complex ( n Bu 4 N) 2 [{Mo 6 I 8 }(N 3 ) 6 ] (3) and comparison of its photophysical and electrochemical properties to those of earlier reported analogues ( n Bu 4 N) 2 [{M 6 X 8 }(N 3 ) 6 ] (X = Cl, Br). Additionally, the dimerisation of 3 as a result of hydrolysis was revealed by mass spectrometry and single crystal X-Ray diffraction. Indeed, the structurally characterised compound ( n Bu 4 N) 4 [({Mo 6 I 8 }(N 3 ) 5 ) 2 O] represents the first example of oxobridged dimer of octahedral molybdenum clusters complexes.