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.

New bright-red luminescent nitrophenolate complexes (Bu4N)2[{Mo6I8}(OR)6] (R = C6H4-p-(NO2), C6H3-2,4-(NO2)2) have been prepared from (Bu4N)2[{Mo6I8}I6] and AgOR, characterized by X-ray analysis, UV-Vis and IR spectroscopies and ESI-mass spectrometry.

The first examples of samarium, europium, and ytterbium complexes with 3,6-di-tert-butyl-o-benzoquinone(3,6-dbbq) in the form of catecholate have been obtained by reactions of the quinone with the corresponding lanthanocenes, [LnCp2*(thf)n] (n = 1 or 2) in solution. In the course of the reactions lanthanide ions lose one or two Cp* ligands, which take part in reduction of a quinone molecule into a catecholate anion (dbcat, 2(-)). As a result of the reactions, Sm and Yb clearly yield dimeric complexes[(LnCp*)2(dbcat)2], where each Ln ion loses one Cp* ligand. Eu forms a trimeric complex [(EuCp*)-(Eu·thf)2(dbcat)3], in which one Eu ion is coordinated by one Cp* ligand, while two Eu ions have lost all Cp* ligands and are coordinated by THF molecules instead. Magnetic properties corroborate the assignment of oxidation states made on the basis of single-crystal X-ray diffraction: all the quinone ligands are present in the catecholate state; both Sm/Yb ions in the dimers are in the +3 oxidation state, whereas the Eu trimer contains two Eu(II) and one Eu(III) ions. Cyclovoltammetry studies show the presence of two reversible oxidation waves for all complexes, presumably concerned with the redox transitions of the dbcat ligands.

The reactions between (Bu4N)2[{W6I8}I6] (1) and silver carboxylates RCOOAg in CH2Cl2 afforded new luminescent carboxylate complexes (Bu4N)2[{W6I8}(RCOO)6] [R = CH3 (2), C6H5 (3), C2F5 (4), C3F7 (5), C6F5 (6)]. The complexes were characterized by single‐crystal X‐ray diffraction, elemental analysis, cyclic voltammetry, and IR and NMR spectroscopy. Complexes 1–6 all exhibit intense and long‐lived photoluminescence. The carboxylate complexes undergo reversible electrochemical oxidation in two consecutive one‐electron steps.

Photoactive transition metal compounds that are prone to reversible redox reactions are important for myriad applications, including catalysis, optoelectronics, and sensing. This article describes chemical and electrochemical methods to prepare cluster complex (BuN)[{MoI}Cl], a rare example of a 23 e cluster complex within the family of octahedral clusters of Mo, W, and Re. The low temperature and room temperature crystal structures; electronic structure; and the magnetic, optical, and electrochemical properties of this complex are described.

Cluster compounds based on a new {ReMoSe} core were obtained and studied. The polymeric solid K[ReMoSe(CN)(CN)] (1) containing 24 cluster valence electrons (CVE) was isolated as a result of high-temperature reaction. Water-soluble salts K[ReMoSe(CN)]·11HO (2) and Cs[ReMoSe(CN)]·HO (3) were prepared from compound 1. Crystal structures of the diamagnetic compounds 2 and 3 contain a cluster anion [ReMoSe(CN)] with a 22-electronic core {ReMoSe}. Metathesis reaction followed by recrystallization from CHCN yielded paramagnetic salt (PhP)[ReMoSe(CN)]·2CHCN (4) containing the {ReMoSe} core with 21 CVE. Cyclic voltammetry of the solution of 4 displayed three quasi-reversible waves with E = -0.325, -0.818 and -1.410 V vs. Ag/AgCl electrode indicating the presence of [ReMoSe(CN)] transitions. Electronic structure calculations showed that both mer- and fac-isomers of [ReMoSe(CN)] clusters undergo great distortion when the number of CVE decreases.