A ligand substituted tungsten iodide cluster: luminescence vs. singlet oxygen production

Abstract

Octahedral tungsten iodide clusters equipped with apical ligands (L) are synthesized to implement substantial photophysical properties. The [WI(CFCOO)] cluster reported herein is the first example of a family of ligand substituted [WIL] clusters. Such compounds are expected to exhibit a rich photochemistry in which the apical ligands play a crucial role. The versatile solid state and solution phase photophysical properties of (TBA)[WI(CFCOO)] described herein parallel characteristics obtained in some photophysically active organic compounds, including a broad absorption in the UV/VIS region. Upon irradiation of this compound, a broad red emission is observed in the VIS/NIR region resulting from excited triplet states, and singlet oxygen (aΔ) is generated in the presence of O.

Time-gated luminescence bioimaging with new luminescent nanocolloids based on [Mo6I8(C2F5COO)6]2−metal atom clusters

“…This behavior is explained by the excitation of triplet oxygen from excited triplet states of the cluster to form singlet oxygen. 50 This point was also demonstrated with Mo6 or Re6 clusters by using bubbling O2 and/or Ar atmosphere. [31][32][33] As we can see on Figure 3, this quenching effect was successfully limited by embedding the cluster units in silica nanoparticles, and a clear red luminescence could be observed with eyes under UV irradiation at 365 nm.…”

“…45 In the case of Cs2Mo6I14 clusters, to explain the maximum centered at 657 nm, we have to consider that iodide apical ligands could be exchanged by OH groups in aqueous solution during the microemulsion process due to the HSAB principle. 50 Indeed, the difference between photo-luminescence properties of Cs2Mo6I i 8I a 6 solid state compound and those of Cs2Mo6Ii8I a 6@SiO2 is due to the substitution of apical iodides by OH groups that influence the nature of excited states and consequently the de-excitation pathways. This classically induces a shift of emission maxima.…”

Preparation and Luminescence of Cluster Compounds [W6Br8L6]2– with L = CF3COO and C7H7SO3

“…[25,34] A comparison of our results on bromides with the corresponding iodides reveals blue shifted emission wavelengths (λ em,max ) of the respective iodide compounds by 75 and 52 nm.…”

“…We note herein, that the generation of singlet oxygen has been evidenced for (TBA) 2 6 ] in solid state and in solution. [25,33] The reason for the different quenching behavior of cluster compounds is influenced by several factors, which are subject of our current research.…”

“…Exchange reactions of cations (Cs + for nBu 4 N + ) and the six apical ligands (Br -for CF 3 COO -and C 7 H 7 SO 3 -) are routine procedures that have been described elsewhere. [19][20][21][25][26] Hence, the reaction was carried out following standard procedures (see Experimental Section) until products were recrystallized from pentane/DCM to yield yellow crystalline powders containing single crystals. Single crystals were selected for an X-ray diffraction measurement with a Bruker APEX II CCD and a Bruker APEX diffractometer equipped with Mo-K α radiation (λ = 0.71073 Å) and a graphite monochromator.…”