Octa(μ3-selenido)hexarhenium(III) Complexes Containing Axial Monodentate Diphosphine or Diphosphine-Monoxide Ligands

Abstract

A series of the octahedral hexarhenium(III) complexes containing a variable number of diphosphine (diphos) or diphosphine-monoxide (diphosO) ligands have been prepared by the substitution of the diphosphine Ph2P(CH2)nPPh2 (n = 1 to 5) for the iodide ions in the parent octahedral hexarhenium cluster compound [Re6Se8I6]3-. The diphosphine Ph2P-(CH2)nPPh2 ligands adopt an eta1-bonding mode with the Re6(mu3-Se)8 core, and the P donor atom in the pendant arm is noncoordinated and oxygenated in most cases. The series of new hexarhenium(III) complexes have been well-defined by 1H, 13C, and 31P NMR spectroscopic and FAB-MS data. Four compounds among the series were characterized by X-ray structural determination. Geometrical isomers were identified by NMR spectroscopy as well as by the structural determinations. The apical ligand substitution induces significant change in the redox potentials and the photophysical properties of the Re6(mu3-Se), core. The E1/2 value of the reversible process ReIII6/ReIII5ReIV becomes more positive with the increasing number of the coordinated P donors. The phosphine-substituted hexarhenium(III) derivatives are highly luminescent, with microsecond scale emissive lifetime at ambient temperature, and the fully substituted derivatives with the formula [Re6Se8-(eta1-diphosO)6]2+ display the strongest luminescence with the longest emission lifetimes.

Photoinduced Electron Transfer Reactions of Hexarhenium(III) Cluster: Oxidative Quenching of [Re6S8Cl6]4− Emission by Electron Acceptors

“…We reported previously, on the other hand, that hexarhenium(III) clusters, [Re 6 (l 3 -S) 8 X 6 ] 4-(X = Cl -, Br -, I -, and so forth), showed relatively intense room temperature emission in the visible * near infrared region (600-1,000 nm) with the emission lifetime (s) and quantum yield (U) in acetonitrile being s = 4-11 ls and U = 0.015-0.056, respectively [8] [15], N-heteroaromatics [16][17][18][19][20][21], phosphine derivatives [17,18,22,23], HCOO [24], CH3COO [25], and N 3 [26] [8,29]. Acetonitrile (Wako Pure Chemicals Co. Ltd.) as a medium throughout the study was purified by distillation over CaH 2 .…”

Cellular uptake and cytotoxicity of octahedral rhenium cluster complexes

“…Another interesting aspect of octahedral rhenium cluster complexes is their potential for photodynamic therapy (PDT) which is based on the excitation properties of a photosensitizer by visible or near-infrared light of a specific wavelength [7,8]. Recent studies showed that many octahedral rhenium cluster complexes both in solution [9][10][11][12][13][14][15][16][17][18][19][20][21] and in solid state [16,18,22] display photoluminescence just in the spectra region where PDT is effective. Thus, similar complexes can be considered as a novel class of potential photosensitizers for PDT.…”

Synthesis, crystal structure, and photophysical properties of acid (H3O)2[{W6Br8}Br6] · 4H2O

“…Tens of works presenting the luminescence proper ties of various octahedral molybdenum and rhenium clusters have been published to date [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. However, the photophysical properties of the W 6 clusters are poorly studied.…”

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It is well known that upon UV irradiation many chalcogenide and halide hexanuclear clusters of tran sition metals, for example, [{Re 6 Q 8 }L 6 ] (Q = S, Se) and [{M 6 X 8 }L 6 ] (M = Mo, W; X = Cl, Br), where L are various inorganic and organic ligands, luminesce in the red spectral range with microsecond emission life times [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Phosphorescence in the red spectral range and, as a consequence, the ability to generate singlet oxygen, as well as specific features of the struc tures of similar octahedral clusters of heavy metals, suggest that these compounds are potentially promis ing for the use as photosensitizers in photodynamic therapy and as X ray contrast preparations in diagnos tics of oncological diseases.

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