Spectroscopic and Photophysical Properties of Hexanuclear Rhenium(III) Chalcogenide Clusters

Abstract

The electronic, vibrational, and excited-state properties of hexanuclear rhenium(III) chalcogenide clusters based on the [Re(6)(mu(3)-Q)(8)](2+) (Q = S, Se) core have been investigated by spectroscopic and theoretical methods. Ultraviolet or visible excitation of [Re(6)Q(8)](2+) clusters produces luminescence with ranges in maxima of 12 500-15 100 cm(-)(1), emission quantum yields of 1-24%, and emission lifetimes of 2.6-22.4 microseconds. Nonradiative decay rate constants and the luminescence maxima follow the trend predicted by the energy gap law (EGL). Examination of 24 clusters in solution and 14 in the solid phase establish that exocluster ligands engender the observed EGL behavior; clusters with oxygen- or nitrogen-based apical ligands achieve maximal quantum yields and the longest lifetimes. The excited-state decay mechanism was investigated by applying nonradiative decay models to temperature-dependent emission experiments. Solid-state Raman spectra were recorded to identify vibrational contributions to excited-state deactivation; spectral assignments were enabled by normal coordinate analysis afforded from Hartree-Fock and DFT calculations. Excited-state decay is interpreted with a model where normal modes largely centered on the [Re(6)Q(8)](2+) core induce nonradiative relaxation. Hartree-Fock and DFT calculations of the electronic structure of the hexarhenium family of compounds support such a model. These experimental and theoretical studies of [Re(6)Q(8)](2+) luminescence provide a framework for elaborating a variety of luminescence-based applications of the largest series of isoelectronic clusters yet discovered.

Mesolamellar Phases Containing [Re6Q8(CN)6]4– (Q = Te, Se, S) Cluster Anions

“…Recently, others have studied the spectroscopic and photophysical properties of Re 6 Q 8 clusters (Q = S, Se, Te). [17] The compound shows a behavior similar to that of the rhenium cluster itself; a solid sample of compound 2 shows an emission maximum at 742.4 nm with excitation at 463 nm. The emission maximum of 2, at 754.8 nm, is found at 12 nm shorter wavelengths relative to that of K 4 [Re 6 Te 8 -(CN) 6 ].…”

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.…”