Electronic Communication in Luminescent Dicyanorhenate-Bridged Homotrinuclear Rhenium(I) Complexes

Abstract

A series of cyano-bridged homotrinuclear Re(I) complexes with the general formula of {diphosphine, or two carbonyl ligands; X = triphenylphosphine or carbonyl ligand} and the corresponding mononuclear complex analogues were synthesized. The structures of most of the trinuclear Re(I) complexes have been determined by X-ray crystallography. The relative orientations of peripheral to central Re(I) units in these structures vary considerably. The photophysical properties of these trinuclear Re(I) complexes have been examined. Except for the trinuclear Re(I) complex with Br 2 phen ligand, all the other triads display orange to red photoluminescence derived from the 3 MLCT [dπ(Re) → π*(phen)] origin of the central Re(I) unit, suggestive of efficient energy transfer between the peripheral chromophores and the central unit. In addition to the efficient energy transfer processes between the Re(I) chromophores in these trinuclear complexes, the ability of the [NC−Re−CN] bridging ligands for electronic coupling between the rhenium metal centers is evidenced by ca. 0.2−0.3 V separation of the two rhenium metal-based oxidation potentials of the chemically equivalent peripheral units.

Excited‐State Dynamics of Phosphorescent Trinuclear Re(I) Complexes

“…As described in our previous report, [7] these complexes show intense intraligand ππ* transitions in the UV region and MLCT [dπ(Re)→π*(N−N)] transitions in the visible region (Figure 3). As the MLCT transitions of the peripheral and central chromophores in the trinuclear complexes are close in energy, these transitions overlap and become a broad absorption band.…”

Study of Re(I) Carbene Complexes for Photocatalytic Reduction of Carbon Dioxide

“…As with related dicarbonyl Re­(I) bipyridine complexes, ,− complexes 2 – 6 show intense ligand-centered ππ* transitions in the UV region and MLCT [Re­(dπ) → π*­(bpy)] transitions in the visible region with tailing down to 550 nm (Figure and Table S1 of the Supporting Information). In comparison to complex 1 and other tricarbonyl Re­(I) bipyridyl complexes, − their MLCT transitions are red-shifted because the replacement of carbonyl with a weaker π-accepting ligand, such as isocyanide or phosphine, in these complexes would lead to destabilization of the dπ­(Re) orbital and, thus, a narrower MLCT energy gap .…”

Aerobically stable and substitutionally labile α-diimine rhenium dicarbonyl complexes

“…In the last decade the groups of Ko and Ishitani have introduced tunable isocyano and acetonitrile rhenium(I) diimine luminophores of general formula cis,cis-[Re(CO) 2 (N_N)(CNR) 2 ] + and cis,cis-and cis-trans-[Re(CO) 2 (-L 0/00 ) 2 (N_N)] + (with L 0 ¼ CH 3 CN and L 00 ¼ CH 3 CN, py, PR 3 or halide). 7,[20][21][22][23][24][25] Complexes are prepared by photo-substitutions/ decarbonylation of fac-[Re(CO) 3 (CNR) 2 Br] in the presence of diimine ligands (N_N) with broadband or UV excitation. N_N isonitrile analogues of the Kromer complexes were similarly obtained by photolytic decarbonylation of fac-[Re(CO) 3 (-N_N)(CNR)] + in the presence of CNR.…”