Synthesis, characterization, structure and dual room-temperature fluorescent and phosphorescent emission in μ-oxalato-bridged rhenium(I) metallacycle

A new self-assembled dinuclear rhenium(I) tricarbonyl complex, [Re2(CO)6(μ-η4-C2O4)(μ-4,4′-tmdp)] (1) featuring a bis-chelating oxalato dianion (μ-η4-C2O4, H2C2O4 = oxalic acid) connects two fac-Re(CO)3 cores, which are interconnected by a neutral ditopic N-donor clip ligand, that is, 4,4′-trimethylenedipyridine (μ-4,4′-tmdp) has been elegantly synthesized in high yield in a one-step reaction. Compound 1 was characterized by elemental analysis, IR, ESI-MS, TGA and single-crystal X-ray diffraction analyses. The titled complex represents the first dirhenium(I) metallacycle which shows the coexistence of two emissive pathways at room temperature, one populates an emissive 3π–π* state and the other populates a 3MLCT state.