Neutral heteroleptic rhenium-based M3L3L′ type metallacycles: Synthesis, structural characterization and DFT/TDDFT studies

Three new M3L3L′-type metallacycles (2–4) based of fac-Re(CO)3 core (M), three rigid anionic ditopic bridging ligands (L = imidazolate for 2; benzimidazolate for 3; benzotriazolate for 4), and flexible tripodal N-donors (L′ = 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene for 2 and 3; 1,3,5-tris(benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene for 4) have been synthesized and structurally characterized by elemental analysis, FT-IR, and 1H NMR spectroscopy. The structure of metallacycle 4 was confirmed by single crystal X-ray diffraction analysis. The crystal structure of 1·DMSO (1 = M3L3L′; L = benzimidazolate, and L′ = 1,3,5-tris(benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene) was discussed. The absorption and emission properties of complexes have been investigated and were assigned using time-dependent density functional theory calculations.