Diimine ligand structure effects on photophysical properties of tricarbonyl rhenium(I) complexes having arylborane charge transfer units

Remarkably Intense Emission from Ruthenium(II) Complexes with Multiple Borane Centers

“…We have focused on triarylboranes as a choice for synthetic modulation of the spectroscopic and photophysical properties of transition metal complexes. , Owing to the presence of the vacant p-orbital on the boron atom (p­(B)) in a triarylborane, a class of transition metal complexes having a triarylborane group(s) in the periphery of the ligand(s) shows fascinating excited-state properties, characterized by the synergistic interactions between MLCT in a transition metal complex and the intramolecular CT interaction between the π-orbital of the aryl group (π­(aryl)) and p­(B) (π­(aryl)–p­(B) CT) in the triarylborane group. As a typical example, we reported that the [Ru­(phen) 3 ] 2+ (phen = 1,10-phenanthroline) derivative having a (dimesityl)­boryldurylethynyl (DBDE) group at the 4- or 5-position of one of the three phen ligands showed intense MLCT absorption/emission and a long-lived excited state compared with [Ru­(phen) 3 ] 2+ : 4BRu 2+ ([Ru­(4-DBDE-phen)­(phen) 2 ] 2+ ), ε 473 (molar absorption coefficient at 473 nm) = 2.6 × 10 4 M –1 cm –1 (M = mol/dm 3 ), Φ em = 0.11, and τ em (emission lifetime) = 12 μs; 5BRu 2+ ([Ru­(5-DBDE-phen) (phen) 2 ] 2+ ), ε 448 = 1.7 × 10 4 M –1 cm –1 , Φ em = 0.11, and τ em = 1.2 μs; [Ru­(phen) 3 ] 2+ , ε 445 = 1.7 × 10 4 M –1 cm –1 , Φ em = 0.045, and τ em = 0.42 μs in CH 3 CN at 298 K .…”

Bright and Long‐Lived Emission from a Starburst‐Type Arylborane‐Appended Polypyridyl Ruthenium(II) Complex

“…As the nonradiative decay of 3 MLCT* occurs through the 3 dd* state, the τ em value of a Ru II complex in general decreases as the temperature ( T ) increases. In contrast, the emission lifetime of 1 is almost independent of T (see Figure ), similarly to those of 2 and other DBDE‐appended polypyridyl Ru II and Re I complexes , . Surprisingly, the τ em value of 1 remains very long even at 400 K ( τ em = 6.6 µs).…”

Emission Tuning of Heteroleptic Arylborane–Ruthenium(II) Complexes by Ancillary Ligands: Observation of Strickler–Berg-Type Relation

“…We have focused on chemical decorations of an MLCT-type transition metal complex by a triarylborane unit(s). − Several research groups have also reported characteristic spectroscopic and photophysical properties of aryiborane-decorated platinum­(II), − iridium­(III), − ruthenium­(II), , zinc­(II), , copper­(I), , rhenium­(I), , and gold­(I) complexes . In the transition metal complex possessing a triarylborane-appended ligand(s), the intramolecular CT transition from the π-orbital of the aryl group (π­(aryl)) to the vacant p-orbital on the boron atom (p­(B)), π­(aryl)–p­(B) CT, in the triarylborane moiety synergistically participates in the MLCT transition in the metal-complex moiety, and as a result, the complex shows intriguing spectroscopic and excited-state properties. − We recently reported the characteristic emission properties of a homoleptic arylborane–ruthenium­(II) complex ([Ru­(B 2 bpy) 3 ] 2+ ), in which six (dimesityl)­boryldurylethynyl (DBDE) groups were introduced to [Ru­(bpy) 3 ] 2+ (bpy = 2,2′-bipyridine) at the 4- and 4′-positions of the three bpy ligands: B 2 bpy = 4,4′-(DBDE) 2 -2,2′-bipyridine . In CH 3 CN at 298 K, [Ru­(B 2 bpy) 3 ] 2+ shows extremely intense and long-lived emission (Φ em = 0.43 and τ em = 1.7 μs).…”