Alkyl‐Spacer Enhancement in Performance of Light‐Emitting Electrochemical Cells

Synthetic, structural, photophysical, and electrochemical study of [Ir(ppy) 2 (py) 2 ](BF 4 ) ( 1 (BF 4 )) and four di‐N–N‐bridged complexes of [Ir(ppy) 2 (bpa)] 2 (BF 4 ) 2 ( 2A (BF 4 ) 2 ), [Ir(ppy) 2 (( cis ‐bpe))] 2 (BF 4 ) 2 ( 2B (BF 4 ) 2 ), [Ir(ppy) 2 (tmp)] 2 (BF 4 ) 2 ( 2C (BF 4 ) 2 ), and [Ir(ppy) 2 (bpy)] 4 (BF 4 ) 4 ( 3 (BF 4 ) 4 ) are described with Hppy = 2‐phenylpyridine, py = pyridine, N– N = dipyridyl ligands of 1,2‐bis(4‐pyridyl)ethane (bpa), cis ‐1,2‐bis(4‐pyridyl)ethylene ( cis ‐bpe), 1,3‐di(4‐pyridyl)propane (tmp), and 4,4'‐dipyridine (bpy). Five single‐crystal structures of 1 (PF 6 ), 2A (NO 3 ) 2 , 2A (PF 6 ) 2 , 2B (PF 6 ) 2 , and 3 (NO 3 ) 4 were determined, supporting the dibridged structures and presence of a variety of stereoisomers. Application of four luminescent complexes, 1 (BF 4 ), 2A (BF 4 ) 2 , 2C (BF 4 ) 2 , and 3 (BF 4 ) 4 , in solid‐state light‐emitting electrochemical cells (LECs) is reported. The work demonstrates an effective approach to realize efficient LECs based on dibridged di‐ and multinuclear cationic transition‐metal complexes with a suitably long alkyl spacer in the bridging ligand.