Anion‐, Solvent‐, Temperature‐, and Mechano‐Responsive Photoluminescence in Gold(I) Diphosphine‐Based Dimers

A series of [Au 2 (nixantphos) 2 ](X) 2 (nixantphos=4,6‐bis(diphenylphosphino)‐phenoxazine; X=NO 3 , 1 ; CF 3 COO, 2 ; CF 3 SO 3 , 3 ; [Au(CN) 2 ], 4 ; and BF 4 , 5 ) complexes that exhibit intriguing anion‐switchable and stimuli‐responsive luminescent photophysical properties have been synthesized and characterized. Depending on their anions, these complexes display yellow ( 3 ), orange ( 4 and 5 ), and red ( 1 and 2 ) emission colors. They exhibit reversible thermo‐, mechano‐, and vapochromic luminescence changes readily perceivable by the naked eye. Single‐crystal X‐ray studies show that the [Au 2 (nixantphos) 2 ] 2+ cations with short intramolecular Au ⋅⋅⋅ Au interactions are involved as donors in an infinite NH ⋅⋅⋅ X (X=O and N) hydrogen‐bonded chain formation with CF 3 COO − ( 2 C ) and aurophilically linked [Au(CN) 2 ] − counterions ( 4 C ). Both crystals show thermochromic luminescence; their room temperature red ( 2 C ) and orange ( 4 C ) emission turns into yellow upon cooling to 77 K. They also exhibit reversible mechanochromic luminescence by changing their emission color from red to dark ( 2 C ), and orange to red ( 4 C ). Compounds 1 – 5 also display reversible mechanochromic luminescence, altering their emission colors between orange ( 1 ) or red ( 2 ) to dark, as well as between yellow ( 3 ) or orange ( 4 and 5 ) to red. Detailed photophysical investigations and correlation with solid‐state structural data established the significant role of NH ⋅⋅⋅ X interactions in the stimuli‐responsive luminescent behavior.