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

• Published in: Chemistry : a European journal 2015-08, Vol.21 (32), p.11495-11508
• Main Authors: Deák, Andrea, Jobbágy, Csaba, Marsi, Gábor, Molnár, Miklós, Szakács, Zoltán, Baranyai, Péter
• Format: Article
• Language: English
• Subjects: Anions; Cations; Chains; Chemistry; Correlation; Crystals; Dimers; Emission; Emissions; Fruits; Gold; hydrogen bonds; Ligands; Luminescence; mechanochromic; Mechanoluminescence; Photoluminescence; Photons; Room temperature; Stimuli; stimuli responsive; X-rays
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201501066

A series of [Au2(nixantphos)2](X)2 (nixantphos=4,6‐bis(diphenylphosphino)‐phenoxazine; X=NO3, 1; CF3COO, 2; CF3SO3, 3; [Au(CN)2], 4; and BF4, 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 [Au2(nixantphos)2]2+ cations with short intramolecular Au⋅⋅⋅Au interactions are involved as donors in an infinite NH⋅⋅⋅X (X=O and N) hydrogen‐bonded chain formation with CF3COO− (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 NH⋅⋅⋅X interactions in the stimuli‐responsive luminescent behavior. Band of gold: A series of [Au2(nixantphos)2](X)2 (X=NO3, CF3COO, CF3SO3, [Au(CN)2], and BF4) complexes was designed and synthesized based on the 4,6‐bis(diphenylphosphino)‐phenoxazine (nixantphos) ligand. The complexes exhibit intriguing anion‐switchable and reversible thermo‐, mechano‐, and vapochromic luminescence changes readily perceivable by the naked eye (see figure).