Luminescent silver() complexes with pyrazole-tetraphenylethene ligands: turn-on fluorescence due to the coordination-driven rigidification and solvent-oriented structural transformation

A new tetrapyrazole-modified tetraphenylethene (TPE) ligand L was designed and found to display "turn-on" fluorescence when it combines with Ag + ions in dilute solution by restricting intramolecular rotation of TPE. A series of Ag complexes 1-7 were obtained, and they exhibit excellent fluorescence properties in the solid state. Compared with PF 6 − , the silver complex with the CF 3 SO 3 − anion can further enhance its fluorescence due to the transformation of its structure from Ag 2 L ( 2 ) to Ag 4 L 2 ( 3 ). As zero-dimensional complexes, 1 and 3 have excellent piezochromic properties with a color change from blue to green. Furthermore, structural changes of 1 and 3 to the corresponding three-dimensional frameworks 4 and 5 occur upon immersing in ethanol. In addition, 1 can act as a potential fluorescent probe for sensing nitrile compounds. A series of Ag complexes 1-7 with pyrazole-tetraphenylethene ligands were fabricated and their fluorescence and sensing properties were examined.