Vapochromic Gold(I)-Silver(I) Cluster Protected by Alkynyl and Phosphine Ligands

Intensely luminescent coinage metal cluster [Au12Ag14(CCPh)(20)(mdppz)(4)(CH3OH)(8)](BF4)(6) {1, mdppz = 2-(3-methylpyrazinyl)diphenylphosphine} was synthesized and structurally characterized. Twenty alkynyl ligands (PhCC-), four mdppz ligands, and eight methanol molecules were found to co-stabilize the metal cluster. Interestingly, when the weakly ligated methanol molecules were removed, the green luminescence of 1 significantly redshifted to yellow; exposing the resulting yellow sample in methanol vapor immediately restores the green luminescence. Thus reversible luminescence response can be observed by removing and restoring methanol. Other small solvent molecules with weak coordination ability such as Me2CO, MeCN, and C2H5OH were also found to be good agents to trigger the vapochromism.