Probing the Structural Origins of Vapochromism of a Triarylboron-Functionalized Platinum(II) Acetylide by Optical and Multinuclear Solid-State NMR Spectroscopy

A vapoluminescent triarylboron-functionalized platinum(II) complex that displays a mechanism of vapochromism differing from all previously reported platinum(II) compounds has been synthesized. The luminescence color of 1 switches in response to many volatile organic compounds in the solid state, including hexanes, CH2Cl2, benzene, and methanol. While vapochromism due to changes in Pt−Pt or π−π stacking interactions has been commonly observed, absorption and luminescence studies and single-crystal and powder X-ray diffraction data as well as multinuclear solid-state NMR experiments (195Pt, 13C, 11B, 2H, and 1H) revealed that the vapochromic response of 1 is instead due to changes in the excited-state energy levels resulting from local interactions of solvent molecules with the complex. Furthermore, these interactions result in inversion of the lowest-energy excited states of the complex in some cases, the first observation of this phenomenon in the solid state.