Single-crystal-based excitation wavelength dependent fluorescence of an organometallic complex and applications in anti-counterfeiting and LED

Excitation wavelength dependent emission (EWDE) materials have attracted considerable interest in recent years. Nevertheless, few large-size single crystals with EWDE performance have been reported. In this work, we state a triarylborane (QB) functionalized by di-(2-picolyl)-N-(2-quinolinylmethyl)amine, with a Zn(II) complex (QB-Zn). QB showed polymorphs with different luminescent behavior. Interestingly, the QB-Zn complex exhibited excitation-dependent tri-color fluorescence at room temperature. The single crystals of QB-Zn can switch their luminescent color from blue to green to red as the excitation wavelength change from 330 to 510 to 550 nm. The EWDE mechanism of QB-Zn was investigated in detail by means of photophysical, X-ray single-crystal structural and theoretical calculations studies. The high luminous efficiency and adjustable luminescence switching of QB-Zn crystalline powder and doped hydrogel make them excellent candidates for anti-counterfeiting, optical recording and LED materials.