Controlling the White-Light Generation of [(RSn)₄ E₆ ]: Effects of Substituent and Chalcogenide Variation

Adamantane-type organotin chalcogenide clusters of the general composition [(RT)₄ S₆ ] (R=aromatic substituent, T=Si, Ge, Sn) have extreme non-linear optical properties that lead to highly directional white-light generation (WLG) upon irradiation with an IR laser diode. However, the mechanism is not yet understood. Now, a series of compounds [(RSn)₄ E₆ ] (R=phenyl, cyclopentadienyl, cyclohexyl, benzyl, CH₂ CH₂ (C₆ H₄ )CO₂ Et; E=S, Se), were prepared, characterized, and investigated for their nonlinear optical properties. With the exception of crystalline [(BnSn)₄ S₆ ], all these compounds exhibit WLG with similar emission spectra; slight blue-shifts are observed by introduction of cyclopentadienyl substituents, while the introduction of Se in the inorganic core can provoke a red-shift. These investigations disprove the initial assumption of an aromatic substituent being a necessary precondition; the precondition seems to be the presence of (cyclic) substituents providing enough electron density.