Tunable third-order nonlinear optical effect via modifying Ti4(embonate)6 cage-based ionic pairs

Abstract

Benefiting from the strong inherent π-conjugation properties, the integration of Ti₄L₆ (L = embonate) cages and various N,N-chelated transition-metal cations into tightly packed structures accurately leads to high-performance materials with adjustable nonlinear optical (NLO) effects. These cage-based ionic pairs possess different supramolecular packing structures, including a π⋯π stacked porous framework where the Ti₄L₆ cages are tactically located at the channels. Interestingly, by introducing the large π-conjugated 1,10-phenanthroline type ligands and adjusting the aromatic ring electron cloud density, we have effectively regulated their third-order NLO properties, realizing nonlinear absorption responses from reverse saturated absorption (RSA) to saturated absorption (SA). This work not only presents an extraordinary coordination cage-based assembly, but also provides new insights into the function of cage materials.