Tuning third-order nonlinear optical response of heterometallic alkyltin-oxo clusters through intermolecular interactions

Two isomorphic titanium-doped organotin-oxo aromatic aldoxime clusters, SnTi-1 and SnTi-2, have been successfully synthesized via a solvothermal method. Both clusters have an identical undecameric core, consisting of a pentagonal wheel-shaped moiety {Ti5} and two alkylate trimers {Sn3} fused together, and decorated with unsubstituted and methoxy-substituted aldoxime ligands, respectively. They exhibit excellent solubility, chemical stability, and hydrophobicity owing to the existence of peripheral protective shells of alkyl and aromatic groups. The steric hindrance effect of methoxy induces a rearrangement of clusters, altering weak interactions from C–H···π to π···π between cluster molecules, and ultimately modulating the third-order nonlinear optical from saturation absorption to reverse saturation absorption.