Enantiomerically pure lanthanide-organic polytungstates exhibiting two-photon absorption properties

Two enantiomerically pure polytungstates, Na2[(CH3)2NH2]3{Na⊂[Ce(III)(H2O)(CH3CH2OH)(L-tartH3)(H2Si2W19O66)]}·3.5H2O (L-1) and [(CH3)2NH2]7{Na⊂[Ce(III)(H2O)(CH3CH2OH)(D-tartH3)(Si2W19O66)]}·2.5H2O (D-1), were successfully synthesized. Structural analysis indicates that chiral tartrate ligands directly connect with novel lacunary [Si2W19O66](10-) polytungstate units. Strong induced optical activity in the polyoxometalate (POM) units is manifested by circular dichroism spectroscopy. Z-scan analysis revealed that L-1 and D-1 are the first chiral POM-based complexes that exhibit two-photon absorption properties typical of the third-order nonlinear optical response.