Shiqing Wang

First NIR luminescent polymeric high-nuclearity Cd–Ln nanoclusters from a long-chain Schiff base ligand

Two classes of Cd–Ln nanoclusters [Ln6Cd22Cl14(OH)2L10(OAc)26]n (Ln = La (1) and Nd (2)), and [Yb6Cd18Cl6(OH)2L9(OAc)28] (3) were prepared using a long-chain Schiff base ligand. 1 and 2 exhibit unusual 1-D coordination polymeric structures built by 28-metal drum-like units, while 3 has a 0-D 24-metal nano-drum-like architecture. Their NIR luminescence properties were investigated.

Anion dependent self-assembly of drum-like 30- and 32-metal Cd–Ln nanoclusters: visible and NIR luminescent sensing of metal cations

Two types of drum-like 30- and 32-metal Cd–Ln nanoclusters [Ln8Cd24L12(OAc)48] (Ln = Sm (1), Yb (2), Er (3)) and [Er8Cd22L12(OAc)38(OH)6] (4) were constructed using a designed Schiff base ligand built around a flexible (CH2)7 chain. Hydroxide (OH−) anions are found in the structure of 4, indicating that the basic environment favors the formation of the 30-metal cluster. The chromogenic Cd/L components in these clusters can act as efficient sensitizers for lanthanide luminescence. With the Ln(III) centers enclosed within the drum-like structures, 1–4 display the typical emission spectra of lanthanide ions. For the Cd–Er clusters, 3 exhibits better NIR luminescence properties than 4. The long-chain Schiff base ligands show “linear” configurations in these clusters, resulting in the large sizes of 1–4. The drum-like structures of 1–4 have inner cavities with the internal sizes approximately 6 × 11 × 11 A, and some solvent molecules such as H2O, MeOH and EtOH are enclosed in the drums. Interestingly, the Cd–Sm cluster 1 shows visible and NIR luminescent sensing of metal cations and exhibits high selectivity to Zn2+ and Fe3+ ions.

Self-assembly of Luminescent Zn-Ln (Ln = Sm and Nd) Nanoclusters with a Long-chain Schiff Base Ligand

Two 12-metal Zn–Ln nanoclusters [Zn8Ln4L8(OAc)8](OH)4 (Ln = Sm (1) and Nd (2)) were prepared using a long-chain Schiff base ligand with a flexible (CH2)3O(CH2)2O(CH2)3 backbone. These two Zn–Ln clusters possess interesting rectangular structures. The long-chain Schiff base ligand adopts a “linear” configuration in the structures, resulting in the large sizes of 1 and 2 (about 9 × 19 × 28 A). Chromogenic Zn/L components in the clusters can act as efficient sensitizers for lanthanide luminescence, and 1 and 2 exhibit emission from Sm3+ and Nd3+, respectively. Their visible and NIR luminescence properties were investigated.

Construction and Luminescence Properties of 4f and d-4f Clusters with Salen-Type Schiff Base Ligands

The synthesis, crystal structures, and photophysical properties of twenty-three 4f and d-4f clusters based on eight salen-type Schiff base ligands are described in this chapter. Most of these lanthanide-based clusters exhibit interesting “enclosed” structures, such as multi-decker, “twisted,” and drum-like structures. In these polynuclear complexes, the multidentate salen-type ligands can efficiently sensitize lanthanide emissions by serving as antennas that absorb excitation light and transfer the energy to the lanthanide centers. With the lanthanide ions encapsulated by chromophoric salen-type ligands and shielded from solvent molecules which can quench the emissions from lanthanide ions, those lanthanide-based clusters with “enclosed” structures show impressive luminescence properties.

Luminescent Polynuclear Zn- and Cd-Ln Square-Like Nanoclusters With a Flexible Long-Chain Schiff Base Ligand

Two series of Zn-Ln and Cd-Ln nanoclusters [Ln4Zn8L2(OAc)20(OH)4] [Ln = Nd (1), Yb (2), and Sm (3)] and [Ln2Cd2L2(OAc)2(OH)2(OCH3)2] [Ln = Nd (4), Yb (5), and Sm (6)] were prepared using a long-chain Schiff base ligand with a flexible (CH2)2O(CH2)2O(CH2)2 chain. All these clusters show square-like structures. The Schiff base ligands show “linear” configurations in the structures of 1-6, and the metric dimensions of Zn-Ln and Cd-Ln clusters measure ~8 × 14 × 21 and 8 × 12 × 12 Å, respectively. The study of luminescence properties shows that the Zn/L and Cd/L chromophores can effectively transfer energy to the lanthanide ions, and 1-6 show visible and NIR emissions.