The largest aluminum molecular rings: Phenol‐thermal synthesis, photoluminescence, and optical limiting

Abstract

It is of great interest to modulate the photophysical properties by atomically precise chemical control. The incorporation of conjugated ligands into crystalline materials provides a platform for molecular‐level interpretation of the structure‐activity relationship. Herein, we reported the phenol‐thermal and scale‐up synthesis of a new family of remarkably stable aluminum molecular rings. They are assembled by twenty AlIII ions with large conjugated ligands and phenols, representing the currently largest sizes (up to 4 nm in diameter) in the field of main group metal oxo clusters. Phenols are not only reaction medium but also auxiliary bridging ligands on the surface of macrocyclic molecules. In addition, they are either parallel to the center of the molecular ring or inserted into the molecular ring, or form dimers/tetramers that bind macrocyclic molecules to form supramolecular structures. These macrocyclic rings are hydrophobic and ultra‐stable, evidenced by retaining their morphology and crystalline when exposed to air for more than a year. Compared with the pristine conjugated ligands, they exhibit coordination‐enhanced fluorescence. By dispersing them into a polydimethylsiloxane (PDMS) matrix, we prepared transparent and flexible PDMS thin films for coupling flexible display and nonlinear optical application. Our discovery of such atomically precise rings provides a platform for the fine‐tuning of photo‐related performances.

Ligand evolution on trigonal bipyramidal boron imidazolate cages for enhanced optical limiting

“…The results show that the corresponding nonlinear absorption coefficient β of BIF-136@PDMS-BIF-141@PDMS prepared in this work is in the range from 4.8 to 90.0 × 10 −10 m W −1 . In the OL materials prepared with PDMS, BIF-141@PDMS (90 × 10 −10 m W −1 ) is better than the aluminum oxide cluster materials known to us (AlOC-90-AlOC-95, 0.75-7.18 × 10 −10 m W −1 ) 55 and is comparable with excellent traditional porphyrin@PDMS materials (135 × 10 −10 ∼ ZnTPyP-1@PDMS and 40 × 10 −10 m W −1 ∼ ZnTPyP-2@PDMS). 53 Moreover, the optical limiting threshold values of BIF-141 and BIF-140 (F OL , defined as the input fluence at the location of half of the linear transmittance) were found to be 1.43 J cm −2 and 1.95 J cm −2 , which are superior to the values for the reported materials based on KBr tablets of cage-based cocrystal PTC-235 (3.90 J cm −2 ).…”

Solvent-controlled synthesis of an Al12-oxo molecular ring and Al24-oxo truncated metallo-cube

“…31 For this dilemma, recently, a new strategy known as coordination delayed hydrolysis has been adopted by Zhang et al to synthesize a series of Al-oxo clusters by choosing monodentate carboxylic acid ligands and organic aluminium salts under solvothermal conditions. [32][33][34][35] Most of these Al-oxo clusters feature the structures of molecular rings from Al 8 to the largest Al 20 constructed using different large conjugated carboxylic acids. 33,34,36 The different peripheral ligands realize luminescence modulation of Al 20 molecular rings from blue to green.…”

“…[32][33][34][35] Most of these Al-oxo clusters feature the structures of molecular rings from Al 8 to the largest Al 20 constructed using different large conjugated carboxylic acids. 33,34,36 The different peripheral ligands realize luminescence modulation of Al 20 molecular rings from blue to green. Besides, other Al clusters also display luminescence properties, which originated from the luminescence of the corresponding ligands.…”

Gradual Size Enlargement of Aluminum-Oxo Clusters and the Photochromic Properties

“…Compared to these ring-shaped transition and lanthanide metal clusters, main-group metal ring clusters are relatively limited, especially aluminum clusters, because of the rapid hydrolysis of Al 3+ ions. Until recently, a series of ring-shaped Al 8 , Al 10 , Al 12 , Al 16 , Al 18 , and Al 20 have been obtained by choosing monodentate carboxylic acid ligands and organic aluminum salts under solvothermal conditions. − The assembly of such structural clusters is closely related to the abundant oxygen coordination sites of peripheral organic ligands . Therefore, suitable abundant oxygen organic ligands, such as polyalcohol and simple monodentate carboxylic acid, display great potential to induce the formation of ring-shaped aluminum-oxo clusters.…”