Phenanthroline-Mediated Photoelectrical Enhancement in Calix[4]arene-Functionalized Titanium-Oxo Clusters.

Incorporating two organic ligands with different functionalities into a titanium-oxo cluster entity simultaneously can endow the material with their respective properties and provide synergistic performance enhancement, which is of great significance for enriching the structure and properties of titanium-oxo clusters (TOCs). However, the synthesis of such TOCs is highly challenging. In this work, we successfully synthesized a TBC4A-functionalized TOC, [Ti 2 (TBC4A) 2 (MeO) 2 ] ( Ti2 ; MeOH = methanol, TBC4A = tert-butylcalix[4]arene). By adjusting the solvent system, we successfully introduced 1,10-phenanthroline (Phen) and prepared TBC4A and Phen co-protected [Ti 2 (TBC4A) 2 (Phen) 2 ] ( Ti2-Phen ). Moreover, when Phen was replaced with bulky 4,7-diphenyl-1,10-phenanthroline (Bphen), [Ti 2 (TBC4A) 2 (Bphen) 2 ] ( Ti2-Bphen ), which is isostructural with Ti2-Phen , was obtained, demonstrating the generality of the synthetic method. Remarkably, Ti2-Phen demonstrates good stability and stronger light absorption, as well as superior photoelectric performance compared to Ti2 . Density functional theory (DFT) calculations reveal that there exists ligand-to-core charge transfer (LCCT) in Ti2 , while an unusual ligand-to-ligand charge transfer (LLCT) is present in Ti2-Phen , accompanied by partial LCCT. Therefore, the superior light absorption and photoelectric properties of Ti2-Phen are attributed to the existence of the unusual LLCT phenomenon. This study not only deeply explores the influence of Phen on the performance of the material but also provides a reference for the preparation of materials with excellent photoelectric performance.