Assembly of Homochiral Titanium-Oxo Clusters Protected by in situ Generated Chiral Ligands for Enhanced Photoelectrochemical Activity

Abstract

The synthesis of titanium oxo clusters (TOCs) with both chirality and photoactivity is urgently needed to expand their applications. However, this remains a significant challenge due to synthetic difficulties and limitations in chiral ligand selection. In this work, we have isolated two pairs of enantiomeric TOCs, [Ti ₃(µ ₃-O)( R/S-L1) ₂( ⁱPrO) ₆] ( R/S-Ti3; iPrOH = isopropanol, R/ S-L1 = R/ S-2’-hydroxy-[1, 1’- binaphthalen]-2-yl isopropyl hydrogenphosphate) and [Ti ₄(µ ₂-O)(µ ₄-O)( R/ S-L2) ₂(EtO) ₈] ( R/S-Ti4; EtOH = ethanol, R/ S-L2 = R/ S-2’-hydroxy-[1, 1’-binaphthalen]-2-yl ethyl hydrogenphosphate), via an in situ ligand transformation approach. The R/ S-L1 and R/ S-L2 ligands were obtained by alcoholysis of R/ S-L ( R/ S-1, 1’-binaphthyl-2, 2’-diyl hydrogenphosphate) in different reaction solvents. These ligands, with additional coordination sites, facilitated the formation of novel TOCs and improved their stability. Importantly, these clusters exhibited exceptional stability in solid state and maintained appreciable stability in solution. Furthermore, the introduction of chiral ligands not only imparts a homochiral nature to R/S-Ti3 and R/S-Ti4 but also confers upon them superior photoelectric properties due to ligand-to-metal charge transfer (LMCT) phenomena, as confirmed by theoretical calculations. This study offers a valuable synthetic strategy for preparing photoactive chiral TOCs, and we anticipate it will inspire new discoveries in the field of chiral metal nanoclusters.

Keywords

Chirality / Titanium-oxo clusters / Crystal engineering / Photoelectric performances / Theoretical calculation / In situ ligand transformation

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