Synthesis of Zirconium Boron‐Oxo Clusters With Tunable Third‐Order Nonlinear Optical Response

ABSTRACT Due to the weak coordination ability with metals and the easy self‐condensation of arylboronic acids, the development of organic–inorganic hybrid metal boron‐oxo clusters is still challenging. In this study, by leveraging the in situ condensation reaction between boron sources (e.g., trimethyl borate and arylboronic acids) and dioxime, a series of dioxime‐modified zirconium boron‐oxo clusters (Zr‐BOCs) was synthesized via a pyrazole‐thermal condition. In these structures, dioximes not only induce the polymerization of boric acid into clusters but also chelate Zr ions, enabling electronic coupling between B‐O and Zr‐O moieties and resulting in a nearly planar cluster core Zr 2 B 8 O 10 . Taking advantage of the open Zr sites and the boron atom hybridization change from sp 2 to sp 3 , we sequentially introduced aromatic carboxylic acids and arylboronic acids to controllably modulate both the planarity and the electronic structure of the Zr 2 B 8 O 10 core. In particular, the Zr‐O quadrilateral ring in BOC‐13 (Zr 2 (Dmg) 4 (CH 3 OB 4 O 5 ) 2 (BA) 2 ) demonstrates aromaticity revealed by DFT calculations. Its conjugation with planar B‐O clusters extends electron delocalization from a p‐p‐π to a d‐p‐π system, significantly enhancing third‐order nonlinear optical (NLO) properties and achieving a minimum normalized transmittance ( T min ) of 0.20 . The present work establishes a modular synthesis strategy for organic‐inorganic hybrid boron‐oxo clusters with a d‐p‐π delocalization system.