Sequential Aggregation of Heterometallic {M4X4}-Cubanes to Wheel-Shaped In10Ni8-Oxo Clusters for Optical Limiting Application

It is extremely challenging but critical to regulatethe structuralattributes and physicochemical behaviors of metal-oxo clusters ina controllable manner. Connecting versatile building units and importingaromatic ligands into crystalline materials facilitates the constructionof unprecedented structures and provides a platform for the interpretationof structure-activity relationships at the molecular level.In this work, the solvent effect and organic-ligand-induced effectare exploited to formulate and regulate the variety and connectionmodes of cuboidal {M4X4} building units (M=In, Ni; X= O, Cl) in a controlled and incremental fashion. Not onlywere the inorganic basic-cubane and its dimeric analogue isolatedbut also their hexameric aggregation into an In10Ni8-oxo cluster with a wheel-shaped architecture was realizedwith the assistance of aromatic carboxylates. The In10Ni8-oxo cluster presents the largest size record in the realmof InOCs, and its peripheral surface could be modified to modulatetheir corresponding physicochemical properties; in particular, thebenzoate and naphthoate groups can bring in abundant & pi;& BULL;& BULL;& BULL;& pi;stacking interactions. Based on the results of Z-scan third-ordernonlinear optical (NLO) measurements, these clusters present highreverse saturable absorption (RSA) suitable as optical limiting (OL)materials and constitute an instructive comparison that the generaltrend of the OL effect is gradually enhanced with the accumulationof more {M4X4}-cubanes including heavy atomsas well as richer and stronger & pi;& BULL;& BULL;& BULL;& pi; stackinginteractions and better delocalization. This work not only startsthe research on InOCs-based optical limiting materials but also providestrategies of regulating building units for constructing heterometallicclusters.

Automated summary

This study demonstrates the controllable formulation and regulation of variety and connection modes of cuboidal {M4X4} building units (M=In, Ni; X= O, Cl) by exploiting solvent effect and organic-ligand-induced effect. The formation of the In10Ni8-oxo cluster with a wheel-shaped architecture is achieved with the assistance of aromatic carboxylates, presenting the largest size record in the realm of InOCs. The In10Ni8-oxo cluster shows high reverse saturable absorption, making it suitable as an optical limiting material.