Octahedral Molybdenum and Vanadium (Oxo)clusters as Dual Photoinitiators and Crosslinkers for PEGDA Hydrogels with Antibacterial Activity

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Covalent integration of inorganic clusters into polymer matrices opens the way to the creation of functional materials in which the identity of the cluster determines the behavior of the material. Here, Vanadium Lindqvist polyoxometalates [V6O13((OCH2)3CCH2-R))2]2– (abbreviated as V6-R, where R = OH, N3, mAcryl is (N3HC2)(C6H4)NHCOC(CH3)=CH2)) and octahedral molybdenum halide clusters [{Mo6I8}(X’6)]2– (abbreviated as Mo6-X’, where X’ is I or Acryl is O2CCH=CH2) demonstrate the unexpected behavior, and facilitate the poly(ethylene glycol) diacrylate (PEGDA) polymerization under mild UV irradiation. The V6-mAcryl and Mo6-Acryl clusters, which bear acrylate ligands grafted onto the inorganic core, fulfill both roles of photoinitiator and polymerizable building block at once, resulting in a composite copolymer network with PEGDA without any additional initiator, sensitizer, or chain-transfer agent. Operando infrared (IR) reaction kinetic monitoring and electron paramagnetic resonance (EPR) studies reveal the markedly differences of mechanistic details, highlighting the important role of hexavanadate core photoreduction and ·OH radical formation in the vanadate mediated processes. Scanning electron microscopy (SEM) reveals dramatically different hydrogel morphologies: Mo6-Acryl@PEGDA exhibits folded, “brain-like” thee-dimensional (3D) structures, while V6-mAcryl@PEGDA shows smooth, flat films. Mo6-Acryl@PEGDA exhibits potent antibacterial activity against Escherichia coli, whereas V6-mAcryl@PEGDA shows minimal bactericidal effect but moderate biocompatibility with L929 fibroblasts. This work establishes a tunable platform for integrating molecular inorganic clusters with metal–oxo and metal–metal bonds into polymer matrices, where cluster structure dictates morphology, kinetics, and biological function.

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