Polyoxometalate/s-triazine hybrid heterostructures with ultrafast photochromic properties

As an emerging class of hybrid complexes, donor-acceptor (D-A) hybrid heterostructures, which combine the advantages of both organic and inorganic photoactive components, provide excellent platforms for the fabrication of photochromic materials with enhanced photo-responsive performances. Herein, four novel hybrid heterostructures, namely H₃TPT·(PW₁₂O₄₀)·2NMP (1), (H_1.5TPT)₂·(PW₁₂O₄₀) (2), (H₃TPT)₂·(SiW₁₂O₄₀)·2Cl·2MeCN (3), and H₃TPT·(HPMo₁₂O₄₀)·Cl·3NMP (4) (TPT is tri(4-pyridyl)-s-triazine, NMP is N-methylpyrrolidone), have been synthesized and characterized. Benefitting from the strong interactions (anion-π interactions) and matching electron energy levels between the donors and acceptors, some of them exhibited ultrafast photochromic behaviour even up to 1 second. Furthermore, based on experimental and theoretical calculations, the plausible PIET process and structure-activity relationship have been discussed in detail.