Preparation and photochromism of piperidine decatungstate

A new photochromic compound, piperidine decatungstate (PiPdDT), (C₅H₁₀NH₂)₄W₁₀O₃₂ was prepared; its TG curve, UV and IR spectra were studied. On exposure to UV light, both its crystal and aqueous solution turn blue with absorption spectra appearing at 756 and 720–742 nm. The ESR signal, recorded at 100 K on a frozen solution of PiPdDT in water after exposure to UV light, centered around g = 1.839. The fading rate constant after exposure to UV light, is k = 7.9 × 10⁻⁴s⁻¹, and its quantum yield was determined as ϕw(v) = 22.2, which is higher than the values yet reported for polytungstates in literature.