Long-Lived Photochromism in a Crystalline Hybrid Naphthalenediimide-Polyoxovanadate System

We developed (H₂N,N-dimenNDI)₂H₂V₁₀O₂₈ (N,N-dimenNDI = N,N-dimethylethylenediamine-substituted naphthalenediimide) as a photochromic hybrid cluster compound exhibiting a long-lived colored state. Upon photoirradiation, the hybrid decavanadate's coloration occurs in minutes and persists over multiple days─substantially longer-lived than molecular NDI that bleaches in <18 h and photodegrades if exposed for >15 min. Structural and spectroscopic analyses suggest the hybrid compound possesses a cluster-to-NDI electron-transfer pathway likely mediated by hydrogen-bonding and/or anion-π supramolecular interactions that can be suppressed or modified through amine side-arm methylation or polyoxometalate mixed valence, respectively. These findings suggest molecular structure-directing approaches to stabilize photoinduced charge separation.