N‐Methyl‐4‐pyridinium Tetrazolate Zwitterion‐Based Photochromic Materials

Abstract N , N′ ‐Disubstituted bipyridinium (viologen) and N ‐monosubstituted bipyridinium compounds are well known for their electron‐transfer (ET) photochromic behavior. Their modification has exclusively focused on the N‐substituents to date. For the first time, we have studied the photochromic behavior when one pyridyl ring of the bipyridinium is substituted with a multifunctional azole group, and have found that two new coordination compounds based on N ‐methyl‐4‐pyridinium tetrazolate (mptz) zwitterion, [Zn(mptz) 2 Br 2 ] ( 1 ) and [Cd 3 (mptz) 2 Cl 6 ] n ⋅4 n H 2 O ( 2 ), exhibit typical ET photochromic behavior owing to photoinduced ET from halogen anion to the mptz ligand. This work demonstrates a new simple, neutral photoactive molecule with electron‐accepting ability, which may act as a photoactive component for materials with potential photoswitching and photocatalysis applications.