A Mg-CP with in Situ Encapsulated Photochromic Guest as Sensitive Fluorescence Sensor for Fe3+/Cr3+ Ions and Nitro-Explosives

Here we report a fluorescent magnesium coordination polymer (Mg-CP), namely, [CH 3 -dpb] 2 [Mg 3 (1,4-NDC) 4 (μ-H 2 O) 2 (CH 3 OH)(H 2 O)]·1.5H 2 O ( 1, 1,4-H 2 NDC = 1,4-naphthalene dicarboxylic acid, dpb = 1,4-bis(pyrid-4-yl)benzene). Compound 1 possesses a three-dimensional (3D) host–guest structure constructed by the 1,4-NDC linkers bridging the linear trinuclear secondary building units of [Mg 3 (COO) 8 (μ-H 2 O) 2 ]. The dpb molecules were in situ reacted with CH 3 OH resulting in photochromic cations of [CH 3 -dpb] + that acted as guests located in the channels parallel to the b -axis. Photoluminescence (PL) studies indicated that 1 showed a strong green emission demonstrating sensitive fluorescence sensing of Fe 3+ /Cr 3+ metal ions and nitro-explosive compounds. Compound 1 represents the first PL Mg-CP as a fluorescent probe for detecting metal ions. Moreover, because of the in situ encapsulation of photochromic [CH 3 -dpb] + guests, 1 exhibited reversible photochromic behavior.