A Mg-CP with in Situ Encapsulated Photochromic Guest as Sensitive Fluorescence Sensor for Fe 3+ /Cr 3+ Ions and Nitro-Explosives.

Here we report a fluorescent magnesium coordination polymer (Mg-CP), namely, [CH3 -dpb]2 [Mg3 (1,4-NDC)4 (μ-H2 O)2 (CH3 OH)(H2 O)]·1.5H2 O (1, 1,4-H2 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 [Mg3 (COO)8 (μ-H2 O)2 ]. The dpb molecules were in situ reacted with CH3 OH resulting in photochromic cations of [CH3 -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 Fe3+ /Cr3+ 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 [CH3 -dpb]+ guests, 1 exhibited reversible photochromic behavior.