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Solvents and metal ions play a crucial role in the construction of metal–organic frameworks (MOFs). Four novel three-dimensional (3D) metal–organic frameworks, namely {[Co2(nttba)(4,4′-bpy)0.5(H2O)2]·0.5H2O}n (1), {[Co(nttba)0.5(4,4′-bpy)0.5(H2O)2]·0.5H2O}n (2), {[Ni2(nttba)(4,4′-bpy)2(H2O)2]·(4,4′-bpy)·11H2O}n (3) and {[Zn(nttba)0.5(4,4′-bpy)0.5(H2O)2]·0.5H2O}n (4) have been synthesized by the reaction of different metal ions (Co2+, Ni2+ and Zn2+), 5′-nitro-[1,1′:3′,1′′-terphenyl]-3,3′′,5,5′′-tetracarboxylic acid (H4nttba) and 4,4′-bipyridine (4,4′-bpy) under solvothermal conditions. Among the four complexes, the synthesis methods of complexes 1 and 3 were the same except for different metal ions, while the synthesis methods of complexes 1 and 2 were the same except for different solvents and the amount of NaOH. Complexes 2 and 4 are isomorphic crystals. However, three different three-dimensional structures were obtained with different space groups and crystal systems, and the solvent void volumes of the three complexes are in the order, 3 (3D, 44.8%) > 1 (3D, 10%) > 2 (3D, 5.9%). In addition, magnetic analysis indicated that antiferromagnetic interactions exist between the neighboring metal ions in 1, 2 and 3. 4 is a highly selective and sensitive fluorescence chemosensor toward Fe3+ ions with good recyclability. In this work, the structure was reshaped by introducing different solvents and metal ions, and the roles and functions of the solvents and metal ions in the structure were studied, providing a feasible idea for the design and precise regulation of MOFs. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel "turn-on" fluorescent chemosensor for the detection of Al3+ was developed. • The probe exhibited anti-interference recognition and low detection limit of 22.0 nM. • The detection mechanism of the probe for Al3+ is the formation of Al-complex. • HL can be utilized as a film to detect Al3+ ions. Many Al3+ sensors have been reported in the literature, the lack of spectral features and poor coordination of Al3+ pose a significant challenge to detection. Herein, the design and synthesis of a Schiff's base (HL) sensor is reported, which exhibits a turn-on response to Al3+ in an aqueous solution, and the fluorescence color of HL from light green to cyan upon the addition of Al3+. The limit of detection (LOD) for Al3+ was determined to be 2.20 x 10−8 M. The mechanism for fluorescence sensing was revealed through the analysis of single-crystal X-ray diffraction, DFT, and UV–vis absorption spectra. HL gradually coordinated with Al3+ during the titration process, leading to the formation of HL-Al crystals. The outcome of this study resulted in the successful preparation and application of flexible and foldable films for visual detection of Al3+. [ABSTRACT FROM AUTHOR]

• A new viologen complex was successfully synthesized and characterized. • Under UV irradiation, the samples heated at 120 and 180℃showed different colors. • We construct a "AND" logic-gate strategy, different inputs lead to disparate results. Electron transfer is crucial for the rapid response of viologen-based complexes and investigating the factors that affect electron transfer has always been a major challenge. Herein, a new viologen-based complex, formulated as {[Zn 5 (cbbbc) 3 (BTC) 3 (μ 1 , 1 -OH)(H 2 O) 5 ]·22H 2 O} n , with a three-dimensional framework was successfully designed and synthesized by viologen ligand 1-(3-carboxybenzyl)-4,4′-bipyridinium chloride (Hcbbpy), trimesic acid (H 3 BTC) and Zn(NO 3) 2 ·6H 2 O. In particular, complex 1 does not exhibit photochromic properties. However, samples of complex 1 heated at 120 and 180 ℃ display tunable colors under UV light irradiation. The experimental results indicate that the compound's light response is less sensitive with higher water content in the lattice. The polarity and hydrogen bonding ability of lattice water in viologen-based complexes can interact with the donor of viologen, leading to a reduction in electron transfer. This study demonstrates the impact of lattice water on electron transfer in viologen-based complexes and offers insights for designing faster response complexes in the future. The light response of the complexes becomes less sensitive as the water content in the lattice increases. This is because the lattice water hinders the electron transfer of the complexes. [Display omitted] [ABSTRACT FROM AUTHOR]