Metal–organic frameworks based on a benzimidazole flexible tetracarboxylic acid: Selective luminescence sensing Fe3+, magnetic behaviors, DFT calculations, and Hirshfeld surface analyses

Abstract Four novel metal–organic frameworks constructed from benzimidazole flexible tetracarboxylic acid ligand, 1‐(3,5‐dicarboxylbenzyl)‐1H‐benzimidazole‐5,6‐dicarboxylic acid (H 4 L), have been prepared by a solvothermal method in the presence of N‐donor ancillary ligands (1,10‐phen = 1,10‐phenanthroline monohydrate, 4,4′‐bibp = 1,4‐di[pyridine‐4‐yl]benzene), namely, [Co 2 (L)(H 2 O) 3 ] n (1) , {[Cd 2 (L)(1,10‐phen)(H 2 O)]·2H 2 O} n (2) , {[Co 4 (L) 2 (4,4′‐bibp) 2 (H 2 O) 7 ]·4H 2 O} n (3) , and {[Ni 4 (L) 2 (4,4′‐bibp) 2 (H 2 O) 7 ]·4H 2 O} n (4) . Complexes 1 and 2 show a 3D supramolecular structure and crystallize in monoclinic space group P 2 1 /c . Complexes 3 and 4 are isomorphous and crystallize in monoclinic space group P n , and the respective metals exhibit a similar coordination environment. The H 4 L ligand behaved in different coordinated modes in Complexes 1–4 , namely, μ 6 ‐η 1 :η 1 :η 1 :η 0 :η 1 :η 1 :η 1 :η 1 :η 1 in 1 , μ 6 ‐η 1 :η 1 :η 1 :η 1 :η 1 :η 1 :η 2 :η 1 :η 1 in 2 , there are two coordination modes (μ 5 ‐η 0 :η 1 :η 1 :η 0 :η 1 :η 1 :η 1 :η 0 :η 1 and μ 5 ‐η 1 :η 1 :η 1 :η 0 :η 1 :η 1 :η 1 :η 0 :η 1 ) in 3 and 4 . Furthermore, photoluminescence and magnetic properties have been studied. The results indicate that Complexes 3 and 4 show strong antiferromagnetic and ferromagnetic coupling through M–O–C–O–M interactions, respectively. In particular, Complex 2 can sensitively and selectively detect Fe 3+ in aqueous systems, and the limit of detection (LOD) values of Fe 3+ is ∼0.19 mM.