Structure-Directing and Template Roles of Aromatic Molecules in the Self-Assembly Formation Process of 3D Holmium–Succinate MOFs

Highlighting Recent Crystalline Engineering Aspects of Luminescent Coordination Polymers Based on F-Elements and Ditopic Aliphatic Ligands

Three principal factors may influence the final structure of coordination polymers (CPs): (i) the nature of the ligand, (ii) the type and coordination number of the metal center, and (iii) the reaction conditions. Further, flexible carboxylate aliphatic ligands have been widely employed as building blocks for designing and synthesizing CPs, resulting in a diverse array of materials with exciting architectures, porosities, dimensionalities, and topologies as well as an increasing number of properties and applications. These ligands show different structural features, such as torsion angles, carbon backbone number, and coordination modes, which affect the desired products and so enable the generation of polymorphs or crystalline phases. Additionally, due to their large coordination numbers, using 4f and 5f metals as coordination centers combined with aliphatic ligands increases the possibility of obtaining different crystal phases. Additionally, by varying the synthetic conditions, we may control the production of a specific solid phase by understanding the thermodynamic and kinetic factors that influence the self-assembly process. This revision highlights the relationship between the structural variety of CPs based on flexible carboxylate aliphatic ligands and f-elements (lanthanide and actinides) and their outstanding luminescent properties such as solid-state emissions, sensing, and photocatalysis. In this sense, we present a structural analysis of the CPs reported with the oxalate ligand, as the one rigid ligand of the family, and other flexible dicarboxylate linkers with –CH₂– spacers. Additionally, the nature of the luminescence properties of the 4f or 5f-CPs is analyzed, and finally, we present a novel set of CPs using a glutarate-derived ligand and samarium, with the formula [2,2′-bipyH][Sm(HFG)₂ (2,2′-bipy) (H₂O)₂]•(2,2′-bipy) (α-Sm) and [2,2′-bipyH][Sm(HFG)₂ (2,2′-bipy) (H₂O)₂] (β-Sm).

Effects of template molecules on the structures and luminescence intensities of a series of porous Tb-MOFs based on the 2-nitroterephthalate ligand

Four novel porous Tb(iii) metal-organic frameworks (Tb-MOFs) have been designed and prepared hydrothermally from 2-nitroterephthalate (2-H2ntp), namely {[Tb(2-ntp)1.5(H2O)]·H2O} n (1), {[Tb(2-ntp)2(H2O)]·4,4'-Hbipy} n (2), {[Tb(2-ntp)2(H2O)]·2,4-Hbipy} n (3), and {[Tb(2-ntp)2(H2O)]·(1,4-H2bbi)0.5} n (4) (4,4'-bipy = 4,4'-bipyridine; 2,4-bipy = 2,4-bipyridine; 1,4-bbi = 1,4-bisbenzimidazole). X-ray diffraction structural analyses show these Tb-MOFs are porous and are based on Tb3+ ions and 2-nitroterephthalate, in which water molecules (1) or protonated N-donor ligands (2-4) exist as templates. The fluorescence properties of complexes 1-4 could be associated with the characteristic peaks of Tb(iii) ions, and the existence of different guest molecules affects the intensities of peaks, which means that these could be potential fluorescence materials, with intensities adjusted using guests.

Four Pb(ii) metal–organic frameworks with increasing dimensions: structural diversities by varying the ligands

Four complexes with 1D, 2D and 3D frameworks were synthesized by three rigid, linear ligands. The ligands' effects and luminescence properties were studied.

Solvent-induced synthesis of cobalt(ii) coordination polymers based on a rigid ligand and flexible carboxylic acid ligands: syntheses, structures and magnetic properties

The structural formations for compounds 1–5 are effected by using different solvents or different carboxylic acid ligands.