Two low-coordinated coordination polymers, [Co(nip)2][EMIm]2 (1) (H2nip = 5-nitryl-isophthalic acid, EMIm = 1-ethyl-3-methyl imidazolium) and [Co(bptc)][EMIm]2·H2O (2) (H4bptc = 2,2′,4,4′-biphenyltetracarboxylic acid) were prepared under an ionic liquid medium, demonstrating that ionothermal synthesis may act as a powerful tool in the preparation of low-coordinated coordination polymers (LCCPs). Investigation on the synthetic conditions shows that a lower reaction temperature, appropriate ratio of ligand to metal ions, and hydrophobic ionic liquid are of key importance for the formation of LCCPs. Both of them feature interesting hydration–dehydration properties with reversible color changing from deep purple to pink. Solid state UV-Vis spectra measurements also indicate that the largest adsorbtion peaks are blue-shifted under hydration. Significantly, under hydration and dehydration processes, compound 2 exhibits a magnetic transformation from anti-ferromagnetism to ferrimagnetism. Essentially, this transformation arises from the formation of new propagating ways triggered by guest water.

•Four new lanthanide-based MPFs were obtained by ionothermal method.•DFT calculation reveals that bromine ions play an important role in their structure.•Luminescence analysis shows that 3 and 4 behave good fluorescence properties.A series of new isomorphic lanthanide-based metal–peptide frameworks, [Ln(PODC)(H2O)2]Br (Ln = La(1), Nd(2), Eu(3), Tb(4), H2PODC = 2, 5-piperazinedione-1, 4-diacetic acid), were synthesized under the ionic liquid medium. Crystal structure measure results exhibit that they are new three-dimensional frameworks, where bromine anions of ionic liquid are enveloped in the pore. Interestingly, it is found that bromine anions can effectively counteract the effects of lanthanide ions (e.g. lanthanide contraction). Via the first-principles DFT calculation, it is obtained that bromine anions of ion liquid influence the electronic properties of PODC2 − ligand and thereby directly control the structure. Luminescence analysis demonstrates that compounds 3 and 4 have good fluorescence properties, where the emission peaks can be ascribed to the transitions of 5D0 → 7FJ (J = 0, 1, 2, 3, 4) for 3 and 5D4 → 7FJ (J = 6, 5, 4, 3) for 4.Four lanthanide-based metal–peptide frameworks under ionothermal condition exhibit new three-dimensional framework and further reveal that anion of ion liquid plays an important role in structure by DFT calculation.

Two Cu(II)-based coordination polymers, {Cu(CMBA)(H2O)}n (1) and {Cu(CMBA)(4, 4′-bpy)0.5(H2O)}n (2) (H2CMBA = 2-(Carboxymethyl-amino)-3-methyl-butyric acid, 4, 4′-bpy = 4, 4′-bipyridine), were obtained under microwave irradiation. Magnetic property measurements indicate that both of them feature ferromagnetic characteristic. Furthermore, quantum Monte Carlo studies respectively reveal that the coupling parameters between the adjacent Cu(II) ions are 8.20 cm− 1 for 1 and 3.60 cm− 1 for 2, respectively. Moreover, it is found that 4, 4′-bpy ligand serves as a weak antiferromagnetic propagation pathway with − 0.36 cm− 1 between two adjacent Cu(II) chains in 2, resulting in the differences of magnetization between 1 and 2.Two Cu(II)-based coordination polymers prepared under microwave irradiation reveal ferromagnetic propagation of 8.20 cm− 1 for 1 and 3.60 cm− 1 for 2 by quantum Monte Carlo method.Highlights► Two Cu(II) based coordination polymers of H2CMBA ligand were obtained. ► Magnetic measure exhibits that they feature ferromagnetic properties. ► Quantum Monte Carlo studies reveal the coupling parameters of two Cu(II) ions. ► 4, 4′-bpy ligand exhibits weak antiferromagnetic interaction with − 0.36 cm− 1.