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The assembly process of lanthanide clusters often involves various complex assembly methods. Hence, studying the stepwise assembly mechanism is extremely difficult. In the assembly process of lanthanide clusters, if the in situ reaction or competitive reaction is involved, the reaction intermediates undergo rapid and complex changes, which makes research on the assembly mechanism even more difficult. Herein, 1-methyl-1H-benzo[d]imidazole-2-carbaldehyde (La) and 1-aminonaphthalen-2-ol (Lb) undergo a stepwise assembly reaction with Dy(III) salts under the promotion of a in situ Schiff base reaction to achieve Dy2synthesis. The stepwise assembly mechanism is La+ Lb→ HL1→ Dy1 → Dy2. In the above Dy2formation reaction, Lais changed to 2-hydroxy-3-methoxybenzaldehyde (Lc), and then pyridin-2-ylmethanamine (Ld) is added. We have found that two different Schiff base ligands are formed in situ, and both are coordinated with Dy(III) ions to form a mixed ligand cluster Dy4by competitive and stepwise assembly. The assembly mechanism is Lb+ Lc/Lc+ Ld→ L2/L3→ Dy1′ → Dy2′ → Dy3′ → Dy4′. We have tracked the competitive assembly process driven by the in situ Schiff base reaction in the lanthanide clusters and proposed its competitive assembly mechanism. Magnetic relaxation studies reveal single-molecule magnet behavior under zero external direct-current field with Ueff= 19.6 K and τo= 1.7 × 10–5s for Dy2and Ueff= 10.0 K and τo= 2.6 × 10–5s for Dy4.

A series of mononuclear lanthanide complexes [Ln(L1)(NO3)3], (Ln = Dy(III), 1; Tb(III), 3; and Eu(III), 4; L1= (N1E,N2E)-N1,N2-bis((1-methyl-1H-benzo[d]imidazol-2-yl)methylene)cyclohexane-1,2-diamine) is obtained by reacting N-methylbenzimidazole-2-carbaldehyde (L2) and 1,2-cyclohexanediamine (L3) with Ln(NO3)3·6H2O under solvothermal conditions. L1ligand is produced via an in situ Schiff base reaction of two molecules of L2and one molecule of L3. The metal center Ln(III) is in a N4O6environment formed by L1and NO3–. NaSCN is added on the basis of 1synthesis. One SCN–replaces one of the three coordinated NO3–anions in the 1structure, and the complex [Dy(L1)(NO3)2(SCN)]·CH3CN (2) is synthesized. The complex 1shows excellent luminescence response to petroleum ether (PET), an organic solvent. To the best of our knowledge, this study is the first to use a complex for sensing responses to PET. When the metal center is changed, the obtained mononuclear complexes 3and 4show an excellent luminescence response to tetrahydrofuran (THF). Lastly, 2obtained by changing the coordinating anion shows an excellent luminescence response to dichloromethane. Herein, for the first time, we regulate the metal center and coordinating anion of lanthanide complexes to adjust the recognition and response of these complexes to different organic solvents.

High-nuclear lanthanide clusters are generally formed by the rapid accumulation of simple building units. Thus, tracking and observing the stepwise assembly process, which is vital for understanding the assembly mechanism, are extremely difficult. Herein, the decanuclear nanocluster [Dy10(L1)6(μ5-NO3)2(OAc)10(HOAc)2]·8H2O (Dy10, H3L1= (E)-3-((3-ethoxy-2-hydroxybenzylidene)amino)propane-1,2-diol) was obtained from the reaction of Dy(NO3)3·6H2O, Dy(OAc)3·6H2O, 3-ethoxy-2-hydroxybenzaldehyde (L2), and 3-amino-1,2-propanediol (L3). The reaction process was further tracked by time-dependent high-resolution electrospray ionization mass spectrometry, and seven reaction intermediate fragments were screened. A stepwise assembly mechanism was observed based on these fragments, that is, L → Dy1 → Dy2 → Dy3 → Dy4 → Dy5 → Dy6 → Dy10. This study is the first to discover a stepwise assembly mechanism during the formation of high-nuclear lanthanide clusters (cluster nucleus > 3). Magnetic studies have shown the multiple relaxation behavior of Dy10.

A clear dependence on the ligand has been observed for the magnetic properties of a closely related series of Co(II) cubane structures, viz. [Co4(mbmor bm)4(ROH)4Br4] (1-MeOH, 1-EtOH, 2-MeOH, and 2-EtOH, where 1= [Co4(mbm)4Br4], 2= [Co4(bm)4Br4], bm= (1H-benzo[d]imidazol-2-yl)methanolate. and mbm= 1-Me-bm.) The [Co4(OR)4] cubane core consists of an octahedral CoIIcenter chelated by the alkoxide oxygen and imidazole nitrogen atoms from monoanionic bmor mbmand coordinated by methanol/alcohol and bromine. Interestingly, electrospray ionization mass spectrometry (ESI-MS) indicates that 1-MeOHand 2-MeOHare unstable in methanol and transformed to the butterfly [Co4L6]2+but that 1-EtOHand 2-EtOHare stable in ethanol. Their magnetic susceptibilities suggest ferromagnetic coupling between the nearest cobalt centers to give a theoretical S= 4 × 3/2 ground state with considerable magneto-crystalline behavior. The packing and intermolecular interactions appear to influence the geometry of the cubes and thus the anisotropy of cobalt, which leads to different blocking temperatures (TB). Consequently, the compounds with mbm, 1-MeOHand 1-EtOH, exhibit TB> 2 K as shown by the relaxation of magnetization in zero applied dc field where the barriers Ueff/kBare respectively 27 and 21 K and relaxation times are τ0= 1.3 × 10–9and 9.7 × 10–9s. However, the compounds with bm, 2-MeOHand 2-EtOH, remain paramagnetic above 2 K and do not show nonlinear response of the ac susceptibilities. These findings reaffirm the subtle dependence of single-molecule magnetism on coordination geometry and intermolecular interaction.