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A series of mononuclear lanthanide complexes [Ln( L1 )(NO 3 ) 3 ], (Ln = Dy(III), 1 ; Tb(III), 3 ; and Eu(III), 4 ; L1 = ( N 1 E , N 2 E )- N 1 , N 2 -bis((1-methyl-1 H -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(NO 3 ) 3 ·6H 2 O under solvothermal conditions. L1 ligand is produced via an in situ Schiff base reaction of two molecules of L2 and one molecule of L3 . The metal center Ln(III) is in a N 4 O 6 environment formed by L1 and NO 3 - . NaSCN is added on the basis of 1 synthesis. One SCN - replaces one of the three coordinated NO 3 - anions in the 1 structure, and the complex [Dy( L1 )(NO 3 ) 2 (SCN)]·CH 3 CN ( 2 ) is synthesized. The complex 1 shows 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 3 and 4 show an excellent luminescence response to tetrahydrofuran (THF). Lastly, 2 obtained 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.

The solvent-induced topological and structural diversities of two Co(II) complexes, namely, [Co(L) 2 (SCN) 2 ] ( Co1 ) and [Co 2 (L) 2 (SCN)(OAc) 3 ] ( Co2 ) (L = 8-methoxyquinoline), were comparatively analyzed. Certain proportions of L, Co(OAc) 2 ·4H 2 O, and NaSCN were mixed and dissolved in CH 3 OH at 60 °C to obtain complex Co1 . Complex Co2 , an asymmetric dinuclear compound, was obtained by simply replacing CH 3 OH with CH 3 CN as the solvent. The Co(II) ion in complex Co1 was coordinated by the N 4 O 2 mode provided by two L ligands and two SCN - anions. The two Co(II) ions in Co2 were in the N 2 O 4 and NO 5 coordination environment and were linked by two μ 2 -OAc - bridges and one rare μ 3 -OAc - bridge. Weak interaction analysis revealed that complexes Co1 and Co2 exhibited 6-connected shp and 14-connected fcu nets, respectively. Magnetic studies showed that Co1 demonstrated single-ion magnet behavior under 2000 Oe. These behaviors are indicative of clearly field-induced single-ion magnetic behavior with U eff = 34.7(2) K and τ 0 = 2.7(2) × 10 -7 s under 2000 Oe dc field, respectively. By contrast, Co2 lacked frequency dependence under zero-field conditions. Electrospray ionization mass spectrometry indicated that two complexes were stable in N , N -dimethylformamide., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)

A clear dependence on the ligand has been observed for the magnetic properties of a closely related series of Co(II) cubane structures, viz. [Co 4 (mbm or bm) 4 (ROH) 4 Br 4 ] (1-MeOH, 1-EtOH, 2-MeOH, and 2-EtOH, where 1 = [Co 4 (mbm) 4 Br 4 ], 2 = [Co 4 (bm) 4 Br 4 ], bm = (1H-benzo[d]imidazol-2-yl)methanolate. and mbm = 1-Me-bm.) The [Co 4 (OR) 4 ] cubane core consists of an octahedral Co II center chelated by the alkoxide oxygen and imidazole nitrogen atoms from monoanionic bm or mbm and coordinated by methanol/alcohol and bromine. Interestingly, electrospray ionization mass spectrometry (ESI-MS) indicates that 1-MeOH and 2-MeOH are unstable in methanol and transformed to the butterfly [Co 4 L 6 ] 2+ but that 1-EtOH and 2-EtOH are 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 (T B ). Consequently, the compounds with mbm, 1-MeOH and 1-EtOH, exhibit T B > 2 K as shown by the relaxation of magnetization in zero applied dc field where the barriers U eff /k B are respectively 27 and 21 K and relaxation times are τ 0 = 1.3 × 10 -9 and 9.7 × 10 -9 s. However, the compounds with bm, 2-MeOH and 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.