Synthesis and Magnetic Studies of Two Neutral, Bis-Ligand Fe(II) Complexes Containing Carbazole-Bis(tetrazole) Ligands

Previously reported carbazole-bis(tetrazole) (CzT^R) ligands (where R = iPr and CH₂-2,4,6-C₆H₂Me₃) were used to synthesize air-stable, six-coordinate, octahedral bis-ligand Fe(II) complexes (CzT^R)₂Fe. The synthesis and characterization of these complexes using ¹H nuclear magnetic resonance (NMR), X-ray crystallography, Mössbauer spectroscopy, and density functional theory (DFT) calculations are reported. Analysis of the magnetic properties revealed that the isopropyl derivative displays thermally induced spin crossover (SCO) over a temperature range of 150-350 K. This transition appears as an abrupt two-step transition in the solid state but simplifies to a smooth one-step transition in solution. The two-step transition in the solid state has been postulated to be due to lattice and solvation effects. In contrast, the slightly bulkier substituted CH₂-2,4,6-C₆H₂Me₃ (CH₂Mes) Fe complex displays dramatically different magnetic behavior with no SCO and magnetic data suggesting low-spin Fe(II) with a possible TIP contribution. DFT calculations support the postulate that the change in magnetic behavior is primarily due to the nature of the ligand substituents.

[Sm6O4(cbz)10(thf)6]·2C7H8: A Polynuclear Samarium Oxo Cluster Obtained from Carbazole-Driven Oxidation of Samarium Nanoparticles

Zerovalent samarium nanoparticles (1.7 ± 0.2 nm in size) are used as the starting material to prepare single crystals of the novel polynuclear samarium oxo cluster [Sm₆O₄(cbz)₁₀(thf)₆]·2C₇H₈. The reaction is performed by oxidation with carbazole (CbzH) in tetrahydrofuran (THF) at 50 °C with subsequent crystallization in toluene (C₇H₈). The oxo cluster contains noncharged molecular units with a central Sm₆O₄ core. Single-crystal structure analysis and infrared spectroscopy confirm the oxidation of CbzH with the formation of (cbz)^-. Polynuclear carbazole complexes are generally rare and here prepared using metal nanoparticles as a reactive starting material for the first time. The reaction with CbzH as a sterically demanding ligand exemplarily shows the feasibility of rare-earth-metal nanoparticles for obtaining new compounds with complex composition and structure.

Single-molecule magnet behavior in luminescent carbazolyl Dy(iii) octahedral complexes with a quasi linear N--Dy-N- angle

We report the synthesis, photoluminescence and magnetic properties of two octahedral dysprosium complexes [DyR2(py)4][BPh4]·2py (1) and [DyR2(THF)4][BPh4] (2) (R = carbazolyl, py = pyridine, THF = tetrahydrofuran) exhibiting a quasi linear N-Dy-N angle in the axial direction, suitable for providing a coordination environment allowing the zero-field slow relaxation of magnetization.