Herein we report the synthesis and characterization of a dinuclear Tb single-molecule magnet (SMM) with two [TbPc] units connected via a fused-phthalocyaninato ligand. The stable and robust complex [(obPc)Tb(Fused-Pc)Tb(obPc)] (1) was characterized by using synchrotron radiation measurements and other spectroscopic techniques (ESI-MS, FT-IR, UV). The magnetic couplings between the Tb ions and the two π radicals present in 1 were explored by means of density functional theory (DFT). Direct and alternating current magnetic susceptibility measurements were conducted on magnetically diluted and nondiluted samples of 1, indicating this compound to be an SMM with improved properties compared to those of the well-known [TbPc] and the axially symmetric dinuclear Tb phthalocyaninato triple-decker complex (Tb(obPc)). Assuming that the probability of quantum tunneling of the magnetization (QTM) occurring in one TbPc unit is P, the probability of QTM simultaneously occurring in 1 is P, meaning that QTM is effectively suppressed. Furthermore, nondiluted samples of 1 underwent slow magnetic relaxation times (τ ≈ 1000 s at 0.1 K), and the blocking temperature (T) was determined to be ca. 16 K with an energy barrier for spin reversal (U) of 588 cm (847 K) due to D geometry and weak inter- and intramolecular magnetic interactions as an exchange bias (H), reducing QTM. Four hyperfine steps were observed by micro-SQUID measurement. Furthermore, solution NMR measurements (one-dimensional, two-dimensional, and dynamic) were done on 1, which led to the determination of the high rotation barrier (83 ± 10 kJ/mol) of the obPc ligand. A comparison with previously reported Tb triple-decker compounds shows that ambient temperature NMR measurements can indicate improvements in the design of coordination environments for SMMs. A large U causes strong uniaxial magnetic anisotropy in 1, leading to a χ value (1.39 × 10 m) that is larger than that for Tb(obPc) (0.86 × 10 m). Controlling the coordination environment and spin arrangement is an effective technique for suppressing QTM in TbPc-based SMMs.

The design of larger architectures from smaller molecular building blocks by element-element coupling reactions is one of the key concerns of synthetic chemistry, so a number of strategies were developed for this bottom-up approach. A general scheme is the coupling of two elements with opposing polarity or that of two radicals. Here, we show that a B-B coupling reaction is possible between two boron analogues of the ethyl cation, resulting in the formation of an unprecedented dicationic tetraborane. The bonding properties in the rhomboid B₄ core of the product can be described as two B-B units connected by three-centre, two-electron bonds, sharing the short diagonal. Our discovery might lead the way to the long sought-after boron chain polymers with a structure similar to the silicon chains in β-SiB₃. Moreover, the reaction is a prime textbook example of the influence of multiple-centre bonding on reactivity.

Cyclopentadienyl ligands functionalized by quinoline or N,N-dimethylaniline have an ideal and rigid geometry for the formation of half-sandwich compounds. As a result, stable chromium(III) complexes 5−8 with intramolecular nitrogen coordination have been obtained. Treatment with MAO leads to highly active, temperature-stable catalysts for the polymerization of ethylene.

The new paramagnetic quinolyl-functionalized Cp chromium(III) complexes 4-8, which serve as precursors for highly active olefin polymerization catalysts, have been synthesized and were investigated together with the known complexes 1-3 by 1 H NMR. Full assignment of the observed NMR signals in these systems was achieved by comparison of the different spectra and by spin unrestricted density functional calculations (UB3LYP level) of the Fermi contact term at the hydrogen atoms. All the geometries were optimized using the experimentally determined solid-state molecular structures as starting points. We obtained a very good correlation (r 2 ) 0.97) between calculated Fermi contact spin densities at the UB3LYP/6-311G(d) level and experimental paramagnetic 1 H NMR shifts. Polarization basis set functions at heavy elements are required to reproduce experimental results, whereas polarization functions at hydrogen atoms and/or diffuse functions do not improve the results. The good correlation between calculated and experimental results indicates that the experimental hyperfine shifts are dominated by Fermi contact interactions. Nevertheless, we were able to identify and estimate non-negligible dipolar contributions to the chemical shifts for some protons. It is possible to predict 1 H NMR shifts of similar organometallic compounds and to obtain structural information of in situ generated paramagnetic species, which play a key role in several catalytic transformations with paramagnetic catalysts. Additionally, calculations provided us with detailed information of the spin density distribution along the molecular systems.