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Recently, the choice of ligand and geometric control of mononuclear complexes, which can affect the relaxation pathways and blocking temperature, have received wide attention in the field of single-ion magnets (SIMs). To find out the influence of the coordination environment on SIMs, two four-coordinate mononuclear Co( ii ) complexes [NEt 4 ][Co(PPh 3 )X 3 ] (X = Cl − , 1; Br − , 2) have been synthesized and studied by X-ray single crystallography, magnetic measurements, high-frequency and -field EPR (HF-EPR) spectroscopy and theoretical calculations. Both complexes are in a cubic space group Pa 3̄ (No. 205), containing a slightly distorted tetrahedral moiety with crystallographically imposed C 3 v symmetry through the [Co(PPh 3 )X 3 ] − anion. The direct-current (dc) magnetic data and HF-EPR spectroscopy indicated the anisotropic S = 3/2 spin ground states of the Co( ii ) ions with the easy-plane anisotropy for 1 and 2. Ab initio calculations were performed to confirm the positive magnetic anisotropies of 1 and 2. Frequency- and temperature-dependent alternating-current (ac) magnetic susceptibility measurements revealed slow magnetic relaxation for 1 and 2 at an applied dc field. Finally, the magnetic properties of 1 and 2 were compared to those of other Co( ii ) complexes with a [CoAB 3 ] moiety. 

Three mononuclear tetrakis(pseudohalido)-cobalt( ii ) complexes (Ph 4 P) 2 [Co(E) 4 ] (E = N 3 − , 1; NCO − , 2; NCS − , 3) have been synthesized and structurally characterized. Each compound contains a distorted tetrahedral Co 2+ ion coordinated by four pseudohalide ligands. The magnetic properties of 1–3 have been studied using direct-current magnetic measurements and high-frequency and -field EPR spectroscopy (HFEPR), suggesting easy-axis magnetic anisotropy for 1 and 2 and easy-plane anisotropy for 3. Analysis of the HFEPR spectra yielded D values of −5.23 and +3.63 cm −1 for 2 and 3, respectively. The absence of the EPR signal in 1 is consistent with a large, negative value of the zero-field splitting (ZFS) parameter D in 1. The nature of magnetic anisotropies of 1–3 has also been confirmed by ab initio calculations. The calculated D values are consistent with those determined using magnetometry and HFEPR studies. Alternating current (AC) magnetic susceptibilities reveal slow magnetic relaxation under an applied magnetic field, thus indicating that 1–3 are field-induced single-ion magnets (SIMs). 

Two five-coordinate mononuclear Co( ii ) complexes [Co(12-TMC)X][B(C 6 H 5 ) 4 ] (L = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane (12-TMC), X = Cl − ( 1 ), Br − ( 2 )) have been studied by X-ray single crystallography, magnetic measurements, high-frequency and -field EPR (HF-EPR) spectroscopy and theoretical calculations. Both complexes have a distorted square pyramidal geometry with the Co( ii ) ion lying above the basal plane constrained by the rigid tetradentate macrocyclic ligand. In contrast to the reported five-coordinate Co( ii ) complex [Co(12-TMC)(NCO)][B(C 6 H 5 ) 4 ] ( 3 ) exhibiting easy-axis anisotropy, an easy-plane magnetic anisotropy was found for 1 and 2 via the analyses of the direct-current magnetic data and HF-EPR spectroscopy. Frequency- and temperature-dependent alternating-current magnetic susceptibility measurements demonstrated that complexes 1 and 2 show slow magnetic relaxation at an applied dc field. Ab initio calculations were performed to reveal the impact of the terminal ligands on the nature of the magnetic anisotropies of this series of five-coordinate Co( ii ) complexes. 

Abstract Propylene is a crucial building block to produce many industrial‐scale chemicals including polypropylene. The separation of propylene from propane to reach the high‐purity levels needed for downstream applications is a difficult task due to the close similarities in their physical properties. The olefin/paraffin separation including that involving propylene mainly relies on highly energy‐intensive distillation processes and accounts for nearly 0.3% of the global energy consumption. The utility of a copper complex supported by a fluorinated bis(pyrazolyl)borate is demonstrated to accomplish the separation of propylene from propane repeatedly, under mild conditions with high selectivity. Complete characterization of a rare, copper(I) propylene complex is also reported including the molecular structure. 

Three mononuclear six-coordinate Co( ii )-pseudohalide complexes [Co(L)X 2 ] with two N-donor pseudohalido coligands occupying the cis -positions (X = NCS − ( 1 ), NCSe − ( 2 ) or N(CN) 2 − ( 3 )), and a five-coordinate complex [Co(L)(NCO)][B(C 6 H 5 ) 4 ] ( 4 ) [L = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane (12-TMC)] have been prepared and structurally characterized. Easy-plane magnetic anisotropy for 1–3 and easy-axis anisotropy for 4 were revealed via the analyses of the direct-current magnetic data, high-frequency and -field EPR (HFEPR) spectra and ab initio theoretical calculations. They display slow magnetic relaxations under an external applied dc field. Typically, two slow relaxation processes were found in 1 and 2 while only one relaxation process occurs in 3 and 4 . The Raman-like mechanism is found to be dominant in the studied temperature range in 1 . For 2–4 , the Raman process is dominant in the low temperature region, while the Orbach mechanism dominates in the high temperature range. 

Experimental and theoretical studies of magnetic anisotropy and relaxation behavior of six-coordinate tris(pivalato)-Co( ii ) and -Ni( ii ) complexes (NBu 4 )[M(piv) 3 ] (piv = pivalate, M = Co, 1 ; M = Ni, 2 ), with a coordination configuration at the intermediate between an octahedron and a trigonal prism, are reported. Direct current magnetic data and high-frequency and -field EPR spectra (HFEPR) of 1 have been modeled by a general Hamiltonian considering the first-order orbital angular momentum, while the spin Hamiltonian was used to interpret the data of 2 . Both 1 and 2 show easy-axis magnetic anisotropies, which are further supported by ab initio calculations. Alternating current (ac) magnetic susceptibilities reveal slow magnetic relaxation at an applied dc field of 0.1 T in 1 , which is characteristic of a field-induced single-ion magnet (SIM), but 2 does not exhibit single-ion magnetic properties at 1.8 K. Detailed analyses of relaxation times show a dominant contribution of a Raman process for spin relaxation in 1 . 

Abstract Purification of C₂H₄from an C₂H₄/C₂H₆mixture is one of the most challenging separation processes, which is achieved mainly through energy‐intensive, cryogenic distillation in industry. Sustainable, non‐distillation methods are highly desired as alternatives. We discovered that the fluorinated bis(pyrazolyl)borate ligand supported copper(I) complex {[(CF₃)₂Bp]Cu}₃has features very desirable in an olefin–paraffin separation material. It binds ethylene exclusively over ethane generating [(CF₃)₂Bp]Cu(C₂H₄). This molecular compound exhibits extremely high and record ideal adsorbed solution theory (IAST) C₂H₄/C₂H₆gas separation selectivity, affording high purity (>99.5 %) ethylene that can be readily desorbed from separation columns. In‐situ PXRD provides a “live” picture of the reversible conversion between [(CF₃)₂Bp]Cu(C₂H₄) and the ethylene‐free sorbent in the solid‐state, driven by the presence or removal of C₂H₄. Molecular structures of trinuclear {[(CF₃)₂Bp]Cu}₃and mononuclear [(CF₃)₂Bp]Cu(C₂H₄) are also presented.