Mono- and tetra-nuclear copper complexes bearing bis(imino)phenoxide derived ligands: catalytic evaluation for benzene oxidation and ROP of epsilon-caprolactone

Complexes of the type [Cu(L)2] (1) and [Cu4L2(μ4−O)(OAc)4] (2) have been obtained from the reaction of the phenoxydiimine 1,3-(2,6-R22C6H3N=CH)2-5-R1C6H2OH-2 (LH) (where R1 = Me, tBu, Cl; R2 = Me, iPr) with copper(II) acetate [Cu(OAc)2]; changing the molar ratio of the reactants affords 10 differing amounts of 1 or 2. Reaction of the parent dialdehyde [1,3-(CHO)2-5-MeC6H2OH-2] with [Cu(OAc)2] in the presence of Et3N afforded, following work-up, a polymeric chain (3) comprising {[Cu2(OAc)4]OAc}n, HNEt3 and MeCN. The crystal structures of 1 (R1 = Me, R2 = iPr 1a; R1 = Cl, R2 = iPr 1b), 2 (R1 = Me, R2 = Me 2a; R1 = Me, R2 = iPr 2b; R1 = tBu, R2 = Me 2c; R1 = Cl, R2 = Me 2d; R1 = Cl, R2 = iPr 2e; R1 = tBu, R2 =iPr 2f) and 3 are reported (synchrotron radiation was necessary for 3). The 15 magnetic properties of the cluster 2b are presented. Complexes of type 2 and 3 were screened for the ring opening polymerization (ROP) of ε-caprolactone, with or without benzyl alcohol present, under a variety of conditions, however only trace polymer was isolated. The electrochemistry of all complexes was also investigated, together with their ability to catalyze benzene oxidation (using hydrogen peroxide); although low conversions were observed, the tetra-nuclear complexes exhibited excellent selectivity

Vanadyl sulfates: molecular structure, magnetism and electrochemical activity

Reaction of differing amounts of vanadyl sulfate with p-tert-butylthiacalix[4]areneH4 and base allows access to the vanadyl-sulfate species [NEt4]4[(VO)4(μ3-OH)4(SO4)4]·½H2O (1), [HNEt3]5[(VO)5(μ3-O)4(SO4)4]·4MeCN (2·4MeCN) and [NEt4]2[(VO)6(O)2(SO4)4(OMe)(OH2)]·MeCN (3·MeCN). Similar use of p-tert-butylsulfonylcalix[4]areneH4, p-tert-butylcalix[8]areneH8 or p-tert-butylhexahomotrioxacalix[3]areneH3 led to the isolation of [HNEt3]2[H2NEt2]2{[VO(OMe)]2p-tert-butylcalix[8-SO2]areneH2} (4), [HNEt3]2[V(O)2p-tert-butylcalix[8]areneH5] (5) and [HNEt3]2[VIV2VV4O11(OMe)8] (6), respectively. Dc magnetic susceptibility measurements were performed on powdered microcrystalline samples of 1–3 in the T = 300–2 K temperature range. Preliminary screening for electrochemical water oxidation revealed some activity for 2 with turnover frequency (TOF) and number (TON) of 2.2 × 10−4 s−1 and 6.44 × 10−6 (mmol O2/mmol cat.), respectively. The compound 3 showed an improved electrochemical activity in the presence of water. This is related to the increased number and the rate of electrons exchanged during oxidation of V4+ species, facilitated by protons generated in the water discharge process

Self-Assembly of the Hexabromorhenate(IV) Anion with Protonated Benzotriazoles: X‑ray Structure and Magnetic Properties

Two novel ReIV compounds of formulas [HBTA]2­[ReIVBr6] (1) and [HMEBTA]2­[ReIVBr6] (2) [BTA = 1H-benzotriazole and MEBTA = 1-(methoxy­methyl)-1H-benzotriazole] have been synthesized and magneto-structurally characterized. 1 and 2 crystallize in the triclinic system with space group P1̅. In both compounds, the rhenium ion is six-coordinate, bonded to six bromo ligands in a regular octahedral geometry. Short ReIV–Br···Br–ReIV contacts, π–π stacking, and H-bonding interactions occur in the crystal lattice of both 1 and 2, generating novel supramolecular structures based on the ReIV. The different dispositions of the cations and the intermolecular Br···Br contacts in 1 and 2 play an important structure–property role, with the magnetic properties of 1 and 2 revealing a significant antiferromagnetic coupling between ReIV ions through intermolecular Br···Br interactions. In 1, these interactions account for a maximum in the magnetic susceptibility at ca. 10 K

Self-Assembly of the Hexabromorhenate(IV) Anion with Protonated Benzotriazoles: X‑ray Structure and Magnetic Properties

Two novel Re^IV compounds of formulas [HBTA]₂­[Re^IVBr₆] (<b>1</b>) and [HMEBTA]₂­[Re^IVBr₆] (<b>2</b>) [BTA = 1<i>H</i>-benzotriazole and MEBTA = 1-(methoxy­methyl)-1<i>H</i>-benzotriazole] have been synthesized and magneto-structurally characterized. <b>1</b> and <b>2</b> crystallize in the triclinic system with space group <i>P</i>1̅. In both compounds, the rhenium ion is six-coordinate, bonded to six bromo ligands in a regular octahedral geometry. Short Re^IV–Br···Br–Re^IV contacts, π–π stacking, and H-bonding interactions occur in the crystal lattice of both <b>1</b> and <b>2</b>, generating novel supramolecular structures based on the Re^IV. The different dispositions of the cations and the intermolecular Br···Br contacts in <b>1</b> and <b>2</b> play an important structure–property role, with the magnetic properties of <b>1</b> and <b>2</b> revealing a significant antiferromagnetic coupling between Re^IV ions through intermolecular Br···Br interactions. In <b>1</b>, these interactions account for a maximum in the magnetic susceptibility at ca. 10 K

Strategy for the Rational Design of Asymmetric Triply Bridged Dinuclear 3d-4f Single-Molecule Magnets.

Three triply bridged MII-DyIII dinuclear complexes, [Ni(μ-L)(μ-OAc)Dy(NO3)2] 1, [Zn(μ-L)(μ-OAc)Dy(NO3)2] 2, and [Ni(μ-L)(μ-NO3)Dy(NO3)2]·2CH3OH 3 were prepared with a new and flexible compartmental ligand, N,N′,N″-trimethyl-N,N″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylene triamine (H2L), containing N3O2-inner and O4-outer coordination sites. These complexes have diphenoxo/acetate (1 and 2) or diphenoxo/nitrate (3) asymmetric bridging fragments. Compounds 1 and 3 exhibit ferromagnetic interaction between Ni2+ and Dy3+ ions and frequency dependence of the out-of-phase (χ″M) alternating current (ac) susceptibility signal characteristic of single-molecule-magnet behavior. The energy barriers Δ/kB for compound 3 under zero and 1000 Oe applied direct current (dc) magnetic fields were estimated from the Arrhenius plots to be 7.6 and 19.1 K, respectively

Strategy for the Rational Design of Asymmetric Triply Bridged Dinuclear 3d-4f Single-Molecule Magnets.

Three triply bridged MII-DyIII dinuclear complexes, [Ni(μ-L)(μ-OAc)Dy(NO3)2] 1, [Zn(μ-L)(μ-OAc)Dy(NO3)2] 2, and [Ni(μ-L)(μ-NO3)Dy(NO3)2]·2CH3OH 3 were prepared with a new and flexible compartmental ligand, N,N′,N″-trimethyl-N,N″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylene triamine (H2L), containing N3O2-inner and O4-outer coordination sites. These complexes have diphenoxo/acetate (1 and 2) or diphenoxo/nitrate (3) asymmetric bridging fragments. Compounds 1 and 3 exhibit ferromagnetic interaction between Ni2+ and Dy3+ ions and frequency dependence of the out-of-phase (χ″M) alternating current (ac) susceptibility signal characteristic of single-molecule-magnet behavior. The energy barriers Δ/kB for compound 3 under zero and 1000 Oe applied direct current (dc) magnetic fields were estimated from the Arrhenius plots to be 7.6 and 19.1 K, respectively

Strategy for the Rational Design of Asymmetric Triply Bridged Dinuclear 3d-4f Single-Molecule Magnets.

Three triply bridged MII-DyIII dinuclear complexes, [Ni(μ-L)(μ-OAc)Dy(NO3)2] 1, [Zn(μ-L)(μ-OAc)Dy(NO3)2] 2, and [Ni(μ-L)(μ-NO3)Dy(NO3)2]·2CH3OH 3 were prepared with a new and flexible compartmental ligand, N,N′,N″-trimethyl-N,N″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylene triamine (H2L), containing N3O2-inner and O4-outer coordination sites. These complexes have diphenoxo/acetate (1 and 2) or diphenoxo/nitrate (3) asymmetric bridging fragments. Compounds 1 and 3 exhibit ferromagnetic interaction between Ni2+ and Dy3+ ions and frequency dependence of the out-of-phase (χ″M) alternating current (ac) susceptibility signal characteristic of single-molecule-magnet behavior. The energy barriers Δ/kB for compound 3 under zero and 1000 Oe applied direct current (dc) magnetic fields were estimated from the Arrhenius plots to be 7.6 and 19.1 K, respectively

Strategy for the Rational Design of Asymmetric Triply Bridged Dinuclear 3d-4f Single-Molecule Magnets.

Three triply bridged MII-DyIII dinuclear complexes, [Ni(μ-L)(μ-OAc)Dy(NO3)2] 1, [Zn(μ-L)(μ-OAc)Dy(NO3)2] 2, and [Ni(μ-L)(μ-NO3)Dy(NO3)2]·2CH3OH 3 were prepared with a new and flexible compartmental ligand, N,N′,N″-trimethyl-N,N″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylene triamine (H2L), containing N3O2-inner and O4-outer coordination sites. These complexes have diphenoxo/acetate (1 and 2) or diphenoxo/nitrate (3) asymmetric bridging fragments. Compounds 1 and 3 exhibit ferromagnetic interaction between Ni2+ and Dy3+ ions and frequency dependence of the out-of-phase (χ″M) alternating current (ac) susceptibility signal characteristic of single-molecule-magnet behavior. The energy barriers Δ/kB for compound 3 under zero and 1000 Oe applied direct current (dc) magnetic fields were estimated from the Arrhenius plots to be 7.6 and 19.1 K, respectively

New Routes to High Nuclearity Clusters: Fluoride-Based Octametallic and Tridecametallic Clusters of Manganese

The reaction of MnF3 with 5,6-dimethylbenzotriazole (Me2BTAH) gives the [MnIII8] complex [Mn8O4(OMe)2(Me2BTA)6F8(Me2BTAH)(MeOH)8] and the [MnIV3MnIII10] complex [Mn13O12(Me2BTA)12F6(MeOH)10(H2O)2]. The octametallic species is an “intermediate” in the formation of the tridecametallic cluster

Effect of Protonated Organic Cations and Anion−π Interactions on the Magnetic Behavior of Hexabromorhenate(IV) Salts

Two novel Re^IV compounds of formula (Hbpym)₂[Re^IVBr₆]·4H₂O (<b>1</b>) and (H₄biim)­[Re^IVBr₆]·4H₂O (<b>2</b>) [Hbpym⁺ = 2,2′-bipyrimidinium cation and H₄biim²⁺ = 2,2′-biimidazolium dication] have been prepared and magnetostructurally characterized. <b>1</b> and <b>2</b> exhibit distinct crystal packing, and the presence of weak intermolecular contacts, such as Re–Br···Br–Re (<b>1</b> and <b>2</b>), Re–Br···(H₂O)···Br–Re (<b>1</b> and <b>2</b>), and Re–Br···π···Br–Re (<b>2</b>), lead to different magnetic behaviors. While <b>1</b> is antiferromagnetic, <b>2</b> is a ferromagnetic compound and indeed the first example of ferromagnetic salt based on the hexabromorhenate­(IV) anion. These results suggest a straightforward synthetic route to the preparation of new ferromagnetically coupled Re^IV compounds