Pressure induced enhancement of the magnetic ordering temperature in rhenium(IV) monomers.

Materials that demonstrate long-range magnetic order are synonymous with information storage and the electronics industry, with the phenomenon commonly associated with metals, metal alloys or metal oxides and sulfides. A lesser known family of magnetically ordered complexes are the monometallic compounds of highly anisotropic d-block transition metals; the 'transformation' from isolated zero-dimensional molecule to ordered, spin-canted, three-dimensional lattice being the result of through-space interactions arising from the combination of large magnetic anisotropy and spin-delocalization from metal to ligand which induces important intermolecular contacts. Here we report the effect of pressure on two such mononuclear rhenium(IV) compounds that exhibit long-range magnetic order under ambient conditions via a spin canting mechanism, with T controlled by the strength of the intermolecular interactions.

A Chiral, Photoluminescent, and Spin-Canted {Cu(I)Re(IV)2}n Branched Chain.

A new heteroleptic 1D Cu(I)-Re(IV) coordination polymer of the formula {Cu(I)Re(IV)Cl4(μ-Cl)(μ-pyz)[Re(IV)Cl4(μ-bpym)]}n·nMeNO2 (1; pyz = pyrazine, bpym = 2,2'-bipyrimidine) has been prepared through the Cu(I)-mediated self-assembly of two different Re(IV) metalloligands, namely, [ReCl5(pyz)](-) and [ReCl4(bpym)]. 1 consists of chiral branched chains with an overall rack-type architecture displaying photoemission and magnetic ordering. These results constitute a first step toward making new multifunctional magnetic materials based on mixed 3d-5d molecular systems.

Metamagnetic behaviour in a new Cu(II)Re(IV) chain based on the hexachlororhenate(IV) anion.

A new chloro-bridged heterobimetallic Cu(II)Re(IV) chain of formula {Cu(pyim)(Him)2ReCl6}n·MeCN (·MeCN) has been prepared and magnetostructurally characterised. Compound is the first example of the [Re(IV)Cl6](2-) anion acting as a metalloligand towards a paramagnetic metal ion.

Highly anisotropic rhenium(IV) complexes: new examples of mononuclear single-molecule magnets.

The rhenium(IV) complex (NBu4)2[ReBr4(ox)] (1) (ox = oxalate and NBu4(+) = tetra-n-butylammonium cation) has been prepared and its crystal structure determined by X-ray diffraction. The structure is made up of discrete [ReBr4(ox)](2-) anions and bulky NBu4(+) cations. Each [ReBr4(ox)](2-) anion is surrounded by six NBu4(+) cations, which preclude any significant intermolecular contact between the anionic entities, the shortest rhenium···rhenium distance being 9.

Ferromagnetic coupling and spin canting behaviour in heterobimetallic Re(IV)M(II/III) (M = Co(II/III), Ni(II)) species.

Three novel heterobimetallic Re(IV) compounds of formulae [ReBr(4)(μ-ox)M(4,7-Cl(2)phen)(2)]·CH(3)CN·CH(3)NO(2) [M = Co(II) (1) and Ni(II) (2)] and [ReBr(4)(ox)](3)[Co(III)(5,6-dmphen)(3)](2)·CH(3)CN·2CH(3)NO(2)·4H(2)O (3) [ox = oxalate, 4,7-Cl(2)phen = 4,7-dichloro-1,10-phenanthroline and 5,6-dmphen = 5,6-dimethyl-1,10-phenanthroline] have been synthesised and the structures of 1 and 3 determined by single crystal X-ray diffraction. Compound 1 is an oxalato-bridged Re(IV)Co(II) heterodinuclear complex where the [ReBr(4)(ox)](2-) unit acts as a bidentate ligand towards the [Co(4,7-Cl(2)phen)(2)](2+) entity, the separation between Re(IV) and Co(II) across the oxalate being 5.482(1) Å.

A heteropentanuclear oxalato-bridged [Re(IV)4Gd(III)] complex: synthesis, crystal structure and magnetic properties.

The compound (NBu(4))(5)[Gd(III){Re(IV)Br(4)(μ-ox)}(4)(H(2)O)]·H(2)O (1), with intramolecular antiferromagnetic coupling, is the first Re(iv) system incorporating a 4f ion.

New family of thiocyanate-bridged Re(IV)-SCN-M(II) (M = Ni, Co, Fe, and Mn) heterobimetallic compounds: synthesis, crystal structure, and magnetic properties.

The heterobimetallic complexes of formula [(Me(2)phen)(2)M(μ-NCS)Re(NCS)(5)]·CH(3)CN [Me(2)phen = 2,9-dimethyl-1,10-phenanthroline and M = Ni (1), Co (2), Fe (3), and Mn (4)] have been prepared, and their crystal structures have been determined by X-ray diffraction on single crystals. Compounds 1-4 crystallize in the monoclinic C2/c space group, and their structure consists of neutral [(Me(2)phen)(2)M(μ-NCS)Re(NCS)(5)] heterodinuclear units with a Re-SCN-M bridge. Each Re(IV) ion in this series is six-coordinated with one sulfur and five nitrogen atoms from six thiocyanate groups building a somewhat distorted octahedral environment, whereas the M(II) metal ions are five-coordinated with four nitrogen atoms from two bidentate Me(2)phen molecules and a nitrogen atom from the bridging thiocyanate describing distorted trigonal bipyramidal surroundings.

First magnetostructural study on a heterodinuclear 2,2'-bipyrimidine-bridged complex.

The use of the [ReCl(4)(bpym)] precursor as a ligand toward the fully solvated nickel(II) metal ion affords the first example of a 2,2'-bipyrimidine-bridged Re(IV)-Ni(II) complex, [ReCl(4)(μ-bpym)NiBr(2)(H(2)O)(2)] (1), whose intramolecular ferromagnetic coupling has been substantiated from both experimental and theoretical studies.

Enhancing the magnetic coupling of oxalato-bridged Re(IV)2M(II) (M=Mn, Co, Ni, and Cu) trinuclear complexes via peripheral halide ligand effects.

Four heterotrinuclear Re(IV)(2)M(II) compounds of general formula (NBu(4))(2)[{Re(IV)Br(4)(μ-ox)}(2)M(II)(Him)(2)] [NBu(4)(+) = tetra-n-butylammonium cation, ox = oxalate, Him = imidazole; M = Mn (1), Co (2), Ni (3), and Cu (4)] have been synthesized by using the novel mononuclear complex [Re(IV)Br(4)(ox)](2-) as a ligand toward divalent first-row transition metal ions in the presence of imidazole. Compounds 1-4 are isostructural complexes whose structure contains discrete trinuclear [{Re(IV)Br(4)(μ-ox)}(2)M(II)(Him)(2)](2-) anions and bulky NBu(4)(+) cations. The Re and M atoms are six-coordinated: four peripheral bromo and two oxalate-oxygens (at Re), and two cis-coordinated imidazole molecules and four oxygen atoms from two oxalate ligands (at M), build distorted octahedral surroundings.

New cyanide-bridged Mn(III)-M(III) heterometallic dinuclear complexes constructed from [M(III)(AA)(CN)4]- building blocks (M = Cr and Fe): synthesis, crystal structures and magnetic properties.

Three Mn(III)-M(III) (M = Cr and Fe) dinuclear complexes have been obtained by assembling [Mn(III)(SB)(H(2)O)](+) and [M(III)(AA)(CN)(4)](-) ions, where SB is the dianion of the Schiff-base resulting from the condensation of 3-methoxysalicylaldehyde with ethylenediamine (3-MeOsalen(2-)) or 1,2-cyclohexanediamine (3-MeOsalcyen(2-)): [Mn(3-MeOsalen)(H(2)O)(µ-NC)Cr(bipy)(CN)(3)]·2H(2)O (1), [Mn(3-MeOsalen)(H(2)O)(µ-NC)Cr(ampy)(CN)(3)][Mn(3-MeOsalen)(H(2)O)(2)]ClO(4)·2H(2)O (2) and [Mn(3-MeOsalcyen)(H(2)O)(µ-NC)Fe(bpym)(CN)(3)]·3H(2)O (3) (bipy = 2,2'-bipyridine, ampy = 2-aminomethylpyridine and bpym = 2,2'-bipyrimidine). The [M(AA)(CN)(4)](-) unit in 1-3 acts as a monodentate ligand towards the manganese(III) ion through one of its four cyanide groups. The manganese(III) ion in 1-3 exhibits an elongated octahedral stereochemistry with the tetradentate SB building the equatorial plane and a water molecule and a cyanide-nitrogen atom filling the axial positions.

Synthesis, crystal structure and magnetic properties of an oxalato-bridged Re(IV)Mo(VI) heterobimetallic complex.

The Re(IV)-Mo(VI) compound of formula (PPh(4))(2)[ReCl(4)(μ-ox)MoO(2)Cl(2)] (1) constitutes the first example of a heterodinuclear oxalato-bridged complex in the coordination chemistry of molybdenum.

Magneto-structural studies on heterobimetallic malonate-bridged M(II)Re(IV) complexes (M = Mn, Co, Ni and Cu).

The mononuclear Re(IV) compound of formula (PPh(4))(2)[ReBr(4)(mal)] (1) was used as a ligand to obtain the heterobimetallic species [ReBr(4)(μ-mal)Co(dmphen)(2)]· MeCN (2), [ReBr(4)(μ-mal)Ni(dmphen)(2)] (3), [ReBr(4)(μ-mal)Mn(dmphen)(2)] (4a), [ReBr(4)(μ-mal)Mn(dmphen)(H(2)O)(2)]·dmphen·MeCN·H(2)O (4b), [ReBr(4)(μ-mal)Cu(phen)(2)]·1/4H(2)O (5) and [ReBr(4)(μ-mal)Cu(bipy)(2)] (6) (mal = malonate dianion, dmphen = 2,9-dimethyl-1,10-phenanthroline, phen = 1,10-phenanthroline and bipy = 2,2'-bipyridine). The structures of 2 and 5 (single-crystal X-ray diffraction) are made up of neutral [ReBr(4)(μ-mal)M(AA)] dinuclear units [AA = dmphen with M = Co (2) and AA = phen with M = Cu (5)] where the metal ions are connected through a malonate ligand which exhibits simultaneously the bidentate [at the Re(IV)] and monodentate [at the M(II)] coordination modes. The carboxylate-malonate group in them adopts the anti-syn conformation with intramolecular ReM separation of 5.

Heterotetranuclear oxalato-bridged Re(IV)3M(II) (M = Mn, Fe, Co, Ni, Cu) complexes: a new example of a single-molecule magnet (M = Ni).

The use of the mononuclear species (NBu(4))(2)[Re(IV)Cl(4)(ox)] (NBu(4)(+) = tetra-n-butylammonium cation; ox = oxalate dianion) as a ligand toward fully solvated divalent first-row transition-metal ions affords the tetranuclear complexes (NBu(4))(4)[{Re(IV)Cl(4)(mu-ox)}(3)M(II)] with M = Mn (1), Fe (2), Co (3), Ni (4), and Cu (5). Their structure is made up of discrete [{ReCl(4)(mu-ox)}(3)M](4-) anions and bulky NBu(4)(+) cations. The complexes 2-5 crystallize in the triclinic system with space group P1; 2 and 5 as well as 3 and 4 are isostructural.

Pentachloro(pyrazine)rhenate(IV) complex as precursor of heterobimetallic pyrazine-containing Re(IV)2M(II) (M = Ni, Cu) species: synthesis, crystal structures and magnetic properties.

Three novel Re(IV) mononuclear complexes of formulae NBu4[ReC15(pyz)] (1), NH2Me2[ReCl5(pyz)] (2) and NH4[ReCl5(pyz)].0.75H2O (3), (pyz being pyrazine; NBu4+ = tetra-n-butylammonium cation, NH2Me2+ = dimethylammonium cation and NH4+ = ammonium cation), were synthesized by ligand substitution reaction from [ReCl6]2- anion and pyrazine in N,N-dimethylformamide (DMF).

X-ray structure of [ReCl4(mu-ox)Cu(pyim)2]: a new heterobimetallic Re(IV)Cu(II) ferrimagnetic chain.

A new heterobimetallic Re(IV)Cu(II) compound has been prepared and its crystal structure determined by single-crystal X-ray diffraction; magnetic susceptibility measurements show that this compound behaves as a ferrimagnetic chain with significant antiferromagnetic interactions between Re(IV) and Cu(II) metal ions.

Synthesis, crystal structure and magnetic properties of novel heterobimetallic malonate-bridged MIIReIV complexes (M = Mn, Fe, Co and Ni).

Five novel ReIV-MII bimetallic complexes of formula [ReCl4(mu-mal)M(dmphen)2].MeCN [M = Co (1), Fe (2) and Ni (3)], [ReCl4(mu-mal)Ni(dmphen)(MeCN)2(H2O)].(MeCN)0.

Heterotrimetallic oxalato-bridged ReIV2MII complexes (M=Mn, Co, Ni, Cu): synthesis, crystal structure, and magnetic properties.

The use of the (NBu4)2[ReIVCl4(ox)] mononuclear species as a ligand toward divalent first row transition metal ions in the presence of imidazole affords the new trinuclear compounds of formula (NBu4)2[{ReIVCl4(mu-ox)}2MII(Him)2] [NBu4+=tetra-n-butylammonium cation, ox=oxalate dianion, Him=imidazole; M=Mn (1), Co (2), Ni (3), Cu (4)] whose preparation, crystal structures, and magnetic properties are reported. 1-4 are isostructural complexes which are made up of discrete trinuclear [{ReIVCl4(mu-ox)}2MII(Him)2]2- anions and bulky NBu4+ cations. The Re and M atoms exhibit somewhat distorted octahedral surroundings which are built by four chloro and two oxalate oxygens (Re) and two imidazole nitrogen and four oxalate oxygen atoms (M), the central M atom being linked to the two peripheral Re atoms through bis-bidentate oxalate.

A novel series of rhenium-bipyrimidine complexes: synthesis, crystal structure and electrochemical properties.

Four novel rhenium complexes of formula [ReCl(4)(bpym)] (1), [ReBr(4)(bpym)] (2) PPh(4)[ReCl(4)(bpym)] (3) and NBu(4)[ReBr(4)(bpym)] (4) (bpym = 2,2'-bipyrimidine, PPh(4) = tetraphenylphosphonium cation and NBu(4) = tetrabutylammonium cation), have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. The structures of 1 and 2 consist of [ReX(4)(bpym)] molecules held together by van der Waals forces. In both complexes the Re(iv) central atom is surrounded by four halide anions and two nitrogen atoms of a bpym bidentate ligand in a distorted octahedral environment.

Magnetic properties and molecular structures of binuclear (2-pyrazinecarboxylate)-bridged complexes containing Re(IV) and M(II) (M = Co, Ni).

Three novel Re(iv) compounds, the mononuclear complex Bu(4)N[ReBr(5)(Hpyzc)] (1) and the heterobimetallic complexes [ReBr(5)(mu-pyzc)M(dmphen)(2)].2CH(3)CN [M = Co (2), Ni (3)] (Hpyzc = 2-pyrazinecarboxylic acid, dmphen = 2,9-dimethyl-1,10-phenanthroline), have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. The structure of 1 consists of [ReBr(5)(Hpyzc)](-) complex anions and tetrabutylammonium cations, Bu(4)N(+).

Ligand design for heterobimetallic single-chain magnets: synthesis, crystal structures, and magnetic properties of MIICuII (M=Mn, Co) chains with sterically hindered methyl-substituted phenyloxamate bridging ligands.

Two new series of neutral oxamato-bridged heterobimetallic chains of general formula [MCu(L(x))(2)] m DMSO (m=0-4) (L(1)=N-2-methylphenyloxamate, M=Mn (1 a) and Co (1 b); L(2)=N-2,6-dimethylphenyloxamate, M=Mn (2 a) and Co (2 b); L(3)=N-2,4,6-trimethylphenyloxamate, M=Mn (3 a) and Co (3 b)) have been prepared by reaction between the corresponding anionic oxamatocopper(II) complexes [Cu(Lx)2](2-) with Mn(2+) or Co(2+) cations in DMSO. The crystal structures of [CoCu(L2)2(H2O)2] (2 b') and [CoCu(L3)2(H2O)2]4 H2O (3 b') have been solved by single-crystal X-ray diffraction methods. Compounds 2 b' and 3 b' adopt zigzag and linear chain structures, respectively.

A Heterotetranuclear [NiIIReIV3] single-molecule magnet.

The reaction of [ReIVCl4(ox)]2- and fully solvated Ni2+ ions in a MeCN/i-PrOH mixture affords the heterotetranuclear complex (NBu4)4[Ni{ReCl4(ox)}3] where the rhenium precursor acts as a bidentate ligand toward the nicke(II) ion through the oxalate group. The mixed 3d-5d species exhibits intramolecular ferromagnetic coupling and it behaves like a single-molecule magnet.

Rhenium(IV)-copper(II) heterobimetallic complexes with a bridge malonato ligand. Synthesis, crystal structure, and magnetic properties.

The Re(IV) complex [ReCl4(mal)]2-, in the form of two slightly different salts, (AsPh4)1.5(HNEt3)0.5[ReCl4(mal)] (1a) and (AsPh4)(HNEt3)[ReCl4(mal)] (1b), and the Re(IV)-Cu(II) bimetallic complexes [ReCl4(mu-mal)Cu(phen)2].

Magnetic studies on hexahalorhenate(IV) salts of ferrocenium cations [Fe(C5R5)2]2[ReX6] (R = H, CH3; X = Cl, Br, I).

The hexahalorhenate(IV) salts of formula [Fe(C5H5)2]2[ReX6], with X = Cl (1), Br (2), and I (3), and [Fe(C5Me5)2]2[ReX6], with X = Cl (4), Br (5), and I (6) ([Fe(C5Me5)2]+ = decamethylferrocenium cation), have been synthesized and the structures of 1, 2, and 4 determined by single-crystal X-ray diffraction. 1, 2, and 4 crystallize in the orthorhombic system, space groups Pbca (1 and 2) and Ibam (4), with a = 14.099(2) A, b = 16.

Long-range magnetic coupling through extended pi-conjugated aromatic bridges in dinuclear copper(II) metallacyclophanes.

Self-assembly of 1,4-phenylenebis(oxamate) and 4,4'-biphenylenebis(oxamate) ligands and Cu2+ ions gives two new dinuclear copper(II) metallacyclophanes where the two metal centers are connected by double para-substituted aromatic diamide bridges. Despite the relatively large intramolecular Cu-Cu distance of ca. 8 and 12 A for each complex, magnetic susceptibility measurements evidence strong to moderately strong intramolecular antiferromagnetic couplings (-J values of the order of 100 and 10 cm-1, respectively).

Magnetic studies on hexaiodorhenate(IV) salts of univalent cations. Spin canting and magnetic ordering in K2[ReI6] with Tc = 24 K.

The ionic salts of rhenium(IV) of formula (Cat)(2)[ReI(6)] with Cat = Li(+) (1), Na(+) (2), K(+) (3), Rb(+) (4), Cs(+) (5), NH(4)(+) (6), and AsPh(4)(+) (7) [AsPh(4)(+) = tetraphenylarsonium cation] have been synthesized, and the structures of two of them (namely, 3 and 6) were determined by single-crystal X-ray diffraction. 3 crystallizes in the monoclinic system, space group Pn, with a = 7.815(1) A, b = 7.