Synthesis, structure, and magnetic properties of three 1D chain complexes based on high-spin metal-cyanide clusters: [Mn(III)6M(III)] (M = Cr, Fe, Co)

On the basis of high-spin metal-cyanide clusters of Mn(III)(6)M(III) (M = Cr, Fe, Co), three one-dimensional (1D) chain complexes, [Mn(salen)](6)[Cr(CN)(6)](2)·6CH(3)OH·H(2)O (1), [Mn(5-CH(3))salen)](6)[Fe(CN)(6)](2)·2CH(3)CN·10H(2)O (2), and [Mn(5-CH(3))salen)](6)[Co(CN)(6)](2)·2CH(3)CN·10H(2)O (3) [salen = N,N'-ethylenebis(salicylideneiminato) dianion], have been synthesized and characterized structurally as well as magnetically. Complexes 2 and 3 are isomorphic but slightly different from complex 1. All three complexes contain a 1D chain structure which is comprised of alternating high-spin metal-cyanide clusters of [Mn(6)M](3+) and a bridging group [M(CN)(6)](3-) in the trans mode. Furthermore, the three complexes all exhibit extended 3D supramolecular networks originating from short intermolecular contacts. Magnetic investigation indicates that the coupling mechanisms are intrachain antiferromagnetic interactions for 1 and ferromagnetic interactions for 2, respectively. Complex 3 is a magnetic dilute system due to the diamagnetic nature of Co(III). Further magnetic investigations show that complexes 1 and 2 are dominated by the 3D antiferromagnetic ordering with T(N) = 7.2 K for 1 and 9.5 K for 2. It is worth noting that the weak frequency-dependent phenomenon of AC susceptibilities was observed in the low-temperature region in both 1 and 2, suggesting the presence of slow magnetic relaxations.     

Hydrogencyanamide-bridged one-dimensional polymers built on Mn(III)-Schiff base fragments: synthesis, structure, and magnetism

The ability of NCNH(-) to construct transition metal coordination polymers and to transmit magnetic coupling was investigated. By introduction of various tetradentate Schiff base ligands (L) and different solvents (S), nine NCNH(-)-bridged manganese(III) coordination complexes were obtained. Their structures can be divided into three types: I) NCNH-bridged chains built on mononuclear [Mn(III)(L)] units, [Mn(III)(L)(mu(1,3)-NCNH)](n) (L=5-Brsalen (1), 5-Clsalen (2)); II) NCNH-bridged chains built on dinuclear [Mn(III) (2)(L)(2)] units, complexes 3-8, [Mn(III) (2)(L)(2)(mu(1,3)-NCNH)]ClO(4)S (L=salen, 5-Fsalen, 5-Clsalen, 5-OCH(3)salen; S=CH(3)OH or C(2)H(5)OH); III) NCNH-bridged Mn(III) dimers linked by hydrogen bonds into a 1D polymer, {[Mn(III)(3-OCH(3)salen)(H(2)O)](2)(mu(1,3)-NCNH)}ClO(4) x 0.5 H(2)O (9, salen=N,N'-bis(salicylidene)-1,2-diaminoethane). In these complexes, the N[triple chemical bond]C--NH(-) resonance structure dominates the bonding mode of the NCNH(-) ligand adopting the mu(1,3)-bridging mode. Magnetic characterization shows that the asymmetric NCNH(-) bridge transmits antiferromagnetic interaction between Mn(III) ions and often favors the weak ferromagnetism caused by spin canting in these one-dimensional chains. However, these complexes exhibit different magnetic behaviors at low temperatures.     

Cyanide-bridged Mn(III)-Fe(III) bimetallic complexes based on the pentacyano(1-methylimidazole)ferrate(III) building block: structure and magnetic characterizations

Seven cyanide-bridged bimetallic complexes have been synthesized by the reaction of [Fe(1-CH3im)(CN)5]2- with Mn(III) Schiff base complexes. Their crystal structure and magnetic properties have been characterized. Five complexes, [Mn2(5-Brsalen)2Fe(CN)5(1-CH3im)] x H2O (1), [Mn2(5-Clsalen)2(H2O)2Fe(CN)5(1-CH3im)] x H2O (2), [Mn2(5-Clsaltn)2(H2O)2Fe(CN)5(1-CH3im)] (3), [Mn2(5-Clsaltmen)2(H2O)2Fe(CN)5(1-CH3im)] x H2O (4), and [Mn2(5-Brsaltmen)2(H2O)2Fe(CN)5(1-CH3im)] x CH3OH (5), are neutral and trinuclear with two [Mn(SB)]+ (SB2- = Schiff base ligands) and one [Fe(1-CH3im)(CN)5]2-. Complex {[Et4N][Mn(acacen)Fe(CN)5(1-CH3im)]}n x 6nH2O (6) is one-dimensional with alternate [Mn(acacen)]+ and [Fe(CN)5(1-CH3im)]2- units. The two-dimensional complex {[Mn4(saltmen)4Fe(CN)5(1-CH3im)]}n[ClO4]2n x 9nH2O (7) consists of Mn4Fe units which are further connected by the phenoxo oxygen atoms. Magnetic studies show the presence of ferromagnetic Mn(III)-Fe(III) coupling in the trinuclear compounds with the magnetic coupling constant (J) ranging from 4.5 to 6.0 cm-1, based on the Hamiltonian H = -2JSFe(SMn(1) + SMn(2)). Antiferromagnetic interaction has been observed in complex 6, whereas ferromagnetic coupling occurs in complex 7. Complexes 6 and 7 exhibit long-range magnetic ordering with a TN value of 4.0 K for 6 and Tc of 4.8 K for 7. Complex 6 shows metamagnetic behavior at 2 K, and complex 7 possesses a hysteresis loop with a coercive field of 500 Oe, typical of a soft ferromagnet.     

2-Aminoisobutyric acid in Co(II) and Co(II)/Ln(III) chemistry: homometallic and heterometallic clusters

The synthesis and magnetic properties of 13 new homo- and heterometallic Co(II) complexes containing the artificial amino acid 2-amino-isobutyric acid, aibH, are reported: [Co(II)(4)(aib)(3)(aibH)(3)(NO(3))](NO(3))(4)·2.8CH(3)OH·0.2H(2)O (1·2.8CH(3)OH·0.2H(2)O), {Na(2)[Co(II)(2)(aib)(2)(N(3))(4)(CH(3)OH)(4)]}(n) (2), [Co(II)(6)La(III)(aib)(6)(OH)(3)(NO(3))(2)(H(2)O)(4)(CH(3)CN)(2)]·0.5[La(NO(3))(6)]·0.75(ClO(4))·1.75(NO(3))·3.2CH(3)CN·5.9H(2)O (3·3.2CH(3)CN·5.9H(2)O), [Co(II)(6)Pr(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Pr(NO(3))(5)]·0.41[Pr(NO(3))(3)(ClO(4))(0.5)(H(2)O)(1.5)]·0.59[Co(NO(3))(3)(H(2)O)]·0.2(ClO(4))·0.25H(2)O (4·0.25H(2)O), [Co(II)(6)Nd(III)(aib)(6)(OH)(3)(NO(3))(2.8)(CH(3)OH)(4.7)(H(2)O)(1.5)]·2.7(ClO(4))·0.5(NO(3))·2.26CH(3)OH·0.24H(2)O (5·2.26CH(3)OH·0.24H(2)O), [Co(II)(6)Sm(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Sm(NO(3))(5)]·0.44[Sm(NO(3))(3)(ClO(4))(0.5)(H(2)O)(1.5)]·0.56[Co(NO(3))(3)(H(2)O)]·0.22(ClO(4))·0.3H(2)O (6·0.3H(2)O), [Co(II)(6)Eu(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)OH)(4.87)(H(2)O)(1.13)](ClO(4))(2.5)(NO(3))(0.5)·2.43CH(3)OH·0.92H(2)O (7·2.43CH(3)OH·0.92H(2)O), [Co(II)(6)Gd(III)(aib)(6)(OH)(3)(NO(3))(2.9)(CH(3)OH)(4.9)(H(2)O)(1.2)]·2.6(ClO(4))·0.5(NO(3))·2.58CH(3)OH·0.47H(2)O (8·2.58CH(3)OH·0.47H(2)O), [Co(II)(6)Tb(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Tb(NO(3))(5)]·0.034[Tb(NO(3))(3)(ClO(4))(0.5)(H(2)O)(0.5)]·0.656[Co(NO(3))(3)(H(2)O)]·0.343(ClO(4))·0.3H(2)O (9·0.3H(2)O), [Co(II)(6)Dy(III)(aib)(6)(OH)(3)(NO(3))(2.9)(CH(3)OH)(4.92)(H(2)O)(1.18)](ClO(4))(2.6)(NO(3))(0.5)·2.5CH(3)OH·0.5H(2)O (10·2.5CH(3)OH·0.5H(2)O), [Co(II)(6)Ho(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·0.27[Ho(NO(3))(3)(ClO(4))(0.35)(H(2)O)(0.15)]·0.656[Co(NO(3))(3)(H(2)O)]·0.171(ClO(4)) (11), [Co(II)(6)Er(III)(aib)(6)(OH)(4)(NO(3))(2)(CH(3)CN)(2.5)(H(2)O)(3.5)](ClO(4))(3)·CH(3)CN·0.75H(2)O (12·CH(3)CN·0.75H(2)O), and [Co(II)(6)Tm(III)(aib)(6)(OH)(3)(NO(3))(3)(H(2)O)(6)]·1.48(ClO(4))·1.52(NO(3))·3H(2)O (13·3H(2)O). Complex 1 describes a distorted tetrahedral metallic cluster, while complex 2 can be considered to be a 2-D coordination polymer. Complexes 3-13 can all be regarded as metallo-cryptand encapsulated lanthanides in which the central lanthanide ion is captivated within a [Co(II)(6)] trigonal prism. dc and ac magnetic susceptibility studies have been carried out in the 2-300 K range for complexes 1, 3, 5, 7, 8, 10, 12, and 13, revealing the possibility of single molecule magnetism behavior for complex 10.     

Two novel cyanide-bridged bimetallic magnetic chains derived from manganese(III) Schiff bases and hexacyanochromate(III) building blocks

Two novel complexes, [{Mn(salen)}(2){Mn(salen)(CH(3)OH)}{Cr(CN)(6)}](n)·2nCH(3)CN·nCH(3)OH (1) and [Mn(5-Clsalmen)(CH(3)OH)(H(2)O)](2n)[{Mn(5-Clsalmen)(μ-CN)}Cr(CN)(5)](n)·5.5nH(2)O (2) (salen(2-) = N,N'-ethylene-bis(salicylideneiminato) dianion; 5-Clsalmen(2-) = N,N'-(1-methylethylene)-bis(5-chlorosalicylideneiminato) dianion), were synthesized and structurally characterized by X-ray single-crystal diffraction. The structural analyses show that complex 1 consists of one-dimensional (1D) alternating chains formed by the [{Cr(CN)(6)}{Mn(salen)}(4){Mn(salen)(CH(3)OH)}(2)](3+) heptanuclear cations and [Cr(CN)(6)](3-) anions. While in complex 2, the hexacyanochromate(III) anion acts as a bis-monodentate ligand through two trans-cyano groups to bridge two [Mn(5-Clsalmen)](+) cations to form a straight chain. The magnetic analysis indicates that complex 1 shows three-dimensional (3D) antiferromagnetic ordering with the Ne?el temperature of 5.0 K, and it is a metamagnet displaying antiferromagnetic to ferromagnetic transition at a critical field of about 2.6 kOe at 2 K. Complex 2 behaves as a molecular magnet with Tc = 3.0 K.     

Syntheses, crystal structures, and magnetic characterization of five new dimeric manganese(III) tetradentate Schiff base complexes exhibiting single-molecule-magnet behavior

Tetradentate Schiff base ligands H2L (H2saltmen, H2salen, H2-5-Brsalen, and H2-3,5-Brsalen), derived from the condensation of the corresponding salicylaldehyde or its derivatives with 1,1,2,2-tetramethylethyldiamine or 1, 2-diaminoethane, reacted with Mn(III) acetate or perchlorate salts and sodium azide or sodium cyanate to produce five Mn(III) dimer complexes, [Mn(saltmen)(O2CCH3)]2.2CH3CO2H (1), [Mn(saltmen)(N3)]2 (2), [Mn(salen)(NCO)]2 (3), [Mn(3,5-Brsalen)(3,5-Brsalicylaldehyde)]2 (4), and [Mn(5-Brsalen)(CH3OH)]2(ClO4)2 (5). These new complexes have been characterized by IR, elemental analyses, crystal structural analyses, and magnetic studies. Within these Mn(III) dimeric complexes, two Mn(III) ions are connected by phenolate oxygen atoms with acetate, azide, cyanate, a 3,5-Brsalicyladehyde anion, and a neutral methanol molecule as the axial ligands for complexes 1-5, respectively. Complexes 1-4 exhibit intradimer ferromagnetic exchange and display frequency dependence of ac magnetic susceptibility, possibly showing single-molecule-magnet (SMM) behavior. In contrast, complex 5 shows an intradimer antiferromagnetic coupling probably originating from the relatively shorter Mn-O distance, compared to those of complexes 1-4.     

Syntheses, structures, and magnetic properties of a family of tetra-, hexa-, and nonanuclear Mn/Ni heterometallic clusters

A family of Mn(III)/Ni(II) heterometallic clusters, [Mn(III)(4)Ni(II)(5)(OH)(4)(hmcH)(4)(pao)(8)Cl(2)]·5DMF (1·5DMF), [Mn(III)(3)Ni(II)(6)(N(3))(2)(pao)(10)(hmcH)(2)(OH)(4)]Br·2MeOH·9H(2)O (2·2MeOH·9H(2)O), [Mn(III)Ni(II)(5)(N(3))(4)(pao)(6)(paoH)(2)(OH)(2)](ClO(4))·MeOH·3H(2)O (3·MeOH·3H(2)O), and [Mn(III)(2)Ni(II)(2)(hmcH)(2)(pao)(4)(OMe)(2)(MeOH)(2)]·2H(2)O·6MeOH (4·2H(2)O·6MeOH) [paoH = pyridine-2-aldoxime, hmcH(3) = 2, 6-Bis(hydroxymethyl)-p-cresol], has been prepared by reactions of Mn(II) salts with [Ni(paoH)(2)Cl(2)], hmcH(3), and NEt(3) in the presence or absence of NaN(3) and characterized. Complex 1 has a Mn(III)(4)Ni(II)(5) topology which can be described as two corner-sharing [Mn(2)Ni(2)O(2)] butterfly units bridged to an outer Mn atom and a Ni atom through alkoxide groups. Complex 2 has a Mn(III)(3)Ni(II)(6) topology that is similar to that of 1 but with two corner-sharing [Mn(2)Ni(2)O(2)] units of 1 replaced with [Mn(3)NiO(2)] and [MnNi(3)O(2)] units as well as the outer Mn atom of 1 substituted by a Ni atom. 1 and 2 represent the largest 3d heterometal/oxime clusters and the biggest Mn(III)Ni(II) clusters discovered to date. Complex 3 possesses a [MnNi(5)(μ-N(3))(2)(μ-OH)(2)](9+) core, whose topology is observed for the first time in a discrete molecule. Careful examination of the structures of 1-3 indicates that the Mn/Ni ratios of the complexes are likely associated with the presence of the different coligands hmcH(2-) and/or N(3)(-). Complex 4 has a Mn(III)(2)Ni(II)(2) defective double-cubane topology. Variable-temperature, solid-state dc and ac magnetization studies were carried out on complexes 1-4. Fitting of the obtained M/(Nμ(B)) vs H/T data gave S = 5, g = 1.94, and D = -0.38 cm(-1) for 1 and S = 3, g = 2.05, and D = -0.86 cm(-1) for 3. The ground state for 2 was determined from ac data, which indicated an S = 5 ground state. For 4, the pairwise exchange interactions were determined by fitting the susceptibility data vs T based on a 3-J model. Complex 1 exhibits out-of-phase ac susceptibility signals, indicating it may be a SMM.     

Cyanido-bridged Fe(III)-Mn(III) heterobimetallic materials built from Mn(III) Schiff base complexes and di- or tri-cyanido Fe(III) precursors

The reaction of [Fe(III)L(CN)(3)](-) (L being bpca = bis(2-pyridylcarbonyl)amidate, pcq = 8-(pyridine-2-carboxamido)quinoline) or [Fe(III)(bpb)(CN)(2)](-) (bpb = 1,2-bis(pyridine-2-carboxamido)benzenate) ferric complexes with Mn(III) salen type complexes afforded seven new bimetallic cyanido-bridged Mn(III)-Fe(III) systems: [Fe(pcq)(CN)(3)Mn(saltmen)(CH(3)OH)]·CH(3)OH (1), [Fe(bpca)(CN)(3)Mn(3-MeO-salen)(OH(2))]·CH(3)OH·H(2)O (2), [Fe(bpca)(CN)(3)Mn(salpen)] (3), [Fe(bpca)(CN)(3)Mn(saltmen)] (4), [Fe(bpca)(CN)(3)Mn(5-Me-saltmen)]·2CHCl(3) (5), [Fe(pcq)(CN)(3)Mn(5-Me-saltmen)]·2CH(3)OH·0.75H(2)O (6), and [Fe(bpb)(CN)(2)Mn(saltmen)]·2CH(3)OH (7) (with saltmen(2-) = N,N'-(1,1,2,2-tetramethylethylene)bis(salicylideneiminato) dianion, salpen(2-) = N,N'-propylenebis(salicylideneiminato) dianion, salen(2-) = N,N'-ethylenebis(salicylideneiminato) dianion). Single crystal X-ray diffraction studies were carried out for all these compounds indicating that compounds 1 and 2 are discrete dinuclear [Fe(III)-CN-Mn(III)] complexes while systems 3-7 are heterometallic chains with {-NC-Fe(III)-CN-Mn(III)} repeating units. These chains are connected through π-π and short contact interactions to form extended supramolecular networks. Investigation of the magnetic properties revealed the occurrence of antiferromagnetic Mn(III)···Fe(III) interactions in 1-4 while ferromagnetic Mn(III)···Fe(III) interactions were detected in 5-7. The nature of these Mn(III)···Fe(III) magnetic interactions mediated by a CN bridge appeared to be dependent on the Schiff base substituent. The packing is also strongly affected by the nature of the substituent and the presence of solvent molecules, resulting in additional antiferromagnetic interdinuclear/interchain interactions. Thus the crystal packing and the supramolecular interactions induce different magnetic properties for these systems. The dinuclear complexes 1 and 2, which possess a paramagnetic S(T) = 3/2 ground state, interact antiferromagnetically in their crystal packing. At high temperature, the complexes 3-7 exhibit a one-dimensional magnetic behavior, but at low temperature their magnetic properties are modulated by the supramolecular arrangement: a three-dimensional antiferromagnetic order with a metamagnetic behavior is observed for 3, 4, and 7, and Single-Chain Magnet properties are detected for 5 and 6.     

Crystal structures and magnetic properties of two low-dimensional materials constructed from [Mn(III)(salen)H2O]+ and [M(CN)8](3-/4-) (M = Mo or W) precursors

The syntheses, X-ray structures, and magnetic behaviors of two new cyano-bridged assemblies, the molecular [Mn(III)(salen)H2O]3[W(V)(CN)8].H2O (1) and one-dimensional [Mn(salen)(H2O)2]2[[Mn(salen)(H2O)][Mn(salen)]2[Mo(CN)(8)]].0.5ClO4.0.5OH.4.5H2O (2), are presented. Compound 1 crystallizes in the monoclinic system, has space group P2(1)/c, and has unit cell constants a = 13.7210(2) A, b = 20.6840(4) A, c = 20.6370(2) A, and Z = 4. Compound 2 crystallizes in the triclinic system, has space group P, and has unit cell dimensions a = 18.428(4) A, b = 18.521(3) A, c = 18.567(4) A, and Z = 2. The structure of 1 consists of the asymmetric V-shaped Mn-NC-W-NC-Mn-O(phenolate)-Mn molecules, where W(V) coordinates with [Mn(salen)H2O] and singly phenolate-bridged [Mn(salen)H2O]2 moieties through the neighboring cyano bridges. The [W(V)(CN)8]3- ion displays distorted square-antiprism geometry. The structure of 2 consists of the cyano-bridged [Mn3(III)Mo(IV)]n- repeating units linked by double phenolate bridges into one-dimensional zigzag chains. The Mn(III) centers are bound to Mo(IV) of square-antiprism geometry through the neighboring cyano bridges. The magnetic studies of 1 reveal the antiferromagnetic intramolecular interactions through the CN and phenolate bridges and the relatively weak intermolecular interactions. Compound 1 becomes antiferromagnetically ordered below TN = 4.6 K. The presence of the magnetic anisotropy is documented with the MH measurements carried out for both polycrystalline and single-crystal samples. At T = 1.9 K, the spin-flop transition is observed in the field of 18 kOe applied parallel to the bc plane, which is the easy plane of magnetization. Field dependence of magnetization of 1 shows field-induced metamagnetic behavior from the antiferromagnetic ground state of ST = 3/2 to the state of ST = 5/2. The magnetic properties of 2 indicate a weak antiferromagnetic interaction between Mn(III) centers in double-phenolate-bridged [Mn(III)(salen)]2 dinuclear subunits and a very weak ferromagnetic interaction between them through the diamagnetic [Mo(IV)(CN)8]4- spacer.     

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. Remarkably, the neutral mononuclear complex [Mn(3-MeOsalen)(H(2)O)(2)]ClO(4) co-crystallizes with the heterobimetallic unit in 2. The values of the Mn(III)-M(III) distance across the bridging cyanide are 5.228 (1), 5.505 (2) and 5.265 ? (3). The packing of the neutral heterobimetallic units in the crystal is governed by the self-complementarity of the [Mn(SB)(H(2)O)](+) moieties, which interact each other through hydrogen bonds established between the aqua ligand from one fragment with the set of phenolate- and methoxy-oxygens from the adjacent one. The magnetic properties of the three complexes have been investigated in the temperature range 1.9-300 K. Weak antiferromagnetic interactions between the Mn(III) and M(III) ions across the cyanido bridge were found: J(MnM) = -5.6 (1), -0.63 (2) and -2.4 cm(-1) (3) the Hamiltonian being defined as H = -JS(Mn)·S(M). Theoretical calculations based on density functional theory (DFT) have been used to substantiate both the nature and magnitude of the exchange interactions observed and also to analyze the dependence of the magnetic coupling on the structural parameters within the Mn(III)-N-C-M(III) motif in 1-3.     

Hydrothermal synthesis, structure, and luminescent properties of selected Zn(II)/Cd(II) coordination polymers constructed from 3,5-bis(x-pyridyl)-1,2,4-triazole (x = 3, 4)

Utilizing 3,5-bis(x-pyridyl)-1,2,4-triazole (x-Hpytz, x = 3; x = 4) as multidentate ligands, six novel coordination polymers with Zn(II) or Cd(II) metal ions were prepared: [Zn(3-pytz)(0.5)(OH)(0.5)Cl](n) (1, 1D ladder), {[Zn(3-Hpytz)(H(2)O)(4)] [Zn(3-Hpytz)(H(2)O)(3)·SO(4)]SO(4)·5H(2)O}(n) (2·5H(2)O, 1D chain), [Cd(3-Hpytz)(SO(4))](n) (3, 3D framework), {[Cd(3-Hyptz)SO(4)·3H(2)O]·2H(2)O}(n) (4·2H(2)O, 1D chain), [Zn(4-pytz)Cl](n) (5, 3D framework) and [Zn(2)(4-pytz)(SO(4))(OH)](n) (6, 3D framework). All compounds were obtained from hydrothermal reactions, with the exception of compound 4 which was obtained by solvent diffusion at room temperature. All compounds were characterized by FTIR, elemental analysis and TGA analysis and their structures were determined by X-ray diffraction. All compounds exhibited substantial thermal stability and showed photofluorescent properties that resulted from ligand π-π* transition.     

Heterometallic MIIRuIII2 compounds constructed from trans-[Ru(Salen)(CN)2]- and trans-[Ru(Acac)2(CN)2]-. Synthesis, structures, magnetic properties, and density functional theoretical study

The synthesis, structures, and magnetic properties of four cyano-bridged M(II)Ru(III)2 compounds prepared from the paramagnetic Ru(III) building blocks, trans-[Ru(salen)(CN)2]- 1 [H2salen = N,N'-ethylenebis(salicylideneimine)] and trans-[Ru(acac)2(CN)2]- (Hacac = acetylacetone), are described. Compound 2, {Mn(CH3OH)4[Ru(salen)(CN)2]2}.6CH3OH.2H2O, is a trinuclear complex that exhibits antiferromagnetic coupling between Mn(II) and Ru(III) centers. Compound 3, {Mn(H2O)2[Ru(salen)(CN)2]2.H2O}n, has a 2-D sheetlike structure that exhibits antiferromagnetic coupling between Mn and Ru, leading to ferrimagnetic-like behavior. Compound 4, {Ni(cyclam)[Ru(acac)2(CN)2]2}.2CH3OH.2H2O (cyclam = 1,4,8,11-tetraazacyclotetradecane), is a trinuclear complex that exhibits ferromagnetic coupling. Compound 5, {Co[Ru(acac)2(CN)2]2}n, has a 3-D diamond-like interpenetrating network that exhibits ferromagnetic ordering below 4.6 K. The density functional theory (DFT) method was used to calculate the molecular magnetic orbitals and the magnetic exchange interaction between Ru(III) and M(II) (Mn(II), Ni(II)) ions.     

Hexametallic manganese clusters with bulky derivatised salicylaldoximes

The reaction of Mn(ClO(4))(2)·6H(2)O with Ph-saoH(2) (Ph-saoH(2) = 2-hydroxybenzophenone oxime) in MeCN in the presence of sodium propionate forms the complex [Mn(III)(6)O(2)(Ph-sao)(6)(prop)(2)(MeCN)(2)]·5.27MeCN (1·5.27MeCN) (prop = propionate). Repeating the same reaction in EtOH produces the complex [Mn(III)(6)O(2)(Ph-sao)(6)(prop)(2)(EtOH)(4)] (2). Complexes 1 and 2 may be considered as structural isomers, since they display the same metallic core but different coordination modes of the propionate ligands; bridging in 1 and terminal in 2. Performing similar reactions and switching from sodium propionate to sodium adamantane-carboxylate (NaO(2)C-ada) and sodium pivalate (Napiv) in the presence of NEt(4)OH yields the complexes [Mn(III)(6)O(2)(Ph-sao)(6)(O(2)C-ada)(2)(MeOH)(4)] (3) and [Mn(III)(6)O(2)(Ph-sao)(6)(piv)(2)(EtOH)(4)]·0.5Et(2)O (4·0.5Et(2)O), respectively. All four complexes contain the same {Mn(III)(3)O(Ph-sao)(3)} building block. Variable temperature magnetic susceptibility and magnetization studies show that all complexes possess an S = 4 ground-state.     

Carboxylate-Free Manganese(II) Phosphonate Assemblies: Synthesis, Structure, and Magnetism

The reaction of manganese(II) salts with organophosphonic acid [t-BuPO(3)H(2) or cyclopentyl phosphonic acid (C(5)H(9)PO(3)H(2))] in the presence of ancillary nitrogen ligands [1,10-phenanthroline (phen) or 2,6-bis(pyrazol-3-yl)pyridine (dpzpy)], afforded, depending on the stoichiometry of the reactants and the reaction conditions, dinuclear, trinuclear, and tetranuclear compounds, [Mn(2)(t-BuPO(3)H)(4)(phen)(2)]·2DMF (1), [Mn(3)(C(5)H(9)PO(3))(2)(phen)(6)](ClO(4))(2)·7CH(3)OH (2), [Mn(3)(t-BuPO(3))(2)(dpzpy)(3)](ClO(4))(2)·H(2)O (3), [Mn(4)(t-BuPO(3))(2)(t-BuPO(3)H)(2)(phen)(6)(H(2)O)(2)](ClO(4))(2) (4), and [Mn(4)(C(5)H(9)PO(3))(2)(phen)(8)(H(2)O)(2)](ClO(4))(4) (5). Magnetic studies on 1, 2, and 4 reveal that the phosphonate bridges mediate weak antiferromagnetic interactions between the Mn(II) ions have also been carried out.     

Manganese(II)-carboxylate-pseudohalide systems derived from 1,4-bis(4-carboxylatopyridinium-1-methylene)benzene: structures and magnetism

The reactions of manganese(II) acetate or perchlorate, sodium azide or sodium cyanate, and the zwitterionic dicarboxylate ligand 1,4-bis(4-carboxylatopyridinium-1-methylene)benzene (L) under different conditions yielded three different Mn(II) coordination polymers with mixed carboxylate and azide (or cyanate) bridges: {[Mn (L(1))(0.5)(N(3))(OAc)]·3H(2)O}(n) (1), {[Mn(4)(L(1))(N(3))(8)(H(2)O)(4)(CH(3)OH)(2)]·[L(1)]}(n) (2), and {[Mn(3)(L(1))(NCO)(6)(H(2)O)(4)]·[L(1)]·[H(2)O](2)}(n) (3). The compounds exhibit diverse structures and magnetic properties. In 1, the 1D uniform anionic [Mn(N(3))(COO)(2)](n) chains with the (μ-EO-N(3))(μ-COO)(2) triple bridges (EO = end-on) are interlinked by the dipyridinium L ligands into highly undulated 2D layers. Magnetic studies on 1 reveal that the mixed triple bridges induce antiferromagnetic coupling between Mn(II) ions. Compounds 2 and 3 consist of 1D neutral polymeric chains and co-crystallized zwitterions, and the chains are formed by the L ligands interlinking linear polynuclear units. The polynuclear unit in 2 is tetranuclear with (μ-EO-N(3))(2) as central bridges and (μ-EO-N(3))(2)(μ-COO) as peripheral bridges, while that in 3 is trinuclear with (μ-NCO)(2)(μ-COO) bridges. Magnetic studies demonstrate that the magnetic coupling through the mixed azide/isocyanate and carboxylate bridges in 2 and 3 is antiferromagnetic. An expression of magnetic susceptibility based on a 2-J model for linear tetranuclear systems of classical spins has been deduced and applied to 2.     

Syntheses, structures, and magnetic properties of low-dimensional heterometallic complexes based on the versatile building block [(Tp)Cr(CN)3]-

Using the tricyano precursor (Bu(4)N)[(Tp)Cr(CN)(3)] (Bu(4)N(+) = tetrabutylammonium cation; Tp = tris(pyrazolyl)hydroborate), a pentanuclear heterometallic cluster [(Tp)(2)Cr(2)(CN)(6)Cu(3)(Me(3)tacn)(3)][(Tp)Cr(CN)(3)](ClO(4))(3)·5H(2)O (1, Me(3)tacn = N,N',N'-trimethyl-1,4,7-triazacyclononane), three tetranuclear heterometallic clusters [(Tp)(2)Cr(2)(CN)(6)Cu(2)(L(OEt))(2)]·2.5CH(3)CN (2, L(OEt) = [(Cp)Co(P(O)(OEt)(2))(3)], Cp = cyclopentadiene), [(Tp)(2)Cr(2)(CN)(6)Mn(2)(L(OEt))(2)]·4H(2)O (3), and [(Tp)(2)Cr(2)(CN)(6)Mn(2)(phen)(4)](ClO(4))(2) (4, phen = phenanthroline), and a one-dimensional (1D) chain polymer [(Tp)(2)Cr(2)(CN)(6)Mn(bpy)](n) (5, bpy = 2,2'-bipyridine) have been synthesized and structurally characterized. Complex 1 shows a trigonal bipyramidal geometry in which [(Tp)Cr(CN)(3)](-) units occupy the apical positions and are linked through cyanide to [Cu(Me(3)tacn)](2+) units situated in the equatorial plane. Complexes 2-4 show similar square structures, where Cr(III) and M(II) (M = Cu(II) or Mn(II)) ions are alternatively located on the rectangle corners. Complex 5 consists of a 4,2-ribbon-like bimetallic chain. Ferromagnetic interactions between Cr(III) and Cu(II) ions bridged by cyanides are observed in complexes 1 and 2. Antiferromagnetic interactions are presented between Cr(III) and Mn(II) ions bridged by cyanides in complexes 3-5. Complex 5 shows metamagnetic behavior with a critical field of about 22.5 kOe at 1.8 K.     

Coulombic aggregations of Mn(III) salen-type complexes and Keggin-type polyoxometalates: isolation of Mn2 single-molecule magnets

The reaction of Mn(III) salen-type complexes with di- and tetraanionic α-Keggin-type polyoxometalates (POMs) was performed, and three types of Coulombic aggregations containing Mn(III) out-of-plane dimeric units (abbreviated as [Mn(2)](2+)) that are potentially single-molecule magnets (SMMs) with an S(T) = 4 ground state were synthesized: [Mn(2)(5-MeOsaltmen)(2)(acetone)(2)][SW(12)O(40)] (1), [Mn(2)(salen)(2)(H(2)O)(2)](2)[SiW(12)O(40)] (2), and [Mn(5-Brsaltmen)(H(2)O)(acetone)](2)[{Mn(2)(5-Brsaltmen)(2)}(SiW(12)O(40))] (3), where 5-Rsaltmen(2-) = N,N'-(1,1,2,2-tetramethylethylene)bis(5-R-salicylideneiminate) with R = MeO (methoxy), Br (bromo) and salen(2-) = N,N'-ethylenebis(salicylideneiminate). Compound 1 with a dianionic POM, [SW(12)O(40)](2-), is composed of a 1:1 aggregating set of [Mn(2)](2+)/POM, and 2, with a tetraanionic POM, [SiW(12)O(40)](4-), is a 2:1 set. Compound 3 with [SiW(12)O(40)](4-) forms a unique 1D coordinating chain with a [-{Mn(2)}-POM-](2-) repeating unit, for which a hydrogen-bonded dimeric unit ([Mn(5-Brsaltmen)(H(2)O)(acetone)](2)(2+)) is present as a countercation. Independent of the formula ratio of [Mn(2)](2+)/POM, Mn(III) dimers and POM units in 1-3 form respective segregated columns along a direction of the unit cell, which make an alternate packing to separate evenly identical species in a crystal. The nearest intermolecular Mn···Mn distance is found in the order 2 < 3 < 1. The segregation of the [Mn(2)](2+) dimer resulted in interdimer distances long enough to effectively reduce the intermolecular magnetic interaction, in particular in 1 and 3. Consequently, an intrinsic property, SMM behavior, of Mn(III) dimers has been characterized in this system, even though the interdimer interactions are still crucial in the case of 2, where a long-range magnetic order competitively affects slow relaxation of the magnetization at low ac frequencies.     

Acid-base equilibrium of aqua-chromium-dioxolene complexes aimed at formation of oxo-chromium complexes

A series of aqua-Cr(III)-dioxolene complexes, [Cr(OH(2))(3,5-Bu(2)SQ)(trpy)](ClO(4))(2) (1s), [Cr(OH(2))(3,5-Bu(2)Cat)(trpy)]ClO(4) (1c), [Cr(OH(2))(3,6-Bu(2)SQ)(trpy)](ClO(4))(2) (2), [Cr(OH(2))(Cat)(trpy)]ClO(4) (3), [Cr(OH(2))(Cl(4)Cat)(trpy)]ClO(4) (4), [Cr(OH(2))(3,5-Bu(2)SQ)(Me(3)-tacn)](ClO(4))(2) (5), [Cr(OH(2))(Cat)(Me(3)-tacn)]ClO(4) (6), and [Cr(OH(2))(Cl(4)Cat)(Me(3)-tacn)]ClO(4) (7) (Bu(2)SQ = di-tert-butyl-o-benzosemiquinonate anion, Bu(2)Cat = di-tert-butylcatecholate dianion, Cat = catecholate dianion, Cl(4)Cat = tetrachlorocatecholate dianion, trpy = 2,2':6',2' '-terpyridine, and Me(3)-tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane), were prepared. On the basis of the crystal structures, redox behavior, and elemental analyses of these complexes, dioxolene in 1c, 3, 4, 6, and 7 coordinated to Cr(III) as the catechol form, and the ligand in 1s, 2, and 5 was linked to Cr(III) with the semiquinone form. All the aqua-Cr(III) complexes reversibly changed to the hydroxo-Cr(III) ones upon dissociation of the aqua proton, and the pK(a) value of the aqua-Cr(III) complexes increased in the order 6 > 3 approximately 1c > 7 > 5 approximately 4 > 1s. Hydroxo-Cr(III)-catechol complexes derived from 1c, 3, 4, 6, and 7 did not show any signs of dissociation of their hydroxy proton. On the other hand, hydroxo-Cr(III)-semiquinone complexes were reduced to hydroxo-Cr(III)-catechol in H(2)O/THF at pH 11 under illumination of visible light.     

Syntheses, structure, and magnetic properties of hexanuclear Mn(III)(2)M(III)(4) (M = Y, Gd, Tb, Dy) complexes

The synthesis and characterizations of a family of isomorphous [Mn(III)(2)M(III)(4)L(2)(μ(4)-O)(2)(N(3))(2)(CH(3)O)(2)(CH(3)OH)(4)(NO(3))(2)]·2H(2)O (M = Y(1), Gd(2), Tb(3), Dy(4)) are reported, where H(4)L = N,N'-dihydroxyethyl-N,N'-(2-hydroxy-4,5-dimethylbenzyl)ethylenediamine. They were obtained from the reactions of H(4)L with M(NO(3))(3)·6H(2)O, Mn(ClO(4))(2)·6H(2)O, NaN(3) and NEt(3) in a 1?:?1?:?1?:?2?:?2 molar ratio. The core structure consists of a Mn(2)M(4) unit. The four M(III) ions that are held together by two μ(4)-bridging oxygen atoms form a butterfly M(4) moiety. The M(4) core is further connected to the two five-coordinate trigonal-bipyramidal Mn(III) ions via one μ(4)-O(2-), two alkyloxo and one methoxo triple bridges. Magnetic susceptibility measurements indicate the presence of intramolecular antiferromagnetic interactions in complex 2, and overall intramolecular ferromagnetic interactions in complexes 3 and 4. The alternating current (AC) magnetic susceptibility studies revealed that complexes 3 and 4 showed frequency-dependent out-of-phase signals, which indicates that they exhibit slow relaxation of the magnetization.     

Self-assembly of unprecedented [8+12] Cu-metallamacrocycle-based 3D metal-organic frameworks

[8+12]-metallamacrocycle-based 3D frameworks {[Cu(4)(pbt)(2)(SO(4))(2)(DMF)(2)(CH(3)OH)]·7H(2)O·DMF}(n) (1) and [12]-macrocycle 3D {[Cu(2)(pbt)(SO(4))(DMSO)(CH(3)OH)(2)]·5H(2)O·CH(3)OH}(n) (2) have been obtained. Both complexes display antiferromagnetic couplings and high catalytic activity in the oxidative coupling reaction of 1-ethynylbenzene and oxazolidin-2-one.