Azido Bridges Research Articles

Difference in bonding behaviour of azide and thiocyanate to Hg(II)-azoimidazoles

Mercury(II) acetate reacts with the 1-alkyl-2-(arylazo)imidazoles [RaaiR′ where R = H ( a), Me ( b); R′ = Me ( 1/ 3/ 5), Et ( 2/ 4/ 6)] and sodium azide in methanol solution to afford azido bridged polymeric complexes [Hg(RaaiR′)(N 3) 2] n ( 3/ 4). On setting up similar reaction condition, the reaction of Hg(OAc) 2 with RaaiR′ and NH 4SCN has yielded, instead of polymer, an ion-pair [Hg(RaaiR′) 4][Hg(SCN) 4] ( 5/ 6). The complexes are characterised by elemental analysis, IR, UV–Vis, 1H NMR spectral data and single-crystal X-ray structures of [Hg(HaaiEt)(μ-1,1-N 3) 2] n ( 4a) and [Hg(HaaiEt) 4][Hg(SCN) 4] ( 6a). The complex 4a is a coordination polymer with end-on (μ-1,1) azido bridge and 6a has tetrahedral structure.

Crystal structures and magnetic behaviour of three new azido-bridged dinuclear cobalt(ii) and copper(ii) complexes

Three dinuclear cobalt(II) and copper(II) complexes with double end-on (EO) azido bridges, [Co2(DMP)2(N3)4] (1), [Cu2(DMP)2(N3)4] (2) and [Cu2(PAP)2(N3)4] (3) (DMP = 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine; PAP = 1-phenyl-2-(2-pyridyl)-1-azapropylene) have been synthesized and characterized by single-crystal X-ray diffraction and magnetic analyses. The EPR spectra of powder samples for the two copper(II) complexes have also been examined at room temperature and 77 K, respectively. In the isomorphous complexes 1 and 2, the metal ions are penta-coordinated with distorted trigonal bipyramidal geometries, and the EO azido bridges assume an equatorial–axial disposition between metal ions. In contrast, the copper(II) ion in complex 3 adopts a distorted square pyramidal geometry, and the EO azido bridges assume a basal–apical disposition between metal ions. According to magnetic studies, the double end-on azido bridges mediate ferromagnetic coupling with J = 18.1 cm−1 in 1, antiferromagnetic coupling with J = −27.6 cm−1 in 2, and ferromagnetic coupling with J = 35.0 cm−1 in 3.

Topological ferrimagnetic behavior of one new chain with the new AF/F/F′/F′/F alternating sequence

An azido-bridged chain with formula [Mn(Menic)(N3)2]n, where Menic is methylnicotinate, was prepared and studied from the magnetic point-of-view. This compound crystallizes in the monoclinic system, space group P21/a, with a = 15.556(2), b = 16.831(2), c = 17.595(2) A, β = 110.80(1)° and Z = 10. The structure consist of a one-dimensional system in which each manganese atom is bridged by two azido ligands in a trans arrangement. Along the chain there are four double end-on azido bridges followed by one double end-to-end azido bridge. This unusual kind of alternation leads to a new one-dimensional magnetic behavior, which has been studied by means of susceptibility and single crystal ESR measurements. The magnetic response has been reproduced by Monte Carlo simulations and exact laws following the classical approach. The characteristic signature of the magnetic behavior has allowed us to determine the three different magnetic coupling constants present in this system. These results have been analyzed in the framework of a theoretical and experimental magneto-structural correlation.

Azido-bridged Cu(II) compounds with asymmetric end-to-end and end-on binding modes: magnetic assignments using a spin dimer model

Dinuclear [Cu(aepi)(N 3) 2] 2 ( 1) [aepi = 1-(2-aminoethyl)piperidine] and 1D chain [Cu(aepy)(N 3) 2] n ( 2) [aepy = 1-(2-aminoethyl)pyrrolidine] have been prepared and characterized by means of X-ray analysis and magnetic measurements. For 1, the Cu(II) centers are doubly bridged by end-on (EO) azido units in a basal–apical fashion. The molecular structure of 2 features magnetic centers that are linked by μ-1,1,3 azido groups, forming a 1D chain with alternating EO and end-to-end (EE) azido bridging patterns. The magnetic data for the dinuclear complex 1 were fitted with the Bleaney–Bowers equation derived from the Hamiltonian H = − JS 1 · S 2, affording parameters of g = 2.093(1), J = −3.06(1) cm −1 and zJ′ = −1.32(3) cm −1. This indicates that the EO azido group mediates an antiferromagnetic interaction. Complex 2 has two possible magnetic pathways: one is through the EO azido bridge ( J eo) and the other via the EE bridge ( J ee). The alternating chain model with ferromagnetic and antiferromagnetic interactions based on the exchange Hamiltonian H = −∑ i [ J 1 S 2 i · S 2 i + 1 + J 2 S 2 i · S 2 i − 1 ] was employed, leading to g = 2.076(2), J 1 = −3.22(5) cm −1, J 2 = 17.0(5) cm −1 and zJ′ = −1.34(6) cm −1. By taking into account structural parameters of 1 and 2, it is rationally suggested that J 1 and J 2 are ascribed to J eo and J ee, respectively. These assignments are also ascertained by MO calculations using a spin dimer model.

A one-dimensional copper (II) coordination polymer [Cu 3(ampym) 2(μ 1,1-N 3) 4(μ 1,3-N 3) 2(dmf) 2] n (ampym = 2-aminopyrimidine) containing both end-on and end-to-end azido bridges

A new polynuclear copper (II) complex, derived from the azido-bridging ligand and 2-aminopyrimidine, has been synthesized and its 3-D structure has been determined by X-ray diffraction methods at two different temperatures. The compound crystallizes in the triclinic system P 1 ¯ space group, with the central copper atom lying on an inversion centre. The crystal structure is built up by trinuclear units (each of them contains two double end-on azido bridges) linked through two azide ions in an end-to-end (EE) fashion, to yield the polymer chain [Cu 3(ampym) 2(μ 1,1-N 3) 4(μ 1,3-N 3) 2(dmf) 2] n . Magnetic susceptibility measurement shows a ferromagnetic interaction above 30 K, whereas a weak anti-ferromagnetic interaction prevails in the range of 30–2 K.

(Schiff‐base)CuII Complexes with Phenolate‐Oxygen/Chloro or ‐Oxygen/Azido Mixed Bridges − Syntheses, Crystal Structures and Magnetic Properties

AbstractFour new CuII complexes of formulae [Cu3(SE)2(H2O)2Cl3]Cl·6H2O (1), Cu3(SE)2(N3)4(DMF)2 (2), Cu(SE)N3·DMF (3) and Cu(SE)N3·Cu(SE)N3 (4) with tridentate Schiff‐base ligands SE−, derived from condensation of N,N‐dimethylethylenediamine with salicylaldehyde, have been synthesised and characterised by IR spectroscopy, X‐ray structural analyses and variable‐temperature magnetic susceptibility measurements. Complex 1 has an alternating phenoxy‐ and chloro‐bridged 1D chain structure. Complex 2 possesses trinuclear units in which the CuII ions are bridged by single end‐on (µ‐1,1) azido ligands. Uniformly spaced 1D chains with end‐to‐end (µ‐1,3) azido bridges are found in 3 and 4. As expected, complexes 1 and 2 exhibit antiferromagnetic and ferromagnetic exchange, respectively. Compounds 3 and 4 show unusual ferromagnetic coupling though the 1,3‐azido pathways. Theoretical simulations have been carried out in order to evaluate the magnitude of the magnetic exchange and the magneto‐structural correlation has been investigated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Solvothermal synthesis, crystal structure and magnetic property of a new dinuclear manganese(II)–azido complex: [Mn(2,2′-dpa)(N 3) 2] 2 (2,2′-dpa = 2,2′-dipicolylamine)

A new dinuclear manganese(II)–azido complex: [Mn(2,2′-dpa)(N 3) 2] 2 1 (2,2′-dpa = 2,2′-dipicolylamine) has been synthesized solvothermally. X-ray crystallography analysis reveals that it consists of two crystallographically independent dimeric manganese moieties; each manganese(II) atom is coordinated by one 2,2′-dipicolylamine, one terminal azido ligand, and double end-on bridging azido ligands, exhibiting a slightly distorted octahedral sphere. There are extensive short contacts among dimeric manganese moieties, which extend the structure into an interesting three-dimensional supramolecular array. Magnetic determination of 1 indicates that dominant ferromagnetic interaction and weak antiferromagnetic interaction, which are ascribed to the end-on azido bridges and the short contacts, respectively, co-exist in this complex.

1D and 2D Systems Derived from Polynuclear [ML(N3)2]n (M?=?Zn(II) or Cd(II) and L is 2-Picoline-N-oxide or 4-Methylpyrimidine)

Four new polynuclear complexes: [Zn(2picNO)(N3)2]n, [Zn(4Mepym)(N3)2]n, [Cd(2picNO)(N3)2]n, and [Cd(4Mepym)(N3)2]n (2picNO = 2-picoline-N-oxide and 4Mepym = 4-methylpyrimidine) have been synthesized and characterized by single-crystal X-ray diffraction. The structures of the zinc(II) complexes feature five-coordinate zinc atoms, (μ-1,1) azido bridges, monodentate organic ligands, and 1D chains. The cadmium(II) azide complexes contain distorted octahedral metal atoms linked by alternate di-(μ-1,1) and di-(μ-1,3) azido bridges in cis arrangement and these chains are connected by 2picNO bridges giving a honeycomb 2D framework or by 4Mepym bridges forming extended 2D network structure.

Mixed pseudohalide complexes of copper(II). Crystal and molecular structure of [Cu(N3)(NCS)(tmen)] n and of [Cu(N3)(NCO)(tmen)]2 (tmen = N,N,N′,N′-tetramethylethylenediamine)

The compounds [Cu(N3)(NSC)(tmen)] n (1), [Cu(N3)(NCO)(tmen)] n (2) and [Cu(N3)(NCO)(tmen)]2 (3) (tmen=N,N,N′,N′-tetramethylethylenediamine) were synthesized and studied by i.r. spectroscopy. Single crystals of compounds (1) and (3) were obtained and characterized by X-ray diffraction. The structure of compound (1) consists of neutral chains of copper(II) ions bridged by a single azido ligand showing the asymmetric end-to-end coordination fashion. Each copper ion is also surrounded by the other three nitrogen atoms; two from one N,N,N′,N′-tetramethylethylenediamine and one from a terminal bonded thiocyanate group. Compound (2) decomposes slowly in acetone and the product formed [Cu(N3)(NCO)(tmen)]2 (3) crystallizes in the monoclinic system (P21). The structure of (3) consists of dimeric units in which the Cu atoms are penta-coordinated and connected by μ(1,3) bridging azido and cyanate ligands. In both cases the five coordinated atoms give rise to a slightly distorted square-based pyramid coordination geometry at each copper ion. The thermal behavior of [Cu(N3)(NSC)(tmen)] n (1) and [Cu(N3)(NCO)(tmen)] n (2) were investigated and the final decomposition products were identified by X-ray powder diagrams.

Synthesis, X-ray structure, spectroscopic and magnetic properties of [Cu(DACO)(μ-1,1-N 3)(μ-1,3-N 3)] n and [Cu(DACO)(μ-NCS)(NCS)] n (DACO=1,5-diazacyclooctane)

Two new one-dimensional copper(II) complexes bridged by azide and thiocyanate, [Cu(DACO)(μ-1,1-N 3)(μ-1,3-N 3)] n ( 1) and [Cu(DACO)(μ-NCS)(NCS)] n ( 2), where DACO=1,5-diazacyclooctane, have been synthesized and characterized. Single crystal X-ray diffraction analysis reveals that the bridging azido groups in complex 1 are coordinated alternately in the single end-to-end and single end-on models, giving an alternate chain, the unbridged N 3 − groups acted as the terminal ligands. In complex 2, the strictly alternating copper ions and thiocyanates produce a chain in which the metallic centers are connected through single end-on-end NCS − groups. The central copper(II) ions in both complexes are penta-coordinated and situated in a distorted square-pyramid environment. Low temperature magnetic susceptibility indicates that complex 1 shows an antiferromagnetic behavior with the value for exchange coupling constant J is −4.06 cm −1, and g=2.038; while the complex 2 exhibits a weak ferromagnetic interactions between the copper ions with J=1.04 cm −1 and the corresponding g=2.03. Moreover, the two complexes have also been characterized on the basis of elemental analysis, IR and UV–vis spectroscopy.

Synthesis, structure and magnetic properties of the novel heteropolynuclear complex bridged by azido

Synthesis of the first heterometallic hexapolynuclear complex [(CuL) 4Mn 2(N 3) 4] · 2MeOH which is bridged by azido and macrocyclic oxamido bridge and especial the azido bridge links to two different metal ions, has been reported in this paper and the complex was characterised by low-temperature magnetic measurements.

Supramolecular Hydrogen‐Bond Structures and Magnetic Interactions in Basal‐Apical, Dinuclear, Azide‐Bridged Copper(II) Complexes

AbstractThe synthesis, characterisation, X‐ray single crystal structures and magnetic properties of three new basal‐apical μ2‐1,1‐azide‐bridged complexes [CuL1N3]2 (1), [CuL2N3]2 (2) and [CuL3N3]2 (3) with very similar tridentate Schiff‐base blocking ligands {HL1 = N‐[2‐(ethylamino)ethyl]salicylaldimine; HL2 = 7‐(ethylamino)‐4‐methyl‐5‐azahept‐3‐en‐2‐one; HL3 = 7‐amino‐4‐methyl‐5‐azaoct‐3‐en‐2‐one} have been reported [complex 1: monoclinic, P21/c, a = 8.390(2), b = 7.512(2), c = 19.822(6) Å, β = 91.45(5)°; complex 2: monoclinic, P21/c, a = 8.070(9), b = 9.787(12), c = 15.743(17) Å, β = 98.467(10)°; complex 3: monoclinic, P21/n, a = 5.884(7), b = 16.147(18), c = 11.901(12) Å, β = 90.050(10)°]. The structures consist of neutral dinuclear entities resulting from the pairing of two mononuclear units through end‐on azide bridges connecting an equatorial position of one copper centre to an axial position of the other. The copper ions adopt a (4+1) square‐based geometry in all the complexes. In complex 2, there is no inter‐dimer hydrogen‐bonding. However, complexes 1 and 3 form two different supramolecular structures in which the dinuclear entities are linked by H‐bonds giving one‐dimensional systems. Variable temperature (300−2 K) magnetic‐susceptibility measurements and magnetisation measurements at 2 K reveal that all three complexes have antiferromagnetic coupling. Magneto‐structural correlations have been made taking into consideration both the azido bridging ligands and the existence of intermolecular hydrogen bonds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Polynuclear and Extended Coordination Compounds from Preorganized Bimetallic Components: Tuning the Magnetic Properties of Dinickel(II) Building Blocks

AbstractVarious dinucleating pyrazole ligands with chelating side arms in the 3‐ and 5‐positions of the heterocycle have been shown to form NiII/azido complexes, where the metal ions are spanned by the pyrazolate, and an azido bridge. Four new complexes have been characterized by X‐ray crystallography and variable‐temperature magnetic susceptibility studies. The Ni···Ni distance, and hence the intra‐dimer coordination mode of the azide (μ‐1,1 or μ‐1,3), is determined by the chelate arm length, such that the magnetic properties of the bimetallic units can be controlled. The intramolecular coupling between the NiII (S = 1) ions was found to be ferromagnetic (J = +4.0 ± 0.5 cm−1) in the case of [L1Ni2(N3)(NO3)2] (1) with a μ‐1,1 azide, but antiferromagnetic (J = −25.7 ± 0.3 cm−1) for [L2Ni2(N3)](ClO4)2 (2) with a μ‐1,3 azide. Such bimetallic units can serve as building blocks for the construction of high‐nuclearity NiII/azide compounds, as demonstrated for the tetranuclear complexes [L12Ni4(μ‐1,1‐N3)2(μ‐1,3‐N3)2](BPh4)2 (3), and [L3Ni2(N3)3]2 (4). Complex 3 was obtained by the replacement of the labile nitrates in 1 by additional azido ligands, that bridge the two [L1Ni2(N3)]2+ subunits in the μ‐1,3 mode. Complex 4 incorporates two additional azides, and two of its azido linkages were found in the rare μ‐1,1,3 binding mode (albeit with relatively long Ni−N bond lengths). The magnetic properties of the tetranuclear species were as predicted from the building blocks and the respective azide binding, with ferromagnetic intra‐dimer and antiferromagnetic inter‐dimer exchanges, yielded an overall S = 0 ground state. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

A nonanuclear iron(II) single-molecule magnet.

Dressed up to the nines: A nonanuclear FeII complex exhibiting rare μ4:η1 azido bridges that induce ferromagnetic exchange interactions possesses a core with a very large ground-state spin (probably S=14, see picture). The combination of a large S value and the magnetic anisotropy of iron(II) centers endows this unique species with superparamagnetic behavior (SMM=single-molecule magnet).

Realization of unusual ligand binding motifs in metalated container molecules: synthesis, structures, and magnetic properties of the complexes [(LMe)Ni2(mu-L')]n+ with L'=NO3-, NO2-, N3-, N2H4, pyridazine, phthalazine, pyrazolate, and benzoate.

A series of dinickel(II) complexes with the 24-membered macrocyclic hexaazadithiophenol ligand H(2)L(Me) was prepared and examined. The doubly deprotonated form (L(Me))(2-) forms complexes of the type [(L(Me))Ni2II(mu-L')](n+) with a bioctahedral N(3)Ni(II)(mu-SR)(2)(mu-L')Ni(II)N(3) core and an overall calixarene-like structure. The bridging coordination site L' is accessible for a wide range of exogenous coligands. In this study L'=NO(3)(-), NO(2)(-), N(3)(-), N(2)H(4), pyrazolate (pz), pyridazine (pydz), phthalazine (phtz), and benzoate (OBz). Crystallographic studies reveal that each substrate binds in a distinct fashion to the [(L(Me))Ni(2)](2+) portion: NO(2)(-), N(2)H(4), pz, pydz, and phtz form mu(1,2)-bridges, whereas NO(3)(-), N(3)(-), and OBz(-) are mu(1,3)-bridging. These distinctive binding motifs and the fact that some of the coligands adopt unusual conformations is discussed in terms of complementary host-guest interactions and the size and form of the binding pocket of the [(L(Me))Ni(2)](2+) fragment. UV/Vis and electrochemical studies reveal that the solid-state structures are retained in the solution state. The relative stabilities of the complexes indicate that the [(L(Me))Ni(2)](2+) fragment binds anionic coligands preferentially over neutral ones and strong-field ligands over weak-field ligands. Secondary van der Waals interactions also contribute to the stability of the complexes. Intramolecular ferromagnetic exchange interactions are present in the nitrito-, pyridazine-, and the benzoato-bridged complexes where J=+6.7, +3.5, and +5.8 cm(-1) (H=-2 JS(1)S(2), S(1)=S(2)=1) as indicated by magnetic susceptibility data taken from 300 to 2 K. In contrast, the azido bridge in [(L(Me))Ni(2)(mu(1,3)-N(3))](+) results in an antiferromagnetic exchange interaction J=-46.7 cm(-1). An explanation for this difference is qualitatively discussed in terms of bonding differences.

New Two-Dimensional Manganese(II)-Azido Polymers with Bidentate Coligands: Structure and Magnetic Properties

Two two-dimensional azido-bridged Mn(II) coordination polymers with bidentate coligands have been synthesized and structurally characterized, and their magnetic properties were studied. The complexes are of formula [Mn(bphz)(N3)2]n (1) and [Mn(mipc)(N3)2]n (2), where bphz = 2-benzoylpyridine hydrazone and mipc = methyl imidopyrazinecarboxylate. Both complexes consist of (6,3) layers in which double end-on (EO) azido-bridged dimers are interlinked by single end-to-end (EE) azido bridges, representing new examples of the sparse 2D Mn(II)-azido polymers assisted by bidentate coligands. Magnetic studies on the complexes reveal that ferromagnetic and antiferromagnetic interactions are mediated through the EO and EE azido bridges, respectively, with the global effect being antiferromagnetic. Both complexes exhibit spin canting related to the lack of inversion centers between the EE azido-bridged Mn(II) ions. Complex 1 behaves as a weak ferromagnet below 20 K, due to the long-range ordering of the residual spins...

A unique 3D alternating ferro- and antiferromagnetic manganese azide system with threefold interpenetrating (10,3) nets.

Alternative bridging: Alternating ferro- and antiferromagnetic interactions are mediated by alternating end-on and end-to-end azido bridges, respectively, in a novel manganese azido complex. The compound has an interesting framework of threefold interpenetrating (10,3) nets, one of which is shown in the picture. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2004/z52780_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

New poly-iron(II) complexes of N4O dinucleating Schiff bases and pseudohalides: syntheses, structures, and magnetic and Mössbauer properties.

Six dinuclear ferrous complexes including [Fe2(acpypentO)(O2CMe)(NCS)2] (1), [Fe2(acpypentO)(O2CMe)(NCSe)2] (2), [Fe2(acpypentO)(NCO)3] (3), ([Fe2(acpybutO)(O2CMe)(NCS)2] (5), [Fe2(acpybutO)(O2CMe)(NCO)2] (6), and [Fe2(acpybutO)(O2CMe)(N3)2] (7), one tetranuclear (bis-dinuclear) ferrous compound, [Fe4(acpypentO)2(N3)6] (4), and one mononuclear ferrous compound, [Fe(acpybutOH)(NCS)2] (8), have been prepared, and their structures and magnetic and Mössbauer properties have been studied (acpybutOH = 1,4-bis[[2-pyridyl(1-ethyl]imino)]butane-2-ol and acpypentOH = 1,5-bis[[2-pyridyl(1-ethyl]imino)]pentane-3-ol). The X-ray diffraction analyses yielded the following results: 1 (C23H26Fe2N6O3S2, monoclinic, P2(1)/n, a = 8.0380(7) A, b = 12.4495(8) A, c = 27.358(2) A, beta = 92.180(10) degrees, V = 2735.7(4) A(3), Z = 4) is a dinuclear species in which the unequivalent high-spin (HS) Fe(II) sites are bridged by the alkoxo oxygen atom of the symmetrical acpypentO- Schiff base and one syn-syn acetato anion; 3 (C22H23Fe2N7O4, triclinic, Ponemacr;, a = 8.4152(10) A, b = 9.1350(10) A, c = 17.666(2) A, alpha = 97.486(14) degrees, beta = 100.026(14) degrees, gamma = 113.510(13) degrees, V = 1195.9(2) A3, Z = 2) is a dinuclear species in which the unequivalent HS Fe(II) sites are bridged by the alkoxo oxygen atom of the symmetrical acpypentO- Schiff base and one end-on NCO anion; 4-MeOH (C39H50Fe4N26O3, triclinic, Ponemacr;, a = 9.1246(11) A, b = 10.2466(11) A, c = 14.928(2) A, alpha = 91.529(15) degrees, beta = 101.078(16) degrees, gamma = 106.341(14) degrees, V = 1309.6(3) A3, Z = 1) is a bis-dinuclear species in which the unequivalent HS Fe(II) sites are bridged by the alkoxo oxygen atom of the symmetrical acpypentO- Schiff base and one end-on N(3)(-) anion, and the symmetry related Fe(II) sites are bridged by two end-on N3- anions; 8-MeOH (C21H26FeN6O2S2, triclinic, Ponemacr;, a = 8.7674(9) A, b = 12.0938(13) A, c = 12.2634(14) A, alpha = 106.685(14) degrees, beta = 93.689(14) degrees, gamma = 108.508(13) degrees, V = 1163.7(2) A3, Z = 2) is a mononuclear species in which the octahedral low-spin (LS) Fe(II) site is in an N6 environment provided by the four N atoms of the protonated asymmetrical acpybutOH Schiff base and two thiocyanato anions. The Mössbauer spectra of all dinuclear species (1-3 and 5-7), and of the bis-dinuclear compound 4, evidence two distinct HS Fe(II) sites while the Mössbauer spectra of the mononuclear compound 8 evidence a LS Fe(II) site over the 80-300 K temperature range. The temperature dependence of the magnetic susceptibility was fitted with J = -13.7 cm(-1), D = -1.8 cm(-1), and g = 2.096 for 1; J = 3.0 cm(-1), D(1) = 1.6 cm(-1), E(1) = -0.35 cm(-1) (lambda(1) = 0.22), D2 = - 12.2 cm(-1), E2 = 1.1 cm(-1) (lambda2 = 0.09), and g = 2.136 for 3; and J(1) = - 0.09 cm(-1), J(2) = 15.9 cm(-1), D(1) = 5.7 cm(-1), D(2) = 12.1 cm(-1), and g = 1.915 for 4. The nature of the ground state in 3 and 4 was confirmed by simulation of the magnetization curves at 2 and 5 K. The intradinuclear interaction through the central O(alkoxo) of the acpypentO- ligand and one pseudohalide bridges is ferromagnetic in 3 (end-on cyanato) while it is very weakly antiferromagnetic in 4 (end-on azido). The interdinuclear interaction through two end-on azido bridges (4) is ferromagnetic as expected. In agreement with the symmetry of the two iron sites of complexes 3 and 4, the fits show that D2 (tetragonal pyramid) is larger than D1 (distorted trigonal bipyramid (3) or distorted octahedron (4)).

From achiral ligands to chiral coordination polymers: spontaneous resolution, weak ferromagnetism, and topological ferrimagnetism.

Using the achiral diazine ligands bearing two bidentate pyridylimino groups as sources of conformational chirality, five azido-bridged coordination polymers are prepared and characterized crystallographically and magnetically. The chirality of the molecular units is induced by the coordination of the diazine ligands in a twisted chiral conformation. The use of L(1) (1,4-bis(2-pyridyl)-1-amino-2,3-diaza-1,3-butadiene) and L(2) (1,4-bis(2-pyridyl)-1,4-diamino-2,3-diaza-1,3-butadiene) induces spontaneous resolution, yielding conglomerates of chiral compounds [Mn(3)(L(1))(2)(N(3))(6)](n) (1) and [Mn(2)(L(2))(2)(N(3))(3)](n)(ClO(4))(n).nH(2)O (2), respectively, where triangular (1) or double helical (2) chiral units are connected into homochiral one-dimensional (1D) chains via single end-to-end (EE) azido bridges. The chains are stacked via hydrogen bonds in a homochiral fashion to yield chiral crystals. When L(3) (2,5-bis(2-pyridyl)-3,4-diaza-2,4-hexadiene) is employed, a partial spontaneous resolution occurs, where binuclear chiral units are interlinked into fish-scale-like homochiral two-dimensional (2D) layers via single EE azido bridges. The layers are stacked in a heterochiral or homochiral fashion to yield simultaneously a racemic compound, [Mn(2)(L(3))(N(3))(4)](n) (3a), and a conglomerate, [Mn(2)(L(3))(N(3))(4)](n).nMeOH (3b). On the other hand, the ligand without amino and methyl substituents (L(4), 1,4-bis(2-pyridyl)-2,3-diaza-1,3-butadiene) does not induce spontaneous resolution. The resulting compound, [Mn(2)(L(4))(N(3))(4)](n) (4), consists of centrosymmetric 2D layers with alternating single diazine, single EE azido, and double end-on (EO) azido bridges, where the chirality is destroyed by the centrosymmetric double EO bridges. These compounds exhibit very different magnetic behaviors. In particular, 1 behaves as a metamagnet built of homometallic ferrimagnetic chains with a unique "fused-triangles" topology, 2 behaves as a 1D antiferromagnet with alternating antiferromagnetic interactions, 3a and 3b behave as spin-canted weak ferromagnets with different critical temperatures, and 4 also behaves as a spin-canted weak ferromagnet but exhibits two-step magnetic transitions.

Cu(L)Mn(N3)2]n: the first complex containing both macrocyclic oxamido and alternate (mu-1,1 and mu-1,3) azido bridges.

A wattle-type heteropolynuclear complex [(CuL)Mn(N(3))(2)](n) (1) (H(2)L = 2,3-dioxo-5,6:15,16-dibenzo-1,4,8,13-tetraazacyclo-pentadeca-7,13-diene), which represents the first system with macrocyclic oxamido and alternate azido bridges, forming a one-dimensional chain structure, has been synthesized and characterized by a low temperature magnetic study. The chains are stacked with interchain hydrogen and lead to the structure of a three-dimensional network.