Azido Bridges Research Articles

Synthesis, characterization, and structures of two new tetranuclear copper complexes with azido/dicyanamide bridges containing chiral Schiff base ligand

Two new copper complexes [Cu4(μ-L)2(μ1,1-N3)2(N3)2] (I) and [Cu4(μ-L)2(μ1,5-Dca)2(Dca)2] (II) (H2L = (1R,3S)-N′,N″-bis[5-methoxysalicylidene]-1,3-diamino-1,2,2-trimethylcyclopentane, Dca = dicyanamide ions) were synthesized and structurally characterized by elemental analyses, IR spectroscopy and single-crystal X-ray diffraction (CIF files CCDC nos. 1013673 (I), 1013672 (II)). The two complexes crystallize in monoclinic P21/c and triclinic $P\bar 1$ space group, respectively. Both the complexes consist of two crystallographically independent copper ions connected by a double phenoxo bridges, which are further linked to the other symmetry-related half of the molecule by two end-on azido bridges or μ1,5-dca groups.

A novel 2-D coordination polymer with mixed azido and alkoxido bridges: Synthesis, structure and magnetic properties

A novel 2-D coordination polymer [Cu2(L)(N3)3]n 1 (HL: 1,5-diaminopentan-3-ol) has been synthesized and its crystal structure and magnetic properties have been studied. The crystal structure of the compound 1 consists of binuclear moieties [Cu2(L)(N3)3] with mixed alkoxido/end-on azido bridges, which are linked by double asymmetric end-on and single asymmetric end-to-end azido bridges, resulting in a 2-D layer extended within the ab crystallographic plane. Variable-temperature magnetic susceptibility data evidence strong antiferromagnetic interaction between the CuII ions within the binuclear units, which are mediated by the two types of bridges (J=−123(2)cm−1, H=−2JS1S2). The experimental value of the exchange coupling constant is confirmed by DFT calculations.

Two novel azido-copper(II) complexes with 4-(1H-tetrazol-1-yl) carboxylate: Synthesis, crystal structure, and magnetism

Using same reactants with different mol ratio, two novel azido-copper(II) compounds [Cu(L)(N3)]n (1) and {[Cu3(L)2(N3)4](CH3OH)3}n (2) {HL=4-(1H-tetrazol-1-yl) benzoic acid} have been synthesized by the method of liquid diffusion at room temperature and structurally characterized. Single crystal X-ray diffraction analyses show that complex 1 has a two dimensional (2D) coordination structure with carboxylate/EO (end on)-azido mixed-bridged copper(II) chains, while 2 possesses different Cu−N3−/COO− one dimensional (1D) chains from that of 1, with double EE (end to end) azido bridge and carboxylate/EO-azido mixed-bridge coexisting, forming a 2D supramolecular framework by interchain H-bonds. The structural difference between 1 and 2 suggests that the tetrazolyl motif also has important influence on the construction of these complexes. Magnetic study indicates that domain ferromagnetic coupling interactions exist in both 1 and 2.

Crystal structure of an end-on azido-bridged polymeric zinc(II) complex

A new end-on azido-bridged polymeric zinc(II) complex [Zn2ClL(μ1,1-N3)]n, where L is the dianionic form of N,N′-bis(5-fluoro-2-hydroxybenzylidene)-2-hydroxy-1,3-propanediamine, is prepared and structurally characterized by elemental analysis and single crystal X-ray diffraction. The complex crystallizes in the monoclinic space group P21/c, with unit cell dimensions a = 9.194(1) A, b = 22.356(2) A, c = 9.598(1) A, β = 95.869(3)°, V = 1962.5(4) A3, Z = 4, R1 = 0.0691, and wR2 = 0.1642. The inner Zn atom of the [Zn2ClL] unit is coordinated by the imino N and phenolate O atoms of L and one azido N atom, forming a square pyramidal geometry. The outer Zn atom of the [Zn2ClL] unit is coordinated by two phenolate O of L, one Cl ligand, and one N atom of the bridging azide group, forming a tetrahedral geometry. The Zn⋯Zn distance in the [Zn2ClL] unit is 3.072(2) A. The [Zn2ClL] units are linked through end-on azido bridges, forming 1D chains running along the c axis.

Different topologies in three manganese-μ-azido 1D compounds: magnetic behavior and DFT-quantum Monte Carlo calculations.

The syntheses and structural characterization of three new monodimensional azido-bridged manganese(ii) complexes with empirical formulae [Mn(N3)2(aminopyz)2]n (1), [Mn(N3)2(4-azpy)2]n (2) and [Mn(N3)2(4-Bzpy)2]n (3) (pyz = pyrazine (1,4-diazine)), 4-azpy = 4-azidopyridine and 4-Bzpy = 4-benzoylpyridine) are reported. 1 is a monodimensional compound with double EO azido bridges, 2 is an alternating monodimensional compound with double end-on and double end-to-end azido bridges in the sequence di-EO-di-EE and 3 is a monodimensional compound with double end-on and double end-to-end azido bridges in the sequence di-EO-di-EO-diEO-di-EO-di-EE. The magnetic properties of 1-3 are reported. Periodic DFT calculations were performed to estimate the J values and quantum Monte Carlo simulations were carried out using the calculated J values to check their accuracy in comparison with the experimental magnetic measurements. From this theoretical analysis, two appealing features of the di-EO Mn(ii) compounds can be extracted: first, the exchange coupling becomes more ferromagnetic when the Mn-N-Mn bridging angle becomes larger and the spin density of the bridging nitrogen atoms has an opposite sign to that of the Mn(II) centers.

Four tetrazolate-based 3D frameworks with diverse subunits directed by inorganic anions and azido coligand: hydro/solvothermal syntheses, crystal structures, and magnetic properties.

Four tetrazolate (tz(-))-based magnetic metal-organic frameworks, [Cu5(μ3-OH)2(SO4)2(tz)4]n (), {[Cu3(tz)4Cl2]·1.4CH3OH}n (), [Cu(N3)(tz)]n () and {[Cu5(tz)9]Cl·4H2O}n (), were hydro/solvothermally synthesized, and structurally and magnetically characterized. Structural analyses reveal that the former two samples exhibit the same eight-connected topological framework assembled from different subunits. Hourglass-shaped {Cu5(μ3-OH)2}(8+) cores in are periodically extended by mixed μ3-/μ4-tz(-) and μ4-SO4(2-) heterolinkers, while the linear {Cu3(μ-Cl)2}(4+) blocks in are repeatedly intersected by ditopic μ3-tz(-) connectors. In contrast, the square grid-shaped network of is constructed from linear {Cu(μ1,1-N3)}(+) chains and μ3-tz(-) linkers. Complex consists of trigonal-prismatic {Cu8(μ3-tz)6}(10+) subunits, which are interlinked into hexagonal microporous architecture by mirror-symmetry μ4-tz(-) ligands. Thus, the various subunits of are significantly tuned by the co-coordination of the inorganic anions and/or the azido co-ligand, and the backbone extensions are directed by the polytopic tetrazolate ligand. Magnetically, different ordering arrangements of the non-zero magnetizations produced in the local Cu(II)5 and Cu(II)3 subunits eventually lead to unusual ferrimagnetic and canted antiferromagnetic properties in and . Strong antiferromagnetic couplings mediated by the mixed tz(-) and/or azido bridges result in overall S = 0 spin ground-states of and .

Sonochemical syntheses of binuclear lead(II)-azido supramolecule with ligand 3,4,7,8-tetramethyl-1,10-phenanthroline as precursor for preparation of lead(II) oxide nanoparticles

The new neutral binuclear lead(II) azido coordination compound, [Pb2(tmph)2(μ-N3)2(CH3COO)2] (1) [tmph=3,4,7,8-tetramethyl-1,10-phenanthroline], has been synthesized by a sonochemical method. Single crystal X-ray structure shows that the overall structure of 1 is binuclear unit. Complex 1 has a bridging azido pathway, end-to-end bridging azides between a pair of lead(II) centers. This is further extended into a one-dimensional (1D) and three-dimensional (3D) supramolecular structure by Pb⋯C and π–π weak directional intermolecular interactions. The coordination number of lead(II) ions is seven, PbN4O3, with two N-donor atoms from tmph ligands and three O-donors from acetate anions and two N-donors from two azide anions. It has a “stereo-chemically active” electron lone pair, and the coordination sphere is hemidirected. The PbO nanoparticles were obtained by thermolysis of 1 at 180°C with oleic acid as a surfactant. The morphology and size of the prepared PbO samples were further observed using scanning electron microscopy (SEM).

2‐Pyridylcyanoxime–Ni II Clusters with Unusual Topologies: Lone‐Pair–π Interactions and Magnetic Properties

Three new complexes derived from the reaction of the 2-pyridylcyanoxime ligand (pyC{CN}NOH) with several non-carboxylate nickel salts have been structural and magnetically characterized. The compounds with the formula [Ni3(MeOH)2(CF3COO)(OH)(pyC{CN}NO)4] (1), [NaNi(tfacac)3]n (2; tfacac = 1,1,1-trifluoroacetylacetone), [Ni5(H2O)2(N3)2(pyC{CN}NO)8] (3), and [Ni3(pyC{CN}NO)5(pyC{CN}NOH)](BF4) (4) exhibit unusual topologies with a triangular {Ni3(μ3-OH)(pyC{R′}NO)3}2+ core for 1, vertex-shared triangles with a {Ni5(μ1,1-N3)2(pyC{CN}NO)6}2+ core for 3, and a {Ni3(pyC{CN}NO)4}2+ core for 4. Direct-current (DC) magnetic measurements performed in the 2–300 K temperature range reveal antiferromagnetic interactions induced by the μ3-OR or oximato superexchange pathways and ferromagnetic interactions promoted by the azido bridges, thereby resulting in ground states S = 0, 3, and 1 for 1, 3, and 4, respectively. Supramolecular lone-pair–π-ring interactions are reported for the first time for the pyC{CN}NO– ligand and its importance in the crystal packing is discussed.

New Classes of Ferromagnetic Materials with Exclusively End‐on Azido Bridges: From Single‐Molecule Magnets to 2 D Molecule‐Based Magnets

A new, flexible synthetic route, which does not require the co-presence of any organic chelating/bridging ligand but only the "key" precursor Me3SiN3, has been discovered and led to a new class of inorganic materials containing exclusively end-on azido bridges; the reported 3d-metal clusters and coordination polymers exhibit ferromagnetic, single-molecule magnet, and long-range magnetic ordering properties.

The Impact of Anion‐Modulated Structural Variations on the Magnetic Coupling in Trinuclear Heterometallic CuII–CoII Complexes Derived from a Salen‐Type Schiff Base Ligand

AbstractThree new trinuclear heterometallic [(CuIIL)2CoIIX2] complexes [H2L = N,N′‐bis(salicylidene)‐1,3‐propanediamine and X = thiocyanate (1), benzoate (2), or azide (3)] have been synthesized by reacting the metalloligand [CuL] with Co(ClO4)2·6H2O and the NH4+ or Na+ salt of the corresponding anion in methanol. Structural characterization reveals that the central CoII ion is connected to two terminal metalloligands through μ1,1‐diphenoxido bridges in all three complexes. However, two monodentate thiocyanato ions, which are mutually cis coordinated to the Co atom in 1, generate a “bent” structure, whereas the trans‐coordinated syn–syn bridging benzoato (1κO:2κO′) and the end‐on bridging azido (μ1,1) coligands in 2 and 3, respectively, produce linear structures. The changes in the number and nature of the bridges with a shortening of the distances between the metal centers leads to a concomitant decrease of the average CuII–O–CoII bridging angle from 99.3(2) to 97.1(4) and 91.5(1)° for 1, 2 and 3, respectively. Variable‐temperature magnetic susceptibility measurements show the presence of a dominant antiferromagnetic coupling between the Cu–Co pairs in all three complexes. However, a steady decrease of the magnitude of the exchange coupling constant (JCu‐Co) is observed from –33.4 (for 1) to –11.4 (for 2) and –2.15 cm–1 (for 3). This trend suggests that larger Cu–O–Co angles are associated with stronger antiferromagnetic coupling.

Synthesis, structure and magnetic properties of a series of cubane-like clusters derived from Schiff base ligands

One new hexanuclear Cu(II) complex [Cu4(L1)4Na2(ClO4)(H2O)](ClO4)(H2O)0.5 (1) and two new tetranuclear Ni(II) complexes [Ni4(L2)4(CH3OH)4] (2), [Ni4(o-vanillinate)4(μ3-N3)4(CH3OH)4] (3) have been synthesized and structurally characterized. All the three complexes 1, 2, and 3 have been characterized by elemental analysis, FTIR, and single crystal X-ray diffraction studies. Single crystal X-ray diffraction studies reveal that all three complexes consist of a cubane core in which the four Cu(II)/Ni(II) centers in 1 and 2 are linked by μ3-alkoxo bridges and Ni(II) ions in 3 are linked by azido bridge in end-on fashion. The skeleton structures of the cubane cores are all distorted from the idealized cube and most show a further distortion. The variable-temperature (2–300K) magnetic susceptibilities and magnetizations of the three compounds were measured. Variable-temperature magnetic susceptibility data exhibit dominant antiferromagnetic interaction in complex 1 while ferromagnetic interactions in complexes 2 and 3.

New azido-substituted tantalum compounds: syntheses and DFT examination of nitrogen-rich mono-, di-, and trinuclear tantalum(v) compounds

The syntheses of new tantalum compounds containing an ancillary azido ligand(s) are described. The tantalum compound with the composition Ta(NMe2)4(N3) has been synthesized in high yield from the reaction of TaCl(NMe2)4 with NaN3 in THF. The solid-state structure reveals a dimeric architecture based on Ta2(NMe2)8(μ-N3)2 (), where the eight-membered dimetallocyclic ring possesses a chair-like conformation with bridging azido ligands binding the two Ta(NMe2)4 moieties. Solution molecular weight measurements and electronic structure calculations predict to exist as a monomer at room temperature. reacts with the formamidine (i)PrNC(H)NH(i)Pr to furnish fac-Ta(NMe2)3(η(1)-N3)[(i)PrNC(H)N(i)Pr] () and Me2NH; compound has been characterized by IR and (1)H NMR spectroscopy and X-ray diffraction analysis. Treatment of with p-toluidine affords the trinuclear compound Ta3(NMe2)5(μ-NMe2)(μ-NC6H4Me-4)2(NC6H4Me-4)(μ-N3)2(η(1)-N3) (). Compound contains three non-bonded tantalum atoms that are ligated by edge-bridging imido, amido, and azido ligands. The molecular structure of has been determined by X-ray crystallography, and the unprecedented presence of terminal and bridging imido, amido, and azido ligands in a single tantalum compound confirmed. The bonding in has been examined by DFT, and these data are discussed relative to the crystallographic structure. Compounds represent the first structurally characterized examples of heteroleptic tantalum compounds that possess an all-nitrogen coordination sphere with at least one azido ligand.

Assembly of Co(ii)/Cu(ii)–azido polynuclear polymers: structural diversity and magnetic behavior

Hydrothermal reaction of cyano-substituted viologen derivatives and NaN3 with corresponding metal salts in the presence/absence of H2PTA (H2PTA = p-phthalic acid) yielded three azide-based polynuclear coordination polymers: [Co4(N3)4(PTA)3(4-CV)2]n·2nH2O 3D (1), [Co4(N3)4(PTA)3(3-CV)2]n·nH2O 3D (2), and [Cu6(N3)14(4-CV)2]n 2D (3) (3/4-CV+ = 4,4′-bipyridinium-N-methyl-3/4-benzonitrile). The azido bridges are employed to construct two types of polynuclear cluster units: tetranuclear [Co4(μ1,1-N3)4] and hexanuclear [Cu6(μ1,1-N3)6(μ1,1,1-N3)4]. Polymers 1 and 2 are isostructural, and exhibit similar 3D frameworks constructed by unprecedented linear tetranuclear CoII4 units with a four-connected 65·8 topology. Polymer 3 features a 2D (4,4) topological network built up by hexanuclear CuII6 segments. The azide anion exhibits diverse coordination modes: μ1,1-N3 in 1 and 2, and μ1,1-, μ1,3-, μ1,1,1- and μ1,1,3-N3 in 3. Variable-temperature magnetic susceptibility data denote that 1 and 2 display a weak antiferromagnetic interaction in CoII4 units and 3 shows a dominant ferromagnetic exchange in CuII6 units.

Five new pseudohalide bridged Mn(II) complexes of pyrimidine derived Schiff base ligands: Synthesis, crystal structures and magnetic properties

Four new azide bridged dinuclear Mn(II) complexes [Mn(L1)(μ1,1-N3)(N3)]2 (1), [Mn(L2)(μ1,1-N3)(N3)]2 (3), [Mn(L3)(μ1,1-N3)(N3)]2[(N3)Mn(L3)(μ1,1-N3)(N3)]2 (4) and [Mn(L4)(μ1,1-N3)(N3)]2[Mn(L4)(μ1,1-N3)(N3)]2 (5) and one new dicynamide bridged binuclear Mn(II) complex {[Mn2(L1)2(dca)2(H2O)2(μ1,5-dca)](ClO4)} (2) have been synthesized using the pyrimidine derived primary Schiff base ligands Ln (n=1–4), with azide and dicynamide as bridging ligands. All the five complexes were characterized by elemental analyses, IR spectroscopy and single crystal X-ray crystallography, together with magnetic measurements of 1–4. The tridentate Schiff base ligands are the [1+1] condensation products of 2-hydrazino-4,6-dimethyl pyrimidine with 2-acetyl pyridine, pyridine-2-carbaldehyde, 2-benzoyl pyridine and di(2-pyridyl) ketone for Ln (n=1–4), respectively. All the complexes except 2 contain Mn(II)-azido links in which the Mn(II) centres are bridged by a di-μ1,1-azido (double EO) group. The double EO bridging fragments in the complexes are similar with bridging angles (Mn–N–Mn) ranging from 102.59° to 104.81°. Magnetic property studies reveal that in 1, 3 and 4 intramolecular ferromagnetic interactions are mediated through the EO azido bridges with J parameters in the range 4.3–5.12cm−1, while a weak antiferromagnetic interaction prevails in 2 (J=−0.12cm−1) via μ1,5-dicynamide bridges. In addition, complexes 1, 3 and 4 show weak intermolecular antiferromagnetic interactions (J=−0.025 to −0.027cm−1).

Versatility of Azide in Serendipitous Assembly of Copper(II) Magnetic Polyclusters

Engineering at the molecular level is one of the most exciting new developments for the generation of functional materials. However, the concept of designing polynuclear extended structures from bottom up is still not mature. Although progress has been made with secondary building units (SBUs) in metal organic frameworks (MOFs), the control seems to be just an illusion when it comes to bridging ligands such as the azide ion. When we say that the azido ligand is versatile in its bridging capabilities, what we mean is that it would be difficult to predict or control its bridging properties. However, this kind of serendipity is not always bad news. For example, scientists have shown that the azido ligand can mediate magnetic exchanges between paramagnetic metals in a predictable fashion (usually depending upon the bonding geometries). Therefore, it is a well-respected ligand in polynuclear assemblies. Serendipitous assemblies offer new magnetic structures that we may not otherwise even think about synthesizing. The azido ligand forms a variety of complexes with copper(II) using different blocking amines or pyridine based ligands. Its structural nature changes upon changing the substitution on amine, as well as the amount of blocking ligand. In principle, if we take any of these complexes and provide more coordination sites to the bridging azido ligands by removing a fraction of the blocking ligands, we can get new complexes with intricate structural networks and therefore different magnetic properties with the same components as used for the parent complex. In this Account, we mainly discuss the development of a number of new topological and magnetic exchange systems synthesized using this concept. Not all of these new complexes can be grouped according to their basic building structures or even by the ratio of the metal to blocking ligand. Therefore, we divided the discussion by the nuclearity of the basic building structures. Some of the complexes with the same nuclearities have very similar or even almost identical basic structures. However, the way these building units are joined together (by the azido bridges) to form the overall extended structures differ almost in every case. The complexes having the Cu6 core are particularly interesting from a structural point of view. Although they have almost identical basic structures, some of them are extended in three dimensions, but two of them are extended in two dimensions by two different bridging networks. In the complexes having linear Cu4 basic units, we find that using similar ligands does not always give the same bridging networks even within the basic building structures. These complexes have also enriched the field of molecular magnetism. One of the complexes with a Cu3 building unit has provided us with the opportunity to study the competing behavior of two different kinds of magnetic exchange mechanism (ferromagnetic and antiferromagnetic) acting simultaneously between two metal ions. Through density functional theory calculations, we showed how they work independently and their additive nature to produce the overall effect. The exciting methodology for the generation of copper(II) polyclusters presented in this Account will provide the opportunity to explore analogous serendipitous assembly of diverse structures with interesting magnetic behavior using other transition metal ions having more than one unpaired electrons.

Synthesis, X-ray crystal structure, and electrochemistry of polynuclear azido-bridged manganese(III) and copper(II) Schiff base complexes

Abstract New azido-bridged [MnIII(salabza)(μ-1,3-N3)]n (1), and [CuII4(salabza)2(μ-1,1-N3)2(N3)2(HOCH3)2],(2) complexes with an unsymmetrical Schiff base ligand, {H2salabza = N,N’-bis(salicylidene)-2-aminobenzylamine}, have been synthesized, characterized by spectroscopic and electrochemical methods, and their crystal structures have been determined by X-ray diffraction. In complex 1, each manganese(III) atom is coordinated with N2O2 donor atoms from salabza and two adjacent Mn(III) centers are linked by an end-to-end (EE) azide bridge to form a helical polymeric chain with octahedral geometry around the Mn(III) centers. Complex 2 is a centrosymmetric tetranuclear compound containing two types of Cu(II) centers with square pyramidal geometry. Each terminal copper atom is surrounded by N2O2 atoms of a salabza ligand, and the oxygen atom of the methanol molecule. Each central copper(II) ion is coordinated with two phenoxo oxygen atoms from one salabza, one terminal azido, and two end-on (EO) bridging azido ligands. The central copper(II) ions are linked to each other by the two end-on (EO) azido groups.

Copper(II)–azido complexes constructed from polypyridyl amine ligands

A novel 1-D polymer Cu(II) complex bridged by perchlorate ions and azide ligand with the structural formula [Cu(DPA)(N3)(μO,O–ClO4)]n (1), {[Cu(Ldpdmen)(μ1,3-N3)]ClO4}n (2), {[Cu2(μ-Lpy)(μ-1,1,3-N3)(μ-1,3-N3)](ClO4)2}n (3) and {[Cu2(LT)(μ2-1,3-N3)(N3)(H2O)](ClO4)2H2O}n (4) where DPA=di(2-pyridylmethyl)amine, Ldpdmen=N,N′-bis(2-pyridylmethyl)-N,N′-dimethylethylenediamine and Lpy=2,6-bis[bis(2-pyridylmethyl)aminomethyl]pyridine and LT=3,5-bis[bis(2-pyridylmethyl) aminomethyl]toluene were synthesized. The complexes were characterized by spectroscopic techniques (IR and visible) and by single crystal X-ray crystallography. The magnetic properties were also measured for 1–3 at variable temperatures (4.5–300K). Compound 1 has the copper center in a 4+2 geometry with the equatorial plane formed through the three N-donors of the DPA and an azido group which acting as a monodentate ligand. The 1-D chain is generated via the axial O,O′-bridging perchlorato groups where the intra-chain Cu⋯Cu distance is 6.9416(16)Å. In complex 2, the Cu center is ligated by the four N-donor atoms of Ldpdmen amine ligand and two N atoms of the EE bridging azido groups in a cis-coordinated asymmetric EE bonding fashion. The intra-chain Cu⋯Cu distance in this complex is 5.7949(15)Å.

Synthesis, Structures, and Magnetic Properties of Two Tetranuclear Copper Complexes with End‐on Azido and Phenoxo Bridges Containing Chiral Schiff Base Ligands

AbstractThe copper complexes [Cu4(μ‐L1)2(μ1, 1‐N3)2·(CH3O)2] (1) and [Cu4(μ‐L2)2(μ1, 1‐N3)2(N3)2]·(H2O)2 (2) [H2L1 = (1R,3S)‐N′,N′′‐bis[salicylidene]‐1, 3‐diamino‐1, 2, 2‐trimethylcyclopentane and H2L2 = (1R,3S)‐N′,N′′‐bis[5‐methylsalicylidene]‐1, 3‐diamino‐1, 2, 2‐trimethylcyclopentane] were synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single crystal X‐ray diffraction. Both are tetranuclear complexes consisting of dinuclear copper moieties [Cu2L1]2+ or [Cu2L2]2+ connected by two end‐on azido bridges. Low temperature magnetic studies indicate that weak antiferromagnetic couple dominates in 1 and 2.

Synthesis and characterization of Mn(II) and Zn(II) azido complexes with halo-substituted pyridine derivative ligands

The synthesis, IR spectra and single-crystal structures of two Mn(II) and one Zn(II) azido complexes with halo-substituted pyridine derivative ligands are reported: [Mn(N3)-2(3-Brpy)2(H2O)]2(3-Brpy)2 (1), [Mn(N3)2(3-Brpy)2] n (2) and [Zn(N3)2(3-amino,2-chloropyridine)] n (3) with 3-Brpy = 3-bromopyridine. In the dinuclear Mn(II) complex 1 and polymeric 1D Zn(II) complex 3, di-EO only azido bridges exist, whereas in the polymeric Mn(II) 1D system of 2, a rather less common di-EO/di-EO/di-EE azido bridging sequence has been observed (EO = end-on, EE = end-to-end). The halo-substituted pyridine derivatives act in the three compounds as terminal ligands and in 1 also as solvent molecules.

A new end-on azido bridged MnIII single-chain magnet and its dimeric single molecule magnet polymorph. Synthesis, structure and magnetic properties of [Mn(5-Clsalpn)N3]n and phenoxo bridged [Mn(5-Clsalpn)N3

An end-on azido bridged Mn(III) coordination chain polymer [Mn(5-Clsalpn)N3]n (complex 1) and its dimeric polymorph, [Mn(5-Clsalpn)N3]2 (complex 2), where 5-Clsalpn is N,N'-bis(5-chlorosalicylidene)-1,3-diaminopropane, were prepared. Complex 1, which is obtained as two concomitant polymorphs (1a and 1b) with nearly identical molecular structures but different crystal packing, has μ-1,1(end-on) azido bridges. This single atom bridge is unsymmetrical and leads to a -1 cm(-1) antiferromagnetic interaction among Mn(III) centers of the one-dimensional coordination polymer. Mn(III) anisotropy is manifested through Jahn-Teller elongation along the N(azido)-Mn-N(azido) axis, and results in single-chain magnet behavior. The phenoxo-bridged dimer (complex 2) has terminal azido ligands and a ferromagnetic interaction is mediated by the unsymmetrical bis-phenoxo bridge. Mn(III) anisotropy is manifested through Jahn-Teller elongation along an N-Mn-O axis, and results in single molecule magnet behavior. The dimers are organized into a two-dimensional network structure via Cl···Cl and Cl···H-phenyl interactions which are also ferromagnetic.