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The preparation of a series of multidentate pyridyl-imine ligands, L1-L3, and their reactivity with the MnII/N3- system is described (L1 = [N,N-bis(pyridine-2-yl)benzylidene]ethane-1,2-diamine; L2 = [N,N-bis(pyridine-2-yl)benzylidene]propane-1,3-diamine, and L3 = [N,N-bis(pyridine-2-yl)benzylidene]butane-1,4-diamine). Complexes comprising dinuclear end-on bis(µ-azido)-bridged manganese(II) units of formulas [Mn2(L1)2(N3)4][Mn2(L1)2(N3)2(CH3OH)2](CIO4)2 (two cocrystallized dinuclear units, 1.2), [Mn2)(L2)2(N3)2](ClO4)2 (3), and [Mn2(L3)2(N3)2](ClO4)2 (4) have been synthesized. The crystal structures of complexes 1-4 as well as their magnetic properties are presented. Each manganese atom of cocrystallized complexes in compound 1.2 is heptacoordinated, displaying Mn-N-Mn angles, θ, of 102.53(12) and 101.70(12)° and Mn···Mn distances of 3.5091(7) and 3.4680(7) Å. On the other hand, each manganese center in compounds 3 and 4 is located within an octahedral coordination environment, the complexes displaying θ angles of 104.29(11) and 103.60(18)°, respectively, and Mn···Mn vectors of 3.5371(7) and 3.5338(10) Å, respectively. Magnetic susceptibility studies revealed the presence of intramolecular ferromagnetic superexchange, yielding an S = 5 spin ground state in all complexes. Fitting of the experimental data led to coupling constants, intermolecular exchange values, and g factors (in the J/zJ'/g format) of 0.77 cm-1/0.01 cm-1/ 2.20 (1.2), 2.04 cm-1/0.01 cm-1/1.99 (3), and 1.75 cm-1/-0.05 cm-1/2.04 (4), respectively (using H = -2JS1S2 as the convention for the Heisenberg spin-Hamiltonian). These results are consistent with predictions from recent DFT calculations performed on end-on bis(µ-N3-)-bridged MnIII dinuclear complexes. A plot of experimental J vs θ, including data from the only preexisting compound of this kind, reveals a linear relationship, which could be the first evidence of a possible magneto-structural correlation between these two parameters. [ABSTRACT FROM AUTHOR]

Abstract: A 1:2:2:6 molar ratio of Cd(NO3)2 ·4H2O, Cu(NO3)2 ·3H2O, tris(2-aminoethylamine) (tren) and NH4NCS in aqueous solution at room temperature affords trinuclear complex of the type [Cu2Cd(tren)2(NCS)6] (1). The complex has been characterised using microanalytical, spectroscopic and magnetic results. X-ray diffraction measurements have been made to define the coordination sphere and long-range structure. 1 consists of two pentacoordinated copper(II) occupied by tren N atoms and one bridging SCN− N atom of the central trans-[Cd(NCS)4(SCN)2]4− molecular ion which bridges by the 1,3-thiocyanate. Each of these trinuclear units are engaged in intra as well as intermolecular N–H⋯S hydrogen bonding. Variable-temperature magnetic study shows no significant magnetic interactions among the metal ions. [Copyright &y& Elsevier]

Abstract: MnCl2 ·4H2O, Cu(NO3)2 ·3H2O, tris(2-aminoethyl)amine (tren) and NH4NCS in a 1:4:4:10 molar ratio in aqueous solution results a bimetallic compound of the type [Cu(tren)(NCS)]4[Mn(NCS)6] (1) which has been characterized by microanalytical, physicochemical, spectroscopic and magnetic results. The structure of the complex is determined by X-ray diffraction study. Some pertinent crystal data are: monoclinic, space group P21/c, a =11.0442(9)Å, b =14.4923(12)Å, c =19.2505(16)Å, β =91.95(10)°, and Z =4. The crystal structure consists of a hydrogen bonded 3D network of [Cu(tren)(NCS)]+ and [Mn(NCS)6]4− ions. Manganese(II) has an MnN6 chromophore bound by six N atoms of the terminal thiocyanates. Each copper(II) centre is five coordinated by one N atom of terminal thiocyanate and four N atoms of the tripod ligand. Four copper(II) units are hydrogen bonded to form a hydrogen bonded tetramer. Each manganese(II) in turn is further engaged in hydrogen bonding to four such tetramers leading to the 3D network. Variable-temperature magnetic study shows no significant magnetic interactions among the metal ions connected by hydrogen bonding. [Copyright &y& Elsevier]

Abstract: Cadmium(II) nitrate tetrahydrate – a metal ion template, tris(2-aminoethyl)amine (tren) – a tripodal amine and thiocyanate – a versatile intermediatary in a 3:2:6 mole ratio in water afford a homopolymer, [Cd3(tren)2(NCS)6] n (1). Replacement of two equivalents of cadmium(II) salt by two equivalents of nickel(II) nitrate hexahydrate results in the heteropolymer, [Ni2Cd(tren)2(NCS)6] n (2). Compound 1 crystallizes in the monoclinic C2/c space group with a =20.3480(17)Å, b =10.8796(9)Å, c =16.3495(10)Å, β =110.009(7)° and Z =4; 2 crystallizes in the same space group as in 1 with a =19.584(5)Å, b =11.034(3)Å, c =15.760(4)Å, β =100.712(4)° and Z =4. 1 and 2 are new examples of homo- and hetero-polymers with the multiconnecting molecular ion bridge [Cd(NCS)6]4− in different geometric configurations. The single crystal X-ray structures of both neutral polymers consist of infinite two-dimensional sheets with two alternating environmentally different octahedral metal ion [M(II)=Ni(II)/Cd(II)] coordination spheres connected by four 1,3-thiocyanato bridging cis-/trans-[Cd(NCS)2(SCN)4]4−. The Cd(1) centres in 1 and 2 with the CdN2S4 chromophore are surrounded by four S atoms of the bridging thiocyanate and two terminal N atoms of the pseudohalide, while the CdN6 chromophore of Cd(2) in 1 and NiN6 chromophore of Ni(1) in 2 are completed by four tren N atoms and two N atoms of the bridging NCS− in cis alignment. In 1, the three tripodal amine N atoms and two bridging S atoms are engaged in strong intermolecular hydrogen bondings, which is responsible for the conformation and stability of the supramolecular network. The absence of such hydrogen bonding in 2 is due to a difference in the orientation of the tripodal amine from that in 1 in the polymeric net. The magnetic property of 2 has been investigated over the 2–300K temperature range. The feature is characteristic of a Curie law for a typical magnetically isolated nickel(II) ion with very weak antiferromagnetic interactions (J <0.01cm−1). The presence of a diamagnetic molecular ion with two 1,3-thiocyanate bridges may be one of the major reasons to hinder effective coupling of the paramagnetic centres. [Copyright &y& Elsevier]

Abstract: Copper perchlorate hexahydrate on reaction with the chelating ligands, N,N′-(bis(pyridin-2-yl)alkylidene)propane-1,3-diamine (bpap) [(py)(R)C(CH2)3–Nwhere py=pyridine; R=H, (bpfp); R=Me, (bpmp); R=C6H5, (bpbp)] and NaN3/NH4NCS in a 1:1:1 mole ratio forms the complexes [Cu(bpap)(N3/NCS)]ClO4 (1a–3b), while cadmium perchlorate hexahydrate/cadmium nitrate tetrahydrate in a 1:1:2 mole ratio produces [Cd(bpap)(N3/NCS)2] (4a–6b). Elemental, spectral, electrochemical and other physicochemical results characterize the complexes. Single crystal X-ray diffraction studies confirm the structure of two representative members, [Cu(bpbp)(N3)]ClO4 (3a) and [Cd(bpbp)(NCS)2] (6b). The complexes of 1a–3b are reduced to [Cu(bpbp)2]ClO4 by ascorbic acid. However, air oxidation of [Cu(bpbp)2]ClO4 in the presence of N3/NCS produces Cu(bpap)(N3/NCS)]ClO4. All the complexes display intraligand 1(π–π*) fluorescence and intraligand 3(π–π*) phosphorescence in glassy solutions (MeOH at 77 K). [Copyright &y& Elsevier]

Abstract: Four complexes of the type [Mn(dpa)2(X)2]·H2O (dpa=2,2′-dipyridylamine; ; X=NCO−, 2) and [Mn(dpa)2(X)(OH2)]ClO4 (; X=NCO−, 4) have been synthesized using single-pot reactions of manganese(II) salt, dpa and X in 1:2:2 and 1:2:1 molar ratios, respectively. The compounds have been characterized by microanalytical, physicochemical, spectroscopic and magnetic results. Room temperature magnetic moments (μ eff) are in the range 5.88–5.97 BM and are typical of high-spin manganese(II) complexes ( idealized, S =5/2). The complexes display a Mn(III)–Mn(II) couple at ∼0.6 V versus SCE in DMF solutions. X-ray structure determinations show that in 1–4 the manganese(II) centres are in a distorted octahedral environment. Compounds 1 and 2 contain the MnN6 chromophore, completed by two bidentatendpa units and two terminal azido groups in 1 or N-coordinated cyanato ligands in 2, along with a water of crystallization. In 3 and 4, one water molecule acts as a coordinating ligand replacing one of the terminal pseudohalides in 1 and 2, respectively, resulting in a MnN5O chromophore. The amine H, terminal azido N or cyanato O, O and H’s of the water molecule are engaged in extensive hydrogen bonding of the type N–H⋯N, O–H⋯N and N–H⋯O in 1 and 2. Additionally O–H⋯O bonding is observed in 3 and 4. Supramolecular 2D sheet structures are obtained arising from such weak intermolecular forces. All the complexes display high-energy intraligand 1(π–π*) fluroscence and intraligand 3(π–π*) phosphorescence in glassy solutions (DMF at 77 K). [Copyright &y& Elsevier]

The synthetic details, characterization data and single crystal X-ray structural analyses of [Zn(dpa)(N3)2] (1) and [Zn(dpa)(N3)(NO3)]2 (2) (dpa=2,2′-dipyridylamine) are described. Structural study reveals that the zinc(II) centre in 1 is in a pseudotetrahedral ZnN4 environment ligated by two terminal azide N atoms and two pyridine N atoms of the chelator. The coordination polyhedron around each metal ion in dinuclear 2 is best described as a ZnN4O2 distorted octahedron linked by two end-on azido bridges. The mononuclear units in 1 are engaged in bifurcated intermolecular hydrogen bonding (N–H…N) between amine N of dpa and coordinated N of azide along with aromatic π–π stacking leading to a 2D sheet. In 2, the dinuclear units participate in intermolecular N–H…O hydrogen bonding between amine N of dpa and bound O of bidentate nitrate in combination with π–π interactions resulting to a 3D supramolecular continuum. 1 and 2 display high energy intraligand 1(π–π*) fluorescence and intraligand 3(π–π*) phosphorescence in glassy solutions (DMF at 77 K). A band (372 nm) observed for both 1 and 2 in their solid-state emission spectra is an excimeric emission arising due to aromatic π–π interaction. The role of dpa, a tailored diimine (–N&z.dbnd6;C, upper limit | –NH–C, upper limit | &z.dbnd6;N–) in 1 and 2 is discussed towards functionalisation on crystal engineering and luminescence behaviour. [Copyright &y& Elsevier]