Search results for "dicyanamide"
showing 10 items of 82 documents
Multiple spin phases in a switchable Fe(ii) complex: polymorphism and symmetry breaking effects
2018
Polymorphism in spin-crossover (SCO) compounds allows accessing additional forms of switchable materials with diverse transition properties. We have prepared three polymorphs of a new complex [FeLBr(dca)2], where LBr is N,N′-bis[(5-bromo-2-pyridyl)methyl]ethane-1,2-diamine and dca is dicyanamide. They display different SCO properties: the α-form displays a hysteretic one-step switch centered at 134 K, the β-form undergoes hysteretic two-step spin transition with a plateau (T1/2 = 153 and 144 K) and the γ-form remains high spin (HS) over the whole temperature region. The kinetic origin of the hysteresis loop was demonstrated in temperature rate dependent magnetic measurements. Spin transitio…
Single-ion magnet behaviour in mononuclear and two-dimensional dicyanamide-containing cobalt(ii) complexes.
2016
Three cobalt(II) complexes of formulae [Co(dca)2(bim)4] (1), [Co(dca)2(bim)2]n (2) and [Co(dca)2(bmim)2]n (3) [dca = dicyanamide, bim = 1-benzylimidazole and bmim = 1-benzyl-2-methylimidazole] were prepared and structurally analyzed by single-crystal X-ray crystallography. Compound 1 is a mononuclear species where the cobalt(II) ion is six-coordinate with four bim molecules in the equatorial positions [Co–Nbim = 2.1546(15) and 2.1489(15) A] and two trans-positioned dca ligands [Co–Ndca = 2.1575(18) A] in the axial sites of a somewhat distorted octahedral surrounding. The structures of 2 and 3 consist of two-dimensional grids of cobalt(II) ions where each metal atom is linked to the other fo…
Hybrid materials containing organometallic cations and 3-D anionic metal dicyanamide networks of type [Cp*2M][M′(dca)3]
2004
A new series of hybrid materials of type [Cp*2M][M′(dca)3] has been prepared by cation templation and structurally characterised (M = Fe(III), Co(III); M′ = Mn(II), Fe(II), Co(II), Ni(II), Cd(II); dca− = N(CN)2−). The crystallographic analysis of [Cp*2Fe][Cd(dca)3] showed that the [Cd(dca)3]− anionic framework is of a symmetrical 3-D α-polonium type, containing octahedral Cd nodes and μ1,5-dca bridging ligands. The [Cp*2Fe]+ cations occupy the cube-like cavities within the framework. The cationic and anionic-framework sublattices remain magnetically independent and display susceptibilities, over the range 300 to 2 K, of a Curie–Weiss nature obtained by adding a S = 1/2 (Cp*2Fe+) or a S = 0 …
Influence of the pyrazine substituent on the structure and magnetic properties of dicyanamide-bridged cobalt(ii) complexes.
2019
Substituted pyrazines were successfully used to prepare two new coordination polymers of formulas {[Co(dca)2(NH2pyz)2]·H2O}n (1) and [Co3(dca)6(HOpyz)5(H2O)2]n (2) [dca = dicyanamide, NH2pyz = 2-aminopyrazine and HOpyz = 2-hydroxypyrazine] whose structures were determined by single-crystal X-ray crystallography. The structure of 1 consists of a two-dimensional rhombus grid of cobalt(II) ions where the dca ligand adopts the μ1,5 bridging mode with trans-positioned monodentate NH2pyz molecules completing the six-coordination around each metal ion. Compound 2 exhibits a stair-like two-dimensional structure where the intralayer connections are performed by the dca and HOpyz groups exhibiting μ1…
Synthesis, X-ray crystal structure and magnetic study of a μ 1,5-dca bridged ferromagnetic dimeric copper(II) complex
2008
Reaction of Cu(NO3)2 · 3H2O, 1-(N-salicyalideneimine)-2-(N,N-dimethyl)-aminoethane (HL1), LiClO4, and sodium dicyanamide (Nadca) in aqueous medium affords a dimeric complex [Cu2(L1)2 (μ1, 5-dca)](ClO4) (1). Single crystal X-ray analysis reveals that 1 is dinuclear with copper(II) ions bridged by a single dicyanamide group in end-to-end fashion. The coordination environment around copper(II) is square planar. Two nitrogens and oxygen of the tridentate Schiff-base ligand (HL1) occupy three coordination sites of the square plane while the remaining site is occupied by the nitrogen of a terminal nitrile of the bridging dca. The nitrogen of the other terminal nitrile group of the μ1,5-dca ligand…
Solid- and solution-state studies of the novel mu-dicyanamide-bridged dinuclear spin-crossover system {[(Fe(bztpen)]2[mu-N(CN)2]}(PF6)3 x n H2O.
2005
The mononuclear diamagnetic compound {Fe(bztpen)[N(CN)2]} (PF6)CH3OH (1) (bztpen = N-benzyl-N,N′,N′- tris(2-pyridylmethyl)ethylenediamine) has been synthesized and its crystal structure studied. Complex 1 can be considered to be the formal pre-cursor of two new dinuclear, dicyanamide-bridged iron(II) complexes with the generic formula {[(Fe(bztpen)]2[μN(CN)2]}(PF6) 3·nH2O (n = 1 (2) or 0 (3)), which have been characterized in the solid state and in solution. In all three complexes, the iron atoms have a distorted [FeN6] octahedral coordination defined by a bztpen ligand and a terminal (1) or a bridging dicyanamide ligand (2 and 3). In the solid state, 2 and 3 can be considered to be molecu …
Spin Crossover in Double Salts Containing Six- and Four-Coordinate Cobalt(II) Ions
2017
The preparation and spectroscopic and structural characterization of three cobalt(II) complexes of formulas [Co(tppz)2](dca)2 (1), [Co(tppz)2][Co(NCS)4]·MeOH (2), and [Co(tppz)2][Co(NCO)4]·2H2O (3) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and dca = dicyanamide] are reported here. Compounds 1–3 have in common the presence of the cationic [Co(tppz)2]2+ entity where each mer-tridentate tppz ligand coordinates to the cobalt(II) ion equatorially through two pyridyl donors and axially via the pyrazine, completing the six-coordination. The electroneutrality is achieved by the organic dca group (1) and the anionic tetrakis(thiocyanato-κN)cobaltate(II) (2) and tetrakis(cyanato-κN)cobaltate(II) (3…
Synthesis and characterization of a novel dicyanamide-bridged Co(II) 1-D coordination polymer with a N 4 -donor Schiff base ligand
2017
The synthesis, structure and magnetic properties of a novel Co(II) 1D coordination polymer, [Co(L)(µ1,5-dca)(ClO4)2·MeOH]n (1) are described. Compound 1 contains two independent cationic Co(II) chains (CoA and CoB) which are parallel to the c direction and present short π-π and C-H⋯π interactions with two neighbouring chains along the b direction, giving rise to alternating layers of chains A and B in the bc plane. Variable-temperature magnetic susceptibility measurements shows a weak antiferromagnetic coupling among the adjacent cobalt(II) centres mediated through μ1,5-dca− bridge.
C3-symmetric trinuclear copper(ii) species as tectons in crystal engineering
2013
Three new complexes have been obtained using C3-symmetric trinuclear complexes as tectons; [Cu3(felden)(NCS)3(dmf)3] (1), [Cu3(felden)(mand)3]·(C2H5)2O (2), and [Cu3(felden)(dca)3(C2H5OH)]·2H2O (3) (H3felden is the Schiff base resulting from the condensation of 2,4,6-triformylphloroglucinol with N,N-dimethylethylenediamine, mand− is the anion of the R-mandelic acid and dca− is the dicyanamide anion). Compounds 1 and 2 are discrete trinuclear species, while compound 3 is a 2D coordination polymer, constructed from trinuclear nodes and dicyanamido spacers. The variable-temperature magnetic properties of 1–3 have been investigated and they reveal the occurrence of weak antiferromagnetic intera…
Influence of the central metal ion in controlling the self-assembly and magnetic properties of 2D coordination polymers derived from [(NiL)2M]2+ node…
2014
Three new 2D coordination polymers (CPs) 2∞[(NiL)2Ni(μ1,5-N(CN)2)2]n (1), 2∞[(NiL)2Cd(μ1,5-N(CN)2)2]n (2) and 2∞[(NiL)2Zn(μ1,5-N(CN)2)2]n (3) have been synthesized by reacting a [NiL] “metalloligand” (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine) with three different metal(II) (Ni, Cd and Zn) perchlorates and sodium dicyanamide, with identical molar ratios of the reactants. All three products have been characterized by IR and UV-Vis spectroscopies, elemental analyses, powder and single crystal X-ray diffraction and variable temperature magnetic measurements. The isomorphous compounds 1 and 2 consist of similar [(NiL)2M(μ1,5-N(CN)2)] (M = Ni for 1 and Cd for 2) angular trinuclear un…