A coordination polymer consisting of two different one-dimensional copper(II) chains.

The title compound, catena-poly[[[diaqua(methanol-κO)copper(II)]-µ-N-(4-methylpyrimidin-2-yl-κN(1))pyrazin-2-amine-κ(2)N(1):N(4)] [[aqua(aqua/methanol-κO)(perchlorato-κO)copper(II)]-µ-N-(4-methylpyrimidin-2-yl-κN(1))pyrazin-2-amine-κ(2)N(1):N(4)] tris(perchlorate) methanol monosolvate 1.419-hydrate], {[Cu(C9H9N5)(CH3OH)(H2O)2][Cu(C9H9N5)(ClO4)(CH3OH)0.581(H2O)1.419](ClO4)3·CH3OH·1.419H2O}n, is a one-dimensional straight-chain polymer of N-(4-methylpyrimidin-2-yl)pyrazin-2-amine (L) with Cu(ClO4)2. The complex consists of two crystallographically independent one-dimensional chains in which the Cu(II) atoms exhibit two different octahedral coordination geometries. The L ligand coordinates to two Cu(II) centres in a tridentate manner, with the pyrazine ring acting as a bridge linking the Cu(II) coordination units and building an infinite one-dimensional chain. Extensive hydrogen bonding among perchlorate anions, water molecules and L ligands results in three-dimensional networks.

Bis(morpholin-4-ium) tetra-chlorido-cobalt(II).

The title compound, (C(4)H(10)NO)(2)[CoCl(4)], is an ionic compound consisting of two protonated tetra-hydro-1,4-oxazine (morpholine) cations and a [CoCl(4)](2-) dianion. The Co(II) ion is in a tetra-hedral coordination geometry. The cations exhibit chair-shaped conformations. A three-dimensional supra-molecular architecture is formed through N-H⋯Cl and C-H⋯Cl hydrogen bonds between the dianions and the cations.

Probing the electronic communication of linear heptanickel and nonanickel string complexes by utilizing two redox-active [Ni2(napy)4]3+ moieties.

Two extended nickel string complexes, [Ni(7)(bnapy)(4)Cl(2)](Cl)(2) (2) and [Ni(9)(bnapya)(4)Cl(2)](PF(6))(2) (3) (bnapy(2-) = 2,6-bis(1,8-naphthyridylamido)pyridine and bnapya(3-) = bis(6-(1,8-naphthyridylamido)pyridyl)amido), which possess two redox-active [Ni(2)(napy)(4)](3+) units, were synthesized and characterized. The electronic communication between the two redox-active units in both complexes can be investigated not only by magnetic measurements but also by analyzing the difference between two consecutive one-electron oxidation peaks (DeltaE(1/2)) of 2 and 3. The antiferromagnetic coupling between the two [Ni(2)(napy)(4)](3+) fragments become weaker as the metal frameworks are elongated (J = -13.21 and -1.48 cm(-1) for 2 and 3, respectively). Moreover, the DeltaE(1/2) values of 2 and 3 are 110 and 84 mV, respectively, which are smaller than that (300 mV) of their pentanickel analogue [Ni(5)(bna)(4)(Cl)(2)](PF(6))(2) (bna(-) = bisnaphthyridylamido) (1). These DeltaE(1/2) values indicate that the electronic communication decreases with increasing number of inner diamagnetic nickel ions in nickel string complexes.

First stable reduced form of [Co(5)](+10): fine tuning of linear pentacobalt(ii) complexes containing delocalized metal-metal bonds through ligand modification.

Pentacobalt EMACs [Co(5)(mu(5)-dpzpda)(4)X(2)] (X = Cl(-) (), NCS(-) ()) with fine-tuning of the supporting ligand based on the tripyridyldiamine ligand, N,N'-di(pyrazin-2-yl)pyridine-2,6-diamine (H(2)dpzpda), and their reduced form (Ph(4)P)[Co(5)(mu(5)-dpzpda)(4)X(2)] (X = Cl(-) (), NCS(-) ()) were first synthesized and structurally characterized. The structures of showed direct Co-Co bonds with Co-Co distances in the range 2.2385(7)-2.2888(15) A, and valence electrons delocalized through the whole metal chain with distances of longer than 9.06 A. The distances of the inner Co-Co bonds and the Co-axial ligands became longer after reduction, whereas no significant change was observed in the distances of the outer Co-Co bonds and Co-N (supporting ligand) bonds, which was consistent with the MO analysis. Electrochemical studies on both and showed one reversible oxidation and one reversible reduction at E(1/2) = +0.82 and -0.05 V for , and at E(1/2) = +0.89 and +0.02 V for , respectively. The redox reactions of the thiocyanate complex happened at higher potentials than the chloride complex . A magnetism study of revealed anomalous magnetic behaviour similar to that of heptacobalt EMACs, and a deviation from the Curie-Weiss law was observed. The chi(M)T value at 300 K is 0.84 and 1.16 emu K mol(-1) for and , respectively, suggesting spin-equilibrium or a spin-admixture between doublet and quartet states arising from the Boltzmann distribution over different energy levels. Similar results were obtained for and , showing intermediate chi(M)T values between a diamagnetic and a triplet state of 0.15-0.96 emu K mol(-1) in the temperature range 5-300 K. The structural and magnetic results were interpreted through an EHMO study.

New versatile ligand family, pyrazine-modulated oligo-alpha-pyridylamino ligands, from coordination polymer to extended metal atom chains.

Here we designed and synthesized a new ligand, di(2-pyrazyl)amine (Hdpza) (1) and studied its coordination modes and the corresponding complexes with Cu(II), Co(II), Ni(II) and Cr(II). Hdpza is an analogue of the well-studied di(2-pyridyl)amine (Hdpa) ligand, which was used to generate the first extended metal atom chain. Three types of coordination modes were found: anti-anti style which resulted in a mononuclear compound [Cu(Hdpza)(2)(H(2)O)(2)](ClO(4))(2) (2); anti-syn which was observed in a complex for the first time and resulted in a 2-D coordination polymer [Co(mu(2)-Hdpza)(2)(NCS)(2)] (3); and syn-syn type which was observed in extended metal atom chains [Ni(3)(mu(3)-dpza)(4)Cl(2)] (4), [Ni(3)(mu(3)-dpza)(4)(NCS)(2)] (5) and [Cr(3)(mu(3)-dpza)(4)Cl(2)] (6). Weak antiferromagnetic coupling via Hdpza was observed in 3, whereas magnetic studies on extended metal atom chains 4 and 5 revealed that the interaction parameter was more than -200 cm(-1). Electrochemistry showed that the extended metal atom chains 4-6 are much more stable to oxidation than the Hdpa complexes, and are able to undergo reduction.

The nano-scale molecule with the longest delocalized metal-metal bonds: linear heptacobalt(II) metal string complexes [Co7(micro7-L)4X2].

A new type of pyrazine-modulated oligo-alpha-pyridylamino ligands, N2-(pyrazin-2-yl)-N6-(6-(pyrazin-2-ylamino)pyridin-2-yl)pyridine-2,6-diamine (H3pzpz) and N2-(pyrazin-2-yl)-N6-(6-(pyridin-2-ylamino)pyridin-2-yl)pyridine-2,6-diamine (H3tpz), were synthesized and characterized by IR, 1H NMR and MS(FAB). Using and , the linear heptacobalt(II) metal string complexes [Co7(micro7-L)4X2] (L=pzpz3-, X=Cl-, NCS-; L=tpz3-, X=Cl-, X=NCS-) were synthesized and structurally characterized. The structures showed the shortest Co-Co distance (2.194 A) and the longest Co chain (13.5 A) obtained to date with direct Co-Co bonds. The Co-Co distances are in the range 2.194-2.309 A. Electrochemical studies showed two reversible oxidations and one reversible reduction, while all the redox reactions of H3pzpz complexes, and , occurred at higher potentials than H3tpz complexes, and . The complexes are fairly stable to oxidation. Temperature-dependent magnetic research on revealed anomalous magnetic behavior with intermediate magnetic moment values between quartet and doublet states, and deviation from the Curie-Weiss law.