Bipyridinium array-type porous polymer displaying hydrogen storage, charge-transfer-type guest inclusion, and tunable magnetic properties.

A multifunctional pillared-layer porous coordination polymer, {[Mn(2)(Bpybc)(ox)(2)]8 H(2)O}(n), has been constructed based on a flexible viologen derivative, 1,1'-bis(4-carboxybenzyl)-4,4'-bipyridinium dichloride (H(2)BpybcCl(2)), and an oxalate (ox) coligand. Single-crystal X-ray analysis reveals that the compound possesses multichannels with dimensions of about 6.1x6.6 A along the [110] and [-110] directions and 4.2x7.6 A along [100], and a void space of about 41.4 %. Hydrogen adsorption measurements at 77 K and 1 atm indicate that the compound exhibits a hydrogen uptake of 0.71 wt %. Owing to the incorporation of bipyridinium acceptor units, the compound can selectively accommodate aromatic donors into its nanosized pores based on charge-transfer interactions in an elastic way, and afford a specific color to different guests. Furthermore, the effect of perturbation exerted by the guest molecules on its magnetic properties has been investigated. The results indicate that the donor inclusion has little effect on its antiferromagnetic behavior, whereas dehydration of the compound decreases the strength of the magnetic exchange couplings and results in a change of the antiferromagnetic transition temperature from 14.7 to 9.8 K.

Novel polythreaded coordination polymer: from an armed-polyrotaxane sheet to a 3D polypseudorotaxane array, photo- and thermochromic behaviors.

A novel coordination compound, {[Cd(BDC)(Bpybc)(1.5)].10H(2)O}(n), obtained by the reaction of CdCl(2) with 1,1'-bis(4-carboxybenzyl)-4,4'-bipyridinium dichloride (H(2)BpybcCl(2)) and 1,4-benzenedicarboxylic acid (H(2)BDC), contains 1D polymeric chains that are comprised of alternating rings and rods and dangling lateral arms. These 1D polymeric motifs are interlaced via rotaxane-like mechanical linkages to give 2D armed-polyrotaxane sheets, which are further mutually polythreaded via pseudorotaxane-like mechanical linkages to form a 3D polypseudorotaxane array. Notably, a sandwich-type donor-acceptor-donor stacking is formed within each ring as a consequence of both types of polythreading in this species, and photoinduced and thermal-induced reduction of bipyridinium occurs with a color change from light yellow to blue.

A series of manganese-carboxylate coordination polymers exhibiting diverse magnetic properties.

The hydrothermal reactions of an asymmetrical 4-(4-carboxyphenylamino)-3,5-dinitrobenzoic acid (H2cpdba), MnCl2.4H2O, or together with 2,2'-bipyridine (2,2'-bpy) or 4,4'-bipyridine (4,4'-bpy) afford three novel molecule-based magnetic coordination polymers [Mn(cpdba)]n (1), ([Mn2(cpdba)2(2,2'-bpy)2(H2O)2].H2O)n (2) and ([Mn2(cpdba)2(4,4'-bpy)].2H2O)n (3). Compound 1 has a 3D acentric coordination network containing carboxylate-bridged 1D ladder-like manganese chains with spin-canted antiferromagnetism (J = -3.51 cm(-1) for the coupling along the ladder legs, and zJ' = 0.22 cm(-1) for coupling along the ladder rungs), whereas compounds 2 and 3 crystallize in the centrosymmetric space groups P1 and C2/c, respectively. 2 exhibits a 1D chain structure, which is extended into a 3D supramolecular network by pi-pi stacking interactions, while 3 features a quite complex 3D network built up from the cpdba(2-) and 4,4'-bpy spacers as well as the carboxylate-bridged Mn(II) chains. Both 2 and 3 show weak antiferromagnetic coupling interactions (J = -0.55 cm(-1) for 2), and a field-induced spin-flop magnetic transition can also be observed in 2 at ca. 3.2 T at 2 K.

A two-step field-induced magnetic transition in spin-canted systems observed only for the CoII coordination polymer.

Two isostructural 1D compounds {[M3(hpdc)2(H2O)6] 2H2O}n (M = Mn, Co; H3hpde = 2-hydroxypyrimidine-4,6-dicarboxylic acid) were synthesized by the in situ hydrothermal reactions of 2-chloropyrimidine-4,6-dicarboxylic acid with MCl2 (M = Mn, Co) and NaOH; the MnII compound shows spin-canted antiferromagnetism, whereas the CoII compound exhibits the coexistence of spin-canting and a two-step field-induced magnetic phase transition.

Strong electron-accepting methylviologen dication confined in magnetic hosts: synthesis, structural characterization, charge-transfer and magnetic properties of {(MV)2[Ni(SCN)5].Cl.2H2O}n and {(MV)[m(N3)2(SCN)2]}n (M=Mn, Co).

Three hybrid host-guest compounds {(MV)2[Ni(SCN)5].Cl.2H2O}n (1), {(MV)[Mn(N3)2(SCN)2]}n (2) and {(MV)[Co(N3)2(SCN)2}n (3) (where MV2+ = methylviologen dication) have been obtained by self-assembly methods and characterized by X-ray crystallography, spectral methods and magnetic measurements. Compound 1 shows a quasi-two-dimensional structure which is formed by novel single thiocyanate-bridged Ni(II) chains connected through S...S interactions. Compounds 2 and 3 are isostructural, containing single micro(1,3)-azide bridged Mn(II)/Co(II) square layers. MV2+, as a strong electron-acceptor and a template, is embedded between the anionic layers in all three compounds. The charge-transfer (CT) interactions between MV2+ and the anionic hosts have been revealed by structural analysis and UV-vis diffuse reflection spectroscopy. The magnetic studies of the compounds show antiferromagnetic interactions between adjacent metal ions (J = -34.52(7) cm(-1) for 1, J = -3.90(2) cm(-1) for 2 and J = -10.96(6) cm(-1) for 3).

Poly[[hexaaquabis[mu4-2-hydroxy-5-(4-sulfonatophenyldiazenyl)benzoato]dibarium(II)] 4,4'-bipyridine solvate].

The title compound, {[Ba2(C(13)H(8)N(2)O(6)S)2(H2O)6].C(10)H(8)N(2)}n, possesses a novel two-dimensional porous coordination network, in which each Ba(II) ion is nine-coordinated by three carboxylate O atoms, two sulfonate O atoms and four water molecules in an irregular coordination environment. Hydrogen-bond interactions between coordinated water molecules and sulfonate/hydroxyl groups hold the network layers together and produce a three-dimensional supramolecular architecture.

[Co5(mu3-OH)2(btec)2(bpp)]n: a three-dimensional homometallic molecular metamagnet built from the mixed hydroxide/carboxylate-bridged ferrimagnetic-like chains.

A three-dimensional homometallic complex [Co(5)(mu(3)-OH)(2)(btec)(2)(bpp)](n) is built from the mixed hydroxide/carboxylate bridged cobalt(ii) chains linked by the 1,2,4,5-benzenetetracarboxylate (btec(4-)) anion and 1,3-bis(4-pyridyl)-propane molecule (bpp). Within each chain, two mu(3)-OH-bridged metal triangles connect to each other by sharing a common vertex to give rise to a bow-tie type Co(5)(mu(3)-OH)(2) subunit, which is joined to adjacent subunits by four mu(1,1)-carboxylate bridges to form a step-like metal-oxygen backbone. The magnetic studies revealed that the coexistence of ferromagnetic and antiferrimagnetic interactions resulted in a ferrimagnetic-like behavior of the homometallic chains. Below a critical temperature (T(N) = 12.5 K), bulk antiferromagnetic ordering was observed at low field due to the weak interchain antiferromagnetic interactions. A metamagnetic transition occurred at a magnetic field of ca. 5 kOe at 2 K.

[FTIR studies of L-threonic acid and its metal compounds].

Highly pure solid compounds, such as L-threonic acid, calcium L-threonate, magnesium L-threonate, manganese L-threonate, cobalt L-threonate, nickel L-theronate, and zinc L-threonate, were prepared, wherein, L-threonic acid was obtained from calcium L-threonate by strong acid type ion exchange process, calcium L-threonate or zinc L-threonate was prepared by alcohol extracting the concentrated filter liquor of the reaction of Vc, H2O2 and CaCO3 or ZnCO3, the reminder of the compounds were synthesized using alcohol extracting the concentrated solution derived from the reaction of L-threonic acid solution, prepared by double decomposition reaction of calcium L-threonate with oxalic acid, and superfluous MgO, MnCO3, Co2(OH)2CO3 and Ni2(OH)2CO3. The compositions of the compounds were determined by chemical and elemental analysis, and these compounds have the formula M(C4H7O5)2.nH2O (M = Ca, Zn, n = 0; M = Mg, Mn, Co, n = 1; M = Ni, n = 2). The purity of the compounds was 99.60% by HPLC. The IR spectra of the complexes were similar with each other but different from that of L-threonic acid. The characteristic absorption peaks of water were not observed in those of calcium L-threonate or zinc L-threonate, which showed that the molecule of water was not involved in the complexes. Further analyses indicate that M2+ in the compounds coordinated to oxygen atom of the carboxy group, while the proton of the carboxyl group was dissociated and the proton belonging to hydroxyl was not M2+ coordinated to L-threonic acid through the sp3 hybrizated fashion. It was assumed that the coordination number of M2+ was 4.