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A two-dimensional (2D) square-grid type porous coordination polymer [Fe(bdpt)2] • guest (1 • g, Hbdpt - 3-(5-bromc>2-pyridyl)-5-(4-pyridyl)-l,2,4-triazole) with isolated small cavities was designed and constructed as a spin-crossover (SCO) material based on octahedral FeIIN6 units and an all-nitrogen ligand. Three guest-inclusion forms were successfully prepared for 1 • g (1 • EtOH for g = ethanol, 1 • MeOH for g = methanol, 1 for g = Null), in which the guest molecules interact with the framework as hydrogen-bonding donors. Magnetic susceptibility measurements showed that 1-g exhibited two-step SCO behavior with different transition temperatures (1-EtOH < 1 • MeOH < l) and hysteresis widths (1 • EtOH > 1 • MeOH > 1 0). Such guest modulation of two-step spin crossover temperature and hysteresis without changing two-step state in a porous coordination framework is unprecedented. X-ray single-crystal structural analyses revealed that all two-step SCO processes were accompanied with interesting symmetry-breaking phase transitions from space group of P21/n for all high-spin Fe(II), to P1 for ordered half high-spin and half low-spin Fe(II), and back to P21/n for all low-spin Fe(II) again by lowering temperature. The different SCO behaviors of 1 • g were elucidated by the steric mechanism and guest--host hydrogen-bonding interactions. The SCO behavior of 1-g can be also controlled by external physical pressure. [ABSTRACT FROM AUTHOR]

A microporous coordination polymer, namely, [Co3(ina)4(OH)(C2H5OH)3](NO3)·C2H5OH·(H2O)3 (1, or MCF-38, ina = isonicotinate), with 8-connected {Co3(OH)} clusters as the structural secondary building units, has been solvothermally synthesized. The hydroxo-centered Co(II) cluster involves multiple active metal sites. The interesting apical ligand substitutions have been directly observed, and the corresponding products of [Co3(ina)4(OH)(G)x(H2O)n](NO3)·G·(H2O)m (1 PrOH, G = PrOH, x = 2, n = 1, m = 3; 1 BuOH, G = BuOH, x = 2, n = 1, m = 1, and 1 MeOH, G = MeOH, x = 3, n = 0, m = 7) have also been obtained by solvothermal syntheses or crystal-to-crystal transformations. High-pressure H2 adsorption measurement at 77 K reveals that activated 1 can absorb 2.2 wt % H2 at 5 bar. The relative H2 absorption at low pressure (86% of the storage capacity at 1 bar) is higher than the corresponding values reported for some typical porous coordination polymers. The magnetic studies of 1 show a dominant antiferromagnetic coupling between Co(II) ions of intra- and inter-cluster. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of equimolar zinc acetate, lithium acetate, and 1,3,5-benzenelricarboxylic acid (H3btc) in different mixed solvents yielded isostnictural three-dimensional frameworks [UZn(btc)()) - IG leG and IG denote coordinated and lattice guests, respectively; cG=(nmp)0.5(H2O)0.5, IG=(EtOH)0.5 (1a); cG=H2O, IG= EtOH (1b); nmp=N-methyl-2-pyrrolidone] with one-dimensional channels occupied by guest molecules and solvent-coordinated, extrusive Li+ ions. Thermogravimetry analyses and powder X-ray diffraction measurements revealed that both la and lb can lose all lattice and coordinated guests to torn', a desolvaled phase [LiZn(btc)] (MCF-27, 1) and almost retains the original framework structure. Gas adsorption measurements on 1 confirmed its permanent porosity but suggested a structural transformation horn 1a/1b 101.11 is noteworthy that only la can undergo a single-ctystal 10 single-crystal (SCSC) transformation into 1 upon desolvation. The crystal structure of 1 revealed that Ihe Li+ ions were retracted into the channel walls via complementary coordination to the carboxylate oxygen atoms in the framework rather than being exposed on the pore surface. Single-crystal X-ray diffraction analyses were also performed for N2- and CO2-loaded samples of 1, revealing that the framework remained unchanged when the gases were adsorbed. Although the gas molecules could not be modeled, the residue electrons inside the channels demonstrated that the retracted Li+ ions still behave as the primary interacting site for CO2 molecules. Nevertheless, solvent molecules such as H2O can readily compete with the framework oxygen atom to retrieve the extrusive Li+ ions, accompanying the reverse structural transformation, i.e., from 1 to 1a/1b. [ABSTRACT FROM AUTHOR]

Two pairs of supramolecular isomers based on ternary zinc(Il)/triazolate/X (triazolate = 3,5-dimethyl-1 ,2,4-triazolate (Hdmtz), X = HCOO-, F-) metal azolate frameworks, namely, [Zn(dmtz)(HCOO)] ∙ H2O (MAF-X3, la), [Zn(d-mtz)(HCOO)] ∙ (1/6Me2NH)(1/4H2O) (MAF-X4, 1b), [Zn(dmtz)F] (MAF-X5, 2a), and [Zn(dmtz)F] (MAF-X6, 2b), have been synthesized via variations of the reaction conditions. The 3-connected Zn(dmtz) networks in 1a, 1b, 2a, and 2b can be described as rarely observed 4.82, 4.122, (8,3)-b, and 82.10-a, respectively. Besides the μ3-dmtz, tetrahedral and trigonal-bipyramidal/square-pyramidal coordination of the Zn ions are accomplished by monodentate formate and μ-F, respectively. While 1a and 2b are nonporous structures, 1b and 2a exhibits 1D nanotubular hydrophilic (d 3.2 Å) and hydrophobic (d 3.6 Å) channels, respectively. Thermogravimetric analysis shows that the stabilities of 2a and 2b are much better than those of la and 1b, which may be ascribed to different coordination numbers of zinc atoms. Moreover, 1b and 2a with different pore properties show selective sorption behavior. [ABSTRACT FROM AUTHOR]

A 3D microporous cadmium(ll) metal-organic framework based on 1 H-tetrazole exhibits strong hydrogen binding with an initial enthalpy of adsorption of 13.3 kJ/mol, due to the smaller pore sizes and the high hydrogen binding affinity of the tetrazolyl-ringdecorated inner surface of the pores. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of cobalt acetate, alkali metal hydroxide, and isophtalic (H2ipa) in H2O/alcohol produce five new three-dimensional (3D) heterometallic carboxylate frameworks, namely, [Na2Co(ipa)2(MeOH)2]n (1), [Na2Co(ipa)2. (EtOH)2]n (2), [Na2Co(ipa)2(H2O)(EtOH)]n (3), [Li2Co(ipa)2(EtOH)]n (4), and ([Li2Co(ipa)2(H2O)]]∙H2O)n (5). Compounds 1—5 are all based on anionic [Co(ipa)2]n square grids, which are linked by alkali metal ions in various manners to generate closely related but quite different 3D architectures. In addition to the carboxylate oxygen donors of the anionic [Co(ipa)2]n square grids, the alkali metal ions are also coordinated by the MeOH, EtOH, or H2O ligands. The prototypical compound 1 shows interresting solid-state structural transformations and sorption properties. The coordinated MeOH molecules in 1 can be easily substituted by moist H2O, accompanying a structural transformation from the chiral phase 1 tocentrosymmetric phase 3. Further, thermal liberation of all MeOH ligands causes significant change and gives rise to a non-porous framework [CoNa2(ipa)2] (1'), which adsorbs MeOH, EtOH< and MeCN but not acetone based on the sizes of solvent molecules. Moreover, 1' can also selectively absorb CO2 over N2, H2 and C2H2, demonstrating the importance of oxophilic Na(I) ion in controlling the gate-opening behavior. [ABSTRACT FROM AUTHOR]

The facile and effective one-pot solvothermal syntheses of 3,5-disubstituted 1,2,4-triazole and its derivatives (substituted group = alkyl, aryl, and pyridyl) through cyclocondensations of organonitriles and hydrazine hydrate in the absence/presence of metal salts have been established. By control of the solvothermal conditions and/or the addition of counteranions, different intermediates and final products were derived from various organonitriles, in which an intermediate N,N′-bis(picolinamide)azine (H4bpa) has been successfully trapped in its neutral manganese(II) complexes. A systematical study shows that, after the initial formation of 2-pyridylamidrazone from 2-cyanopyridine and hydrazine, two reaction paths are involved in the formation of 1,2,4-triazoles: via the formation of 3,6-bis(2-pyridyl)-l,2-dihydro-l,2,4,5-tetrazine and H4bpa as intermediates. The tetrazine and H4bpa paths are preferred in the absence and presence of metal ions, respectively. In the presence of metal ions, metal ion binding can stabilize the tautomers, enhance the nucleophilic reactivity of the imino C atom, and inhibit the tautomerization of H4bpa, hence leading to the formation of 1,2,4-triazolates or H4bpa in complexed forms. The in situ cyclocondensation reactions of 2-pyridylamidrazone and carboxylate into asymmetric 3,5-disubstituted 1,2,4-triazolates under solvothermal conditions have also been observed for the first time. Crystal structures of the crystalline metal complexes have been obtained, including dinuclear [Mn2(bpt)2Cl2(H2O)2] (1) and [Mn2(bpt)2(SCN)2(H2O)2] (3; Hbpt = 3,5-bis(2-pyridyl)-4H-1,2,4-triazole), tetranuclear [Mn4(H3bpa)2(mpt)4(N3)2]·2H2O (5; Hmpt = 3-methyl-5-(2-pyridyl)-1H-1,2,4-triazole), [Mn4(H3bpa)2(pt)4(N3)2]·2C2H5OH (6; Hpt = 5-(2-pyridyl)-1H-1,2,4-triazole), and [Mn4(H3bpa)4(SCN)4]. 2C2H5OH (7), as well as helical [Cu(bpt)] (2). Among them, 7 is the first example of a neutral tetranuclear [2 × 2] grid manganese(II) complex. Both 5 and 7 exhibit antiferromagnetic interactions. [ABSTRACT FROM AUTHOR]