Porous coordination polymers are materials formed from metal ions that are bridged together by organic linkers and that can combine two seemingly contradictory properties-crystallinity and ...flexibility. Porous coordination polymers can therefore create highly regular yet dynamic nanoporous domains that are particularly promising for sorption applications. Here, we describe the effective selective sorption of dioxygen and nitric oxide by a structurally and electronically dynamic porous coordination polymer built from zinc centres and tetracyanoquinodimethane (TCNQ) as a linker. In contrast to a variety of other gas molecules (C(2)H(2), Ar, CO(2), N(2) and CO), O(2) and NO are accommodated in its pores. This unprecedented preference arises from the concerted effect of the charge-transfer interaction between TCNQ and these guests, and the switchable gate opening and closing of the pores of the framework. This system provides further insight into the efficient recognition of small gas molecules.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The ins and outs of spin: Using the microporous coordination polymer {Fe(pz)Pt(CN)₄} (1, pz=pyrazine), incorporating spin-crossover subunits, two-directional magnetic chemo-switching is achieved at ...room temperature. In situ magnetic measurements following guest vapor injection show that most guest molecules transform 1 from the low-spin (LS) state to the high-spin (HS) state, whereas CS₂ uniquely causes the reverse HS-to-LS transition.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Precise control of spin transition temperature (T c) is one of the most important challenges in molecular magnetism. A Hofmann-type porous coordination polymer {Fe(pz)PtII(CN)4} (1; pz = pyrazine) ...exhibited cooperative spin transition near room temperature (T c up = 304 K and T c down = 284 K) and its iodine adduct {Fe(pz)PtII/IV(CN)4(I)} (1-I), prepared by oxidative addition of iodine to the open metal sites of PtII, raised the T c by 100 K. DSC and microscopic Raman spectra of a solid mixture of 1-I and 1 revealed that iodine migrated from 1-I to 1 through the grain boundary after heating above 398 K. We have succeeded in precisely controlling the iodine content of {Fe(pz)Pt(CN)4(I) n } (1-I n ; n = 0.0–1.0), which resulted in consecutive modulation of T c in the range 300–400 K while maintaining the hysteresis width. Furthermore, it was demonstrated that iodine migration in the solid mixture was triggered by the spin transition of 1-I. The magnetically bistable porous framework decorating guest interactive open-metal-site in the pore surface makes it possible to modulate T c ad arbitrium through unique postsynthetic method using iodine migration.
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The oxalate-bridged bimetallic complexes {NH(prol)3}MIICrIII(ox)3 (MII = MnII, FeII, CoII) with hydrophilic tri(3-hydroxypropyl)ammonium (NH(prol)3 +) were prepared by a new synthetic procedure, and ...the effects of the NH(prol)3 + ion upon the structure, magnetism, and electrical conduction were studied. An X-ray crystallographic study of the MnCr dihydrate, {NH(prol)3}MnCr(ox)3·2H2O, was performed. Crystal data: hexagonal, P63, a = b = 9.3808(14) Å, c = 15.8006(14) Å, Z = 2. The structure comprises oxalate-bridged bimetallic layers interleaved by NH(prol)3 + ions. The ions assume a tripodal configuration and are hydrogen bonded to the bimetallic layers together with water molecules, giving rise to a short interlayer separation (7.90 Å) and unsymmetrical faces to the bimetallic layer. Cryomagnetic studies demonstrate ferromagnetic ordering with transition temperature of 5.5 K for the MnCr complex, 9.0 K for the FeCr complex, and 10.0 K for the CoCr complex. The interlayer magnetic interaction is negligibly weak in all of the complexes despite the short interlayer separation. A slow magnetization is observed in all the complexes. This is explained by spin canting associated with the unsymmetrical feature of the bimetallic layer. The complexes show proton conduction of 1.2 × 10−10 to 4.4 × 10−10 S cm−1 under 40% relative humidity (RH) and ∼1 × 10−4 S cm−1 under 75% RH. On the basis of water adsorption/desorption profiles, the conduction under 40% RH is mediated through the hydrogen-bonded network formed by the bimetallic layer, NH(prol)3 + ions, and water molecules (two per MCr). Under 75% RH, additional water molecules (three per MCr) are concerned with the high proton conduction. This is the first example of a metal complex system exhibiting coexistent ferromagnetism and proton conduction.
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A dinuclear Cu(II) complex, Cu2(OAc)2(tpxn)(H2O)2(PF6)2 tpxn = N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,4-xylenediamine, was synthesized and characterized by single-crystal X-ray analysis. The compound ...crystallizes in the monoclinic space group P21/c with a = 9.310(4), b = 10.880(4), c = 20.628(8)Å, β = 91.581(6)°, V = 2088.6(14)Å3, Dcalcd = 1.704 g/cm3, and Z = 4. The R1 I > 2σ(I) and wR2 (all data) values are 0.0343 and 0.0923, respectively, for all 4731 independent reflections. The complex contains two square-pyramidal Cu(II) ions bound to both terminal tridentate sites of tpxn.
A mononuclear cobalt(III) complex with 2-(2-hydroxymethylphenyl)iminomethylphenol (H2L1-H) and dimethylaminopyridine (dmpa), Co(L1-H)(HL1-H)dmpa·CH3CN, was synthesized and characterized by ...single-crystal X-ray analysis. The compound crystallizes in the monoclinic space group P21/n (#14) with cell parameters a = 10.551(2)Å, b = 12.499(3)Å, c = 24.242(6)Å, β = 92.004(4)°, V = 3194.8(12)Å3, Dcalcd = 1.400 g/cm3, Z = 4. The R1 I > 2σ(I) and wR2 (all data) values are 0.0483 and 0.1226, respectively, for all 7112 independent reflections. The coordination forms of the two H2L1-H ligands are dianionic tridentate and monoanionic bidentate, respectively.
A quasielastic neutron scattering and solid-state 2H NMR spectroscopy study of the polymeric spin-crossover compound {Fe(pyrazine)Pt(CN)4} shows that the switching of the rotation of a molecular ...fragmentthe pyrazine ligandoccurs in association with the change of spin state. The rotation switching was examined on a wide time scale (10–13–10–3 s) by both techniques, which clearly demonstrated the combination between molecular rotation and spin-crossover transition under external stimuli (temperature and chemical). The pyrazine rings are seen to perform a 4-fold jump motion about the coordinating nitrogen axis in the high-spin state. In the low-spin state, however, the motion is suppressed, while when the system incorporates benzene guest molecules, the movements of the system are even more restricted.
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The title compound, Ni(HL1–NO2)2·CH3CN, H2L1–NO2 = 2-2-(hydroxymethylphenyl)iminomethyl-4-nitrophenol, was synthesized and characterized by single-crystal X-ray analysis. The compound crystallizes in ...the triclinic space group P1 with cell parameters a = 10.556(2)Å, b = 11.779(3)Å, c = 12.247(3)Å, α = 86.412(10)°, β = 71.135(8)°, γ = 73.009(8)°, V = 1377.2(5)Å3, Dcalcd = 1.549 g/cm3, Z = 2. The R1 I > 2σ(I) and wR2 (all data) values are 0.0362 and 0.1024, respectively, for all 5989 independent reflections. The tridentate ligands coordinate to the nickel atom as a mer-manner.
The synthesis, structure, and magnetic properties of three clathrate derivatives of the spin‐crossover porous coordination polymer {Fe(pyrazine)Pt(CN)4} (1) with five‐membered aromatic molecules ...furan, pyrrole, and thiophene is reported. The three derivatives have a cooperative spin‐crossover transition with hysteresis loops 14–29 K wide and average critical temperatures Tc=201 K (1⋅fur), 167 K (1⋅pyr), and 114.6 K (1⋅thio) well below that of the parent compound 1 (Tc=295 K), confirming stabilization of the HS state. The transition is complete and takes place in two steps for 1⋅fur, while 1⋅pyr and 1⋅thio show 50 % spin transition. For 1⋅fur the transformation between the HS and IS (middle of the plateau) phases occurs concomitantly with a crystallographic phase transition between the tetragonal space groups P4/mmm and I4/mmm, respectively. The latter space group is retained in the subsequent transformation involving the IS and the LS phases. 1⋅pyr and 1⋅thio display the tetragonal P4/mmm and orthorhombic Fmmm space groups, respectively, in both HS and IM phases. Periodic calculations using density functional methods for 1⋅fur, 1⋅pyr, 1⋅thio, and previously reported derivatives 1⋅CS2, 1⋅I, 1⋅bz(benzene), and 1⋅pz(pyrazine) have been carried out to investigate the electronic structure and nature of the host–guest interactions as well as their relationship with the changes in the LS–HS transition temperatures of 1⋅Guest. Geometry‐optimized lattice parameters and bond distances in the empty host 1 and 1⋅Guest clathrates are in general agreement with the X‐ray diffraction data. The concordance between the theoretical results and the experimental data also comprises the guest molecule orientation inside the host and intermolecular distances. Furthermore, a general correlation between experimental Tc and calculated LS–HS electronic energy gap was observed. Finally, specific host–guest interactions were studied through interaction energy calculations and crystal orbital displacement (COD) curve analysis.
The synthesis, structure, and magnetic properties of three new clathrate compounds of the spin‐crossover porous coordination polymer {Fe(pyrazine)Pt(CN)4} are presented (see example). A DFT analysis of the host–guest interactions and rationalization of the experimental critical temperatures observed for this family of compounds were carried out.
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