We have synthesized five new metal-organic coordination polymers incorporating the bent ligand H2hfipbb 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) with different transition metal ions and ...co-ligands via solvothermal reactions to give Zn2(hfipbb)2(py)2·DMF (1), Zn2(hfipbb)2(4,4′-bipy)(H2O) (2), Zn2(hfipbb)2(bpdab)·2DMF (3), Cd2(hfipbb)2(DMF)2·2DMF (4), and Co(hfipbb)(dpp)·MeOH (5) (py = pyridine, 4,4′-bipy = 4,4′-bipyridine, bpdab = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, dpp = 1,3-di(4-pyridyl)propane). Compound 1 displays a 2-fold 2D→2D parallel interpenetrated layer network with one-dimensional (1D) helical channels, while 3 exhibits a three-dimensional pillared helical-layer open framework of α-Po topology based upon binuclear paddlewheel units. In compounds 2 and 5, binuclear motifs with double carboxylate bridges are linked by hfipbb2− ligands into a 1D ribbon, which are further assembled into two-dimensional non-interpenetrated (4,4) layers via bipyridyl co-ligands. However, the different bridging modes of hfipbb2− ligands and the different disposition of the coordinated co-ligands around metal ions result in subtle differences in the final architecture. Thus, 2 is based on a binuclear cluster node, double-stranded hfipbb2− linkers, and single-stranded 4,4′-bipy linkers, while 5 is based on a binuclear cluster node and hfipbb2− and dpp linkers which are both double-stranded. Among these compounds, the Cd(II) complex 4 is possibly the most interesting because it represents a rare example in which metal centers are linked by carboxylate groups into infinite chains further joined together by hfipbb2− spacers to form a 2D network with tubular helical channels. All these coordination polymers exhibit low solvent-accessible volumes. Both 3 and 4 retain structural integrity and permanent microporosity upon evacuation of guest molecules, with hydrogen uptakes of 0.57 and 0.78 wt %, respectively, at 20 bar and 77 K.
Two new three‐dimensional ScIII metal–organic frameworks {Sc3O(L1)3(H2O)3⋅Cl0.5(OH)0.5(DMF)4(H2O)3}∞ (1) (H2L1=1,4‐benzene‐dicarboxylic acid) and {Sc3O(L2)2(H2O)3(OH)(H2O)5(DMF)}∞ (2) ...(H3L2=1,3,5‐tris(4‐carboxyphenyl)benzene) have been synthesised and characterised. The structures of both 1 and 2 incorporate the trinuclear trigonal planar Sc3(O)(O2CR)6 building block featuring three ScIII centres joined by a central μ3‐O2− donor. Each ScIII centre is further bound by four oxygen donors from four different bridging carboxylate anions, and a molecule of water located trans to the μ3‐O2− donor completes the six coordination at the metal centre. Frameworks 1 and 2 show high thermal stability with retention of crystallinity up to 350 °C. The desolvated materials 1 a and 2 a, in which the solvent has been removed from the pores but with water or hydroxide remaining coordinated to ScIII, show BET surface areas based upon N2 uptake of 634 and 1233 m2 g−1, respectively, and pore volumes calculated from the maximum N2 adsorption of 0.25 cm3 g−1 and 0.62 cm3 g−1, respectively. At 20 bar and 78 K, the H2 isotherms for desolvated 1 a and 2 a confirm 2.48 and 1.99 wt % total H2 uptake, respectively. The isosteric heats of adsorption were estimated to be 5.25 and 2.59 kJ mol−1 at zero surface coverage for 1 a and 2 a, respectively. Treatment of 2 with acetone followed by thermal desolvation in vacuo generated free metal coordination sites in a new material 2 b. Framework 2 b shows an enhanced BET surface area of 1511 m2 g−1 and a pore volume of 0.76 cm3 g−1, with improved H2 uptake capacity and a higher heat of H2 adsorption. At 20 bar, H2 capacity increases from 1.99 wt % in 2 a to 2.64 wt % for 2 b, and the H2 adsorption enthalpy rises markedly from 2.59 to 6.90 kJ mol−1.
It's ScIIIandalous: {Sc3O(L1)3(H2O)3⋅Cl0.5OH0.5(DMF)4(H2O)3}∞ (1) (H2L1=1,4‐benzenedicarboxylic acid) and {Sc3O(L2)2(H2O)3OH(H2O)5(DMF)}∞ (2) (H3L2=1,3,5‐tris(4‐carboxyphenyl)benzene) incorporate the trinuclear trigonal planar Sc3(O)(O2CR)6 building block. After appropriate thermal treatment on the acetone‐exchanged sample 2, the generation of free metal coordination sites has been achieved to give an increase in the BET surface area in 2 b.
Treatment of Cu(dipic)(OH2)3 dipic2 = pyridine-2,6-dicarboxylate (dipicolinate) 1 with diverse bipyridyl bridging ligands of varying length pyrazine (pyz), 4,4′-bipyridine (bipy), ...trans-4,4′-azobis(pyridine) (azpy), 1,2-bis(pyridin-4-yl)ethene (bpe), 3,6-bis(pyridin-4-yl)-1,2,4,5-tetrazene (pytz) and 1,4-bis{2-(pyridin-4-yl)ethenyl}benzene (bpeb) under a variety of conditions yielded Cu2(dipic)2(bipy)·4H2O, 2, Cu2(dipic)2(bpe)·2H2O, 3, {Cu(dipic)(OH2)}(μ-pyz)0.5·H2O, 4, {Cu(dipic)(OH2)}(μ-pyz)0.5, 5, {Cu(dipic)(OH2)}(μ-bipy)0.5{Cu(dipic)(OH2)0.75(OHMe)0.25}(μ-bipy){Cu(dipic)(OH2)}·2.25H2O·0.5CH3OH, 6, {{Cu(dipic)}2(μ-bipy)·2H2O·CH2Cl2}∞, 7, {Cu(dipic)(OH2)}(μ-bpe){Cu(dipic)}·3H2O, 8, {{Cu(dipic)}(μ-azpy)0.5·CH2Cl2}∞, 9, {{Cu(dipic)}(μ-azpy)0.5·CH3OH}∞, 10, {Cu(dipic)(OH2)}2(μ-pytz)·2H2O, 11, Cu2(dipic)2(bpeb)·4H2O, 12 and {Cu(dipic)(OHMe)}2(μ-bpeb), 13. Complexes 4−11 and 13 were characterized by single crystal X-ray diffraction which confirmed the presence of binuclear building blocks in which two square-pyramidal Cu(II) centers are linked by bipyridyl bridges. The differences in the structures lie in the choice of ligand located at the apical site of the Cu(II) center, the basal sites being occupied by one N- and two O-donors of the mer-bound dipicolinate ligand and an N-donor from the bridging heterocyclic ligand. In the presence of excess coordinating solvent such as H2O or MeOH, recrystallization affords products with the apical sites occupied by solvent molecules to give extensive hydrogen-bonding networks within 3-D matrices in 4−6, 8, 11, 13. With reduced levels of coordinating solvent in the crystallizing medium, the apical sites are occupied by carboxylate oxygens of adjacent Cu(dipic) moieties giving 2-D coordination polymers of 63 topology as in 7, 9, 10.
Non‐CsCl topologies for eight‐connected solid‐state materials have been observed for the first time in three networks based on lanthanide cations and 4,4′‐bipyridine‐N,N′‐dioxide ligands. The ...structure of the {Yb(L)4(CF3SO3)3}∞ network is depicted.
A helical staircase structure is observed for the layers made from chains of alternating AgI centers and pytz ligands in Ag(pytz)(NO3)∞ (pytz = 3,6‐di‐(4‐pyridyl)‐1,2,4,5‐tetrazine). Decisive for the ...formation of this array—a view of the structure along the helical axis is shown on the right—is the anionic ligand NO −3, as shown by the comparison with the analogous PF −6 and BF −4 compounds. These two show parallel chains of alternating AgI ions and pytz ligands held in pairs through weak AgAg contacts and π–π interactions between adjacent pytz ligands.
Reaction of Co(NO(3))(2)·6H(2)O with H(2)L H(2)L = pyridine-4-(phenyl-3',5'-dicarboxylic acid) under different reaction conditions gives three closely-related metal-organic framework polymers, ...{Co(2)(L)(2)(DMF)·n(solv)}(∞) (1), {Co(L)·2DMF}(∞) (2) and {Co(3)(L)(3)(DMF)(0.5)(H(2)O)(1.5)·n(solv)}(∞) (3). Variation in reaction conditions thus has a decisive impact on the materials isolated, producing frameworks based upon either binuclear (1, 2) or trinuclear (3) cobalt cluster nodes. Analysis of their crystal structures shows that all three contain considerable solvent-accessible volumes, an indication of porosity that is confirmed for desolvated 1 and 3, which can store up to 2.75 and 2.33 wt% of H(2) at 78 K and 20 bar, respectively.
The reaction of cadmium(II) and zinc(II) salts with 3,6-bis(pyridin-3-yl)-1,2,4,5-tetrazine (3,3‘-pytz) affords coordination polymers, the structures of which are controlled by the choice of ...alcoholic solvent. Reaction of Cd(NO3)2·4H2O and 3,3‘-pytz in MeOH/CH2Cl2 yields the 1:1 ligand/metal complex {Cd(μ-3,3‘-pytz)(NO3)2(MeOH)2}∞, 1 triclinic space group P1̄; a = 9.011(2) Å, b = 9.338(4) Å, c = 11.941(2) Å, α = 74.51(3)°, β = 86.94(4)°, γ = 86.50(5)°; Z = 2. Replacement of MeOH with EtOH or iPrOH in the above reaction affords respectively the 3:2 ligand/metal complexes {Cd2(μ-3,3‘-pytz)3(NO3)4(EtOH)}∞, 2 triclinic, space group P1̄; a = 9.060(4) Å, b = 9.848(3) Å, c = 13.208(4) Å, α = 86.76(3)°, β = 79.04(3)°, γ = 88.14(2)°; Z = 2 and {Cd2(μ-3,3‘-pytz)3(NO3)4(CH2Cl2)}∞, 3 triclinic space group P1̄; a = 8.981(16) Å, b = 9.93(2) Å, c = 13.19(2) Å, α = 94.18(15)°, β = 102.35(13)°, γ = 88.12(15)°; Z = 2. Complex 1 exhibits a zigzag chain polymer motif, whereas complexes 2 and 3 show noninterpenetrated ladder structures. Reaction of Zn(NO3)2·6H2O and 3,3‘-pytz in MeOH or EtOH/CH2Cl2 solution affords a 3:2 ligand/metal complex {Zn2(3,3‘-pytz)2(NO3)4(ROH)2(μ-3,3‘-pytz)}∞, 4 R = Me; triclinic, space group P1̄; a = 7.5346(12) Å, b = 10.7279(13) Å, c = 15.219(2) Å, α = 85.364(11)°, β = 80.627(12)°, γ = 69.343(12)°; Z = 2 and 5 R = Et; triclinic, space group P1̄; a = 7.590(3) Å, b = 10.561(2) Å, c = 15.951(5) Å, α = 87.56(2)°, β = 83.49(4)°, γ = 71.12(2)°; Z = 2. The reaction in iPrOH/CH2Cl2 results in a 3:2 ligand/metal complex {Zn2(μ-3,3‘-pytz)3(NO3)4(CH2Cl2)2}∞, 6 triclinic, space group P1̄; a = 9.1110(18) Å, b = 12.474(3) Å, c = 13.171(3) Å, α = 117.79(3)°, β = 102.39(3)°, γ = 101.13(3)°; Z = 2. The isostructural complexes 4 and 5 both exhibit a unique hydrogen-bonding motif in coordination polymer chemistry which gives rise to an alternating single- and double-bridged species, whereas 6 exists as a noninterpenetrated ladder complex.
The coordination polymer {Cd2(4,4‘-pytz)3(μ-NO3)(NO3)3(MeOH)}∞, 1, displays a unique polyknotted structure in which each Cd(II) center is coordinated by three pyridyl N-donors arranged in an ...approximate T-shaped geometry to form a ladder motif. Within this structure, each ladder is interpenetrated perpendicularly by two other ladders. Significantly, each of the Cd(II) centers at the intersections of one ladder is bridged by a coordinated NO3 - anion to a Cd(II) center located at the corner of a square section of one of the perpendicularly interpenetrated ladders. Thus, all the ladders are linked together to give a three-dimensional polymer where the overall architecture is constructed of one molecule in a fused “polyknot”.
