Ligand Excess "Inverse-Defected" Zr6 Tetrahedral Tetracarboxylate Framework and Its Thermal Transformation.

A new porous coordination polymer (PCP/MOF), ZRTE-10, based on a tetrahedral 1,3,5,7-tetra(carboxyphenyl)benzene ligand (H4L4) was synthesized using formic or acetic acids as modulators. The low symmetry (C2/c) framework, [Zr6(µ3-O)4(µ3-OH)4(L4)(HL4)2(OH)2(H2O)2], is built upon a rare 10-connected Zr6 cluster. Two-thirds of the ligands bear one nondeprotonated carboxy group, and the framework has a complex trinodal 3,4,10-c, {414.624.87}{43}2{45.6}, underlying net. Supercritical CO2 drying and mild degassing at 120 °C yielded a porous material with SBET = 1190 m2 g-1. When heated up to ∼200 °C, ZRTE-10 converts to another crystalline framework, ZRTE-11. The latter was identified to be identical to the expected fluorite (flu) observed previously for other tetrahedral ligands. The high symmetry (I4/m) framework is built upon 8-connected Zr6 clusters and has a formula of [Zr6(µ3-O)4(µ3-OH)4(OH)4(L4)2]. The complicated trinodal network of ZRTE-10 and the simple flu net in ZRTE-11 are topologically interrelated via the operation of the merging of two neighbor three-connected nodes to one four-connected one. The thermally induced conversion of ZRTE-10 proceeds with expulsion of one ligand per Zr6 node in the pores of the framework, resulting in a relatively low SBET = 585 m2 g-1 for the activated H4L4@ZRTE-11. A mixed ligand approach for ZRTE-10,11 was attempted using 1,3,5-tetra(carboxyphenyl)benzene (H3L3), which is a truncated analog of H4L4 with one missing branch. The monocrystalline sample of ZRTE-10 obtained in small yields demonstrated only minor inclusion of H3L3. However, the high-yielding (∼80%) procedure with HCl as a modulator allows near proportional incorporation of the ligands. The formed materials are semiamorphous with powder XRDs intermediary between pure ZRTE-10 and -11. Thermal treatment of the semiamorphous materials increases their crystallinity and allows SBET = 400-550 m2 g-1 surface areas to be reached for pure H4L4 and H3L3 or their mixture alike. The approach proposes a viewpoint on the H3L3 trifunctional ligand as a model of a ligand platform, suitable for bearing a large functionality on the fourth "truncated" branch. The significance of ZRTE-10 as a material for postsynthetic introduction of metal-based cluster functionality and as a model of functionality encapsulation, an alternative to the ship-in-the-bottle method, is discussed.

Benzoic acid as a selector-modulator in the synthesis of MIL-88B(Cr) and nano-MIL-101(Cr).

The concentration of benzoic acid was found to exercise efficient control over the formation of either MIL-101(Cr) or MIL-88B(Cr) under otherwise similar hydrothermal synthetic conditions. Nanocrystals of MIL-101(Cr) with ∼100 nm average size and excellent SBET = 3467 m2 g-1 are obtained at lower concentrations of benzoic acid, while at higher concentrations the microparticulated MIL-88B(Cr) product is formed. Hereby a new efficient synthetic method towards the elusive MIL-88B(Cr), yet reported only once without synthetic details, is proposed. The obtained MIL-88B(Cr) has an interesting and potentially valuable property of retaining its high-volume form (Vcell ∼ 2000 Å3) after thermal activation. The degassing of MIL-88B(Cr) in a vacuum at 250 °C yields a porous material with a SBET area of 1136 m2 g-1, which is around the theoretical maximum. The transition to the denser 'closed' form (Vcell ∼ 1500 Å3) occurs only at 350 °C, when all of the benzoate/benzoic acid, hindering the process, is removed.

High-yield, fluoride-free and large-scale synthesis of MIL-101(Cr).

MIL-101(Cr), one of the most important prototypical MOFs, is well investigated and widely used in many scientific fields. With regard to MOF synthesis in general, the addition of a modifier is commonly used to improve the properties of the products. The effect of inorganic (mineral) and organic acid modifiers was thoroughly investigated in the synthesis of MIL-101(Cr) and HNO3 could increase the yield to over 80% of a product with average SBET > 3200 m(2) g(-1) in repeated experiments (from an average of 50% in most published syntheses) in small-scale laboratory synthesis. The large-scale synthesis could use the finding of HNO3 addition and produce MIL-101(Cr) in >100 g quantities with yields near 70% and BET-surface areas near 4000 m(2) g(-1). The addition of acetic acid (CH3COOH) together with seeding could decrease the reaction temperature, the lowest being 160 °C (from typically 220 °C in published procedures), with still relatively good yield and BET surface area of the product. The use of other strong inorganic or weak carboxylic acids as modulators typically caused a decrease in yield and porosity.

1,3,5,7-Tetrakis(tetrazol-5-yl)-adamantane: the smallest tetrahedral tetrazole-functionalized ligand and its complexes formed by reaction with anhydrous M(II)Cl2 (M = Mn, Cu, Zn, Cd).

1,3,5,7-Tetrakis(tetrazol-5-yl)-adamantane (H4L) was probed as a building block for the synthesis of tetrazolato/halido coordination polymers with open-network structures. MCl2 (M = Cu, Cd, Zn, Mn) was reacted with H4L in DMF at 70 °C to yield [Cu4Cl4L(DMF)5]·DMF, ; [Cd4Cl4L(DMF)7]·DMF, ; [Zn3Cl2L(DMF)4]·2DMF, and [Mn2L(DMF)2(MeOH)4]·DMF·2MeOH·2H2O, . and (Fddd) are nearly isostructural and have zeolitic structures with a {4(3)·6(2)·8}, gis or gismondine underlying net, where the role of the tetrahedral nodes is served by the coordination bonded clusters and the adamantane moiety. (P21/n) has a porous structure composed of coordination bonded layers with a (4·8(2)) fes topology joined via trans-{Zn(tetrazolate)2(DMF)4} pillars with an overall topology of {4·6(2)}{4·6(6)·8(3)}, fsc-3,5-Cmce-2. (Pca21) is composed of stacked {Mn2L} hexagonal networks. In and the ligand fulfills a symmetric role of a tetrahedral building block, while in and it fulfills rather a role of an effective trigonal unit. Methanol-exchanged and activated displayed an unusual type IV isotherm with H2 type hysteresis for N2 sorption with an expected uptake at high P/P0, but with a smaller SBET = 505.5 m(2) g(-1) compared to the calculated 1789 m(2) g(-1), which is a possible result of the framework's flexibility. For H2 sorption 0.79 wt% (1 bar, 77 K) and 0.06 wt% (1 bar, RT) uptake and Qst = -7.2 kJ mol(-1) heat of adsorption (77 K) were recorded. Weak antiferromagnetic interactions were found in and with J1 = -9.60(1), J2 = -17.2(2), J3 = -2.28(10) cm(-1) and J = -0.76 cm(-1) respectively. The formation of zeolitic structures in and , the concept of structural 'imprinting' of rigid building blocks, and design opportunities suggested as a potential hexafunctionalized biadamantane building block.

1,2,4-Triazole functionalized adamantanes: a new library of polydentate tectons for designing structures of coordination polymers.

A series of functionalized adamantanes: 1,3-bis(1,2,4-triazol-4-yl)(tr(2)ad); 1,3,5-tris(1,2,4-triazol-4-yl)-(tr(3)ad); 1,3,5,7-tetrakis(1,2,4-triazol-4-yl)adamantanes (tr(4)ad) and 3,5,7-tris(1,2,4-triazol-4-yl)-1-azaadamantane (tr(3)ada) were developed as a new family of geometrically rigid polydentate tectons for supramolecular synthesis of framework solids. The coordination compounds were prepared under hydrothermal conditions; their structures reveal a special potential of the triazolyl adamantanes for the generation of highly-connected and open frameworks as well as structures based upon polynuclear metal clusters assembled with short-distance N(1),N(2)-triazole bridges. Complexes [Cd{L}(2)]A·nH(2)O [L = tr(3)ad, A = 2NO(3)(-) (4), CdCl(4)(2-) (5); L = tr(3)ada, A = CdI(4)(2-) (7)] are isomorphous and adopt a layered 3,6-connected structure of CdI(2) type. [{Cu(3)(OH)}(2)(SO(4))(5)(H(2)O)(2){tr(3)ad}(3)]·26H(2)O (6) is a layered polymer based upon Cu(3)(µ(3)-OH) nodes and trigonal tr(3)ad links. In [Cu(3)(OH)(2){tr(3)ada}(2)(H(2)O)(4)](ClO(4))(4) (8), [Cu(2){tr(3)ada}(2)(H(2)O)(3)](SO(4))(2)·7H(2)O (9) and [Cd(2){tr(3)ada}(3)]Cl(4)·28H(2)O (10) (UCl(3)-type net) the organic tripodal ligands bridge polynuclear metal clusters. Complexes [Ag{tr(4)ad}]NO(3)·3.5H(2)O (11) and [Cu{tr(4)ad}(H(2)O)](ClO(4))(2)·3H(2)O (12) have 3D SrAl(2)-type frameworks with the metal ions and adamantane tectons as topologically equivalent tetrahedral nodes, while in [Cd(3)Cl(6){tr(4)ad}(2)]·9H(2)O (13) the ligands bridge trinuclear six-connected Cd(3)Cl(6)(µ-tr)(4)(tr)(2) clusters. In the compounds [Cd(2){tr(2)ad}(4)(H(2)O)(4)](CdBr(4))(2)·2H(2)O (2) and [Cd{tr(2)ad}(4){CdI(3)}(2)]·4H(2)O (3) the bitopic ligands provide simple links between the metal ions, while in [Ag(2){tr(2)ad}(2)](NO(3))(2)·2H(2)O (1) the ligand is tetradentate and generates a 3D framework.

Novel coordination frameworks incorporating the 4,4'-bipyrazolyl ditopic ligand.

The reaction of the rigid spacer 4,4'-bipyrazole (H(2)BPZ) with late transition metals, either following conventional routes or under solvothermal conditions, afforded the coordination polymers [M(BPZ)]·Solv (M = Zn, 1; Co, 2; Cd, 3; Hg, 4; Cu, 5; Ni, 6; Pd, 7; Solv = DMF, 3; MeCN, 5 and 6; H(2)O, 7), [Cu(H(2)BPZ)(2)(NO(3))(2)] (8), and [Cd(H(2)BPZ)(CH(3)COO)(2)] (9). State-of-the-art laboratory powder diffraction methods allowed to disclose the isomorphous character of 1 and 2, as well as of 5 and 6, which feature 3D porous networks containing 1D channels of square and rhombic shape, respectively. 3, crystallizing in the relatively rare P6(1)22 space group, consists of homochiral helices of octahedral Cd(II) ions, packing in bundles mutually linked by "radial", nonplanar BPZ ligands. Finally, the dense species 8 and 9 contain parallel 2D layers of square and rectangular meshes, respectively. Thermogravimetric analyses witnessed the relevant thermal robustness of all the [M(BPZ)] materials [except the mercury(II) derivative], which are stable in air at least up to 300 °C, with the zinc(II) derivative decomposing only around 450 °C. Variable-temperature powder diffraction experiments highlighted the permanent porosity of 1-3, 5, and 6, retained along consecutive temperature cycles in all cases but 3. When probed with N(2) at 77 K, 1-3 and 5-7 showed Brunauer-Emmett-Teller and Langmuir specific surface areas in the ranges 314(2)-993(11) and 509(16)-1105(1) m(2)/g, respectively.

Redetermination of diaqua-tetra-kis-(dimethyl-formamide-κO)magnesium dichloride.

The crystal structure of the title compound, [Mg(C(3)H(7)NO)(4)(H(2)O)(2)]Cl(2), in which the Mg ion lies on a crystallographic inversion centre, confirms that of the previous room-temperature study [Pavanello et al. (1995 ▶). Main Group Met. Chem.18, 9-19]. This redetermination at 113 K has improved geometry precision by almost an order of magnitude [e.g. Mg-O(w) (w = water) distances = 2.094 (4) and 2.0899 (7) Šin the old and new structures, respectively] and allowed the water H atoms to be located and their positions refined. In the crystal, O-H⋯Cl hydrogen bonds between the two aqua ligands of the complex mol-ecule and neighboring chloride counter-anions generate supra-molecular chains propagating along [010]. The dicationic [Mg(DMF)(4)(H(2)O)(2)] unit (DMF is dimethyl-formamide) adopts a slightly distorted octa-hedral geometry in which the Mg atom is coordinated by four DMF O atoms in a pseudo-tetra-gonal arrangement and two trans aqua ligands.

Reactions of trialkoxynitridomolybdenum with low-coordinate phosphorus compounds containing a P=N double bond.

The reactions of N≡Mo(OR)(3) (R = (t)Bu, (i)Pr) with (Me(3)Si)(2)NPNSiMe(3) (1), (Me(3)Si)(2)NPN(t)Bu (2), (Me(3)Si)(2)NPS(N(t)Bu) (3) and (Me(3)Si)(2)NP(NSiMe(3))(2) (4) have been studied. Reported complexes were synthesized via 1,2-addition of an Mo-OR bond across the P=N bond, resulting in four-membered metallacycles of the corresponding σ(2)λ(3)-iminophosphine or σ(3)λ(5)-iminophosphorane with trialkoxynitridomolybdenum. The structure of all new compounds was elucidated by (1)H, (13)C and (31)P NMR spectroscopy. Compounds [(Me(3)Si)(2)N-P(NSiMe(3))(O-(t)Bu)]{((t)BuO)(2)Mo≡N} (5), [(Me(3)Si)(2)N-PS(N(t)Bu)(O-(t)Bu)]{((t)BuO)(2)Mo≡N} (7), [(Me(3)Si)(2)N-P(NSiMe(3))(2)(O-(t)Bu)]{((t)BuO)(2)Mo≡N} (8) and [(Me(3)Si)(2)N-P(NSiMe(3))(2)(O-(i)Pr)]{((i)PrO)(2)Mo≡N} (12) were also characterized by single X-ray analysis and shown to be metallacycles containing the Mo atom with an intact terminal nitrido ligand.

1,3,5-Triphenyladamantane and 1,3,5,7-tetraphenyladamantane.

In 1,3,5-triphenyladamantane, C(28)H(28), (I), and 1,3,5,7-tetraphenyladamantane, C(34)H(32), (II), the molecules possess symmetries 3 and 4, and are situated across threefold and fourfold improper axes, respectively. The molecules aggregate by means of extensive C-H...pi interactions. In (I), the pyramidal shape of the molecules dictates the formation of dimers through a ;sixfold phenyl embrace' pattern. The dimers are linked to six close neighbors and constitute a primitive cubic net [H...pi = 2.95 (2) and 3.02 (2) A]. Compound (II) is isomorphous with tetraphenyl derivatives EPh(4) of group 14 (E = C-Pb) and ionic salts [EPh(4)][BPh(4)] (E = P, As and Sb). The multiple C-H...pi interactions arrange the molecules into chains, with a concerted action of CH (phenyl) and CH(2) (adamantane) groups as donors [H...pi = 3.15 (2) and 3.44 (2) A, respectively]. The additional interactions with the methylene groups (four per molecule) are presumably important for explaining the high melting point and insolubility of (II) compared with the EPh(4) analogs.

Polynuclear spin crossover complexes: synthesis, structure, and magnetic behavior of [Fe4(mu-CN)4(phen)4(L)2)]4+ squares.

Three new tetranuclear compounds of formula [Fe(4)(mu-CN)(4)(phen)(4)(L)(2))](PF(6))(4) x G where L = tris(pyridin-2-ylmethyl)amine (TPMA) [G = 0] (1), (6-methylpyrid-2-ylmethyl)-bis(pyrid-2-ylmethyl)amine (MeTPMA) [G = 0] (2), or bis(6-methylpyrid-2-ylmethyl)-(pyrid-2-ylmethyl)amine (Me(2)TPMA) [G = NH(4)PF(6)] (3) and phen = 1,10-phenanthroline) have been synthesized and characterized. The three compounds crystallize in the C2/c space group and consist of [Fe(4)(mu-CN)(4)(phen)(4)(L)(2))](4+) square shaped cations with two distinct iron(II) sites. The sites, associated with [Fe(phen)(2)(CN)(2)] and [Fe(L)(NC)(2)] moieties, are connected by cyanide bridging ligands and reside in different [FeN(4)C(2)] and [FeN(6)] ligand field strength environments. For 1, the structural features of both sites at 100 and 293 K are those of an iron(II) atom in the low-spin state, according to the magnetic properties. At 370 K the structure of the [FeN(6)] site is consistent with a quite complete change of spin state from the low-spin state to the high-spin state, a behavior confirmed by the magnetic study. Introduction of a methyl substituent in the sixth position of one or two pyridine groups to get MeTPMA or Me(2)TPMA derivatives, respectively, induce in 2 and 3 notable steric constraint in the [FeN(6)] site making longer the average Fe-N bond distances thereby weakening the ligand field strength and stabilizing the high-spin state. The [FeN(4)C(2)] site remains in the low-spin state in the three compounds.

Polar hydrogen-bonded organic chains in 4,4'-bipyrazolium bromide and perchlorate monohydrates.

4,4'-Bipyrazolium [or 4-(1H-pyrazol-4-yl)pyrazolium] bromide monohydrate, C6H7N4+.Br-.H2O, and 4,4'-bipyrazolium perchlorate monohydrate, C6H7N4+.ClO4-.H2O, have closely related layered structures involving tight stacks of antiparallel N-H...N hydrogen-bonded polar bipyrazolium chains [N...N = 2.712 (3) and 2.742 (2) A], which are crosslinked by hydrogen bonds with water molecules and counter-anions.

Construction of extended networks with a trimeric pyrazole synthon.

A H-bonded pyrazole trimeric motif drives the self-association of bifunctional tetramethyl-4,4'-bipyrazole, yielding highly interpenetrated 3D frameworks and allowing the engineering by design of a novel supramolecular isomer.

Mixed-anion complexes with a bipyrazolyl ligand. A new entry to a realm of three-dimensional five-connected coordination topologies.

Cross-linking of corrugated square grid coordination layers by anionic bridging groups generates five-connected coordination networks; the 3D topologies of mixed-anion cobalt(II) and nickel(II) complexes with a tetramethyl-substituted 4,4'-bipyrazolyl ligand are supported by mu-SO4(2-) functions and exist as neutral or cationic five-connected arrays involving additional terminal (NCS-) or non-coordinated (NO3-, ClO4-) groups.