Conrad W. Ingram

Characteristics of the synthetic heulandite-clinoptilolite family of zeolites

Heulandite-clinoptilolite zeolites can be synthesized over the complete range of Si/Al ratio (2.5 to 6) found for the natural minerals. The unit cell parameters, framework infrared vibrational characteristics and thermal properties are similar to those of their natural counterparts. Results of environmental studies involving the removal of toxic metal ions such as lead, strontium and cesium from solution show that though natural clinoptilolite efficiently removes these ions from solution, the higher aluminum content of heulandite results in an improvement in the capacity of this topology for divalent cations. The ability to readily prepare synthetic heulandite and clinoptilolite using environmentally benign methods is expected to lead to improvements in the use of this family of zeolites for similar environmental applications.

Metal substituted aluminophosphate molecular sieves as phenol hydroxylation catalysts

Abstract Substitution of transition metals for either aluminum and/or phosphorus in the AIPO 4 -11 framework is found to afford novel heterogeneous catalysts for liquid phase hydroxylation of phenol with hydrogen peroxide. AlPO 4 -11 is more active than SAPO-11 and MgAPO-11 for phenol conversion to hydroquinone. Substitution of transition metal cations, such as Fe, Co and Mn significantly improves the conversion of phenol. The activity follows the order of FeAPO-11 > CoAPO-11 > FeMnAPO-11 > MnAPO-11 ≫ AlPO 4 -11. FeAPO-11, FeMnAPO-11 and CoAPO-11 give similar product selectivities of about 1:1 hydroquinone (HQ) to catechol (CT) whereas MnAPO-11 favors the production of catechol. FeAPO-11 show comparable performance to TS-1 (titanium silicate with MFI topology) for phenol conversion, with TS-1 giving higher selectivities toward hydroquinone. Medium pore size CoAPO-11 was more active than larger pore CoAPO-50, -36 and -5. The external surfaces of the catalysts play a significant role in these oxidation reactions.

catena-Poly[zinc-μ(3)-{3,3'-[(1,7-dioxa-4,10-diaza-cyclo-dodecane-4,10-di-yl)bis-(methyl-ene)]dibenzoato}].

The ZnII ion in the title compound, [Zn(C24H28N2O6)]n, is located on a twofold rotation axis and is at the midpoint of a crown-4 moiety of 3,3′-[(1,7-dioxa-4,10-diazacyclododecane-4,10-diyl)bis(methylene)]dibenzoate anion. It is octahedrally coordinated by two N atoms and two O atoms of the crown moiety from one ligand and two carboxylate O atoms from two bridging intra-chain ligands. Metallomacrocyclic rings are identified in the structure. The metallomacrocycle contains two ZnII ions and 14 atoms from the bridging ligands. Repetition of these units gives rise to an infinite zigzag chain along [101]. C—H⋯O hydrogen bonds occur.

Complex three-dimensional lanthanide metal–organic frameworks with variable coordination spheres based on pyrazine-2,3,5,6-tetracarboxylate

Metal–organic frameworks {[Ln4(pztc)3(H2O)11]·10(H2O)}n (Ln = Gd(1), Tb(2); pztc = pyrazine-2,3,5,6-tetracarboxylate) containing variable coordination spheres and with a complex and unusual three dimensional structure, were synthesized by the reaction of H4pztc with the respective Ln(III) salt in water under hydrothermal conditions. The compounds were characterized by single crystal X-ray crystallography, elemental and thermal analysis, and FTIR spectroscopy. The asymmetric units in these compounds have four symmetry-independent Ln(III) ions and these are octa- and nona-coordinate centers, with irregular coordination polyhedra from [Ln(pztc)2(H2O)6], [Ln(pztc)2(H2O)4], [Ln(pztc)3(H2O)3], [Ln(pztc)3(H2O)], and [Ln(pztc)4] cluster units. The fully deprotonated ligand, pztc, coordinates to the Ln3+ ions through seven or through ten of its atoms (i.e., the maximum coordination number for this ligand). The three-dimensional open framework contains irregular channels along the [001] crystallographic direction. The channels are approximately 12 A wide at their largest dimension and contain strongly hydrogen bonded water molecules of crystallization which further stabilize the structure. The solvent accessible volume is 20% of the total volume. The structures exhibit magnetic behavior that is characteristic of the respective isolated paramagnetic lanthanide ions.

A hydrogen bonded Co(II) coordination complex and a triply interpenetrating 3-D manganese(II) coordination polymer from diaza crown ether with dibenzoate sidearms

The diaza crown ether dicarboxylate ligand, 4,4′-((1,7-dioxa-4,10-diazacyclododecane-4,10-diyl)bis(methylene)dibenzoate), L, forms a monomeric coordination complex of Co(II) ions, CoL(H2O)2·2H2O, 1, and a coordination polymer (MnL·H2O)n, 2, with Mn(II) ions under hydrothermal conditions. The monomeric coordination complex (structure 1) is polar with mirror symmetry and crystallizes in the non-centrosymmetric space group Cm. The mirror plane bisects the complex at the six-coordinate Co(II) ion, the two oxygen atoms of the crown moiety and the two oxygen atoms from coordinated water molecules. The coordinated water molecules take part in strong, linear hydrogen bonds with carboxylate oxygens provided by neighboring Co(II)–crown complexes resulting in a three-dimensional (1 : 1)n polar network in which the topology of the underlying 8-coordinated net is sqc3. The structure of 2 crystallizes in the orthorhombic Fdd2 space group as an infinite, polar triply interpenetrating three-dimensional network. The eight-coordinate Mn(II) ion coordinates two oxygen and two nitrogen atoms of the crown moiety, as well as single carboxylate O atom from each of two neighboring ligands. In both structures, the ligand assumes a flexed-wing bird shape, with the two benzoate sidearms of the crown moiety locked in a syn orientation. The metal ion elevated above the plane of the diaza-crown oxygen and nitrogen atoms. The diaza-crown moiety with its two benzoate sidearms has the peculiar property of forming an oriented crystal structure where the metal-crown vectors are oriented parallel to each other in the crystal. However, the structures are achiral, but the rigid crystal lattice prevents re-orientation of the structure through inversion. The coordination polymer (MnL·H2O)n, 2, is a 3-center uninodal net with ths (ThSi2) topology. Computational results using the density functional theory (DFT) calculations explain why the flexed-wing bird shape is the preferred and most stable ligand conformation for metal ion binding. Both structures demonstrate magnetic properties that are characteristics of the respective non-interacting isolated paramagnetic transition metal ions that are present.

catena-Poly[{μ3-3,3′-[(1,7-dioxa-4,10-di­aza­cyclo­dodecane-4,10-di­yl)bis­(methyl­ene)]dibenzoato}cobalt(II)]

The title compound, [Co(C24H28N2O6)]n, crystallizes as infinite chains related to one another by inversion centers, giving a centrosymmetric coordination polymer. The CoII ion, situated on a twofold rotation axis, forms a complex with the crown-4 moiety of the 3,3′-[(1,7-dioxa-4,10-diazacyclododecane-4,10-diyl)bis(methylene)]dibenzoate anion. The distorted octahedral coordination sphere of the CoII ion is completed by two carboxylate O atoms from two bridging intra-chain ligands. Metallomacrocyclic rings of 16 atoms are present, with each ring containing two CoII ions and 14 atoms from the bridging ligands. These units repeat as infinite zigzag chains along [101].