Layer or Tube? Uncovering Key Factors Determining the Rolling-up of Layered Coordination Polymers

Nanotubular materials have garnered considerable attention since the discovery of carbon nanotubes. Although the layer-to-tube rolling up mechanism has been well recognized in explaining the formation of many inorganic nanotubes, it has not been generally applied to coordination polymers (CPs). To uncover the key factors that determine the rolling-up of layered CPs, we have chosen the Co/R-, S-Xpemp [Xpemp = (4-X-1-phenylethylamino)methylphosphonic acid, X = H, F, Cl, Br] systems and study how the weak interactions influence the formation of layered or tubular structures. Four pairs of homochiral isostructural compounds R-, S-Co(Xpemp)(H₂O)₂ [X = H (1H), F (2F), Cl (3Cl), Br (4Br)] were obtained with tubular structures. The inclusion of 3,3'-azobipyridine (ABP) guest molecules led to compounds R-, S-[Co(Xpemp)(H₂O)₂]₄·ABP·H₂O with layered structures when X was Cl (5Cl) and Br (6Br), but tubular compounds 1H and 2F when X was H and F. Layered structures were also obtained for racemic compounds meso-Co(Xpemp)(H₂O)₂ [X = F (7F), Cl (8Cl), Br (9Br)] using racemic XpempH₂ as the reaction precursor, but not when X = H. A detailed study on R-6Br revealed that layer-to-tube transformation occurred upon removal of ABP under hydrothermal conditions, forming R-4Br with a tubular structure. Similar layer-to-tube conversion did not occur in organic solvents. The results demonstrate that weak interlayer interactions are a prerequisite but not sufficient for the rolling-up of the layers. In the present cases, water also provides a driving force in the layer-to-tube transformation. The experimental results were rationalized by theoretical calculations.

Assembly of a Hexameric Cluster of Polyoxomolybdotriphosphonate Builts from [Zn(H2O){TeMo6O21}{N(CH2PO3)3}]6- Subunits and Its Optical and Catalytic Properties

The crown-shaped organotriphosphonate-modified 36-molybdenum cluster (NH₄)₁₈Na₇H₁₁[Zn(H₂O)TeMo₆O₂₁{N(CH₂PO₃)₃}]₆·23H₂O (1) has been synthesized, which is the largest zinc-containing organophosphonate-based polyoxometalate to date. Compound 1 was prepared in buffer solution (pH 5.5) with heptamolybdate and amino trimethylene phosphonic acid (ATMP) as the organic ligand. The polyanion constructed from a hexmeric assembly of [Zn(H₂O){TeMo₆O₂₁}{N(CH₂PO₃)₃}]^6- subunits has been fully investigated by a few characterization methods. In this work, we discovered that 1 exhibited reversible photochromism and it changed from white to reddish brown upon UV irradiation. In addition, compound 1, as a catalyst, can oxidize sulfides to sulfoxides, showing a high yield/conversion and a good selectivity.

Polyoxotungstates incorporated organophosphonate and nickel: synthesis, characterization and efficient catalysis for epoxidation of allylic alcohols

“Top-down” synthetic strategy was performed to incorporate nickel into the organophosphonate-based POTs showing superior catalysis for the epoxidation of allylic alcohols.

Template-Directed One- and Two-Dimensional Copper(II) Diphosphonates: Structures and Characterizations of (NH(4))(2)Cu(3)(hedp)(2)(H(2)O)(4), [NH(3)(CH(2))(4)NH(3)]Cu(3)(hedp)(2).2H(2)O, and [NH(2)(C(2)H(4))(2)NH(2)]Cu(3)(hedp)(2) (hedp = 1-Hydroxyethylidenediphosphonate)

Three new copper(II) diphosphonates, (NH(4))(2)Cu(3)(hedp)(2)(H(2)O)(4) (1), [NH(3)(CH(2))(4)NH(3)]Cu(3)(hedp)(2).2H(2)O (2), and [NH(2)(C(2)H(4))(2)NH(2)]Cu(3)(hedp)(2) (3), where hedp = 1-hydroxyethylidenediphosphonate, have been synthesized and characterized by single-crystal structural analysis. Crystal data: 1, monoclinic, P2(1)/n, a = 6.2137(13) Å, b = 14.747(2) Å, c = 11.1802(12) Å, beta = 105.83(2) degrees, Z = 2; 2, triclinic, P&onemacr;, a = 7.4840(12) Å, b = 8.032(3) Å, c = 10.007(2) Å, alpha = 111.68(2) degrees, beta = 96.188(14) degrees, gamma = 96.97(2) degrees, Z = 1; 3, triclinic, P&onemacr;, a = 7.0155(6) Å, b = 8.0904(9) Å, c = 9.2644(11) Å, alpha = 112.611(13) degrees, beta = 90.819(8) degrees, gamma = 92.824(7) degrees, Z = 1. The compound 1 is composed of infinite chains with a ladder-type motif. The compounds 2 and 3 adopt a two-dimensional layer structure which contains four- and eight-membered rings assembled from vertex-sharing {CuO(4)} units and {CPO(3)} tetrahedra. The magnetic properties of 3 have been investigated.