Timothy J. Prior

Ligand flexibility and framework rearrangement in a new family of porous metal–organic frameworks

Ligand flexibility permits framework rearrangement upon evacuation and gas uptake in a new family of porous MOFs.

Putting pressure on elusive polymorphs and solvates

The reproducible crystallisation of elusive polymorphs and solvates of molecular compounds at high pressure has been demonstrated through studies on maleic acid, malonamide, and paracetamol. These high-pressure methods can be scaled-up to produce ‘bulk’ quantities of metastable forms that can be recovered to ambient pressure for subsequent seeding experiments. This has been demonstrated for paracetamol form II and paracetamol monohydrate. The studies also show that the particular solid form can be tuned by both pressure and concentration.

In situ characterization of elusive salt hydrates. The crystal structures of the heptahydrate and octahydrate of sodium sulfate.

An important intermediate phase in the crystallization of aqueous solutions of sodium sulfate is the highly metastable sodium sulfate heptahydrate (Na(2)SO(4).7H(2)O). This has been structurally characterized for the first time by in situ single crystal X-ray diffraction. The crystal structure shows that each sodium cation is octahedrally coordinated to water molecules, with a slight distortion due to one of the water molecules being disordered. The hydrated sodium cations are hydrogen-bonded to form a three-dimensional bonded network, which is markedly different from the architecture of one-dimensional bonded chains observed in sodium sulfate decahydrate (mirabilite). This major structural difference explains the reconstructive nature of the transformation observed between the heptahydrate and mirabilite. High-pressure crystallization of a 3.41 mol/kg water aqueous solution of sodium sulfate at 1.54 GPa in a diamond-anvil cell resulted in the formation of a previously unknown sodium sulfate hydrate, which we have determined by single crystal X-ray diffraction methods to be an octahydrate, Na(2)SO(4).8H(2)O. In this structure the sulfate ions are coordinated directly to sodium ions. This resembles anhydrous sodium sulfate (thenardite) but contrasts with the heptahydrate and decahydrate in which the sodium ions are coordinated exclusively by water molecules. This observation demonstrates how the delicate balance of inter- and intramolecular bonds in the crystal structure can be significantly altered by the application of pressure.

Ionothermal synthesis, structure and characterization of three-dimensional zinc phosphates.

The first metal phosphate analogue of the zeolite Na-J (framework type JBW) has been synthesized by an ionothermal approach along with zincophosphate thomsonite.

Designed layer assembly: a three-dimensional framework with 74% extra-framework volume by connection of infinite two-dimensional sheets.

A coordination polymer with 74% extra-framework volume is prepared by predictable linking of the honeycomb network to generate a framework-structured solid designed with two distinct connecting ligands.

Macrocyclic scaffolds derived from p-aminobenzoic acid.

The regiospecific synthesis of C3 macrocyclic scaffolds possessing multiple different functional groups is described.

Crystal engineering of a 3-D coordination polymer from 2-D building blocks

Linking of ‘all chair’ two-dimensional honeycomb nnetworks, structurally analogous to CFx, with the n4-aminopyridine ligand leads to a three-dimensional molecular nframework.

A dense coordination polymer bearing an extensive and highly intricate hydrogen bonding array

Linking of hydrogen bonded sheets by coordination polymer nchains produces a three-dimensional solid derived from two distinct nstructural components.

High-pressure studies of palladium and platinum thioether macrocyclic dihalide complexes.

The mononuclear macrocyclic Pd(II) complex cis-[PdCl2([9]aneS3)] ([9]aneS3 = 1,4,7-trithiacyclo-nonane) converts at 44u2005kbar into an intensely coloured chain polymer exhibiting distorted octahedral coordination at the metal centre and an unprecedented [1233] conformation for the thioether ligand. The evolution of an intramolecular axial sulfur-metal interaction and an intermolecular equatorial sulfur-metal interaction is central to these changes. High-pressure crystallographic experiments have also been undertaken on the related complexes [PtCl2([9]aneS3)], [PdBr2([9]aneS3)], [PtBr2([9]aneS3)], [PdI2([9]aneS3)] and [PtI2([9]aneS3)] in order to establish the effects of changing the halide ligands and the metal centre on the behaviour of these complexes under pressure. While all complexes undergo contraction of the various interaction distances with increasing pressure, only [PdCl2([9]aneS3)] undergoes a phase change. Pressure-induced I...I interactions were observed for [PdI2([9]aneS3)] and [PtI2([9]aneS3)] at 19u2005kbar, but the corresponding Br...Br interactions in [PdBr2([9]aneS3)] and [PtBr2([9]aneS3)] only become significant at much higher pressure (58u2005kbar). Accompanying density functional theory (DFT) calculations have yielded interaction energies and bond orders for the sulfur-metal interactions.

Biomimetic polyorganosiloxanes: model compounds for new materials.

The chemistry of N-organosilylalkyl-substituted heterocyclic bases (thymine, adenine and cytosine) is described, covering the structures of model compounds, the synthesis of substituted oligo-siloxanes and a preliminary report of the synthesis of a poly(organosiloxane) with pendant N-alkyl(heterocycle) functionalities. N-Alkenylthymines CH2=CH(CH2)(n)T (T = thymine, n = 1 (1), 2 (2), 3 (3)) have been prepared and 2 hydrosilylated to form PhMe2Si(CH2)4T (5). Alternatively, 5 was prepared by reaction of PhMe2Si(CH2)4Br (6) with (O,O-SiMe3)2T, a method which has also been used to prepare PhMe2Si(CH2)4A (7) and PhMe2Si(CH2)4C (8) (A = adenine, C = cytosine). Model di- and tri-siloxanes [Br(CH2)4(Me)2Si]2O (10), Me3SiOSi(Me)2(CH2)4Br (11), PhMe2SiOSi(Me)2(CH2)4Br (12) and (Me3SiO)2(Me)Si(CH2)4Br (13) have been prepared by hydrosilylation of H2C[double bond, length as m-dash]C(H)(CH2)4Br with an appropriate hydrosiloxane and used to prepare Me3SiO(Me)2Si(CH2)4T (14), Me3SiO(Me)2Si(CH2)4A (15) (both from 11), and (Me3SiO)2(Me)Si(CH2)4T (16), (Me3SiO)2(Me)Si(CH2)4A (17) (both from 13). 10 reacts with thymine to give a mixture of the pyrimidocyclophane cyclo-T-N,N-[(CH2)4(Me)2Si]2O (19) and [T(CH2)4Si(Me)2]2O (20), while cytosine reacts similarly to form cyclo-C-N,N-[(CH2)4(Me)2Si]2O (21; as an imine) and [C(CH2)4Si(Me)2]2O (22); adenine only generates [A(CH2)4Si(Me)2]2O (18) in an analogous synthesis. Using a related protocol, polymeric {[MeSi(O)(CH2)4Br]2[Me2SiO]98}n (23) has been converted to {[MeSi(O)(CH2)4T]2[Me2SiO]98}n (24) and {[MeSi(O)(CH2)4A]2[Me2SiO]98}n (25). The structures of 4, 5, 8, 19 and 21, along with a 2u2009:u20091 adduct of 5 with Ni(dithiobiuret)2 (9) are reported.