Lucy M. Bull

Influence of cationic phosphorus dendrimers on the surfactant-induced synthesis of mesostructured nanoporous silica

The concomitant use of polycationic dendrimers and cationic surfactants for the elaboration of periodic mesoporous silica of type MCM-41 is described. The hexagonal structure is preserved up to about 26% in weight of dendrimer included in the silica. The cationic surfactant can be selectively removed to liberate the pores, while preserving the non-covalently incorporated dendrimers. These dendrimers included in the mesoporous silica are fully accessible through the mesoporous volume to small molecules such as HCl and tetrahydrofuran.

Behaviour of the one-dimensional, inorganic polymer 1∞[MPS4]– anions (M=Ni, Pd) in organic solutions

The behaviour of the KMPS 4 (M=Ni, Pd) salts and some solid-solution phases, KNi x Pd 1–x PS 4 , when dissolved in dimethylformamide (DMF) have been studied. For KNiPS 4 -DMF the novel re-arranged molecular bowl-like [Ni 3 P 3 S 12 ] 3– trianion can be formed from solutions that have been heated at 323 K for 2 days and K + exchanged by larger organic cations such as PPh 4 + (tetraphenylphosphonium), TMA + (tetramethylammonium), TEA + (tetraethylammonium), and MEM + (methylethylmorpholinium). This remarkable dispersion/auto-fragmentation/re-arrangement sequence extends the concept of mere excision in solution of monomeric molecular motifs from low-dimensional inorganic solids. Investigations by electrospray mass spectrometry (ESMS), 31 P solution-state NMR and optical microscopy under polarized light of KNiPS 4 in DMF have shown that chains of[MPS 4 ] – exist intact in freshly prepared solutions. These solutions show transient birefringence under stress. ESMS and NMR studies of KNiPS 4 solutions show that the [NiPS 4 ] – chains are quickly broken down at ambient temperature and that cyclic [Ni 3 P 3 S 12 ] 3– trianions are formed. By contrast, the [PdPS 4 ] – chain remains intact at temperatures up to 323 K. This behavioural difference can be understood in terms of the Ni-S and Pd-S bond strengths. ESMS spectra of aged KNi x Pd 1–x PS 4 /DMF solutions indicate that mixed metal trianions are formed, such as [Ni 2 PdS 12 ] 3– , [NiPd 2 P 3 S 12 ] 3– and [Ni 3 P 3 S 12 ] 3– , but no [Pd 3 P 3 S 12 ] 3– species have yet been observed.

Studies on physicochemical and catalytic properties of borosilicate zeolites

Abstract Our studies reveal that the structural defects such as framework boron sites and SiOH groups are the driving force for Pt dispersion in zeolites and that boron species remain in the zeolite framework after both Pt impregnation and dehydration. The framework boron sites in zeolites are necessary to provide acid sites of weak strength for certain catalytic reactions.

Multinuclear solid-state nuclear magnetic resonance study of 2-aminoethylferrocene and its intercalation compounds with the layered host lattices MoO3 and α-Zr(HPO4)2H2O

The isotopically labelled amino-functionalised ferrocene derivatives FcCH2CH215NH2 and Fc′CH2CH2NH2[Fc = Fe(η-C5H5)(η-C5H4); Fc′= Fe(η-C5D5)(η-C5D4)] have been synthesized. Their hydrochloride salts and the lamellar intercalation compounds MoO3(Fc′CH2CH215NH2)0.36, and Zr(HPO4)2(Fc′CH2CH215NH2)0.5(H2O)x(x= 0.1–0.5), have been studied by 2H, 15N and, in the last case, 31P solid-state NMR spectroscopy. 2H NMR lineshape analysis has probed aspects of molecular dynamical behaviour. The 2H NMR studies are consistent with rapid reorientation of the η-C5D5 ring about the Fe-ring centroid axis. The deuterons of the η-C5D4CH2CH2NH2 moiety appear to be static on the 2H NMR timescale. Increased averaging of the lineshapes at higher temperatures is interpreted in terms of a rapid wobbling motion of the molecular pseudo-fivefold axis with near axial symmetry, and of progressively increasing amplitude with increase in temperature. Additionally, in the case of the hydrochloride salt and the MoO3 intercalate, but not the Zr(HPO4)2H2O intercalate, a vibration of the molecule in a plane perpendicular to the ferrocene molecular axis, in a manner whereby the molecules are ‘anchored’ at the substituent, is suggested.The 15N CP/MAS NMR spectra reveal features of the host–guest bonding. The spectra of the intercalates are significantly different from those for FcCH2CH215NH2 and [FcCH2CH215NH3]+Cl–. For MoO3(FcCH2CH215NH2)0.36 the 15N NMR shows two distinct environments for 15N within the layers. The major resonance is apparently intermediate between that for [FcCH2CH215NH3]+Cl– and FcCH2CH215NH2, whilst the other minor resonance has been tentatively assigned to a species resulting from oxidation of the guest molecules during the intercalation reaction. The 15N and 31P CP/MAS NMR spectra of Zr(HPO4)2(FcCH2CH2l5NH2)0.5(H2O)x(x= 0.1–0.5) support the hypothesis that the amine is interacting with the acidic layers through P-O ⋯ H-N hydrogen bonds.