Synthesis and characterisation of dimeric eight-coordinate lanthanide(III) complexes of a macrocyclic tribenzylphosphinate ligand.

The macrocyclic ligand 1,4,7,10-tetraazacyclododecane-1,4,7-triyl(methylenebenzyl-phosphinic acid) H3L3, has been prepared and its complexes with Eu, Gd and Tb(III) studied by NMR, relaxometry, luminescence and single crystal X-ray crystallography. In solution and in the crystal, the complexes have eight-coordinate metal centres with bridging phosphinate groups linking the two twisted square antiprismatic coordination polyhedra. A single stereoisomer crystallises from solution with an RRR and SSS configuration at the P centres in each sub-unit. The relaxivity of [GdL3]2 is low (1.9 mM−1 s−1, 298 K, 20 MHz), consistent with the absence of any proximate water molecules. The terbium dimer possesses a relatively long excited state lifetime (2.47 ms, 298 K)

Controlling emission energy, self-quenching, and excimer formation in highly luminescent N C N-coordinated platinum(II) complexes

A series of cyclometalated platinum(II) complexes have been prepared, [PtLnCl], containing NCN-coordinating, terdentate ligands based on 1,3-dipyridylbenzene (HL1), incorporating aryl substituents at the central 5 position of the ligand. All of the new complexes are intensely luminescent in a degassed solution at 298 K ( = 0.46-0.65 in CH2Cl2) with lifetimes in the microsecond range (7.9-20.5 s). The introduction of the aryl substituents leads to a red shift in the lowest-energy, intense charge-transfer absorption band compared to [PtL1Cl] (401 nm in CH2Cl2), in the order H 100 nm. The X-ray structures of the biphenylyl- and methyl-substituted complexes are reported, together with those of the 2-pyridyl- and mesityl-substituted ligands and the key synthetic intermediate 1-bromo-3,5-di(2-pyridyl)benzene

Alkyl and aryl dicationic derivatives of cyclic triphosphenium ions

Direct alkylation of cyclic triphosphenium ions by triflates to give di-ium dications is only possible for small organic substituents on the attacking reagent. The dicationic products are not intrinsically unstable, however, and in many instances they may be synthesised by an alternative route, pioneered by Schmidpeter and co-workers. These species may be readily identified in solution by 31P NMR spectroscopy. The crystal and molecular structures of five such derivatives have been ascertained for the first time by single crystal X-ray diffraction at 120 K. The results confirm that normal single P-P bond lengths are present in the dications, in contrast with the monocationic parent cyclic triphosphenium ions, where structural determinations have shown that the P-P bond lengths are intermediate between single and double bonds. © The Royal Society of Chemistry

Self-assembled polymetallic square grids ([2 × 2] M4, [3 × 3] M9) and trigonal bipyramidal clusters (M5)—structural and magnetic properties.

New self-assembled grids and clusters are reported, with square [2 × 2] M4 (M = Mn(II)4, Cu(II)4), trigonal-bipyramidal Mn(II)5, and square [3 × 3] M9 (M = Mn(II), Cu(II)) examples. These are based on a series of ditopic and tritopic hydrazone ligands involving pyridine, pyrimidine and imidazole end groups. In all cases the metal centres are bridged by hydrazone oxygen atoms with large (>125°) bridge angles, leading to antiferromagnetic exchange for all the Mn systems (J = −2 to −5 cm−1), which results in S = 0 (Mn4), and S = 5/2 (Mn5, Mn9) ground states. The copper systems have a 90° alternation of the Jahn–Teller axes within the Cu4 and Cu8 grid rings (Cu9), which leads to magnetic orbital orthogonality, and dominant ferromagnetic coupling. For the Cu9 grid antiferromagnetic exchange between the ring and the central copper leads to a S = 7/2 ground state, while for the Cu4 grids S = 4/2 ground states are observed. The magnetic data have been treated using isotropic exchange models in the cases of the Cu4 and Cu9 grids, and the Mn5 clusters. However due to the enormity of a fully isotropic calculation a simplified model is used for the Mn9 grid, in which the outer Mn8 ring is treated as the equivalent of an isolated magnetic chain, with no coupling to the central metal ion

Informality in organization and research : a review and a proposal

The growing interest in informal and emergent features of organizations has accompanied changes both in the dominant forms of organization and prevailing academic views about how best to think about and research them. It is argued here that currently espoused dichotomous characterizations of both organizations and research approaches are over-simplified and misleading. A review of types of organisation research is conducted and it is suggested that the relationship between theory and data collection provides a more detailed and illuminating taxonomy than a distinction between qualitative and quantitative research. Two major distinctions are proposed: [1] between theory driven and phenomenon driven research; [2] between descriptive and prescriptive theory. It is suggested that organization theory is properly prescriptive in nature. The place of informality in organization and management studies is explicated, drawing on insights from Wittgenstein and ethnomethodology (EM). A distinction is drawn between [1] the degree of formality in particular organizational settings and [2] the necessarily informal foundations of formal organizational schemes and methods. Finally, the organization of research itself is addressed. A prescriptive theory (TFV) is suggested as a means of organizing and accounting for the research process. This suggestion serves as both [1] a proposal for research management and [2] an illustration of the relationship between theory and organization

On the role of the counter-ion in defining water structure and dynamics : order, sructure and dynamics in hydrophilic and hydrophobic gadolinium salt complexes

The crystal structures of the hydrated salts of [Gd.DOTAM]3+ and its more hydrophobic derivative [Gd.2]3+, bearing 4 -phenylethyl groups, (both Gd and Yb salts) are reported and compared. The nature of the anion determines the degree of ordering in the lattice and the extent of hydration. These effects are correlated with the results of 17O and 1H NMR measurements of water exchange dynamics in solution. With [Gd.DOTAM]3+, structural ordering or the extent of hydration in the hydrated lattice follows the sequence Cl– > Br– > I– and this order also defines the water exchange rate in solution: 7.3, 19.5, 33.3 × 104 s–1 (298 K), respectively. For [Gd.2]3+ salts, the measured relaxivity is determined purely by the outer sphere term and the water exchange rate at 298 K is very similar (typically 1 × 104 s–1) for chloride, bromide, iodide, acetate, triflate and nitrate salts, notwithstanding the different nature and extent of hydration found in the crystalline lattice

Use of near-infrared spectroscopy and least-squares support vector machine to determine quality change of tomato juice*

Near-infrared (NIR) transmittance spectroscopy combined with least-squares support vector machine (LS-SVM) was investigated to study the quality change of tomato juice during the storage. A total of 100 tomato juice samples were used. The spectrum of each tomato juice was collected twice: the first measurement was taken when the tomato juice was fresh and had not undergone any changes, and the second measurement was taken after a month. Principal component analysis (PCA) was used to examine a potential capability of separating juice before and after the storage. The soluble solid content (SSC) and pH of the juice samples were determined. The results show that changes in certain compounds between tomato juice before and after the storage period were obvious. An excellent precision was achieved by LS-SVM model compared with discriminant partial least-squares (DPLS), soft independent modeling of class analogy (SIMCA), and discriminant analysis (DA) models, with 100% of a total accuracy. It can be found that NIR spectroscopy coupled with LS-SVM, DPLS, SIMCA, and DA can be used to control the quality change of tomato juice during the storage