Heterotopic helicand for designing heterometallic helicates

A new diazine tetratopic helicand, H4L, is obtained from 3-formylsalicylic acid and hydrazine. The reaction between H4L and cobalt(II) perchlorate, iron(III) perchlorate, and sodium carbonate leads to triple-stranded tetranuclear anionic helicates, [L3Co(II)2Fe(III)2]2-, which are connected through Na ions, resulting in chiral coordination polymers, [L3Na2Fe2Co2(H2O)4(EtOH)2].3H2O.     

Triplet energy back transfer in conjugated polymers with pendant phosphorescent iridium complexes

The nature of Dexter triplet energy transfer between bonded systems of a red phosphorescent iridium complex 13 and a conjugated polymer, polyfluorene, has been investigated in electrophosphorescent organic light-emitting diodes. Red-emitting phosphorescent iridium complexes based on the [Ir(btp)(2)(acac)] fragment (where btp is 2-(2'-benzo[b]thienyl)pyridinato and acac is acetylacetonate) have been attached either directly (spacerless) or through a -(CH(2))(8)- chain (octamethylene-tethered) at the 9-position of a 9-octylfluorene host. The resulting dibromo-functionalized spacerless (8) or octamethylene-tethered (12) fluorene monomers were chain extended by Suzuki polycondensations using the bis(boronate)-terminated fluorene macromonomers 16 in the presence of end-capping chlorobenzene solvent to produce the statistical spacerless (17) and octamethylene-tethered (18) copolymers containing an even dispersion of the pendant phosphorescent fragments. The spacerless monomer 12 adopts a face-to-face conformation with a separation of only 3.6 A between the iridium complex and fluorenyl group, as shown by X-ray analysis of a single crystal, and this facilitates intramolecular triplet energy transfer in the spacerless copolymers 17. The photo- and electroluminescence efficiencies of the octamethylene-tethered copolymers 18 are double those of the spacerless copolymers 17, and this is consistent with suppression of the back transfer of triplets from the red phosphorescent iridium complex to the polyfluorene backbone in 18. The incorporation of a -(CH(2))(8)- chain between the polymer host and phosphorescent guest is thus an important design principle for achieving higher efficiencies in those electrophosphorescent organic light-emitting diodes for which the triplet energy levels of the host and guest are similar.     

Reactions inside a porous nanocapsule/artificial cell: encapsulates' structuring directed by internal surface deprotonations

In the cavities of unprecedentedly functionalised, spherical, porous capsules of the type {Pentagon}12{Linker}30 identical with [{(Mo)Mo5O21(H2O)6}12{Mo2O4(ligand)}30]n- reactions with the ligands -i.e. at the internal shell surfaces - can be performed, in the present case deliberate aquation/hydration and deprotonation reactions at the linker fragments {(Mo2O4)C2O4H}+ similar to that reported in the literature for [(NH3)5CoC2O4H]2+ in solution.     

Strong axiality and Ising exchange interaction suppress zero-field tunneling of magnetization of an asymmetric Dy2 single-molecule magnet

The high axiality and Ising exchange interaction efficiently suppress quantum tunneling of magnetization of an asymmetric dinuclear Dy(III) complex, as revealed by combined experimental and theoretical investigations. Two distinct regimes of blockage of magnetization, one originating from the blockage at individual Dy sites and the other due to the exchange interaction between the sites, are separated for the first time. The latter contribution is found to be crucial, allowing an increase of the relaxation time by 3 orders of magnitude.     

Complexes of aryl-substituted porphyrins and naphthalenediimide (NDI): investigations by synchrotron X-ray diffraction and NMR spectroscopy

New donor-acceptor hybrids of Zn(II)-metallated 5,15-diaryl porphyrins have been designed and synthesised via the porphyrin interactions with an electron acceptor molecule, di-n-hexyl N-substituted 1,2,4,8-naphthalenetetracarboxylic diimide (NDI). Binding interactions within these supramolecular complexes were investigated in the solid state by synchrotron X-ray diffraction and probed in solution by (1)H NMR spectroscopy. The systematic modulation of the porphyrin π-density was achieved, for the first time as multiple methoxy and fluorine groups were introduced as substituents to the 5,15-diaryls of the porphyrin. For these, the variation of the porphyrin-NDI binding strengths determined by (1)H NMR titrations was shown, using the Swain's type dual parameter approach, to be closely linked with the peripheral substitution pattern of the diaryl porphyrins validated by crystallography. The new 1:1 donor-acceptor complexes formed display characteristic features of the aromatic-stacked systems, i.e. the parallel arrangement and short interplanar separation between the substituted porphyrin and NDI. Synthetic modification of electron-density on the porphyrin surface by introducing substituents at peripheral sites of functionalised porphyrins represent a general solution towards electronically tunable aromatic surfaces: an understanding of their solution and solid state behaviour will significantly improve the rational design of new functional donor-acceptor supramolecular materials with potential applications ranging from new energy materials to dye-sensitised solar cells, photovoltaics and future drug delivery devices.     

4‐(Azulen‐1‐yl) six‐membered heteroaromatics substituted with thiophen‐2‐yl or furan‐2‐yl moieties in 2 and 6 positions

Pyranylium perchlorates with azulen‐1‐yl moiety in 4‐position and thiophen‐2‐yl or furan‐2‐yl in 2 and 6‐positions were obtained by the substitution of 4‐chloro corresponding salts with azulenes. The pyranylium salts are used as starting materials for the synthesis of pyridine and pyridinium salts. The products were characterized and for pyridines pKa was spectroscopically determined. Several attempts were made for pyridine complexation with metal cations as Hg²⁺ or Ag⁺. J. Heterocyclic Chem., (2011).     

Polyhydrosilanes I. Synthesis

Abstract

Using the well known Wurtz coupling technique, polyhydrosilanes copolymers with diphenyl - and methyl(phenyl) - sequences, were synthesised. This work describes the possibility to maintain stable Si-H group and to obtain in good yields, soluble, high molecular, functional polysilanes. IR, ¹-NMR, ¹³C, UV spectral data, quantitative elemental Si and H (from Si-H) analyses and indirect molecular weight investigation sustain the molecular structure of the copolysilanes.     

Outdoor 222Radon concentrations monitoring in relation with particulate matter levels and possible health effects

Air quality monitoring could potentially improve exposure estimates for use in epidemiological studies. We investigated air quality by monitoring concentrations of ²²²Rn near the ground and particulate matter (PM) with an aerodynamic diameter less than or equal to 10 μm (PM10) and 2.5 μm (PM2.5) for Bucharest-Magurele periurban area. Atmospheric radon concentrations have been continuously monitored near the ground at 1 m height as well as at 10 m height. This paper presents time-series of radon concentrations monitoring in air near the ground measured during 1 January 2011–1 January 2012 by use of solid state nuclear track detectors SSNTD CR-39, exposed for 10 days periods. The daily average atmospheric radon concentration near the ground registered at 1 m height was found to be in range of 40.25 ± 7.53 Bq/m³, which was comparable with the daily average radon concentration of 44.92 ± 9.94 Bq/m³ recorded for period 1 August 2011–20 December 2011 at 10 m height by AlphaGUARD Radon monitor. Also, was done a comparative analysis of spatio-temporal variations in time series of outdoor radon concentration and PM in two size fractions (PM10 and PM2.5) in Bucharest Magurele area for 2011 year. The predominant recorded component in PM10 was PM2.5. Observational results show that recorded yearly average PM2.5 and PM10 concentrations were 35.96 μg/m³ and 40.91 μg/m³, respectively. The average ratio of PM2.5/PM10 was 87.9 % at this sampling site. However, in densely populated Bucharest urban and suburban areas the mean daily EC limit values for PM10, PM2.5 and attached ²²²Rn are frequently exceeded leading to serious public concern during the last years. The ambient air pollution measurements like as PM10 and PM2.5 levels are used as a proxy for personal exposure levels. Have been investigated also meteorological effects on the temporal patterns of atmospheric radon and particle matter.     

Sequential dehydrogenation–arylation of diisopropylamine–borane complex catalyzed by palladium nanoparticles

Palladium nanoparticles have been prepared using different techniques, CO₂-assisted microfluidics coflow or thermolysis using ionic liquids. Both techniques displayed interesting activities in dehydrogenation of diisopropylamine–borane complex, and allowed performing a dehydrogenation–arylation sequence with the creation of a carbon–boron bond.     

Dual‐emissive polydiphenylsilane nanocomposite: effect of N,N′‐bis(4‐hydroxysalicylidene)‐1,2‐phenylenediamine‐Zn complex

The fluorescence properties of polysilane can be strongly influenced by creating new excited states that involve electronic transitions and the relaxation to the ground state. This work presents the optical effects obtained by doping a specially designed polydiphenylsilane copolymer with Zn complex of N,N′‐bis(4‐hydroxysalicylidene)‐1,2‐phenylenediamine. The nanocomposites have been prepared in solution by mixing the polymer with low amounts of Zn–salophen and using tetrahydrofuran as solvent. The ultraviolet–visible spectrum has shown the occurrence of an intermolecular charge transfer between polysilane and the metal complex. Photoluminescence studies have revealed an interesting dual emission profile of nanocomposite. The origin of this phenomenon has been evidenced by molecular modeling and simulation of the electronic transitions. The modeling results have unveiled a new low‐lying excited state due to intermolecular interactions. The thin films of nanocomposites have been drop‐casted from solutions. The obtained films have been studied by Transmission Electron Microscopy (TEM)‐Scanning Transmission Electron Microscopy (STEM)‐Energy Dispersive X‐ray analysis (EDX) to gain information on the film‐forming capacity and surface morphology. The results have revealed a high potential of such materials for fluorescence sensing applications. Copyright © 2015 John Wiley & Sons, Ltd.