ExperimentalThe ET2 monomer was prepared as previously reported [23]. PolyET2 films (4±6 mm thick) were deposited on indium-tin-oxide (ITO) plates by cyclic voltammetry (from ±0.2 to 1.2 V vs. SCE), of a 4.0´10 ±3 M ET2 solution in acetonitrile with TBAF (0.1 M) as the supporting electrolyte. The doping level of the polymer was changed by varying the oxidation potential (V ox ) within the range ±0.2 to +0.8 V in chronoamperometric experiments. For each explored potential, the chronoamperometry was run until very low current values were attained. All potentials are referred to the SCE. N d was calculated from the charge flow during the chronoamperometric experiments. N d was found to vary between 6.8´10 18 and 3.4´10 20 cm ±3 in the V ox range of 0 to +0.8 V. The doping level was not evaluated for V ox < 0 V because of the high error affecting the current measurement at those potentials. Immediately after electrochemical doping, the polyET2 films were removed from the ITO substrates and spread onto glass plates for electrical characterization carried out at ambient conditions. The X-ray diffraction spectra were recorded by a Philips (PW1050/81-PW1710) powder diffractometer configured in the Bragg±Brentano geometry and equipped with a graphite monochromator in the diffracted beam. Cu Ka X-radiation was employed, and the step-scanning recording was performed in the 3±50 2y range at 0.01 2y steps and with a fixed counting time of 10 s.The conductivity and R H were measured using standard van der Pauw geometry on 10´10 mm square samples. The electrical tests were carried out by placing small tips directly onto each corner of the polymer film. The measurements were performed by applying a constant current (typically 10 mA) across a pair of tips and by evaluating the voltage drop across the other electrode pair with and without the applied magnetic field (0.85 T). A detailed description of the measurement technique is reported by Mousty et al. [24]. The conductivity was found to vary between 2´10 ±5 and 3´10 1 (W cm) ±1 in the considered range of the electrochemical dopant concentration.Since the discovery of efficient room temperature light emission from porous silicon (PS), great effort has been expended to understand structural, stability, photophysical, and optoelectronic properties of PS. The consensus is that feature sizes of silicon have to be below~1 nm to evoke the short-enough radiative lifetimes needed for optoelectronic applications. While this is a challenging length scale for fabrication methods, it is a size regime where self-assembly materials chemistry may provide solutions. Herein we report a novel and very soft chemistry preparation of 1 nm silicon clusters in free-standing oriented hexagonal mesoporous silica film, OHMSF. The film displays yellow± orange photoluminescence and nanosecond luminescence lifetimes, in contrast to milli-and microsecond lifetimes for PS and nanocrystalline silicon (nc-Si). This new way of preparing light-emitting silicon clusters in oriented mesoporous silica film is purely...

The absorption spectra of Ni(H2O)6 2+, trans-NiCl2(H2O)4, and NiCl6 4- show an unusual band shape for the 3A2g → 3T1g, 1Eg (O h labels) electronic transitions in the near-infrared to visible wavelength range. A barely resolved broad band and an intense vibronic progression with a spacing larger than the totally symmetric ground-state metal−ligand vibrational frequency are superposed. Low-temperature polarized spectra are analyzed with a quantitative model and both the large interval and the band intensities are shown to arise from efficient intersystem crossings between the two excited states. Alternative assignments proposed in the literature are examined.

This paper reports the synthesis, structures, and magnetic and optical properties of a series of gadolinium(III) (1a-4a) and europium(III) (1b-4b) complexes with nitronyl or imino nitroxide radicals. The crystal structures of compounds 1a and 1b consist of [Ln(III)(radical)(2)(NO(3))(3)] entities in which the gadolinium(III) (1a) or europium(III) ion (1b) is 10-coordinated to two nitronyl nitroxide radicals and three nitrato ligands. The crystal structures of compounds 2a-4a and 2b-4b consist of [Ln(III)(hfac)(3)(radical)] entities in which the gadolinium(III) (2a-4a) or europium(III) ion (2b-4b) is 8-coordinated to one nitronyl (2a and 2b) or one imino (3a, 4a and 3b, 4b) nitroxide radical and three hexafluoroacetylacetonato ligands. The gadolinium(III) complexes (1a-4a) are isostructural with their europium(III) analogues (1b-4b). The magnetic properties of the gadolinium complexes were studied. Along the series 1a-4a only compound 2a exhibits a ferromagnetic Gd(III)-radical coupling (J(Gd-rad) = +1.7 cm(-1)), while for the others this coupling is antiferromagnetic (1a: J(Gd-rad1) = -4.05 cm(-1) and J(Gd-rad2) = -0.80 cm(-1); 3a: J(Gd-rad) = -2.6 cm(-1); 4a: J(Gd-rad) = -1.9 cm(-1)). The first full luminescence spectra of lanthanide complexes with free radical ligands are reported between 650 and 1200 nm. The rich vibronic structure in luminescence and absorption spectra indicates that several excited states define the absorption spectra between 400 and 800 nm. Qualitative trends can be established between magnetic ground state properties and the energies and fine structure of the title compounds.