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A new family of electron-deficient tris(aryl)boranes, B(C6F5)3–n(C6Cl5)n (n = 1–3), has been synthesized, permitting an investigation into the steric and electronic effects resulting from the gradual replacement of C6F5 with C6Cl5 ligands. B(C6F5)2(C6Cl5) (3) is accessed via C6Cl5BBr2, itself prepared from donor-free Zn(C6Cl5)2 and BBr3. Reaction of C6Cl5Li with BCl3 in a Et2O/hexane slurry selectively produced B(C6Cl5)2Cl, which undergoes B–Cl exchange with CuC6F5 to afford B(C6F5)(C6Cl5)2 (5). While 3 forms a complex with H2O, which can be rapidly removed under vacuum or in the presence of molecular sieves, B(C6Cl5)3 (6) is completely stable to refluxing toluene/H2O for several days. Compounds 3, 5, and 6 have been structurally characterized using single crystal X-ray diffraction and represent the first structure determinations for compounds featuring B–C6Cl5 bonds; each exhibits a trigonal planar geometry about B, despite having different ligand sets. The spectroscopic characterization using 11B, 19F, and 13C NMR indicates that the boron center becomes more electron-deficient as n increases. Optimized structures of B(C6F5)3–n(C6Cl5)n (n = 0–3) using density functional theory (B3LYP/TZVP) are all fully consistent with the experimental structural data. Computed 11B shielding constants also replicate the experimental trend almost quantitatively, and the computed natural charges on the boron center increase in the order n = 0 (0.81) < n = 1 (0.89) < n = 2 (1.02) < n = 3 (1.16), supporting the hypothesis that electrophilicity increases concomitantly with substitution of C6F5 for C6Cl5. The direct solution cyclic voltammetry of B(C6F5)3 has been obtained for the first time and electrochemical measurements upon the entire series B(C6F5)3–n(C6Cl5)n (n = 0–3) corroborate the spectroscopic data, revealing C6Cl5 to be a more electron-withdrawing group than C6F5, with a ca. +200 mV shift observed in the reduction potential per C6F5 group replaced. Conversely, use of the Gutt

We report the simultaneous electroanalytical determination of Pb2+ and Cd2+ by linear sweep anodic stripping voltammetry (LSASV) using an antimony nanoparticle modified boron doped diamond (Sb-BDD) electrode. Sb deposition was performed in situ with the analytes, from a solution of 1 mg L-1 SbCl3 in 0.1 M HCl (pH 1). Pb2+ inhibited the detection of Cd2+ during simultaneous additions at the bare BDD electrode, whereas in the presence of antimony, both peaks were readily discernable and quantifiable over the linear range 50-500 mu g L-1. Ex situ AFM characterization of the BDD electrode after Sb deposition showed a distribution of nanoparticles ranging from 3 to 110 nm in height, and 8.5 to 506.5 nm in diameter across the electrode surface, which corresponded well to the low mass of Sb expected on the BDD with respect to the voltammetric data.

The electrochemical opening of closed-ended, pristine single-walled carbon nanotubes (SWCNTs) upon the application of either a sufficiently oxidizing or reducing electrode potential is reported. Hitherto, it has been unclear whether the side walls of SWCNTs are electrochemically active, or whether, like their multiwalled counterparts (MWCNTs), the electroactive sites on SWCNTs also reside at the edge-plane-like defects at the open ends of the tubes. Evidence is presented herein that suggests the latter case is true, i.e., that SWCNTs require edge-plane sites to be electroactive. Comparisons of the voltammetric response of end-closed SWCNTs (EC-SWCNTs), end-open (EO-SWCNTs), and SWCNTs encapsulating a metal halide filling (MX@SWCNTs, where MX represents either NaI or CuI) in aqueous electrolytes indicate that SWCNTs undergo electrochemical opening if the applied electrode potential is greater than +1.2 V vs SCE or less than -1.5 V vs SCE. This was further confirmed using ex situ X-ray photoelectron spectroscopy. The nonaqueous voltammetry of NaCl@SWCNTs, NaI@SWCNTs, CuI@SWCNTs, and ZnCl2@SWCNTs in dimethyl formamide (DMF) containing 0.1 M tetrabutyl ammonium perchlorate (TBAP) all exhibited voltammetric responses identical to that of EC-SWCNTs unless the potential was cycled beyond ca. +1.6 V vs Ag (+2.129 V vs the cobaltocene/cobaltocenium redox couple) whereupon voltammetry corresponding to the filling material was observed, again indicating that the SWCNTs had become open-ended. Evidence for quantized charging of the EC-SWCNTs is presented in terms of the unusual "bow-tie" shape of the background charging current in DMF is also presented.

We report the simultaneous electroanalytical determination of Pb2+ and Cd2+ by square-wave anodic stripping voltammetry (SWASV) using a bismuth nanoparticle modified boron doped diamond (Bi-BDD) electrode. Bi deposition was performed in situ with the analytes, from a solution of 0.1 rnM Bi(NO3)(3) in 0.1 M HClO4, (pH 1.2), and gave detection limits of 1.9 mu g L-1 and 2.3 mu g L-1 for Pb(II) and Cd(II) respectively. Pb2+ and Cd2+ could not be detected simultaneously at a bare BDD electrode, whilst on a bulk Bi macro electrode (BiBE) the limits of detection for the simultaneous determination of Pb2+ and Cd2+ were ca. ten times higher. In situ atomic force microscopy (AFM) was performed to characterize the Bi nanoparticle growth on the BDD surface over a period of 120 s. The average final size of the Bi nanoparticles was 45 +/- 25 nm in height with a number density on the electrode surface of ca. 7 x 10(9) np/cm(2) obtained. The in situ AFM characterization suggests that the Bi nanoparticles are deposited by an "instantaneous" nucleation and growth mechanism.