Chromium(III) complexes bearing bis(benzotriazolyl)pyridine ligands: synthesis, characterization and ethylene polymerization behavior

<p>Reaction of benzotriazole with 2,6-bis(bromomethyl)pyridine and 2,6-pyridinedicarbonyl dichloride yields the tridentate ligands 2,6-bis(benzotriazol-1-ylmethyl)pyridine (<b>1</b>) and 2,6-bis(benzotriazol-1-ylcarbonyl) pyridine (<b>2</b>). The molecular structures of the ligands were determined by single-crystal X-ray diffraction. These ligands react with CrCl₃(THF)₃ in THF to form neutral complexes, [CrCl₃{2,6-bis(benzotriazolyl)pyridine-<i>N,N,N</i>}] (<b>3</b>, <b>4</b>), which are isolated in high yields as air stable green solids and characterized by mass spectra (ESI), FTIR spectroscopy, UV–Visible, thermogravimetric analysis (TGA), and magnetic measurements. After reaction with methylaluminoxane (MAO), the chromium(III) complexes are active in the polymerization of ethylene showing a bimodal molecular weight distribution. A DFT computational investigation of the polymerization reaction mechanism shows that the most likely reaction pathway originates from the <i>mer</i> configuration when the spacer is CH₂ (complex <b>3</b>) and from the <i>fac</i> configuration when the spacer is CO (complex <b>4</b>).</p

A new copper(I) coordination polymer from 2,6-bis(1<i>H</i>-benzotriazol-1-ylmethyl)pyridine: Synthesis, characterization, and use as additive in transparent submicron UV filters

<p>The use of a new copper(I) coordination polymer (CP) as additive in transparent composite films of 190 nm of thickness for ultraviolet (UV) shielding is presented. The luminescent 1-D Cu(I) CP was easily synthesized through a self-assembly process between Cu(I) iodide and 2,6-bis(1<i>H</i>-benzotriazol-1-ylmethyl)pyridine (L). The CP, [Cu₂(<i>μ</i> − I)₂(<i>μ</i> − <b>L</b>)₂]_<i>n</i>, was structurally characterized by infrared, UV–visible diffuse reflectance and photoluminescence spectroscopy, elemental and thermogravimetric analyses, single-crystal and powder X-ray diffraction, and relativistic density functional theory calculations. The CP was dispersed and immobilized into a polymeric matrix in the presence of Sudan I, yielding a composite material that exhibits a reduction of 49% of the UV transmittance at 350 nm. Thus, the use of a new Cu(I) CP in polymeric composite films appears as a novel approach toward ultrathin and transparent UV shielding films, which have potential applications as protection layers of paints and coatings that tend to degrade when exposed to UV radiation.</p