Quadratic susceptibility and first hyperpolarizability of the complex of Cr(CO)(3) with 2.2 paracyclophane

The peculiarities of chemical bonding and nonlinear optical properties of the complex of Cr(CO)(3) with [2.2]paracyclophane (Cr-pCp) have been studied by a combined experimental-theoretical approach. The Cr-pCp complex exhibits second harmonic generation, the efficiency of which was measured by the powder technique at 1064.2 nm fundamental wavelength and estimated theoretically. The comparison of electronic structure of the Cr-pCp with benzene tricarbonyl chromium analogue has revealed an important role of intraligand charge transfer state in pCp moiety conditioned by a strong transannular interaction between aromatic rings which is responsible for the enhanced molecular hyperpolarizability of Cr-pCp

Keto-enol tautomerism and nonlinear optical properties in beta-diketones containing 2.2 paracyclophane

Nonlinear optical properties of [2.2]paracyclophane (pCp) derived beta-diketones containing functional groups with different donor-acceptor properties, bounded to the dicarbonyl fragment, have been studied. Two polymorphic modifications, one of which is characterized by the polar space group Pca2(1) while the other one is centrosymmetric (space group Pbca) were obtained for beta-diketone substituted by thiophene group depending on the crystal growth procedure. All molecules studied exhibit second harmonic generation ability, the efficiency of which was measured by the powder technique at 1064 nm fundamental wavelength. The NLO susceptibility for the compounds studied is analyzed taking into account the structural peculiarities and theoretical calculations

Aryloxy Alkyl Magnesium versus Dialkyl Magnesium in the Lanthanidocene-Catalyzed Coordinative Chain Transfer Polymerization of Ethylene

Complexes [(1,2,4-Ph3C5H2)2NdCl2K(THF)2]2 (Nd1), {[1,2-Ph2-4-(4-MeOC6H4)C5H2]2NdCl2K(THF)2}2 (Nd2), {[1,2-Ph2-4-(2-MeOC6H4)C5H2]2NdCl2[K(THF)4]}(THF)0.5 (Nd3), and [(1,2,4-Ph3C5H2)2TbCl2K]2 (Tb1) have been synthesized, studied by X-ray diffraction analysis, and used in coordinative chain transfer polymerization (CCTP) of ethylene upon activation by alkyl magnesium derivatives. The complexes Nd1 and Tb1 exhibiting similar molecular structures and the same core type have demonstrated similar catalytic activities. Two types of alkylating/chain transfer agents, namely, di-n-butyl magnesium and heteroleptic complex (BHT)Mg(THF)2 nBu Mg1 (BHT = 2,6-di-tert-butyl-4-methylphenoxide), have been studied in this reaction. We have found that (BHT)Mg(PE) products (PE is an oligoethylene chain) are being formed at a relatively high rate while using Mg1 at 40 °C in the solution polymerization of ethylene; the oligomeric products comprise more than 40 ethylene fragments, unlike Mg(PE)2 derivatives, which are obtained from MgnBu2 and contain about 20 ethylene fragments. Luminescence spectroscopy study of the reaction mixtures, while initiating the complex Tb1 by MgnBu2 or Mg1, confirmed the structural proximity and high symmetry of the catalytic complexes for both types of Mg reagents. These experimental results reaffirmed the hypothesis about the CCTP mechanism, suggesting the formation of trinuclear LnMg2 catalytic species. Within this mechanism, we can explain the increase in the polymerization degree (Pn) when Mg1 is used by growing a single oligoethylene chain (PE) per a Mg atom to form (μ-BHT)2Mg2(PE)2 species, whereas application of MgnBu2 provides the growth of two PE chains to form the Mg2(PE)4 product with lower solubility. © 2019 American Chemical Society