1795-01-3Relevant articles and documents
Role of Substituents at 3-position of Thienylethynyl Spacer on Electronic Properties in Diruthenium(II) Organometallic Wire-like Complexes
Roy, Sourav Saha,Chowdhury, Sabyasachi Roy,Mishra, Sabyashachi,Patra, Sanjib K.
, p. 3304 - 3313 (2020/09/09)
A series of organometallic complexes [Cl(dppe)2Ru?C≡C-(3-R?C4H2S)-C≡C?Ru(dppe)2Cl] (3-R-C4H2S=3-substituted thienyl moiety; R=?H, ?C2H5, ?C3H7, ?C4H9, ?C6H13, ?OMe, ?CN in 5 a–5 g respectively) have been synthesized by systematic variation of 3-substituents at the thienylethynyl bridging unit. The diruthenum(II) wire-like complexes (5 a–5 g) have been achieved by the reaction of thienylethynyl bridging units, HC≡C-(3-R-C4H2S)-C≡CH (4 a–4 g) with cis-[Ru(dppe)2Cl2]. The wire-like diruthenium(II) complexes undergo two consecutive electrochemical oxidation processes in the potential range of 0.0 - 0.8 V. Interestingly, the wave separation between the two redox waves is greatly influenced by the substituents at the 3-position of the thienylethynyl. Thus, the substitution on 3-position of the thienylethynyl bridging unit plays a pivotal role for tuning the electronic properties. To understand the electronic behavior, density functional theory (DFT) calculations of the selected diruthenium wire-like complexes (5 a–5 e) with different alkyl appendages are performed. The theoretical data demonstrate that incorporation of alkyl groups to the thienylethynyl entity leaves unsymmetrical spin densities, thus affecting the electronic properties. The voltammetric features of the other two Ru(II) alkynyl complexes 5 f and 5 g (with ?OMe and ?CN group respectively) show an apparent dependence on the electronic properties. The electronic properties in the redox conjugate, (5 a+) with Kc of 3.9×106 are further examined by UV-Vis-NIR and FTIR studies, showing optical responses in NIR region along with changes in “?Ru?C≡C?“ vibrational stretching frequency. The origin of the observed electronic transition has been assigned based on time-dependent DFT (TDDFT) calculations.
Catalytic transformations of alkylthiophenes
Mashkina,Chernov
, p. 209 - 215 (2007/10/03)
The transformations of alkylthiophenes in the presence of amorphous aluminosilicate and decationated zeolite HNaY were studied. Substituted thiophenes with R = 2- and 3-Me, 2-Et, and 2-iso-Pr undergo dealkylation to thiophene with close rates, migration of the alkyl group from the 9α- to the β-position of the thiophene ring (or in the opposite direction with an elevated rate), and decomposition with H2S elimination. The dealkylation rate of 2-substituted thiophenes with a branched-chain radical (R = iso-Pr, terf-Bu) is much higher and the elimination rate with this radical is lower than those for normal-chain radicals; the isomerization step is virtually absent. Di-, tri-, and tetrasubstituted thiophenes with R = Et and iso-Pr undergo stepwise dealkylation, which is facilitated by an increase in the degree of substitution on the thiophene ring. Thiophene and its lower homologues can be obtained by the transformation of a mixture of high-molecular thiophenes. Copyright
Thallium(III) Trifluoroacetate-Trifluoroacetic Acid in the Chemistry of Polythiophenes. 2. Treatment of 3-Alkylthiophenes and Electron Paramagnetic Resonance Results
Tormo, Jordi,Jesus Moreno,Ruiz, Jordi,Fajari, Lluis,Julia, Luis
, p. 878 - 884 (2007/10/03)
The treatment of thiophene and 3-alkylthiophenes with thallium(III) trifluoroacetate (TTFA) in trifluoroacetic acid (TFA) gives insoluble and dark powdery solids with oxygen content and electrical conductivities ranging from 10-4 to 10-6 Ω-1 cm-1. Polar and short fractions are negligible. All of them show semiconductivity (10-3Ω-1 cm-1) when doped in iodine atmosphere. Electron paramagnetic resonance (EPR) spectra of either as-synthesized or I2-treated solids display characteristic single and broad lines (ΔHPP, 1.84-7.4 G) with Lorentzian shapes and g-values in the range 2.0028-2.0038. Infrared spectra show characteristic C-H out-of-plane deformations (780 cm-1 for polythiophene and 820-825 cm-1 for poly(3-alkylthiophenes)) in addition to a strong peak at 1650-1690 cm-1 which has not been conclusively assigned. EPR spectra of some disubstituted and tetrasubstituted 2,2′-bithiophene radical cations have been observed and their g-values and coupling constants assigned when the corresponding parent compounds are photolyzed with ultraviolet light in TFA. Photolysis of 3-alkylthiophenes in TFA in the EPR instrument gave the radical cations of 4,4′-dialkyl-2,2′-bithiophenes. In no case, were EPR signals of the isomeric 3,3′-dialkyl- or 3,4′-dialkyl-2,2′-bithiophene radical cations observed, indicating that dimerization of 3-alkylthiophenes occurs through the less sterically hindered 5-position. The presence of two doublet species corresponding to both conformers, syn and anti, in the radical cations is associated with a large barrier to rotation about the C(2)-C(2′) bond.
