- Role of Substituents at 3-position of Thienylethynyl Spacer on Electronic Properties in Diruthenium(II) Organometallic Wire-like Complexes
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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.
- Roy, Sourav Saha,Chowdhury, Sabyasachi Roy,Mishra, Sabyashachi,Patra, Sanjib K.
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- Catalytic transformations of alkylthiophenes
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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
- Mashkina,Chernov
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p. 209 - 215
(2007/10/03)
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- STUDIES TOWARD ALKYLTHIOPHENE-2-CARBOXALDEHYDES. REDUCTION OF 3-ALKENYLTHIOPHENES WITH TRIETHYLSILANE/TRIFLUOROACETIC ACID. REGIOSELECTIVTY IN FORMYLATION REACTIONS OF ALKYLTHIOPHENES
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Reduction of 2- or 3-alkenylthiophenes with Et3SiH/CF3CO2H in CH2Cl2 gives the corresponding 2- or 3-alkylthiophene in >90percent isolated yield.The regioselectivity of various Vilsmeier formylations of 3-alkylthiophenes was found to be a function of increasing steric bulk in the 3-alkyl substituent and in the Vilsmeier reagent.The regioselectivty of formylations of 3-alkylthiophenes by initial lithiation with butyllithium in ether followed quenching with DMF is independent of the presence or absence of TMEDA.
- Detty, Michael R.,Hays, David S.
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p. 925 - 938
(2007/10/02)
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- A CONVENIENT SYNTHESIS OF 3-ALKYLTHIOPHENES
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The known procedures for the synthesis of 3-alkylthiophenes are rather lengthy or involved.By using the NiDPPP++ catalyzed cross-coupling method between 3-bromothiophene and Grignard reagents derived from alkyl halides a number of 3-alkylthiophenes have been prepared in a one-step reaction in good to excellent yields.
- Pham, Chiem Van,Mark, Harry B.,Zimmer, Hans
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p. 689 - 696
(2007/10/02)
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