Mustafa Güllü

Preparation of an EDOT-based polymer: optoelectronic properties and electrochromic device application

Here we present the synthesis, characterization and electropolymerization of a new EDOT-based monomer; 5,10-dihydrobenzo[f]thieno[3,4-b][1,4]dioxocine (DTD). Electrochemical polymerization of DTD was performed potentiostatically by using dichloromethane (DCM) as solvent and tetrabutylammonium hexafluorophosphate (TBPF6) as supporting electrolyte. Homopolymer [P(DTD)] films and copolymer [P(DTD-co-TPA)] films of DTD prepared by using 4-(2,5-di(thiophen-2-yl)-1H-pyrrole-1-yl)butane-1-amine (TPA) were characterized via CV and UV-vis spectroscopy. Spectroelectrochemical analysis of P(DTD) revealed electronic transitions at 585 nm (π–π* transition) with an electronic band gap of 1.69 eV. Electrochromic studies revealed that P(DTD) has competitive properties to EDOT. Furthermore, a dual-type complementary colored polymer electrochromic device based on P(DTD) and P(TPA) was constructed in sandwich configuration. Spectroelectrochemical studies revealed that the oxidized state of the device shows a blue color whereas it is yellow in the reduced state. The maximum contrast (Δ%T) and switching time of the device were measured as 25.5% and 0.5 s for 385 nm and 21% and 1.0 s for 550 nm.

Stereoselectivity and mechanism in the electrohydrodimerisation of esters of cinnamic acid

Rate constants (kobs) and reaction orders have been determined for the cathodic reduction in DMF solution of 11 cinnamic acid esters including some derived from chiral alcohols and a dicinnamate derived from trans-cyclohexane-1,2-diol. The cinnamic acid esters typically reduce with high stereoselectivity to all-trans 3,4-diphenylcyclopentanone-2-carboxylates. The enhancement of rates of reaction by addition of water was studied for selected substrates and low energies of activation were found. Changes in the alkoxy or aryloxy groups also caused significant changes in rate and log kobs correlated linearly with E° values. The results from kinetic experiments were complemented by product studies of reactions aimed at probing reversibility of key reaction steps. The combined evidence is interpreted as unambiguous support for radical anion–radical anion coupling as the key step with complexation with water, prior to coupling, being crucial.The relative stereochemistry at C-3 and C-4 is fixed, irreversibly, at the coupling stage and there is strong evidence to suggest that templating in the complex between two radical anions and water determines the stereochemical outcome.

Heterostructured poly(3,6-dithien-2-yl-9H-carbazol-9-yl acetic acid)/TiO2 nanoparticles composite redox-active materials as both anode and cathode for high-performance symmetric supercapacitor applications

Herein, a facile and simple method is reported for preparation of composite electrode materials based on conducting polymer/nano metal oxide combination for supercapacitor applications. The heterostructured composite redox-active electrode materials, having both p- and n-doping ability, were fabricated using poly(3,6-dithien-2-yl-9H-carbazol-9-yl acetic acid) and nano sized TiO2 particles without any binder and conducting additives. The heterostructured composite electrodes exhibited remarkable a specific capacitance (Cspec = 462.88 F g−1), specific power (SP = 266.96 kW kg−1), specific energy (SE = 89.98 W h kg−1), good cycling performance and excellent reversible capability (81.7% capacitance retention after 8000 charge/discharge cycles) at 2.5 mA cm−2 current density within a 1.2 V potential window with two-electrode symmetric cell configuration. Besides, heterostructured composite electrode materials were fabricated using different particle sized TiO2 (3–5 nm, average 21 nm and bulk), and the effect of the particle size on supercapacitor performances was investigated and compared in detail. Our symmetric pseudo-capacitor device lighted a LED for 4.7 min with 42 s charge time at 2.5 mA cm−2 even after 8000 charge/discharge cycles.

N-Substituted poly(3,6-dithienylcarbazole) derivatives: a new class of redox-active electrode materials for high-performance flexible solid-state pseudocapacitors

Herein, we present the design and synthesis of novel poly(3,6-dithienylcarbazole) derivatives, namely poly(tert-butyl 2-(3,6-di(thiophen-2-yl)-9H-carbazol-9-yl)acetate) (PTTBCbz) and poly(tert-butyl 2-(3,6-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9H-carbazol-9-yl)acetate) (PETBCbz), as redox-active materials for high performance electrochemical energy storage applications. Symmetric flexible solid-state pseudocapacitor devices were assembled by using PTTBCbz or PETBCbz and a polymer gel electrolyte based on LiClO4. The electrochemical characteristics of the pseudocapacitor devices were evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge measurements (GCD) and electrochemical impedance spectroscopy (EIS). The fabricated supercapacitor devices delivered superior specific capacitances (Cspec = 640 F g−1 and Cspec = 554 F g−1), energy densities (E = 1280 W h kg−1 and E = 1108 W h kg−1) and power densities (P = 36 kW kg−1 and P = 32.7 kW kg−1). Furthermore, these flexible supercapacitors exhibited good cycling stability and excellent capacitance retentions (92.5% and 90.5%) after 10000 successive charge/discharge cycles at a current density of 1 mA cm−2. The electrochemical characterization studies confirmed that these novel poly(3,6-dithienylcarbazole)-based redox-active materials have significant potential for utilization as redox-active electrode materials in high performance flexible and portable energy storage devices.

Cyclisation of 3-alkenylpyrido[1,2-a]pyrimidines to furo[2,3-d]pyrido[1,2-a]pyrimidines

3-Alkenylpyrido[1,2-a]pyrimidines react under mild conditions to give novel tricyclic furo[2,3-d]pyrido[1,2-a]pyrimidines in high yields. The cyclisation takes place in the presence of an acid catalyst. The product yield is affected by the type and the strength of the acid used. Exceptionally high yields were obtained when an organic acid like trifluoromethanesulfonic acid and trifluoroacetic acid were used. On the other hand, sulfuric acid gave the best results of the inorganic acids examined.

Novel poly(2,5-dithienylpyrrole) (PSNS) derivatives functionalized with azobenzene, coumarin and fluorescein chromophore units: spectroelectrochemical properties and electrochromic device applications

Three novel 2,5-dithienylpyrrole (SNS) derivatives containing strong chromophore units such as azobenzene, coumarin and fluorescein were synthesized to investigate the effects of chromophore substituents on the electrochemical and spectroelectrochemical properties of resulting polymers. Electrochemical and optoelectronic characteristics of the homopolymers, poly(1-(2-(4-(phenyldiazenyl)phenoxy)ethyl)-2,5-di(thiophen-2-yl)-1H-pyrrole) (PTPTAz), poly(4-(2-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)ethoxy)-2H-chromen-2-one) (PTPTCo) and poly(methyl 2-(6-(2-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)ethoxy)-3-oxo-3H-xanthen-9-yl)benzoate) (PTPTFlo), were investigated in detail. The combination of a strong chromophore pendant group with a poly(2,5-dithienylpyrrole) (PSNS) backbone significantly influences the electronic and optoelectronic behaviors of conducting polymers. PTPTAz and PTPTCo exhibited different colors in their neutral and oxidized states while PTPTFlo showed a yellow color in all states. The optical band gap (Eg) values of PTPTAz, PTPTCo and PTPTFlo films were calculated as 2.81 eV, 2.44 eV and 2.31 eV respectively. Moreover, a PTPTFlo/PEDOT based dual type solid state electrochromic device (ECD) was constructed. The ECD exhibited quite good long-term stability with reasonable optical memory performance under ambient conditions.

Electro-organic reactions part 35. Efficient carbon—oxygen bond formation in the anodic coupling of pyridopyrimidine derivatives.

Abstract 4-H-Pyrido[1,2-a]pyrimidine-2,4-diones (Chichibabin) derivatives, formed by condensation of 2-aminopyridines with substituted dialkylmalonates, are electroactive. In solution in CH2Cl2/CF3CO2H mixtures they are smoothly and selectively anodically coupled in high yield. The products are novel and unexpected; radical coupling at the C-3 and O-4 positions is involved and the proposed mechanism is analogous to that of oxidative phenolic coupling.

Electroorganic Reactions. Part 45. The Highly Stereoselective Electrochemical Hydrodimerisation of Methyl 4-tert-Butylcyclohex-1-enecarboxylate.

Abstract Methyl 4-tert-butylcyclohex-1-enecarboxylate undergoes 1 F reduction at a mercury cathode in DMF solution to give as the major single product a hydrodimer in which the cyclohexyl rings are joined axially and the methoxycarbonyl groups are also axial. The structure is confirmed by X-ray crystallography. Kinetic experiments, combined with force field calculations, indicate radicalanion/radical-anion coupling which is under stereoelectronic control and which dictates diaxial coupling of the cyclohexyl rings. Protonation of the resulting dimeric dianion is under thermodynamic control.

The effect of electrochemically formed aluminum salts on the electrochemical cyclisation of methyl cinnamate

Abstract Electrochemical cyclisation of methyl cinnamate with dielectrophiles has been improved by the presence of an aluminum salt which was pre-formed in situ by the electrolysis of a carboxylic acid with a sacrificial aluminum anode. High yields of three, five and six-membered cyclic products have been obtained in the reactions of methyl cinnamate with dichloromethane, 1,3-dibromopropane, and 1,4-dibromobutane.

Microwave-Assisted Synthesis of Furo[3,2-c]-1,8-naphthyridines

Abstract Microwave-assisted ring-conversion reactions of some pyrido[1,2-a]pyrimidine derivatives to 1,8-naphthyridines have been investigated. Novel furo[3,2-c]-1,8-naphthyridine compounds were synthesized in good yields under thermal reaction conditions. Both microwave and classical heating methods have been found to be satisfactory for the synthesis of new 1,8-naphthyridines.