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Conductive π-conjugated polymers were electrochemically generated from a variety of donor–acceptor pyrroles containing fused perimidine subunits. Alternating oxidative and reductive polarization of...

Thermally activated delayed fluorescence has been found in a group of tricarbazolylamines that are purely electron-donating, non-charge-transfer (CT) molecules. We show that the reverse intersystem crossing step in these materials is mediated through upper triplet states. Reverse internal conversion is shown to be the thermally activated mechanism behind the triplet harvesting mechanism. The strongly mixed n−π*/π–π* character of the lowest energy optical transitions retains high oscillator strength and gives rise to high ΦPL. Organic light-emitting diode devices using these materials were fabricated to show very narrow (full width at half-maximum = 38–41 nm) electroluminescence spectra, clearly demonstrating the excitonic nature of the excited states. This new combination of physicochemical properties of a non-CT molecule yields thermally activated delayed fluorescence, but via a different, physical mechanism, reverse internal conversion delayed fluorescence.

A high absorption coefficient and narrow absorption bands in squaraine (SQ) dyes have resulted in rapidly growing interest in them as a donor material in photovoltaic devices. The exciton dissociation process in organic systems proceeds via a multistep mechanism where the electron–hole pairs (charge transfer states) involved in the current generation process determine the recombination losses and subsequently limit the overall performance of organic solar cells. In this work, these basic electronic processes are investigated by magneto-photocurrent measurements (MPC, the photocurrent change induced by the external magnetic field) of SQ:PC60BM bulk-heterojunction solar cells with varying electron acceptor concentrations under magnetic fields up to 9 T and at different temperatures. Under a weak external magnetic field, the change in photocurrent is due to electron and hole (e–h) pairs that experience a modulating hyperfine interaction associated with nuclear (mainly proton) magnetic moment, while in strong magnetic fields the photocurrent is affected by the Δg mechanism with spin dephasing due to different Lande factors of the electron and hole entities (Δg ≈ 10−3). To consistently interpret the amplitudes and lineshapes of the MPC signals at various temperatures, charge carrier hopping in a disordered environment competing with the magnetic dipole spin precession is proposed. The requirements for efficient small-molecular weight organic:fullerene bulk-heterojunction solar cells are briefly discussed.

The work describes the in-situ Raman spectroelectrochemical studies on thionine layer covalently bound to the gold surface (Th/Au). The thionine layer was deposited on Au substrate via electrochemical reduction of corresponding diazonium salt. Due to the presence of system of conjugated bonds in the film’s structure, grafted thionine reveals electrochemical response analogical to unbound thionine. It is shown that bound Th can undergo irreversible oxidation leading to the formation of surface-bound radical cation and thus thionine dimers, as supported by cyclic voltammetry and Raman spectroelectrochemistry studies.

Triphenylamine-based hydrazones were subjected to electropolymerization process that gave well conductive hydrazone based polymers. The first example of polyhydrazone formation during the electrochemical process was shown. The estimation of polymer structure was demonstrated using IR spectroelectrochemistry. The EPR spectroelectrochemistry allowed to explain why in some cases dimer couldn’t be formed. The results of electrochemical, spectroelectrochemical investigation of small molecules, as well as their polymers obtained by electropolymerization, are presented. The comparative study of electropolymerization and doping process by IR, EPR, potentiostatic and potentiodynamic UV-Vis-NIR, DEIS spectroelectrochemical techniques was performed to determine the reaction path, charge carriers and conductivity of polymeric layers.

First report of π-conjugated push-pull copolymer systems with 4,4′-bipyridine moieties in the main macromolecular chain is presented. C-substitution pattern of electropolymerisable bithiophene pendants at the 4,4′-bipyridine unit offered the versatility to retain the latter as free amine, or convert it into bipyridylium salt. Both structures have been prepared and investigated, delivering the first example of a polymer with viologen unit making up the extended π-bond. Detailed electrochemical, spectroelectrochemical and quantum chemical study of these new polymer systems and their 2,2′-bipyridine analogues has shown that while linear structure and extended conjugation in the latter help it to accommodate charge carriers characteristic for heavily doped polythiophene, the conjugation break afforded by the meta substitution pattern across the 4,4′-pirydyl unit makes the polymer behave like an ensemble of shorter oligomeric segments with better defined electron transitions and sharper, and faster electrochromic response. Effective π-π interchain coupling between α,ω-bis(2-pyridyl)quaterthiophene repeating units was observed, whereas intramolecular interactions were found to dominate in the linear 2,2′-bipyridyl based polymer. While the bithiophene derivative of methyl viologen electropolymerised less easily than its corresponding non-quaternised derivative, the resulting polymer films demonstrated decent stability when subject to subsequent p- and n-doping, featuring pronounced charge trapping/detrapping signatures. Furthermore, ion pairing between the viologen and weakly basic PF 6 − and CF 3 SO 3 − counterions has been found to impact the redox chemistry of bithiophene functionalised viologen structure. Experimental findings have been confronted with results of quantum chemical computations helping to elucidate the electrochemical and spectroelectrochemical observations made. Presented study delivers insights into the doping processes taking place in conjugation disrupted 4,4'-bipyridine core copolymers, helping to evaluate their potential as substrates for new tuneable π-conjugated polymeric systems.

A new class of carbazole derivatives, with varying degree of core substitution was synthesized and characterized. The presented synthetic route requires mild conditions, starts from low-cost substrates and leads to the formation of the target products with good yields. The optical and electronic properties of the synthesized materials were estimated and supported by DFT calculations. Investigated compounds emit violet light with quantum efficiency reaching 18.2%. Electrochemical and electron photoemission spectroscopy revealed that ionization potentials are in range of 5.10–5.30 eV. Time-of-flight measurements revealed that those compounds have balanced hole and electron mobility in range of 4.27·10−6–8.42·10‐5 cm2/Vs for star-shaped compound and 6.2 × 10−7–6.2 × 10−6 cm2/Vs for linear derivatives. Electroluminescence spectra of the OLED device prepared using the newly synthesized compounds were characterized by broad emission in visible range, resulting in white light generation.

A structure-property study across a series of donor-acceptor-donor structures composed of mono- and bi-(1,3,4-oxadiazole) units symmetrically substituted with alkyl functionalized bi-, ter- and quaterthiophene segments is presented. Synthetically tailoring the ratio of electron-withdrawing 1,3,4-oxadiazole to electron-releasing thiophene units and their alkyl grafting pattern permitted us to scrutinize the impact of these structural factors on the redox, absorptive and emissive properties of these push-pull molecules. Contrasting trends of redox potentials were observed, with the oxidation potential closely following the donor-to-acceptor ratio, whereas the reduction potential being tuned independently by either the number of acceptor units or the conjugation length of the donor-acceptor system. Increasing the thiophene unit contribution delivered a shift from blue to green luminescence, while the structural rigidity afforded by intramolecular non-covalent interactions between 1,3,4-oxadiazole and the thiophene moieties has been identified as the prime factor determining the emission efficiency of these molecules. All six structures investigated electro-polymerize easily, yielding electroactive and electrochromic polymers. The polymer doping process is largely influenced by the length of the oligothiophene repeating unit and the alkyl chain grafting density. Polymers with relatively short oligothiophene segments are able to support polarons and polaron-pairs, whereas those with segments longer than six thiophene units could also stabilize diamagnetic charge carries - bipolarons. Increasing the alkyl chain grafting density improved the reversibility and broadened the working potential window of the p-doping process. Stable radical anions have also been investigated, bringing detailed information about the conjugation pattern of these electron-surplus species. This study delivers interesting clues towards the conscious structural design of bespoke frontier energy level oligothiophene functional materials and their polymers by incorporating a structurally matching 1,3,4-oxadiazole unit.

1,3,4-Thiadiazole, 2,2'-bi(1,3,4-thiadiazole), 2,2':5',2″-ter(1,3,4-thiadiazole), and 2,2':5',2″:5″,2‴-quater(1,3,4-thiadiazole) symmetrically disubstituted with 3-alkyl-(2,2'-bithiophen)-5-yl were synthesized by new procedures using readily available ethyl 3-alkyl-(2,2'-bithiophene)-5-carboxylate as a convenient substrate. These new compounds with a fixed number of donor rings and increasing number of acceptor rings showed very interesting, tunable redox properties. In particular, they exhibited electron affinities (EAs) ranging from -3.06 to -3.83 eV, reaching EA values desired for air-operating n-type organic semiconductors. Their electrochemically determined ionization potentials were only moderately dependent on the number of thiadiazole rings, varying from 5.83 to 6.01 eV. Emission spectra of these compounds could also be tuned in a wide range (from 470 to 600 nm). Spectroscopic and electrochemical data were confirmed by density functional theory calculations demonstrating full consistency.

A mixture of three constitutional isomers containing terminal reactive phthaloperinone units was obtained by the condensation of 4,4′-(4,4′-isopropylidenediphenoxy)bis(phthalic anhydride) with 1,8-naphthalenediamine. Both terminal units underwent an addition reaction via electrochemical oxidation and subsequent reduction at the perimidine core and isoindolinone, respectively, to create a multi-directional crosslinked product. The course of electropolymerization depended significantly on the isomer used, which was related to the intermediate products formed during electrooxidation: π-dimers formed in the precursor solution with stronger π-π interactions between radical cations and/or products containing π-conjugated segments: bis-isoindolinone, bis-perimidine (bonded via 3/4 and 3′/4′ positions) and protonated σ-bonded bis-perimidine via 1/6 and 1′/3′/4′/6′ positions, where hydrogen bonds stabilized these latter adducts and prevented their deprotonation. The polymers were characterized by a mixed structure, which had different effects on the long-range interactions, stability of hydrogen bonds providing a redox center located on the protonated dicationic bis-perimidine segment underwent reversible reduction to stable radical cation.

We report on electrochemical and spectroelectrochemical (UV-Vis, EPR) investigations of donor-acceptor-donor triphenylamine- s -tetrazine derivatives with different linkers between donor and acceptor part of molecules. The influence of the chemical nature of the linker on properties of studied compounds was observed and analyzed. Tuning of the conjugation level between donor and acceptor part of molecules results in different activity in the electrochemical polymerization (oligomerization) process. The investigations of the polymerized layers have revealed interesting features. Thin polymeric films exhibit charge trapping phenomena, together with a storage properties. In order to conduct more precise analysis, the DFT/TDDFT calculations were carried out which provided comprehensive characteristics of investigated molecules.

Six 3,6-disubstituted-s-tetrazine, symmetrical and unsymmetrical, derivatives have been characterized electrochemically and spectroelectrochemically. Our studies started from 3,6-dichloro-s-tetrazine and afterwards the effect of halogen replacement with the ethoxy and phenoxy group was examined. Then, the influence of heterocyclic substituents was investigated. Finally, the reduction process of compound with two s-tetrazine ring in its structure was analyzed. The systematic EPR investigations of electronic structure of studied anion-radicals are presented. Those studies have revealed an unusual behavior of a compound featuring two connected s-tetrazine rings in its structure. Reduction of this compound proceeds as a two-step process which leads to formation of two radicals with different g-factors: one of them localizes on one s-terazine ring as a result of the first step and the second radical localizes on another ring in the second step of reduction.

EPR and UV–vis spectroelectrochemical behavior of a series of ambipolar donor–acceptor–donor (DAD) compounds, consisting of a diketopyrrolopyrrole (DPP) central unit symmetrically disubstituted with mono-, bi- and terthiophene, is reported. All derivatives studied undergo a reversible reduction to radical anions at E ca. −1.55 V to ca. −1.65 V vs Fc/Fc+. Electrochemically generated radical anions are sufficiently stable to be detected at RT. Two-step oxidation of these compounds involves the formation of radical cations in the first step followed by their transformation into spinless dications in the second one. The formed radical cations are detectable at RT, however, contrary to the case of radical anions they yield unresolved EPR spectra. The potential of their formation depends on the length of D segment decreasing from ca. 0.50 V vs Fc/Fc+ for monothiophene disubstituted DPP to ca. 0.25 V in the case of the terthiophene derivative. Combining differential pulse voltammetry with EPR and UV–vis spectroelectrochemistry allows for unequivocal identification of all new, electrochemically induced UV–vis bands to particular forms of the studied molecules (radical anions, radical cations or dications). Both electrochemical reduction and electrochemical oxidation processes involve profound and distinctly different spectral changes in the visible range of the spectrum. Since they are reversible, the studied compounds can be considered as promising multicolor electrochromophores.

The purpose of this study was to investigate 3,4-diarylpyrrole electropolymerization and simultaneous or subsequent intramolecular oxidative coupling leading to poly(phenanthropyrrole). Small amounts of π-conjugated products were obtained only under the conditions of increased concentration of the monomer and increased rate of potential sweep, which enabled both processes − monomer oxidation and deprotonation of the σ-dimer. The combined electrochemistry, UV-vis-NIR, ESR and TD-DFT results show, that the α,α'-coupling of 3,4-diarylpyrrole derivatives is inhibited by the stability of the σ-dimer dication, inhibition of the deprotonation and the reversal of the σ bond formation resulting in regeneration of the monomer. The addition of pyridine did not result in σ–dimer deprotonation in 2- and 2'-position.

In this work the electrochemical and spectroelectrochemical characterization of a s-tetrazine-triphenylamine derivative with a donor–acceptor–donor-type structure is reported, which in addition undergoes electrochemical polymerization. The investigations of the polymerized layers have revealed unusual characteristics. Thin polymeric film exhibits charge-trapping properties with great storage and memory effect. Moreover, the polymer displays reversible switching of fluorescence in oxidation mode and emission of light during reduction.

The derivatives of 2,4,6-triphenyl-1,3,5-triazine containing fluorene, carbazole and phenothiazine moieties were investigated electrochemically. The comparative study of electrochemical and optical properties of the compounds was performed with the attempt to establish a correlation between their properties and π-electron conjugation lengths. Basic electronic parameters were estimated and electrochromic windows from three polymeric derivatives were formed. Electrochromic parameters, optical density (ΔOD) and coloration efficiency (CE) were determined.

Organic electronics, mainly due to advancements in OLED (organic light-emitting diode) technology, is a fast developing research area having already revolutionized the displays market. This direction presents the use of exciplex emitters and thermally activated delayed fluorescence (TADF) in OLEDs, to give efficient, stable emitters that do not use scarce and expensive materials such as iridium. Here, it is shown for the first time several diketopyrrolopyrrole (DPP) derivatives that could be used as emitters in OLED devices. We were able to improve the efficiency of DPP materials by forming exciplex-enhanced OLED devices. These organic materials were also characterized by electrochemical and spectroscopic methods in order to elucidate each molecule's interaction and decrease the photoluminescence efficiency.

We present the synthesis of amidine derivatives and the separation of their isomers obtained after the reaction of different bis(phthalic anhydrides) with 1,8-diaminenaphtalene (1,8DAN). The isolated isomers of 4′-(4,4′-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA) significantly differed in their optical and electrochemical properties, showing distinct changes in reactivity due to electrooxidation. The calculated HOMO energy and visualization of this orbital indicated its localization on the perimidine unit. Thus, the condensation of BPADA with 2,3-diaminonaphthalene was also performed to obtain the naphtho[2,3-d]imidazole units as terminal groups to compare its oxidative reactivity versus the perimidine segment. It was confirmed that only the perimidine-containing compounds were reactive due to electrochemical oxidation; however, in a solution containing a mixture of isomers, we only obtained soluble products. In turn, the isolation of isomers and electrooxidation in a solution containing only one type of isomer resulted in the production of a solid and redox-active product.

Series of compounds consisting of carbazole arms and 1,3,5-triazine core linked by amino group were synthesized and characterized. The clear relationship between electrochemical properties, quantum efficiency, charge transport properties and structure were estimated. The exciplex-forming properties of the synthesized compound as donor, and two known exciplex-forming acceptors 4,7-diphenyl-1,10-phenanthroline (Bphen) and 2,2′,2"-(1,3,5-benzenetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) where predicted and investigated. It was shown that the star-shaped configuration of the compound 3CzNCprovides the best exciplex OLED performance with EQE up to 6.84%.

The formation of a poly(2,6-carbazole) derivative during an electrochemical polymerization process is shown. Comparison of 3,5-bis(9-octyl-9H-carbazol-2-yl)pyridine and 3,5-bis(9-octyl-9H-carbazol-3-yl)pyridine by electrochemical and UV-Vis-NIR spectroelectrochemical measurements and DFT (density functional theory) calculation prove the formation of a poly(2,6-carbazole) derivative. Both of the compounds form stable and electroactive conjugated polymers.

Here we report the characterization of diquinoline derivatives with ambipolar character. The investigated derivatives show low p- and moderately low n-doping redox systems. The derivatives were investigated and the electrochemical and optical properties of these compounds measured, with attempts to correlate the properties with their π-electron conjugation lengths. We showed the marked influence of the heteroatom in the bridge (central ring) and geometry of the molecule with its electronic properties. The compounds were compared by UV–vis–NIR and electron paramagnetic resonance (EPR) spectroelectrochemistry indicating very different charge and spin properties dependent on the heteroatoms present. Finally the organic light-emitting diode (OLED) devices were formed and characterized.

Arylene diimide derivatives with imine linkages, that is, azomethinenaphthaldiimides end-capped with pyridine, thiophene, bithiophene, and (ethylenedioxy)-thiophene units and corresponding polymers with thiophene and bithiophene structure as charge-transport compounds were investigated. All compounds along with polymers form alternated electron-accepting (A)–electron-donating (D) systems, except of one contains the pyridine structure, which constitutes an A–D–A–D–A molecule. The effect of end-capping structure group on the spectroelectrochemical properties was studied. All compounds were electrochemically active and undergo reversible reduction and irreversible oxidation. They exhibited a low electrochemically (CV) calculated energy band gap (Eg), ranging from 1.09 to 1.78 eV. The lowest one was found for compound with (ethylenedioxy)-thiophene structure. Moreover, the attempt of electrochemical polymerization of azomethinenaphthaldiimides was undertaken. The changes in UV–Vis spectra recorded during electrochemical oxidation and reduction were observed. Results indicate the lack of interaction between imide groups and end-capping groups. In order to analyze the structure of charged forms created during electrochemical reduction, the EPR spectroelectrochemical measurements were performed.

A series of star-shaped carbazole derivatives were prepared via Suzuki-Miyaura and Stille coupling procedures. Received monomers were characterized by UV-Vis spectroscopy, fluorescence spectroscopy and cyclic voltammetry in order to estimate their basic spectral, electrochemical and electronic properties important for wide scale of applications in organic electronics and photovoltaics. Experimental results were supported by DFT calculations. Synthesised compounds were also used as monomers in the electrodeposition of conjugated polymers. Spectroelectrochemical EPR and UV-Vis-NIR measurements were carried out in order to study the influence of structure on charge carrier formation.

Four arylene bisimides N-substituted with triarylamine and three bisimides core-functionalized with the same substituent were studied by cyclic voltammetry, UV-vis and EPR spectroelectrochemistry. All the investigated compounds showed ambipolar behaviour manifested by their quasi-reversible reduction to radical anions and quasi-reversible oxidation to radical cations. The presence of stable radical anions and radical cations was confirmed by EPR spectroelectrochemical experiments. Formation of the radical anions resulted in bleaching of the bisimide UV-vis bands with simultaneous hypsochromic shift of the charge transfer (CT) band and appearance of the radical anion peaks, the bands originating from the triarylamine remaining essentially unchanged. Electrochemical generation of radical cations resulted in turn in bleaching of the triarylamine band accompanied by a hypsochromic shift of the CT band and with the appearance of the radical cation bands at higher wavelengths, the bisimide bands remained essentially intact.

In this work we present electropolymerization of monomers of an unusual type using N -linked carbazole units to limit their conjugation. The polymers thus obtained have limited conjugation through the backbone. Using donor-acceptor-donor (D-A-D) and donor-donor-donor (D-D-D) monomers we evaluate the effects of the presence (or absence) of charge transfer states on synthesized electropolymers. The use of a D-A-D monomer resulted in obtaining an ambipolar polymer with quasi -reversible reduction.

The 2,7- and 3,6-substituted carbazole and triphenylamine chalcogenophene (Se, Te) derivatives and their electrodeposited polymers are investigated using electrochemical and UV–vis–NIR/ESR spectroelectrochemical methods. Major differences in the case of oxidation and electropolymerization behavior between monomers and related polymers are shown. Se and Te atoms do not conjugate their lone electron pairs with the π-conjugated system and therefore only increase the contribution of the quinoid form of the chalcogenophene unit. The 2,7- substituted carbazole derivatives present stronger carbazole–chalcogenophene conjugation than 3,6-substituted derivatives. One 3,6-substituted carbazole derivative and triphenylamine derived polymers were found to have promising electrochromic properties with black electrochromism.

Electrochemical and spectroelectrochemical properties of a series of new penta-ring donor–acceptor compounds, comprising 1,3,4-oxadiazole, 1,3,4-thiadiazole, and 1,2,4-triazole central ring, symmetrically connected to substituted bithiophenes, were investigated. Aromaticity and electrophilic–nucleophilic traits of the aza-heterocyclic units, fostering inductive and resonance effects that translate to conjugation enhancement and electron (de)localization, were found a major factor determining the key electron properties of ionization potential (IP) and electron affinity (EA) of these molecules. Replacing the alkyl thiophene substituent for an alkoxy one afforded certain control over the two parameters as well. All studied compounds were found to undergo electrochemical polymerization giving p- and n-dopable products, featuring good electrochemical reversibility of their oxidative doping process, as demonstrated by cyclic voltammetry and UV–vis–NIR, EPR spectroelectrochemistry. While electropolymerization o...

Mono- and disubstituted EHBG (HBED) ligands of different kind: forming hydrogen bonds ( p -OMe, p -NHAc) and of high lipophilicity (3,4-Me 2 , p -Ph) were obtained. The ligands were complexed with Fe(III). Complexes so obtained were studied for their stability in different pH environments; and r 1 relaxivity, which turned out the highest for Fe-EHBG-NHAc, i.e. 0.95 mM −1 s −1 in aqueous solution and 1.34 mM −1 s −1 for Fe-EHBG-Me 2 in bovine serum. EPR signals were observed at g -factor of 4.27 indicative of Kramer's doublet transitions of a rhombically distorted high-spin paramagnetic center.

Here we report the preparation of 3,6- bis(bithenyl)-N-decylcarbazole with low oxidation potential due to extended conjugation that underwent facile electrochemical polymerization to form stable electroactive polymer. We extended the conjugation of the monomers in comparison to the carbazole and large decrease were observed in the oxidation potential at which polymerization occurs. To lower the oxidation potential of the monomer and control the optical and electronic properties of the polycarbazole, we attached the thiophene, bithiophene and 3,4-ethylenedioxythiophene (EDOT) at both the 3 and 6 positions of N-substituted carbazole. The monomers and their polymers were compared through electron paramagnetic resonance (EPR) and UV-Vis-NIR spectroelectrochemistry resulting in interesting properties. As optically active materials the CIE L*a*b chromaticity and other optical properties were observed.

Polymer films of poly(3,4-ethylenedithiothiophene) obtained by electrochemical oxidative polymerisation of the corresponding monomer have been investigated. p-Doping process of the polymer was characterized by in situ EPR spectroelectrochemisty. Compared to its close relative – PEDOT, the polymer features two distinct voltammetric peaks. The results of our studies indicate that both represent faradaic processes and that each manifests generation of charge carriers in the polymer.

Triazine derived organic materials possessing various donor-chromophores at the periphery have been designed, synthesized and characterized. The synthesized compounds formed molecular glasses. Their glass transition temperatures ranged from 148 to 235 °C. The compounds demonstrated high thermal stability. The onset temperatures of their thermal decomposition exceeded 390 °C. The fluorenyl- and carbazolyl-substituted triazine derivatives were shown to be highly fluorescent in solutions and rigid polymer matrices with fluorescence quantum yields being in the range of 0.73–0.82. The phenothiazinyl-substituted triazine derivative showed moderate fluorescence quantum yields in dilute solution ( η = 0.25) or polymer matrix ( η = 0.50). Photophysical studies of phenothiazinyl-substituted triazine derivative in media of different rigidity and polarity revealed its twisted intramolecular charge transfer character. Neat films of the triazine compounds displayed significant fluorescence quenching accompanied by a non-exponential excited-state decay profile which was attributed to migration-assisted exciton quenching at non-radiative decay sites in disordered media. Differential pulse voltammetry studies of the synthesized materials showed that the nature of donor-substituents attached to the triazine core can influence their redox behaviour. Investigation by cyclic voltammetry revealed that the synthesized materials can be used as monomers to prepare high dimensional conjugated polymers by electro-oxidation. Spectroelectrochemical investigation of electro-oxidation products suggested the formation of charged species like polarons or bipolarons.

Two low molecular weight electroactive donor-acceptor-donor (DAD)-type molecules are reported, namely naphthalene bisimide (NBI) symmetrically core-functionalized with dithienopyrrole (NBI-(DTP)2 ) and an asymmetric core-functionalized naphthalene bisimide with dithienopyrrole (DTP) substituent on one side and 2-ethylhexylamine on the other side (NBI-DTP-NHEtHex). Both compounds are characterized by low optical bandgaps (1.52 and 1.65 eV, respectively). NBI-(DTP)2 undergoes oxidative electropolymerization giving the electroactive polymer of ambipolar character. Its two-step reversible reduction and oxidation is corroborated by complementary EPR and UV/Vis-NIR spectroelectrochemical investigations. The polymer turned out to be electrochemically active not only in aprotic solvents but also in aqueous electrolytes, showing a distinct photocathodic current attributed to proton reduction. Additionally, poly(NBI-(DTP)2 ) was successfully tested as a photodiode material.

A series of hybrid tetrathiafulvalene-oligothiophene compounds has been synthesised, where the tetrathiafulvalene unit is fused at each side to an end-capped oligothiophene chain of varying length (terthiophene, quinquithiophene and septithiophene). Each hybrid structure (1-3) has been studied by cyclic voltammetry and triple EPR-UV-Vis-NIR spectroelectrochemistry in the case of the quinquithiophene compound (2). Comparison is made with the corresponding half-units, which lack the fulvalene core and contain just one oligothiophene chain. The highest hole mobility of quinquithiophene-TTF 2 was obtained from field effect transistors (8.61 × 10-3 cm 2 V-1 s-1); its surface morphology was characterised by tapping mode atomic force microscopy and a power conversion of 2.5% was achieved from a bulk heterojunction organic solar cell device using PC71BM as the acceptor.

In an effort to extend the conjugation system of boron-dipyrrin (BODIPY), the dye was coupled with polymerisable units of carbazole, alkylthiophene, and 3,4-ethylenedioxythiophene (EDOT). Due to electron donating character of the units connected to the strong electron accepting segment of tri-coordinated boron, the optical and electrochemical properties of the dye changed, and followed the strength of the electron donating substituent. All studied compounds exhibited electroactivity in both anodic and cathodic potential ranges, however, electropolymerisation was only observed for BODIPY modified with EDOT, leading to trimeric and tetrameric substituents. Potential controlled optical changes (spectroelectrochemistry) and in situ spin density distribution measurements, supported by quantum chemical calculations using density functional theory, were undertaken in order to understand the reversibility of the electrochemical processes. Hyperfine split ESR spectra of the radical anion species were successfully modelled revealing intriguing, hyperconjugation type unpaired spin delocalisation patterns.