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A series of molecules with a dicyanovinyl acceptor connected with various substituted phenyls as donor blocks were synthesized and characterized. The thermal, electrochemical and photophysical properties of these compounds were investigated and compared. DSC and TGA measurements revealed that all compounds showed high both different melting transitions and the beginning of decomposition. The electrochemical studies did not show significant differences in energy band gap being between 2.41 and 2.55 eV (except for one with carbazole unit), which was also supported by the density functional theory calculations. They emitted light with higher photoluminescence quantum yield in film than in solution. Blends containing the malononitrile derivatives dispersed in a solid matrix consisting of poly(9-vinylcarbazole) and (2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole) emitted with small or high contribution from the host, signaling efficient or incomplete energy transfer from host to guest molecules. Emission of light under external voltage by diodes based on these blends was observed.

Two cyclometalated alkynylgold(III) complexes [AuCl(tpy)(C≡C–C6H4CH3)] (1) and [AuCl(ppy)(C≡C–C6H4CH3)] (2), where ppy = 2-phenylpyridine and tpy = 2-(p-tolyl)-pyridine, were successfully synthetized. Their photophysical properties were investigated by absorption and photoluminescence spectroscopy in solution, solid state, and glass matrix (77 K). Differences in solid state luminescent behaviour of the reported Au(III) complexes were correlated with packing of [AuCl(tpy)(C≡C–C6H4CH3)] and [AuCl(ppy)(C≡C–C6H4CH3)] molecules and weak interactions in the network lattices of 1 and 2. Additionally, photoluminescence spectra of [AuCl(tpy)(C≡C–C6H4CH3)] in film and dispersed in solid matrix consisting of poly(9-vinylcarbazole) and (2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole) were registered. The preliminary tests of electroluminescence ability of complex 1 were carried out.

A series of solution-processable tetrasubstituted naphthalene derivatives bearing thiophene or carbazole units were synthesized using the tandem cycloaddition [2+1+2+1] and Diels–Alder reaction[4+2]. Thermal, electrochemical, absorption, and emission properties of synthesized compounds were studied. They can be considered as molecular glasses with glass transition temperature ranging from 37 to 122 °C with high thermal stability up to 300 or 400 °C. The naphthalene derivatives were electrochemically active and showed low energy band gap between 1.64 and 1.85 eV. All derivatives were luminescent and emitted light with maximum emission band located at 379–436 nm with photoluminescence quantum yield in the range of 9.5–19.8% in solution. They photo- and electroluminescence ability in solid state as thin film and blends with poly(9-vinylcarbazole) (PVK) and mixture PVK with (2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole) (PBD) were tested. Together with increase of compound content from 2 to 15 wt% in binary matrix, the increase of electroluminescence intensity was observed. Diodes with guest-host configuration showed electroluminescence with maximum of emission band from 593 to 637 nm. The most intense emission of light under applied voltage characterized devices based on compound bearing carbazole derivatives and one methyl group.

Solid-state emissive organic materials are perspective for applications in organic electronics. Here, the 2,2-dicyanovinyl derivatives bearing thiophene, furan, phenyl, N-methylpyrrole, naphthalene, benzothiophene and benzofuran structures were successfully prepared by the Knoevenagel condensation of propane-1,3-dinitrile with various ketones. The synthesized compounds were crystalline solid with melting temperature between 87 and 161 °C and temperature of 5% weight loss in the range of 140–190 °C based on differential scanning calorimetry and thermogravimetric measurements, respectively. The density functional theory showed that LUMO orbitals are localized more at 2,2-dicyanovinyl moiety whereas in the case of HOMOs slightly higher contribution from the aromatic parts can be observed. The results of cyclic voltammetry showed that both reduction and oxidation process values differ greatly depending on donor properties. Calculated the ionization potentials and electron affinities were in the range of −5.52 – −6.48 eV and −3.3 − −3.64 eV, respectively, which results in energy band gap mainly below 3.0 eV. The 2,2-dicyanovinyl derivatives were emissive both in solution and in the solid, in which higher quantum photoluminescence yield was detected. When 2,2-dicyanovinyl derivatives molecularly dispersed in a solid matrix poly(9-vinylcarbazole) (PVK) and a binary matrix consisting of PVK (60 wt. %) and 2- text-butylphenyl-5-biphenyl-1,3,4-oxadiazole) (PBD) (40 wt. %) (guest-host configuration), they show green or yellow or red electroluminescence.

Six novel azomethines with substituted thiophene central core were synthesized and their properties are reported. They were obtained by the condensation reaction between 2,5-diamino-thiophene-3,4-dicarboxylic acid diethyl ester and various aldehydes. The imines were characterized by NMR and FTIR spectroscopies and by elemental analysis. DSC measurements revealed that the prepared compounds are molecular glasses (except for one) with high T g varying from 94 and 183 °C. Their redox properties were investigated in solution by cyclic voltammetry and differential pulse voltammetry. It was found that all imines were electrochemically active and showed low values of energy band gap ranging from 1.61 to 1.78 eV. Photoluminescence measurements indicated that they emitted light in solution with quantum yield (Φ PL ) in the range of 1.2–14.3% and in solid state as film and blend with poly(methyl methacrylate) and binary blend with poly(9-vinylcarbazole) (PVK) and (2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole) (PDB) with Φ PL form 0.24–1.77% and from 0.52% to 1.66%, respectively. The density functional theory (DFT) was applied for calculating their geometries and frontier molecular orbitals. Their electroluminescence ability was examined in guest-host diode with structure ITO/PEDOT:PSS/PVK:PBD:imine / Al and emission of light with maximum of emission band from 626 to 674 nm was observed. This work demonstrates, to the best of our knowledge, the first example of light emitting devices based on thiophene azomethines as active layer component.

Novel derivatives of 4'-phenyl-2,2':6′,2″-terpyridine (tpy) with ethynyl ( T1 ), 2-ethynyl-9,9-dioctylfluorene ( T2 ), 9,9-dioctylfluorene ( T3 ), 9-ethynyl-10-decyloxyanthracene ( T4 ) substituents were obtained via Sonogashira or Suzuki-Miyaura coupling reactions, respectively, and thoroughly characterized. The presence of ethynyl bridge impacts photophysical properties of novel compounds by shifting absorption and emission spectra towards longer wavelengths as compared to T3 , where fluorene is connected with tpy via a single bond. TGA measurements showed that among the new terpyridines those obtained as solids exhibited high thermal stability as opposed to those which were oils (tpy containing fluorene motif). Due to the fact that high thermal stability of 4'-phenyl-2,2':6′,2″-terpyridine derivatives showed photoluminescence (PL) quantum yield (Φ) in the range of 27–84% in solution, their electroluminescence ability was tested in diodes with guest-host configuration. For the compounds dispersed in a matrix consisting of poly(9-vinylcarbazole) (PVK) (50 wt %) and (2- tert -butylphenyl-5-biphenyl-1,3,4-oxadiazole) (PBD) (50 wt %) radiation with maxima between 374 and 531 nm and characterized with Φ in the range of 8–12% was observed. They exhibited green or violet electroluminescence. The results confirmed the substantial role of aryl groups and the linker in the presented terpyridines in terms of their thermal, electrochemical, optical and electroluminescence properties. In addition, density functional theory (DFT) and time-dependent-density functional theory (TD-DFT) calculations were performed to provide an independent support and deeper insight into the experimental results.

Five novel derivatives of pyrene, substituted at positions 1,3,6,8 with 4-(2,2-dimethylpropyloxy)pyridine (P1), 4-decyloxypyridine (P2), 4-pentylpyridine (P3), 1-decyl-1,2,3-triazole (P4), and 1-benzyl-1,2,3-triazole (P5), are obtained through a Suzuki-Miyaura cross-coupling reaction or CuI -catalyzed 1,3-dipolar cycloaddition reaction, respectively, and characterized thoroughly. TGA measurements reveal the high thermal stability of the compounds. Pyrene derivatives P1-P5 all show photoluminescence (PL) quantum yields (Φ) of approximately 75 % in solution. Solid-state photo- and electroluminescence characteristics of selected compounds as organic light-emitting diodes are tested. In the guest-host configuration, two matrixes, that is, poly(N-vinylcarbazole) (PVK) and a binary matrix consisting of PVK and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD) (50:50 wt %), are applied. The diodes show red, green, or blue electroluminescence, depending on both the compound chemical structure and the actual device architecture. In addition, theoretical studies (DFT and TD-DFT) provide a deeper understanding of the experimental results.

Three solution-processable small organic molecules bearing quinoline as electron-accepting moiety were synthesized via condensation reaction of novel 6-amino-2-(2,2’-bithiophen-5-yl)-4-phenylquinoline with 2,2’-bithiophene-5-carboxaldehyde, 9-ethyl-9H-carbazole-3-carbaldehyde and 9-phenanthrenecarboxaldehyde. The presence of alternating electron-donating and accepting units results in a donor-acceptor-donor architecture of these molecular systems. Thermal, photophysical, and electrochemical properties of these small molecules were examined and the experimental results were supported by the density functional theory calculations. The obtained molecular systems exhibited high thermal stability with decomposition temperatures (5% weight loss) exceeding 330 °C in nitrogen atmosphere. It was found, based on DSC measurements, that investigated Schiff bases form amorphous material with glass transition temperatures between 88 and 190 °C. They also showed a UV–vis absorption in the range of 250–500 nm both in solution and in solid state as film and blend with PMMA and PVK. Photoluminescence measurements revealed moderately strong blue-light emission of the imines in solution as well as in PMMA blend with quantum yields in the range of 2–26%. In the case of imines dispersed in PVK matrix the emission of green light was mainly observed. In addition, when mixed with plasmonically active silver nanowires, the compounds exhibit relatively strong electroluminescence signal, associated with plasmonics enhancement, as evidenced by high-resolution photoluminescence imaging. The energy band gap estimated based on cyclic voltammetry was between 2.38 and 2.61 eV.

Nine rhenium(i) complexes possessing three carbonyl groups together with a bidentate coordinated 2,6-di(thiazol-2-yl)pyridine derivative were synthesized to examine the impact of structure modification of the triimine ligand on the photophysical, thermal and electrochemical properties of [ReCl(CO)3(4-Rn-dtpy-κ2N)]. The Re(i) complexes were fully characterized using IR, 1H and 13C, HRMS-ESI and single crystal X-ray analysis. Their thermal properties were evaluated using DSC and TGA measurements. Photoluminescence spectra of [ReCl(CO)3(4-Rn-dtpy-κ2N)] were investigated in solution and in the solid state, at 298 and 77 K. Both emission wavelengths and quantum yields of [ReCl(CO)3(4-Rn-dtpy-κ2N)] were found to be structure-related, demonstrating a crucial role of the substituent attached to the 2,6-di(thiazol-2-yl)pyridine skeleton. In order to fully understand the photophysical properties of [ReCl(CO)3(4-Rn-dtpy-κ2N)], density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed. Furthermore, the complexes which showed appropriate solubility in chloroform were tested as an emissive active layer in OLED devices.

Novel symmetrical anthracene derivatives with bulky carbazolyl-fluorene, diphenylamino-fluorene, or carbazolyl-carbazole units connected to the anthracene frame through an ethynyl bridge were synthesized in excellent yield by using Sonogashira cross-coupling. The ethynyl bridge in the anthracene dyes increases π-electron conjugation and the bulky substituents considerably attenuate intermolecular interactions. The dyes possess high thermal stability, tremendous solubility in common organic solvents, and especially high photoluminescence quantum yield (Φf) in solution in the range of 77–98 %. OLED devices were fabricated. The AFM images of thin films and blends prepared from all compounds show a uniform and flat surface, indicating excellent film-forming properties. Devices incorporating the anthracene derivative with diphenylamino-fluorene end-capping groups exhibited the highest value of current density (J). All of the fabricated OLED devices emitted yellowish-orange light under applied voltage.

New azomethine-phthalic (AzPhDIs) and azomethine-naphthalene (AzNDIs) diimides were synthesized in condensation reaction of diamines containing phthalic or naphthalene diimide core and two aldehydes: 4-(4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecyloxy)benzaldehyde and 4-octadecyloxybenzaldehyde. The phase behavior of azomethine-diimides was examined by differential scanning calorymetry (DSC) and polarized optical microscopy (POM). AzPhDIs exhibited liquid crystalline properties in wide temperature range, whereas AzNDIs were not liquid crystalline. Thermal stability was investigated by thermogravimetric analysis (TGA). Azomethine-diimides exhibited high decomposition temperatures in the range between 360 and 401 °C. Optical properties were studied by UV–vis and photoluminescence (PL) measurements. Azomethine-diimides emitted blue light in NMP solution and blends with PMMA. The investigated compounds were electrochemically active and underwent reversible reduction and irreversible oxidation processes as evidenced by cyclic voltammetry (CV). Azomethine-diimides exhibited LUMO and HOMO levels in the range of −3.87 to −4.2 eV and −5.56 to−6.02 eV, respectively.

Several new rhenium(I) complexes [ReCl(CO)3(4′-R-terpy-κ2N)] incorporating 2,2′:6′,2′′-terpyridine-based ligands were successfully synthetized and characterized by IR, NMR (1H and 13C), UV-vis spectroscopy and single crystal X-ray analysis. The luminescent properties of [ReCl(CO)3(4′-R-terpy-κ2N)] were studied in solution and solid state, at 298 and 77 K. To better understand the photophysical properties of [ReCl(CO)3(4′-R-terpy-κ2N)], density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed. Preliminary studies towards application of these complexes in organic light emitting diodes (OLEDs) were carried out, including testing the possibility of electroluminescence intensity increase by including metallic nanowires in the structure design.

Six new Re(i) complexes of the general formula [ReCl(CO)3(4'-R-terpy-κ(2)N)] with 2,2':6',2''-terpyridine-based ligands have been synthesized and characterized by IR, NMR ((1)H and (13)C), UV-Vis spectroscopy and single crystal X-ray analysis. The luminescent properties of [ReCl(CO)3(4'-R-terpy-κ(2)N)] were studied in solution and solid state, at 298 and 77 K, respectively. To obtain detailed insight into the electronic structures and spectroscopic properties of [ReCl(CO)3(4'-R-terpy-κ(2)N)], the density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed. Also, the suitability of this class of materials for being applied in organic light emitting diodes (OLEDs) has been preliminarily tested.

The unsymmetrical and symmetrical azines prepared by condensation of benzophenone hydrazone with (di)aldehydes with thiophene rings were reported in this study The structures of obtained compounds were characterized by FTIR, 1 H NMR, and 13 C NMR spectroscopy as well as elemental analysis. Optical, electrochemical, and thermal properties of azines were investigated. The unsymmetrical azine with bithiophene unit exhibited liquid crystalline properties as was detected by DSC and POM experiments. All compounds are electrochemically active, however, only azines with bithiophene structure undergo reversible reduction process as was found in cyclic and differential pulse voltammetry (CV and DPV) studies. Additionally, the electronic properties, that is, orbital energies and resulting energy gap were calculated theoretically by density functional theory (DFT). The photovoltaic properties of two azines as active layer in organic solar cells at the configuration ITO/PEDOT:PSS/active layer/Al under an illumination of 1.3 mW/cm 2 were studied. Active cell layers blends of poly 3-hekxylthiophene (P3HT) or poly 3-butylthiophene (P3OT) with azines were applied. The device comprising P3HT with symmetrical azine containing bithiophene unit showed the highest value of power conversion efficiency (0.82%). To the best of our knowledge, the azines are very seldom considered as potential compounds in active layer in bulk heterojunction (BHJ) solar cells.

New polyimides and copolyimides were obtained by polycondensation of 2,5-bis(p-aminophenyl)-1,3,4-oxadiazole with one of the three aromatic dianhydrides: 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4′-(4,4′-isopropylidene-diphenoxy)bis(phthalic anhydride) and 4,4′-tetraphthaloyl-bis(1,8-naphthalene dicarboxylic)dianhydride. The photophysical properties such as UV absorption, photoluminescence (PL), electrochemical and spectroelectrochemical properties of the copolymers were evaluated. Additionally, their thermal behavior was investigated. The polymers dissolved in NMP and in the solid state as blend with nonemissive poly(methyl methacrylate) emitted blue light with the highest intensity under excitation wavelength ( λ ex ) 340 nm, whereas, under λ ex = 405 nm green fluorescence was observed with double-exponential lifetime. Longer decay constants were estimated for polymers in blend as compared with the ones obtained for solutions. The electronic properties, such as, HOMO–LUMO levels and band gaps were calculated via cyclic voltammetry (CV) and differential pulse voltammetry (DPV) and for models of polyimides were calculated theoretically by density functional theory (DFT). All of the polymers exhibited reversible reduction and non-reversible oxidation process. The electrochemical band gaps based on DPV measurements were in the range of 1.79–2.50 eV. Spectral changes in UV–vis region under applied potential were observed. Decreasing of applied potential to negative values resulted in appearance of new band around 600 nm in the case of film prepared from polyimide with naphthalene imide rings and with copolyimide containing naphthalene diimide and phthalic imide structures. The obtained polymers exhibited glass transition temperatures ( T g ) in the range of 227–336 °C and decomposition temperature ( T d ) in the range of 382–505 °C.

Two series of azines and their azomethine analogues were prepared via condensation reaction of benzaldehyde, 2-hydroxybenzaldehyde, 4-pyridinecarboxaldehyde, 2-thiophenecarboxaldehyde, and 4-(diphenylamino)benzaldehyde with hydrazine monohydrate and 1,4-phenylenediamine, respectively. The structures of given compounds were characterized by FTIR, (1)H NMR, and (13)C NMR spectroscopy as well as elemental analysis. Optical, electrochemical, and thermal properties of all compounds were investigated by means of differential scanning calorimetry (DSC), UV-vis spectroscopy, stationary and time-resolved photoluminescence spectroscopy, and cycling voltammetry (CV). Additionally, the electronic properties, that is, orbital energies and resulting energy gap were calculated theoretically by density functional theory (DFT). Influence of chemical structure of the compounds on their properties was analyzed.

Results of optical spectroscopy reveal strong influence of plasmon excitations in silver nanowires on the fluorescence properties of poly(3-hexylthiophene) (P3HT), which is one of the building blocks of organic solar cells. For the structure where a conductive polymer poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) was used as a spacer in order to minimize effects associated with non-radiative energy transfer from P3HT to metallic nanoparticles, we demonstrate over two-fold increase of the fluorescence intensity. Results of time-resolved fluorescence indicate that the enhancement of emission intensity can be attributed to increased absorption of P3HT. Our findings are a step towards improving the efficiency of organic solar cells through incorporation of plasmonic nanostructures. (C) 2013 AIP Publishing LLC. Publisher PDF