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In this research, six novel unsymmetrical imino-1,8-naphthalimides (AzNI) were synthesized. Comprehensive thermal (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), optical (UV-Vis, photoluminescence), and electrochemical (CV, DPV) studies were carried out to characterize these new compounds. The molecules showed the onset of thermal decomposition in the temperature range 283–372 °C and molecular glass behavior. Imino-1,8-naphthalimides underwent reduction and oxidation processes with the electrochemical energy band gap (Eg) below 2.41 eV. The optical properties were evaluated in solvents with different polarities and in the solid-state as a thin films and binary blends with poly(N-vinylcarbazole): (2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole) (PVK:PBD). Presented compounds emitted blue light in the solutions and in the green or violet spectral range in the solid-state. Their ability to emit light under external voltage was examined. The devices with guest-host structure emitted light with the maximum located in the blue to red spectral range of the electroluminescence band (EL) depending on the content of the AzNI in the PVK:PBD matrix (guest-host structure).

ASAP Article - Articles ASAP (as soon as publishable) are posted online and available to view immediately after technical editing, formatting for publication, and author proofing., Five new unsymmetric thiophene imines end-capped with an electron-donating amine (−NH2) group were obtained using a simple synthetic route, that is, the melt condensation of 2,5-diamino-thiophene-3,4-dicarboxylic acid diethyl ester with commercially available aldehydes. Their thermal stability and electrochemical and photophysical (absorption (UV−vis) and photoluminescence (PL)) properties were examined and density functional theory calculations were performed. The imines were thermally stable above 200 °C. They underwent reduction and oxidation processes and exhibited an energy band gap electrochemically estimated between 1.81 and 2.44 eV. They absorbed radiation from the UV and visible range to 480 nm and showed weak light emission. These compounds were investigated as hole transporting materials in solar cells with the structure FTO/b-TiO2/m-TiO2/perovskite/imine/Au. The highest photoelectric conversion efficiency was observed for compounds with a morpholine derivative substituent.

A new series of 1,8-naphtalimides containing an imine bond at the 3-position of the naphthalene ring was synthesized using 1H, 13C NMR, FTIR, and elementary analysis. The impact of the substituent in the imine linkage on the selected properties and bioimaging of the synthesized compounds was studied. They showed a melting temperature in the range of 120–164 °C and underwent thermal decomposition above 280 °C. Based on cyclic and differential pulse voltammetry, the electrochemical behavior of 1,8-naphtalimide derivatives was evaluated. The electrochemical reduction and oxidation processes were observed. The compounds were characterized by a low energy band gap (below 2.60 eV). Their photoluminescence activities were investigated in solution considering the solvent effect, in the aggregated and thin film, and a mixture of poly(N-vinylcarbazole) (PVK) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD) (50:50 wt.%). They demonstrated low emissions due to photoinduced electron transport (PET) occurring in the solution and aggregation, which caused photoluminescence quenching. Some of them exhibited light emission as thin films. They emitted light in the range of 495 to 535 nm, with photoluminescence quantum yield at 4%. Despite the significant overlapping of its absorption range with emission of the PVK:PBD, incomplete Förster energy transfer from the matrix to the luminophore was found. Moreover, its luminescence ability induced by external voltage was tested in the diode with guest–host configuration. The possibility of compound hydrolysis due to the presence of the imine bond was also discussed, which could be of importance in biological studies that evaluate 3-imino-1,8-naphatalimides as imaging tools and fluorescent materials for diagnostic applications and molecular bioimaging.

Novel oxetane-functionalized derivatives were synthesized to find the impact of carbazole substituents, such as 1-naphtyl, 9-ethylcarbazole and 4-(diphenylamino)phenyl, on their thermal, photophysical and electrochemical properties. Additionally, to obtain the optimized ground-state geometry and distribution of the frontier molecular orbital energy levels, density functional theory (DFT) calculations were used. Thermal investigations showed that the obtained compounds are highly thermally stable up to 360 °C, as molecular glasses with glass transition temperatures in the range of 142–165 °C. UV–Vis and photoluminescence studies were performed in solvents of differing in polarity, in the solid state as a thin film on glass substrate, and in powders, and were supported by DFT calculations. They emitted radiation both in solution and in film with photoluminescence quantum yield from 4% to 87%. Cyclic voltammetry measurements revealed that the materials undergo an oxidation process. Next, the synthesized molecules were tested as hole transporting materials (HTM) in perovskite solar cells with the structure FTO/b-TiO2/m-TiO2/perovskite/HTM/Au, and photovoltaic parameters were compared with the reference device without the oxetane derivatives.

A simple and rapid synthesis of six new, stable β-ketoenamines by coupling 3-amino-1,8-naphthalimide derivatives with 2-(4-pyrimidinyl)-malondialdehyde in the presence of trifluoroacetic acid was developed. Two of the synthesized 3-amino-1,8-naphthalimide derivatives were condensed with 9H-fluorene-2-carboxaldehyde, resulting in azomethine products. The structure of obtained compounds was confirmed by 1H and 13C NMR, COSY, HMQC, FTIR spectroscopy and elemental analysis. The photophysical, electrochemical and thermal properties of the compounds were investigated. Additionally, calculations using density functional theory were performed to obtain the optimized ground-state geometry and distribution of the HOMO and LUMO levels as well as UV–Vis and photoluminescence spectra of the synthesized compounds. DSC measurements revealed that the compounds form amorphous material with glass transition temperature in the range of 41–146 °C and are thermally stable up to 300 °C. β-Ketoenamines have higher glass transition temperature, smaller energy gap (2.11–2.47 eV), higher PL quantum efficiency in solution (5.25–12.97%) and ability to aggregation-induced emission than the azomethines.

New phenanthro[9,10-d]imidazole derivatives bearing thienyl motifs were prepared by the condensation reaction. They were characterized using elemental analysis and NMR spectroscopy. Thermal, electrochemical, spectroelectrochemical, and optical properties of synthesized compounds were investigated. The prepared compounds were electrochemically active and showed multistep electrochemical reduction and oxidation. Phenanthro[9,10-d]imidazole derivatives exhibited luminescence with emission bands around 400 nm. The photoluminescence quantum yields in solution were found between 41–72%. The photoluminescence of the films, prepared from the synthesized compounds, was observed in the blue range of light. Additionally, the electroluminesce ability of the obtained molecules was preliminary tested.

Three push-pull molecules with linear, quadrupolar and tripodal arrangements, consisting of triphenylamine (electro-donor) substituted with malononitrile groups (electro-acceptor), were synthesized with high yield by a simple procedure. Impact of the number of malononitrile substituents on optoelectronic properties was investigated with cyclic voltammetry, absorption and emission spectroscopy, as well as density functional theory calculation. The derivatives formed amorphous materials and exhibited low energy band gaps ranging from 2.06 to 2.49 eV. UV–Vis absorption and photoluminescence emission spectra were investigated in solutions (CHCl3, NMP) and in solid-state as thin films and two kinds of blends (with PMMA and PVK:PBD). Quantum yield of photoluminescence was dependent on the molecule structure, solvent, and solid-state layer formulation. The compounds exhibited high photoluminescence quantum yield in the range of 15–42% and 12–59% in solid-state as film and blend with PMMA (1 wt%), respectively, being promising for applications in light emitting diodes. The diodes with active layer consisting of neat derivatives and compounds molecularly dispersed in PVK:PBD (50:50 wt%) matrix showed orange and green electroluminescence.

A new series of thiophene-based azomethines differing in the core structure was synthesized. The effect of the central core structure in azomethines on the thermal, optical and electrochemical properties was investigated. The obtained compounds exhibited the ability to form a stable amorphous phase with a high glass transition temperature above 100 °C. They were electrochemically active and undergo oxidation and reduction processes. The highest occupied (HOMO) and the lowest unoccupied molecular (LUMO) orbitals were in the range of −3.86–−3.60 eV and −5.46–−5.17 eV, respectively, resulting in a very low energy band gap below 1.7 eV. Optical investigations were performed in the solvents with various polarity and in the solid state as a thin film deposited on a glass substrate. The synthesized imines absorbed radiation from 350 to 600 nm, depending on its structure and showed weak emission with a photoluminescence quantum yield below 2.5%. The photophysical investigations were supported by theoretical calculations using the density functional theory. The synthesized imines doped with lithium bis-(trifluoromethanesulfonyl)imide were examined as hole transporting materials (HTM) in hybrid inorganic-organic perovskite solar cells. It was found that both a volume of lithium salt and core imine structure significantly impact device performance. The best power conversion efficiency (PCE), being about 35–63% higher compared to other devices, exhibited cells based on the imine containing a core tiphenylamine unit.

In this paper, we describe both new as well as described in our previous works 1,8-naphthalimide derivatives substituted at the 3-C position with imine or β-ketoenamine unit in order to demonstrate a broader scope of research enabling of analysis between the structure-properties relationship relevant to the application of these compounds in organic electronics and cellular imaging. Thermal, physicochemical, optical, electrochemical, electroluminescence, and biological properties of a series of derivatives containing the 1,8-naphthalimide unit were tested and compared. This allowed the determination of the impact of substituents in the imide part (hexylamine, phenylethyl, benzyl, fluorobenzyl, methylbenzyl), type of bond (imine or ketoenamine) as well as the substituent on the naphthalene ring (2-hydroxyphenyl, 5-bromo-2-hydroxyphenyl, 3,5-diodo-2-hydroxyphenyl, pyrimidines) on their properties. Moreover, the properties in the aggregating state were tested in the MeOH/PBS system. Imines are susceptible to the hydrolysis process and aggregation-caused photoluminescence quenching (ACQ). In turn, β-ketoenamine shown excited-state intramolecular proton transfer promoted by aggregation (AIEE). Our studies can be helpful in the further design of compounds containing the 1,8-naphthalimide structure for various applications.

In this work, a series of six rhenium(I) complexes bearing 2,2′:6′,2″-terpyridine (terpy), 2,6-di(thiazol-2-yl)pyridine (dtpy), and 2,6-di(pyrazin-2-yl)pyridine (dppy) with appended quinolin-2-yl and N-ethylcarbazol-3-yl groups were prepared and spectroscopically investigated to evaluate the photophysical consequences of both the trisheterocyclic core (terpy, dtpy and dppy) and the heterocyclic substituent. The [ReCl(CO)3(Ln-κ2N)] complexes are regarded as ideal candidates for getting structure–property relationships, while terpy-like framework represents an excellent structural backbone for structural modifications. The replacement of the peripheral pyridine rings of 2,2′:6′,2″-terpyridine by thiazoles and pyrazines resulted in a significant red-shift of the absorption and emission of [ReCl(CO)3(Ln-κ2N)] due to stabilization of the ligand-centred LUMO orbital. Both quinoline and N-ethylcarbazole are extended π-conjugation organic chromophores, but they differ in electron-donating abilities. The low-energy absorption band of Re(I) complexes with the triimine ligands bearing quinolin-2-yl group was contributed by the metal-to-ligand charge-transfer (MLCT) electronic transitions. The introduction of electron-donating N-ethylcarbazol-3-yl substituent into the triimine acceptor core resulted in the change of the character of the HOMO of Re(I) complexes and a significant increase of molar absorption coefficients of the long-wavelength absorption, which was assigned to a combination of 1MLCT and 1ILCT (intraligand charge-transfer) transitions. Regardless of the appended heteroaromatic group, the emitting excited state of Re(I) terpy-based complexes was demonstrated to have predominant 3MLCT character, as evidenced by comprehensive studies including static and time-resolved emission spectroscopy along with ultrafast transient absorption measurements. The diodes with Re(I) complexes dispersed molecularly in a PVK:PBD matrix were emissive and effects of the complex structure on colour of emitted light and its intensity was pronounced.

Series of Re(I) carbonyls complexes were designed and synthesized to explore the impact of the triimine skeleton and number of methoxy groups attached to aryl substituents on their optoelectronic and thermal properties. The chemical structures of the prepared complexes were confirmed by 1H and 13C NMR spectroscopy, HR-MS, elemental anlsysis, and X-ray measurements. DSC measuremtns showed that they melted in the range of 198–325 °C. Some of them form stable molecular glasses with high glass transition temperatures (158–173 °C). Experimentally obtained optical properties were supported by DFT calculations. The UV–Vis spectra display a series of overlapping absorption bands in the range 200–350 nm, and much weaker broad band in the visible spectral region, due to intraligand and charge transfer transitions, respectively. All synthesized complexes were emissive in solution and in solid state as powder. Moreover, when applied in diodes, some of them exhibited ability for emission of light under external voltage with maximum of electroluminescence band located at 591–630 nm.

Three novel perylene diimide derivatives with bulky aromatic moieties (fluorene, carbazolyl-fluorene, and anthracyl-fluorene) connected via triple bonds with perylene core were successfully designed and synthesized. The chemical structure of prepared compounds was confirmed by 1H and 13C NMR and mass spectrometry. Their optimized ground-state geometry and frontier molecular orbitals were theoretically estimated based on density functional theory. The compounds undergo the reversible electrochemical reduction process and exhibit very low energy band gaps (1.56–1.98 eV) being promising for electronic applications. They also display excellent solubility, high thermal stability and luminescence in solution and in the solid state as a film in the red spectral region. The highest photoluminescence quantum yield (79% in solution and 28% in the film) was found for perylene diimide bearing fluorene unit. All molecules showed the ability for light emission under an applied voltage. The fabricated diodes with structure ITO/PEDOT:PSS/compound/Al exhibited electroluminescence with maximum emission band located between 685 and 732 nm. The most intense electroluminescence, which was additionally plasmonically enhanced by incorporating silver nanowires, was observed for the device based on molecules with anthracene structure.

Novel 1,8-naphthalimides core substituted at 3-C position via imine bond with carbazole, benzothiazole, methylindole, quinoline, benzoindole, phenylmorpholine and triphenylamine derivatives were designed, synthesized and investigated with regard to their thermal, electrochemical, and luminescence behavior. DSC measurements showed that the obtained crystalline compounds can be converted into amorphous materials with glass transition temperatures in the range of 28–54 °C, except for the molecule bearing benzoindole derivative. The prepared compounds were thermally stable with the onset of thermal decomposition in the range of 345–368 °C. Energy band gap electrochemically estimated was modulated from 2.13 to 2.52 eV. Effect of excitation wavelength on the photoluminescence relative intensity of those naphthalimides in solution was detected. Their photoluminescence maximum band was located in the range of 495–560 nm in solution with the quantum yield from 0.2 to 14.0%. In the film, they emitted light in the blue and green spectral region with quantum yields from 1.1 to 3.6%. The electroluminescence ability of core substituted 1,8-naphthalimides was tested in the single-layer diode geometry. They were utilized as an emitting layer for both non-doped and doped single-layer OLEDs fabricated by solution processing. Additionally, calculations using density functional theory were performed to obtain the optimized ground-state geometry and distribution of the HOMO and LUMO levels of the synthesized molecules.

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.

New aliphatic-aromatic polymers based on perylene or/and naphthalene diimide units were synthesized and investigated. The effect of diimide core on electrochemical, spectroelectrochemical (UV–vis, EPR) and emission properties was evaluated. Based on cyclic voltammetry measurements the electron affinity of synthesized polymers was estimated. It ranges from − 4.28 to − 4.14 eV which suggests that obtained materials have low-lying LUMO level and could be used in air-operating devices. Investigated polymers show also fluorescence in solution as well as in solid state as a blend with PMMA with quantum efficiency reached up to 68%.

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.

New arylene bisimide derivatives containing imine linkages and anthracene units were synthesized. Azomethine diimides were prepared via condensation reaction of 9-anthracenecarboxaldehyde and diamines with phthalic diimide or naphthalene diimide core and Schiff base linkers. They were characterized by FTIR spectroscopy, elemental analysis and mass spectrometry (MALDI-TOF-MS). The synthesized compounds exhibited high resistance against thermal decomposition up to 400 °C. Investigated compounds are electrochemically active and undergo reversible electrochemical reduction and irreversible oxidation processes as was found in cyclic voltammetry studies. The photoluminescence measurements of synthesized compounds in solid state as thin film on glass substrate revealed their ability to emission of the blue light with quantum yield efficiency about 2%. The electronic structure and spectroscopic properties of prepared azomethine diimides were also calculated by the density functional theory (DFT). The electrical properties of the diimide derivatives were preliminary investigated by current–voltage measurements.

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.

Unsymmetrical and symmetrical azomethines were obtained using the condensation reaction of diamino-thiophene-3,4 dicarboxylic acid diethyl ester with 4-(1-pyrrolidino)benzaldehyde, fluorene-2-carboxaldehyde, 1-methylindole-3-carboxaldehyde, and benzothiazole-2-carboxaldehyde. Their thermal, optical, and electrochemical properties were investigated, and the results were supported by calculations using the density functional theory. The studied compounds melted in the range of 170–260 °C and can be converted into amorphous materials with high glass transition temperatures between 76 and 135 °C. They were thermally stable up to 220–300 °C. All imines were electrochemically active and exhibited low energy band gaps below 2 eV (except for one imine with Eg = 2.39 eV) determined on the basis of cyclic voltammetry. Most of the azomethines were emissive in solution and in the solid state. Some of them showed both S1 (first excited state) emission and S2 (second excited state) emission or only fluorescence from higher excited state, which is first time observed for azomethines. The imine with the most promising properties was tested in a light-emitting diode, and its ability for emission of light under external voltage was demonstrated.

A set of N-octylphenothiazine malononitriles (P1–P4) containing (p-methoxyphenyl, p-trifluoromethylphenyl, 3,5-bis(trifluoromethyl)phenyl, or p-cyanophenyl) substituents connected via acetylene linker were designed and synthesized. The obtained structures, which exhibit A/D-π-D-A architecture, were characterized by NMR and mass spectroscopy, and elemental analyses. Photophysical, thermal, and electrical properties of these novel dyes P1–P4 were comprehensively studied and confronted with theoretical calculations. They exhibit high thermal stability of up to 306–369 °C. Compounds showed an intramolecular charge transfer (ICT) absorption band at about 480 nm and emission band at around 620 nm with quantum yields between 31 and 50% in chloroform solution. Comparison of the solution and thin film photoluminescence (PL) spectra of P1–P4 exhibit a significant red-shift of 40–70 nm in the thin film PL spectrum. Furthermore, the impact of the end-capped groups in P1–P4 on optical and electrochemical properties was investigated in detail with the support of TD/DFT calculations. The diodes based on P1–P4 with configuration ITO/PDOT:PSS/PBK:PBD:compound/Al were constructed and their electroluminescence (EL) spectra were registered. Considering the preliminary EL investigations, the beneficial effect of the presence of p-cyanophenyl as a substituent (P4) was demonstrated.

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.

The fluorinated polyimides are synthesized from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride and various diamines containing fluorene, anthraquinone, phenanthridine, stilbene, and fluorenylidene units. The polymers exhibit high glass transition temperature (Tg = 170–261 °C) and high thermal stability with decomposition temperatures (Td) in the range of 320–560 °C and 290–520 °C in nitrogen atmosphere and in air, respectively. The optical properties, that is, absorption in UV–vis range and photoluminescence of obtained polyimides, are investigated in solution and in solid state as a blend with inert poly(methyl methacrylate). The polymers in solution and in solid state emit light in the range of 356–572 nm depending on the polymer structure. Additionally, the photoluminescence properties of the polyimide containing phenanthridine units in the backbone before and after protonation with HCl and methanesulfonic acid are tested in N-methyl-2-pyrrolidone solution. All polyimides are electrochemically active and undergo an electrochemical reduction process as is found in cyclic voltammetry. The lowest unoccupied molecular orbital (LUMO) levels are found in the range from −3.58 to −3.93 eV.

Seven aromatic hydrocarbons bearing a dicyanovinyl unit were prepared to determine the relationship between both the number of aromatic rings and location of acceptor substituent on their thermal and optoelectronic properties. Additionally, the density functional theory calculations were performed. The obtained compounds showed temperatures of the beginning of thermal decomposition in the range of 137–289 °C, being above their respective melting points found between 88 and 248 °C. They were electrochemically active and showed quasi-reversible reduction process (except for 2-(phen-1-yl)methylene)malononitrile). Electrochemically estimated energy band gaps were below 3.0 eV, in the range of 2.10–2.50 eV. The absorption and emission spectra were recorded in CHCl3 and NMP and in solid state. All compounds strongly absorbed radiation with absorption maximum ranging from 307 to 454 nm ascribed to the intramolecular charge transfer between the donor and acceptor units. The aromatic hydrocarbons were luminescent in all investigated media and exhibited higher photoluminescence quantum yields in the solid state due to the aggregation induced emission phenomena. Electroluminescence ability of selected compounds was tested in a diode with guest-host configuration. Additionally, the selected compound together with a commercial N719 was applied in the dye-sensitized solar cell.

A novel Schiff base sensor with the phenyl-ethynyl-phenyl system was designed and synthesized. The compound was characterized using FTIR, 1H and 13C NMR, elemental analysis as well as UV–vis and fluorescence spectroscopy were performed. The sensor was found to have a high level of selectivity and sensitivity to Cu2+ cation vs. other metal ions (Al3+, Ba2+, Co2+, Cr3+, Fe2+, Fe3+, Mn2+, Ni2+, Pb2+, Sr2+ and Zn2+) in acetonitrile and PBS/acetonitrile solutions. It was found that trace levels of copper ions in water can be detected inexpensively in a short period of time, when equipped with the designed sensor using only the naked eye. Moreover, the probe containing the copper ions in the acetonitrile solution showed a significant enhancement of the fluorescence intensity compared to the pure compound. Different mechanisms to explain the possibility of determining copper in both a water and in pure acetonitrile was presented. Detecting the level of copper using the proposed sensor in acetonitrile was estimated to be 0.1 nM. By visually detecting the presence of copper at the WHO maximum allowable limit of 30 μM can easily be determined. The high level of selectivity was explained by the formation of a Cu-complex which exhibited the properties that initiate 2-aminophenol oxidation.

A series of polyaromatic hydrocarbons with anthracene, phenanthrene and pyrene units connected with Schiff base junctions were synthesized via condensation of p-phenylenediamine and hydrazine with selected aldehydes. The effect of both hydrocarbon structures and presence of N-N- or phenyl- linked diimines on properties of the prepared azines and azomethines was analyzed. The obtained compounds were soluble in common organic solvents and melted in the range of 226-317°C. Their photophysical and electrochemical properties were investigated by UV-vis, photoluminescence spectroscopies and cyclic voltammetry (CV), respectively. Moreover, a density functional theory (DFT) was applied for calculation of their electronic and geometric structures as well as absorption and emission spectra. Additionally, their electron acceptor activity was preliminary tested in photovoltaic experiment.

The new Schiff bases bearing anthracene unit were synthesized from 2-aminoanthracene and various aldehydes such as: benzaldehyde, 4-(diphenylamino)benzaldehyde, 9-phenanthrenecarboxaldehyde, 9-anthracenecarboxaldehyde, and biphenyl-4-carboxaldehyde, 2-naphthaldehyde. Resulted azomethines were characterized by IR, NMR (1H and 13C), elemental analysis and UV-vis spectroscopy. The imine consists of anthracene and biphenyl moieties exhibited liquid crystal properties and their nematic phase showed Schlieren texture. The photoluminescence measurements carried out in solution and in solid state as blend with PMMA revealed the ability of the imines to emission of the blue light with quantum yield efficiency in the range of 2.18-6.03% in blend. Based on the electrochemical experiment they showed value of energy gap (Eg) in the range of 2.5-2.7eV. Additionally, density functional theory (DFT) was applied for calculations of both electronic structure and spectroscopic properties of synthesized Schiff bases. Moreover, the results obtained from preliminary tests of application of the azomethines in organic photovoltaic (OPV) devices confirmed their electron acceptor character.

The large specific surface area and strong adsorption ability of graphene oxide and its derivates such as partially or fully reduced graphene oxide are attractive for gas-sensing applications. Such materials are also easy to work with and are economically attractive and are thus suited to large scale fabrication. Here we compare graphene oxide with two partially reduced graphene oxide materials. In the first, ascorbic acid is used as a weak reducer and in the second, we demonstrate a new thiolation/reduction route which can also partially reduce graphene oxide and in addition provide thiol groups at the surface. We then compare the three materials for use in a simple drop-cast sensor system. The signal profile data from the three different sensors vary in shape and intensity as well as response and recovery times for the two different analytes investigated. The data suggests these parameters could be used as an array system to discriminate between analytes.