| 1. |
- Baryshnikov, Gleb V., et al.
(author)
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Aromaticity and photophysics of tetrasila- and tetragerma-annelated tetrathienylenes as new representatives of the hetero[8]circulene family
- 2019
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 21:18, s. 9246-9254
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Journal article (peer-reviewed)abstract
- The electronic structure, absorption and emission spectra, aromaticity and photophysical behavior of the recently synthesized tetrasilatetrathia[8]circulene and tetragermatetrathia[8]circulene compounds have been studied computationally. Both compounds demonstrate a specific bifacial aromaticity, which is unusual for hetero[8]circulenes; the inner eight-membered core sustains an expected strong paratropic magnetically-induced ring current, while the outer perimeter contains saturated Si(Et)(2) and Ge(Et)(2) moieties which break the conjugation between the thiophene rings. The overall magnetically-induced ring current for both studied circulenes is close to zero because of the strong local diatropic currents in each thiophene ring that compensate the paratropic counterpart. The electronic absorption and emission spectra of tetrasilatetrathia[8]circulene and tetragermatetrathia[8]circulene demonstrate a clear visible vibronic progression. The 0-0 band is the most active one in the absorption spectra, while in the fluorescence spectra the 0-1 band composed of several normal vibrations is more intense compared with the 0-0 band in excellent agreement with experiment. Accounting for spin-orbit coupling effects, an analysis of the photophysical constants for the two compounds demonstrates: (1) a clear manifestation of the internal heavy atom effect on the inter-system crossing efficiency; (2) one to two order domination of non-radiative rates over the fluorescence rate; and (3) that the S-1-S-0 internal conversion is extremely slow and can not compete with the fluorescence, while the S-1-T-n inter-system crossing is a main deactivation channel of the S-1 excited state. These results provide new insight into the electronic structure and photophysics of tetrasilatetrathia[8]circulene and tetragermatetrathia[8]circulene as novel standalone representatives of hetero[8]circulenes - tetraannelated derivatives of tetrathienylene.
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| 2. |
- Gusev, Alexey N., et al.
(author)
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Schiff Base Zinc(II) Complexes as Promising Emitters for Blue Organic Light-Emitting Diodes
- 2021
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In: ACS Applied Electronic Materials. - : American Chemical Society (ACS). - 2637-6113. ; 3:8, s. 3436-3444
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Journal article (peer-reviewed)abstract
- Organometallic blue fluorescent Zn(II) Schiff base complexes are synthesized and explored computationally in order to use them in organic electroluminescent heterostructures. Characterization of these pyrazolone-based azomethine-zinc complexes was accomplished by various physicochemical techniques to get insight into their applicability as an active layer in light-emitting diodes. All the complexes demonstrate high thermal stability and remarkable photoluminescence both in solution and in the solid state with maximum in the blue region. Quantum chemical calculations of the first exited electronic state and vertical singlet-singlet electronic transitions by means of time-dependent density functional theory calculations and results show that the origin of the luminescence for the target complexes refers to the intraligand charge transfer within the Schiff bases. The constructed light-emitting diodes demonstrate low input voltage (3.2-4.0 V), brightness at a level of 4300-11,600 Cd m(-2), and external quantum efficiency of up to 3.2%, which is a good value for purely fluorescent organic light-emitting diodes.
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| 3. |
- Pedersen, S. K., et al.
(author)
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Anti-Aromatic versus Induced Paratropicity : Synthesis and Interrogation of a Dihydro-diazatrioxa[9]circulene with a Proton Placed Directly above the Central Ring
- 2020
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In: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 59:13, s. 5144-5150
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Journal article (peer-reviewed)abstract
- We present a high-yielding intramolecular oxidative coupling within a diazadioxa[10]helicene to give a dihydro-diazatrioxa[9]circulene. This is the first [n]circulene containing more than eight ortho-annulated rings (n>8). The single-crystal X-ray structure reveals a tight columnar packing, with a proton from a pendant naphthalene moiety centred directly above the central nine-membered ring. This distinct environment induces a significant magnetic deshielding effect on that particular proton as determined by 1H NMR spectroscopy. The origin of the deshielding effect was investigated computationally in terms of the NICS values. It is established that the deshielding effect originates from an induced paratropic ring current from the seven aromatic rings of the [9]circulene structure, and is not due to the nine-membered ring being antiaromatic. UV/Vis spectroscopy reveals more efficient conjugation in the prepared diazatrioxa[9]circulene compared to the parent helical azaoxa[10]helicenes, and DFT calculations, including energy levels, confirm the experimental observations.
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| 4. |
- Chapran, Marian, et al.
(author)
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Electronic Structure of Exciplexes and the Role of Local Triplet States on Efficiency of Thermally Activated Delayed Fluorescence
- 2023
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In: ACS APPLIED ELECTRONIC MATERIALS. - : American Chemical Society (ACS). - 2637-6113. ; 5:3, s. 1489-1501
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Journal article (peer-reviewed)abstract
- In this work, we present an investigation of the electronic states in a series of thermally activated delayed fluorescence (TADF) exciplexes formed with the popular electron-transport compound TpBpTa and hole-transporting TCTA, TAPC, TPD10, TPD, and NPB. We rationalize the photophysical behavior of exciplexes by using computational methods and demonstrate that the reason for the commonly observed temporal red shift in the time-resolved spectra is related to the distribution of molecular conformations, thus CT energy, in film. We also use spectrally resolved thermoluminescence (SRTL) measurements to give insight into the trapping phenomena in exciplex blends. The results demonstrate that trapped charge carriers in the majority of studied exciplexes recombine through the luminescent intermolecular CT state. In addition, we report OLED devices using the said exciplexes in the emissive layer. The best performance is obtained with the TCTA:TpBpTa and TAPC:TpBpTa exciplexes showing maximum external quantum efficiencies (EQEs) of 8.8% and 7.2%, respectively.
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| 5. |
- Karaush-Karmazin, Nataliya N., et al.
(author)
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Aromaticity of Heterocirculenes
- 2021
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In: Chemistry. - Switzerland : MDPI. - 2624-8549. ; 3:4, s. 1411-1436
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Journal article (peer-reviewed)abstract
- This review summarizes the results on the aromaticity of a series of synthesized and hypothetical neutral heterocirculene molecules and their double charged ions. The aromaticity of heterocirculenes is a direct reflection of their electronic structure responsible for the specific optoelectronic and photophysical properties. We show how the presence of a heteroatom in the outer macrocycle affects the aromaticity of hetero[8]circulenes. In addition, we also describe the change in aromaticity and strain energy for a series of the "lower" (n < 8) and "higher" (n > 8) hetero[n]circulenes. It was demonstrated that the loss of planarity with increased strain leads to an increased antiaromaticity of the lower hetero[n]circulenes, whereas higher hetero[n]circulenes demonstrate a more pronounced aromatic nature because of the small departure from planarity of each heteroarene ring in hetero[n]circulene molecule. Finally, we discuss the aromatic nature of the first examples of pi-extended hetero[8]circulenes.
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| 6. |
- Karaush-Karmazin, Nataliya N., et al.
(author)
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Furans and Their Benzo Derivatives : Structure
- 2021
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In: Comprehensive Heterocyclic Chemistry IV. - : Elsevier BV. ; , s. 190-232
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Book chapter (other academic/artistic)abstract
- This article provides an overview of the results of 10-year (2008–2018) studies on the structure and properties of furans and their benzo derivatives. Particular attention is paid to strategies to improve stability of furan-containing systems by introducing p-block inorganic elements and by furan annelation with other conjugated aromatic systems. We also show that furans and benzofurans represent advantageous alternatives to thiophenes and thiophene-based building units toward the design and synthesis of novel “green” polymeric materials with desired properties for optoelectronic applications.
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| 7. |
- Karaush-Karmazin, Nataliya N., et al.
(author)
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Impact of heteroatoms (S, Se, and Te) on the aromaticity of heterocirculenes
- 2019
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In: New Journal of Chemistry. - : ROYAL SOC CHEMISTRY. - 1144-0546 .- 1369-9261. ; 43:30, s. 12178-12190
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Journal article (peer-reviewed)abstract
- A series of thia[7]circulenes and novel Se-, Te-, S/Te-, and Se/Te-substituted [8]circulenes have been studied by calculations of nucleus-independent chemical shift indices and gauge including magnetically induced currents to interpret the impact of heteroatoms on the aromatic properties of these polyheterocyclic species. The calculations indicate that all the studied hetero[7]circulenes and hetero[8]circulenes consist of two concentric subsystems: an inner seven- or eight-membered core is antiaromatic because of the existence of a paratropic ring current, and an outer system of benzene and hetarene rings that exhibit aromatic behaviour due to the circulation of diatropic ring currents. Thus, most of the hetero[7]circulenes can be considered as slightly antiaromatic because of the slight domination of the paratropic ring currents over the diatropic ones, whereas hetero[8]circulenes represent aromatic species due to the prevailing contribution of the diatropic currents. The antiaromaticity gradually increases with more scattered arrangements of the thiophene and benzene rings in each series of di-, tri-, tetra-, and pentathia[7]circulenes because of the reduced conjugation effect between the neighboring thiophene and benzene rings. Loss of planarity with increased strain leads to an increased antiaromatic character of the lower representatives of the thia[n]circulenes, whereas higher thia[n]circulenes demonstrate a more pronounced aromatic nature because of the small deviation from planarity. The ring current topology is found to be quite insensitive to the heteroatom type, number of hetarene rings and the size of the inner ring; this clearly manifests the special electronic structure of hetero[n]circulenes containing two concentric cyclic subsystems.
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| 8. |
- Karaush-Karmazin, Nataliya N., et al.
(author)
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Impact of molecular and packing structure on the charge-transport properties of hetero[8]circulenes
- 2021
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In: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 9:4, s. 1451-1466
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Journal article (peer-reviewed)abstract
- In organic photovoltaic cells, absorption of light leads to the formation of excitons, which then diffuse to the donor/acceptor interface to generate photocurrent. The distance from which excitons can reach the interface is constrained by the exciton diffusion length, which has been difficult to quantitatively model or predict due to structural and energetic disorder. Modern non-fullerene acceptors have been shown to possess exceptionally large diffusion lengths, along with well-defined molecular and packing structures, suggesting that a predictive framework for materials design and computational screening may be possible. In this work, we demonstrate that the large diffusion coefficient recently observed in an archetypical non-fullerene acceptor, IDIC, can be accurately quantified using density functional theory, and that the low energetic disorder means that the crystal structure provides a meaningful starting point to understand exciton motion in thin films. Accounting for the short- and long-range excitonic interactions, as well as spatiotemporal disorder, we demonstrate that both Monte-Carlo techniques and a simple sum-over-rates method can accurately predict experimental values for exciton diffusivity and diffusion length. The simplicity and accuracy of this approach are directly linked to the structural order of these materials, and an electronic coupling profile that is unusually resilient to thermal distortions - highlighting the potential of the sum-over-rates method for computational materials screening. Moreover, we show that these factors, combined with the low reorganisation energy and significant long-range electronic coupling, lead to diffusion rates that approach the upper limit of incoherent energy transfer and long diffusion lengths that relieve constraints on organic solar cell device architectures.
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| 9. |
- Karaush-Karmazin, Nataliya N., et al.
(author)
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Structure, stability and electronic properties of one-dimensional tetrathia- and tetraselena[8]circulene-based materials : a comparative DFT study
- 2020
-
In: New Journal of Chemistry. - : Royal Society of Chemistry. - 1144-0546 .- 1369-9261. ; 44:17, s. 6872-6882
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Journal article (peer-reviewed)abstract
- Conjugated polymers gain much attention due to the promising applications in organic electronic device technology. In this work, we theoretically study the structures and electronic properties of a novel class of nanostructures, namely one-dimensional tetrathia[8]circulenes (TTC) and tetraselena[8]circulenes (TSC) predicted to be promising semiconducting soft materials. It is found that all nanoribbons are thermodynamically stable and that their electronic properties depend significantly on the type of fusing between the monomers. In particular, the band gap tends to decrease while moving from the directly fused TTC/TSC ribbons to the structures coupled via a benzene-core linker and then to the ribbons fused through a four-membered ring. Therefore, both coupling type and length of oligomers allow one to manipulate the electronic and optical properties of the studied ribbons. The band structure calculations of infinite nanoribbons reveal direct band gaps that decrease from 2.28 to 2.14 eV for the TTC ribbons of the first and second fusion types. The TSC structures demonstrate the same trend exhibiting band gap narrowing from 2.41 (type I) up to 2.11 eV (type II). The type III ribbons possess a lack of periodicity due to the close-lying energy minima for the possible twisting configurations of TTC and TSC moieties relative to the linking four-membered ring.
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| 10. |
- Minaeva, Valentina A., et al.
(author)
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Structure and Spectral Properties of Thianthrene and Its Benzoyl-Containing Derivatives
- 2023
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In: Eurasian Journal of Chemistry. - : Karagandy University of the name of academician E.A. Buketov. - 2959-0663 .- 2959-0671. ; 111:3, s. 89-103
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Journal article (peer-reviewed)abstract
- The IR absorption spectra of the recently synthesized series of benzoyl-containing thianthrene derivatives were studied in the context of their structural identification. Geometry optimizitation of the ground singlet state by density functional theory (DFT) calculations with the gradient and Hessian search were performed for thianthrene molecule in the framework of the C2v symmetry restriction. The excited singlet and triplet states of thianthrene were found to be distorted along the b3u vibrational mode of the D2h point group, as well as the ground state, which leads to the non-planar batterfly-like structure (C2v). But the excited states require additional symmetry reduction; they are closer to planarity but have no symmetry elements. Optimized ground states structure for the thianthrene-benzoyle molecule and its four derivatives with fluoro-substituents and different substitution positions were analysed through complete assignment of all their vibrational modes and comparison with experimental infrared absorption spectra. A good agreement between experimental data and DFT calculated IR spectra provides additional structural support to results of the X-ray diffraction analysis of all synthesized compounds. The Hirshfeld surfaces analysis of the crystalline 3-fluorobenzoylthianthrene (T3F) was performed in order to analyze intermolecular interactions in T3F crystal. It indicates the presence of weak CH...F, CH...S and CH...O intermolecular contacts, stabilizing the crystal structure of T3F. The CH...O interactions appear in the IR spectrum of T3F crystal as two vibrational modes with frequencies 3084 and 3078 cm-1. The intermolecular interactions CH...F and CH...S do not affect the IR spectrum of T3F.
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