Supramolecular organization and electronic structure of perylene tetracarboxylic diimide: X-ray diffraction and theoretical studies

The inter- and intracolumnar arrangements of the perylene tetracarboxylic diimide (PDI) was investigated experimentally and theoretically by using X-ray diffraction with combined DFT computation and molecular dynamics simulation. The structure was found to be hexagonal with a packing parameter of ne...

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Veröffentlicht: Інститут проблем матеріалознавства ім. І.М. Францевича НАН України 2010
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spelling irk-123456789-627022014-05-25T03:01:53Z Supramolecular organization and electronic structure of perylene tetracarboxylic diimide: X-ray diffraction and theoretical studies Pokropivny, A. Методы исследования наноструктур и наноматериалов The inter- and intracolumnar arrangements of the perylene tetracarboxylic diimide (PDI) was investigated experimentally and theoretically by using X-ray diffraction with combined DFT computation and molecular dynamics simulation. The structure was found to be hexagonal with a packing parameter of nearest column a = 2.025 nm characterized by a ~ 45° twist of molecules within the columns. Меж- и внутриколоночные упорядочения перилена были исследованы экспериментально и теоретически при использовании рентгеновской дифракции с комбинированными вычислениями методами функционала плотности и молекулярной динамики. Структура кристалла определена как гексагональная с упаковочным параметром самой близкой колонки a = 2,025 нм с характерным твистом ~ 45° молекул в пределах колонок. Між- і внутрішньоколончасті впорядкування перилену було досліджено експериментально й теоретично при використанні рентгенівської дифракції з комбінованими обчисленнями методами функціоналу густини та молекулярної динаміки. Структуру кристала визначено як гексагональну з пакувальним параметром найближчої колонки a = 2,025 нм із характерним твістом ~ 45° молекул у межах колонок. 2010 Article Supramolecular organization and electronic structure of perylene tetracarboxylic diimide: X-ray diffraction and theoretical studies / A. Pokropivny // Наноструктурное материаловедение. — 2010. — № 1. — С. 53-58. — Бібліогр.: 20 назв. — англ. 1996-9988 http://dspace.nbuv.gov.ua/handle/123456789/62702 541.183.24:576.8 en Наноструктурное материаловедение Інститут проблем матеріалознавства ім. І.М. Францевича НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
topic Методы исследования наноструктур и наноматериалов
Методы исследования наноструктур и наноматериалов
spellingShingle Методы исследования наноструктур и наноматериалов
Методы исследования наноструктур и наноматериалов
Pokropivny, A.
Supramolecular organization and electronic structure of perylene tetracarboxylic diimide: X-ray diffraction and theoretical studies
Наноструктурное материаловедение
description The inter- and intracolumnar arrangements of the perylene tetracarboxylic diimide (PDI) was investigated experimentally and theoretically by using X-ray diffraction with combined DFT computation and molecular dynamics simulation. The structure was found to be hexagonal with a packing parameter of nearest column a = 2.025 nm characterized by a ~ 45° twist of molecules within the columns.
format Article
author Pokropivny, A.
author_facet Pokropivny, A.
author_sort Pokropivny, A.
title Supramolecular organization and electronic structure of perylene tetracarboxylic diimide: X-ray diffraction and theoretical studies
title_short Supramolecular organization and electronic structure of perylene tetracarboxylic diimide: X-ray diffraction and theoretical studies
title_full Supramolecular organization and electronic structure of perylene tetracarboxylic diimide: X-ray diffraction and theoretical studies
title_fullStr Supramolecular organization and electronic structure of perylene tetracarboxylic diimide: X-ray diffraction and theoretical studies
title_full_unstemmed Supramolecular organization and electronic structure of perylene tetracarboxylic diimide: X-ray diffraction and theoretical studies
title_sort supramolecular organization and electronic structure of perylene tetracarboxylic diimide: x-ray diffraction and theoretical studies
publisher Інститут проблем матеріалознавства ім. І.М. Францевича НАН України
publishDate 2010
topic_facet Методы исследования наноструктур и наноматериалов
url http://dspace.nbuv.gov.ua/handle/123456789/62702
citation_txt Supramolecular organization and electronic structure of perylene tetracarboxylic diimide: X-ray diffraction and theoretical studies / A. Pokropivny // Наноструктурное материаловедение. — 2010. — № 1. — С. 53-58. — Бібліогр.: 20 назв. — англ.
series Наноструктурное материаловедение
work_keys_str_mv AT pokropivnya supramolecularorganizationandelectronicstructureofperylenetetracarboxylicdiimidexraydiffractionandtheoreticalstudies
first_indexed 2025-07-05T13:34:35Z
last_indexed 2025-07-05T13:34:35Z
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fulltext Íàíîñòðóêòóðíîå ìàòåðèàëîâåäåíèå, 2010, ¹ 1 ÓÄÊ 541.183.24:576.8 A. Pokropivny Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine 03142, Ukraine, Kiev, Krzhuzhanovsky str., 3 SUPRAMOLECULAR ORGANIZATION AND ELECTRONIC STRUCTURE OF PERYLENE TETRACARBOXYLIC DIIMIDE: X-RAY DIFFRACTION AND THEORETICAL STUDIES The inter- and intracolumnar arrangements of the perylene tetracarboxylic diimide (PDI) was investigated experimentally and theoretically by using X-ray diffraction with combined DFT computation and molecular dynamics simulation. The structure was found to be hexagonal with a packing parameter of nearest column a = 2.025 nm characterized by a ~ 45° twist of molecules within the columns. In the last years the self-assembly of organic molecules presented the perspectives of developing novel materials for electronics. A special attention was made on the mesophases, characterized by p-conjugated molecules and formation of columnar superstructures in both the solid and liquid crystalline states. The arrangement of the molecules allows a charge carrier transport along the one-dimensional structures by increasing of coupling of p-electrons, which make them unique materials for device applications, such as field-effect transistors and solar cells. The perspectives of such materials became clear taking into account the anisotropy of electronic properties, low-cost and facile device fabrication, self-healing of defects within the columns, and relatively high local one- dimensional charge carrier mobility [1]. Most of the alkyl substituted low molecular weight species which organize into columnar superstructures are p-type semiconductors. Rylene diimide molecules, such as perylene tetracarboxylic diimide (PDI), terrylene tetracarboxylic diimide (TDI) and quaterrylene tetracarboxylic diimide (QDI) form a unique class of n-type organic semiconductors [2]. Both n-and p-types molecules can be used separately in field-effect transistors, while only their mixture are required in bulk-heterojunction photovoltaics, like hexabenzocoronene (HBC)-PDI and polycarbazolA. POKROPIVNY, 2010© ÌÅÒÎÄÛ ÈÑÑËÅÄÎÂÀÍÈß ÍÀÍÎÑÒÐÓÊÒÓÐ È ÍÀÍÎÌÀÒÅÐÈÀËΠKey words: liquid crystals, X-ray diffraction, non-covalent interac- tions, electronic properties, molecu- lar dynamics, quantum-chemistry calculation 54 Íàíîñòðóêòóðíîå ìàòåðèàëîâåäåíèå, 2010, ¹ 1 (CPz)-PDI, revealed the highest efficiencies for columnar phases [3]. PDI derivatives are used to control the molecular deposition [4], as an injector of charge carriers for different polymers employing the time-of-flight technique [5], and as fluorescence switch [6]. Furthermore, perylene has been utilized as convenient precusor for a consequent synthesis of more complex molecules, such as terrylene derivatives [7], perylenebisimide and bisbenzi- midazole [8], fullerene-perylene and perylenebi- simide-triphenyldiamine dyads [9]. These sub- stances are widely used for optoelectronic appli- cations [5–10] owing to their dyes cover the visible light [11] and due to their high thermal and photostability [12]. Nevertheless, the supramolecular structure into which PDI self-assemblies is not yet fully understand. An intracolumnar arrangement was proposed with a twist of the adjacent molecules [11, 13], or without any twist [14]. A detailed knowledge about the supramolecular organisations is necessary for the calculation of the electronic properties, since the electron and hole transfers strongly depend on the molecular arrangement [15]. The aim of this communication is to determine the supramolecular structure of heptyloctyl sub- stituted PDI (1), namely inter- and intracolumnar arrangements by using both X-ray diffraction analysis and simulations. Molecular dynamics simulation (total 30 ns run) had been done at a pressure P = 0.1 MPa and a temperature T = 300 K by using usual OPLS force field. GROMACS [20] software was used. The equations of motion were integrated using Varlet’s algorithm with a time step of 2 fs. After constructing topology of single PDI molecule, a periodic box of 4x4x12 molecules with hexagonal arrangement of columns with a 45° twist within columns were created. DFT calculations (BH&H/6–31G(d) level of theory) were done for dimers constructed from optimized monomers at the fixed distance of 0.35 nm between molecular cores. Gaussian 03 and GAMESS software were used. The total energy and electronic spectra were calculated with for different rotational angles. 2D-WAXS experimental setup [1, 11] consisted of a rotating anode (Rigaku 18 kW) X-ray beam with a pinhole collimation and a 2D Siemens detector, that use a double graphite monochromator for the Cu-Ka radiation (λ = 0.154 nm). The two-dimensional wide-angle X-ray scat- tering (2D-WAXS) pattern of a mechanically aligned PDI (1) is presented in Fig. 1. On the basis of two distinct equatorial reflections an orthorhombic intercolumnar arrangement was previously proposed with a unit cell of a = 1.67 nm and b = 2.08 nm. Later It is possible to consider the unit cell as a hexagonal lattice with a = 4.05 nm [11] leading to the assignment of the two equatorial reflections as (110) and (200). The intracolumnar packing is more complex and can be characterized by the meridional reflections. The major distinct (004) wide-angle meridional reflection is related to the π-stacking period of 0.345 nm, as shown in Fig. 1. The molecular cores arrange orthogonally with respect to the columnar axis. The appearance of additional (001) meridional reflections suggests a further intracolumnar correlation. Taking into account the π-stacking distance in relation with the high order distance of 1.39 nm, it is derived that Fig. 1. The 2D-WAXS pattern of PDI (1) at a temperature T = 300 K. Two meridional (004) and (001) reflections correspond to 0.345 nm and 1.39 nm periodicities in a direction of the columnar axis. Inset highlights the two major (110) and (200) equatorial reflections of hexagonal intercolumnar arrangement of a = 4.05 nm (004) (001) (200) (110) ÌÅÒÎÄÛ ÈÑÑËÅÄÎÂÀÍÈß ÍÀÍÎÑÒÐÓÊÒÓÐ È ÍÀÍÎÌÀÒÅÐÈÀËΠ55 М АТ ЕР ИА ЛО ВЕ Д ЕН ИЕ Íàíîñòðóêòóðíîå ìàòåðèàëîâåäåíèå, 2010, ¹ 1 every fourth molecule within the column is in the same position and laterally rotated by 45° to each other, providing the excellent agreement with π-stacking distance of 1.39/4 = 0.3475 nm with a divergence average of less than 1%. The large hexagonal packing parameter of a = = 4.05 nm contradicts the theoretical size of the PDI (1) molecules, while orthorhombic one with a > b parameters disagrees with the possible 45° twist of molecules. In comparison, the more extended rylene molecules, i.e. TDI and QDI revealed even a smaller hexagonal lattice with a = 2.94 nm and a = 3.09 nm, respectively. It is reasonably to assume that the parameter of a = 4.05 nm involves every second column leading to a simple intercolumnar distance of 2.025 nm in the hexagonal unit cell. Indeed, such a non-usual distribution of reflections with absence Table 1. Experimental (WAXS) and simulation data for a PDI columnar phase at 300 K of the (100) reflection has been reported for discotic liquid crystals [16] and fullerene-like crystals [17]. In such a case PDI belongs to columnar liquid crystals with p6 mm symmetry, like other rylenes. In order to confirm the experimentally observed hexagonal packing of columns, molecular dynamics (MD) simulation was performed (see for details [18]). As a test, a single column of 12 molecules was simulated. During the simulation the column was tilted in the simulated box, already indicating rather a hexagonal than rectangular or orthorhombic Fig. 2. Calculated positional correlation functions: perpendicular (squares) and parallel (circles). Inset highlights the hexagonal columnar arrangement of a simulation box after 30 ns run 9 6 3 0 1 2 3 Distance (nm) (100) (110) (200) g 0 56 Íàíîñòðóêòóðíîå ìàòåðèàëîâåäåíèå, 2010, ¹ 1 columnar arrangement. MD simulations revealed a unit cell parameter of 1.98 nm and a π-stacking distance of 0.35 nm (Fig. 2 and Fig. 3a) which were in a good agreement with the experimental values, from above discussed X-ray diffraction analysis. The hexagonal structure was slightly disordered so that the (100) reflection entirely could not be visible. The packing of PDI molecules in the columns revealed strong dependence on the molecular rotational angle, see Fig. 3b. At the 0° angle, i.e. only translations without twist, appropriate branches of dimer tails were closely connected with each other. Thus, a rotation of tails and a tilting of molecules were expected in order to minimize a total energy within the columns as shown in Fig. 3c. The total energetic profiles for different dimers with D6h and D3h symmetries revealed that the global energy minimum was rather unpredictable [15]. Fig. 4 shows the dependence of the total energies for PDI (1) and hydrogen substituted PDI (2) dimers calculated with BH&H/6–31g(d) method without optimisation at the fixed intermolecular distance of 0.35 nm. This method was successfully tested for calculation of vdW interactions on benzenes and pyridines [19]. The results indicated that the global energy minima for PDI (2) dimer were disposed in the ~30° and ~150° rotational angle position. At the 90° there was also a local minimum (see Fig. 4) for both types of dimers. For PDI (1) dimer the evolution of the total energy was more complicated with non-symmetric dependence on the rotational angle. The absolute minimum of function equals to ~24°. The local minimum equaled to ~139° (see Fig. 4), corres- ponding to ~41° twist, in full agreement with experimental value. It was expected the helical arrangement of molecules on the values of both minima, i.e., the absolute minimum at ~24° also might be achieved during slow crystallization process. The helical stack of the single column is reproduced in Fig. 3a and Fig. 3b. Comparisons of the WAXS experimental data with the simulations are shown in the table 1. The comparison shows Fig. 3. The single column of simulated box after MD simulation (a). Molecular architecture of PDI (1) molecules in the stack (every molecule is rotated to its neighbour by 45° around the columnar axis as shown by arrows) (b). Geometry of dimer of PDI molecules (at 30°) during quantum-chemistry calculations (c) a b c + C + H + H + O Fig. 4. Evolution of a difference of the total energies of a dimer made of D2 symmetry PDI–C8,7 (1) (circles) and D2h symmetry PDI–H (2) (squares) when rotating one core along the stacking axis, as calculated at DFT (BH&H) level of theory 50 40 30 20 10 0 0 30 60 90 120 150 180 Rotation (degrees) Energy (kcal/mol) 1 2 ÌÅÒÎÄÛ ÈÑÑËÅÄÎÂÀÍÈß ÍÀÍÎÑÒÐÓÊÒÓÐ È ÍÀÍÎÌÀÒÅÐÈÀËΠ57 М АТ ЕР ИА ЛО ВЕ Д ЕН ИЕ Íàíîñòðóêòóðíîå ìàòåðèàëîâåäåíèå, 2010, ¹ 1 that simulations fully agreed with experimental data and the structure of PDI is determined. Fig. 5 shows the results of the HOMO and LUMO splittings calculations, which are the double from the intermolecular transfer integral (t). As clearly seen, the electronic structures of PDI derivatives strongly depends on the substitutions: the alkyl chain causes a change of geometry that leads to distortion of the electronic structure. In particular, the dependence of HOMO splitting of PDI (1) and LUMO splitting of PDI (2) are practically identical. The dependence of splittings on the angle is non-symmetric, according to slight twisting of molecular skeletons in order to balance the massive branches of opposite alkyl chains. The rate of electron hopping (k) depends on LUMO splitting as k~t2 [15]. Thus, PDI electron mobility equals to zero for the PDI (2) at the 45° expe- rimental twist angle, while the perylene derivative carrying the branched side chains reveals the relatively high t values of ~0.01 eV (Fig. 5). Thereby, substitution of branched tails has a strong influence on the charge carrier mobility as major factor, besides angle of twist, temperature and defects. The calculated value of t at ~25° angle is ~0.1 eV. Reorganisation energies for PDI equals to 0.18 eV and 0.20 eV for positive and negative polarons, respectively, which are very close to the HATNA energies of 0.1 1–0.2 eV. According to the Marcus formalism [15] the charge transfer rate and charge mobility for PDI at the absolute minimum position are expected to be comparable with that of HATNA derivatives, promising electron trans- porters. In summary, the molecular and supramolecular arrangement has been determined for columnar phase of a perylene derivative bearing branched alkyl substituents. Analysis of 2D-WAXS patterns clearly indicated a hexagonal arrangement of columns and a helical packing of the molecules within the columns, like other rylene mesophases. Molecular dynamics simulation confirmed the stability of the hexagonal intercolumnar structure with a packing parameter of ~2 nm and π-stacking distance of ~0.35 nm. The helical intracolumnar arrangement of molecules was also verified by the DFT calculations. The calculated optimal rotational angles were proved to be 24° and 41° with the last value been very close to the experimental value of 45°. The electronic spectra revealed an essential dependence from the nature of the tails: the substitutes (tails, rings etc.) must be taken into account during transfer integral and charge mobility calculations. Ìåæ- è âíóòðèêîëîíî÷íûå óïîðÿäî÷åíèÿ ïåðèëåíà áûëè èññëåäîâàíû ýêñïåðèìåíòàëüíî è òåîðåòè÷åñêè ïðè èñïîëü- çîâàíèè ðåíòãåíîâñêîé äèôðàêöèè ñ êîìáèíèðîâàííûìè âû÷èñëåíèÿìè ìåòîäàìè ôóíêöèîíàëà ïëîòíîñòè è ìîëå- êóëÿðíîé äèíàìèêè. Ñòðóêòóðà êðèñòàëëà îïðåäåëåíà êàê ãåêñàãîíàëüíàÿ ñ óïàêîâî÷íûì ïàðàìåòðîì ñàìîé áëèçêîé êîëîíêè a = 2,025 íì ñ õàðàêòåðíûì òâèñòîì ~ 45° ìîëåêóë â ïðåäåëàõ êîëîíîê. Êëþ÷åâûå ñëîâà: æèäêèå êðèñòàëëû, ðåíòãåíîâñêàÿ äè- ôðàêöèÿ, íåêîâàëåíòíûå âçàèìîäåéñòâèÿ, ýëåêòðîííûå ñâîéñòâà, ìîëåêóëÿðíàÿ äèíàìèêà, êâàíòîâî-õèìè÷åñêèå âû÷èñëåíèÿ ̳æ- ³ âíóòð³øíüîêîëîí÷àñò³ âïîðÿäêóâàííÿ ïåðèëåíó áóëî äîñë³äæåíî åêñïåðèìåíòàëüíî é òåîðåòè÷íî ïðè âèêîðèñ- òàíí³ ðåíòãåí³âñüêî¿ äèôðàêö³¿ ç êîìá³íîâàíèìè îá÷èñëåí- íÿìè ìåòîäàìè ôóíêö³îíàëó ãóñòèíè òà ìîëåêóëÿðíî¿ äèíà- ì³êè. Ñòðóêòóðó êðèñòàëà âèçíà÷åíî ÿê ãåêñàãîíàëüíó ç ïàêóâàëüíèì ïàðàìåòðîì íàéáëèæ÷î¿ êîëîíêè a = 2,025 íì ³ç õàðàêòåðíèì òâ³ñòîì ~ 45° ìîëåêóë ó ìåæàõ êîëîíîê. Êëþ÷îâ³ ñëîâà: ð³äê³ êðèñòàëè, ðåíòãåí³âñüêà äèôðàêö³ÿ, íåêîâàëåíòíi âçàºìî䳿, åëåêòðîíí³ âëàñòèâîñò³, ìîëåêó- ëÿðíà äèíàì³êà, êâàíòîâî-õ³ì³÷í³ îá÷èñëåííÿ Fig. 5. Evolution of the HOMO (squares) and LUMO (circles) splittings of PDI (1) (filled types) and PDI (2) (open types) dimers when rotating around the stacking axis 0,8 0,6 0,4 0,2 0 0 30 60 90 120 150 180 Rotation (degrees) Splitting (ev) 58 Íàíîñòðóêòóðíîå ìàòåðèàëîâåäåíèå, 2010, ¹ 1 1. A Zone-Casting Technique for Device Fabrication of Field-Effect Transistors Based on Discotic Hexa-peri- hexabenzocoronene / Pisula W., Menon A., Stepputat M. et al.// Adv. Mater. – 2005. – 17, N 6. – P. 684–689. 2. Evidence for n-type conduction in a perylene tetra- carboxylic diimide derivative / Horowitz G., Kouki F., Spearman P. et al. // Adv. Mater. – 1996. – 8, N 3. – P. 242–245. 3. 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