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    Electrochemical, photovoltaic and DFT studies on hybrid materials based on supramolecular self-assembly of a ditopic twisted perylene diimide with square-planar platinum(II)- and/or palladium(II)-2,2 ':6 ',2 ''-terpyridyl complex ions
    (Elsevier Sci Ltd, 2019) Buyukeksi, Sebile Isik; Orman, Efe Baturhan; Acar, Nursel; Altindal, Ahmet; Ozkaya, Ali Riza; Sengul, Abdurrahman
    A ditopic bridging ligand, N,N'-bis(pyridine)-1,6,7,12-tetrakis-(4-methoxyphenoxy)perylene diimide (1) was synthesized. Metallosupramolecular self-assembly of 1 with 2,2':6',2 ''-terpyridyl-platinum(II) and/or -palladium (II) complex ions afforded to new triads [(terpy)M(II)-(1)-M(II)(terpy)1(NO3)(4) where, M(II) = Pt(II) (2), and Pd (II) (3), respectively. These isolated triads 2 and 3 and also free ligand 1 were fully characterized by FT-IR, H-1 NMR, C-13 DEPT NMR, H-1-H-1 COSY NMR, MALDI TOF and HRMS (MALDI-TOF/TOF-MS) mass techniques and UV/Vis spectroscopy. DFT studies revealed that the molecular structure of 1 is highly distorted and deviated from the planarity by bulky methoxyphenyl groups at bay positions. The calculated HOMO and LUMO are located on the PDI core and phenyl groups, and the band gap was found to be 2.27, 2.23 and 2.24 eV in DMSO for 1, 2 and 3, respectively. The calculated UV/Vis spectra are in good agreement with those of experimental results. Electrochemical, in situ spectroelectrochemical and in situ electrocolorimetric measurements in solution suggested that redox processes of the compounds are accompanied by favourable electron transport properties with remarkably narrow HOMO-LUMO gaps and intense light absorption over the visible range. The association of usually reversible and fast electron transfer processes with the net colour changes in solution pointed out the applicability of the compounds as an electrochromic material. The electrochromic performance measurements with the films of the compounds on indium tin oxide glass provided additional support for their usability as a colour changing material in electrochromic devices. Surface morphologies of the films were characterized by scanning electron microscopy (SEM). The metal complexes of 1, especially the platinum(II) complex (2), behaved as a good neutral and cathodic colouring electrochromic material with fast response time, long-term stability, and long-term write erase efficiency. The photovoltaic performance of the compounds as electron acceptor material was investigated by varying their relative ratio in the bulk heterojunction solar cells. It was found that the photovoltaic conversion efficiency of the devices strongly depends on the blend ratio. The optimized performance for the devices was obtained with the P3HT:PDIs (weight ratio 1.0:1.5) blended films. For this blend ratio, the device showed a maximum conversion efficiency of 3.91%, 8.17% and 5.18% for 1, 2 and 3, respectively. The results obtained reveal that employing 2 as an acceptor material has great potential for the development of highly efficient nonfullerene bulk heterojunction photovoltaic devices.
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    A novel AB(3)-type trimeric zinc(II)-phthalocyanine as an electrochromic and optical limiting material
    (Royal Soc Chemistry, 2020) Buyukeksi, Sebile Isik; Karatay, Ahmet; Orman, Efe Baturhan; Selcuki, Nursel Acar; Ozkaya, Ali Riza; Salih, Bekir; Sengul, Abdurrahman
    Recent advances in the practical applications of metallophthalocyanines (MPcs) in different technological fields have stimulated us to design and synthesize a new asymmetric AB(3)-type trimeric zinc(II)-phthalocyanine (1). This bulky and high molecular weight compound was characterized by elemental analysis, H-1, C-13 DEPT, and H-1-H-1 NOESY NMR, HR MALDI-TOF mass spectrometry, UV-vis, and FT-IR (ATR) techniques. In-depth electrochemical studies show that 1 displays quasi-reversible three one-electron reductions and two one- or two-electron oxidation processes, rather than any redox processes including the transfer of three-electrons in one-step. Besides this, in situ spectroelectrochemical measurements suggest the good application potential of 1 as an electrochromic material in display technologies. A study of the nonlinear optical properties (NLOs) of 1 reveals that the poly(methylmethacrylate) (PMMA) composite film displays a much larger nonlinear absorption coefficient and a lower saturable absorption threshold for optical limiting when compared to the same Pc molecules in solution. Ultrafast transient absorption measurements reveal the intersystem crossing mechanism. Density functional theory (DFT) was used for the geometry optimizations and time dependent-DFT (TD-DFT) for HOMO/LUMO energies and electronic transitions for 1.
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    Spectroscopic, electrochemical and electrocolorimetric properties of novel 2-(2 '-pyridyl)-1H-benzimidazole appended bay-substituted perylene diimide triads
    (Elsevier Science Sa, 2019) Pekdemir, Fatih; Orman, Efe Baturhan; Selcuki, Nursel Acar; Ozkaya, Ali Riza; Salih, Bekir; Sengul, Abdurrahman
    In this study, four new perylene diimide (PDI) derivatives incorporating 2-(2'-pyridyl)-1H-benzimidazole (2PBI) chromophores at the imide positions, in which 1 bearing non-bay-substituted perylene core, and those having four substituents at 1,6,7,12-bay positions of the perylene core, namely 2 bearing electron-withdrawing chlorine atoms, 3 bearing electron-donating 4-methoxyphenoxy groups and 4 bearing non-electron-donating 4-tert-butylphenoxy groups, respectively were synthesized and fully characterized by FT-IR, H-1 NMR, C-13 NMR, MALDI-TOF mass spectrometry and UV/Vis spectroscopy. The thermal properties were measured by thermogravimetric analysis (TGA) which showed that the materials (1-4) are thermally very stable (T-d > 450 degrees C). DFT was performed for geometry optimizations, and TDDFT was used to compare the calculated and the experimental UV/Vis electronic spectra at the B3LYP/6-311 G(d) level. Detailed measurements were carried out by the use of electroanalytical, spectroscopic and colorimetric techniques in order to understand redox natures, color changes and optoelectronic characters of the novel compounds. These 2PBI-functionalized PDI triads showed reversible reduction processes, chemically stable reduced species and considerably low HOMO-LUMO band gaps, as the new worthy members of photoactive charge transport materials for optoelectronic and photovoltaic systems. In addition, with distinct color changes associated with their redox processes in the solution, these new triads displayed great capacity for application in electrochromic devices. The emission maxima of the compounds were found to be red shifted in the solid state.
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    Tetrahydroxyphthalocyanine as a potential nonlinear optical material
    (Elsevier, 2023) Buyukeksi, Sebile Isik; Orman, Efe Baturhan; Karatay, Ahmet; Selcuki, Nursel Acar; Ozkaya, Ali Riza; Elmali, Ayhan; Salih, Bekir
    We have synthesized a new zinc(II)-phthalocyanine (ZnPc) incorporating hydroxyl groups at the pe-ripheral positions. This new zinc(II)-tetra-hydroxyphthalocyanine ( 1 ) has been characterized by high -resolution MALDI TOF MS, UV-Vis, FT-IR (ATR), and 1 H-and 13C-NMR techniques, and further by the electrochemical measurements. DFT and TD-DFT computations were performed to model plausible struc-ture and also analyze the electronic structure and optical properties of 1 . The effects of the polarity and hydrogen bonding ability of the hydroxyl substituents on the peripheral positions of 1 on the optical and electrochemical properties are reported in this study. The redox behavior of 1 in dimethyl sulfoxide (DMSO) was determined by voltammetry and colorimetry supported in situ spectroelectrochemistry. The nonlinear absorption and optical limiting (OL) properties of 1 were measured in tetrahydrofuran (THF) by utilizing the open aperture Z-scan technique with nanosecond pulses at 532 nm. The sample demon-strated good reverse saturable absorption and OL behaviors. The ultrafast pump-probe experiments re-vealed the intersystem crossing (ISC) mechanism (triplet-triplet transition) and the nonlinear absorption mechanism of the compound. The results indicate that this new phthalocyanine ( 1 ) can be considered a potential candidate for low-power OL applications.(c) 2022 Elsevier B.V. All rights reserved.