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The Ability to Fine-Tune the Electronic Properties and OpenCircuit Voltage of Phenoxy-Boron Subphthalocyanines through Meta-Fluorination of the Axial Substituent Kathleen L. Sampson, David S Josey, Yiying Li, Jessica D Virdo, Zheng-Hong Lu, and Timothy P Bender J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.7b11157 • Publication Date (Web): 18 Dec 2017 Downloaded from http://pubs.acs.org on December 23, 2017

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The Journal of Physical Chemistry C is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

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The Journal of Physical Chemistry

The Ability to Fine-Tune the Electronic Properties and Open-Circuit Voltage of Phenoxy-Boron Subphthalocyanines through Meta-Fluorination of the Axial Substituent. Kathleen L. Sampson,† David S. Josey, † Yiying Li,§ Jessica D. Virdo,† Zheng-Hong Lu,§ and Timothy P. Bender†,§,‡,* * to whom correspondences should be addressed. E-mail: [email protected] †Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario, Canada M5S 3E5. §Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario, Canada M5S 3E4. ‡Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.

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Abstract Six different boron subphthalocyanines with fluorophenoxy axial substituents were synthesized to explore and fine-tune the HOMO and LUMO energy levels based on past observations of the unique levels of pentafluorophenoxy-boron subphthalocyanine (F5BsubPc). Electrochemistry reduction potentials, ionization energies from ultraviolet photoelectron spectroscopy (UPS) measurements, and energy levels calculated using semi-empirical methods reveal finely variable values between phenoxy-BsubPc (PhO-BsubPc), without any fluorine atoms, and F5BsubPc, with all five fluorines. There is no trend between the number of fluorines on the phenoxy group and the electronic properties, but there is an influence of meta fluorine(s) altering the redox potentials and ionization energy leading us to categorize the fluorophenoxy-BsubPcs into two “buckets”: with and without meta fluorines. We then applied the fluorophenoxy-BsubPcs as electron acceptors in planar heterojunction organic photovoltaic devices. The categorization of these “buckets” was confirmed by the fine change in open-circuit voltage between 1.15 V and 1.21 V, which is an exceptionally high value. This level of fine tuning of properties and device metrics is a unique handle enabled by the phenoxy axial substituent of BsubPcs. Introduction The energy level alignment of the organic semiconductor materials has an important role in converting light into electrical current within organic photovoltaic (OPV) devices.1 The dissociation of excitons (electron-hole pairs) generated within the active layer of an OPV is dependent on the energetic spacing of the highest occupied molecular orbital (HOMO) and

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lowest unoccupied molecular orbital (LUMO) of the electron-donating and electron-accepting materials, respectively.2-3 Therefore, the ability to fine-tune these energy levels is a potential handle to engineer efficient charge transfer and improve device performance. However, the ability to have a molecular fragment handle to fine-tune these properties is rare in organic electronic materials, especially for typical materials such as fullerene-based electron acceptors.1, 4 A member of a broader class of materials called phthalocyanines (Pcs), boron subphthalocyanine (BsubPc) is a small molecule, semiconducting material of interest for OPV applications. BsubPcs contain a boron center surrounded by three nitrogen-linked isoindoline groups, which form a unique bowl shape. We have proven experimentally that the physical properties of BsubPcs, such as maximum absorption wavelength,5 sublimation temperature,6 solubility,7-8 melting point,9 crystal structure,10 extinction coefficent,5 and electronic characteristics,11 can be altered through the functionalization of the axial position or substitution of the hydrogens in the periphery.12-14 This array of modifications is highly desirable compared to the inability to alter the electronic and optical properties of typical fullerene electron acceptors, which are limited to an open-circuit voltage (VOC) of below 1 V in OPVs.15 One such derivative of BsubPc, which has previously been explored, is pentafluorophenoxyBsubPc (F5BsubPc), which has a pentafluorophenoxy group in the axial position.12 F5BsubPc has previously been incorporated into organic light emitting diodes (OLEDs) and OPVs and has shown significant performance characteristics including strong orange electroluminescence and ambipolar functionality within an OPV.16-17

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While the phenoxy axial substituent is versatile in adjusting the properties of BsubPcs, we have only shown in theory that the HOMO and LUMO levels of a phenoxy-BsubPc can be engineered through the incorporation of functional groups into the phenoxy molecular fragment.12 In that same study, we outlined how the HOMO and LUMO energy levels are less sensitive to modification of the substituents on the axial phenoxy ligand than the same modifications around the periphery of the BsubPc molecular fragment. F5BsubPc was found to be an exception, whereby it did change the HOMO and LUMO energy levels of the BsubPc chromophore likely due to the five strong electron-withdrawing fluorines present on the phenoxy group. Compared to a representative phenoxy-BsubPc (PhO-BsubPc), the HOMO and LUMO energy levels of F5BsubPc were measured to be notably deeper by ~0.4 eV.12 Cnops, et al. has previously shown that variations in peripheral substitution of BsubPcs, when applied as electron acceptors, allowed the optimization of the donor-acceptor energy gap and overall device performance.1 Our group has shown fluorophenoxy axial substituents on silicon phthalocyanines, materials that are structurally similar to BsubPcs, enable their application as electron and hole-accepting materials. We have also determined that position and frequency of fluorine atoms on the phenoxy substituent enables further tuning of their properties and device performance relative to the fully fluorinated pentafluorophenoxy-silicon phthalocyanine, achieving a high VOC of 0.94 V.18 In this study, we were able to determine the root cause of the unique properties of F5BsubPc and demonstrate that the electronic properties could also be fine-tuned by systematically reducing the number of fluorine groups on the fluorophenoxy substituent from F5 (F5BsubPc) to F4 to F3 to F2 Page 4 of 48


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to F1 (Scheme 1) with the final point of comparison being PhO-BsubPc with no fluorine atoms present. This observed ease of energy level tuning of an electron acceptor material, compared to that of fullerene acceptors, is ideal for improving charge extraction and achieving high VOC in an OPV device. To achieve these conclusions, five additional fluorophenoxy-BsubPc (FnPhOBsubPc) compounds were synthesized; 3-fluorophenoxy-BsubPc (3F1PhO-BsubPc); 3,5difluorophenoxy-BsubPc

(35F2PhO-BsubPc);

2,4,6-trifluorophenoxy-BsubPc

(246F3PhO-

BsubPc); 3,4,5-trifluorophenoxy-BsubPc (345F3PhO-BsubPc); and 2,3,5,6-tetrafluorophenoxyBsubPc (2356F4PhO-BsubPc). Once synthesized, the compounds were characterized by solution absorption and emission spectra, quantum yield, solid-state arrangement through x-ray crystallography, cyclic voltammetry (CV), differential pulse voltammetry (DPV), semi-empirical modelling, ultraviolet photoelectron spectroscopy (UPS), and then incorporated as electronaccepting materials in planar heterojunction OPVs.

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Experimental Section Methods and Materials All of the solvents used were purchased from Caledon Laboratories Ltd. (Caledon, Ontario, Canada) and used as received, unless otherwise stated. Kauffman chromatography was performed using 50 – 200 µm standard basic alumina purchased from Caledon Laboratories Ltd. (Caledon, Ontario, Canada) and used as received. The train sublimation apparatus and Kauffman column techniques are previously described.16 Synthetic precursors, such as phenol, 3fluorophenol,

3,5-difluorophenol,

2,4,6-trifluorophenol,

3,4,5-trifluorophenol,

2,3,5,6-

tetrafluorophenol, and pentafluorophenol, were purchased from Sigma-Aldrich (Oakville, Ontario, Canada). High-pressure liquid chromatography (HPLC) was performed using a Waters 2695 separation module with a Waters 2998 photodiode array and a Waters 4.6 mm × 100 mm SunFire C18 3.5 µm column. HPLC grade acetonitrile and dimethylformamide were purchased from Caledon Laboratories Ltd. (Caledon, Ontario, Canada) and eluted at a rate of 0.6 mL⋅min-1 with a concentration of 80/20 acetonitrile/dimethylformamide. Single crystals suitable for x-ray diffraction were grown by sublimation, slow vapor diffusion of heptane into benzene, and slow evaporation of dichloromethane. All solution ultraviolet-visible (UV-vis) spectroscopy was executed using a Perkin-Elmer Lambda 25 in a PerkinElmer quarts cuvette with a 10 mm path length. All nuclear magnetic resonance (NMR) spectra were acquired from a Bruker Avance III 400 MHz system using deuterated chloroform (CDCl3) and referenced to an internal standard of 0.05 % TMS.

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Photoluminescence spectra were measured from a Perkin-Elmer LS 55. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were performed using a Bioanalytical Systems C3 electrochemical workstation. The working electrode was a 1 mm platinum disk, the counter electrode was a platinum wire, and the reference electrode was Ag/AgCl in 3M sodium chloride salt solution. Electrochemistry was done with 0.1 M tetrabutylammonium perchlorate (SigmaAldrich) electrolyte in anhydrous dichloromethane (Caledon Laboratories), a 30 minute nitrogen purge prior to experimentation, and decamethylferrocene (Sigma-Alrich) as an internal reference. The redox potential of decamethylferrocene has been previously determined to be -0.012 V for CV vs. Ag/AgCl and all potentials were corrected to this value.19 For DPV, all potentials were corrected to the maximum potential of decemethylferrocene, which was calculated to be -0.037 V vs. Ag/AgCl using the following equation: ‫ܧ‬௠௔௫ = ‫ܧ‬ଵൗ − ଶ

௱ா ଶ

where Emax is the maximum

potential, E½ is the known half-wave potential, and ∆E is the pulse amplitude.20 Samples were analyzed over a range of +1.6 V to -1.6V for CV at a scan rate of 100 mV/s for three cycles. For DPV, scan windows of +0.25 V to -1.6 V and -1.6 V to -0.25 V were used with a pulse amplitude of 0.05 V. Bromo-boronsubphthalocyanine (Br-BsubPc) Synthesis Br-BsubPc was prepared based on the method previously reported21 by modifying a published procedure by Potz, et al.22 Phenoxy-BsubPc (PhO-BsubPc) Synthesis

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A similar procedure was followed as described by Morse, et al.12 To a preheated 100 mL round bottom flask fitted with a condenser and under pressure of argon, Br-BsubPc (3.0 g, 6.31 mmol) was dissolved in 65 mL of chlorobenzene. After five minutes of stirring, five equivalents of phenol (3.0 g, 31.6 mmol) were added to the flask. The reaction was heated to 131 °C at reflux and left overnight. In the morning, the heating was stopped and allowed to cool to room temperature before removing the solvent by rotary evaporation. To purify the crude product, Kauffman chromatography was used with standard basic alumina and dichloromethane as the mobile solvent phase. The column yield was 1.972 g (48.0 % yield) with 96.70% purity determined by HPLC. The PhO-BsubPc was further purified by train sublimation at resulting in >99.9% purity and 66.7% yield. Florinated-Phenoxy-BsubPc Synthesis The synthetic procedure for all five fluorophenoxy-BsubPcs was adapted from a previously reported process for pentafluorophenoxy boron subphthalocyanine (F5BsubPc)

16

. In a 100 mL

round bottom flask fitted with a condenser, Br-BsubPc (3.0 g, 6.314 mmol) was dissolved in toluene (30 mL) under constant pressure of argon gas. To the vessel, three equivalents of the fluorinated-phenol were added and the mixture was refluxed at 111 °C for 4 h, while monitoring the completion of the reaction (absence of Br-BsubPc) by HPLC analysis. The reaction was then cooled to room temperature and the toluene was removed by rotary evaporation. The crude product was subsequently purified using Kauffman column chromatography with standard basic alumina and dichloromethane as the mobile phase in order to remove the excess fluorophenol. The solvent was removed by rotary evaporation and yielded the crude product with purity Page 8 of 48


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determined by HPLC analysis. Further purification of the product was carried out by train sublimation. The apparatus was operated under vacuum with an internal pressure of 1 × 10-1 Torr from the flow of carbon dioxide gas. The temperature was increased from room temperature to 150 °C and held there for an hour to remove low subliming impurities. The sublimation temperature was then increased over 30 min to the sublimation temperature for each compound and left overnight. The next morning, the apparatus was cooled back to room temperature and the middle metallic gold band film was confirmed to be the fluorophenoxy-BsubPc by HPLC analysis. 3F1PhO-BsubPc Amount of 3-fluorophenol added to the reaction vessel: 2.8 mL, 30.9 mmol. Crude product after Kauffman column: 1.576 g, 3.11 mmol, 94% purity. Sublimation yield: 0.098 g, 0.194 mmol, 27.2 % yield, 99% purity. 1H NMR (400 MHz, CDCl3, Me4Si): δ 5.11 – 5.14 (1H, m), 5.16 (1H, ddd), 6.32 (1H, tdd), 6.69 (1H, td), 7.86 – 7.99 (6H, m), 8.81 – 8.92 (6H, m) (Figure S1). MS (EI) exact mass calculated for C30H16BFN6O: m/z 506.1463, found 506.1466. 35F2PhO-BsubPc Amount of 3,5-difluorophenol added to reaction vessel: 4.192 g, 32.2 mmol. Crude product after Kauffman column: 2.206 g, 4.21 mmol, 98% purity. Sublimation yield: 0.179 g, 3.41 mmol, 40.1% yield, >99% purity. 1H NMR (400 MHz, CDCl3, Me4Si): δ 4.87 – 4.97 (2H, m), 6.07 (1H, tt), 7.88 – 7.98 (6H, m), 8.82 – 8.92 (6H, m) (Figure S2). MS (EI) exact mass calculated for C30H15BF2N6O: m/z 524.1368, found 524.1368. Page 9 of 48



246F3PhO-BsubPc Amount of 2,4,6-trifluorophenol added to reaction vessel: 4.680 g, 31.6 mmol. Crude product after Kauffman column: 1.634g, 3.01 mmol, 92% purity. Sublimation yield: 0.305 g, 5.62 mmol, 66.9% yield, >99.9% purity. 1H NMR (400 MHz, CDCl3, Me4Si): δ 6.09 – 6.20 (2H, m), 7.87 – 7.97 (6H, m), 8.81 – 8.91 (6H, m) (Figure S3). MS (EI) exact mass calculated for C30H14BF3N6O: m/z 542.1274, found 542.1277. 345F3PhO-BsubPc Amount of 3,4,5-trifluorophenol added to reaction vessel: 4.692 g, 31.7 mmol. Crude product after Kauffman column: 1.583g, 2.92 mmol, 95% purity. Sublimation yield: 0.225 g, 4.15 mmol, 58.6% yield, >99% purity. 1H NMR (400 MHz, CDCl3, Me4Si): δ 5.02 (2H, ddt), 7.98 – 7.88 (6H, m), 8.92 – 8.82 (6H, m) (Figure S4). MS (EI) exact mass calculated for C30H14BF3N6O: m/z 542.1274, found 542.1274. 2356F4PhO-BsubPc Amount of 2,3,5,6-tetrafluorophenol added to reaction vessel: 5.375 g, 32.4 mmol. Crude product after Kauffman column: 1.963g, 3.50 mmol, 99% purity. Sublimation yield: 0.338 g, 6.03 mmol, 76.8% yield, >99.9% yield. 1H NMR (400 MHz, CDCl3, Me4Si): δ 6.35 (1H, tt), 7.88 – 7.98 (6H, m), 8.82 – 8.92 (6H, m) (Figure S5). MS (EI) exact mass calculated for C30H13BF4N6O: m/z 560.1180, found 5560.1183. F5BsubPc Page 10 of 48


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Previously synthesized according to method reported by Morse 16. Semi-empirical Methods All compounds were modelled in HyperChem version 8.0 for Windows OS. Optimization using the MM+ molecular mechanics force field was performed first followed by further refining using either RM1 or PM3 semi-empirical methods. Molecular mechanics and semi-empirical methods geometric optimization was performed using the Polak-Ribiere conjugated gradient algorithm with a 0.02 kcal/Å·mol-1 root-mean-squared convergence limit. The semi-empirical RM1 and PM3 files were modified as per our previously published experimentally verified BsubPc model by Morse, et al.12 Device Fabrication The OPV fabrication and characterization in this study followed previously described methods.2325

Briefly, the devices were fabricated on pre-patterned, ITO-coated glass substrates (Figure S6).

The substrates were cleaned using sonication in a detergent solution and solvents, followed by an atmospheric plasma treatment. After cleaning, the substrates were spin-coated with PEDOT:PSS and baked on a hot plate at 110 °C for at least 10 min. The substrates were then removed from atmospheric conditions for the remainder of fabrication and characterization by transferring to a nitrogen atmosphere glovebox attached to a custom vacuum deposition chamber. All subsequent organic layers were deposited at ~1.0 Å/s and a working pressure of ~1 x 10-7 torr. Silver electrodes were deposited at 1.0 Å/s

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and a working pressure of ~1 x 10-6 torr through a shadow mask, defining an active area of 0.2 cm2.

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Results and Discussion Synthesis of Fluorophenoxy-BsubPc Compounds For this study, five fluorophenoxy-BsubPcs (FnPhO-BsubPcs) were synthesized in addition to phenoxy-BsubPc (non-substituted PhO-BsubPc) and pentafluorophenoxy-BsubPc (pentasubstituted, F5-BsubPc): 3-fluorophenoxy-BsubPc (mono-substituted, 3F1PhO-BsubPc); 3,5difluorophenoxy-BsubPc (di-substituted, 35F2PhO-BsubPc); 2,4,6-trifluorophenoxy-BsubPc (trisubstituted, 246F3PhO-BsubPc); 3,4,5-trifluorophenoxy-BsubPc (tri-substituted, 345F3PhOBsubPc); and 2,3,5,6-tetrafluorophenoxy-BsubPc (tetra-substituted, 2356F4PhO-BsubPc). The synthesis of all fluorophenoxy-BsubPc compounds was achieved by reacting Br-BsubPc with three molar equivalents of the respective fluorophenol in toluene under reflux (Scheme 1). The mechanism of this reaction has been established.26 We have previously shown that Br-BsubPc has a high phenoxylation reaction rate, achieving completion in only a few hours, and is, therefore, an ideal precursor for efficient synthesis of phenoxy-BsubPc derivatives.9 All FnPhOBsubPcs were purified by train sublimation prior to characterization and device fabrication.

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Scheme 1. Synthesis of the array of fluorophenoxy-BsubPcs from Br-BsubPc and the respective fluorophenol. Conditions (i) three equivalents of fluorophenol to Br-BsubPc in toluene and refluxed at 111 °C for 4 hours.

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Spectroscopy Analysis The UV-vis absorption and photoluminescence spectra of each fluorophenoxy-BsubPc compound were measured in toluene solution (Figure 1). All flurophenoxy-BsubPc compounds were found to have very similar absorption spectra, which is typical of BsubPcs and directly comparable to F5BsubPc. This confirmed that the axial phenoxy substituent has no influence on the band gap nor basic photophysics of the BsubPc chromophore. The maximum absorptions for the fluorophenoxy-BsubPcs occur between 562 and 564 nm (within experimental error, Table 1). The spectra also have distinct shoulders at 547 nm. The varying position and quantity of fluorines on the axial phenoxy molecular fragment does, however, affect the UV region where differences in extinction coefficients can be seen. Photoluminescence spectra were also measured in toluene solution by excitation at 540 nm, slightly lower in wavelength than the maximum absorbance. The fluorophenoxy-BsubPc compounds, again, had emission spectra of similar size and shape to that of other BsubPcs, and F5BsubPc in particular (Figure 1). The maximum photoluminescence peak emissions had minimal variations, ranging from 569 nm to 573 nm (Table 1). Each compound also had an emission shoulder at around 615 nm, mirroring the absorption spectrum. Much like the UV-Vis absorption spectra, the different fluorination has little effect on the emission spectra, which is consistent with previous observations.27 Stokes shifts are also similar and only range from 6 to 9 nm (Table 1).

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Figure 1. Overlaid UV-vis absorption (solid line) and photoluminescence spectra (dotted line) of PhO-BsubPc (grey), 3F1PhO-BsubPc (red), 35F2PhO-BsubPc (blue), 246F3PhO-BsubPc (green), 345F3PhO-BsubPc (purple), 2356F4PhO-BsubPc (orange), and F5BsubPc (pink).

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Table 1. Maximum UV-vis absorption, fluorescence, Stokes shift, and quantum yield

Fluorophenoxy-

Maximum

Maximum

Stokes Shifts

Quantum

BsubPc

Absorption

Fluorescence

(nm)

Yield

Wavelength

Wavelength

(nm)

(nm)

PhO-BsubPc

562

570

8

0.47

3F1PhO-BsubPc

563

569

6

0.42

35F2PhO-BsubPc

564

573

9

0.38

246F3PhO-BsubPc

563

572

9

0.46

345F3PhO-BsubPc

564

570

6

0.41

2356F4PhO-BsubPc

563

570

7

0.44

F5BsubPc

564

573

9

0.42

measurements for the array of fluorophenoxy-BsubPc compounds.

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Fluorescence quantum yield measurements for each fluorophenoxy-BsubPc were measured at room temperature in toluene solutions relative to the previously determined standard F5BsubPc (0.42).16 The quantum yields of each material are similar to F5BsubPc (Table 1) and range from 0.38 (35F2PhO-BsubPc) to 0.47 (PhO-BsubPc). Although the quantum yields are very similar, it is notable that the BsubPcs with the lowest measured quantum yield have fluorines only in the meta position(s) on the phenoxy group, while the two highest measured quantum yield values correspond to the BsubPcs with fluorines only in the para and ortho position(s). Solid-State Arrangement Analysis How the molecules arrange in the solid-state is relevant to the formation of thin films and transfer of charge within an organic electronic device. Therefore, the crystal structure of each fluorophenoxy-BsubPc was examined by growing crystals suitable for X-ray diffraction. For the fluorophenoxy-BsubPcs (3F1PhO-BsubPc, 35F2PhO-BsubPc, 246F3PhO-BsubPc, 345F3PhOBsubPc, 2356F4PhO-BsubPc), we focused mainly on crystals formed by train sublimation as this would likely be the most representative arrangement of the vacuum deposited films in devices (description of crystal structures from other methods are described in the Supporting Information and Figure S7). PhO-BsubPc crystals grown by vapor diffusion and F5BsubPc crystals grown by vapor diffusion (α-F5BsubPc) and sublimation (β-F5BsubPc) have been previously reported by Paton, et al., Morse, et al., and Castrucci, et al.16, 28-29 There are two general descriptions of BsubPc solid-state interactions: one details the interactions of the bowl shapes with one another and the other describes the arrangement of the isodindoline

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groups between neighboring BsubPcs. If one considers the axial ligand face of the bowl shape to be convex and the opposite side to be concave, the bowls can interact in three ways: concaveconcave, convex-concave, and convex-convex. For the placement of the isoindoline groups, the peripheral aromatic group is regarded as the head and the imine nitrogen side of the BsubPc is referred to as the tail. BsubPcs generally align head-to-tail, head-to-head, and concave-to-ligand. These classifications have been previously developed by Morse, et al. and pictorially described by Claessens, et al.14, 16 The solid-state arrangements of BsubPcs can be characterized by the π-π interaction distances between adjacent BsubPcs in these types of interactions. The typical geometry of these types of interactions in the fluorophenoxy-BsubPcs is depicted in Figure 2 and the corresponding distances are described in Table 2.

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The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Figure 2. The three general solid-state interactions of adjacent fluorophenoxy-BsubPcs in terms of the relative arrangement of the bowls (concave-concave, convex-convex, and concave-ligand) and the position of the isoidoline groups (highlighted in yellow: headto-head, convex-convex, and concave-to-ligand). The short π-π centroid contacts of each packing type are labelled with A through H.

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Table 2. Space group, unit cell dimensions, hydrogen-to-fluorine bond distance, and shortest π-π interaction distances (A – H) between adjacent fluorophenoxy-BsubPcs in their respective solid-state arrangements (described in Figure 2).

FnPhOBsubPc

CCDC#

Space Group

PhOBsubPcc, f

783165

P1

3F1PhOBsubPca

1584840

P1

35F2PhOBsubPca

158438

P1

35F2PhOBsubPcb

1584835

P1

246F3PhOBsubPca, b, c

1584836

C2/c

345F3PhOBsubPca

1584837

P1

2356F4PhOBsubPca

1584839

P21/c

β-F5BsubPca,

878101

P21/c

α-F5BsubPcc,

824388

C2/c

g

h

a b c (Å) 10.04920 10.75030 11.83420 12.6225(5) 13.5539(5) 15.1187(5) 12.4735(3) 13.5131(3) 15.4024(4) 10.644(2) 11.493(2) 11.574(2) 19.625(5) 10.083(2) 23.329(19) 8.1252(3) 11.3487(5) 13.6884(6) 9.967(2) 21.088(4) 11.827(2) 14.2834(6) 11.3575(2) 15.1707(7) 19.7225(4) 10.3637(3)

α β γ (°) 85.8930 77.4510 66.0430 95.231(2) 107.955(2) 100.509(2) 101.669(1) 107.457(1) 93.076(1) 92.380(4) 105.001(4) 105.023(4) 90 92.862(5) 90 89.312(2) 76.945(2) 79.112(2) 90 107.068(5) 90 90 99.7330(15) 90 90 93.3870(15)

Distance A (Å)

Distance B (Å)

Distance C (Å)

Distance D (Å)

Distance E (Å)

Distance F (Å)

H···F Bond Distance (Å)

3.674

4.110

-

-

-

-

-

3.6405(8) 3.7410(8)

4.1765(8) 4.3024(8)

-

-

-

-

-

3.6344(8)d 3.6506(8)e

4.1672(8)d 4.2676(8)e

-

-

-

-

2.539

3.7069(11)

4.4851(12)

-

-

-

-

2.461

3.54012(12)

4.2127(13)

-

-

-

-

2.250

3.6334(8)

4.0469(9)

-

-

-

-

-

3.8495(12)

4.7505(13)

3.5260(12)

3.7225(13)

-

-

2.520 2.379

-

-

-

3.7873(14)

3.9655(14)

-

4.0825(9)

-

-

-

-

2.542 2.532

-

3.5182(10)

Page 21 of 48


The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

23.4591(6)

Page 22 of 57

90

2.462

a

Crystals grown by sublimation, b Crystals grown by slow evaporation of dichloromethane, c Crystals grown by slow vapor diffusion,

d

Interactions between BsubPc in conformation 1, e Interactions between BsubPcs in confirmation 1 and 2, f Previously reported by

Paton,

et

al.29

g

Previously

reported

by

Castrucci,

et

al.28

Page 22 of 48


h

Previously

reported

by

Morse,

et

al.16

Page 23 of 57 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


All fluorophenoxy-BsubPc compounds, except for β-F5BsubPc, display the most typical BsubPc interaction: concave-concave, head to head.14 Distances A, C, and E describe the π-π interaction distances, while distances B, D, and F describe the degree of isoindoline group overlap. In this arrangement, the π-π interactions of the fluorophenoxy-BsubPc compounds varies from 3.54 to 3.85 Å with the smallest distance in 246F3PhO-BsuPc and the largest distance in 2356F4PhOBsubPc. The degree of overlapping isoindoline groups between the fluorophenoxy-BsubPc compounds varies as well from 4.05 to 4.67 Å. In contrast, single crystals of F5BsubPc made by sublimation (previously denoted β-F5BsubPc) do not have overlapping isoindoline groups, but have concave-to-ligand interactions.28 The pentafluorophenoxy axial ligand interacts closely with one isoindoline group on a neighboring BsubPc with a distance of 3.79 Å to the peripheral benzene (Figure 2, distance E). In addition, the π-π interactions continue from one molecule to the next and form ribbon-like structures in the solid-state arrangements of 345F3PhO-BsubPc and 2345F4PhO-BsubPc, as depicted in Figure S8 of the Supporting Information. 246F3PhO-BsubPc, 2356F4PhO-BsubPc, α-F5BsubPc, and β-F5BsubPc crystallized in a different space group (P21/c or C2/c) than the P1 space group of PhO-BsubPc (Table 2). The change in space group is likely due to the presence of weak hydrogen-fluorine bonds. Half of the fluorophenoxy-BsubPc crystal structures, excluding 3F1PhO-BsubPc, 345F3PhO-BsubPc and βF5BsubPc, exhibit hydrogen-fluorine bonds between the fluorines on the phenoxy group and hydrogens on neighboring BsubPcs (Figure 3). It has been demonstrated that defining weak hydrogen bonds as less than the sum of the van der Waals radii (

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