Diphenanthrioctaphyrin(1.1.1.0.1.1.1.0): Conformational Switching

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Diphenanthrioctaphyrin(1.1.1.0.1.1.1.0): Conformational Switching Controls the Stereochemical Dynamics of the Topologically Chiral System Bartosz Szyszko, Piotr J. Chmielewski, Monika Przewoznik, Micha# J Bia#ek, Kamil Kupietz, Agata Bialonska, and Lechoslaw Latos-Grazynski J. Am. Chem. Soc., Just Accepted Manuscript • Publication Date (Web): 21 Mar 2019 Downloaded from http://pubs.acs.org on March 21, 2019

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Journal of the American Chemical Society

Diphenanthrioctaphyrin(1.1.1.0.1.1.1.0): Conformational Switching Controls the Stereochemical Dynamics of the Topologically Chiral System Bartosz Szyszko,* Piotr J. Chmielewski, Monika Przewoźnik, Michał J. Białek, Kamil Kupietz, Agata Białońska, and Lechosław Latos-Grażyński*

Department of Chemistry, University of Wrocław, 14 F. Joliot-Curie St., 50-383 Wrocław, Poland ABSTRACT: The analogue of octaphyrin(1.1.1.0.1.1.1.0) bearing two dimethoxyphenanthrene units was synthesized and characterized in solution and solid state. The macrocycle was demonstrated to exist as two locked conformers that can be easily separated and handled individually. The conversion of conformers was proven to be facilitated by the presence of hydrogen bond acceptors, such as amines. Bis-boron(III) complex of diphenanthrioctaphyrin has been obtained proving that the metalloid center acts as the topology selector stabilizing only one conformation of the macrocycle, irrespectively of the stereoisomer used for the insertion. Both conformers of diphenanthrioctaphyrin, as well as the boron complex formed from them, have been separated into enantiomers using HPLC on chiral stationary phase. All of these systems have shown strikingly different stereodynamic behavior.

INTRODUCTION Expanded porphyrins1–3 are considered as the most diverse group of porphyrinoids in terms of conformation, molecular dynamics4 and aromaticity.5–11 They were proven to act as unusual ligands for metals and metalloids cations,12,13 effective receptors,5,14 as well as molecular switches able to accommodate multiple topologies resulting in Hückel and Möbius aromaticity and antiaromaticity.8,15–24 Among expanded porphyrins, the octaphyrin family25–32 has drawn particular interest due to their nontrivial coordination chemistry,33–40 including metal-mediated mitosis reactions yielding metalloporphyrins,41,42 anions binding,43,44 proton-coupled electron transfer (PCET) reactions,45 and Baird-type aromaticity.46 Many octaphyrins were demonstrated to adopt non-planar, dynamic figure-of-eight conformations that can be effectively modulated through redox reactions,47 protonation,48,49 or deprotonation.50 Much interest was devoted to chirality of figure-of-eight octaphyrins51–54 that, in some cases, can work as macrocyclic chirality sensors.55 Despite impressive number of reported expanded porphyrins and heteroporphyrins, the group of their carbaanalogues56 is still rather modest even though the last couple of years provided new and exciting expanded carbaporphyrinoid systems18,21,57–69 including heptaphyrin containing dithienothiophene unit,70,71 mbenzihexaphyrins,72 doubly N-fused expanded di-mbenziporphyrinoids,32 di-m-benzidecaphyrins,73 expanded azuli- and benzocarbaporphyrins.74 In the last several years we have been developing the carbaporphyrin subgroup with polycyclic aromatic hydrocarbon moieties embedded, namely aceneporphyrinoids or, in broader terms, Polycyclic Aromatic Hydrocarbonporphyrins (PAH-porphyrins).75 This group is, till now, represented by 1,3-naphthiporphyrins,76,77 1,4-

naphthiporphyrins,76,78 helical hetero-1,5-naphthiporphyrins,79 meso-fused thianaphthiporphyrin,80 9,10-anthriporphyrins,81,82 meso-fused thiaanthriporphyrin,83 and pyreniporphyrin.75 Closely related to aceneporphyrinoids are phenanthriporphyrinoids, however, the phenanthrene moiety incorporated into the macrocyclic core, should be described as phenacene-like rather than acene-type hydrocarbon. Starting from our first report on phenanthritetraphyrin(1.1.1.0) (phenanthriporphyrin or phenanthricorrole) 1,84 85 dioxophenanthritetraphyrin(1.1.1.0) 2, and their phosphorous 1-P and copper(III) complexes 1-Cu, and 2-Cu86 we have been systematically expanding the macrocyclic framework of 1 by formal incorporation of consecutive (E)‐2‐benzylidene‐2H‐pyrrole units which led to heterophenanthripentaphyrins(1.1.1.1.0) (32-heterosapphyrins) 3-X,87 and helicenophyrins 4, and 588 obtained in the attempted phenanthrihexaphyrin(1.1.1.1.1.0) synthesis (Chart 1). Independently to our studies, the structurally resembling phenanthriporphyrinoids macrocycles bearing dibenzo[g,p]chrysene moiety were developed by the Sessler group, namely fused bis-dicarbacorrole 6 forming mixed Cu(III)-Pd(II) [6-Cu/Pd]• complex89 with stable organic radical character and bis-Pd(II) complex system 6-Pd2, where the hydrocarbon part of the ligand presents quinoidal nature.90 Very recent exemplification of this group is the remarkable, conjugated carbaporphyrin cage 7.91 Chart 1. Phenanthriporphyrinoids and related macrocycles.

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Journal of the American Chemical Society MeO

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OMe

O

O

MeO

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MeO

OMe

F

OMe

F F

OHC Ph

Ph

M N

Ph

N

Ph

M N

Ph

MeO

OMe MeO PNP

PNP N H N PNP

HN Ph

N N

Ph

N

30

Ph

N

O

H

27

O

Mes

26

N

6-Pd2 Mes

Mes

NH C6F5 C6F5

H N N H

Mes Mes

NH

H N N H

J 54 N

40 42

Ph

2 3

A

46

49

N 48 E

21 19

N

Ph Ph

Ar

11

D 14

Ph

C

6

O

8 9

13

N

9-1

Ar

HN

NH

Ph

Ph OMe MeO MeO OMe

Herein we report on new expanded carbaporphyrin – diphenanthrioctaphyrin(1.1.1.0.1.1.1.0) that in its free base form exists as two locked conformers that can be readily isolated by column chromatography and handled separately. Although their properties clearly differ, including strikingly diverse stereodynamic behavior, the macrocycles are interconvertible in presence of hydrogen bond acceptors. Surprisingly, even though the stereoisomers are in the thermodynamic equilibrium under boron(III) insertion conditions, they both produce a single bis-boron(III) complex, stabilizing preferentially only one geometry. RESULTS AND DISCUSSION Synthesis. Following our pursuit of expanded phenanthriporphyrinoids, aiming for diphenanthrioctaphyrin 9, two components condensations of phenanthritripyrrane 8 with activated aromatic aldehydes (pentafluorobenzaldehyde and 4-nitrobenzaldehyde) were conducted under Lindsey-type conditions (Scheme 1). The intermediate products, formed in the first step of the reaction, were oxidized without isolation, using DDQ (2,3-dichloro-5,6dicyano-1,4-benzoquinone). In the process of chromatographic purification of the crude reaction mixture two fractions, distinctively differing in their polarity and colors, were collected. Surprisingly, the high resolution mass spectra recorded for the samples of both fractions showed the same m/z ratio corresponding, for both sets of substituents, to [M+H]+ molecular ions of diphenanthrioctaphyrins (1.1.1.0.1.1.1.0) 9a,b. Scheme 1. Synthesis of 9a and 9b.

16

Ph

HN

Ph

Mes

O

Ar

N

NH

7

18

H

47 N

Ar

Ar

C6F5 C6F5

5

9a, Ar = perfluorophenyl, 13% 9b, Ar = p-nitrophenyl, 6%

Mes

6, M1 = M2 = 3H 6-Cu, M1 = 3H, M2 = CuIII 6-Cu2, M1 = M2 = CuIII [6-Cu/Pd]., M1 = CuIII, M2 = PdII

HN

Mes

F

Ph

HN Mes Mes

39

43

N Mes

Mes

Mes

37

B

C6F5

M2

N

N

Ar

35

I 53 N H

52

23

N M1

C6F5 C6F5

Pd

32

G

N

N Pd

Ph

29

24

C6F5

NO2

OHC

1. Et2O:BF3, CHCl3, 2 h 2. DDQ 34

HN

Mes

+

8

5, PNP = p-nitrophenyl

Mes

F or

NH HN

PNP Ph

4, PNP = p-nitrophenyl

F

Ph

OMe

N

PNP

Mes

Ph

X

Ar Ar 3-X, X = S, Se, Te

2, M = 3H 2-Cu, M = CuIII

PNP

N

N

Ph

1, M = 3H 1-Cu, M = CuIII 1-P, M = PV(OMe)2

+

Ph

Ph

N

MeO

N

Ph

Ph

OMe

MeO

OMe

9-2

In addition, both species presented very similar absorption patterns in their UV-vis spectra, as well as very alike, although non-identical, 1H NMR patterns. Eventually, we have realized that two isolated species are differently locked conformers 9-1 and 9-2 of diphenanthrioctaphyrin(1.1.1.0.1.1.1.0) (Scheme 1). Although several expanded porphyrins are known to exist in the solution as the equilibrium mixtures of different conformers,4 to our best knowledge only one example of separation and characterization of such stereoisomers of the expanded porphyrin was previously reported.92 9-1 and 9-2 were also demonstrated to form in course of the condensation of 8 with benzaldehyde but they were prone to decomposition during purification. After typical work-up and chromatographic separation 9a-1 (9b-1) and 9a-2 (9b-2) were isolated in 6% (2%) and 7% (4%) yields, respectively. Characterization. The first, light green fraction eluted during chromatography either on basic alumina or silica gel contained 9-1. The composition of 9a-1 was confirmed by high-resolution mass spectrometry which showed the molecular ion at m/z = 1445.4027 corresponding exactly to the calculated for [M+H]+ (C90H55F10N4O4+) value of 1445.4058 (Figure S98, SI). More polar, green-blue fraction isolated from the mixture contained the 9a-2 conformer. Expectedly, the HRMS spectrum indicated for the same composition with the molecular ion at m/z = 1445.4107 (Figure S100, SI). 9a-1 is well soluble in chlorinated solvents and forms vividly green solutions. Its UV-vis spectrum contains three intense bands at 255 (logƐ = 4.8), 374 (4.8) and 458 (4.6) nm, as well as lesser but broad absorption extending from 510 to 900 nm with maximum at 656 nm (4.3) (Figure 1). The replacement of two perfluorophenyl substituents at positions 16 and 37 in 9a-1 for p-nitrophenyl groups of 9b-1 manifested by marked blue shift (12 – 21 nm) of two, lowest energy bands. The other


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absorptions were affected to a much lesser extent (2 – 5 nm) (Figure S104, SI). Differently than for 9-1, the solubility of 9-2 in dichloromethane and chloroform is distinctively lower. Also, the green color of 9-2 solutions is slightly different with bluer tint. This reflects in the UV-vis spectrum of 9a-2 which presents three intense bands with maxima at 259 (sh. 295, logƐ = 4.9), 380 (5.0) and 647 nm (sh. 764, 4.6), and overlapping, weak bands at 446 (4.4) and 472 nm (4.4). For 9b-2 low energy bands were blue shifted by 8 and 26 nm, respectively, resembling the changes observed for 9a-1 (Figure S106, SI).

Figure 2. Top: crucial NOE contacts observed in the NOESY/ROESY spectra for protons of A) 9a-1, and B) 9a-2. Bottom: the 1H NMR spectra (DCM-d2, 600 MHz) of C) 9a-1 (220 K), and D) 9a-2 (200 K).

Figure 1. The UV-vis absorption spectra (DCM, 298 K) of 9a-1 (black), 9a-2 (red), and 9a-2-(BF2)2 (green).

Solution structures of 9-1 and 9-2. The number of corresponding signals, altogether with their chemical shifts, in the 9-1 and 9-2 1H NMR spectra suggested resemblance of two conformations adopted by diphenanthrioctaphyrin 9 (Figure 2). Detailed analysis of the set of 2D NMR experiments, supported by the extensive molecular modelling, allowed to propose two C2-symmetric figure-ofeight conformations as the starting point for further considerations. The recognition of the appropriate extensive systems of dipolar, through-space couplings in the NOESY (and ROESY) spectra of 9-1 and 9-2 (Figures 2, S1, SI) supported the compact, figure-of-eight conformations and allowed for ultimate determination of the molecular geometries. In terms of macrocyclic aromaticity no relevant shielding/deshielding effects have been observed in the spectra of 9-1 or 9-2, therefore they should be both treated as conjugated, nonaromatic [32]diphenanthrioctaphyrins. The 1H NMR chemical shifts have been calculated using the GIAOB3LYP method for the optimized models of 9a-1 and 9a-2 [ωB97XD/6-31G(d,p)]. Good qualitative agreement between calculated and experimental sets of chemical shifts has been obtained (Figures S136, S137, SI). The Nucleus Independent Chemical Shifts values (NICS) were calculated within two semi-pockets of the figure-of-eight macrocycles. They are equal –2.2 for 9a-1, and –2.0 for 9a-2, respectively, indicating negligible macrocyclic -conjugation in both conformers.

The most pronounced structural feature of the lemniscular conformer 9-1 is the position of two phenanthrenylene moieties located at the crossing of the figure-of-eight shape (Figure 2). This geometry enforces a network of strong dipolar couplings within two pockets of the macrocycle, which were found crucial for determination of the structure. It was recognized that NH(47)···H(43), NH(47)···H(46) and NH(47)···H(23) set of NOE cross peaks serves as the fingerprint of the 9-1 conformation (Figure 2, trace A, Figures S6, S14, SI). In addition, the relative placement of phenanthrene moieties one above the other resulted in an evident differentiation of the chemical shifts of H(2,23) and H(9,30) protons, whose signals are separated by 1.8 – 2.0 ppm (depending on the substitution variant). Such a separation of the signals indicates for the location of H(2,23) protons within the deshielding zone of the phenanthrene ring situated below. Similar effect has been recently demonstrated for helicenophyrins 4 and 5, where two pyrrole rings were located in the shielding region below aza[5]helicene unit.88 The 1H NMR spectrum of 9a-1 recorded at 220 K contains two sets of phenanthrenylene resonances due to nonequivalence of its sides (left vs. right) (Figure 2). The H(46,52) and H(43,49) protons give rise to doublets (4J = 1.3 – 1.4 Hz) at 9.74 and 7.93 ppm coupled with two doublets of doublets of H(9,30) and H(2,23) at 6.93 and 8.98 ppm, respectively. The signals of third part of the AMX spin system of the phenanthrene moiety, namely H(8,29) and H(3,24) appears as doublets (3J = 8.7 – 8.8 Hz) at 7.76 and 7.24 ppm. Two pyrrole rings give rise to two pairs of β-H signals located, as expected for nonaromatic porphyrinoids,81,87,88 at the 5.9 – 7.1 ppm region. A narrow NH signal appears at the 13.03 ppm in the spectra measured at 300 K indicating for hydrogen bonding within the dipyrromethene subunit (δ=12.5 ppm value was documented for 5‐phenyl‐4,6‐dipyrrin)93. Interestingly, in the 1H-1H COSY spectrum recorded at 300 K the NH signal correlates to all four β-pyrrolic protons suggesting fast, on the NMR time scale, tautomerization (Figure S4, SI). Also, practically identical relative energies of three tautomers 9a-1-I, 9a-1-II, and 9a-1-III confirms their accessibility at 300 K. The


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similar spectroscopic response was described for tetraphenylsapphyrin.94 Chart 2. Relative energies calculated for DFT-optimized [ωB97XD/6-31G(d,p)] models of 9a-1 and 9a-2 tautomers. Positions of NH atoms in each tautomer are marked with pink circles. C6F5

C6F5 N

Ph Ph

C6F5 C6F5

N HN

NH

Ph

N

HN

Ph

Ph OMe MeO MeO OMe

Ph MeO

9a-1-I E = 0.0 kcal/mol (E = 6.6 kcal/mol vs 9a-2-I)

N

Ph Ph

NH

N H

Ph

OMe MeO MeO OMe

N

MeO

OMe MeO MeO OMe 9a-1-III E = 0.3 kcal/mol

MeO

OMe

C6F5 C6F5 Ph

N

NH

N Ph

Ph

Ph

Ph

Ph

OMe

C6F5 N H

HN

N

9a-2-II E = 1.4 kcal/mol

C6F5 Ph Ph

HN Ph

9a-1-II E = 0.3 kcal/mol

N H

OMe

C6F5 C6F5

Ph

N

MeO

9a-2-I E = 0 kcal/mol

N

Ph

Ph

Ph

OMe

C6F5

C6F5

N

NH

MeO

OMe

HN

N

Ph

Ph

MeO

OMe

9a-2-III E = 2.9 kcal/mol

Due to large broadening of meso-phenyl resonances in the 1H NMR spectra of 9a-1 at 300 K the assignment of all peaks was not possible. Lowering the temperature slowed down dynamic processes, including the rotation of meso-aryl rings, which resulted in the decoalescence of the signals allowing for their complete assignment (Figure S10, SI). Also, measuring the 1H1H COSY spectrum at 180 K helped determining the principal tautomer as 9a-1-I (Chart 2). This is consistent with the lowest relative energy of this species predicted by theoretical calculations. Differently than for 9-1, two pyrrole rings, together with their Cα–Cmeso bonds, in the conformer 9-2 are located at the crossing of the figure-of-eight. This geometry also manifests itself through another set of NOE contacts in the NOESY/ROESY spectra, unique for the 9-2 conformer (Figure 2, trace B, Figure S44, S46, S54, S56). Namely, the NH(48,54) protons of E/J pyrroles show dipolar couplings not only to H(43,49) and H(46,52) of phenanthrenylene moieties but they also throughspace correlates with ortho- and meta- protons of 21,42-phenyls at the crossing of the figure-of-eight. Counterintuitively, due to the effective C2 symmetry of the molecule, also the β-pyrrolic H(19,40) of E and J pyrroles are in the close proximity to protons within macrocyclic semi-pockets enforcing the H(19,40)···H(46,52) and H(19,40)···H(43,49) through-space contacts (Figure 2). This unique set of dipolar couplings constitutes the spectroscopic fingerprint of the 9-2 conformer. Spatial disengagement of two phenanthrene units brought together the 1H NMR signals of protons H(2,23) and H(9,30)

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that in the case of 9a-2 are separated by only 0.3 ppm (Figure S40, DCM-d2, 300 K). Other than for 9-1, the 1H-1H COSY spectra recorded at 300 K and at 200 K show intense cross peaks between NH(48,54) and only one pair of β-pyrrolic signals indicating that the tautomer with the amine-type NH groups on the pyrrole rings E/J predominates in the solution state (Figures S42, S52, SI). This observation is consistent with the DFT calculations indicating that in a series of three tautomers 9a-2I, 9a-2-II, and 9a-2-III, the first one has the lowest energy (Chart 2). Solid state structures of 9-1 and 9-2. X-ray quality monocrystals of 9a-1 and 9b-2 were grown by slow evaporation of their solutions in CHCl3/MeOH and CHCl3/n-hexane, respectively. Both 9-1 and 9-2 conserved their solution conformations in the solid state. The molecules of 9a-1 adopt figure-of-eight, or crescent-like, conformation with two pairs of benzene rings A,B and F,G of the independent phenanthrene moieties located at the intersection, altogether with the adjacent C(1,42)–C(22,21) bonds (Figure 3A). The distance between above lying carbon atoms of the phenanthrene rings are ranging from 3.49 – 3.88 Å indicatively for the offset, face-to-face π···π stacking attractive interactions as the major factors stabilizing the conformation 91.95 The interplanar angles between A(F) and C(H) benzene rings of phenanthrene equal to 7.3 – 7.5° suggest considerable steric repulsion between protons H(43,46) and H(49,52) in the bay region of phenanthrene units in the 9-1 conformer. Lengths of C(1)–C(42), C(10)–C(11), C(22)–C(21), and C(31)–(C32) bonds linking two phenanthrenylene rings with the dipyrromethene units equal to 1.477(8), 1.467(6), 1.468(8), and 1.468(5) Å indicate for their C(sp2)–C(sp2) single bond character. Interestingly, the tautomer 9a-1-II have been identified in the solid state (Chart 2). Figure-of-eight molecules of 9b-2 has amine-type pyrrole rings and adjacent Cα–Cmeso bonds at the intersection (Figure 3B). In this case, stabilization of the conformation might be arising from the π···π stacking of the phenyl rings at 21,42 positions and the phenanthrene moieties, as suggested by the close distance between the above lying carbon atoms of mesoPh and the bay-region phenanthrene carbons ranging from 3.27 – 3.83 Å for one, and 3.37 – 3.72 Å for the second pair of interacting rings.95


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Journal of the American Chemical Society additional factor facilitating the conversion of 9-1 into 9-2. Bond lengths C(1)–C(42), C(10)–C(11), C(22)–C(21) and C(31)–(C32) are equal to 1.464(8), 1.477(5), 1.463(6), and 1.461(5) Å suggest that isomerization did not affect their single bond character. Isomerization. When analyzing structural differences between 9-1 and 9-2 stereoisomers, one can follow the formalism proposed for description of porphyrinoids conformations,6 being actually the extension of the system applied previously for annulenes (Chart 3).96 Application of this approach requires defining concave and convex sides of hetero- and carbocyclic subunits followed by determination of the individual configuration (cis or trans) of each of every two, formally single bonds forming bridges between subunits. Chart 3. Determination of the conformational descriptors for 9-1 and 9-2. convex side convex side

concave side

c

c

c

concave side

t c

cis-cis cc

cis-trans ct

c

c

c

c

c

c

c c

c

c

cis-cis cc

t t c

c

9-1 tc cc cc tc cc cc

t cis-trans ct

c

c

c

c

c c

c t c

t

c

c

9-2 ct cc cc ct cc cc inversion

Assigning the bonds configuration was started from the carbon atom marked with black circle and moving clockwise along the macrocycle.

Figure 3. Molecular structures of (M,M)-9a-1 and (P,P)-9b-2: top – upfront view, bottom – side view with meso-aryl groups and protons omitted for clarity. Displacement ellipsoids are shown at 50% probability level.

Interestingly, the phenanthrene moieties are evidently more twisted in 9-2 conformer. Evidently much larger values of interplanar angles between terminal benzene rings A/C and F/H equal 12.8 and 21.1° (7.3 – 7.5° in 9-1) suggest that the torsional strain of phenanthrene is released, in comparison to 9a-1. Minimization of the unfavorable intramolecular steric repulsion between bay-region protons of phenanthrene might be the

Use of this formalism for (M,M)-enantiomers of 9-1 and 9-2 leads to (tccccctccccc) and (ctccccctcccc) conformational descriptors, respectively, and indicates that the rearrangement of 91 to 9-2 requires cis-trans isomerization of tc/tc to ct/ct sets of bonds linking two phenanthrenylene moieties with neighboring pyrrole rings. Alternatively, one can analyze double bonds configurations within the frameworks of 9-1 and 9-2 allowing for their classification as the (Z,Z,Z,Z,Z,Z) and (Z,Z,E,Z,Z,E) isomers. Therefore, the conversion between 9-1 and 9-2 is, in fact, the effect of cis-trans isomerization of two double bonds within the macrocyclic framework of 9, that translates into two distinctive structures differing in relative spatial orientation of cyclic subunits in respect to the loop of figure-of-eight shape.

Energy difference between the most stable tautomers of diphenanthrioctaphyrins 9a-1 and 9a-2 was found to be relatively small with 9a-2 being 6.6 kcal/mol more stable than 9a-1, as shown by DFT predictions (Chart 2). In order to determine whether 9-1 and 9-2 are in the thermodynamic equilibrium, a series of NMR experiments were conducted



where solutions of both 9a conformers have been subjected to heating in deuterated solvents with increasing boiling points, namely: chloroform-d (61 oC), toluene-d8 (111oC), pyridine-d5 (115 oC), chlorobenzene-d5 (131 oC), DMF-d7 (153 oC), and DMSO-d6 (189 oC). The 1H NMR spectra of 9a-1 and 9a-2 in each of these solvents were recorded for pure species before, and after prolonged heating (up to one week). It was found that boiling of the 9a-1 and 9a-2 solutions in chloroform-d and toluene-d8 did not result in the enrichment of the sample with the second conformer, whereas for pyridine-d5, chlorobenzened5, DMF-d7, and DMSO-d6 prolonged heating at the temperature approaching boiling point of the solvent resulted in the appearance of the set of resonances unambiguously assigned to the alternative figure-of-eight isomer. Subsequently, we have demonstrated that addition of amine to the solutions of 9a-1 and 9a-2 in toluene-d8 triggered the partial 9a-1 to 9a-2 interconversion not observable in pure toluene-d8. These findings suggest that the interconversion of 9-1 and 9-2 might be conducted thermally using highly boiling solvents (e.g. chlorobenzene) but is strongly facilitated by the external agent acting as the hydrogen bond acceptor (HBA). The proposed mechanism of the isomerization under such conditions would include 1) binding of the HBA molecules to 9-1 through hydrogen bonding with dipyrromethene units, 2) barging of HBA within transient species enforcing the structural change releasing the strain in the macrocycle, and 3) dissociation of HBA forming 9-2 (Scheme 2). In each case the enrichment of the sample was considerably larger in favor of 9a-2 suggesting the equilibrium is shifted toward this species. Its much worse solubility in most of tested solvents is most likely additionally shifting the equilibrium toward this species that might partially precipitate from the refluxing solution. The conversion between conformers was monitored by UV-vis spectroscopy (Figure 4). The electronic absorption spectra recorded for samples of the boiling pyridine solution of 9a-1 demonstrated gradual conversion of 9a-1 into 9a-2 over the 8 hours period. The 1H NMR spectrum of the reaction mixture showed practically complete conversion into 9a-2 species with only traces of 9a-1 Boron(III) insertion. Molecular structures of 9-1 and 9-2 suggest both of them might potentially act as ligands able to bind up to two metal or metalloid centers. However, the coordination pockets of two isomers are evidently different, potentially engaging, apart from two N donors, different CH groups in binding of the central atom(s). Due to relatively small sizes of the coordination pockets in both species we have decided to explore boron(III) chemistry. Scheme 2. Proposed mechanism of 9-1 to 9-2 isomerization in presence of hydrogen bond acceptor. Bond characters and methoxy groups were omitted for clarity.

Page 6 of 14 Ar

Ar Ph Ph

N

N HN

NH

Ph

Ph 1) HBA

9-1

Ar

Ar N

Ph Ph

N

2)

H N

N H

Ar

N

N

N

Ph

H

Ph

Ph

Ph

Ar

N H

Ph

Ph

9-2-HBA

9-1-HBA 3) Ar

Ph

N

HBA

Ar

HN

NH

Ph

N

Ph

Ph

9-2

Figure 4. The UV-vis spectra of mixture aliquots taken from the refluxing pyridine solution of 9a-1 (DCM/pyridine, 298 K).

Refluxing 9a-1 in freshly distilled toluene with excess of boron(III) trifluoride dietherate in presence of dry triethylamine for 3 hours resulted in formation of bis-boron(III) octaphyrin 9a-2-(BF2)2 (Scheme 3). After typical work-up and chromatographic separation the complex was isolated in 34% yield. The boron(III) insertion was unambiguously confirmed by high-resolution mass spectrometry which showed the molecular ion [M+Na]+ at m/z = 1563.3830 (calcd. for C90H52B2F14N4O4Na+ m/z = 1563.3849) (Figure S102, SI). Our attempts of boron(III) insertion in absence of amine have failed and no traces of macrocyclic boron(III) complex were found. Scheme 3. Synthesis of 9a-2-(BF2)2 TEA – triethylamine).


Page 7 of 14 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

Journal of the American Chemical Society coupling with fluorine (J ~ 0.8 Hz) resulting in more complex shape of the resonance line.

C6F5 C6F5 1. BF3:Et2O, TEA, toluene, reflux, 3 h 2. TEA

Ph

N B

N

F F Ph

9a-1 or 9a-2

MeO

OMe

N B F

N

Ph

F

Ph

MeO

OMe

9a-2-(BF2)2, 34% (from 9a-1)

Interestingly, exactly the same product has been obtained when 9a-2 was used as the substrate indicating that under the reaction conditions the metalloid center selects only one conformer that fits optimally the geometric constraints imposed by the boron(III) center. The thermodynamic equilibrium between 9a-1 and 9a-2 is essential for the outcome of boron(III) insertion. The UV-vis spectrum of 9a-2-(BF2)2 is strongly altered in comparison to 9a-2 (Figure 1). It contains a band located at 355 nm (logƐ = 4.7), partially overlapping with broad one at 446 nm (4.2) reaching up to 500 nm, and the absorption ranging from 500 – 800 nm with a maximum at 625 nm (4.6). Boron(III) insertion was corroborated by 1H, 11B and 19F NMR spectroscopies, including 19F-19F COSY experiment allowing to unambiguously distinguish fluorine atoms belonging to the perfluorophenyl- and BF2 moieties (Figure S88, SI). The 11B resonance was identified at 4.13 ppm (referenced to HBF4 used as the external standard for boron nuclei; Figure S89, SI). The coordination of two BF2 groups was confirmed by the disappearance of the NH peaks and altering of the remaining resonances of the ligand, with the spectrum maintaining the symmetry of the free base (Figure 5). Evidently, the 1H NMR spectrum of 9a-2-(BF2)2 presents the spectral pattern indicating that macrocyclic ligand within the complex adopts the geometry of 9a-2 free base. Especially, spatial separation of two phenanthrene units resulted in very similar chemical shifts of the signals assigned to two non-equivalent „halves” of phenanthrenylene moieties. In addition, the placement of two BF2 groups within semi-pockets of the macrocycle restricts the rotation of meso-phenyl substituents located at the intersection of the figure-of-eight macrocycle resulting in appearance of five, well separated signals in the 5.1 – 7.3 ppm range. Eventually, unambiguous confirmation of the macrocyclic ligand’s conformation in 9a-2-(BF2)2 has been provided by the ROESY spectrum recorded at 240 K (Figure S83, SI). Identification of the H(46/52)···H(19/40) and H(46/52)···ortho-H(21/42) set of NOE dipolar couplings provided the ultimate proof for the conformation of the macrocycle within the bis-boron(III) complex. Quite unusual feature of the 1H NMR spectrum of 9a-2(BF2)2 is the form of H(46/52) and H(43/49) peaks. When one of the internal phenanthrenylene peaks has an expected coupling pattern seen in the spectra of the free bases 9-1 and 92, the appearance of the second signal is strongly altered due to involvement of only one proton of each pair into the CH···FB hydrogen bond formed with the fluoride ligands of BF2 moieties. 97,98 In the particular case of the 9a-2-(BF2)2 the CH···FB interaction is a result of the entrapment of BF and CH units in close proximity enforcing the interaction. The H(46,52) phenanthrenylene protons not involved into the interaction with fluoride of BF2 give rise to a doublet with 4JH-H coupling constant of ca. 1.2 Hz, whereas the signal of the H(43,49), being involved in the CH···FB interaction, experiences peculiar

Figure 5. The 1H NMR spectrum of 9a-2-(BF2)2 (240 K, CDCl3, 600 MHz). Inset presents the 11B NMR spectrum (300 K, CDCl3, 192.5 MHz). The prospective DFT-optimized model of 9a-2-(BF2)2 was constructed taking into consideration the geometrical constraints imposed by the NOE correlations (Figure 6). The characteristic structural feature of the complex is larger, in comparison with 9a2, separation of the opposite lying halves of the molecule due to the presence of BF2 groups in the macrocyclic pockets. The distance between phenanthrenylene protons H(43/49) and one of fluoride ligand in each BF2 groups indeed indicate for CH···FB hydrogen bonds. The H···F distances vary in the range 2.167 – 2.171 Å, with the corresponding C-H···F angles equal to 137.9, and 140.6°.97,98

Chiroptical properties. Figure-of-eight shapes of both 9-1 and 9-2 molecules make these systems topologically chiral. Racemic mixtures of 9a/b-1 and 9a/b-2 were separated into enantiomers by HPLC on the column with chiral stationary phase (Figures S108-112, SI). Optical activity of each collected stereoisomer was confirmed by measuring circular dichroism spectra (Figure 7). The absolute configurations of the enantiomers were assigned by comparison of experimental and TD‐DFT calculated spectra (Figures S114, S116 SI). Satisfactory agreement between calculated and recorded CD was observed for each set. Interestingly, the stereodynamic properties of 9-1 and 9-2 are clearly different, with the configuration stability of separated enantiomers strongly depending on the type of substituents at 16,37-meso-positions.



Page 8 of 14

enantiomers was even smaller, with the racemization constant krac = 0.502 (min-1) (295.5 K) and enantiomer half-life time of 1.4 min (at RT) (Figure S123, SI), while separated enantiomers of 9b-2 were similarly resistive to racemization as 9a-2 (Figure S124, SI).

Figure 6. DFT-optimized [ωB97XD/6-31G(d,p)] model of (P,P)-9a-(BF2)2 (top – upfront view, bottom – side view).

Both free bases 9-1 and 9-2, as well as the complex 9a-2(BF2)2 are responsive in the circular dichroism spectroscopy in the UV-vis-NIR region (Figure 7). The Cotton effects in the CD spectrum of (M,M)-9a-1 appear at λ/nm (ΔƐ/M-1cm-1) 260 (6.1), 302 (–2.1) 372 (7.5), 437 (20), 460 (23.1), 647 (–43.8), and 807 (11.3). The circular dichroism spectrum of (M,M)-9a2 is characterized by major Cotton effects appearing at λ/nm (ΔƐ/M-1cm-1) 239 (–22.2), 244 (–21.6), 256 (–16.4), 266 (–5.8), 284 (5.4), 360 (43.5), 379 (67.5), 448 (–24.0), 473 (–35.5), and 800 (–4.0), while the spectrum of (M,M)-(9a-2)-(BF2)2 consists of Cotton effects at λ/nm (ΔƐ/M-1cm-1) 237 (–53.0), 259 (– 94.3), 273 (58.9), 306 (46.1), 330 (62.9), 358 (133.9), 389 (– 74.4), 453 (–142.6), 617 (232.6), and 712 (–102.0). Once the single enantiomers of 9a-1 and 9a-2 were isolated, the time decay of the ECD signal was monitored at various temperatures. When the racemization process was completed the kinetic constant was determined, and from the series of measurements at different temperatures the energies of activation for racemization were calculated altogether with the half-life time of the enantiomer. Interestingly, the separated enantiomers of 9a-1 racemized quite rapidly, with the rate constant krac = 0.131 (min-1) and half-life time of 5.2 min (295.5 K) (Figure S120, SI), while the separated stereoisomers of 9a2 were configurationally stable. Energy of activation for racemization of 9a-1 is equal to Ea = 17.1(2) kcal/mol. Activation enthalpy and entropy of the racemization were calculated using the Eyring plot of ln(k/T) against 1/T and they are equal ΔH‡ = 16.7 kcal/mol, and ΔS‡ = −14.3 cal/mol (Figures S121,122, SI). Free enthalpy of activation at 298 K calculated based on these data was equal to ΔG‡298 = 20.9 kcal/mol which is slightly smaller than values determined for racemization of [36]octaphyrin(2.1.0.1.2.1.0.1) (ΔG‡298 = 23.1 kcal/mol),28 and quadruply N-methylated octaphyrin (ΔG‡298 = 22.74 (kcal/mol).51 The configuration stability of separated 9b-1

Figure 7. Circular dichroism spectra of 9a-1 (DCM/hexane 85/15 v/v, red traces), 9a-2 (DCM, blue traces), and (9a-2)-(BF2)2 (DCM/hexane 25/75 v/v, black traces). The solid lines represent enantiomers (M,M), and the dashed lines enantiomers (P,P) for each of the compounds.

Boron(III) insertion, strongly influenced the stereodynamic properties of 9a-2 macrocycle within 9a-2-(BF2)2 complex. As expected, the bulkiness of BF2 groups located within two semipockets of the ligand disturbed the phenyl-phenanthrene π∙∙∙π stacking interactions allowing for racemization of HPLCseparated enantiomers. Still, quite tight geometry of the complex makes the racemization process much more difficult than for the free base 9a-1, with the Ea equal to 24.0(7) kcal/mol, krac = 0.0146 min–1 (343 K), and extrapolated to roomtemperature enantiomer half-life time of about a week (Figure S125, SI). The activation enthalpy and entropy of activation obtained from the Eyring plot are equal to ΔH‡ = 23.5 kcal/mol, and ΔS‡ = −6.8 cal/mol, whereas the calculated free activation enthalpy ΔG‡298 = 25.5 kcal/mol (Figure S126,127 SI). This is considerably smaller value than the one reported by Osuka et al. for racemization of palladium(II) [28]hexaphyrin (ΔG‡373 = 30.4 kcal/mol).99 For both, free base 9a-1 and bis-boron complex 9a-2-(BF2)2 the racemization process of resolved enantiomers is expected to consist in disentangling the figure-of-eight conformation of the macrocycle and folding into the structure with the opposite twist (absolute configuration) of the lemniscate (Scheme 4). Such conformational rearrangement resulting in change of the configuration of an enantiomer to the opposite might be a onestep reconfiguration going through a single transient achiral species, as well as a multi-step process involving an achiral transient species and a series of chiral intermediates. In an attempt to understand the possible mechanism of racemization reaction of 9-1 we have prepared DFT-optimized model of an intermediary species 10 that might be, in geometrical sense, close to a possible transition state of such rearrangement (Figure S135, SI). Actually, the involvement of an achiral, disentangled species of this kind have been previously proposed as a rationalization explaining the inversion of configuration of turcasarin,100 and [36]octaphyrin(2.1.0.1.2.1.0.1)


Page 9 of 14 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


enantiomers.28 Herges suggested that the transition state in the racemization of octaphyrin(1.1.1.1.1.1.1.1) may acquire the boat-like conformation.101 Application of the same formalism that have been used for illustrative description of the bonding system within 9-1 and 9-2 stereoisomers allows identifying the bonds reconfiguration governing the (M,M) ↔ (P,P) inversions of 9-1 and 9-2-(BF2)2 enantiomers (Scheme 4). Accordingly, the following classification of the appropriate stereoisomers can be applied: (M,M)-9-1 (tccccctccccc), (P,P)-9-1 (ccccctccccct), (M,M)-92-(BF2)2 (ctccccctcccc), and (P,P)-9-2-(BF2)2 (cccctccccctc). In the case of the 9-1 inversion crucial for the rearrangement are the cis-trans isomerization of bonds between phenanthrene rings and meso positions (tctc ↔ ctct), whereas for the bisboron(III) complex 9-2-(BF2)2 the (tctc ↔ ctct) inversion of pyrrolic Cα-Cmeso bonds linking the dipyrromethene units with phenanthrene moieties is crucial for the rearrangement. Scheme 4. Proposed rearrangements of 9-1 and 9-2-(BF2)2 leading to racemization. Positions of the same rings in both enantiomers are marked with an orange and pink squares. A) c

c

c

c

c

c

c

c

c

c

c

cc

c

B

N

N

N

9-1 (M,M)

c

c

c

cc

c

c

t

N

(P,P)-9-1 cc cc ct cc cc ct

c B

t

N

N

N

N

c

c

(M,M)-9-1 tc cc cc tc cc cc c

N

75o

9-1 (P,P)

c

c

c

c

c

75o

t t

t t

B)

c

be stored for long time (9-2) or quickly erased (9-1) by a simple conformational rearrangement of the macrocycle. Moreover, they carry the direction information, as the isomerization of the macrocyclic framework is changing the relative orientation of the substituents, affecting properties of the macrocycle, e.g. its polarity (Scheme 5). Further work on application of 9 as the macrocyclic platform for functional supramolecular systems is currently under investigation in our laboratory. Scheme 5. Diphenanthrioctaphyrin as the molecular switch (only relevant meso positions are marked).

c

c

B

c B

c c

t c c

(M,M)-9-2-(BF2)2 ct cc cc ct cc cc

(P,P)-9-2-(BF2)2 cc cc tc cc cc tc

N

N

9-2

c

t

N

c

CONCLUSIONS AND OUTLOOK In this contribution we have shown the synthesis of diphenanthrioctaphyrin(1.1.1.0.1.1.1.0) 9 that in its free base form exists as two locked conformers 9-1 and 9-2 stabilized by the intramolecular interactions. Both isomeric macrocycles were separated and fully characterized in the solution and solid state, and their thermally-induced isomerization, facilitated by presence of hydrogen bond acceptors, has been demonstrated. Racemic mixtures of topologically chiral diphenanthrioctaphyrins were separated into enantiomers and their stereodynamic properties were shown to strongly depend on the conformation. The inertness of 9-2 enantiomers in the racemization reaction was possibly affected by disruption of intramolecular π∙∙∙π stacking between aromatic panels within the macrocycle, through introduction of two BF2 groups into the macrocyclic pockets. Interestingly, boron(III) cations were proven to act as topology selector stabilizing only 9-2 geometry of the macrocycle, irrespective of the conformation of the starting material. Diphenanthrioctaphyrin 9 may be treated as a simple, macrocyclic molecular switching system whose reversible conformational rearrangements can be easily controlled. Due to strikingly diverse stereodynamic properties two conformers, 91 and 9-2, carry different stereochemical information that can

EXPERIMENTAL SECTION 11,21,32,42-Tetraphenyl-16,37-diperfluorophenyl5,6,26,27-tetramethoxydiphenanthrioctaphyrin(1.1.1.0.1.1.1.0) 9a-1. In a 1000 mL round-bottomed flask equipped with a magnetic stirrer, 3,6-bis(phenyl-(2pyrolyl)methyl)-9,10-dimethoxyphenanthrene 8 (548 mg, 1.0 mmol) and perfluorobenzaldehyde (196 mg, 1.0 mmol) were dissolved in amylene-stabilized chloroform (900 mL). The solution was purged with nitrogen for 20 minutes. Boron trifluoride – diethyl etherate (100 L) was then added and the reaction mixture was protected from light and stirred for two hours under nitrogen. 2,3-Dichloro-5,6-dicyano-1,4benzoquinone (DDQ; 454 mg, 2.0 mmol) was subsequently added and the reaction mixture was stirred for another ten minutes. After that time solvent was evaporated under reduced pressure and the dark residue was subjected to preliminary column chromatography (basic alumina deactivated by addition of 4 mL of water per 100 g of alumina, dichloromethane). The first, dark band was collected and then chromatographed over silica gel (70-230 mesh) with n-hexane–dichloromethane (2/8, v/v) as the eluent. The desired product was eluted as the second, green band. After subsequent chromatography (silica gel (70230 mesh), dichloromethane–ethyl acetate (9/1, v/v)) the product was eluted as the second, green band. Yield: 42 mg (6%). Not all of the meso-aryl signals were assigned due to their considerable broadening and overlapping in the 300 – 180 K temperature range. NMR (500 MHz, [D]chloroform, 300 K):  (ppm) 13.03 (b, 2H, NH), 9.74 (d, 2H, 4J = 1.4 Hz, 46,52-H), 8.98 (dd, 2H, 3J = 8.5 Hz, 4J = 1.5 Hz, 2,23-H), 7.93 (d, 2H, 4J = 1.3 Hz, 43,49H), 7.76 (d, 2H, 3J = 8.8 Hz, 8,29-H), 7.38 (t, 3J ~ 7.0 – 7.3 Hz, 1H



Ph), 7.32 (t, 3J ~ 7.6 Hz, Ph), 7.24 (d overlapping with solvent signal, 3J = 8.7 Hz, 3,24-H), 7.21 (t, 3J ~ 7.5 Hz, Ph), 7.14 (b, Ph), 6.93 (dd, 2H, 3J = 8.8 Hz, 4J = 1.6 Hz, 9,30-H), 6.80 (d, 2H, 3J = 5.2 Hz, 14,35-H), 6.34 (d, 2H, 3J = 5.1 Hz, 13,34-H), 6.30 (m, 3J = 5.2 Hz, 4J = 1.3 Hz, 19,40-H), 5.98 (d, 2H, 3J = 5.1 Hz, 18,39-H), 3.82 (s, 6H, 5,26-OMe), 3.81 (s, 6H, 6,27OMe). 13C NMR (151 MHz, [D2]dichloromethane, 300 K)  (ppm): 163.4, 160.1, 151.4, 148.7, 148.2 (b), 145.0 (b), 144.6, 143.1, 142.7, 142.2, 140.2 (b), 137.3, 137.1, 136.8 (b), 136.2, 135.8, 135.6, 135.3, 132.3, 132.1 (b), 131.0, 129.5, 129.0, 128.9, 128.8, 128.63, 128.58, 128.55, 128.4, 128.35, 126.9, 126.7, 126.5, 125.1, 122.8, 122.7, 114.2, 61.4, 61.3. 19F NMR (546 MHz, [D]chloroform, 300 K)  (ppm): −137.8 (dd, 2F, 3J = 24.3 Hz, 4J = 8.0 Hz, 16,37-ortho-C6F5), −138.4 (dd, 2F, 3J = 24.7 Hz, 4J = 8.0 Hz, 16,37-ortho-C6F5), −155.3 (t, 2F, 3J = 21.0 Hz, 16,37-para-C6F5), −162.0 (m, 2F, 16,37-meta-C6F5), −162.2 (m, 2F, 16,37-meta-C6F5). HRMS (ESI+, TOF) m/z: [M+H]+ 1445.4027, calcd 1445.4058 for C90H55F10N4O4+. UV– vis (CH2Cl2, 298 K): λmax (log ε) 255 (4.8), 374 (4.8), 458 (4.6), 656 (4.3). 11,21,32,42-Tetraphenyl-16,37-di(4-nitrophenyl)-5,6,26,27tetramethoxydiphenanthrioctaphyrin-(1.1.1.0.1.1.1.0) 9b-1. In a 500 mL round-bottomed flask equipped with a magnetic stirrer, 3,6-bis(phenyl-(2-pyrolyl)methyl)-9,10dimethoxyphenanthrene 8 (274 mg, 0.5 mmol) and 4nitrobenzaldehyde (76 mg, 0.5 mmol) were dissolved in ethanol-stabilized chloroform (450 mL). The solution was purged with nitrogen for 20 minutes. Boron trifluoride – diethyl etherate (50 L) was then added and the reaction mixture was protected from light and stirred for two hours under nitrogen. 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ; 227 mg, 1.0 mmol) was subsequently added and the reaction mixture was stirred for another ten minutes. After that time solvent was evaporated under reduced pressure and the dark residue was subjected to preliminary column chromatography (basic alumina deactivated by addition of 4 mL of water per 100 g of alumina, dichloromethane). The first, dark band was collected and then chromatographed over silica gel (70-230 mesh) with n-hexane–dichloromethane (3/7, v/v) as the eluent. The desired product was eluted as the second, green band. The crude product was recrystallized from dichloromethane/methanol yielding green solid. Yield: 8 mg (2%). Not all of the meso-aryl signals were assigned due to their considerable broadening and overlapping in the 300 – 180 K temperature range. NMR (500 MHz, [D]chloroform, 300 K):  (ppm) 13.01 (b, 2H, NH), 9.88 (b, 2H, 46,52-H), 8.77 (dd, 2H, 3J = 8.6 Hz, 4J = 1.7 Hz, 2,23-H), 8.33 (m, 4H, 16,37-m-PNP), 7.92 (b, 2H, 43,49-H), 7.75 (d, 2H, 3J = 8.8 Hz, 8,29-H), 7.59 (m, 4H, 16,37o-PNP), 7.37 (t, 3J ~ 6.9 – 7.1 Hz, Ph), 7.28 – 7.24 (m, Ph), 7.25 (d, 2H, 3J = 8.6 Hz, 3,24-H), 7.15 – 7.10 (m, Ph), 6.96 (dd, 2H, 3J = 8.8 Hz, 4J = 1.7 Hz, 9,30-H), 6.79 (d, 2H, 3J = 5.3 Hz, 13,34/14,35-H), 6.53 (d, 2H, 3J = 5.3 Hz, 13,34/14,35-H), 6.29 (d, 2H, 3J = 5.1 Hz, 19,40-H), 6.06 (d, 2H, 3J = 5.1 Hz, 18,39H), 3.82 (s, 6H, 6,27-OMe), 3.79 (s, 6H, 5,26-OMe). 13C NMR (151 MHz, [D]chloroform, 300 K)  (ppm): 163.9, 157.5, 152.0, 147.2, 147.0, 146.6, 144.0, 142.6, 142.1, 141.9, 136.6, 136.4, 135.9, 135.7, 133.9, 132.6, 132.2, 131.9, 130.3, 129.0, 128.4, 128.2, 127.83, 127.77, 127.25, 127.21, 126.8, 125.8, 125.1, 123.7, 122.2, 122.0, 106.0, 60.9, 60.8. HRMS (ESI+, TOF) m/z: [M+H]+ 1355.4669, calcd: 1355.4702 for 1H

Page 10 of 14

C90H63N6O8+. UV–vis (CH2Cl2, 298 K): λmax (log ε) 260 (4.9), 373 (4.8), 470 (4.6), 678 (4.4). 11,21,32,42-Tetraphenyl-16,37-diperfluorophenyl5,6,26,27-tetramethoxydiphenanthrioctaphyrin(1.1.1.0.1.1.1.0) 9a-2. In a 1000 mL round-bottomed flask equipped with a magnetic stirrer, 3,6-bis(phenyl-(2pyrolyl)methyl)-9,10-dimethoxyphenanthrene 8 (548 mg, 1.0 mmol) and perfluorobenzaldehyde (196 mg, 1.0 mmol) were dissolved in amylene-stabilized chloroform (900 mL). The solution was purged with nitrogen for 20 minutes. Boron trifluoride – diethyl etherate (100 L) was then added and the reaction mixture was protected from light and stirred for two hours under nitrogen. 2,3-Dichloro-5,6-dicyano-1,4benzoquinone (DDQ; 454 mg, 2.0 mmol) was subsequently added and the reaction mixture was stirred for another ten minutes. After that time solvent was evaporated under reduced pressure and the dark residue was subjected to preliminary column chromatography (basic alumina deactivated by addition of 4 mL of water per 100 g of alumina, dichloromethane). The first, dark band was collected and then chromatographed over silica gel (70-230 mesh) with n-hexane–dichloromethane (2/8, v/v) as eluent. The desired product was eluted as the third, green band. The crude product was recrystallized from methanol yielding green solid. Yield: 53 mg (7%). Not all of the meso-aryl signals and were assigned due to their considerable broadening and overlapping in the 300 – 180 K temperature range. NMR (500 MHz, [D2]dichloromethane, 300 K):  (ppm) 13.48 (b, 2H, 48,54-NH), 9.68 (d, 2H, 4J ~1.2 Hz, 46,52-H), 8.32 (d, 2H, 4J ~1.2 Hz, 43,49-H), 8.04 (d, 2H, 3J = 8.8 Hz, 8,29H), 7.92 (d, 2H, 3J = 8.7 Hz, 3,24-H), 7.81 (b, Ph), 7.60 – 7.30 (b, Ph), 7.46 (t, 3J ~ 7.1 – 7.3 Hz, Ph), 7.31 (dd, 2H, 3J = 5.2 Hz, 4J = 1.5 Hz, 19,40-H), 7.20 (dd, 2H, 3J = 8.7 Hz, 4J = 1.5 Hz, 9,30-H), 7.06 (b, Ph), 6.92 (dd, 2H, 3J = 8.7 Hz, 4J = 1.5 Hz, 2,23-H), 6.78 (b, Ph), 6.60 (d, 2H, 3J = 4.9 Hz, 13,34-H), 6.57 – 6.56 (m, 2H, 18,39-H), 6.15 – 6.13 (m, 14,35-H, Ph), 5.89 (b, 2H, Ph), 5.66 (b, 2H, Ph), 4.13 (s, 6H, 6,27-OMe), 4.08 (s, 6H, 5,26-OMe). 13C NMR (126 MHz, [D]chloroform, 300 K)  (ppm): 167.5, 154.6, 154.2, 145.5, 145.3, 145.0, 142.9, 139.4, 138.8, 137.9, 137.3, 136.8, 131.9, 131.2, 130.5, 130.4, 130.1, 130.0, 129.5, 129.1, 128.9, 128.6, 128.3, 128.0, 127.8, 127.2, 126.9, 122.2, 121.8, 61.6(x2). 19F NMR (546 MHz, [D]chloroform, 300 K)  (ppm): −137.1 (m, 2F, 3J ~ 25 Hz, 16,37-ortho-C6F5), −140.6 (m, 2F, 3J ~ 24 Hz, 16,37-orthoC6F5), −155.0 (m, 2F, 16,37-para-C6F5), −161.7 (m, 2F, 16,37meta-C6F5), −162.8 (m, 2F, 16,37-meta-C6F5). HRMS (ESI+, TOF) m/z: [M+H]+ 1445.4107, calcd 1445.4058 for C90H55F10N4O4+. UV–vis (CH2Cl2, 298 K): λmax (log ε) 259 (sh. 295; 4.9), 380 (5.0), 446 (4.4), 472 (4.4), 647 (sh. 764; 4.6). 11,21,32,42-Tetraphenyl-16,37-di(4-nitrophenyl)-5,6,26,27tetramethoxy-diphenanthrioctaphyrin-(1.1.1.0.1.1.1.0) 9b2. In a 500 mL round-bottomed flask equipped with a magnetic stirrer, 3,6-bis(phenyl-(2-pyrolyl)methyl)-9,10dimethoxyphenanthrene 8 (274 mg, 0.5 mmol) and 4nitrobenzaldehyde (76 mg, 0.5 mmol) were dissolved in ethanol-stabilized chloroform (450 mL). The solution was purged with nitrogen for 20 minutes. Boron trifluoride – diethyl etherate (50 L) was then added and the reaction mixture was protected from light and stirred for two hours under nitrogen. 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ; 227 mg, 1 mmol) was subsequently added and the reaction mixture was stirred for another ten minutes. After that time solvent was 1H


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evaporated under reduced pressure and the dark residue was subjected to preliminary column chromatography (basic alumina deactivated by addition of 4 mL of water per 100 g of alumina, dichloromethane). The first, dark band was collected and then chromatographed over silica gel (70-230 mesh) with n-hexane–dichloromethane (3/7, v/v) as the eluent. The desired product was eluted as the third, green band. After subsequent chromatography (silica gel (70-230 mesh), dichloromethane–nhexane (9/1, v/v)) the crude product was recrystallized from methanol yielding green solid. Yield: 13 mg (4%). Not all of the meso-aryl signals were assigned due to their considerable broadening and overlapping in the 300 – 180 K temperature range. NMR (500 MHz, [D]chloroform, 300 K):  (ppm) 13.61 (b, 2H, 48,54-NH), 9.65 (d, 2H, 4J = 1.4 Hz, 46,52-H), 8.32 (d, 2H, 4J = 1.4 Hz, 43,49-H), 8.01 (d, 2H, 3J = 8.9 Hz, 8,29-H), 7.95 (b, Ar), 7.88 (d, 2H, 3J = 8.6 Hz, 3,24-H), 7.75 (b, 2H, Ar), 7.47 – 7.35 (b, m, Ar), 7.27 (b, Ar), 7.26 (dd, 2H, 3J = 5.3 Hz, 4J = 1.5 Hz, 19,40-H), 7.18 (dd, 2H, 3J = 8.7 Hz, 4J = 1.5 Hz, 9,30H), 6.93 (dd, 2H, 3J = 8.6 Hz, 4J = 1.7 Hz, 2,23-H), 6.73 (b, Ar), 6.70 (dd, 2H, 3J = 5.3 Hz, 4J = 1.2 Hz, 18,39-H), 6.54 (d, 2H, 3J = 4.9 Hz, 13,34-H), 6.28 (d, 2H, 3J = 4.9 Hz, 14,35-H), 6.13 (t, 2H, 3J = 7.4 Hz, 21,42-Ph), 5.90 (b, 2H, 21,42-Ph), 5.63 (b, 2H, 21,42-Ph), 4.11 (s, 6H, OMe), 4.06 (s, 6H, OMe). 13C NMR (151 MHz, [D]chloroform, 300 K)  (ppm): 167.0, 153.34, 153.31, 146.0, 145.9, 145.1, 144.9, 144.8, 144.2, 142.2, 138.2, 137.8, 136.9, 136.7, 136.3, 131.7 (b), 131.3, 131.0, 130.6, 129.9, 129.5, 129.4, 128.7, 128.2, 128.1, 127.9, 127.7, 127.3, 126.60, 126.59, 123.1, 121.5, 121.2, 105.8, 61.1, 61.0. HRMS (ESI+, TOF) m/z: [M+H]+ 1355.4702, calcd: 1355.4702 for C90H63N6O8+. UV–vis (CH2Cl2, 298 K): λmax (log ε) 259 (sh. 283; 5.0), 377 (4.9), 455 (4.6), 673 (sh. 606; 4.6). Bis(difluoroboron(III))-11,21,32,42-tetraphenyl-16,37diperfluorophenyl-5,6,26,27-tetramethoxydiphenanthrioctaphyrin(1.1.1.0.1.1.1.0) 9a-2-(BF2)2. In a 100 mL two-neck, round-bottom flask equipped with a magnetic stirrer and a reflux condenser with argon inlet 11,21,32,42tetraphenyl-16,37-diperfluorophenyl-5,6,26,27tetramethoxydiphenanthrioctaphyrin(1.1.1.0.1.1.1.0) 9a-1 (12 mg, 0.008 mmol) was dissolved in dry toluene (60 mL). Freshly distilled triethylamine (80 µL, 0.57 mmol) was added and the mixture was deoxygenated by purging with argon for 20 minutes. Boron trifluoride diethyl etherate (800 µL, 6.5 mmol) was added, which was accompanied by the color change of the solution from green to sapphire blue, and the mixture was boiling for 3 hours under argon. After this time the mixture was cooled to room temperature and the reaction was quenched by adding freshly distilled triethylamine (5 mL). The solvent was evaporated to dryness using rotary evaporator, and the green/blue residue was subjected to preliminary column chromatography (silica gel (70-230 mesh), dichloromethane). The first, green/blue band was collected and then chromatographed over silica gel (70-230 mesh) with n-hexane– dichloromethane (3/7, v/v) as the eluent. The product was eluted as the second, green-blue band. Yield 4.4 mg (34%). 1H

NMR (600 MHz, [D]chloroform, 300 K):  (ppm) 8.91 (b, 2H, 46,52-H), 8.63 (d, 2H, 4J = 1.1 Hz, 43,49-H), 7.94 (d, 2H, 3J = 8.6 Hz, 3,24-H), 7.90 (d, 2H, 3J = 8.6 Hz, 8,29-H), 7.28 (d, 3J = 7.6 Hz, Ph), 7.26 – 7.21 (m, Ph), 7.09 (d, 3J ~ 7.0 Hz, Ph), 6.99 (d, 2H, 3J = 5.1 Hz, 19,40-H), 6.97 (t, 2H, 3J = 7.6 Hz, Ph), 6.92 (dd, 2H, 3J = 8.6 Hz, 4J = 1.5 Hz, 9,30-H), 6.83 (dd, 2H, 3J = 8.6 Hz, 4J = 1.5 Hz, 2,23-H), 6.82 (d, 2H, 3J = 5.5 Hz, 1H

13,34/14,35-H), 6.58 (t, 2H, 3J = 7.5 Hz, Ph), 6.26 (d, 2H, 3J = 5.1 Hz, 18,39), 6.20 (d, 2H, 3J = 5.4 Hz, 13,34/14,35-H), 5.66 (d, 2H, 3J = 7.7 Hz, Ph), 5.24 (t, 2H, 3J = 7.7 Hz, Ph), 4.15 (s, 6H, 6,27-OMe), 4.05 (s, 6H, 5,26-OMe). 13C NMR (151 MHz, [D]chloroform, 300 K)  (ppm): 160.8, 159.3, 146.85, 146.78, 145.9, 145.4, 144.9, 144.0, 140.9, 140.6, 140.3, 140.2, 139.1, 137.8, 132.0, 131.6, 130.2, 129.6, 129.5, 129.4, 129.3, 129.2, 128.8, 128.1, 127.9, 127.7, 127.6, 126.5, 126.1, 126.0, 122.9, 122.7, 121.4, 121.2, 61.1 60.8. 19F NMR (546 MHz, [D]chloroform, 300 K)  (ppm): −123.7 (d, 2F, JF-B = 30.6 Hz, BF2), −123.8 (d, 2F, JF-B = 30.0 Hz, BF2), −136.2 (m, 2F, 16,37ortho-C6F5), −137.9 (dd, 2F, 3J = 24.6 Hz, 4J = 8.1 Hz, 16,37ortho-C6F5), −154.9 (t, 2F, 3J = 21.2 Hz, 16,37-para-C6F5), −162.0 (m, 2F, 16,37-meta-C6F5), - 162.1 (m, 2F, 16,37-metaC6F5). 11B NMR (192.5 MHz, [D]chloroform, 300 K)  (ppm): 4.13 (t, JB-F = 30.5 Hz). HRMS (ESI+, TOF) m/z: [M+Na]+ 1563.3868, calcd 1563.3842 for C90H52B2F14N4NaO4+. UV–vis (CH2Cl2, 298 K): λmax (log ε) 258 (4.9), 355 (4.7), 446 (4.2), 625 (4.7).

ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge via the Internet at http://pubs.acs.org. Full experimental details, compound characterization data, Cartesian coordinates of all computed chemical structures (from DFT studies), including additional information as indicated in the main text within this manuscript.

AUTHOR INFORMATION Corresponding Author * [email protected] * [email protected]

ACKNOWLEDGMENT The project was funded by the National Science Centre of Poland (2017/26/D/ST5/00184 to B.S., and 2016/23/B/ST5/0016 to L.L.-G). Quantum-chemical calculations were performed

in the Wrocław Center for Networking and Supercomputing (Grant 329).

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Diphenanthrioctaphyrin(1.1.1.0.1.1.1.0): Conformational Switching

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