Synthesis and Characterization of Ferrocenyl Chlorins, 1, 1

Feb 10, 2017 - Synthesis and Characterization of Ferrocenyl Chlorins, 1,1′-Ferrocene-Linked Chlorin Dimers, and their BODIPY Analogues...
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Synthesis and Characterization of Ferrocenyl Chlorins, 1,1′Ferrocene-Linked Chlorin Dimers, and their BODIPY Analogues Anna I. Arkhypchuk, Andreas Orthaber, and K. Eszter Borbas* Department of Chemistry, Ångström Laboratory, Uppsala University, Box 523, 75120 Uppsala, Sweden S Supporting Information *

ABSTRACT: We present the synthesis and characterization of meso-ferrocenyl-substituted hydroporphyrins (chlorins) and 1,1′-linked chlorin dimers. The dipyrromethane chlorin precursors were also transformed into Fc-substituted BODIPYs and 1,1′-ferrocenyl-linked BODIPY dimers. The chlorin dimers were studied by 1D and 2D NMR experiments and DFT calculations, which showed that their solution structures were dependent on the central metal. Monomeric and dimeric Ni(II) chlorins had similar 1H NMR spectra. Monomeric and dimeric free base, Zn(II), and Pd(II) chlorins, on the other hand, showed significantly more different spectra. The eclipsed conformer of the free base chlorin dimer was calculated to be energetically more favored than the open form. The chlorin and BODIPY fluorescence emissions were quenched in the Fcsubstituted compounds; these could be recovered by oxidation of the Fe(II) center. Cyclic voltammetry showed up to five oxidation waves for the free base chlorin dimer, which suggests that the macrocycles were not behaving independently of each other.

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surrogate25 (see Figure 1 for generalized structures).26 Various possibilities exist for BODIPY27,28 functionalizations, which place the Fc onto the indacene periphery or onto the boron atom.26 Multiple Fc units in the same molecule can give rise to metal−metal coupling, in some cases even over remarkably long (>10 Å) distances.29 This has been probed in Fcsubstituted single-pyrrole models30 as well as in oligopyrroles.31 Given how prominently artificial photosynthesis features among the potential applications of Fc-functionalized oligopyrroles, it is somewhat surprising that little work has been done on Fc-functionalized hydroporphyrins. Hydroporphyrins are porphyrinic tetrapyrroles lacking one or more peripheral double bonds. The most common hydroporphyrins are the chlorins,33,34 which contain one partially reduced pyrrole ring (Figure 1b). Chlorins constitute the cores of the chlorophylls and as such are responsible for light harvesting and photosynthesis on Earth. To date, there has been a single report on covalently Fc-modified chlorins (Figure 1b),32 which used naturally derived pyropheophorbide functionalized though its isocyclic ring. Most of the products were unstable and underwent oxidative ring opening upon exposure to air. While a ruthenocene derivative could be isolated and studied, the Fc analogue proved labile upon photoexcitation, which precluded its spectroscopic investigation. Here, we present chlorin monomers carrying one Fc unit and chlorin dimers linked by a 1,1′-ferrocenyl group. We report the chemical,

INTRODUCTION Tetrapyrroles are some of the most versatile frameworks for the well-defined arrangement of functional units. They are at the core of molecules with applications in sensing and imaging, medical diagnostics, therapeutics, artificial photosynthesis, and catalysis, as well as in supramolecular architectures. Combining the tetrapyrrole with a redox-active unit, such as a metallocene (most often ferrocene, FcH), affords external control over the desired activity: e.g., fluorescence emission and singlet oxygen production.1−4 Ferrocene provides a handle for a redox readout in sensors5 and for controlling electronic6 and conformational changes.7 Thus, Fc incorporation into functional tetrapyrroles has been a successful strategy to create molecular memory devices,8 machines,9 and wires,10 has provided increased selectivity for multielectron oxygen reduction,11 and has furnished model systems for electron transfer in artificial photosynthesis.12 Interestingly, ferrocene can generate reactive oxygen species in cells upon the recovery of its Fe2+ oxidation state from its one-electron-oxidized form.13,14 This property is increasingly being taken advantage of in cancer therapeutics to override the defense mechanisms of tumor cells.15 The location of the ferrocene, its distance from the oligopyrrolic core, and the type of linkage between the two depend on balancing synthetic necessities with exerting the desired control over the oligopyrrole’s properties.16−19 The cyclopentadienyl (Cp) ring can be attached to tetrapyrroles through C−C bonds at the macrocycle periphery,20,21 through C−M22,23 or X/L−M24 bonds to a suitable central metal, or by replacement of one of the pyrrole rings with a cyclopentadienyl © XXXX American Chemical Society

Received: December 30, 2016

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DOI: 10.1021/acs.inorgchem.6b03158 Inorg. Chem. XXXX, XXX, XXX−XXX

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The Fc-linked chlorin dimer (ZnChl)2Fc was synthesized from the ferrocenyl dialdehyde 7 in a procedure analogous to that described above (Scheme 2). Two alternatives were explored, and the protocol avoiding formylation of the Fcsubstituted dipyrromethane again proved superior. Briefly, monoformylation of both dipyrromethane units in 840 (available from 7) to 9 proceeded in 22% yield. The mass balance is accounted for by decomposed starting material and small amounts of overformylated products. Dibromination of 9, followed by condensation with 5,38 gave (ZnChl)2Fc in 3.8% yield. Alternatively, dibromination of 8 to 11 was quantitative, and the subsequent macrocyclization proceeded in 15% yield. This is in the range usually observed for meso-substituted chlorins. The ferrocenylated monomeric BODIPY dye BODIPYFc and the ferrocene-linked dimer BODIPY2Fc were prepared from the appropriate dipyrromethanes by oxidation to the dipyrrins with DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) and complexation with BF3·OEt2 (Scheme 3). The central Zn(II) ion could be removed upon treatment of ZnChlFc or (ZnChl)2Fc with TFA (trifluoroacetic acid) to furnish ChlFc or (Chl)2Fc, respectively. We could install Cu(II), Ni(II), and Pd(II) instead of Zn(II) by treatment of the free base compounds with Cu(OAc)2 at room temperature or with Ni(OAc)2 or Pd(acac)2 under microwave irradiation41,42 in the presence of a large excess of pyridine (Schemes 1 and 2). The chlorins and the BODIPYs were characterized by 1H and 13C NMR spectroscopy and high-resolution ESI-MS. A full assignment of 1H NMR resonances was possible by a combination of 1D and 2D experiments (see the Figures S1− S25 in the Supporting Information). Additionally, we were able to obtain single crystals of BODIPYFc suitable for crystallography by slow solvent evaporation from a saturated solution in a CH2Cl2−isopropyl alcohol mixture (Figure 2). The BODIPY core shows typical metrical parameters. The (Cp) ring of the ferrocenyl substituent is twisted by 35.2(2)° with respect to the BODIPY core about the C5−C10 axis; this value is close to that found in a previously reported crystal structure (42°).43 The solid-state packing is dominated by short Cp−centroid distances of 3.72 Å indicative of weak π−π interactions as well as short F···H interactions (2.48−2.51 Å) well below the sum of their van der Waals radii (2.65 Å). The solution structures of the chlorin dimers were further analyzed by NOESY NMR and variable-temperature 1H NMR. The chlorins could be divided in two groups depending on the central metal ions. The spectra of the monomeric and dimeric Ni(II) chelates have similar 1H NMR spectra. The minor differences are due to small upfield shifts of the aromatic signals. The shifts are largest for H-7, H-13, H-8, and H-12 and smallest for H-5 and H-15 (Figure 3). This suggests that in solution NiChlFc and (NiChl)2Fc have similar geometries. The free base, Zn(II), and Pd(II) chlorins, on the other hand, had significantly more different monomeric and dimeric spectra (Figure 3). Specifically, the H-8 and H-12 resonances are shifted downfield in the dimers in comparison to the monomers. The other signals are shifted upfield, most notably H-13 and H-5. Ni(II) chelation by porphyrins and chlorins is known to result in macrocycle ruffling to accommodate the small metal ion; free base, Zn(II), and Pd(II) chlorins, on the other hand, are quite planar. It is possible that the nonplanarity of the Ni(II) chlorins would prevent the two macrocycles in (NiChl)2Fc from adopting certain geometries that are available to (Chl)2Fc, (ZnChl)2Fc, and (PdChl)2Fc (vide infra).

Figure 1. (a) Possible porphyrin structures carrying directly linked or fused metallocenes. (b) Chlorins (pheophorbides) covalently attached to Fc units reported to date.32 (c) Access to 10-substituted ferrocenylchlorin and meso-Fc-BODIPY from the same Fc-dipyrromethane precursor.

photophysical, and electrochemical characterization of these species and compare them to the analogous BODIPY dyes. These compounds are interesting additions to the available arsenal of Fc-functionalized oligopyrroles by combining the Fcredox chemistry with light-harvesting ability in the red region.

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RESULTS AND DISCUSSION Synthesis. Monomeric and dimeric chlorins were prepared following Lindsey’s method35−37 as shown in Schemes 1 and 2. To access the monomeric Fc chlorin, ferrocene was incorporated in the 10-positions of the tetrapyrroles. Known ferrocenyl dipyrromethane 220 was obtained in 64% yield from aldehyde 1 following a reported procedure. Monoformylation of 2 was possible under Vilsmeier conditions, although 3 was obtained in only modest yields. This was due to the low reactivity of 2 at room temperature, which necessitated the heating of the reaction mixture. However, at high temperatures 2 has limited stability; furthermore, diformylation becomes prominent. Bromination of 3 with NBS afforded a so-called Eastern half (a 1-bromodipyrromethane, 4), which was condensed with a Western half (a tetrahydrodipyrrin, 5;38 Scheme 1) in a two-step procedure without purification of the linear tetrapyrrolic intermediate. The Zn chelate ZnChlFc was isolated after column chromatography on silica gel in 11.6% yield. The bottleneck of the synthesis appeared to be the preparation of 3. Therefore, we tested an alternative condensation that avoids its use. Monobromination of 2 was selective and high-yielding. The resulting 6 was condensed with formyl Western half 5CHO 39 under the standard conditions to give the target ZnChlFc in an excellent yield (43%). B

DOI: 10.1021/acs.inorgchem.6b03158 Inorg. Chem. XXXX, XXX, XXX−XXX

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Scheme 1. Preparation of the Zn(II) Chelate of Mono-Fc-chlorin ZnChlFc and its Transformation into ChlFc and MChlFc (M = Cu, Ni, Pd)a

a

TMPi = 2,2,6,6-tetramethylpiperidine.

The NOESY spectra of (ZnChl)2Fc at room temperature and at 90 °C were essentially identical (Figures S1−S4 in the Supporting Information). Even at high temperature, very strong NOE cross-peaks were seen between H-8 and H-12 and the Fc protons. Variable-temperature 1H NMR-spectra were recorded between +95 and −75 °C (Figure 4). When the sample was cooled from 95 to 25 °C, all aromatic peaks moved downfield, with the largest changes being observed for H-8 (Δδ 0.3 ppm), H-12 (Δδ 0.3 ppm), and H-20 (Δδ 0.6 ppm). Upon further cooling, between ca. −40 and −60 °C a coalescence point was reached. Continued lowering of the temperature to −75 °C resulted in the emergence of two sets of signals, which were tentatively assigned to the open and eclipsed forms of the dimer (vide infra). A full assignment of the new peaks was not possible due to the low solubility of (ZnChl)2Fc at low temperatures and the resulting poor spectrum quality. In order to further probe the dimer geometries, we performed density functional (DFT) calculations on (Chl)2Fc and (ZnChl)2Fc. The structures were fully optimized using the M06-2X functional with a 6-311G** triple-ζ basis set, which is known to perform well also for noncovalent interactions.44,45 Two minimum structures were identified on the PES

corresponding to the open and the eclipsed forms (Figure 5 and Figure S26 in the Supporting Information). In the open form of (Chl)2Fc the dihedral angle between the chlorins about the ferrocene swivel axis is 142.5°, while the chlorin planes twist by 44.3 and 45.0°. Consequently, no interaction between the two chlorin fragments is observed. The dihedral angle in the closed form is 11.2°, and the ferrocene takes a slightly eclipsed conformation. Both angles between the chlorin and the Cp planes are significantly reduced to 37.5°, which results in short distances between the two chlorin fragments: e.g., a centroid distance of 3.66 Å and short C···N/C (3.20/3.28 Å) distances. Importantly, the closed isomer is more stable by 11 kcal mol−1 (Gibbs free energy, ΔG) according to our gas-phase calculations. Similarly, the closed form of (ZnChl)2Fc is more stable by ca. 19 kcal mol−1. The dihedral angle is reduced from 141.8 to 12.1° in the closed form,while the angles between the Cp and the chlorin planes are only slightly reduced (40.9/42.8° in the closed form vs 45.9/46.0° in the open form). Interestingly, a very short intermetallic distance (3.30 Å) and short C···N/C···C distances (∼3.2 Å) support strong interaction between the two chlorin fragments in the closed form. C

DOI: 10.1021/acs.inorgchem.6b03158 Inorg. Chem. XXXX, XXX, XXX−XXX

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BODIPYs are shown in Figure 8 and Figure S31 in the Supporting Information. The data are summarized in Table 1. The room-temperature absorption spectra of MChlFc and (MChl)2Fc are similar. The most important differences are the higher Qy band intensities relative to the Soret bands in the dimeric species, in comparison to the corresponding monomers. A small blue shift of the Soret bands (5−10 nm) and minor broadening of both the Soret and Qy bands of the dimers are also seen in the dimers. The order of the Qy bands is as expected on the basis of previous reports and is the same for both monomers and dimers: the most blue-shifted bands are for the Pd species and the most red-shifted bands are for the free base macrocycles. The Ni(II) chlorins had the most broadened spectra, which is in line with previous reports on Ni(II) porphyrins and chlorins and is caused by macrocycle distortion.46 Additionally, the blue shift of the Soret band of (NiChl)2Fc in comparison to NiChlFc was negligible (2 nm), again showing that the Ni chelates behaved anomalously. The UV−vis absorption spectrum of (ZnChl)2Fc was modestly temperature dependent (Figure 7). The roomtemperature and 85 °C spectra were essentially superimposable, with only small changes observed in the Qy region. However, when the solution was cooled to −85 °C, the Soret band redshifted by 12 nm and the Qy band blue-shifted by ∼1 nm. Even more importantly, the Soret to Qy ratio decreased dramatically, from 4.8 to 2.4. These data support the conclusions of the NMR experiments that at low temperatures the chlorin dimers adopt a conformation different from that of the roomtemperature structure. However, the dimers aggregate at low temperature, as seen from the NMR spectra, and both the aggregation and the adoption of a cofacial arrangement by the chlorin rings are expected to affect the absorption spectra. The UV−vis absorption spectra of the monomeric and dimeric BODIPYs were similar (Figure 8). The most prominent features were sharp bands at λabs 507 nm and λabs 512 nm for BODIPYFc and BODIPY2Fc, respectively, assigned to the 4,4difluoro-4-bora-3a,4a-diaza-s-indacene core. Additionally, broad, low-intensity bands are seen for both chromophores in the red, stretching all the way to the near-infrared. These are attributed to charge-transfer bands on the basis of similar spectral features observed in other Fc-substituted BODIPYs.12 Free base chlorins and BODIPYs without Fc are usually strongly fluorescent (Φ ≈ 20−30%, 32% for chlorophyll a), as are, to a smaller extent, Zn chlorins (Φ ≈ 5%).42,47,48 The covalent attachment of an Fc unit resulted in essentially complete quenching of the fluorescence of these chromophores, presumably due to photoinduced electron transfer (PeT) from the Fc to the excited state chromophore. The driving force (ΔE) for electron transfer was calculated for a free red base chlorin (eq 1). Eox 1/2(D) and E1/2(A) are the oxidation and reduction potentials (vs NHE) of the donor (Fc, 0.65 eV, Table 2) and the acceptor (chlorin, −1.17 eV), respectively. Eexc(A) is the excited state energy of the acceptor (chlorin singlet), which was approximated with the higher-energy maximum of the emission spectrum (639 nm, 1.94 eV). ΔECoul is the attraction between the radical ion pair resulting from PeT. The contribution of this term is usually small.49 Its lower limit was estimated by an established value for complete charge separation in acetonitrile (0.06 eV). As we work in CH2Cl2, which has a lower ε, we expect this term to be larger. These approximations give ΔE = −0.18 eV (−0.12 eV without the last term), indicating that electron transfer is possible.

Scheme 2. Preparation of the Fc-Linked Chlorin Dimer (ZnChl)2Fc and its Transformation into (Chl)2Fc and (MChl)2Fc (M = Cu, Ni, Pd)

Scheme 3. Preparation of the BODIPYs

UV−Vis Absorption and Emission Spectroscopy. The spectra of the monomeric and dimeric Fc chlorins are shown in Figures 6 and 7 and in Figures S27−S30 in the Supporting Information, while those for the monomeric and dimeric D

DOI: 10.1021/acs.inorgchem.6b03158 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 2. X-ray structure of BODIPYFc: perspective view with ellipsoids at the 50% probability level. Selected distances (Å) and angles (deg): C5− C10 1.460(4), B1−N1 1.540(4), B1−N2 1.532(4), B1−F1 1.389(4), B1−F2 1.391(4), N1−B1−N2 106.3(2).

Figure 3. Aromatic regions of the 1H NMR spectra of the monomeric (top) and dimeric (bottom) Fc chlorins NiChlFc and (NiChl)2Fc (left) and ZnChlFc and (ZnChl)2Fc (right).

Figure 4. Variable-temperature 1H NMR spectra (aromatic region) of (ZnChl)2Fc in toluene-d8. ox red ΔE = E1/2 (D) − E1/2 (A) − Eexc(A) − ECoul

Further support for fluorescence quenching by PeT was provided by the recovery of the chlorin and BODIPY emission

(1) E

DOI: 10.1021/acs.inorgchem.6b03158 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 5. Calculated rotamers of (ZnChl)2Fc at the M06-2X/6-311G** level of theory: (a) top view of the open form and (b) top and (c) side views of the closed form.

Figure 6. UV−vis spectra of (left) MChlFc and (right) (MChl)2Fc in CH2Cl2 at room temperature.

Figure 7. UV−vis spectra of (ZnChl)2Fc at different temperatures in toluene.

Figure 8. UV−vis absorption spectra of monomeric and dimeric BODIPYs in CH2Cl2.

F

DOI: 10.1021/acs.inorgchem.6b03158 Inorg. Chem. XXXX, XXX, XXX−XXX

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general less emissive than their monomeric analogues, presumably due to the short chlorin−chlorin distance in these compounds, which results in self-quenching. Electrochemistry. Cyclic voltammetry of all compounds was measured, and the results are summarized in Table 2 and in Figures S33 and S34 in the Supporting Information. The compounds show complex behavior and undergo multiple redox processes. Monomeric chlorins have two reductions, assigned to macrocycle-based processes on the basis of comparison with simple free base chlorins.50 The first reduction is usually reversible. There are two macrocycle-based oxidations in addition to the first oxidation around 0 eV, which is Fcbased. Chlorin dimers have more complicated voltammograms, exhibiting stepwise oxidations with up to five well-resolved peaks (see e.g. (Chl)2Fc). This suggests that there is electronic communication between the chlorin macrocycles mediated by the Fc unit. Oxidation of Fe(II) to Fe(III) is observed at 0.02− 0.10 eV but can also be at as lower potentials: e.g. −0.02 and −0.04 eV for (CuChl)2Fc and (ZnChl)2Fc, respectively. The order of the oxidation and reduction potentials follows the order expected on the basis of the electron-withdrawing properties of the central metal ion in the chlorin (Zn < Cu < Pd).51 The Ni chlorins behaved differently from the other metalated and free base chlorins: e.g., NiChlFc had a reduction potential at the most negative value (at −1.88 eV), which might be due to structural factors. For the monomeric and dimeric Zn chelates, a sharp peak is observed for the anodic scan at +0.06 V, which is probably a stripping effect: i.e., release of metal from deposited material during irreversible oxidative scans. BODIPYFc has fully reversible first oxidation and reduction peaks at 0.3 and −1.32 eV, respectively. Only the second oxidation at 1.30 eV is irreversible. BODIPY2Fc has five peaks in all in the CV (two reductions and three oxidations), all of which are irreversible. Extensive decomposition and material deposition onto the electrode were observed in this case. The spectroelectrochemical investigations of ZnChl Fc and (ZnChl)2Fc were inconclusive. Studies with Bu4NPF6 as electrolyte were not satisfactory, most probably because of the small separation between the oxidation processes. Using the bulkier NaBARF (BARF = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) as the electrolyte, the first two oxidation processes could be separated. However, UV−vis absorption spectroscopy showed substantial broadening of the Soret band and the slow disappearance of the Q band (Figures S45−S48 in the Supporting Information) for both compounds, suggesting the decomposition of these species.

Table 1. Photophysical Properties of Fc Chlorins and BODIPYs compound

λ(Soret), nma

ZnChlFc ChlFc NiChlFc PdChlFc CuChlFc (ZnChl)2Fc (Chl)2Fc (NiChl)2Fc (PdChl)2Fc (CuChl)2Fc ChlFc+ d (Chl)2Fc+ d BODIPYFc BODIPY2Fc BODIPYFc+ d BODIPY2Fc+ d

410 407 410 404 408 400 399 408 399 401 412 394 359, 506 362, 513 504 500, 402

I(λS)/ I(λQ)b

λ(Qy), nma 615 647 611 597 610 615 647 612 598 612 537, 616, 768e 636

4.82 5.39 3.19 3.42 3.77 4.83 6.32 3.23 3.36 3.79 8.1

λem, nma,c (637f)

(639f)

639 640

488, 516 488, 519

a

Recorded in CH2Cl2 at room temperature. bDetermined by integration of the peak area. cExcitation was carried out at the Soret band. dObtained by addition of Fe(ClO4)3 to the sample. eMultiple bands, not regular chlorin Q bands. fPossibly due to contaminant, as it is at higher energy than the chlorin absorption and is very weak.

Table 2. Cyclic Voltammetry Data for the Fc-Substituted Chlorins and BODIPYs compound

reduction,a eV

(Chl)2Fc (NiChl)2Fc

−2.32, −1.79 −2.22, −1.80b −1.88 −2.31, −1.83b −2.35, −1.85b −2.31, −2.12,d −2.01,d −0.04b −2.17, −1.74b −1.80b

(PdChl)2Fc (CuChl)2Fc BODIPYFc BODIPY2Fc

−2.33, −1.80b −1.85,b −0.02b −1.32b −1.74, −1.31

Fc

ZnChl ChlFc NiChlFc PdChlFc CuChlFc (ZnChl)2Fc

b

oxidation,a eV b

0.02, 0.02,b 0.07,b 0.06,b 0.04,b 0.18,b

0.24,b 0.73c 0.51, 0.90 0.39,b 0.77, 1.12 0.53, 0.98, 1.13, 1.21 0.37,b 0.85, 1.11, 1.24 0.33,b 0.74, 0.94

0.008, 0.41, 0.61, 0.90, 1.09 0.09,b 0.26,b 0.43,b 0.82, 1.12 0.10,b 0.30, 0.60 0.32, 0.57, 0.94,e 1.16 0.30,b 1.30 0.35, 0.59, 1.16e

a

Measured for 1 mM solutions of the analyte in CH2Cl2 (0.1 M NBu4PF6) with a glassy-carbon electrode and ν = 100 mV/s. All potentials are given versus Fc+/0. bPeak is reversible; reported value corresponds to E1/2 = (Epa + Epc)/2. cPeak features large tail. dTwo peaks that are not well-resolved and are very broad. eShoulder.

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CONCLUSIONS The syntheses of free base and metalated ferrocene-substituted chlorins and the analogous BODIPY dyes are reported. Chlorin macrocyclizations resulted from condensing a tetrahydrodipyrrin with ferrocenyl 1-bromo-9-formyldipyrromethanes or a formylated tetrahydrodipyrromethane with ferrocenyl 1-bromodipyrromethanes. The latter method gave excellent yields of both monomeric and dimeric chlorins, highlighting the way the stabilities of dipyrromethane derivatives can affect macrocyclization yields. The UV−vis absorption spectra of the dimeric species were similar to those of the monomers, with only small differences noted, mostly in the Soret region. The fluorescence emissions of all Fc-substituted compounds were quenched. Emission could be partially restored by chemical oxidation of the Fe(II) center in Fc, thus suggesting that quenching proceeds through electron transfer to the

upon oxidation of the Fe(II) center. Fe(II) was oxidized to Fe(III) in ChlFc and (Chl)2Fc with Fe(ClO4)3. Fe(III) is a strong enough oxidant to affect the Fe(II) → Fe(III) transformation (0.77 V (in water)) without oxidizing the chromophores. The dark green solutions turned dark red upon the addition of Fe(ClO4)3. Upon oxidation the Soret bands of both the monomeric and the dimeric chlorins red-shifted to a small extent without broadening significantly. Under the same conditions, the Qy bands broadened and were bathochromically shifted and their short-wavelength satellites intensified (Figure S32 in the Supporting Information). Oxidation has a strong electronic effect, in addition to modestly decreasing the Cp−Cp distance; the significance of the latter is expected to be higher for dimers than for monomers. Dimeric chlorins were in G

DOI: 10.1021/acs.inorgchem.6b03158 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

108.32, 106.75, 106.69, 89.39, 69.60, 69.23, 68.87, 68.86, 68.74, 68.72, 68.69, 68.43, 38.31, 38.26. HRMS: calcd for C30H26FeN4O2Na [M + Na]+ 553.12978, found 553.12958. General Procedure for Macrocyclization. Step 1: Bromination. A sample of dipyrromethane or formyl dipyrromethane (1 equiv) in dry THF (∼10 mmol/mL) was cooled to −78 °C. To this solution was added 1 equiv (for 2 or 3) or 2 equiv (for 8 or 9) of NBS dissolved in THF dropwise. The reaction mixture was stirred for 30 min, during which time it was slowly warmed to ca. 0 °C. Stirring was continued at this temperature for an additional 15 min. The reaction was quenched by adding 30 mL of brine, and the mixture was to warmed to room temperature. The phases were separated, and the aqueous layer was extracted twice with diethyl ether. The combined organic layers were washed with brine and dried over MgSO4. The solvent was removed under reduced pressure (Caution! The water bath temperature should not exceed 25 °C.) to give the crude product, which was directly used in the next step without additional purification. Step 2: Macrocyclization. Caution! All manipulations should be performed with the exclusion of light. To a solution of bromodipyrromethane or 1-bromo-9-formyldipyrromethane (1 equiv for monomeric or 0.5 equiv for dimeric species) and 5 (1 equiv) or 5CHO (1 equiv) in dry CH2Cl2 (∼10 mM) was added a solution of 5 equiv of ptoluenesulfonic acid monohydrate in MeOH. The solution was stirred for 30 min, and the reaction was quenched by the addition of 10 equiv of TMPi (2,2,6,6-tetramethylpiperidine). The volatile components were removed under reduced pressure (Caution! The water bath temperature should not exceed 25 °C.), and the solid residue was redissolved in dry CH3CN (∼0.5 mmol/mL). Then, 25 equiv of TMPi, 15 equiv of Zn(OAc)2, and 3 equiv of AgOTf were added in that order. After this, the reaction mixture was refluxed for 16−24 h in the dark open to the air. During this time a dark gray to black suspension was formed. The reaction mixture was cooled to room temperature. The mixture was filtered through a silica pad which was thoroughly washed with CH2Cl2. The removal of the solvents gave a dark green to black solid, which was purified by column chromatography on silica gel using a 1/1 mixture of CH2Cl2 and hexane as the eluent. Dark green solids were obtained. ZnChlFc: Synthesis A, Starting from 3. Bromination was performed on 90 mg (0.31 mmol) of 3 with 55 mg (0.31 mmol) of NBS. During macrocyclization 58 mg (0.31 mmol) of 5, 295 mg (1.55 mmol) of ptoluenesulfonic acid monohydrate, 0.44 g (3.10 mmol) and 1.09 g (7.75 mmol) of TMPi, 0.85 g (4.65 mmol) of Zn(OAc)2, and 240 mg (0.93 mmol) of AgOTf were used. Rf (CH2Cl2/hexane, 1/1) = 0.52. Yield: 12%, 21 mg. ZnChlFc: Synthesis B, Starting from 2. Bromination was performed on 40 mg (0.15 mmol) of 2 with 27 mg (0.15 mmol) of NBS. During macrocyclization 33 mg (0.15 mmol) of 5CHO, 144 mg (0.76 mmol) of p-toluenesulfonic acid monohydrate, 0.21 g (1.52 mmol) and 0.54 g (3.8 mmol) of TMPi, 0.42 g (2.3 mmol) of Zn(OAc)2, and 117 mg (0.45 mmol) of AgOTf were used. Rf (CH2Cl2/hexane, 1/1) = 0.52. Yield: 43%, 28 mg. 1H NMR (400 MHz, CDCl3): δ 9.87 (d, 3JH,H = 4.5 Hz, 1H, β-pyrrole), 9.80 (d, 3JH,H = 4.2 Hz, 1H, β-pyrrole), 9.45 (s, 1H, meso-H), 8.97 (d, 3JH,H = 4.3 Hz, 1H, β-pyrrole), 8.79 (d, 3JH,H = 4.3 Hz, 1H, β-pyrrole), 8.68 (d, 3JH,H = 4.2 Hz, 1H, β-pyrrole), 8.53 (d, 3 JH,H = 4.5 Hz, 1H, β-pyrrole), 8.50 (s, 1H, meso-H), 8.50 (s, 1H, meso-H), 5.46−5.39 (m, 2H, Fc), 4.79−4.71 (m, 2H, Fc), 4.39 (s, 2H, CH2), 4.23 (s, 5H, Fc), 1.99 (s, 6H, CH3). 13C NMR (101 MHz, CDCl3): δ 170.58, 158.65, 153.89, 152.22, 148.10, 146.59, 145.46, 145.35, 133.70, 132.55, 129.52, 127.30, 126.97, 125.74, 121.20, 109.64, 96.84, 94.04, 90.04, 70.54, 68.23, 50.10, 45.22, 30.78. HRMS: calcd for C32H26ZnFeN4 ([M]+) 586.0794, found 586.0788. (ZnChl)2Fc: Synthesis A, Starting from 9. Bromination was performed starting from 24 mg (0.045 mmol) of 9 with 16 mg (0.090 mmol) of NBS. During macrocyclization 17 mg (0.091 mmol) of 5, 86 mg (0.45 mmol) of p-toluenesulfonic acid monohydrate, 0.127 g (0.67 mmol) and 0.32 g (2.25 mmol) of TMPi, 0.247 g (1.35 mmol) of Zn(OAc)2, and 69 mg (0.27 mmol) of AgOTf were used. Rf (CH2Cl2/hexane, 1/1) = 0.41. Yield: 3.8%, 2 mg. (ZnChl)2Fc: Synthesis B, Starting from 8. Bromination was performed on 145 mg (0.31 mmol) of 8 with 109 mg (0.61 mmol)

chromophore from the ferrocene. The presence of the redoxactive Fc and one or two hydroporphyrin units resulted in rich redox chemistry for MChlFc and (MChl)2Fc. Taken together, Fc chlorins are interesting as rare red-absorbing, redox-active systems with potential as models of electron transfer in photosynthesis. Designs wherein the Fc unit and the chlorin or the BODIPY are connected by a linker are conceivable and could be useful in controlling the electron transfer. Applications of these or similar compounds as fluorescent sensors for redox sensing are conceivable, and the multiple well-resolved redox states of some of these compounds make them interesting as molecular memory devices.

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EXPERIMENTAL SECTION

All reactions were performed under Ar using Schlenk techniques if not stated otherwise. Diethyl ether and THF were freshly distilled from Na/benzophenone prior to use, CH2Cl2 was distilled from CaH2. 1H and 13C NMR spectra were recorded on a 400 MHz spectrometer (Agilent and JEOL) unless noted otherwise. Chemical shifts (ppm) are referenced to the internal signal of residual solvent protons. Highresolution mass spectral analyses (HRMS) were performed at the Organisch Chemisches Institut WWU Münster. Compounds 2,20 5,38 5CHO,39 and 840 were prepared according to literature procedures. The X-ray crystal structure was solved using direct methods in the monoclinic space group P21/n (No. 14) with four molecules in the unit cell. General Procedure for Vilsmeier Formylation. A sample of 2 or 8 (1 equiv) was dissolved in dry DMF (10 mL), and the solution was cooled in an ice−water bath. In a separate vial, POCl3 (1 or 2 equiv, respectively) was added to dry DMF (5 mL), and this mixture was stirred for 10 min, after which it was transferred to the dipyrromethane solution. The reaction mixture was warmed to room temperature and was then heated for 2−3 h until no more starting material could be detected by TLC analysis. The reaction was quenched by the addition of aqueous Na2CO3 (1 M), and the solution was diluted with diethyl ether. The phases were separated, and the aqueous layer was extracted three times with diethyl ether. The combined organic phase was washed three times with brine, dried (MgSO4), and concentrated. Column chromatography on silica gel using CH2Cl2/hexane (1/1) as eluent gave the products as pale yellow solids. 3. The compound was prepared starting from 0.320 g (1.22 mmol) of 2 and 187 mg (1.22 mmol) of POCl3. Rf (EtOAc/pentane, 1/4) = 0.1. Yield: 25%, 90 mg. 1H NMR (400 MHz, CDCl3): δ 9.42 (s, 1H, COH), 9.35 (bs, 1H, NH), 8.02 (bs, 1H, NH), 6.96−6.84 (m, 1H, pyrrole), 6.70−6.67 (m, 1H, pyrrole), 6.13 (d, 3JH,H = 6.1 Hz, 1H, pyrrole), 6.00−5.98 (m, 1H, pyrrole), 5.23 (s, 1H, CH), 4.21−4.19 (m, 2H, Fc), 4.13 (s, 5H, Fc), 4.05 (m, 2H, Fc). 13C NMR (101 MHz, CDCl3): δ 178.70, 142.56, 132.03, 131.33, 121.56, 117.37, 110.27, 108.57, 107.08, 69.13, 68.31, 68.20, 68.11, 67.82, 38.33. HRMS: calcd for C20H18FeN2ONa [M + Na]+ 381.06609, found 381.06604. 9. The compound was prepared starting from 0.10 g (0.21 mmol) of 8 and 65 mg (0.042 mmol) of POCl3. Rf (5% MeOH in Et2O) = 0.63. Yield: 22%, 24 mg. The product was obtained as a mixture of diastereomers. 1H NMR (400 MHz, CDCl3): δ 10.00 (bs, 2H, NH isomer 1), 9.87 (bs, 2H, NH isomer 2), 9.30 (s, 4H, CHO isomers 1 + 2), 8.44 (bs, 2H, NH isomer 1), 8.41 (bs, 2H, NH isomer 2), 6.87 (t, 3 JH,H = 4.1,4JH,H = 2.2 Hz, 2H, pyrrole isomer 1), 6.86 (t, 3JH,H = 4.1,3JH,H = 2.2 Hz, 2H, pyrrole isomer 2), 6.67 (dd, 3JH,H = 4.1,4JH,H = 2.6 Hz, 2H, pyrrole isomer 1), 6.63 (dd, 3JH,H = 4.1,4JH,H = 2.6 Hz, 2H, pyrrole isomer 2), 6.11 (dd, 3JH,H = 3 Hz, 2H, pyrrole isomer 1), 6.10 (dd, 3JH,H = 3 Hz, 2H, pyrrole isomer 2), 6.05 (dd, 3JH,H = 3 Hz, 2H, pyrrole isomer 1), 6.05 (dd, 3JH,H = 3 Hz, 2H, pyrrole isomer 2), 5.99− 5.93 (m, 4H, pyrrole isomers 1 + 2), 5.03 (s, 2H, CH isomer 1), 4.99 (s, 2H, CH isomer 2), 4.03−3.98 (m, 5H, Fc isomers 1 + 2), 3.97− 3.95 (m, 1H, Fc isomers 1 + 2), 3.94−3.90 (m, 2H, Fc isomers 1 + 2). 13 C NMR (101 MHz, CDCl3): δ 178.80, 144.05, 143.81, 131.74, 131.66, 131.63, 131.49, 122.79, 117.39, 117.18, 110.19, 110.14, 108.33, H

DOI: 10.1021/acs.inorgchem.6b03158 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

JH,H = 4.3 Hz, 2H, β-pyrrole), 8.20 (d, 3JH,H = 4.6 Hz, 2H, β-pyrrole), 5.54 (d, 3JH,H = 1.6 Hz, 4H, Fc), 4.91 (d, 3JH,H = 1.6 Hz, 4H, Fc), 4.48 (s, 4H, CH2), 2.02 (s, 12H, CH3), − 1.51 (bs, 2H, NH), − 2.20 (bs, 2H, NH). 13C NMR (101 MHz, CD2Cl2): δ 175.34, 162.39, 153.67, 149.16, 141.09, 138.18, 136.08, 133.15, 131.70, 131.55, 128.32, 128.03, 123.09, 122.38, 118.40, 107.19, 96.63, 93.97, 90.35, 79.00, 71.72, 51.75, 46.03, 30.73. HRMS: calcd for C54H47FeN8 ([M + H]+) 863.3269, found 863.3249. General Procedure for Preparation of Cu Chlorins. To a solution containing 1 equiv of the free base chlorin in CH2Cl2 (15 mL) was added 5 equiv (ChlFc) or 10 equiv of Cu(OAc)2 ((Chl)2Fc). The reaction mixture was stirred at room temperature for 12 h, after which the reaction mixture was directly poured onto a silica chromatography column. Elution with a mixture of CH2Cl2 and hexane (1/1) gave the products as bright turquoise solids after the removal of the solvents. CuChlFc. The reaction was performed using 13 mg (0.025 mmol) of ChlFc. Rf (CH2Cl2/hexane, 1/1) = 0.61. Yield: 97%, 14 mg. HRMS: calcd for C32H26FeCuN4 ([M]+) 585.0799, found 585.0799. (CuChl)2Fc. The reaction was performed using 10 mg (0.012 mmol) of (Chl)2Fc. Rf (CH2Cl2/hexane, 1/1) = 0.58. Yield: 50%, 6 mg. HRMS: calcd for C54H42FeCu2N8 ([M]+) 986.1454, found 986.1419. General Procedure for the Preparation of Pd- and Nichlorins. To a solution of 1 equiv of free base chlorin in pyridine (5 mL) was added 5 equiv (ChlFc) or 10 equiv ((Chl)2Fc) of Pd(acac)2 or Ni(OAc)2·4H2O. The reaction mixture was irradiated in a microwave reactor for 30 min at 180 °C. After this time the solvent was removed under reduced pressure and the residue was extracted with CH2Cl2. Column chromatography on silica gel using a mixture of CH2Cl2 and hexane (1/1) as eluent gave bright pink (Pd) or green (Ni) solids after solvent removal. PdChlFc. The reaction was performed using 13 mg (0.025 mmol) of ChlFc. Rf (CH2Cl2/hexane, 1/1) = 0.67. Yield: 30%, 4.8 mg. 1H NMR (400 MHz, CD2Cl2): δ 9.86 (d, 3JH,H = 4.7 Hz, 1H, β-pyrrole), 9.79 (d, 3 JH,H = 4.8 Hz, 1H, β-pyrrole), 9.62 (s, 1H, meso-H), 8.93 (d, 3JH,H = 4.5 Hz, 1H, β-pyrrole), 8.88 (d, 3JH,H = 4.5 Hz, 1H), 8.70 (d, 3JH,H = 4.8 Hz, 1H, β-pyrrole), 8.69 (s, 1H, meso-H), 8.65 (s, 1H, meso-H), 8.59 (d, 3JH,H = 4.8 Hz, 1H, β-pyrrole), 5.37 (dd, 3JH,H = 1.8 Hz, 2H, Fc), 4.78 (dd, 3JH,H = 1.8 Hz, 2H, Fc), 4.54 (s, 2H, CH2), 4.22 (s, 5H, Fc), 2.00 (s, 6H, CH3). 13C NMR (101 MHz, CD2Cl2): δ 161.50, 149.86, 145.34, 143.86, 139.30, 137.78, 137.46, 137.09, 132.63, 131.50, 128.27, 126.76, 126.59, 125.66, 121.56, 109.96, 97.62, 95.23, 88.71, 76.44, 70.51, 68.50, 49.80, 45.43, 30.34. HRMS: calcd for C32H26FePdN4 ([M]+) 628.0550, found 628.0555. (PdChl)2Fc. The reaction was performed using 6 mg (0.007 mmol) of (Chl)2Fc. Rf (CH2Cl2/hexane, 1/1) = 0.73. Yield: 20%, 1.7 mg. 1H NMR (400 MHz, CDCl3): δ 9.70−9.62 (m, 4H, β-pyrrole), 9.10 (s, 2H, meso-H), 8.66 (d, 3JH,H = 4.3 Hz, 2H, β-pyrrole), 8.57 (d, 3JH,H = 4.5 Hz, 2H, β-pyrrole), 8.54 (s, 2H, meso-H), 8.35 (s, 2H, meso-H), 8.10 (d, 3JH,H = 4.6 Hz, 2H, β-pyrrole), 8.03 (d, 3JH,H = 4.6 Hz, 2H, βpyrrole), 5.40 (t, J = 1.7 Hz, 4H, Fc), 4.79 (d, J = 1.7 Hz, 4H, Fc), 4.38 (s, 4H, CH2), 1.98 (s, 12H, CH3). 13C NMR (101 MHz, CDCl3): δ 154.09, 149.23, 145.14, 143.74, 137.93, 137.21, 136.84, 132.51, 131.33, 129.07, 127.88, 126.50, 126.39, 125.64, 125.52, 110.08, 97.58, 95.18, 90.68, 79.03, 71.00, 49.94, 45.46, 29.62. HRMS: calcd for C54H42FePd2N8 ([M]+) 1070.09755, found 1070.09990. NiChlFc. The reaction was performed using 7 mg (0.013 mmol) of ChlFc. Rf (CH2Cl2/hexane, 1/1) = 0.54. Yield: 80%, 6.2 mg. 1H NMR (400 MHz, CDCl3): δ 9.34 (d, 3JH,H = 4.7 Hz, 1H, β-pyrrole), 9.30 (d, 3 JH,H = 4.6 Hz, 1H, β-pyrrole), 9.08 (s, 1H, meso-H), 8.70 (d, 3JH,H = 4.5 Hz, 1H, β-pyrrole), 8.56 (d, 3JH,H = 4.5 Hz, 1H, β-pyrrole), 8.39 (d, 3 JH,H = 4.6 Hz, 1H, β-pyrrole), 8.29 (d, 3JH,H = 4.7 Hz, 1H, β-pyrrole), 8.06 (s, 1H, meso-H), 8.01 (s, 1H, meso-H), 5.08 (dd, J = 1.9 Hz, 2H, Fc), 4.64 (dd, J = 1.8 Hz, 2H, Fc), 4.05−4.03 (m, 7H, Fc+CH2), 1.79 (s, 6H, CH3). 13C NMR (101 MHz, CDCl3): δ 161.06, 149.92, 146.80, 145.29, 141.47, 139.14, 138.80, 138.09, 133.77, 132.72, 128.65, 127.64, 127.20, 126.40, 119.72, 108.75, 95.78, 93.31, 87.36, 75.54, 70.34, 68.69, 50.11, 45.98, 28.41. HRMS: calcd for C32H26FeN4Ni ([M]+) 580.08549, found 580.08545. (NiChl)2Fc. The reaction was performed using 10 mg (0.012 mmol) of (Chl)2Fc. Rf (CH2Cl2) = 0.71. Yield: 30%, 3 mg. 1H NMR (400

of NBS. During macrocyclization 66 mg (0.31 mmol) of 5CHO, 291 mg (1.5 mmol) of p-toluenesulfonic acid monohydrate, 0.43 g (3.06 mmol) and 1.08 g (7.61 mmol) of TMPi, 0.84 g (4.6 mmol) of Zn(OAc)2, and 235 mg (0.92 mmol) of AgOTf were used. Rf (CH2Cl2/hexane, 1/1) = 0.41. Yield: 15%, 19 mg. 1H NMR (500 MHz, toluene-d8): δ 10.06 (bs, 2H, β-pyrrole), 10.00 (bs, 2H, βpyrrole), 9.06 (s, 2H, meso-H), 8.73 (d, 3JH,H = 4.2 Hz, 2H, β-pyrrole), 8.56 (d, 3JH,H = 4.2 Hz, 2H, β-pyrrole), 8.36 (d, 3JH,H = 4.2 Hz, 2H, βpyrrole), 8.34 (s, 2H, meso-H), 8.16 (d, 3JH,H = 4.2 Hz, 2H, β-pyrrole), 8.14 (s, 2H, meso-H), 5.51 (dd, J = 1.8 Hz, 4H, Fc), 4.65 (dd, J = 1.7 Hz, 4H, Fc), 3.98 (s, 4H, CH2), 1.79 (s, 12H, CH3). 13C NMR (101 MHz, toluene-d8): δ 169.04, 157.23, 153.37, 151.41, 148.03, 147.05, 144.64, 144.19, 136.89, 133.19, 131.66, 126.52, 126.29, 125.28, 119.77, 108.57, 96.10, 93.78, 92.68, 79.32, 70.07, 49.65, 44.53, 30.43. HRMS: calcd for C54H42Zn2FeN8 ([M]+) 990.1418, found 990.1411. General Procedure for BODIPY Preparation. To a solution of 2 or 8 in CH2Cl2 (25 mL) was added 1 or 2 equiv of DDQ in CH2Cl2 (5 mL) as a single portion. The reaction mixture immediately changed color to dark brown. Stirring was continued for 5 min at room temperature. Then DIPEA (3 mL) was added and stirring was continued for another 5 min, after which BF3·OEt2 (3 mL) was added. The reaction was monitored by TLC. Typically, no further changes were observed after 15 min, and at this point the reaction was quenched by the addition of brine. The mixture was diluted with Et2O and was washed three times with water and twice with brine. The organic layer was dried over MgSO4. The solid residue after the removal of the solvent was chromatographed on silica gel. BODIPYFc. The reaction was performed using 25 mg (0.12 mmol) 2. Rf (Et2O) = 0.8. Yield: 62%, 18 mg. 1H NMR (400 MHz, CDCl3): δ 7.85 (s, 2H, pyrrole), 7.65 (d, 3JH,H = 4.1 Hz, 2H, pyrrole), 6.58−6.47 (m, 2H, pyrrole), 4.97 (t, J = 1.9 Hz, 2H, Fc), 4.75 (t, J = 1.9 Hz, 2H, Fc), 4.21 (s, 5H, Fc). 19F NMR (376 MHz, CDCl3): δ −145.84 (m). 13 C NMR (101 MHz, CDCl3): δ 146.51, 140.95, 134.86, 129.94, 117.49, 79.34, 74.00, 72.18, 71.69. HRMS: calcd for C19H16BF2FeN2 ([M + H]+) 377.0722, found 377.0747. BODIPY2Fc. The reaction was performed using 78 mg (0.16 mmol) of 8. Rf (Et2O) = 0.54. Yield: 3%, 3 mg. 1H NMR (400 MHz, CDCl3): δ 7.86 (s, 4H, pyrrole), 7.54 (d, 3JHH = 3.3 Hz, 4H, pyrrole), 6.48 (m, 4H, pyrrole), 4.87 (s, 4H, Fc), 4.75 (s, 4H, Fc). 19F NMR (376 MHz, CDCl3): δ −145.79 (m). 13C NMR (101 MHz, CDCl3): δ 148.18, 142.38, 134.79, 130.22, 118.11, 81.54, 76.70, 74.85. Repeated attempts at HRMS analysis were unsuccessful due to sample decomposition. General Procedure for the Preparation of Free Base Chlorins. To a solution of the Zn chlorin in dry CH2Cl2 (∼0.3 M) was added TFA (∼0.25 mL) as a single portion. The reaction mixture was stirred at room temperature for 20 min, after which the reaction was quenched by the addition of Et3N (1 mL), yielding a dark green to black solution. This was directly loaded onto a silica gel column. The product was eluted with a mixture of CH2Cl2 and hexane (1/1). Removal of the solvent under reduced pressure gave spectroscopically clean products as dark green solids. ChlFc. The reaction was performed using 10 mg (0.017 mmol) of ZnChlFc. Rf (CH2Cl2/hexane, 1/1) = 0.44. Yield: 70%, 6.3 mg. 1H NMR (400 MHz, CDCl3): δ 10.07 (d, 3JH,H = 4.7 Hz, 1H, β-pyrrole), 9.78 (s, 1H, meso-H), 9.70 (d,3JH,H = 4.3 Hz, 1H, β-pyrrole), 9.17 (d, 3 JH,H = 4.5 Hz, 1H, β-pyrrole), 8.94 (d, 3JH,H = 4.3 Hz, 1H, β-pyrrole), 8.94 (s, 1H, meso-H), 8.87 (d, 3JH,H = 4.5 Hz, 1H, β-pyrrole), 8.83 (d, 3 JH,H = 4.7 Hz, 1H, β-pyrrole), 8.80 (s, 1H, meso-H), 5.53 (m, 2H, Fc), 4.80 (m, 2H, Fc), 4.58 (s, 2H, CH2), 4.23 (s, 5H, Fc), 2.04 (s, 6H, CH3), − 1.28 (bs, 1H, NH), − 1.89 (bs, 1H, NH). 13C NMR (101 MHz, CDCl3): δ 175.19, 162.11, 153.67, 149.40, 141.24, 138.42, 136.09, 133.41, 131.98, 131.68, 128.48, 128.24, 123.23, 122.49, 119.48, 107.60, 96.79, 93.86, 76.50, 70.64, 68.76, 52.00, 31.03. HRMS: calcd for C32H29FeN4 ([M + H]+) 525.1737, found 525.1739. (Chl)2Fc. The reaction was performed using 8 mg (0.0081 mmol) of (ZnChl)2Fc. Rf (CH2Cl2) = 0.7. Yield: 70%, 5 mg. 1H NMR (400 MHz, CD2Cl2): δ 9.99 (d, 3JH,H = 4.6 Hz, 2H, β-pyrrole), 9.63 (d, 3JH,H = 4.3 Hz, 2H, β-pyrrole), 9.50 (s, 2H, meso-H), 9.07 (dd, 3JH,H = 4.5, 4 JH,H = 1.6 Hz, 2H, β-pyrrole), 8.87 (dd, 3JH,H = 4.5, 4JH,H = 1.3 Hz, 2H, β-pyrrole), 8.83 (s, 2H, β-pyrrole), 8.70 (s, 2H, meso-H), 8.49 (d,

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DOI: 10.1021/acs.inorgchem.6b03158 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry MHz, CDCl3): δ 9.20 (d, 3JH,H = 4.8 Hz, 2H, β-pyrrole), 9.18 (d, 3JH,H = 4.7 Hz, 2H, β-pyrrole), 8.97 (s, 2H, meso-H), 8.65 (d, 3JH,H = 4.8 Hz, 2H, β-pyrrole), 8.37 (d, 3JH,H = 4.5 Hz, 2H, β-pyrrole), 8.33 (d, 3 JH,H = 4.5 Hz, 2H, β-pyrrole), 8.10 (d, 3JH,H = 4.7 Hz, 2H, β-pyrrole), 8.01 (s, 2H, meso-H), 7.98 (s, 2H, meso-H), 5.02 (s, 4H, Fc), 4.38 (s, 4H, Fc), 4.04 (s, 4H, CH2), 1.81 (s, 12H, CH3). 13C NMR (101 MHz, CDCl3): δ 161.05, 149.98, 146.80, 145.28, 141.37, 139.11, 138.09, 133.66, 132.70, 128.44, 127.72, 127.18, 126.52, 118.96, 108.77, 95.79, 93.39, 88.11, 72.48, 50.13, 45.96, 28.45. HRMS: calcd for C54H42FeN8Ni2, ([M+]) 974.15846, found 974.15920.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b03158. Additional characterization and 1H and 13C NMR spectra of all new compounds (PDF) X-ray crystallographic data for BODIPYFc (CIF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail for K.E.B.: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was funded by the Swedish Research Council (project grant 2013-4655 to K.E.B.) and by Stiftelsen Olle Engkvist Byggmästare (postdoctoral fellowship to A.I.A.).

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REFERENCES

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DOI: 10.1021/acs.inorgchem.6b03158 Inorg. Chem. XXXX, XXX, XXX−XXX