Design of new aggregates for catalysis
Tosi, Filippo
DOI:
10.33612/diss.107814277
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Publication date: 2019
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Tosi, F. (2019). Design of new aggregates for catalysis. Rijksuniversiteit Groningen. https://doi.org/10.33612/diss.107814277
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Chapter 3
Salen-Based Amphiphiles: Directing
Self-Assembly in Water by Metal
Complexation
ABSTRACT: Tuning morphologies of self-assembled structures in water is a
major challenge. Here we present a salen-based amphiphile which, using complexation with distinct transition metal ions, allows to control effectively the self-assembly morphology in water, as observed by Cryo-TEM and confirmed by DLS measurements. Applying this strategy with various metal ions gives a broad spectrum of self-assembled structures starting from the same amphiphilic ligand (from cubic structures to vesicles and micelles). Thermogravimetric Analysis and Electric Conductivity measurements reveal a key role for water coordination apparently being responsible for the distinct assembly behavior.
This chapter was published as: Filippo Tosi, Marc C. A. Stuart, Sander J. Wezenberg,
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3.1 Introduction
A major challenge is to control the morphology of the self-assembled structure in water in an effective and simple manner. In this regard, accessing more than one morphology with only minor modification of the parent amphiphile is a difficult task; it generally requires significant structural modification and extensive chemical synthesis. We envisioned that transition metal complexation to a readily accessible ligand, forming the core of the amphiphile, would present a unique opportunity to access a broad range of aggregates.
As the ligand, salen was our first choice since these ligands and their metal
complexes are known for their remarkable self-assembly properties.[1–5] Because of
their modular structure, they have been successfully employed as supramolecular
building blocks,[6,7] for example, in the formation of Langmuir films,[8] boxes,[9–12]
helical structures,[13,14] gels,[15–17] fibers,[18,19] metal-organic frameworks,[20,21] covalent
organic frameworks[22–24] and nano-rings[25] or for surface functionalization.[26] Salen
ligands are also easily synthesized by an imine condensation and the metalation step is usually straightforward and high yielding. Here we report the synthesis and self-assembly in water of an amphiphilic salen ligand and its metal complexes of the late first row transition metals. In the design of our target molecule we took advantage of the modular synthesis of salen ligands by separately preparing the hydrophilic diamine and hydrophobic salicylic aldehyde components. The amphiphilic salen ligand that we envisioned (Figure 3.1), is then obtained in a final condensation step. In the present study, it is shown that this salen framework allows for remarkable diversification in self-assembly behaviour by making different complexes (i.e. Cu, Ni, Co, Fe, Mn).
=
Figure 3.1: Design of salen-based amphiphiles.
3.2 Synthesis
The synthesis of the salen ligand started from the known MOM-protected phenol
1,[27] which was first deprotected by acidic hydrolysis and then formylated in the
ortho-position using paraformaldehyde to afford salicylaldehyde 3 (Scheme 3.1). The
chiral diamine precursor 6 with pendant PEG chains was synthesized starting from
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to obtain compound 5. After Boc deprotection, the TFA salt 6 was treated with base and subsequent condensation with aldehyde 3 in a 1:2 ratio gave the amphiphilic salen ligand L1.
Scheme 3.1: Synthesis of the amphiphilic salen ligand L1.
The structure of the amphiphile was confirmed by 1H NMR, showing both alkyl
and PEG chains (Figure 3.2), in addition to HRMS.
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The complexes L1-Cu and L1-Ni were obtained in good yields by metalation of
L1 with the corresponding acetate salts (Scheme 3.2). The iron complex L1-Fe was
obtained in a similar way using FeCl3.3H2O as the metal source. As for Cu and Ni, the
synthesis of the cobalt complex L1-Co was performed using Co(OAc)2.4H2O, which in
this case was followed by oxidation with molecular oxygen in the presence of AcOH. The manganese complex L1-Mn was synthesized using a similar protocol, starting
from L1 and Mn(OAc)2.4H2O, followed by oxidation in the presence of molecular
oxygen and an excess of LiCl. The successful synthesis of all metal complexes was confirmed by HRMS, showing the expected isotopic patterns (see Appendix, Figure 3.9-Figure 3.13), as well as IR and UV-Vis spectroscopy. The diamagnetic complex
L1-Ni was additionally characterized by NMR.
Scheme 3.2: Synthesis of the metal complexes of amphiphilic salen ligand L1. (i)
Cu(OAc)2.H2O/Ni(OAc)2.4H2O/FeCl3.3H2O, MeOH, reflux, 2 h; (ii) Co(OAc)2.4H2O, CH2Cl2/MeOH 1:1, rt, 1 h then AcOH, rt, air, 3 h; (iii) Mn(OAc)2.4H2O, MeOH, reflux, 1 h then LiCl (30 eq), rt, air, 1 h.
3.3 Self-Assembly Behavior
The self-assembly behavior of the parent amphiphile and its metal complexes
was studied by Cryo-TEM using a sample concentration of 2 mM.* The ligand L1 was
found to self-assemble in water in the form of a cubic structure (Figure 3.3a). This structure is typically characterized by a bi-continuous bilayer of inverted micelles, which shows a porous system clearly visible in the convolutions of the soft
material.[29] Interestingly, under the same experimental conditions, the metal
* All samples were studied at different concentrations, namely 0.5 mM, 1 mM and 2 mM. A
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complexes showed substantially different morphologies. The Cu and Ni complexes
both gave aggregates that were characterized as sponges (Figure 3.3b-c).[30]
Apparently, the geometrical constraint of the salen core of the amphiphile in a square planar geometry, as a result of Cu or Ni complexation, results in a very distinct self-assembly behavior with respect to the free ligand. The observed structures, which are smaller than the cubic structure generated by the free ligand L1, still belong to the same aggregation domain (namely inverted micelles) and therefore show a similar type of porous and ordered bilayer (Figure 3.3b-c).
Figure 3.3: (a) Self-assembly of L1 into cubic aggregates, QII; (b) Self-assembly of L1-Cu into sponges, QII; (c) Self-assembly of L1-Ni into sponges, QII.
The presence of the metal in the soft material was confirmed by EDX analysis (Figure 3.4). Elemental mapping clearly showed the presence of Cu and Ni in the sponge aggregates and not in the water solution, although apparently for Cu some leaching occurred.
Figure 3.4: EDX mapping of L1-Cu (a) and L1-Ni (b) sponges on holey carbon grid: (top) elemental
mapping of C, red and Cu (a) Ni (b) green; (bottom) EDX spectrum of the mapping.
50 nm 50 nm 50 nm
a) b) c)
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A striking difference in assembly behavior was observed with the Co, Fe and Mn complexes, all of which feature a pentacoordinated metal ion. The complexes L1-Co
and L1-Fe were found to form lamellar vesicles[31,32] (Figure 3.5a-b).
Figure 3.5: (a) Self-assembly of L1-Co into vesicles, Lα; (b) Self-assembly of L1-Fe into vesicles, Lα; (c) Self-assembly of L1-Mn into spherical micelles (L1 phase) in dotted circles.
These vesicles feature a bilayer very distinct from the nanostructures formed by the starting ligand L1. Furthermore, the L1-Mn complex self-assembles into spherical
micelles[33] (Figure 3.5c), which is an aggregate very distinct from the one formed by
the starting ligand L1. Dynamic Light Scattering (DLS) showed sharp peaks for L1-Cu,
L1-Ni, L1-Co and L1-Fe with an average Dh value above 70 nm, confirming the
presence of large aggregates as observed by Cryo-TEM (Figure 3.6).
Figure 3.6: DLS measurements of self-assembled metallosalen complexes (1 mM). The scattering of the
samples were recorded at 20 °C as a measure for assembly size, and reported as mass percentage. The models used by Wyatt software are fitting for spherical objects.
In contrast to the above mentioned amphiphiles, L1-Mn showed an average Dh
value around 16 nm, confirming the presence of much smaller aggregates as observed by Cryo-TEM in the formation of spherical micelles shown in Figure 3.5c. It is
50 nm 100 nm 50 nm
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important to note that not only different aggregates are obtained for the metal complexes, but by using the same ligand scaffold a wide range of self-assembled amphiphilic structures can be obtained.
3.4 Critical Packing Parameter
In order to explain the major differences in assembly behavior, we qualitatively
considered the Critical Packing Parameter (CPP) of the amphiphile (Equation 3.1),[34]
i.e. the ratio between the volume of the lipophilic chain (V), its length (lc) and the
interfacial area occupied by the hydrophilic component (a0).
𝐶𝑃𝑃 = 𝑉
𝑙𝑐𝑎0
Equation 3.1: Critical Packing Parameter (CPP) definition.
A change in substitution pattern, length or chain terminus of an amphiphile is
known to influence these three terms.[35] In our case, the molecular scaffold of the
amphiphile was left intact and by merely changing the metal center the morphology obtained upon self-assembly was altered. Considering the CPP equation, which is an expression of the ratio between hydrophobic and hydrophilic balance in the amphiphile, we imagined that the differences observed could be explained in terms of the geometrical and electronical characteristics of our metal complexes. The largest deviations in aggregation from the parent ligand L1 were observed with the complexes of Co, Fe and Mn, which have a 3+ oxidation state, rather than the 2+ oxidation state of Cu and Ni. Furthermore, they possess an axial ligand and have the possibility to coordinate an additional electron donating ligand. Unlike Cu and Ni, the metal centers of the Co, Fe and Mn salen amphiphiles may coordinate water as an
external ligand.[36–38] Water coordination should lead to a higher hydrophilic character
(a0) resulting in a decrease of the CPP as is reflected in the structural change from
cubic to lamellar and eventually micellar aggregates for Mn complexes. At the same time, the hydrophobic volume is reduced, as the metal participates in hydrating the amphiphile. The generation of an octahedral complex, also sterically different from the square planar complexes of Cu and Ni, would cause a significant change in CPP. Overall, the hydration of the amphiphile is therefore expected to drive the self-assembly process from inverted micelles (CPP > 1 for L1-Cu and L1-Ni) to bilayers (½ < CPP < 1 for L1-Co and L1-Fe) and even micelles (CPP < ½ for L1-Mn).
To demonstrate water coordination, we prepared the aqua-complexes of Co, Fe and Mn starting from the model ligand L2 (see experimental section), which is similar to L1, but lacks the hydrophobic and hydrophilic chains (Figure 3.7).
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Figure 3.7: Model salen ligand L2 and corresponding Co, Fe and Mn complexes.
Thermogravimetric Analysis (TGA) showed water desorption upon heating of the
samples of Co and Fe (±160 °C and ±196 °C, respectively).† However, in the case of Mn
we observed decomposition of the complex and formation of HCl.‡ Since the
self-assembly behavior of the Mn amphiphile was surprisingly different, we hypothesized that upon initial water coordination the Cl ion partially dissociates leading to an ion
pair, the formation of which has been reported for the core salen structure.[39] The
charge formation upon chloride dissociation was successfully proven by Electric Conductivity (EC) experiments using L2-Mn, showing a 1:1 electrolyte dissociation
(13.36 µS cm-1),§ which could not be observed for the model complexes L2-Co and
L2-Fe. Due to the much better solubility of the charged species in water, the CPP is
decreased. Hence, the formation of spherical micelles in our case can be explained by charge formation. Our proposed water-binding model is illustrated in Figure 3.8.
Figure 3.8: Proposed water-binding model and resulting aggregates with different metal ions.
3.5 Conclusions
In conclusion, we have developed a powerful, modular approach, based on an amphiphilic salen scaffold, to access a diverse set of self-assembled structures in
† Decomplexation of water above 100 °C in the TGA diagram illustrates that a water molecule
was coordinated to the Co and Fe metal centers.
‡ As reported in ref. [62], the crystal structure of the salen(MnCl)H2O complex shows a shorter
Mn-O bond than the Mn-Cl bond, suggesting that the Mn-Cl bond is weaker. This could explain the observed dissociation of HCl.
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water. Cryo-TEM measurements demonstrated that metalation of the salen ligand gave access to a wide range of aggregates. These include: cubic assemblies for the free ligand, sponges in the case of Cu(II) and Ni(II) complexes, vesicles for Co(III) and Fe(III), and micelles for Mn(III). TGA and EC studies support the hypothesis that water coordination gives rise to the observed differences in aggregation behavior, which can be related to the CPP. As far as we know, our approach is unprecedented in terms of effectively controlling self-assembly of a single amphiphilic structure in water and the diverse structural morphologies obtained by only changing its metal center, and controlling water binding. These findings open the path for future developments in the field of responsive self-assembly and catalysis in confined-space.
3.6 Contributions
The project was carried out under the supervision of dr. S. J. Wezenberg and prof. dr. B. L. Feringa. The synthesis, spectroscopy studies and DLS measurements were carried out by F. Tosi. Cryo-TEM and EDX studies were performed by M. C. A. Stuart.
3.7 Experimental Section
Methods. As a standard optimized procedure, the compounds were dissolved in
a small amount of THF (5% of the total solution) and subsequently added to MilliQ water, which generated in almost all cases a milky, turbid sample. Each of the samples was then shock frozen in liquid nitrogen and sonicated 3 times.
Cryo-TEM. The samples were prepared by depositing a few µL of amphiphile
solution on holey carbon coated grids (Quantifoil 3.5/1, Quantifoil Micro Tools, Jena, Germany). After blotting the excess liquid, the grids were vitrified in liquid ethane (Vitrobot, FEI, Eindhoven, The Netherlands) and transferred to a FEI Tecnai T20 cryo-electron microscope equipped with a Gatan model 626 cryo-stage operating at 200 keV. Micrographs were recorded under low-dose conditions with a slow-scan CCD camera. The bilayer thickness was measured on slightly defocused cryo-electron microscopy images to obtain maximal phase contrast. EDX analysis was performed with an SDD detector (Oxford xmax 80T) and the elemental ratio was calculated using INCA software. For the analysis of Cu complexes Molybdenum Quantifoil grids were used instead of copper grids.
3.8 Synthetic Procedures
Compound 1,[27] 4[28] and p-toluenesulfonate tetraethylene glycol monomethyl
ether,[40] were prepared according to known literature procedures and structural data
were in accordance with the literature. Salen ligand L2 and metallosalen complexes
L2-Cu,[41] L2-Ni,[42] L2-Co,[43] L2-Fe[44] and L2-Mn[45] were prepared according to
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data. Metallosalen complexes L1-Cu,[41] L1-Ni,[42] L1-Co,[43] L1-Fe[44] and L1-Mn[45]
were prepared according to modified literature procedures.
MOM protected phenol 1 (4.24 g, 13.9 mmol) was dissolved in THF (100 mL) under a nitrogen atmosphere. A solution of aq. HCl (37%, 34.3 mL) was added dropwise and the mixture was left stirring at rt for
16 h. The reaction mixture was then washed with sat. aq. NH4Cl (ca.
100 mL), and the aqueous layer was extracted with EtOAc (2x50 mL).
The combined organic layers were washed with brine, dried over MgSO4, and
concentrated in vacuo. Purification by column chromatography (SiO2, Pentane/EtOAc:
97:3) gave 2 (3.6 g, 99%) as a white solid; (Rf: 0.6 Pentane/EtOAc: 97:3); m.p. 44.1 –
44.5 °C; 1H NMR (400 MHz, CDCl3) δ 7.11 (dd, J = 7.4, 1.7 Hz, 1H), 7.08 (td, J = 7.7, 1.7
Hz, 1H), 6.87 (td, J = 7.4, 1.2 Hz, 1H), 6.75 (dd, J = 7.7, 1.2 Hz, 1H), 2.60 (t, J = 7.6 Hz,
2H), 1.69 – 1.52 (m, 2H), 1.33 – 1.26 (m, 18H), 0.93 – 0.83 (t, J = 6.5 Hz, 3H); 13C NMR
(101 MHz, CDCl3) δ 153.7, 130.5, 128.9, 127.3, 121.1, 115.5, 32.2, 30.2, 30.1, 30.0, 30.0
(2C), 29.9, 29.9, 29.9, 29.7, 23.0, 14.4.
Compound 2 (1.94 g, 7.39 mmol), MgCl2 (1.4 g, 14 mmol) and
paraformaldehyde (492 mg, 16.3 mmol) were dissolved in dry THF (30 mL) under a nitrogen atmosphere. Triethylamine (2.06 mL, 14.8 mmol) was added dropwise upon which the white suspension turned red. The mixture was stirred at reflux for 16 h after which the
reaction was treated with sat. aq. NH4Cl (ca. 30 mL). The resulting mixture extracted
with EtOAc (2x30 mL) and the combined organic layers were washed with brine,
dried over MgSO4, and concentrated in vacuo. Purification by column chromatography
(SiO2, Pentane/EtOAc: 97:3) gave 3 (1.4 g, 69%) as a white solid; (Rf: 0.6
Pentane/EtOAc: 98:2); m.p. 29.4 – 31.5 °C; 1H NMR (400 MHz, CDCl3) δ 11.27 (s, 1H),
9.88 (s, 1H), 7.39 (d, J = 7.5 Hz, 2H), 6.94 (t, J = 7.5 Hz, 1H), 2.66 (t, J = 7.7 Hz, 2H), 1.80
– 1.47 (m, 2H), 1.26 – 1.35 (m, 18H), 0.88 (t, J = 6.7 Hz, 3H); 13C NMR (101 MHz, CDCl3)
δ 197.1, 160.1, 137.4, 131.8, 131.7, 120.5, 119.7, 32.2, 30.0, 30.0, 30.0, 29.9, 29.8, 29.8,
29.7, 29.7, 29.4, 23.0, 14.4; HRMS (ESI-ion trap) m/z: [M-H]– Calcd for C19H29O2
289.2162, found 289.2177.
Compound 4 (200 mg, 0.45 mmol), Cs2CO3
(308 mg, 0.94 mmol) and p-toluenesulfonate tetraethylene glycol monomethyl ether (155 mg, 0.94 mmol) were dissolved in dry THF (10 mL) under a nitrogen atmosphere. The reaction mixture was heated at reflux for
16 h, treated with sat. aq. NH4Cl (ca. 20 mL) and extracted with EtOAc (2x20 mL). The
combined organic layers were washed with brine, dried over MgSO4, and concentrated
in vacuo. Purification by column chromatography (SiO2, CH2Cl2/MeOH: 99:1 to 95:5)
gave 5 (219 mg, 59%) as a white solid; (Rf: 0.2 CH2Cl2/MeOH: 98:2); 1H NMR
(400 MHz, CDCl3) δ 6.92 (d, J = 8.2 Hz, 4H), 6.70 (d, J = 8.2 Hz, 4H), 5.49 (br, 2H), 4.74
(br, 2H), 4.04 (t, J = 4.7 Hz, 4H), 3.69 (t, J = 4.7 Hz, 4H), 3.60 – 6.70 (m, 20H), 3.52 (dd,
J = 6.3 Hz, J = 4.7 Hz, 4H), 3.35 (s, 6H), 1.41 (s, 18H); 13C NMR (101 MHz, CDCl3) δ 158.3, 156.5, 132.0, 128.7, 114.7, 79.9, 72.2, 71.0, 70.9, 70.8 (2), 69.9, 67.6, 60.3,
59.3, 28.7; HRMS (ESI-ion trap) m/z: [M+H]+ Calcd for C42H69N2O14 825.4743, found
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Compound 5 (145 mg, 0.175 mmol) and triisopropyl silane (0.078 mL, 61 mg,
0.39 mmol) were dissolved in CH2Cl2 (4 mL).
TFA (0.134 mL, 1.75 mmol) was added dropwise and the reaction mixture was stirred at rt for 16 h. Toluene (10 mL) was then added and the volatiles were
evaporated. Precipitation with Et2O (4x5 mL)
gave 6 (104 mg, 70%) as a white semisolid; 1H NMR (400 MHz, CDCl3) δ 7.04 (d, J = 8.2
Hz, 4H), 6.72 (d, J = 8.2 Hz, 4H), 4.70 (br, 2H), 4.00 (t, 4H), 3.77 (t, 4H), 3.60 – 6.71 (m,
20H), 3.44 (t, 4H), 3.27 (s, 6H); 13C NMR (101 MHz, CDCl3) δ 159.7, 129.4, 126.0, 115.4,
77.0, 71.9, 70.8, 70.6, 70.5, 70.4, 69.8, 67.6, 59.0, 58.5; 19F NMR (376 MHz, CDCl3)
δ -75.7.
Compound 6 (100 mg, 0.117 mmol) was dissolved in
CH2Cl2 (10 mL) and washed with 10 mL of aq. NaOH
(1 M) solution. The combined organic layers were
collected, dried over MgSO4 and concentrated in
vacuo. The resulting starting material and compound
3 (67.9 mg, 0.234 mmol) were dissolved in dry
MeOH (4 mL) under a nitrogen atmosphere. The reaction mixture was heated at reflux for 1 h, then
concentrated in vacuo. Purification by column chromatography (Al2O3 neutral,
CH2Cl2/MeOH: 99:1) gave pure L1 (106.5 mg, 78%) as a yellow oil; (Rf: 0.8
CH2Cl2/MeOH: 99:1); FT-IR (ATR) νmax/cm-1 3373 (m, br), 2923 (s), 2853 (m), 1612
(m); 1H NMR (400 MHz, CDCl3) δ 13.45 (s, 2H), 8.31 (s, 2H), 7.10 (d, J = 7.7 Hz, 2H), 7.05 (d, J = 8.4 Hz, 4H), 6.98 (d, J = 7.7 Hz, 2H), 6.75 (d, J = 8.4 Hz, 4H), 6.70 (t, J = 7.7 Hz, 2H), 4.60 (s, 2H), 4.05 (t, J = 5.0 Hz, 4H), 3.83 (d, J = 5.0 Hz, 4H), 3.66 (m, 20H), 3.54 (t, J = 4.9 Hz, 4H), 3.37 (s, 6H), 2.62 (t, J = 7.6 Hz, 4H), 1.29 (m, 40H), 0.88 (t, J = 6.9 Hz, 6H); 13C NMR (101 MHz, CDCl3) δ 166.3, 159.1, 158.3, 132.8, 132.2, 130.6, 129.7, 129.2 (2C), 118.5, 114.7, 80.1, 72.2, 71.1, 70.9 (3C), 70.8, 70.0, 67.6, 59.3, 32.2,
30.0 (4C), 29.8 (4C), 29.7, 23.0, 14.4. HRMS (ESI-ion trap) m/z: [M+H]+ Calcd for
C70H109N2O12 1169.7975, found 1169.8031.
Compound L1 (68 mg, 0.058 mmol) was dissolved in dry MeOH (2 mL) under a nitrogen atmosphere.
A solution of Cu(OAc)2.H2O (11 mg, 0.058 mmol) in
dry MeOH (1 mL) was added dropwise, upon which the reaction mixture turned dark brown. The reaction mixture was heated at reflux for 1 h, then toluene (10 mL) was added and the crude product was concentrated in vacuo. Purification by column
chromatography (Al2O3 neutral, CH2Cl2/MeOH:
99:1) gave pure L1-Cu (38.4 mg, 54%) as a dark brown oil; (Rf: 0.6 CH2Cl2/MeOH:
99:1); FT-IR (ATR) νmax/cm-1 2921 (s), 2854 (m), 1609 (m); UV-Vis (CH3CN) λmax/nm:
231, 278, 375; UV-Vis (H2O) λmax/nm: 235, 286, 384; HRMS (ESI-ion trap) m/z: [M+H]+
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Compound L1 (136 mg, 0.117 mmol) was dissolved in dry MeOH (4 mL) under a
nitrogen atmosphere. A solution of Ni(OAc)2.4H2O
(29.1 mg, 0.117 mmol) in dry MeOH (1 mL) was added dropwise upon which the reaction mixture turned intense red. The reaction mixture was heated at reflux for 1 h, then toluene (10 mL) was added and the crude product was concentrated in vacuo.
Purification by column chromatography (Al2O3
neutral, CH2Cl2/MeOH: 99:1) gave pure L1-Ni (97 mg,
67%) as a red oil; (Rf: 0.4 CH2Cl2/MeOH: 99:1); FT-IR (ATR) νmax/cm-1 2923 (s), 2854
(m), 1607 (m); UV-Vis (CH3CN) λmax/nm: 230, 258, 327, 419; UV-Vis (H2O) λmax/nm:
232, 265, 329, 427; 1H NMR (400 MHz, CD2Cl2 + 5% Pyridine-d5) δ 7.55 (d, J = 8.7 Hz, 4H), 7.28 (s, 2H), 7.12 (dd, J = 7.1, 1.7 Hz, 2H), 6.94 (d, J = 8.7 Hz, 4H), 6.83 (dd, J = 8.0, 1.7 Hz, 2H), 6.44 (t, J = 8.0, 7.1 Hz, 2H), 4.54 (s, 2H), 4.14 – 4.01 (m, 4H), 3.84 – 3.78 (m, 4H), 3.72 – 3.43 (m, 24H), 3.32 (s, 6H), 2.71 (td, J = 7.1, 1.6 Hz, 4H), 1.80 – 1.60 (m, 4H), 1.48 – 1.19 (m, 36H), 0.99 – 0.80 (m, 6H); 13C NMR (101 MHz, CD2Cl2 + 5% Pyridine-d5) δ 164.6, 163.5, 159.8, 134.6, 134.0, 131.8, 131.2, 130.0, 120.6, 115.9, 115.1, 79.1, 72.7, 71.6, 71.4, 71.3 (2C), 71.2, 70.3, 68.4, 59.4, 32.8, 31.5, 30.8, 30.8, 30.7,
30.7, 30.6, 30.6, 30.3, 30.2, 23.5, 14.7; HRMS (ESI-ion trap) m/z: [M+H]+ Calcd for
C70H107N2NiO12 1230.7115, found 1230.7059.
Compound L1 (68 mg, 0.058 mmol) was dissolved in dry MeOH (2 mL) under a nitrogen atmosphere.
A solution of FeCl3.6H2O (16 mg, 0.058 mmol) in dry
MeOH (1 mL) was then added dropwise upon which the reaction mixture turned dark purple. The reaction mixture was heated at reflux for 1 h, then toluene (10 mL) was added and the crude product was concentrated in vacuo. Purification by column
chromatography (Al2O3 neutral, CH2Cl2/MeOH: 99:1) gave pure L1-Fe 54.9 mg, 75%)
as a dark brown oil; (Rf: 0.4 CH2Cl2/MeOH: 99:1); FT-IR (ATR) νmax/cm-1 2923 (s),
2854 (m), 1609 (m); UV-Vis (CH3CN) λmax/nm: 226, 266, 327; UV-Vis (H2O) λmax/nm:
226, 269, 304, 397; HRMS (ESI-ion trap) m/z: [M-Cl]+ Calcd for C70H106FeN2O12
1220.7136, found 1220.7160.
Compound L1 (68 mg, 0.058 mmol) was dissolved in dry MeOH (2 mL) under a nitrogen atmosphere. A
solution of Mn(OAc)2.4H2O (15 mg, 0.058 mmol) in
dry MeOH (1 mL) was then added dropwise upon which the reaction mixture turned dark brown. The reaction mixture was heated at reflux for 1 h, then allowed to cool down to room temperature. LiCl (84.3 mg, 1.99 mmol) was added and the reaction mixture was stirred under air for 1 h. Toluene (10 mL) was added the crude product
was concentrated in vacuo. Purification by column chromatography (Al2O3 neutral,
CH2Cl2/MeOH: 99:1) gave pure L1-Mn (54.9 mg, 79%) as a dark brown oil; (Rf: 0.2
CH2Cl2/MeOH: 99:1); FT-IR (ATR) νmax/cm-1 2924 (s), 2853 (m), 1607 (m); UV-Vis
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HRMS (ESI-ion trap) m/z: [M-Cl]+ Calcd for C70H106MnN2O12 1221.7121, found
1221.7062.
Compound L1 (68 mg, 0.058 mmol) was dissolved
in deoxygenated dry CH2Cl2 (2 mL) under a
nitrogen atmosphere and cooled down to 0 °C. A
solution of Co(OAc)2.4H2O (5.8 mg, 0.088 mmol) in
deoxygenated dry MeOH (1 mL) was then added dropwise upon which the reaction mixture turned bright red. The reaction mixture was stirred for 1 h at 0 °C, then all volatiles were removed in high vacuum. Toluene (2 mL) and AcOH (44 µL) were added and the reaction mixture was stirred under air for 3 h. The crude product was
concentrated in vacuo. Purification by column chromatography (Al2O3 neutral,
CH2Cl2/MeOH: 99:1) gave L1-Co (40.6 mg, 40%) as a dark brown oil; (Rf: 0.3
CH2Cl2/MeOH: 99:1); FT-IR (ATR) νmax/cm-1 2923 (s), 2852 (m), 1607 (m); UV-Vis
(CH3CN) λmax/nm: 229, 258, 401; UV-Vis (H2O) λmax/nm: 228, 261, 402; HRMS (ESI-ion
trap) m/z: [M-OAc]+ Calcd for C70H106CoN2O12 1225.7072, found 1225.7083.
3.9 Appendix
1226 1228 1230 1232 1234 1236 1238 1240 1242 1244 1246 1248 1250 1252 m/z 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 R e la ti ve A b u n d a n ce 1230.70591 1231.70847 1233.70766 1234.70912 1235.71094 1249.73000 1229.69784 1245.72165 1226.71242 1240.71168 1242.69819 1230.71145 1231.71481 1232.70965 1233.71300 1234.71636 1235.71971 1238.72731 1240.73402 NL: 2.04E7 FT217B_17102013114 5#5-19 RT: 0.09-0.48 AV: 15 T: FTMS + p ESI Full ms [900.00-1500.00] NL: 3.10E5 C70H107CuN2O12: C70H107Cu1N2O12 pa Chrg 156
3
1215 1220 1225 1230 1235 1240 1245 m/z 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 R e la ti ve A b u n d a n ce 1225.71929 1226.72251 1227.72114 1228.71965 1229.71807 1232.71078 1224.70950 1236.70811 1239.69568 1242.74699 1213.882431217.828611220.71288 1225.71720 1226.72056 1227.71264 1228.71600 1229.71935 1230.71356 1233.71653 1237.72749 NL: 9.45E5 FT187Ni#8-30 RT: 0.18-0.80 AV: 23 T: FTMS + p ESI Full ms [900.00-1500.00] NL: 3.05E5 C70H107N2NiO12: C70H107N2Ni1O12 pa Chrg 1Figure 3.10: HRMS of L1-Ni (top) experimental, (bottom) calculated.
1218 1220 1222 1224 1226 1228 1230 1232 1234 1236 m/z 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 R e la ti ve A b u n d a n ce 1225.70837 1226.71223 1227.71582 1228.71894 1222.71050 1224.71669 1229.72165 1220.74442 1231.71176 1235.364221237.38030 1218.65888 1225.70723 1226.71058 1227.71394 1228.71729 1229.72065 1231.72489 1233.73160 1235.73585 NL: 1.04E7 FT226#5-21 RT: 0.09-0.53 AV: 17 T: FTMS + p ESI Full ms [900.00-1500.00] NL: 4.49E5 C70H106CoN2O12: C70H106Co1N2O12 pa Chrg 1
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1215 1220 1225 1230 1235 1240 m/z 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 R e la ti ve A b u n d a n ce 1222.71043 1223.71293 1224.71560 1225.71859 1220.71602 1226.72120 1217.76308 1229.70474 1239.707031241.85226 1214.16432 1232.17732 1236.21767 1222.70897 1223.71232 1224.71568 1225.71903 1220.71364 1226.72239 1229.72999 1232.73759 NL: 1.07E8 FT225#5-16 RT: 0.09-0.39 AV: 12 T: FTMS + p ESI Full ms [900.00-1500.00] NL: 4.12E5 C70H106FeN2O12: C70H106Fe1N2O12 pa Chrg 1Figure 3.12: HRMS of L1-Fe (top) experimental, (bottom) calculated.
1218 1220 1222 1224 1226 1228 1230 1232 m/z 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 R e la ti ve A b u n d a n ce 1221.70620 1222.70845 1223.71093 1224.71330 1225.71532 1230.70346 1220.69659 1229.24402 1232.69975 1219.24393 1227.72447 1221.71208 1222.71543 1223.71879 1224.72214 1225.72550 1227.72974 1229.73645 1231.74070 NL: 5.86E7 FT217A_17102013055 8#6-18 RT: 0.12-0.45 AV: 13 T: FTMS + p ESI Full ms [900.00-1500.00] NL: 4.49E5 C70H106MnN2O12: C70H106Mn1N2O12 pa Chrg 1
58
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