Functionalized Paddle Wheel Complexes from BODIPY Carboxylic Acids

Article abstract of DOI:10.1002/zaac.201500695

A series of BODIPY carboxylic acids carrying aromatic linking units between the luminophor and the carboxylate functional group was prepared using Sonogashira and Stille type coupling protocols. Ferrocene and hydroquinone units could be introduced by either of these methods. Metal complex formation of the BODIPY carboxylic acid ligands was investigated with the divalent metal ions of copper and rhodium. Copper forms insoluble material, which crystallized in one case. The X-ray crystallographic analysis shows the presence of a BODIPY-appended paddle wheel complex with typical Cu?Cu and Cu-O distances and four BODIPY units in a distance of 9.681 ? and 9.747 ? from the dinuclear center. Treatment with donor solvents results in the decomposition/monomerization of the compound, which could be shown crystallographically for pyridine. Rhodium(II) ions form soluble paddle wheel complexes with four different BODIPY carboxylates. The crystallographic analysis of one example shows the isostructural nature of the dirhodium and the dicopper derivatives. Optical spectroscopy and cyclic voltammetry provide first insights into efficient intramolecular energy- and electron transfer pathways for the rhodium complexes.

Full text of DOI:10.1002/zaac.201500695

Journal of Inorganic and General Chemistry
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DOI: 10.1002/zaac.201500695
Functionalized Paddle Wheel Complexes from BODIPY Carboxylic Acids
Sebastian Höfler,[a] Anne Scheja,[a] Benedikt Wolfram,[a] and Martin Bröring*[a]
Keywords: BODIPY dyes; Paddle wheel structures; Carboxylate complexes; Copper; Rhodium
Abstract. A series of BODIPY carboxylic acids carrying aromatic 9.747 Å from the dinuclear center. Treatment with donor solvents re-
linking units between the luminophor and the carboxylate functional
group was prepared using Sonogashira and Stille type coupling proto-
cols. Ferrocene and hydroquinone units could be introduced by either
sults in the decomposition/monomerization of the compound, which
could be shown crystallographically for pyridine. Rhodium(II) ions
form soluble paddle wheel complexes with four different BODIPY
of these methods. Metal complex formation of the BODIPY carboxylic carboxylates. The crystallographic analysis of one example shows the
acid ligands was investigated with the divalent metal ions of copper isostructural nature of the dirhodium and the dicopper derivatives. Op-
and rhodium. Copper forms insoluble material, which crystallized in
tical spectroscopy and cyclic voltammetry provide first insights into
one case. The X-ray crystallographic analysis shows the presence of a efficient intramolecular energy- and electron transfer pathways for the
BODIPY-appended paddle wheel complex with typical Cu···Cu and
rhodium complexes.
Cu–O distances and four BODIPY units in a distance of 9.681 Å and
Introduction
All metal ions form carboxylate complexes with carboxylic
acids and some of their derivatives. Such complexes are known
to exist as mono-, di-, or oligonuclear molecules, or as poly-
meric coordination networks nowadays called MOFs (metal-
organic framework). One particularly intriguing subclass is
that of the dinuclear paddle wheel or Chinese lantern type
structure of the general formula [M2(RCO2)4L2], which is real-
ized in molecular complexes of many divalent metal ions like
CuII, RhII, RuII, CoII, CrII, MoII, and others.[1] In the paddle
wheel structures each carboxylate ligand coordinates to both
metal ions thus bridging the two metals and keeping them at
a very close distance. Therefore metal–metal bonds or strong
antiferromagnetic interactions are typically found in these spe-
cies. In many reports, the introduction of such dinuclear metal
cores as nodes into larger molecular architectures and poly-
mers was achieved using carboxylate ligands with an ad-
ditional function. Figure 1 shows a recent, typical example
with the general motif of such paddle wheel structures.[2]
BODIPYs (boron dipyrrines; Figure 2) are potent lumines-
cent dyes.[3] They are easily prepared in large amounts from
readily available chemicals, show very high fluorescence
quantum yields, are thermally and photochemically very robust
and were found to show almost no cytotoxicity.[4] In addition,
the outstanding synthetic addressability of BODIPYs[5] and the
Figure 1. Heterometallic Cu2 paddle wheel complex with peripherally
bound iridium complex fragments.[2]
* Prof. Dr. M. Bröring
E-Mail: m.broering@tu-bs.de
[a] Institut für Anorganische und Analytische Chemie
Technische Universität Braunschweig
Hagenring 30
Figure 2. BODIPY general formula and numbering scheme.
38106 Braunschweig, Germany
ease, by which the photophysical properties can be altered
through chemical means[6] has triggered much interest in the
chemical society. A large body of work has thus been devoted
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201500695 or from the au-
thor.
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to investigate this scaffold for applications as, for example,
electroluminescent dye,[7] chemosensor,[8] luminescence
marker,[9] singlet oxygen sensitizer,[3f,10] photocatalyst,[11] and
many more, including commercialization in the biomedical
sector. Another prominent use of BODIPYs is that of an an-
tenna chromophore for artificial light harvesting systems[12]
and in solar cells. For these applications the photochemical
robustness of BODIPYs is of great importance.
There is an actual trend to combine BODIPY dyes with
metal complex fragments and/or nanoparticles in order to pre-
pare functional (supra)molecular materials for applications in,
for example, energy research and pharmaceutical science.[13]
Within this context we attempted to use BODIPY ligands with
peripheral carboxylate functions for the preparation of dinu-
clear paddle wheel complexes, and to study their properties.
The approach was successful, and first results are reported in
this contribution.
Results and Discussion
Preparation and Characterization of BODIPY Carboxylic
Acids
For this project, the use of BODIPY carboxylic acids with
the carboxylate function connected to either the meso or the β
position and with additional electron relay units (ferrocenyl or
hydroquinonyl subunits) was anticipated. Several new struc-
tures had thus to be established. Scheme 1 shows the syntheses
of the new BODIPY carboxylates 3 and 7, where the carb-
oxylic acid groups are connected to the BODIPY through the
meso position. In both cases the BODIPY luminophor was
formed in a one-pot reaction by condensation of the respective
benzaldehyde with the appropriate alkylpyrrole, followed by
dehydrogenation and difluoroboration, in 13% and 35% yield,
respectively. In the case of 6 the benzylic protection groups
can be removed hydrogenolytically in one step using 10% pal-
ladium on charcoal as the catalyst. This deprotection yields
quantitative amounts of the hydroquinone 7. Oxidation to the
quinone was unsuccessful.
Scheme 1. Preparation of 3 and 7: (a) 1. TFA, CH2Cl2; 2. DDQ; 3.
BF3·Et2O, NEt3. (b) Pd/C, H2, EtOH.
β-Carboxylated BODIPYs have been prepared in the past
but show photo- and thermolabile behavior.[14] Therefore dif-
ferent linking units with and without additional functionalities
were introduced. Stille coupling of the organo tin reagent 10
with the β-iodoBODIPYs 8 and 9 gave the benzyl esters 11
and 12 in 73% and 93% yield, respectively. As before, the
hydrogenolysis of these benzyl esters using 10% palladium on
charcoal proceeds smoothly and results in the almost quantita-
tive formation of the desired carboxylic acids 13 and 14. An
elongated phenylacetylene linker was introduced by Sonoga-
shira coupling of the mono- and diiodo-BODIPYs 9 and 15
with 4-carboxyphenylacetylene 16. In both cases only the
monosubstituted products 17 and 18 were obtained in 69% and
79% yield, respectively. In these cases the carboxy group is
Scheme 2. Preparation of 13, 14, 17 and 18: (a) Pd(PPh3)4, toluene;
(b) Pd/C, H2, EtOH; (c) Pd0, CuI, THF, NEt3.
compatible with the reaction conditions and no protection precursor 16 with the functional ferrocenyl alkyne 19 and with
group strategy needs to be applied (Scheme 2). the protected hydroquinone alkyne 21. Coupling with iodo-
As depicted in Scheme 3 the functional group compatibility BODIPY 9 results directly in the bifunctional carboxylic acids
of the Sonogashira reaction allows the exchange of the C6H4 20 and 22 in 87% and 79% isolated yields, respectively.
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Figure 4. Hydrogen bonding and packing scheme representation
of 3 (ellipsoids set to 50% probability; carbon-bound hydrogen atoms
are omitted for clarity). Selected bond lengths /Å and distances
/Å: O–H 0.964, O···H 1.664, O···O 2.626, {center C2O4}–{center
C3N2B} 9.080.
and from 1.347(2)–1.399(2) Å (C–N), supporting the delocal-
ized nature of the π system within the chromophore. The 4-
carboxyphenyl substituent at the meso position is planar in
itself (max. deviation from the C7O2 plane of 0.043 Å) and
rotated by 76.94° from the mean squares C9N2B plane of the
BODIPY. The quasi orthogonal arrangement of the π systems
is enforced by the two methyl groups located at the βЈ posi-
tions so that no free rotation of the meso aryl group is ex-
pected.
Scheme 3. Preparation of functionalized 20 and 22: Pd0, CuI, THF,
NEt3.
All new carboxylic acids were identified by mass spectrom-
The metrics of the carboxylate group clearly show two dif-
ferent types of C–O bonds with bond lengths of 1.314(2) Å
and 1.227(2) Å. A proton was found during refinement at the
more distantly bound oxygen atom O1. The carboxylates of
two neighboring molecules form hydrogen bonds leading to
dimeric structures as shown in Figure 4. The crystal lattice
forms by coplanar packing of such hydrogen bonded dimers.
The meso-methyl derivative 13 formed a single crystal from
a dichloromethane/pentane mixture. The structure was solved
etry and characterized by 1H, 13C, 19F, and 11B NMR methods.
In three cases single crystals formed which were suitable for
X-ray diffraction analyses. Crystallographic data for these
analyses is given in Table 3. The meso substituted BODIPY
carboxylic acid 3 forms blocks from dichloromethane and
crystallizes in the space group P1 with Z = 2. The molecular
structure and the packing scheme of 3 are shown in Figure 3
and Figure 4.
¯
¯
in space group P1 with two crystallographically distinct, but
very similar molecules in the unit cell. Only molecule A is
shown in Figure 5.
Figure 5. Molecular structure of BODIPY carboxylic acid 13
(molecule A; ellipsoids set to 50% probability; carbon-bound
hydrogen atoms are omitted for clarity). Selected bond lengths /Å and
angles /°: B–N1 1.542(2), B–N2 1.549(2), B–F1 1.389(2), B–F2
1.390(2), C–O1 1.273(2), C–O2 1.260(2), C8–Cphenyl 1.479(2); N1–
B–N2 107.01(11), N1–B–F1 108.96(12), N1–B–F2 110.42(12), N2–
B–F1 110.99(12), N2–B–F2 109.67(12), F1–B–F2 109.76(12), O1–C–
O2 124.21(13).
Figure 3. Molecular structure of BODIPY carboxylic acid 3 (ellipsoids
set to 50% probability; carbon-bound hydrogen atoms are omitted for
clarity). Selected bond lengths /Å and angles /°: B–N1 1.550(2), B–
N2 1.551(2), B–F1 1.400(2), B–F2 1.393(2), C–O1 1.314(2), C–O2
1.227(2); N1–B–N2 106.9(1), N1–B–F1 109.8(1), N1–B–F2 110.6(1),
N2–B–F1 110.1(1), N2–B–F2 110.1(1), F1–B–F2 109.3(1), O1–C–O2
123.57(13).
The almost planar C9N2B and distorted tetrahedral BF2N2
Compound 3 constitutes a typical BODIPY with a coplanar subunits of 13 are characterized by bond lengths and angles as
core of two five-membered and one six-membered ring. The expected. For example, the data of the coordination unit
boron atom is bound to two nitrogen atoms [1.550(2) Å and around the boron atom is found at the following values: B–N:
1.551(2) Å] and two F atoms [1.400(2) and 1.393(2) Å] in a 1.542(2) and 1.549(2) Å; B–F: 1.389(2) and 1.390(2) Å;
distorted tetrahedron with bond angles at the boron atom in the X–B–Y angles: 107.01(11)–110.99(12)°. Other than for 3, how-
range of 106.9(1)–110.6(1)°. All C–C and C–N bond lengths ever, the 4-carboxyphenyl substituent of 13 is not found in an
of the C9N2 unit are aligned from 1.384(2)–1.430(2) Å (C–C), almost perpendicular orientation but largely rotated in direc-
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tion of a coplanar arrangement with the BODIPY core. The
As for 3 and 13, the C9N2B luminophor of 18 and the met-
interplane angle of these planar subunits of only 39.65° ac- rics of the BF2N2 subunit account for a typical BODIPY with
counts for a significant degree of conjugation between the lum- aligned bond lengths and a distorted tetrahedral coordination
inophor and the designated metal binding site. Typical for of the boron atom [B–N: 1.560(12) and 1.553(11) Å; B–F:
carboxylic acids, and similar to the behavior or 3, identical 1.378(12) and 1.395(12) Å; X–B–Y angles: 105.5(7)–
molecules of 13 form hydrogen bridged dimers, from which 111.2(8)°]. The mesityl substituent at the meso position is
the crystal forms by π stacking (Figure 6).
found in an almost perpendicular orientation with a torsion
angle of 89.00° while the bridging acetylene linker leads to a
basically coplanar arrangement of the carboxyphenyl group
with the BODIPY chromophore. As before, the carboxylic acid
groups of two molecules form a hydrogen-bridged system
leading to the dimerization of two molecules, and the crystal
is again formed by π stacking interactions of these dimers.
The new BODIPY carboxylic acids are characterized by an
intense absorption in the optical spectrum at about 500–
550 nm and by fluorescence from the excited singlet state. The
fluorescence band appears close to the absorption maximum
with a small Stokes shift of 17–31 nm and with high quantum
yields for most of the compounds (Table 1). For the ferrocene
and hydroquinone derivatives 20 and 7, however, the quantum
yields drop dramatically, indicating an efficient electron or en-
ergy transfer process in the excited state. The same holds true
for the iodinated 18, where spin orbit coupling of the heavy
atom results in efficient quenching of the singlet excited state.
Further dependencies on the quantum yields like substitution
pattern or donor strengths of the substituents are not obvi-
ous.[15]
Figure 6. Hydrogen bonding and packing scheme representation of 18
(ellipsoids set to 50% probability; carbon-bound hydrogen atoms are
omitted for clarity). A and B denominate the crystallographically dif-
ferent molecules of 13. Selected bond lengths /Å and distances /Å: O–
H 0.84, O···H 1.771/1.895, O···O 2.598/2.720, {center C2O4}-{center
C3N2B} 10.991/11.120.
BODIPY carboxylic acid 18 carrying the acetylene-elon-
gated 4-carboxyphenyl group at the β position crystallized
from chloroform in the triclinic system, space group P1, with
Z = 2. Figure 7 and Figure 8 illustrate the molecular structure
of 18 and the arrangement of the molecules in the crystal pack-
ing.
¯
Table 1. Photophysical data of BODIPY carboxylic acids (CH2Cl2).
Compound Absorption
Emission
λmax /nm
λmax /nm εa)
ΦF
b)
3
7
528
502
509
516
532
553
533
538
65500
n.d.
550
519
536
534
559
580
552
569
0.50
0.03
0.88
0.94
0.53
0.08
Ͻ 0.01
0.48
c)
c)
c)
c)
13
14
17
18
20
22
91000
77700
42100
64900
21700
34400
a) Given in L·mol–1·cm–1. b) Excitation with λmax. c) In THF.
Figure 7. Molecular structure of BODIPY carboxylic acid 18 (ellip-
soids set to 50% probability; carbon-bound hydrogen atoms are omit-
ted for clarity). Selected bond lengths /Å and angles /°: B–N1
1.560(12), B–N2 1.553(11), B–F1 1.378(12), B–F2 1.395(12), C–O1
1.294(1), C–O2 1.235(1), C–I 2.080(9), C8–C23 1.426(12), C23–C24
1.192(12), C24–C25 1.440(12); N1–B–N2 105.5(7), N1–B–F1
111.2(8), N1–B–F2 109.1(8), N2–B–F1 111.2(8), N2–B–F2 109.4(8),
F1–B–F2 110.3(8), O1–C–O2 125.1(8), C8–C23–C24 175.1(10), C23–
C24–C25 177.2(10).
BODIPY-appended Paddle Wheel Complexes
When the new BODIPY carboxylic acids are treated with
copper(II) salts a solid forms immediately in all cases. This
solid could not be redissolved without decomposition of the
material. Therefore a careful cocrystallization procedure was
sought for the preparation of the desired copper complexes. If
dilute solutions of Cu(OTf)2 and of one of the BODIPY carb-
oxylic acids in THF are layered, a solid deposits at the liquid-
liquid interface. In the case of 3 crystals are formed, which
can be used for a crystallographic analysis. The new compound
¯
23 crystallizes in the triclinic system in space group P1.
Cocrystallized solvent (THF) is present in the crystal lattice,
which had to be treated with the SQUEEZE command in one
position due to massive disorder. Crystallographic data is given
in Table 3. Figure 9 illustrates the molecular structure of 23
Figure 8. Hydrogen bonding and packing scheme representation of 18
(ellipsoids set to 50% probability; carbon-bound hydrogen atoms are
omitted for clarity). Selected bond lengths /Å and distances /Å: O–H
0.84, O···H 1.79, O···O 2.616, {center C2O4}-{center C3N2B} 13.542. and provides selected bond lengths and angles.
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Figure 9. Molecular structure of the bis-copper(II) paddle wheel com-
Figure 10. Molecular structure of the copper(II) carboxylate complex
plex 23 (ellipsoids set to 50% probability; carbon-bound hydrogen
atoms and cocrystallized solvent molecules are omitted for clarity).
Selected bond lengths /Å and angles /°: Cu···Cu 2.6007(9), Cu–O1
1.967(2), Cu–O2 1.974(2), Cu–O3 1.968(2), Cu–O4 1.962(2), Cu–O5
2.205(2), B1–N1 1.536(4), B1–N2 1.544(4), B1–F1 1.401(4), B1–F2
1.397(4), C–O1 1.269(4), C–O2 1.266(4), B2–N3 1.541(4), B2–N4
1.551(4), B2–F3 1.404(4), B2–F4 1.383(5), C–O3 1.264(4), C–O4
1.264(4); O1–C–O2 125.8(3), O3–C–O4 126.7(3).
24 (ellipsoids set to 50% probability; carbon-bound hydrogen atoms
are omitted for clarity). Selected bond lengths /Å and angles /°: Cu–
O1 2.595(1), Cu–O2 1.9562(10), Cu–N3 2.0376(12), B–N1
1.5503(18), B–N2 1.5436(18), B1–F1 1.3933(16), B1–F2 1.3936(17),
C–O1 1.2357(16), C–O2 1.2894(15); O1–Cu–O2 56.36(9), O1–C–O2
123.23(12).
2.595(1) Å in the axis, with a O–Cu–O angle of only
56.36(9)°. Thus, the breaking-up of the dinuclear paddle wheel
structure in the presence of donor solvents appears to be a
simple consequence of the reorientation of the Jahn-Teller axis
towards the carboxylate ligand donors.
The introduction of a BODIPY-containing periphery to dinu-
clear Rh(II) complexes was more successful and led to four
soluble paddle wheel systems 25–28 (Scheme 4). In all cases
the BODIPY carboxylic acid and rhodium(II)acetate were
heated in 1,2-dichlorobenzene with 1% methanol to 150 °C for
5 h. Chromatographic purification and recrystallization from
dichloromethane/n-hexane yielded 71–73% of dark green-met-
allic solids. For the other BODIPY carboxylic acids, in particu-
lar for those carrying addition hydroquinone or ferrocene brid-
ges, only decomposed material was obtained.
Compound 23 constitutes a typical copper paddle wheel
structure with two THF molecules as ligands in the axial posi-
tions at a distance of 2.205(2) Å and a Cu–Cu distance of
2.6007(9) Å. The BODIPY carboxylate ligands show bond
lengths and angles very similar to the non-bonded acid 3. The
phenyl group is rotated away from the BODIPY mean squares
C9N2B plane by 76.29° and almost coplanar with the carboxy
group. The boron atoms are bound by two nitrogen and two
fluorine donors in a distorted tetrahedral way. The only signifi-
cant difference is the enhanced bite angle of the O–C–O moi-
ety for 23, which is 2.2–3.1° larger due to the bridging binding
mode. In this arrangement the centers of four BODIPY lumin-
ophors are located at distances of 9.682 Å and 9.747 Å from
the central Cu···Cu unit.
Further characterization of 23 was hindered by the ex-
tremely low solubility of the compound. Instead an exchange
of the THF ligands with pyridine or 4,4Ј-bipyridine during the
cocrystallization procedure was attempted. Despite many
attempts these approaches were unsuccessful. In the case of
pyridine, however, a mononuclear complex 24 carrying two
BODIPY carboxylate ligands formed and could be analysed
crystallographically. 24 crystallizes in space group P21/c with
Z = 2. Crystallographic data is given in Table 3. Figure 10 il-
lustrates the molecular structure of 24 and provides selected
bond lengths and angles.
As for the dinuclear 23 the BODIPY carboxylate ligand
does not undergo significant structural changes upon coordina-
tion, and the distance of the BODIPY luminophor center to the
copper(II) ion of 9.672 Å is also similar as in 23. The cop-
per(II) ion of 24 is coordinated in a distorted octahedral envi-
ronment typical for a 3d9 system. Within the polyhedron the
Scheme 4. Preparation of BODIPY-appended Rh2-paddle wheel com-
plexes 25–28. Rh2(OAc)4(H2O)2, 1,2-dichlorobenzene, methanol, re-
flux 5 h.
The molecular structure of RhII paddle wheel complexes
stronger N donor ligand pyridine occupies two opposite equa- with BODIPY antennae could be studied in the case of 25
torial positions at a distance of 2.0376(12) Å and pushes one (Figure 11). A single crystal suitable for a X-ray diffraction
of the weaker O donor atoms of each BODIPY carboxylate study grew from the reaction mixture. The compound crys-
ligand into the Jahn-Teller axis. This results in a highly unsym- tallizes in space group P21/c, with Z = 2 as a mixed dichloro-
metric binding of the carboxylate group with Cu–O bond benzene/methanol solvate. Crystallographic details are given
lengths of 1.9562(10) Å at the equatorial positions and in Table 3.
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proposed for propeller shaped donor-acceptor type fluo-
rophors,[17] but does not seem to be in action here.
Figure 11. Molecular structure of the dirhodium(II) paddle wheel com-
plex 25 (ellipsoids set to 50% probability; carbon-bound hydrogen
atoms are omitted for clarity). Selected bond lengths /Å and angles
/°: Rh–Rh 2.3914(8), Rh–O1 2.042(3), Rh–O2 2.026(3), Rh–O3
2.027(3), Rh–O4 2.037(3), Rh–O5 2.317(4), B1–N1 1.548(7), B1–N2
1.547(7), B1–F1 1.395(7), B1–F2 1.376(7), C–O1 1.283(6), C–O2
1.261(6), B2–N3 1.522(9), B2–N4 1.533(8), B2–F3 1.419(7), B2–F4
1.400(7), C–O3 1.272(6), C–O4 1.262(6); O1–C–O2 127.4(4), O3–C–
O4 126.7(4).
Figure 12. Normalized UV/Vis absorption spectra of dirhodium(II)
paddle wheel complexes 25–28 (ca. 10–5 mol·L–1, dichloromethane).
The molecular structure of the dirhodium complex 25 is
very similar to the isotypical structure of the copper compound
23. Four BODIPY carboxylates are bound to the Rh–Rh
bonded metal core in bridging fashions and at Rh–O distances
of 2.026(3)–2.042(3) Å, and as before, the labile axial posi-
tions are occupied by weakly coordinating solvent molecules
(methanol for 25) with a Rh–O distance of 2.317(4) Å. The
Rh–Rh distance is found at 2.3914(8) Å which is a typical
value for such single bonded species (for comparison: Rh–Rh
distance in [Rh2(OAc)4(H2O)2]: 2.378 Å)[16]. As for 23 this
arrangement results in four BODIPY luminorphor units located
in distances of 9.712 Å and 9.763 Å of the dinuclear core. In
contrast to the copper chelate 23, however, 25 is soluble in
organic solvents without decomposition of the dinuclear struc-
ture. Donor solvent do not monomerize 25 as they do for 23,
presumably due to the strong, additional rhodium(II)–rhodi-
um(II) single bond.
Table 2. Photophysical data of dirhodium complexes 25–28 (CH2Cl2).
Compound Absorption
Emission
λmax /nm
b)
λmax /nm εa)
ΦF
25
26
27
28
528
511
518
536
190600
–
358600
234200
555
536
537
562
Ͻ0.01
Ͻ0.01
Ͻ0.01
Ͻ0.01
c)
a) Given in L·mol–1·cm–1. b) Excitation with λmax. c) Unreliable data
due to low solubility.
Finally, cyclic voltammetry was applied to the BODIPY
carboxylic acid 3 and the dirhodium complex 25 (Figure 13).
Both compounds show oxidation and reduction steps at similar
potentials, indicating a basically BODIPY centered redox be-
havior of the dinuclear 25 without visible interaction between
the four redox sites. There is, however, a significant difference
in the electrochemical reversibility of the processes. While the
oxidation process is reversible for both compounds, the re-
duction of the paddle wheel complex 25 becomes irreversible.
The solubility of the dirhodium paddle wheel complexes 25–
28 allows a more detailed spectroscopic investigation. Of par-
ticular interest with respect to the possibility of an antenna
function of the BODIPY units are the optical spectra and the
electrochemical behavior of the species. UV/Vis spectra were
measured from ca. 10–5 mol·L–1 solutions of 25–28 in dichlo-
romethane. The results for absorption and emission behavior
are given in Figure 12 and in Table 2. The absorption spectra
are very similar to those of the respective BODIPY carboxyl-
ates, so that an electronic or excitonic influence of the dirho-
dium subunit or of an adjacent BODIPY chromophore can be
excluded. Fluorescence of 25–28 is observed with similar
Stokes shifts as for the free BODIPY ligands 3, 13, 14, and
17, however, the quantum yields are at very small values
Ͻ 1%. This indicates a very efficient energy- or electron trans-
fer from the excited singlet state, presumably due to the pres-
ence of the nearby Rh2 core. An alternative interpretation
comes from an aggregation caused quenching process (ACQ),
which is typically observed for low-solubility chromophores.
Figure 13. Cyclic voltammetry of BODIPY carboxylic acid 3 and di-
rhodium paddle wheel complex 25 (CH2Cl2, 0.5 mol·L–1 TBAPF6,
The phenomenon of aggregation induced emission has been 200 mV·s–1).
Z. Anorg. Allg. Chem. 2016, 107–117
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Journal of Inorganic and General Chemistry
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ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
resonances (1H, 13C NMR spectra) or to external standards (BF3·Et2O
Such a difference may be interpreted as a fast and efficient
for 11B and CFCl3 for 19F NMR spectra). Mass spectra were recorded
with a Finnigan MAT95 (HR-EI) or a Finnigan LCQ Deca (ESI). Val-
ues m/z are given for the most abundant isotopes only. CHN analyses
were measured with an Elementar Vario Micro Cube or an Elementar
Vario EL. A Shimadzu UV-1601 PC spectrophotometer and a Varian
Cary Eclipse spectrofluorometer were used to acquire absorption and
emission spectra. Absolute fluorescence quantum yields were deter-
mined in aerated solvents by a PTI QuantaMaster 40 UV/VIS spectro-
fluorometer equipped with an integrating sphere. The provided correc-
tions for excitation and emission were applied. Cyclic voltammetry
was performed with a Princeton Applied Research VersaSTAT 3 po-
tentiostat under inert conditions at room temperature in absolute
CH2Cl2 containing nBu4NPF6. A self-made 3-electrode set-up with
two platinum wires as working and counter electrodes and a silver
wire as quasi-reference electrode was used and ferrocene as internal
standard had been added. Single crystal X-ray diffraction studies were
performed with an Oxford Diffraction Xcalibur E (18), or an Oxford
electron transfer from the BODIPY radical anion to the dirho-
dium core. However, further spectroelectrochemical and pho-
tophysical studies are necessary here to support this point.
Conclusions
The study has shown that BODIPY carboxylate ligands are
readily prepared if aromatic or unsaturated linkers are placed
between the luminophor and the CO2H group. Even function-
alized systems are available by Palladium catalyzed Sonoga-
shira- and Stille coupling protocols. However, the latter reac-
tion requires the use of benzyl protection groups for carboxy
and hydroxyl substituents. Depending on the site and type of
the carboxylic acid group attachement different relative orien-
tations of the BODIPY plane and the CO2 plane are accessible.
Paddle wheel type dinuclear complexes form with divalent Diffraction Xcalibur (3, 13, 23, 24, 25). All structures were solved
with SIR-92[18] or SHELXS,[19] and refined with SHELXL.[20]
copper and rhodium ions in good yields. While research on the
WinGX[21] and Mercury[22] were used during refinement and analysis
copper derivatives is hampered by an extremely low solubility,
of the crystallographic data. A summary of the crystallographic data
rhodium carboxylates with appended BODIPY units can be
and structure refinement results are listed in Table 3
dissolved undecomposed in many solvents. First investigations
suggest the antenna function of the BODIPY units with respect
to energy and electron transfer processes. This functionality
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
offers much potential for future studies on BODIPY-appended Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-1418580, CCDC-1418581, CCDC-1418582,
paddle wheel complexes.
CCDC-1418583, CCDC-1418584, and CCDC-1424950 (for 3, 18, 23,
24, 25, and 13, respectively) (Fax: +44-1223-336-033; E-Mail:
deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
Experimental Section
General: Solvents were dried according to standard procedures in an
inert gas atmosphere of argon or nitrogen. All reagents were purchased 1,2,3,5,6,7-Hexamethyl-8-(4-carboxyphenyl)-BODIPY (3): 2,3,4-
from commercial sources in reagent grade and used as received. NMR Trimethylpyrrole (2.29 g, 21 mmol) and 4-formylbenzoic acid (1.50 g,
spectra were obtained with a Bruker DPX 200, a Bruker Avance II 300, 10 mmol) in dichloromethane (650 mL) were treated with trifluoro-
a Bruker DRX 400, a Bruker Avance III 400, and a Bruker Avance II
acetic acid (20 μL) and stirred for 4 h under inert conditions. DDQ
600 spectrometer with room temperature as measuring temperature. (2.21 g, 9.8 mmol) was added, and the mixture was stirred for an ad-
Chemical shifts (δ) are given in ppm relative to residual protio solvent
Table 3. Selected crystallographic data for 3, 13, 18, 23–25.
ditional 15 min before triethylamin (12 mL, 86 mmol), followed by
3
13
18
23·4THF
24
25·2C6H4Cl2·4CH3OH
Formula
C22H23BF2N2O2 C21H21BF2N2O2 C31H28BF2IN2O2 C112H136B4Cu2F8N8O14 C54H54B2CuF4N6O4 C106H118B4Cl4F8N8O14Rh2
Mr /g·mol–1
396.23
382.20
¯
636.26
¯
2140.60
¯
1012.20
P21/c
2270.94
P21/c
¯
Space group P1
P1
P1
P1
a /Å
b /Å
c /Å
α /°
β /°
γ /°
6.7449(6)
7.7593(4)
14.2596(6)
16.6737(6)
93.617(4)
95.738(4)
104.261(4)
1771.67(14)
4
8.7562(16)
9.047(2)
18.562(5)
84.48(2)
82.79(2)
75.477(16)
1409.0(6)
2
13.2863(7)
14.0673(8)
17.5167(8)
95.231(4)
95.681(4)
118.117(6)
2837.7(3)
1
7.8961(2)
15.7848(2)
20.5179(5)
90
106.648(2)
90
2450.12(9)
2
1.372
10.6057(8)
35.2660(14)
14.9508(16)
90
111.689(7)
90
5196.0(7)
2
1.451
9.0266(6)
17.3846(16)
84.132(6)
81.279(8)
89.325(8)
1040.71(15)
2
V /Å3
Z
dcalcd. /g·cm–3 1.264
1.433
0.879
1.500
1.181
1.253
1.088
μ /mm–1
0.766
1.199
4.194
2θ limits /°
Measured
4.93–75.78
12980
3.21–76.17
38137
4.44–50.0
13552
3.61–78.32
46026
3.58–75.46
10994
3.42–75.78
46812
Independent 4279
7374
6333
517/0
4963
3809
361/6
11735
8691
695/56
10994
9943
326/0
9830
7975
677/0
Observeda)
Parameters/
restraints
3704
272/0
b)
R1 all data
0.0466
0.1076
0.0516
0.1149
0.1246
0.1730
0.0978
0.2146
0.0554
0.1480
0.0776
0.1727
c)
wR2
a) Observation criterion: I Ͼ 2σ(I). b) R1 = Σ||Fo|–|Fc||/Σ|Fo|. c) wR2 = {Σ[w(Fo –Fc ) ]/Σ[w(Fo ) ]}1/2
.
2
2 2
2 2
Z. Anorg. Allg. Chem. 2016, 107–117
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ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
BF3·OEt2 (16 mL, 170 mmol) were added. After 2 h the fluorescent 154.9, 151.0, 141.9, 139.1, 136.6, 136.1, 132.8, 131.8, 130.4, 129.8,
mixture was treated with NaHCO3 solution, extracted with dichloro- 128.7, 128.6, 128.3, 128.2, 121.9, 66.7, 17.5, 16.9, 15.3, 14.5, 13.1.
methane, and the organic layer was dried with Na2SO4. After removal 11B NMR (96 MHz, CDCl3): δ = 0.92 (t, JBF = 32.7 Hz, 1B, BF2). 19
F
of the solvent, the residue was subjected to column chromatography NMR (188 MHz, CDCl3): δ = –146.9 (q, JBF = 32.6 Hz, 2F, BF2). MS
on silica with CH2Cl2/MeOH 99/1 to yield the title compound (1.85 g, (ESI): m/z = 473 ([M + H]+). UV/Vis λabs (ε[rel]) = 364 (0.07), 508
1
4.66 mmol, 13%). H NMR (400 MHz, CDCl3): δ = 8.25 (d, 2 H, J
= 8.4 Hz, Ar–H), 7.44 (d, 2 H, J = 8.4 Hz, Ar–H), 2.53 (s, 6 H, CH3),
1.85 (s, 6 H, CH3), 1.27 (s, 6 H, CH3). 13C NMR (100 MHz, CDCl3):
δ = 171.1, 154.7, 141.7, 138.5, 138.3, 130.9, 130.1, 129.7, 128.9,
126.8, 12.7, 12.1, 9.0. 19F NMR (376 MHz, CDCl3): δ = –146.2 ppm
(q, JBF = 33 Hz, 2F; 2ϫBF2). 11B NMR (128 MHz, CDCl3): δ =
0.99 ppm (t, JBF = 33 Hz, 1B; BF2). MS (ESI): m/z = 395 ([M]+). UV/
(1); λem (λexc: 508 nm) = 536 nm.
2-(4-Benzyloxycarbonylphenyl)-1,3,5,7-tetramethyl-8-mesityl-
BODIPY (12): 2-IodoBODIPY 9[26] (200 mg, 0.41 mmol),
4-stannylbenzoic acid benzylester 10[25] (250 mg, 0.50 mmol) and
Pd(PPh3)4 (10 mg, 8 μmol) in dry toluene were heated to 100 °C for
24 h. After removal of the solvent the mixture was subjected to silica
chromatography with dichloromethane/pentane 1:1 to yield the title
Vis (CH2Cl2): λabs (ε[rel]) = 380 (8600), 528 (65500); λem (λex
528 nm) = 550 nm. C22H23BF2N2O2: calcd. C 66.69, H 5.85, N 7.07%;
found: C 66.58, H 6.01, N 7.21%.
=
1
compound (216 mg, 0.38 mmol, 93%). H NMR (300 MHz, CDCl3):
δ = 8.19 (d, 2H, J = 8.6 Hz, Ar–H), 7.35–7.31 (m, 2H, Bn–H), 7.23–
7.13 (m, 2H, Bn–H), 6.97 (d, 2H, J = 8.6 Hz, Ar–H), 6.79 (s, 2H,
Mesityl-H), 5.77 (s, 1H, β-H), 5.29 (s, 2H, CH2Ph), 2.75 (s, 3H, CH3),
2.73 (s, 3H, CH3), 2.16 (s, 3H, CH3), 2.11 (s, 6H, CH3), 1.50 (s, 3H,
CH3), 1.46 (s, 3H, CH3). 11B NMR (96 MHz, CDCl3): δ = 1.74 (t, J
= 32.5 Hz, 1B, BF2). 19F NMR (188 MHz, CDCl3): δ = –146.7 (q,
JBF = 31.9 Hz, 2F, BF2). MS (ESI): m/z = 599 ([M + H]+). UV/Vis
λabs (ε[rel]): 278 (0.30), 368 (0.07), 515 (1.0) nm; λem (λexc: 515 nm)
= 536 nm.
8-(4-(2,5-Bisbenzyloxy)benzoic
Acid
Benzylate)-1,3,5,7-tetra-
methyl-BODIPY (6): Benzaldehyde 4 (453 mg, 1.00 mmol) and pyr-
role 5[23] (215 mg, 2.25 mmol) in dry dichloromethane (250 mL) were
treated with trifluoroacetic acid (15 μL) and stirred for 8 h. DDQ
(227 mg, 1.00 mmol) was added and stirring was continued for 30 min
bevor triethylamine (0.85 mL, 6.00 mmol) and boron trifluoride
etherate (1.35 mL, 13.0 mmol) were added. After 3 h sodium hydrogen
carbonate solution was added, the organic layer was separated, dried
with MgSO4 and purified by silica chromatography with dichlorometh-
ane. Recrystallization from ethyl ether at –20 °C yields 234 mg
(0.35 mmol, 35%). 1H NMR (400 MHz, CDCl3): δ = 7.57 (s, 1 H,
Ar–H), 7.44 – 7.15 (m, 15 H, Bn–H), 6.89 (s, 1 H, Ar–H), 5.95 (s, 2
H, β-H), 5.37 (s, 2 H, CH2Ph), 5.09 (s, 2 H, CH2Ph), 5.06 (s, 2 H,
CH2Ph), 2.56 (s, 6 H, CH3), 1.33 (s, 6 H, CH3). 13C NMR (100 MHz,
CDCl3): δ = 165.5, 155.6, 153.1, 149.0, 142.5, 136.8, 136.5, 136.1,
135.8, 130.9, 129.7, 128.6, 128.6, 128.5, 128.4, 128.3, 127.9, 127.2,
127.1, 121.6, 121.1, 116.8, 116.2, 71.4, 70.7, 67.1, 14.6, 14.0. 11B
NMR (128 MHz, CDCl3): δ = 1.00 (t, JBF = 33.0 Hz, 1B, BF2). 19F
NMR (376 MHz CDCl3): δ = –146.2 (dq, JFF = 110, JBF = 32.8 Hz,
1F, BF1F2), 145.3 (dq, JFF = 110, JBF = 32.9 Hz, 1F, BF1F2). MS
(ESI+): m/z = 671 ([M + H]+). UV/Vis (CH2Cl2): λabs (ε) = 309
2-(4-Carboxyphenyl)-1,3,5,7,8-pentamethyl-BODIPY (13): Benzyl
protected BODIPY 11 (100 mg, 0.21 mmol) in ethanol and Pd/C
(10 mg) was stirred for 2 h under a blanket of hydrogen. The solvent
was removed and the residue purified by silica chromatography with
dichloromethane/methanol 99:1 (yield: 79 mg, 0.206 mmol, 98%). 1H
NMR (200 MHz, [D6]DMSO): δ = 8.04 (d, J = 8.1 Hz, 2H, Ar-H),
7.40 (d, J = 8.1 Hz, 2H), 6.30 (s, 1H, β-H), 2.69 (s, 3H, CH3), 2.45 (s,
6H, CH3), 2.38 (s, 3H, CH3), 2.34 (s, 3H, CH3). 11B NMR (96 MHz,
[D6]DMSO): δ = 0.90 (t, J = 34.1 Hz, 1B, BF2). 19F NMR (188 MHz,
[D6]DMSO): δ = –143.1 (m, 2F, BF2). MS (ESI): m/z = 381 ([M –
H]+). UV/Vis λabs (CH2Cl2, ε[L mol–1 cm–1]) = 303 (8300), 365
( 6 20 0 ) , 5 0 8 ( 9 10 0 0 ) n m ; λe m ( λe x c : 509 nm) = 536 nm.
C21H21BF2N2O2·0.5H2O: calcd. C 64.47, H 5.67, N 7.16%; found: C
63.77, H 5.57, N 7.09%.
(9900), 506 (68400) nm; λem (λex
=
506 nm)
=
528 nm.
C41H37BF2N2O4·0.5Et2O: calcd. C 72.99, H 5.98, N 3.96%; found: C
73.21, H 6.31, N 3.72%.
2-(4-Carboxyphenyl)-1,3,5,7-tetramethyl-8-mesityl-BODIPY (14):
Benzyl protected BODIPY 11 (200 mg, 0.35 mmol) in ethanol and Pd/
C (10 mg) was stirred for 2 h under a blanket of hydrogen. The solvent
was removed and the residue purified by silica chromatography with
dichloromethane/methanol 99:1 (yield: 162 mg, 0.33 mmol, 94%). 1H
NMR (400 MHz, CDCl3): δ = 8.12 (d, 2H, J = 8.4 Hz, Ar-H), 7.29
(d, 2H, J = 8.4 Hz, Ar-H), 6.96 (s, 2H, Mes-H), 6.02 (s, 1H, β-H),
2.59 (s, 3H, CH3), 2.54 (s, 3H, CH3), 2.33 (s, 3H, CH3), 2.14 (s, 6H,
CH3), 1.41 (s, 3H, CH3), 1.34 (s, 3H, CH3). 13C NMR (100 MHz,
CDCl3): δ = 171.4, 156.5, 152.4, 143.4, 142.3, 139.9, 138.8, 137.8,
134.8, 131.6, 131.3, 131.1, 130.3, 130.2, 130.0, 129.1, 127.6, 121.5,
21.2, 19.6, 14.7, 13.5, 13.3, 11.5. 11B NMR (128 MHz, CDCl3): δ =
1.10 (t, JBF = 32.4 Hz, 1B, BF2). 19F NMR (376 MHz, CDCl3): δ =
–146.6 (q, JBF = 31.3 Hz, 2F, BF2). MS (ESI): m/z = 485 ([M – H]+).
UV/Vis λabs (ε[L mol–1 cm–1]) = 311 (7000), 515 (77700) nm; λem
(λexc: 515 nm) = 534 nm. C29H29BF2N2O2·H2O: calcd. C 69.06, H
6.20, N 5.55%; found: C 68.88, H 6.59, N 5.84%.
8-(4-(2,5-Bishydroxy)benzoic acid)-1,3,5,7-tetramethyl-BODIPY
(7): BODIPY 6 (25 mg, 37 μmol) and Pd/C were treated with
hydrogen gas in ethanol (15 mL) for 30 min. The mixture was filtered
with ethanol and the eluate taken to dryness whereupon the product
remained as a red solid (yield: 13.6 mg, 34 μmol, 92%). Attempts to
purify the compound led to decomposition. 1H NMR (300 MHz,
[D6]DMSO): δ = 9.65 (br. s, 1 H, COOH), 7.40 (s, 1 H,Ar–H), 6.78
(s, 1 H, Ar–H), 6.17 (s, 2 H, β-H), 3.17 (s, 2 H, OH), 2.44 (s, 6 H,
2ϫCH3), 1.54 (s, 6 H, 2ϫCH3). 11B NMR (96 MHz, [D6]DMSO): δ
= 1.33 (t, JBF = 32.2 Hz, 1B, BF2). UV/Vis (THF): λabs (ε[rel]) = 308
(0.2), 335 (0.17), 502 (1); λem (λex = 502 nm) = 519 nm.
2-(4-Benzyloxycarbonylphenyl)-1,3,5,7,8-pentamethyl-BODIPY
(11): 2-IodoBODIPY 8[24] (141 mg, 0.41 mmol), stannylbenzoic acid
benzylester 10[25] (250 mg, 0.50 mmol), and Pd(PPh3)4 (10 mg,
8 μmol) in dry toluene were heated to 100 °C for 24 h. After removal
of the solvent the mixture was subjected to silica chromatography with 1,3,5,7-Tetramethyl-8-mesityl-2-((4-carboxyphenyl)-ethinyl)-
dichloromethane/pentane 1:1 to yield the title compound (140 mg,
0.30 mmol, 72%). H NMR (400 MHz, CDCl3): δ = 8.14 (d, 2 H, J
BODIPY (17): 2-Iodo-BODIPY 9[26] (168 mg, 0.34 mmol), 4-ethinyl-
benzoic acid 16[27] (50 mg, 0.34 mmol), Pd(PPh3)4 (15 mg, 13 μmol),
1
= 8.5 Hz, Ar–H), 7.47 (m, 2 H, Bn–H), 7.40 (m, 3 H, Bn–H), 7.29 (d, and copper(I)iodide (10 mg, 52 μmol) in dry THF (8 mL) and Hünig
2 H, J = 8.5 Hz, Ar–H), 6.11 (s, 1 H, β-H), 5.40 (s, 2 H, CH2Ph), 2.65 base (2 mL) were stirred at 55 °C for 24 h. After cooling the solvent
(s, 3 H, CH3), 2.55 (s, 3 H, CH3), 2.47 (s, 3 H, CH3), 2.45 (s, 3 H,
CH3), 2.32 (s, 3 H, CH3). 13C NMR (100 MHz, CDCl3): δ = 166.3,
was removed in vacuo and the residue was subjected to silica
chromatography with ethyl ether/n-hexane 2:1 + 1 % acetic acid.
Z. Anorg. Allg. Chem. 2016, 107–117
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Journal of Inorganic and General Chemistry
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ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Recrystallization from ethyl acetate/n-hexane yields the title compound cooling the solvent was removed in vacuo and the residue was sub-
(120 mg, 0.23 mmol, 69%). 1H NMR (300 MHz, CDCl3): δ = 8.04
jected to silica chromatography with dichloromethane/pentane 1:1 to
(d, 2 H, J = 8.5 Hz, Ar-H), 7.52 (d, 2 H, J = 8.5 Hz, Ar-H), 6.98 (s, 2 yield the title compound (313 mg, 0.43 mmol, 79 %). 1H NMR
H, Mes-H), 6.04 (s, 1 H, β-H), 2.71 (s, 3 H, CH3), 2.59 (s, 3 H, CH3),
2.36 (s, 3 H, CH3), 2.10 (s, 6 H, CH3), 1.53 (s, 3 H, CH3), 1.42 (s, 3
H, CH3). 13C NMR (100 MHz, CDCl3): δ = 170.6, 158.1, 156.0, 144.5,
142.3, 141.9, 138.9, 132.1, 131.1, 130.7, 130.1, 129.4, 129.3, 129.1,
(600 MHz, CDCl3): δ = 7.75 (s, 1 H, Ar-H), 7.43 (m, 8 H, Bn-H), 7.30
(m, 2 H, Bn-H), 7.17 (s, 1 H, Ar-H), 6.98 (s, 2 H, Mes-H), 6.04 (s, 1
H, β-H), 5.24 (s, 2 H, CH2Ph), 5.18 (s, 2 H, CH2Ph), 2.58 (s, 6 H,
CH3), 2.38 (s, 3 H, CH3), 2.07 (s, 6 H, CH3), 1.42 (s, 3 H, CH3), 1.37
127.9, 122.1, 113.9, 95.1, 86.2, 21.2, 19.5, 14.8, 13.6, 13.5, 12.1. 11B (s, 3 H, CH3). 13C NMR (150 MHz, CDCl3): δ = 164.8, 158.2, 153.7,
NMR (128 MHz, CDCl3): δ = 0.92 (t, J = 31.8 Hz, 1B, BF2). 19F
NMR (376 MHz, CDCl3): δ = –146.8 (q, J = 32.8 Hz, 2F, BF2). MS
151.1, 142.3, 138.9, 136.0, 134.8, 134.1, 130.7, 129.3, 129.2, 129.2,
129.1, 128.5, 128.4, 128.3, 128.2, 128.1, 127.9, 120.3, 116.9, 115.6,
91.3, 91.1, 73.2, 71.1, 21.2, 19.5, 15.8, 14.8, 13.6, 13.4, 12.0. 11B
NMR (128 MHz, CDCl3): δ = 0.88 (t, JBF = 33.2 Hz, 1B, BF2, BF2).
(ESI+) m/z = 509 ([M – H]+). UV/Vis (CH2Cl2): λabs (ε[L·mol–1
·
cm–1]) = 343 (9700), 533 (42100) nm. λem (λexc: 533 nm) = 559 nm.
C
31H29BF2N2O2·0.75C4H8O2: calcd. C 70.84, H 6.12, N 4.86 %; 19F NMR (376 MHz, CDCl3): δ = –146.8 (q, JBF = 33.1 Hz, 2F, BF2).
found: C 71.19, H 5.79, N 4.52%.
MS (ESI+): m/z = 703 ([M-F]+). UV/Vis (CH2Cl2): λabs (ε [rel]) = 300
(11700), 372 (14200), 538 (34400) nm. λem (λexc = 538 nm) = 569 nm.
C45H41BF2N2O4·H2O: calcd. C 72.98, H 5.85, N 3.78 %; found: C
73.40, H 5.58, N 3.89%.
2-Iod-6-(ethinyl(4-carboxyphenyl))-1,3,5,7-tetramethyl-8-mesityl-
BODIPY (18): 2,6-Diiodo-BODIPY 15[28] (85 mg, 0.14 mmol), 4-
ethinylbenzoic acid 16[27] (50 mg, 0.34 mmol), Pd(PPh3)4 (10 mg,
8 μmol), and CuI (4 mg, 21 μmol) were heated in dry THF (5 mL) and
Hünig base (1.5 mL) to 60 °C for 24 h. After cooling the solvent was
removed in vacuo and the residue was subjected to silica chromatog-
raphy with dichloromethane/pentane 1:1 and recrystallized from ethyl
acetate/n-hexane to yield the title compound (70 mg, 0.11 mmol,
79%). 1H NMR (400 MHz, CDCl3): δ = 8.05 (d, 2 H, J = 8.6 Hz, Ar-
H), 7.53 (d, 2 H, J = 8.6 Hz, Ar-H), 6.99 (s, 2 H, Mes-H), 2.72 (s, 3
H, CH3), 2.67 (s, 3 H, CH3), 2.37 (s, 3 H, CH3), 2.09 (s, 6 H, CH3),
1.53 (s, 3 H, CH3), 1.44 (s, 3 H, CH3). 13C NMR (100 MHz, CDCl3):
δ = 166.9, 154.1, 152.5, 144.7, 142.5, 139.3, 134.8, 131.4, 131.2,
130.6, 129.3, 129.1, 128.2, 127.8, 127.8, 127.7, 121.7, 95.7, 85.5, 21.2,
19.5, 16.1, 15.8, 13.7, 12.4. 11B NMR (128 MHz, CDCl3): δ = 0.81
(t, 1B, JBF = 32.0 Hz, 1B, BF2). 19F NMR (376 MHz, CDCl3): δ =
–146.5 (q, JBF = 31.9 Hz, 2F, BF2). MS (ESI+): m/z = 617 ([M-F]+).
UV/Vis (CH2Cl2): λabs (ε[L·mol–1·cm–1]) = 298 (14200), 339 (12900),
393 (9800), 553 (64900) nm. λem (λexc = 553 nm) = 580 nm.
Copper Paddlewheel Complex 23: BODIPY carboxylic acid 3
(44.8 mg, 0.11 mmol) in THF (6 mL) and triethylamine (100 μL) was
carefully layered with
a solution of copper(II)triflate (7.5 mg,
0.02 mmol) in THF (1.5 mL) and left for 3 d. At the interphase small
crystals formed, which were collected, washed with hexane, and dried
to yield the title compound as a THF solvate (25 mg, 13.5 μmol, 67%).
C88H88B4Cu2F8N8O8: calcd. C 61.88, H 5.19, N 6.56%; found: C
61.28, H 5.38, N 6.34%.
Bispyridin Copper Complex 24: Copper(II)triflate (5 mg, 13.8 μmol)
and BODIPY carboxylic acid 3 (12 mg, 30 μmol) were dissolved in
THF (2 mL) and triethylamine (20 μL) and left in a pyridine saturated
atmosphere for one week. The title compound forms red-brownish
crystals which were collected, washed with n-hexane, and dried to
yield 6 mg (6 μmol, 43%) of 24.
Rhodium Paddlewheel Complex 25: BODIPY carboxylic acid 3
(224 mg, 0.57 mmol) and rhodium acetate (50 mg, 0.11 mmol) were
heated in 1,2-dichlorobenzene (20 mL) and methanol (20 μL) to
150 °C for 4 h. After removal of the solvents in vacuo the residue
was purified by silica chromatography with dichloromethane + 0.5%
C
45H41BF2N2O4·C4H8O2·C6H14: calcd. C 60.75, H 6.22, N 3.46 %;
found: C 60.92, H 6.32, N 3.27%.
2-(1-Ethinyl-1Ј-ferrocenyl carboxylic acid)-1,3,5,7-tetramethyl-8-
mesityl-BODIPY (20): 2-Iodo-BODIPY 9[26] (100 mg, 0.20 mmol),
ethinylferrocenyl carboxylic acid 19[29] (64 mg, 0.25 mmol),
Pd(PPh3)4 (20 mg, 18 μmol), and copper(I)iodide (10 mg, 52 μmol)
were heated in dry THF. (12 mL) and Hünig base (3 mL) to 55 °C for
24 h. After cooling the solvent was removed in vacuo and the residue
was subjected to silica chromatography with ethyl ether/n-hexane 2:1
+ 2 % methanol to yield the title compound (107 mg, 0.17 mmol,
1
methanol to yield the title compound (139 mg, 77.8 μmol, 71%). H
NMR (400 MHz, CDCl3): δ = 8.12 (d, 8 H, J = 8.3 Hz, Ar-H), 7.23
(d, 8 H, J = 8.3 Hz, Ar-H), 2.49 (s, 24 H, CH3), 1.80 (s, 24 H, CH3),
1.12 (s, 24 H, CH3). 13C NMR (100 MHz, CDCl3): δ = 184.8, 154.4,
139.9, 138.8, 138.5, 131.3, 130.1, 129.9, 127.9, 126.5, 12.7, 12.2, 8.9.
11B NMR (128 MHz, CDCl3): δ = 0.94 (t, J = 32.6 Hz, 4B, BF2). 19F
NMR (376 MHz, CDCl3): δ = –146.2 (m, 8F, BF2). MS (ESI): m/z =
1767 ([M-F]+). UV/Vis (CH2Cl2): λabs (ε[L·mol–1·cm–1]) = 323
(23300), 380 (24700), 528 (190600) nm. λem (λexc: 500 nm) = 513 nm;
λem (λexc: 528 nm) = 555. C90H96B4F8N8O10·2H2O: calcd. C 57.29, H
5.34, N 5.94%; found: C 57.08, H 5.18, N 6.17%.
1
87%). H NMR (300 MHz, CDCl3): δ = 6.97 (s, 2 H, Mes-H,), 6.01
(s, 1 H, β-H), 4.85 (m, 2 H, Cp-H), 4.48(m, 4 H, Cp-H), 4.30 (m, 2
H, Cp-H), 2.68 (s, 3 H, CH3), 2.58 (s, 3 H, CH3), 2.35 (s, 3 H, Mes-
para-CH3), 2.10 (s, 6 H, Mes-ortho-CH3), 1.51 (s, 3 H, CH3), 1.40 (s,
3H, CH3). 13C NMR (75 MHz, CDCl3): δ = 176.5, 143.6, 142.0, 138.8,
134.8, 132.2, 132.0, 131.6, 130.8, 130.7, 129.3, 129.1, 128.6, 128.5,
121.5, 77.7, 72.9, 71.8, 71.6, 70.5, 67.7, 21.2, 19.5, 14.7, 14.1, 13.5,
12.3. 11B NMR (128 MHz, CDCl3): δ = 0.90 (t, J = 31.8 Hz, 1B, BF2).
19F NMR (376 MHz, CDCl3): δ = - 146.8 (q, J = 31.2 Hz, 2F, BF2).
MS (ESI-) m/z = 617 ([M – H]+). UV/Vis (CH2Cl2): λabs (ε[L·
Rhodium Paddlewheel Complex 26: BODIPY carboxylic acid 13
(75 mg, 0.20 mmol) and rhodium acetate (20 mg, 0.05 mmol) were
heated in 1,2-dichlorobenzene (15 mL) and methanol (20 μL) to
150 °C for 4 h. After removal of the solvents in vacuo the residue
was purified by silica chromatography with dichloromethane + 0.5%
methanol to yield the title compound (62 mg, 35.8 μmol, 72%). 1H
NMR (400 MHz, CDCl3): δ = 7.39 (d, 4 H, J = 3.6 Hz, Ar-H), 7.37
(d, 4 H, J = 3.6 Hz, Ar-H), 7.14 (d, 4 H, J = 3.6 Hz, Ar-H), 7.12 (d,
mol–1·cm–1]) = 289 (6400), 375 (4000), 533 (21700) nm. λem (λexc
533 nm) = 552 nm. C35H33BF2FeN2O2·2CH3OH: calcd. C 65.12, H
6.06, N 4.11%; found: C 64.85, H 6.32, N 4.32%.
:
2-(4-Ethinyl-(2,5-(bisbenzyloxy)carboxyphenyl))-1,3,5,7-tetra- 4 H, J = 3.6 Hz, Ar-H), 6.00 (s, 4 H, β-H), 2.50 (s, 6 H, CH3), 2.45
methyl-8-mesityl-BODIPY (22): 2-Iodo-BODIPY 9[26] (270 mg,
(s, 12 H, CH3), 2.32 (s, 12 H, CH3), 2.29 (s, 6 H, CH3), 2.14 (s, 12
0.55 mmol), 4-ethinylbenzoic acid derivative 21 (140 mg, 0.39 mmol), H, CH3). 13C NMR was not measured due to the insufficient solubility
Pd(PPh3)4 (10 mg, 8 μmol) and CuI (4 mg, 21 μmol) in dry THF
of 26. 11B NMR (128 MHz, CDCl3): δ = 0.83 (m, 4B, BF2). 19F NMR
(10 mL) and Hünig base (3 mL) were stirred at 60 °C for 24 h. After (376 MHz, CDCl3): δ = –146.7 (m, 8F, BF2). MS (ESI): m/z = 1753
Z. Anorg. Allg. Chem. 2016, 107–117
115
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Journal of Inorganic and General Chemistry
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ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
([M + Na]+). UV/Vis (CH2Cl2): λabs (ε[L·mol–1·cm–1]) = 308 (36600),
2041–2047; l) F. A. Cotton, L. R. Falvello, A. H. Reid Jr., J. H.
Tocher, J. Organomet. Chem. 1987, 319, 87–97; m) F. A. Cotton,
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366 (23900), 511 (269600) nm. λem (λexc: 511 nm) = 536 nm.
C84H80B4F8N8O8·2MeOH: calcd. C 57.55, H 4.94, N 6.24%; found:
C 57.76, H 5.12, N 6.34%.
Rhodium Paddlewheel Complex 27: BODIPY carboxylic acid 14
(96 mg, 0.20 mmol) and rhodium acetate (20 mg, 0.05 mmol) were
heated in 1,2-dichlorobenzene (10 mL) and methanol (20 μL) to
150 °C for 4 h. After removal of the solvents in vacuo the residue
was purified by silica chromatography with dichloromethane + 0.5%
methanol to yield the title compound (70 mg, 32.6 μmol, 72%). 1H
NMR (400 MHz, CDCl3): δ = 7.96 (d, 8 H, J = 8.4 Hz, Ar-H), 7.05
(d, 8 H, J = 8.4 Hz, Ar-H), 6.91 (s, 8 H, Mes-H), 6.01 (s, 4 H, β-H),
2.56 (s, 12 H, CH3), 2.41 (s, 12 H, CH3), 2.30 (s, 12 H, Mes-CH3),
2.08 (s, 24 H, Mes-CH3), 1.38 (s, 12 H, CH3), 1.21 (s, 12 H, CH3).
13C NMR (100 MHz, CDCl3): δ = 185.0, 156.1, 152.8, 143.1 142.1,
138.7, 138.1, 138.0, 137.9, 134.8, 132.0, 131.1, 130.0, 129.8, 129.4,
129.1, 129.0, 121.0, 31.1, 21.2, 19.5, 14.7, 13.5, 11.4. 11B NMR
(128 MHz, CDCl3): δ = 1.03 (m, 4B, BF2). 19F NMR (376 MHz,
CDCl3): δ = –146.6 (m, 8F, BF2). MS (ESI): m/z = 2146 ([M]+). UV/
Vis (CH2Cl2): λabs (ε[L·mol–1·cm–1]) = 269 (61700), 368 (26000), 517
(358600) nm. λem (λexc: 517 nm) = 537 nm. C116H112B4F8N8O8·
2CH3OH: calcd. C 64.09, H 5.47, N 5.07%; found: C 64.27, H 5.24,
N 5.10%.
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Rhodium Paddlewheel Complex 28: BODIPY carboxylic acid 17
(80 mg, 157 μmol) and rhodium acetate (15 mg, 34 μmol) were heated
in 1,2-dichlorobenzene (10 mL) and methanol (20 μL) to 150 °C for 4
h. After removal of the solvents in vacuo the residue was purified by
silica chromatography with dichloromethane + 0.5% methanol to yield
the title compound (54 mg, 24 μmol, 73%). 1H NMR (400 MHz,
CDCl3): δ = 7.87 (d, 6H, J = 8.4 Hz, Ar-H), 7.45 (dd, 2H, J1 = 3.5, J2
= 6.0 Hz, Ar-H), 7.30 (d, 6H, J = 8.4 Hz, Ar-H), 7.21 (dd, 2H, J1 =
3.5, J2 = 6.0 Hz, Ar-H), 6.94 (s, 8H, Mes-H), 6.02 (s, 4H, β-H), 2.65
(s, 12H, CH3), 2.57 (s, 12H, CH3), 2.33 (s, 12H, Mes-CH3), 2.06 (s,
24H, Mes-CH3), 1.46 (s, 12H, CH3), 1.39 (s, 12H, CH3). 13C NMR
(100 MHz, CDCl3): δ = 184.7, 157.8, 156.1, 144.2, 142.3, 141.9,
138.9, 134.8, 132.6, 131.9, 130.7, 130.5, 130.3, 130.0, 129.3, 129.1,
129.0, 127.7, 127.6, 121.9, 114.1, 95.4, 85.2, 21.2, 19.5, 14.8, 13.6,
13.5, 12.1. 11B NMR (128 MHz, CDCl3): δ = 0.89 (t, J = 30.4 Hz, 4B,
BF2). 19F NMR (376 MHz, CDCl3): δ = –146.9 (m, 8F, BF2). MS
(ESI): m/z = 2306 ([M + 2 MeOH]+). UV/Vis (CH2Cl2): λabs (ε[L·
mol–1·cm–1]) = 298 (64000), 346 (67100), 405 (27600), 537 (234200)
nm. λem (λexc: 537 nm) = 562 nm. HRMS (ESI): m/z calcd. for
C124H112B4F8N8O8Rh2 ([M]2+): 1121.35117; found.: 1121.35072.
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Supporting Information (see footnote on the first page of this article):
Preparation and analysis of precursors 2, 4, and 21.
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Received: September 28, 2015
Published Online: November 26, 2015
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