Synthesis and ligand binding properties of triptycene-linked porphyrin arrays

Article abstract of DOI:10.1016/j.tet.2010.12.025

Multiporphyrin arrays are a complex class of molecules with numerous potential applications in energy transfer, photomedicine, and light harvesting. We have developed a facile/versatile route to a class of triptycene-linked porphyrin arrays via both Suzuk

Full text of DOI:10.1016/j.tet.2010.12.025

Tetrahedron 67 (2011) 1126e1134
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Synthesis and ligand binding properties of triptycene-linked porphyrin arrays
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Eimear M. Finnigan , Regis Rein , Nathalie Solladie , Katja Dahms , Daniel C.G. Gotz ,
Gerhard Bringmann c, Mathias O. Senge a
a School of Chemistry, SFI Tetrapyrrole Laboratory, Trinity College Dublin, Dublin 2, Ireland
Groupe de Synthese de Systemes Porphyriniques, Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse Cedex 4, France
Institut fur Organische Chemie, Universitat Wurzburg, Am Hubland, D-97074 Wurzburg, Germany
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Article history:
Received 19 August 2010
Received in revised form 3 November 2010
Accepted 9 December 2010
Available online 16 December 2010
Multiporphyrin arrays are a complex class of molecules with numerous potential applications in energy
transfer, photomedicine, and light harvesting. We have developed a facile/versatile route to a class of
triptycene-linked porphyrin arrays via both Suzuki and Sonogashira cross-coupling methods, which
makes use of the rigid three-pronged orientation of triptycene to construct trimeric porphyrin arrays
linked either in the meso or b-position with various linker groups. In order to understand the properties
of these potential antenna systems and probe their potential applications, the coordination behavior of
zinc(II) derivatives with mono- and bidentate N-donor ligands was investigated. Depending on ligand
concentration, both one- and two-point binding was observed with a bidentate ligand. Also/in addition,
different cavity sizes, obtained by the use of different linker groups, resulted in differences in the binding
properties of each trimeric system.
Keywords:
Porphyrins
Triptycenes
Suzuki coupling
Sonogashira coupling
Ligand binding
Antenna systems
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
Three types of meso linked triptycenylporphyrin arrays and
a
b-linked system were prepared with varying cavity sizes and
Synthetic multiporphyrin arrays can mimic naturally occurring
tetrapyrrolic aggregates that are involved in photosynthesis, light
harvesting and electron transfer. In nature, the rates of these pro-
cesses are optimized by organizing the active components at ideal
distances and orientations, which is achieved by the use of multi-
ple, non-covalent interactions.1e4 Synthetically this can be achieved
using multiple covalent and/or coordination bonds, which serve to
dramatically increase the association constants between compo-
nents and ensure a well-defined geometry for the resulting
complex.5e7
selected examples were easily metalated with zinc(II). Zinc(II)
porphyrins have a simple coordination chemistry and typically
form 1:1 complexes with N-donor ligands.17 Thus, we also per-
formed initial investigations into the host/guest chemistry of the
zinc(II) triptycenylporphyrin arrays.
2. Results and discussion
2.1. Syntheses
Triptycene and its derivatives possess rigid three-dimensional
frameworks8e10 and thus have potential applications in host/guest
complexes, molecular inclusion compounds and coordination
compounds with unusual geometries.11e14 The 120ꢀ orientation
provided by this framework constitutes a useful linker group for
multichromophore assemblies.15 Consequently, we became in-
terested in using a triptycene unit as a scaffold for the construction
of porphyrin arrays with applications in host/guest chemistry.
Triptycene was earlier used by us for the preparation of triptycene/
quinones for electron transfer studies.16
Triptycene-linked porphyrin trimers were chosen as suitable
candidates for multidentate host/guest chemistry and were first
synthesized using Pd-catalyzed coupling reactions.8 We anticipated
that variation of the porphyrin center-to-center distances would
allow an investigation of the coordination properties of the rigid
trimers. The synthetic route started by preparation of an appro-
priately functionalized triptycene derivative.
Commercially available triptycene 1 was reacted with nitric acid
under reflux according to a procedure by Zhang et al.1 A mixture of
2,6,14- and 2,7,14-trinitrotriptycene was obtained, from which the
former was isolated in 85% yield via column chromatography on
silica gel with dichloromethane/n-hexane (1:1) as eluent. Re-
duction of the nitro residues to amino functions yielded 2,6,14-
triaminotriptycene in quantitative yield. 2,6,14-Triiodotriptycene 2
* Corresponding author. E-mail address: sengem@tcd.ie (M.O. Senge).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.12.025

E.M. Finnigan et al. / Tetrahedron 67 (2011) 1126e1134
1127
was obtained from a Sandmeyer reaction using hydrochloric acid,
sodium nitrite, and potassium iodide (Scheme 1).11
Suzuki cross-coupling reaction16 yielded the respective triporphyrin
triptycene derivatives 3e6c. Slightly better yields were obtained for
coupling of the free-base porphyrin 7b as compared to the conver-
sion of 5b due to difficulties in purification of the zinc(II) tricoupled
products. The free-base trimer 7c could be metalated in situ with
zinc(II) acetate to give the zinc(II) trimer 5c in quantitative yield.
I
i-iii
I
I
1
2
Scheme 1. Synthesis of 2,6,14-triiodotriptycene from triptycene. (i) HNO3 (ii) Pd/C,
NaBH4 (iii)HCl, NaNO2, KI.
Introduction of a boronate or ethyne functionality onto the meso
position of a porphyrin would allow subsequent SuzukieMiyaura
or Sonogashira coupling reactions of these derivatives. The halo-
gen-bearing moiety 2 would thus be coupled to the respective
porphyrins yielding triptycene-linked porphyrin trimers. Several
different porphyrin monomers were synthesized bearing a boronic
ester, an ethyne, and a phenylethyne functionality, respectively.
2.1.1. Suzuki reaction. Porphyrins modified at the meso positions
were obtained via condensation of pyrrole or a pyrrolic derivative
with various aldehydes. A2-type porphyrins with two unsub-
stituted meso positions available for further functionalization, were
synthesized from the respective dipyrromethane precursor fol-
lowing a procedure developed by Lee and Lindsey.12 A nucleophilic
substitution reaction13 yielded trisubstituted A2B-type porphyrins.
Subsequent bromination of the porphyrins with N-bromosuccini-
mide (NBS) then yielded the porphyrin precursors 3a to 6a. meso-
Boronylation was performed according to a procedure by Therien
et al. (Scheme 2).14 For example, the reaction of 5a and 6a with
4,4,5,5-tetramethyl-1,3,2-dioxaborolane proceeded as expected in
12 h. Debromination of the starting material was a competing re-
action. Thus, a 10-fold excess of pinacolborane was used to ensure
a high yield of the boronate porphyrins 5b (56%) and 6b (80%).
The methodology established above was also applicable to the
preparation of triptycene-porphyrin trimers with the porphyrins
joined to the linker unit/triptycene backbone in a
b
-position. Por-
phyrin dimers and trimers with meso- and
b
beb
linkage17,18 have
been intensely studied in recent years, especially due to their re-
warding stereochemical features and unique structural chemistry18
R2
N
N
N
N
3a M = Ni(II), R1 = R2 = phenyl
R1
M
Br
4a M = 2H, R1 = n-butyl, R2 = 4-Me-C6H4
5a M = Zn(II), R1 = R2 = phenyl
6a M = Zn(II), R1 = n-butyl, R2 = 4-Me-C6H4
7a M = 2H, R1 = R2 = phenyl
R2
R1
4,4,5,5-tetramethyl-1,3-dioxaborolane,
PdCl2(PPh3)2,
C2H4Cl2
R2
N
N
M
N
R2
N
R2
I
R2
R1
N
N
N
N
O
O
Pd(PPh3)4, K3PO4
DMF, 100 o
N
M
R1
+
N
M
B
I
N
N
C
R2
R2
N
I
N
2
R2
N
M
3c M = Ni(II), R1 = R2 = phenyl (22 %)
N
3b M = Ni(II), R1 = R2 = phenyl (51 %)
R1
R2
4c M = 2H, R1 = n-butyl, R2 = 4-Me-C6H4 (16 %)
5c M = Zn(II), R1 = R2 = phenyl (27 %)
6c M = Zn(II), R1 = n-butyl, R2 = 4-Me-C6H4 (22 %)
7c M = 2H, R1 = R2 = phenyl (33 %)
4b M = 2H, R1 = n-butyl, R2 = 4-Me-C6H4 (48 %)
5b M = Zn(II), R1 = R2 = phenyl (56 %)
Zn(II)OAc2
(100 %)
6b M = Zn(II), R1 = n-butyl, R2 = 4-Me-C6H4 (80 %)
7b M = 2H, R1 = R2 = phenyl (56 %)
Scheme 2. Synthesis of triptycene-linked porphyrin trimers via SuzukieMiyaura cross-coupling reaction with 2,6,14-triiodotriptycene and boronylporphyrins.
Next, the boronate porphyrins were reacted with 2,6,14-triio-
dotriptycene 2 using the conditions described by Chng et al. for the
preparation of a dibenzofurane-linked porphyrin dimer:15 The
or their fundamental use in electron transfer.17b Using a procedure
similar to the one applied to meso functionalized porphyrins
b-linked porphyrin triptycene systems were accessible as well,

1128
E.M. Finnigan et al. / Tetrahedron 67 (2011) 1126e1134
albeit in lower yield due to the increased sterical hindrance at the
coupling position. For example, 2-([10,30,20]-dioxaborolan-20-yl)-
5,10,15,20-tetraphenylporphyrin (structure not shown)18a,b was
reacted with 2 in the presence of Ba(OH)2 and Pd(PPh3)4 giving the
triptycene derivative 8 in 10% yield.
reaction involving triphenylarsine and tris(dibenzylideneacetone)
dipalladium (0).26b Thus, under mild, non-acidic, non-metalating
conditions, the zinc(II) porphyrins 9b and 10b were coupled with
2,6,14-triiodotriptycene to yield the desired ethynyl- and phenyl-
ethynyl-linkedporphyrintrimers9c (28%) and10c (36%) (Scheme 3).
2.1.2. Sonogashira reaction. Precursors of the Sonogashira coupling
reaction19 required an ethyne moiety to react with the triiodo-
triptycene. The porphyrin monomer 9a was synthesized by a mixed
condensation reaction20 of pyrrole with two different aldehydes.
Here, 3-(trimethylsilyl)propiolaldehyde served as the reactive
aldehyde, whereas, p-tolylaldehyde was chosen because of its
availability and enhanced solubility of p-tolyl-substitued porphyrin
as compared to the respective phenyl derivatives, thus aiding
chromatography. Following a procedure by Seo et al.,21 pyrrole, p-
tolylaldehyde, and 3-(trimethylsilyl)propiolaldehyde were con-
densed in a 4:2.1:2 ratio to yield 9a. Deprotection of the ethyne
group with tetrabutylammonium fluoride (TBAF) then gave the
ethynyl-substituted porphyrin 9b.
2.2. Host/guest properties
In order to understand the behavior of the trimer complexes 5c,
9c, and 10c upon ligand coordination, investigations by UV/vis
spectroscopy were first carried out to determine how the bidentate
ligand, 4,40-bipyridine (bipy) coordinated to a monomeric metal-
loporphyrin (5,10,15,20-tetramesityl-porphyrinato)zinc(II). UV/vis
spectroscopy has been used to elucidate the stoichiometry of bind-
ing, binding constants, and a limited amount of structural in-
formation. Previous studies showed that upon coordination of an
N-donor ligand to a zinc(II) porphyrin, a bathochromic shift of about
10 nm occurred in the Soret region/the Soret band is red-shifted by
about 10 nm indicating a 1:1 binding stoichiometry.27,28 In addition,
1H NMR spectroscopy had shown that at millimolar concentrations
a 2:1 porphyrin/ligand sandwich complex was formed upon addi-
tion of 0.5 equiv of a bidentate ligand.29 The 2:1 complex then opens
up to give the 1:1 open complex in the presence of excess ligand.
The addition of incremental amounts of bipy to (5,10,15,20-tet-
ramesitylporphyrinato)zinc(II) (
methane resulted in a Soret band shift from 420 to 428 nm
e
¼756,600 Mꢁ1 cmꢁ1) in dichloro-
NH
N
N
N
N
N
N
Zn
TMS
(
Dl¼8 nm) with one distinct isosbestic point at 424 nm, clearly
indicating an equilibrium between two defined species (Fig. 1).30
The titration data were analysed using the non-linear regression
analysis program SpecfitÔ, which analyses the entire series of
spectra simultaneously.31 The best/optimum data fit was obtained
for/when applying a 1:1 binding model and resulted in a binding
constant of log K1:1¼4.4ꢂ0.004, which was expected for the for-
mation of an open complex.27,28
HN
9a
9b
UV/vis experiments were carried out on trimers 5c, 9c, and 10c
with mono- and bidentate ligands to determine the coordination
properties of these rigid porphyrin arrays. Bidentate ligands are
capable of displaying multiple binding interactions with these por-
phyrin trimers (Fig. 2). Previous UV/vis and 1H NMR investigations
on porphyrin systems have revealed that dimeric bridging ligand
complexes preferentially adapt the bridged structure at low con-
centrations of ligand, in spite of the fact that the endo side is con-
siderably more accessible than the exo side.28,32 Using/In 1H NMR
spectroscopy, this phenomenon was reflected in/resulted in a high-
NH
N
N
N
N
N
Zn
HN
N
10a
10b
field resonance at
d¼ꢁ5 ppm for the CH2 protons of a 1,4-dia-
zabicyclo[2.2.2]octane ligand (DABCO) tightly bound to two zinc(II)
porphyrins, which was completely absent when monodentate li-
gands were used.27,28,33 Monomeric and dimeric binding have also
been differentiated using UV/vis spectroscopy. Formation of a 1:1
dimer/ligand sandwich complex was accompanied by a 5 nm red-
shift, compared to a 10 nm red-shift in the 1:2 open system, which
was observed with the addition of excess ligand.27 Also, association
constants determined from UV/vis titrations for the formation of
dimeric sandwich complexes are much greater than those for the
corresponding monodentate binding motifs.34
Therefore, a bidentate ligand such as bipy, is capable of forming
a 1:1 trimer/ligand sandwich complex (Fig. 2a), a 1:2 complex,
displaying both sandwich and open complexation (Fig. 2b), and
a 1:3 trimer ligand complex, where all ligands are bound in an open
complex (Fig. 2c).
For preparation of a porphyrin with a phenylethyne functionality
we initially attempted a mixed condensation procedure previously
reported by Fazio et al.22 However, for our target system isolation of
the products turned out to be difficult due to the similar polarities of
the components of the mixtures. Thus, the 4-ethynylphenyl residue
was introduced into 5,15-ditolylporphyrin 10a23 by a nucleophilic
substitution reaction.13 1-Bromo-4-ethynylbenzene was reacted with
n-butyllithium under inert conditions, to yield the desired organo-
lithium reagent. Addition of 5,15-ditolylporphyrin 10a in THF yielded
the desired free-base product in 69% yield. Subsequent treatment
with zinc(II) acetate gave the zinc(II) porphyrin monomer 10b.24
Sonogashira coupling reactions have commonly been used for
the synthesis of porphyrin multicomponent systems.25 The palla-
dium coupling conditions are reasonably attractive as they are per-
formed in neutral to basic conditions, where demetalation does not
occur. However, using copper as a co-catalyst, and under specific
conditions, transmetalation can occur with the zinc(II)porphyrin. In
agreement with Farina Krishnan who reported an improved rate of
the Stille reaction upon addition of triphenylarsine,26a Lindsey et al.
successfully outlined the conditions for a copper-free Sonogashira
2.2.1. Directly linked porphyrin trimer 5c. The absorption spectrum
of the directly linked trimer 5c (
e
¼816,000 Mꢁ1 cmꢁ1) exhibited
a
lmax at 424 nm with a shoulder at 417 nm. This was indicative of
a slight electronic interaction between the porphyrin components.35
Upon titration of 5c with bipy in dichloromethane, two new

E.M. Finnigan et al. / Tetrahedron 67 (2011) 1126e1134
1129
Tol
N
Tol
N
Zn
N
Tol
N
Tol
N
N
Tol
Zn
N
N
Tol
Tol
N
9c (28%)
9b
N
I
Tol
N
Zn
N
N
N
Zn
Tol
N
Tol
AsPh3, Pd2(dba)3
THF, Et3N,
12 h, rt
I
Tol
I
2
Tol
10b
N
N
Zn
N
Tol
N
N
N
Tol
Zn
10c (36%)
N
N
Tol
Scheme 3. Sonogashira coupling reaction of 2,6,14-triiodotriptycene with ethynyl functionalized porphyrins.
(a)
Zn
Zn
N
N
K
1:1
+
N
N
Zn
Zn
N
Zn
Zn
K1:2
(c)
(b)
N
Zn
Zn
N
N
K1:3
N
N
N
N
Zn
Zn
Zn
Zn
N
N
Fig. 1. Changes in the absorption spectra (Soret band spectral region) of (5,10,15,20-
tetramesitylporphyrinato)zinc(II) (1.34ꢃ10ꢁ6 M) recorded in dichloromethane, upon
addition of bipy. Inset: the changes at 428 nm with a 1:1 fit (0e6000 equiv).
Fig. 2. Schematic representation of the species in the equilibria of binding bipy to
a trisporphyrin.

1130
E.M. Finnigan et al. / Tetrahedron 67 (2011) 1126e1134
transitions formed at 430 (Dl¼6 nm) and 433 nm (Dl¼9 nm), with
isosbestic points at 427 and 428 nm, respectively (Fig. 3). Titration
with pyridine resulted in a 9 nm bathochromic shift (Table 1), thus
confirming that the final species in the 5c/bipy solution was the 1:3
open complex.
2.2.2. Ethyne-linked porphyrin trimer 9c. The spectra for compound
9c (
e
¼996,400 Mꢁ1 cmꢁ1) exhibited a lmax at 443 nm. Upon titra-
tion with bipy, a new transition at 449 nm developed and an iso-
sbestic point at 444 nm was identified (Fig. 5). Upon the formation
of a 1:1 complex, the monomer exhibited an 8 nm red-shift. In the
case of dimeric ligands, the formation of a 1:1 open complex was
accompanied by a 10 nm red-shift, whereas the formation of
a sandwich complex resulted in a 5 nm red-shift.28,29,32a,b,d How-
ever, titration with pyridine resulted in an overall bathochromic
shift of 6 nm (Table 2).
Fig. 3. The changes in the absorption spectra (Soret region) of the directly linked
trimer 5c (8ꢃ10ꢁ7 M) upon addition of bipy, recorded in dichloromethane. Inset: the
changes at 433 nm fit to a five-component system.
Table 1
The absorption maxima and binding constants for the complexation between 5c and
mono- and bidentate ligands
Fig. 5. UV/vis titration (Soret region) of the ethyne-linked trimer 9c (9.2ꢃ10ꢁ7 M) with
bipy recorded in dichloromethane (0e70,000 equiv). Inset: The changes at 449 nm
with a 1:2 trimer/ligand fit (0e500 equiv).
lmax (nm)
Log K1:1
Log K1:2
Log K1:3
5c
424, 548, 587
433, 563, 602
433, 563, 602
Table 2
5cþbipy
5.3ꢂ0.03
4.8ꢂ0.18
5.4ꢂ0.03
4.1ꢂ0.22
3.3ꢂ0.02
3.4ꢂ0.23
The absorption maxima and binding constants for the complexation between 5c and
mono- and bidentate ligands
5cþpyr
lmax (nm)
Log K1:1
Log K1:2
Log K1:3
The changes in the spectra with increasing concentrations of
bipy were best described by a five-component system (host, guest,
1:1 host/guest, 1:2 host/guest and 1:3 host/guest) after fitting by
SpecfitÔ, the fit of which is shown as an inset in Fig. 3. The 6 nm
red-shift relative to the absorption of the uncomplexed trimer was
attributed to the 1:2 trimer/ligand complex (Fig. 2b) since it
seemed unlikely that the zinc(II) metal would remain four-co-
ordinate in the presence of excess bipy. The binding constants for
this fit are shown in Table 1.
The binding constants for the 1:1 and 1:2 species were of similar
magnitude and indicated the formation of the more stable sandwich
complexes. The species distribution plot for the five-component
system (Fig. 4) revealed a simultaneous formation of the 1:1 and 1:2
trimer/ligand species at low concentrations of bipy.
8c
443, 567, 614
449, 582, 635
449, 581, 636
8cþbipy
6.18ꢂ0.01
4.62ꢂ0.10
5.14ꢂ0.09
3.95ꢂ0.17
3.79ꢂ0.09
3.43ꢂ0.14
8cþpyr
The binding constants for the formation of the 1:1 and 1:2 9c/
bipy complexes were considerably higher than for the formation of
the 9c/pyr complexes, and indicated the formation of sandwich-
type complexes with the bidentate ligand. The changes in the
spectra were therefore attributed to a five-component system
(host, guest and 1:1, 1:2 and 1:3 host/guest complexes). The bind-
ing isotherm is shown as an inset in Fig. 5.
The species distribution diagram in Fig. 6 obtained from the fit
showed that the 1:1 complex reached 62% formation at only 1 equiv
Fig. 4. The species distribution plot of the directly linked trimer 5c (8ꢃ10ꢁ7 M) upon
the addition of bipy recorded in dichloromethane 0e60 equiv.
Fig. 6. The species distribution diagram of the ethyne-linked trimer 9c (9.22ꢃ10ꢁ7 M)
upon the addition of bipy (0e500 equiv) recorded in dichloromethane.

E.M. Finnigan et al. / Tetrahedron 67 (2011) 1126e1134
1131
of ligand per porphyrin. The 1:2 complex became the main species
in solution after the addition of 3 equiv of ligand, whereas the 1:3
species was predominant in solution after the addition of almost
60 equiv of bidentate ligand.
2.2.3. Phenylethynyl-linked trimer 10c. In the case of the phenyl-
ethynyl-linked porphyrin trimer 10c (
e
¼958,100 Mꢁ1 cmꢁ1), the
addition of bipy resulted in a decrease in the absorption at 415 nm
while a new band appeared at 422 nm, with an isosbestic point at
419 nm (Fig. 7). With the addition of further equivalents of bipy,
Fig. 8. The species distribution plot of the phenylethynyl-linked trimer 10c
(1.13ꢃ10ꢁ6 M) upon addition of bipy recorded in dichloromethane.
3. Conclusions
2,6,14-Trisubstiuted triptycenylporphyrins were synthesized in
yields up to 36% both via Suzuki and Sonogashira coupling re-
actions. The porphyrin precursors were prepared by nucleophilic
addition reactions of A2-type porphyrins or mixed condensation
reactions and linked to the triptycene core either through the meso
Fig. 7. UV/vis titration spectra (Soret region) of the phenylethynyl-linked trimer 10c
(1.13ꢃ10ꢁ6 M) with bipy recorded in dichloromethane (from 0 to 5000 equiv). Inset:
The binding isotherm with 1:3 trimer/ligand fit, which was determined using SpecfitÔ,
at 425 nm (0e1000 equiv).36
or
b position. The systems investigated provide a proof of concept
for the construction of larger porphyrin arrays based on/with a rigid
triptycene core.
a second isosbestic point was identified at 421 nm (Dl¼6 nm), and
a final absorption with a lmax at 425 (Dl¼10 nm) resulted. This
was comparable to UV/vis investigations carried out with pyri-
dine, where a new absorption at 425 nm (Dl¼10 nm) was ob-
served with a single isosbestic point at 420 nm. This confirmed the
final species in the trimer/bipy solution to be the 1:3 open com-
plex. Using SpecfitÔ the changes in the absorption spectra upon
titration with bipy were assigned to a five-component system
(host; guest; and 1:1; 1:2 and 1:3 trimer/ligand complexes). The
binding isotherm is shown as an inset in Fig. 7.
The binding constants obtained for this fit are shown in Table
3. The binding constant for the formation of the 1:1 complex
was greater than the latter two, indicating the formation of the
more stable sandwich complex. The 6 nm red-shift was attrib-
uted to the formation of a 1:2 trimer/ligand complex, whereas
the overall red-shift of 10 nm relative to the original trimer
absorption was consistent with the formation of the 1:3 open
complex.
Preliminary studies were performed to investigate the host/
guest properties of the triptycene-linked porphyrin trimers.
Complexation experiments with the trimers and bidentate 4,40-
bipyridine were performed and binding constants were de-
termined using SpecfitÔ. Pyridine, a monondentate ligand, was
used for a comparative study. In each array, the binding constants
for the formation of the 1:1 complex were greater by an order of
magnitude with 4,40-bipyridine compared with pyridine. This was
consistent with intramolecular sandwich-type complexation.
Larger binding constants were also obtained for the formation of
the 1:2 trimer/ligand complexes of 9c and 10c with bipy, whereas
5c, displayed a comparable value for both bipy and pyr.
An intermediate species was detected for compounds 5c and
9c and was 6 nm red-shifted from the uncoordinated porphyrin
array. This was assigned to the 1:2 trimer/ligand complex,
which displayed both sandwich and open binding interactions.
At higher concentration of bipy, overall red-shifts of 9/10 nm
was observed. These shifts were comparable to results obtained
with pyridine and were consistent with the formation of a 1:3
trimer/ligand open complex. Compound 8c displayed different
behavior: an intermediate species, with a clear set of isos-
bestic points could not be detected and a red-shift of 6 nm was
observed in the presence of excess ligand. A comparison with
pyridine confirmed that the final species was in fact the 1:3
open complex.
Table 3
The absorption maxima and binding constants for the complexation between 10c
and mono- and bidentate ligands
lmax (nm)
Log K1:1
Log K1:2
Log K1:3
10c
10c bipy
10c pyr
415, 542, 578
425, 557, 595
425, 556, 596
5.1ꢂ0.01
3.5ꢂ0.08
3.7ꢂ0.07
3.3ꢂ0.17
3.9ꢂ0.07
3.5ꢂ0.09
The types of trimers presented herein have not been inve-
stigated previously. They are not fully symmetric and, conse-
quently, both sandwich and open complexation were observed
simultaneously in titrations with bipy. Previous investigations on
the coordination chemistry of multiporphyrin arrays focused either
on fully symmetric systems, whereby sandwich and/or open com-
plexes were observed sequentially,28,29,32a,37 or on dendrimer-type
systems where the intermediate complexes could not be decisively
classified.38
The speciation diagram in Fig. 8 depicted 69% formation of the
1:1 ligand/trimer complex at 11 equiv of bipy per porphyrin. The
1:2 and 1:3 trimer/ligand species were formed simultaneously,
with the former reaching its maximum concentration at 53 equiv of
guest. Both species had similar binding constants and were con-
sistent with external complexation.34

1132
E.M. Finnigan et al. / Tetrahedron 67 (2011) 1126e1134
4. Experimental
140.33, 140.44, 141.25, 141.45, 142.48, 146.44 ppm; UV/vis (CH2Cl2):
lmax (log
e
)¼413 (5.27), 528 (4.21), 569 nm (3.78); HRMS (ESþ)
4.1. General information
[C44H35BN4NiO2]: calcd for [MþH] 721.2285, found 721.2272.
1H NMR spectra were recorded on a Bruker DPX 400 (400 MHz
for 1H NMR and 100.6 for 13C NMR). Chemical shifts are reported in
(ppm) referenced to tetramethylsilane set at 0.00 ppm. HRMS
spectra were measured on Micromass/Waters Corp. USA liquid
chromatography timer-of-flight spectrometer equipped with ES
source. Low resolution mass spectra were recorded on Micromass/
Waters Corp. USA Quattro micro_LCeMS>MS. UV/vis measure-
ments were performed on a PerkineElmer, Lambda 1050 spectro-
photometer or a PerkineElmer, Lambda 25 spectrophotometer.
Melting points were acquired on a Stuart SMP10 melting point
apparatus and are uncorrected. Thin layer chromatography (TLC)
was performed on silica gel 60F254 (Merck) precoated aluminum
sheets. Flash chromatography was carried out using Fluka Silica Gel
60 (230e400 mesh). Anhydrous THF distilled over sodium/benzo-
phenone was used. All commercial chemicals were supplied by
Aldrich and used without purification. UV/vis titrations were per-
formed with a PerkineElmer, Lambda 1050 spectrophotometer or
with a Perkin Elmer, Lambda 25 spectrophotometer. Solutions of
porphyrins were prepared in spectrophotometric grade dichloro-
methane (Aldrich). Analytical data for compounds 2,1 4a,40 5a,41
7a39 9a,21 9b,21 10a,23 and 10b24 agree with those reported in the
literature and related compounds.40
4.2.3. 5-Butyl-15-(40,40,50,50-tetramethyl-[10,30,20]dioxaborolan-20-
yl)-10,20-bis(4-methylphenyl)porphyrin (4b). Prepared by reaction
of 5-bromo-15-butyl-10,20-ditolylporphyrin 4a following the pro-
cedure in Section 4.2.2. The crude product was purified by column
chromatography on silica gel dichloromethane/n-hexane (1:2, v/v)
and gave the pure product as second fraction as purple crystals
after recrystallization from dichloromethane/methanol (207.3 mg,
0.308 mmol) in 48% yield: mp¼260 ꢀC; Rf¼0.37 (dichloromethane/
n-hexane, 1:1, v/v); 1H NMR (400 MHz, CDCl3):
d
¼1.14 (t, 3J¼7.4 Hz,
3H, CH2CH3), 1.84 (s, 14H, CH3þCH2CH3), 2.55 (m, 2H, CH2CH2CH2),
2.76 (s, 6H, tolyleCH3), 5.04 (t, 3J¼7.9 Hz, 2H, CH2CH2CH2CH3), 7.59
(d, 3J¼7.8 Hz, 4H, ArH), 8.10 (d, 3J¼7.8 Hz, 4H, ArH), 8.92 (d,
3J¼4.8 Hz, 2H, Hb), 8.95 (d, 3J¼4.8 Hz, 2H, Hb), 9.49 (d, 3J¼4.8 Hz, 2H,
Hb), 9.82 ppm (d, 3J¼4.8 Hz, 2H, Hb); 13C NMR (100.6 MHz, CDCl3):
d
¼14.24, 21.58, 23.71, 25.33, 35.28, 40.94, 85.06, 119.58, 122.50,
127.29, 134.45, 137.24, 139.67 ppm; UV/vis (CH2Cl2): lmax (log
e)¼
417 (5.35), 517 (4.22), 549 (3.79), 589 (3.77), 644 nm (3.53); HRMS
(ESþ) [C44H45BN4O2]: calcd for [MþH] 673.3714, found 673.3685.
4.2.4. [5-(40,40,50,50-Tetramethyl-{10,30,20}dioxaborolan-20-yl)-
10,15,20-triphenylporphyrinato]zinc(II) (5b). Produced from bro-
moporphyrin 5a following the procedure in Section 4.2.2. The crude
product was purified by column chromatography on silica gel
dichloromethane/n-hexane (1:2, v/v, h¼24 cm, ø¼3 cm) and gave
the pure product as second fraction as purple crystals after re-
crystallization from dichloromethane/methanol, yield: (241.1 mg,
56%): mp¼148 ꢀC; Rf¼0.17 (dichloromethane/n-hexane, 1:1, v/v);
4.2. Syntheses
4.2.1. [5-Bromo-15-(n-butyl)-10,20-bis(4-methylphenyl)porphyr-
inato]zinc(II) (6a). Porphyrin 3a was metalated using Zn(OAc)
according to a procedure by Tomizaki et al.41 to yield a purple solid:
(204.5 mg, 93%): mp >300 ꢀC; Rf¼0.31 (SiO2, dichloromethane/n-
1H NMR (400 MHz, CDCl3):
d
¼1.83 (s, 12H, CH3), 7.72 (m, 9H, ArH),
8.17 (m, 6H, ArH), 8.83 (d, 3J¼4.7 Hz, 2H, Hb) 8.85 (d, 3J¼4.9 Hz, 2H,
hexane, 1:2, v/v); 1H NMR (400 MHz, CDCl3):
d
¼1.15 (t, 3J¼7.3 Hz,
Hb), 8.99 (d, 3J¼4.7 Hz, 2H, Hb), 9.83 (d, 3J¼4.7 Hz, 2H, Hb) ppm; 13
C
CH2CH2CH2CH3), 1.84 (m, 2H, CH2CH2CH2CH3), 2.49 (m, 2H,
CH2CH2CH2CH3), 2.77 (s, 6H, tolyleCH3), 4.82 (t, 3J¼8.0 Hz,
CH2CH2CH2CH3), 7.60 (d, 3J¼7.6 Hz, AreH), 8.05 (d, 3J¼7.8 Hz,
AreH), 8.94 (m, 4H, Hb), 9.41 (d, 3J¼4.7 Hz, 2H, Hb), 9.65 ppm
NMR (100.6 MHz, CDCl3):
d
¼25.02, 84.91, 120.64, 122.30, 126.20,
127.13, 127.19, 131.24, 131.85, 132.56, 132.69, 134.02, 134.17, 142.44,
142.55, 149.02, 149.69, 150.09, 154.10 ppm; UV/vis (CH2Cl2): lmax
(log
e
)¼417 (5.13), 546 (4.27), 581 nm (3.57); HRMS (ESþ)
(d,3J¼4.7 Hz, 2H, Hb); 13C NMR (150.9 MHz, CDCl3):
d
¼14.2, 21.6,
[C44H35BN4O2Zn] calcd for [MþH] 727.2223, found 727.2206.
23.7, 35.4, 41.1, 103.5, 121.1, 122.2, 127.3, 129.0, 132.4, 132.5, 133.1,
134.4, 137.2, 139.6, 149.6, 149.6, 150.0, 150.3 ppm; UV/vis (CH2Cl2):
4.2.5. [5-Butyl-15-(40,40,50,50-tetramethyl-[10,30,20]dioxaborolan-20-
yl)-10,20-bis(4-methylphenyl)porphyrinato]zinc(II) (6b). The re-
action followed the procedure given in Section 4.2.2. However,
prior to purification metalation with zinc(II) acetate was performed
on the crude product. Filtration through a frit using silica gel and
dichloromethane/n-hexane (1/1, v/v) eluted the debrominated
porphyrin side product. Changing the eluent to dichloromethane
yielded the title compound 6b as a purple solid (390.4 mg, 80% for
two steps): mp >300 ꢀC; Rf¼0.51 (dichloromethane/n-hexane, 1:1,
lmax (log
e
)¼423 (5.6), 554 (4.5), 592 nm (4.3); HRMS (ESþ)
[C38H31N4BrZn] calcd for [MþH] 686.1024, found 686.1013.
4.2.2. [5-(40,40,50,50-Tetramethyl-{10,30,20}dioxaborolan-20-yl)-
10,15,20-triphenylporphyrinato]nickel(II) (3b). The bromoporphyrin
3a (1 equiv) was placed in a Schlenk tube and dried under vacuum.
Dry 1,2-dichloroethane (20 ml) and dry triethylamine (13 equiv)
were added under argon. The solution was degassed via three
freeze-pump-thaw cycles, before the vessel was purged with argon.
4,4,5,5-Tetramethyl-1,3,2-dioxaborolane (10 equiv) and dichlorobis
(triphenylphosphine)palladium(II) (0.03 equiv) were then added,
and the Schlenk tube was sealed and stirred at 90 ꢀC overnight. The
reaction was quenched carefully with a saturated KCl solution,
washed with water, and dried over Na2SO4. The solvent was
removed under reduced pressure. The crude product was purified
by column chromatography on silica gel dichloromethane/n-hex-
ane (1:2, v/v, h¼31 cm, ø¼6 cm) and gave the pure product as
second fraction as purple crystals after recrystallization from
dichloromethane/methanol, yield: 201.5 mg (0.28 mmol, 51%):
mp¼230 ꢀC; Rf¼0.53 (dichloromethane/n-hexane, 1:1, v/v); 1H
v/v); 1H NMR (400 MHz, CDCl3):
d
¼1.17 (t, 3J¼7.4 Hz, 3H,
CH2CH2CH2CH3), 1.90 (m, 14H, CH3, CH2CH2CH2CH3), 2.54 (m, 2H,
CH2CH2CH2CH3), 2.79 (s, 6H, tolyleCH3), 4.92 (m, 2H,
CH2CH2CH2CH3), 7.62 (d, 3J¼7.2 Hz, 4H, AreH), 8.13 (d, 3J¼7.3 Hz,
4H, AreH), 9.05 (m, 4H, Hb), 9.50 (m, 2H, Hb), 9.91 ppm (m, 2H, Hb);
13C NMR (150.9 MHz, CDCl3):
85.1, 120.4, 123.2, 127.7, 128.9, 131.8, 132.9, 134.4, 137.0, 140.1, 149.2,
d
¼14.2, 21.5, 23.8, 25.3, 35.6, 41.2,
149.7, 150.0, 154.6 ppm; UV/vis (CH2Cl2): lmax (log
e
)¼419 (5.7), 548
(4.5), 585 nm (4.1); HRMS(ESþ) [C44H43N4O2Zn] calcd for [MþH]
734.2771, found 734.2749.
4.2.6. 5-(40,40,50,50-Tetramethyl-[10,30,20]dioxaborolan-20-yl)-
10,15,20-triphenylporphyrin (7b). 5-Bromo-10,15,20-triphenylpor-
phyrin 7a (400 mg, 0.65 mmol), triethylamine (1.17 mL, 8.42 mmol),
borolane (0.94 mL, 6.48 mmol), and dichlorobis(triphenylphos-
phine)palladium(II) (13.6 mg, 0.02 mmol) were reacted according to
4.2.2. Column chromatography using dichloromethane as eluent
NMR (400 MHz, CDCl3):
d
¼1.72 ppm (s. 12H, CH3), 7.71 (m, 9H,
AreH), 8.02 (m, 6H, AreH), 8.70 (d, 2H, 3J¼4.9 Hz, Hb), 8.74 (d, 2H,
3J¼4.9 Hz, Hb), 8.86 (d, 2H, 3J¼5.1 Hz, Hb), 9.79 ppm (d, 2H,
3J¼5.1 Hz, Hb); 13C NMR (100.6 MHz, CDCl3):
¼24.73, 84.39, 118.25,
d
126.38, 127.23, 127.29, 131.12, 131.86, 132.61, 133.18, 133.26, 133.54,

E.M. Finnigan et al. / Tetrahedron 67 (2011) 1126e1134
1133
yielded a purple solid (241.1 mg, 56%): mp >300 ꢀC; Rf¼0.2 (SiO2,
dichloromethane/n-hexane 1:2, v/v); 1H NMR (600 MHz, CDCl3):
2:1, v/v); 1H NMR (600 MHz, CDCl3):
d
¼6.16 (s, 1H, CH), 6.31 (s, 1H,
CH), 7.82 (m, 27H, AreH), 8.01 (d, 3J¼7.1 Hz, 1H, AreH), 8.13 (d,
3J¼7.3 Hz, 1H, AreH), 8.17 (m, 1H, AreH), 8.30 (m, 20H, AreH), 8.52
(s, 1H, AreH), 8.61 (s, 1H, AreH), 8.70 (s, 1H, AreH), 8.99e9.11 (m,
d
¼ꢁ2.75 (s, 2H, NH), 1.87 (s, 12H, CH3), 7.78 (m, 9H, AreH), 8.24 (m,
6H, AreH), 8.85 (dd, 3J¼4.4, 14.2 Hz, 4H, Hb), 9.00 (d, 3J¼4.6 Hz, 2H,
Hb), 9.89 ppm (d, 3J¼4.6 Hz, 2H, Hb); 13C NMR (150.9 MHz, CDCl3)
18H,
¼56.2, 120.7, 122.4, 126.6, 127.5, 130.6, 132.0, 132.1, 132.4,
bH), 9.22 ppm (m, 6H, b
H); 13C NMR (150.9 MHz, CDCl3):
d
¼23.3, 85.2, 120.0, 121.8, 126.6, 127.7, 134.5, 142.0, 142.4 ppm; UV/
d
vis (CH2Cl2): lmax (log
e
)¼417 (5.4), 514 (4.3), 546 (4.0), 588 (4.0),
134.5 ppm; UV/vis (CH2Cl2): lmax (log
e
)¼424 (5.9), 548 (4.6),
649 nm (3.9); HRMS(ESþ) [C44H38N4] calcd for [MþH] 665.3088,
587 nm (4.0); HRMS (MALDI LDþ) [C134H80N12Zn3þH]: calcd
found 665.3109.
2048.4503, found 2048.4529.
4.2.7. 2,6,14-[Tris(5,10,15-triphenylporphyrin-20-ylato)nickel(II)]
triptycene (7c). The borolanylporphyrin 3b (1 equiv), 2,6,14-triio-
dotriptycene 2 (0.3 equiv), potassium phosphate (4 equiv) and
tetrakis(triphenylphosphine)palladium(0) (0.1 equiv) were placed
in a Schlenk tube and dissolved in anhydrous DMF under argon. The
mixture was heated at 100 ꢀC for 12 h. The solvent was removed
and the residue was redissolved in dichloromethane and washed
with aqueous sodium hydrogen carbonate solution. The crude
product was purified by dry-loaded column chromatography on
silica gel, dichloromethane/n-hexane (1:2, v/v, h¼53 cm, ø¼3 cm)
and gave the pure product as second fraction as orange crystals
after recrystallization from dichloromethane/methanol (20.6 mg,
0.01 mmol, 22%). Alternatively, this compound was prepared by
Suzuki coupling of the free-base porphyrin 7b directly followed in
situ by metalation with zinc(II)acetate and standard work up: mp
>310 ꢀC; Rf¼0.47 (dichloromethane/n-hexane, 1:1, v/v); 1H NMR
4.2.10. 2,6,14-[Tris(5-n-butyl-10,20-bis(4-methylphenyl)porphyrin-15-
ylato)zinc(II)]triptycene (6c). [5-n-Butyl-15-(40,40,50,50-tetramethyl-
[10,30,20]dioxa-borolan-20-yl)-10,20-bis(4-methylphenyl)porphy-
rinato]zinc(II) 6a (200 mg, 0.27 mmol), 2,6,14-triiodotriptycene 2
(51.5 mg, 0.08 mmol), and potassium phosphate (230.7 mg,
1.10 mmol) were added to a 100 mL Schlenk flask and dried under
vacuum. The vacuum was released to allow the addition of dry
dimethylformamide (25 mL). The mixture was degassed via three
freeze-pump-thawcyclesbeforethevesselwaspurgedwithargonand
tetrakis(triphenylphosphine)palladium(0) (31.4 mg, 0.03 mmol) was
added. The Schlenk flask was sealed and heated to 100 ꢀC overnight
(TLC control; dichloromethane/n-hexane 1:1, v/v). Then, the solvent
was removed and the residue was redissolved in dichloromethane and
washed with aqueous sodium hydrogen carbonate. The crude por-
phyrin mixture was dried in vacuo and subjected to purification via
column chromatography on silica gel using dichloromethane/n-hex-
ane (2:1, v/v) as eluent ti yield the title compound (22 mg, 22%); mp
>300 ꢀC; Rf¼0.41 (SiO2, dichloromethane/n-hexane 1:2, v/v); 1H NMR
(400 MHz, CDCl3):
d¼5.96 ppm (s, 1H, CH), 6.10 (s, 1H, CH), 7.71 (m,
30H, ArH), 8.05 (m, 21H, ArH), 8.18 (s, 1H, ArH), 8.25 (s, 1H, ArH), 8.33
(s, 1H, ArH), 8.78 (m, 16H, Hb), 8.92 ppm (m, 8H, Hb); 13C NMR
(400 MHz, CDCl3):
d
¼1.18 (t, 3J¼7.3 Hz, 9H, CH2CH2CH2CH3), 1.90 (m,
(150.9 MHz):
d
¼53.97, 54.01, 118.83, 118.84, 118.87, 118.91, 118.96,
6H CH2CH2CH2CH3), 2.60 (m, 6H, CH2CH2CH2CH3), 2.77 (s, 6H, tol-
yleCH3), 2.79 (s,12H, tolyleCH3), 5.04 (m, 6H, CH2CH2CH2CH3), 6.10 (s,
1H, ArH), 6.26 (s,1H, ArH), 7.62 (m,12H, ArH), 7.97 (d, 3J¼7.3 Hz, 1H, ArH),
8.14 (m, 18H, ArH), 8.54 (s,1H, ArH), 8.63 (s, 1H, ArH), 9.07 (m, 18H, Hb),
122.43, 126.69, 126.71, 127.56, 129.43, 131.16, 132.02, 132.06, 132.29,
132.36. 132.42, 133.57, 138.02, 140.80 ppm; UV/vis (CH2Cl2): lmax
(log
e
)¼418 (5.54), 528 nm(5.06); HRMS (LDþ) [C134H80N12Ni3]
calcd 2030.4689, found 2030.4669.
9.58 ppm (m, 6H, Hb); 13C NMR (150.9 MHz, CDCl3):
35.4, 41.0, 46.2, 54.3, 120.5,122.2, 127.2,128.6, 130.4,130.7, 131.7, 132.1,
d
¼13.9, 21.4, 23.6,
4.2.8. 2,6,14-Tris[5-n-butyl-10,15-bis(4-methylphenyl)porphyrin-20-
yl]triptycene (4c). Produced from the borolanylporphyrin 4b fol-
lowing procedure given in 4.2.7. The crude product was purified by
column chromatography on silica gel dichloromethane/n-hexane
(1:1, v/v, h¼31 cm, ø¼3 cm) and gave the pure product as the sixth
fraction as purple crystals after recrystallization from dichloro-
methane/methanol (8.9 mg, 0.005 mmol, 16%): mp¼237 ꢀC;
Rf¼0.13 (CH2Cl2/n-hexane, 1:1, v/v); 1H NMR (600 MHz, CDCl3,
132.3, 134.2, 136.9, 139.9, 149.9, 150.4 ppm; UV/vis (CH2Cl2): lmax
(log
e
)¼424 (6.0), 552 (4.8), 593 nm (4.6); HRMS (MALDI LDþ)
[C134H104N12Zn3]: calcd for [MþH] 2072.6381, found 2072.6462.
4.2.11. 2,6,14-Tri[(5-ethynyl-10,15,20-tris(4-methylphenyl)porphyr-
inato)zinc(II)]triptycene (8). Under a nitrogen atmosphere 2,6,14-
triiodotriptycene 2 (40.0 mg, 63.3
borolan-20-yl)-5,10,15,20-tetraphenylporphyrin (281 mg, 380
6 equiv), and Ba(OH)2$8H2O (200 mg, 663 mol) were dissolved in
toluene/H2O (20 mL/4 mL) und the resulting mixture was degassed by
a nitrogen stream for 20 min. Pd(PPh3)4 (14.6 mg,12.7 mol, 20 mol %)
m
mol, 1 equiv), 2-([10,30,20]-dioxa-
mmol,
20 ꢀC, TMS):
d
¼ꢁ2.64 ppm (s, 2H, NH), -2.61 (s, 2H, NH), ꢁ2.57 (s,
m
2H, NH), 1.16 (t, 12H, 3J¼7.3 Hz, CH3), 1.85 (m, 6H, CH2CH3), 2.57 (m,
6H, CH2CH2CH2), 2.77 (m, 18H, C6H5eCH3), 5.06 (m, 6H,
CH2CH2CH2CH3), 6.13 (s, 1H, CH), 6.26 (s, 1H, CH), 7.61 (m, 12H, ArH),
8.14 (m, 18H, ArH), 8.48 (s, 1H, ArH), 8.53 (s, 1H, ArH), 8.60 (s, 1H,
m
was added and the mixture was heated to reflux for 18 h. The crude
mixture was filtered through a plug of silica eluting with CH2Cl2 and
EtOAc. The filtrate was washed with a saturated solution of NH4Cl and
H2O and the solvent was removed in vacuo. Column chromatography
on silica gel (CH2Cl2/n-hexane, 1:1/3:2/2:1/1:0, v/v) yielded 8 as
ArH), 8.91 (m, 5H, Hb), 8.99 (m, 13H, Hb), 9.51 ppm (m, 6H, Hb); 13
C
NMR (150.9 MHz, CDCl3):
d
¼13.97, 14.06, 21.41, 22.54, 23.51, 29.21,
29.56, 31.79, 35.11, 40.75, 54.17, 119.25, 119.46, 116.53, 120.29,
122.34, 127.19, 128.69, 130.47, 130.75, 132.04, 134.33, 137.05, 137.08,
137.15, 139.30, 139.43, 144.11, 144.87 ppm; UV/vis (CH2Cl2): lmax
a purple microcrystalline solid (12.8 mg, 6.12
m
mol,10%): mp >300 ꢀC;
¼3301 (w), 3052 (m), 3021
Rf¼0.26 (CH2Cl2/n-hexane, 2:1); IR (ATR):
n
(log
e
)¼422 (5.40), 446 (5.01), 518 (4.44), 554 (4.25), 593 (4.04),
(m), 2923 (w), 1596 (m), 1574 (w), 1560 (w), 1468 (m), 1439 (s), 1405
(w), 1348 (m), 1261 (w), 1216 (w), 1177 (m), 1155 (w), 1071 (m), 1032
(w),1001 (m), 986 (m), 964 (s), 929 (w), 878 (w), 842 (w), 828 (w), 796
649 nm (4.05); HRMS (ESþ) [C134H110N12]: calcd for [Mþ2H]
1888.9133, found 1888.9158.
(s), 723 cmꢁ1 (s); 1H NMR (400 MHz, CDCl3):
d
¼ꢁ2.64 to ꢁ2.49 (m, 6H,
4.2.9. 2,6,14-[Tris(5,10,15-triphenylporphyrin-20-ylato)zinc(II)]trip-
NH), 5.04 (s, 1H, triptyceneH), 5.21 (s, 1H, triptyceneH), 6.29e6.48 (m,
3H, ArH), 6.64e6.88 (m, 6H, ArH), 7.16e7.25 (m, 4H, ArH), 7.27e7.43 (m,
5H, ArH), 7.66e7.90 (m, 33H, ArH), 8.15e8.41 (m, 18H, ArH),
tycene
(5c). [5-(40,40,50,50-Tetramethyl-[10,30,2]-dioxaborolan-20-
yl)-10,15,20-triphenylporphyrin]zinc 5b (200 mg, 0.27 mmol),
2,6,14-triiodotriptycene 2 (52.1 mg, 0.08 mmol), potassium phos-
phate (233.3 mg, 1.10 mmol), and tetrakis(triphenylphosphine)pal-
ladium(0) (31.6 mg, 0.03 mmol) were reacted as described for
Section 4.2.7. Column chromatography on silica gel using dichloro-
methane/n-hexane (1:1, v/v) as eluent yielded the title compound
(44.4 mg, 27%): mp >310 ꢀC; Rf¼0.09 (dichloromethane/n-hexane,
8.64e8.97 ppm (m, 21H, Hb); 13C NMR (150.9 MHz, CDCl3):
d¼53.4,
53.5, 119.6, 119.7, 119.8, 119.9, 120.3, 120.4, 121.6, 122.2, 122.5, 122.8,
122.9, 125.7, 125.8, 126.5, 126.6, 126.7, 127.1, 127.2, 127.7, 127.8, 128.7,
128.8, 130.8, 130.9, 131.9, 132.1, 132.3, 132.4, 132.7, 133.6, 133.8, 134.4,
134.5, 134.6, 135.3, 135.4, 135.5, 136.3, 139.7, 139.8, 139.9, 134.0, 141.8,
141.9, 142.2, 142.3, 142.5, 143.7, 144.9 ppm; UV/vis (CH2Cl2): lmax

1134
E.M. Finnigan et al. / Tetrahedron 67 (2011) 1126e1134
(log
e
)¼424 (5.44), 519 (4.46), 554 (4.25), 594 (4.08), 650 nm (4.07);
B2650). We are grateful to Rebecca Duke and Prof. Thorri Gunn-
laugsson for assistance with the Specfit analysis.
HRMS (MALDI LDþ) [C152H99N12]: calcd for [MþH] 2091.8116, found
2091.8079. HRMS (ESI, positive) C152H99N12: calcd for [MþH]þ
2091.8110, found 2091.8085.
References and notes
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4.2.12. 2,6,14-Tri[(5-ethynyl-10,15,20-tris(4-methylphenyl)porphyr-
inato)zinc(II)]triptycene
phenyl)porphyrinato]zinc(II) 9b (100 mg, 0.15 mmol) 2,6,14-
triiodotriptycene (31.5 mg, 0.05 mmol), and triphenylarsine
(9c). [5-Ethynyl-10,15,20-tris(4-methyl-
2
6. Han, T.; Chen, C.-F. Org. Lett. 2006, 8, 1069e1072.
(91.7 mg, 0.3 mmol) were added to a 100 mL Schlenk flask and dried
under vacuum. The vacuum was released to allow for the addition of
dry THF (10 mL) and dry triethylamine (5 mL). The mixture was
degassed via three freeze-pump-thaw cycles before the vessel was
purged with argon and tris(dibenzylideneacetone)dipalladium(0)
(27.4 mg, 0.03 mmol) was added. The Schlenk tube was sealed and
the reaction mixture stirred overnight at 30 ꢀC. Then, dichloro-
methane (60 mL) was added, the mixture was washed with water
(2ꢃ30 mL) and dried over sodium hydrogen carbonate. The solvent
was evaporated under reduced pressure and the product purified by
column chromatography on silica gel. The crude product was sub-
jected to column chromatography on silica gel using dichloro-
methane/n-hexane (1:1, v/v) as eluent toyield the title compound 5c
(31 mg, 28%): mp >300 ꢀC; Rf¼0.61 (SiO2, dichloromethane/n-hex-
7. Osuka, A.; Liu, B. L.; Maruyama, K. J. Org. Chem. 1993, 58, 3582e3585.
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€
Photobiol. 1999, 70, 206e216; (c) Wiehe, A.; Senge, M. O.; Schafer, A.; Speck, M.;
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Tannert, S.; Kurreck, H.; Roder, B. Tetrahedron 2001, 57, 10089e10110.
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ane 3:1, v/v); 1HNMR (600 MHz, CDCl3):
d¼2.75(m, 27H, tolyleCH3),
5.93(s,1H, ArH), 6.00(s,1H, ArH), 7.59 (m, 24H, ArH), 7.83(m, 6H, ArH),
8.11 (m, 24H, ArH), 8.29 (s,1H, ArH), 8.32 (s,1H, ArH), 8.35 (s,1H, ArH),
8.91 (m, 12H, Hb), 9.06 (m, 6H, Hb), 9.86 ppm (m, 6H, Hb); 13C NMR
17. (a) Deng, Y. Q.; Chang, C. K.; Nocera, D. G. Angew. Chem., Int. Ed. 2000, 39,
€
€
1066e1067; (b) Senge, M. O.; Rossler, B.; von Gersdorff, J.; Schafer, A.; Kurreck,
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18. (a) Bringmann, G.; Rudenauer, S.; Gotz, D. C. G.; Gulder, T. A. M.; Reichert, M.
(150.9 MHz, CDCl3):
d
¼21.4 (CH3), 53.9 (AreC), 121.4 (qC), 124.2
€
€
(AreC), 127.2 (qC), 127.2 (AreC), 128.7 (AreC), 129.2 (AreC), 130.6
(AreC), 131.7 (AreC), 132.8 (AreC), 134.1 (AreC), 134.2 (qC), 137.1
(qC), 139.4 (qC), 144.9 (qC), 149.8 ppm (qC); UV/vis (CH2Cl2): lmax
€
Org. Lett. 2006, 8, 4743e4746; (b) Bringmann, G.; Gotz, D. C. G.; Gulder, T. A. M.;
Gehrke, T. H.; Bruhn, T.; Kupfer, T.; Radacki, K.; Braunschweig, H.; Heckmann,
A.; Lambert, C. J. Am. Chem. Soc. 2008, 130, 17812e17825; (c) Gotz, D. C. G.;
€
Bruhn, T.; Senge, M. O.; Bringmann, G. J. Org. Chem. 2009, 74, 8005e8020.
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(log
e
)¼443 (6.0), 527 (4.2), 566 (4.7), 614 nm (4.9); HRMS (MALDI
LDþ) [C149H98N12Zn3]: calcd for [MþH] 2246.5912, found 2246.5916.
4.2.13. 2,6,14-Tri[(5,15-bis(4-methylphenyl)-10-(4-phenylethynyl)
porphyrinato)zinc(II)]triptycene (10c). [5,15-Bis(4-methylphenyl)-
10-phenylethynylporphyrinato]zinc(II) 10b (100 mg, 0.15 mmol)
2,6,14-triiodotriptycene 2 (32.2 mg, 0.05 mmol), triphenylarsine
(93.6 mg, 0.3 mmol), and tris(dibenzylideneacetone)dipalladium(0)
(28.0 mg, 0.03 mmol) werereacted according tothe proceduregiven
in Section 4.2.12. The crude product was subjected to column
chromatography on silica gel using dichloromethane/n-hexane (1:1,
v/v) as eluent to yield the title compound (39.6 mg, 36%): mp
>300 ꢀC; Rf¼0.49 (SiO2, dichloromethane/n-hexane 1:1, v/v); 1H
30. Connors, K. A. p. In Binding Constants, the Measurement of Molecular Complex
Stability; John Wiley: New York, NY, 1987; 141e187.
31. (a) Gampp, H.; Maeder, M.; Meyer, C. J.; Zuberbuhler, A. D. Talanta 1986, 33,
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32. (a) Ballester, P.; Costa, A.; Castilla, A. M.; Deya, P. M.; Frontera, A.; Gomila, R. M.;
NMR (600 MHz, CDCl3):
d¼2.77 (m,18H, tolyleCH3), 5.66 (s,1H, ArH),
€
5.68 (s, 1H, ArH), 7.49 (d, 3J¼6.9 Hz, 3H, ArH), 7.62 (m, 12H, ArH), 7.74
(m, 3H, ArH), 7.87 (m, 3H, ArH), 7.96 (d, 3J¼7.9 Hz, 6H, ArH), 8.15 (m,
12H, ArH), 8.24 (d, 3J¼7.9 Hz, 6H, ArH), 9.04 (m,12H, Hb), 9.13 (m, 6H,
Hb), 9.37 (m, 6H, Hb),10.20 ppm (m 3H, Hmeso); 13C NMR (150.9 MHz,
ꢁ
Hunter, C. A. Chem.dEur. J. 2005, 11, 2196e2206; (b) Tabushi, I.; Kugimiya, S.;
Kinnaird, M. G.; Sasaki, T. J. Am. Chem. Soc. 1985, 107, 4192e4199; (c) Flamigni,
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Commun. 2001, 733e734.
ꢀ
CDCl3):
d
¼21.4, 53.7, 106.0, 124.7, 125.2, 127.2. 128.2, 128.8, 129.6,
130.3, 131.6, 132.0, 132.6, 134.3, 137.0, 143.2 ppm; UV/vis (CH2Cl2):
lmax (log
[C146H92N12Zn3]: calcd for [MþH] 2204.5442, found 2204.5479.
33. Anderson, H. L.; Hunter, C. A.; Meah, M. N.; Sanders, J. K. M. J. Am. Chem. Soc.
1990, 112, 5780e5789.
34. Flamigni, L.; Talarico, A. M.; Ventura, B.; Sooambar, C.; Solladie, N. Eur. J. Inorg.
e
)¼415 (6.0), 542 (4.6), 581 nm (3.5); HRMS (MALDI LDþ)
ꢀ
Chem. 2006, 2155e2165.
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Trans. 1 1988, 1735e1738.
4.3. Determination of binding constants
ꢀ
37. Rein, R.; Gross, M.; Solladie, N. Chem. Commun. 2004, 1992e1993.
Binding constants were determined by using the non-linear
least-squares program SPECFIT/32Ô, which is a multivariate data
analysis program for modeling and fitting experimental data sets
(such as chemical kinetics and equilibrium titrations) obtained
from multivariate spectrophotometric measurements.
ꢀ
38. Flamigni, L.; Talarico, A. M.; Ventura, B.; Rein, R.; Solladie, N. Chem.dEur. J.
2006, 12, 701e712.
39. Hartnell, R. D.; Edwards, A. J.; Arnold, D. P. J. Porphyrins Phthalocyanines 2002, 6,
695e707.
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Scientific Publishing Company: Amsterdam, 1975; pp 157e232; (b) DiMagno,
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J. Chem. Soc., Perkin Trans. 1 2001, 1030e1038.
Acknowledgements
This work was generously supported by grants from Science
Foundation Ireland (SFI 07/RFP/CHEF232 and SFI P.I. 09/IN.1/
41. Tomizaki, K.-y.; Lysenko, A. B.; Taniguchi, M.; Lindsey, J. S. Tetrahedron 2004, 60,
2011e2023.