Synthesis, structure, and spectroscopy of phenylacetylenylene rods incorporating meso-substituted dipyrrin ligands

Article abstract of DOI:10.1002/chem.200305041

The synthesis, structure, and spectroscopic characterization of a series of phenylacetylenylene rodlike molecules containing dipyrromethene (dipyrrin) ligands are described. The combination of the phenylacetylenylene groups with the porphyrinogenic dipyrr

Full text of DOI:10.1002/chem.200305041

FULL PAPER
Synthesis, Structure, and Spectroscopy of Phenylacetylenylene Rods
Incorporating meso-Substituted Dipyrrin Ligands
Sara R. Halper and Seth M. Cohen*[a]
Abstract: The synthesis, structure, and
spectroscopic characterization of a ser-
ies of phenylacetylenylene rodlike mol-
ecules containing dipyrromethene (di-
pyrrin) ligands are described. The com-
bination of the phenylacetylenylene
groups with the porphyrinogenic dipyr-
rin moieties results in a rich absorption
spectroscopy for these compounds, al-
though the fluorescence of the phenyl-
acetylenylene moiety is quenched by
presence of the dipyrrin chelator. The
Cu2‡ and Fe3‡ complexes of these li-
gands have been prepared and three of
these compounds have been structurally
characterized by using single-crystal
X-ray diffraction. Unlike other octahe-
dral metal-dipyrrin complexes described
to date, one of the iron complexes
demonstrates ideal threefold symmetry
in the solid-state. The elongated struc-
ture and high symmetry of these com-
plexes suggests the use of these meso-
substituted phenylacetylenylene ligands
as an interesting class of extended,
branched molecules for the construction
of supramolecular architectures.
Keywords: copper ¥ iron ¥ ligand
design ¥ N ligands ¥ supramolecular
chemistry
ing relative ease of synthesis, intense optical absorptions, and
a propensity to form stable, neutral complexes with a variety
of metal ions. Previous efforts have taken advantage of these
properties by synthesizing both simple coordination com-
pounds and supramolecular clusters that are easily purified by
conventional silica flash chromatography.[21, 22] Earlier studies
by Dolphin and co-workers utilized a- and b- linked dipyrrins
for the synthesis of metallohelicates and metal-containing
cyclic trimers.[21, 22] These multinuclear complexes clearly
demonstrate the advantages of dipyrrin ligands as described
above, but the complexes described to date have been limited
to only a few different supramolecular topologies.[23, 24] In
contrast, the use of meso-substituted dipyrrins has the
advantage of allowing for the rational design of directional
bonding[24, 25] and exploration of new molecular architectures
with these intriguing ligand systems.
In an effort to exploit the phenylacetylenylene building
block motif and provide new compounds for the synthesis of
supramolecular structures, we have prepared a series of meso-
substituted dipyrrin ligands fused with a variety of phenyl-
acetylenylene backbones. The cupric and ferric metal com-
plexes of these ligands have been synthesized, and the
spectroscopic properties of these compounds have been
examined. The compounds prepared show that metal ions
can be used to spatially organize phenylacetylenylene units in
a defined stoichiometry. The highly symmetric architecture of
these complexes makes them excellent candidates for incor-
poration of transition-metal centers into many of the supra-
molecular systems where phenylacetylenylene-derived com-
pounds have found utility.
Introduction
Rigid phenylacetylenylene building blocks have gathered
considerable attention for use in a variety of supramolecular
systems. Macrocyclic phenylacetylenylenes have been used to
prepare a number of liquid-crystalline materials,[1, 2] and
heteroatom-substituted systems have been synthesized to
generate several novel metal-binding macrocycles.[3]
Branched phenylacetylenylene-based molecules have been
described in the construction of light-harvesting dendrim-
ers[4 and decorating the surface of metal-cluster-based
dendrimers.[7] Smaller branched systems have been derivat-
ized with peripheral metal-binding groups to construct
6]
molecular solids[8
and even to link together metal nano-
10]
particles.[11, 12] These conjugated molecules have also been
tethered to surfaces for study as 'molecular-scale wires'[13] and
surface-immobilized catalysts.[14, 15] Clearly, these investiga-
tions show that the phenylacetylenylene unit has found
widespread incorporation into various supramolecular sys-
tems.
Dipyrromethene (dipyrrin) ligands are aromatic, planar
ligand systems that are porphyrinogenic in nature.[16
dipyrrin ligand offers a number of desirable features for
utilization in supramolecular coordination chemistry includ-
20]
The
[a] Prof. S. M. Cohen, S. R. Halper
Department of Chemistry and Biochemistry
University of California, San Diego, La Jolla, CA 92093-0358 (USA)
Fax: (‡1)858-822-5598
E-mail: scohen@ucsd.edu
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DOI: 10.1002/chem.200305041
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S. M. Cohen and S. R. Halper
FULL PAPER
shows the synthesis of a meta-substituted dipyrrin phenyl-
acetylenylene ligand (L2) that was also synthesized via a
phenylacetylenylene-substituted aldehyde prior to formation
of the dipyrrin. Scheme 3 shows the synthesis of two
'extended' ligands (L3, L4) that contain an additional phenyl-
acetylenylene unit relative to L1 and L2. The synthesis of these
extended ligands proceeds via an iodoarylaldehyde inter-
mediate that is ultimately converted to the dipyrrin ligand at
the end of the synthesis in a manner analogous to ligands L1
and L2 described above. All of the final dipyrrin ligands can be
isolated as yellow, glassy solids, however isolation of the
dipyrrins was not required for the synthesis of the desired
metal complexes. Indeed, synthesis of the metal complexes
was found to be more facile when prepared by a one-pot
Results and Discussion
Ligand synthesis: Three different approaches were envisaged
for the preparation of dipyrrin phenylacetylenylene ligands.
These three synthetic strategies are outlined in Scheme 1.
Method 1 begins first with the preparation of an arylhalide-
substituted dipyrrin that can be subsequently coupled to
phenylacetylenylene. Method 1 was abandoned due to the
difficulty involved in purifying the dipyrrin products via
column chromatography (vide infra). Method 2 involved the
preparation of an arylhalide-substituted dipyrromethane,
followed by Sonogashira coupling[26] to phenylacetylenylene,
and finally oxidation to the dipyrrin ligand.[17, 18] Although a
plausible route based on the large amounts of dipyrromethane
that could be prepared (despite the modest yield), repeated
attempts of the Sonogashira coupling were unsuccessful,
presumably due to an incompatibility with the dipyrrome-
thane moiety. Finally, method 3 was applied, which involves
the synthesis of a phenylacetylenylene-extended aldehyde
followed by subsequent preparation of the dipyrromethane
and the dipyrrin, respectively. Method 3 was found to be the
most efficient route to L1 and was subsequently applied to all
of the ligands described herein. This route provided good
yields for all of the intermediates, although the isolated yields
of the dipyrrin products remained relatively low. Scheme 2
18]
reaction starting with the dipyrromethane precursors.[16
Synthesis of metal complexes: Copper(ii) and iron(iii) com-
plexes of ligands L1 L4 were synthesized from solutions of
the ligand prepared in situ. This approach was used, as
purification of the free dipyrrin ligands was rather tedious,
while isolation of the metal complexes was found to be facile.
In addition, the free dipyrrin ligand could be isolated later by
demetalation methods (vide infra).[27, 28] In a typical reaction
(Scheme 4), the dipyrromethane precursor (2, 4, 8, 11) was
oxidized in ice cold CHCl3 by the addition of a benzene
Scheme 1. Three synthetic routes investigated for the synthesis of dipyrrin L1. TF Aˆ trifluoroacetic acid, DDQ ˆ 2,3-dichloro-5,6-dicyanobenzoquinone,
TEA ˆ triethylamine.
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Phenylacetylene Rods with meso-Substituted Dipyrrin Ligands
4661 4669
Scheme 2. Synthetic route for ligand L2.
Scheme 3. Synthetic route for ligands L3 and L4.
complexes were easily purified by flash silica chromatography,
where the compounds were followed as bright red bands on
the column. Subsequent isolation of the free ligands could be
obtained by treating the purified copper complexes
([Cu(LN)2]) with excess KCN in a ꢀ3:1 THF/water solution.
Subsequent removal of solvent and re-dissolution of the
resulting residue in CH2Cl2 was followed by several aqueous
washes resulting in isolation of the metal-free ligands (L1
L4). A notable difference was found in the solubility of
complexes prepared with the 'linear' ligands (L1, L3) versus
the 'bent' ligand systems (L2, L4). The complexes [Cu(L2)2],
[Fe(L2)3], [Cu(L4)2], and [Fe(L4)3] were soluble in most
organic solvents including acetone, MeOH, EtOH, CH2Cl2,
CHCl3, benzene, pentane, hexanes, and diethylether. How-
ever, the linear ligand complexes [Cu(L1)2], [Fe(L1)3],
[Cu(L3)2], and [Fe(L3)3] were generally only soluble in
CH2Cl2, CHCl3, and benzene. Notably, the complex
[Cu(L3)2] after being purified by column chromatography,
using CHCl3 as solvent, became difficult to redissolve in all
solvents, including the aforementioned CH2Cl2, CHCl3, and
benzene. The reason for the low solubility of the 'linear' ligand
Scheme 4. Synthesis of metal complexes from ligands L1 L4.
solution containing an equimolar amount of 2,3-dichloro-5,6-
dicyanobenzoquinone (DDQ). After the addition was com-
plete, partial removal of solvent, followed by addition of the
metal salt resulted in formation of the desired complexes as
judged by thin-layer chromatography. All of the metal
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S. M. Cohen and S. R. Halper
FULL PAPER
complexes is unclear, but may be related to interligand
stacking and subsequent aggregation.
of the dipyrrin chelating groups, as is typically found for meso-
substituted dipyrrins with aryl substituents in this posi-
18]
tion.[16 The angle between the planes of the two aromatic
systems is 598 in one ligand and 558 in the other. The
phenylacetylenylene groups are essentially linear for both
ligands attached to the copper center.
The iron complex [Fe(L1)3] crystallized as small hexagons,
suggestive of a high-symmetry complex. Indeed, the metal
center displays a perfect octahedral coordination geometry
with the metal center occupying a special position in the
crystal lattice (Figure 2). The high symmetry of this complex
Structure: The structures of [Cu(L1)2], [Fe(L1)3], and [Fe(L3)3]
were determined by single-crystal X-ray diffraction methods
(Table 1). The crystals were produced by solvent diffusion
Table 1. Crystal data for [Cu(L1)2], [Fe(L1)3], and [Fe(L3)3].
[Cu(L1)2]
[Fe(L1)3]
[Fe(L3)3]
empirical formula
crystal system
space group
unit cell dimensions
a [ä]
a [8]
b [ä]
b [8]
c [ä]
C52H36N4Cu
triclinic
P1
C75H51N6F
e
99H69N6CFe
monoclinic
P21/c
rhombohedral
≈
≈
R3c
9.378(1)
14.455(1)
84.738(1)
14.455(1)
84.738(1)
14.455(1)
84.738(1)
2984.2(2), 2
28.896(2)
90
15.122(1)
91.484(1)
17.094(1)
90
104.721(2)
13.821(1)
99.250(2)
16.635(2)
104.753(2)
1957.2(3), 2
g [8]
volume [ä3], Z
crystal size [mm]
temperature [K]
reflections collected
independent
reflections
R(int)
7466.7(8), 4
0.21 Â 0.20 Â 0.20 0.34 Â 0.32 Â 0.12 0.48 Â 0.35 Â 0.03
100(2)
16330
8499
100(2)
24747
2298
100(2)
45623
16911
0.0253
0.0326
0.0426
data/restraints/
parameters
8499/0/514
2298/0/119
16911/0/955
goodness-of-fit on F 2 1.034
final R
1.075
1.023
indices I > 2s(I)
R1
wR2
0.0518
0.1445
0.0393
0.0999
0.0510
0.1164
R indices (all data)
R1
wR2
largest peak/hole
difference [eäÀ3
0.0551
0.1477
2.215/ À 0.631
0.0497
0.1043
0.339/ À 0.267
0.0821
0.1292
0.699/ À 0.473
Figure 2. Structural diagram of [Fe(L1)3] with partial atom numbering
schemes (ORTEP, 50% probability ellipsoids). Hydrogen atoms and
disordered solvent have been omitted for clarity.
]
in the solid state is unlike similar octahedral complexes of a,b-
unsubstituted dipyrrins reported to date, where the geometry
at the metal center is typically distorted such that no threefold
axis is present.[16, 17] The idealized symmetry of the complex
methods by using a solution of the metal complex into which
either hexanes or cyclohexane was slowly diffused. Like other
metal complexes based on dipyrrin ligands, the complexes
prepared here produced deeply colored crystals that appeared
either red and/or a lustrous deep green. The copper complex
[Cu(L1)2] displays the expected four-coordinate distorted
square-planar coordination geometry (Figure 1), with a twist
À
generates a Fe N distance of 1.959 ä and an interplane angle
between the dipyrrin and phenylacetylenylene p systems of
738. Although the phenyl groups of each ligand are twisted
relative to one another, the phenylacetylenylene units are
overall linear in structure with no apparent bending along the
ligand axis. The rigid structure and high symmetry of this
complex suggests that appropriately substituted derivatives
may be very useful for prepar-
À
angle between the two dipyrrin planes of ꢀ468. The Cu N
bond lengths are all comparable at 1.942, 1.951, 1.947, and
1.943 ä. The phenylacetylenylene moieties lie out of the plane
ing heterometallic honeycomb
framework molecular solids.[8, 9]
Crystals of the iron complex
[Fe(L3)3] were obtained as thin
hexagonal plates by slow evap-
oration from benzene. Al-
though this morphology was
suggestive of a high-symmetry
complex (vide supra), a struc-
Figure 1. Structural diagram of [Cu(L1)2] with partial atom numbering schemes (ORTEP, 50% probability
ellipsoids). Hydrogen atoms and solvent have been omitted for clarity.
ture from these crystals was not
achieved due to their extremely
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Phenylacetylene Rods with meso-Substituted Dipyrrin Ligands
4661 4669
thin dimension and fragility. Ultimately, the structure of
[Fe(L3)3] was determined from thin plates (which did not show
a hexagonal morphology), grown from solvent diffusion
methods. The structure shows the expected distorted octahe-
dral complex (Figure 3) lacking the perfect three-fold sym-
previously reported iron dipyrrin compounds,[16] complexes
[Fe(LN)3] (N ˆ 1, 2, 3, or 4) display quasireversible redox
couples centered around À1.152 V (À0.692 V versus SCE)
with an average DEp value of 0.119 V for all four complexes.
Table 2 summarizes the individual electrochemical results for
1
À
metry observed in [Fe(L )3]. The average Fe N bond length is
1.960 ä and the twist angles between the dipyrrin and phenyl
p systems for each ligand are 658, 678, and 848. A notable
feature of the structure is the bending observed along the axis
of the coordinated ligands (Figure 3).
Table 2. Electrochemical data for [Fe(L1)3], [Fe(L2)3], [Fe(L3)3], and
[Fe(L4)3].
Compound
Potential versus
Fc [V]
Potential versus
SCE [V]
DEp [V]
[Fe(L1)3]
[Fe(L2)3]
[Fe(L3)3]
[Fe(L4)3]
À 1.156
À 1.147
À 1.155
À 1.150
À 0.697
À 0.687
À 0.695
À 0.690
0.105
0.086
0.145
0.140
each compound. Based on this data the phenylacetylenylene
moiety does not significantly contribute to the electrochem-
ical behavior of the metal center. The electrochemical
behavior of these complexes may serve as a useful tool to
examine the incorporation of these building blocks in supra-
molecular structures.
UV/Vis spectroscopy: The combination of the phenylacet-
ylenylene groups with the dipyrrin chelators provides these
ligands and the resulting metal complexes with a rich
absorption spectroscopy. Absorption spectra were collected
for all of the phenylacetylenylene-substituted aldehydes,
dipyrromethanes, dipyrrins, and metal complexes synthesized.
The absorption spectra of the aldehydes and dipyrromethanes
for each phenylacetylenylene system generally displayed
fairly similar broad, high energy transitions below 350 nm.
For example, compounds 3 and 4 had similar absorption
spectra with maxima at 282/298 nm and 284/302 nm, respec-
tively. These broad, intense features are assigned to p p*
transitions of the phenylacetylenylene systems.[5] Compounds
7 and 8 display the most significantly red-shifted spectra with
maxima at 338 nm and 324/346 nm, respectively. This is
consistent with the extended p-conjugation of this system
due to the para substitution pattern at the central benzene
ring.[5] Compounds 10 and 11 do not display this large red-
shift, indicating that the meta substitution pattern on the
central benzene ring disrupts the extended conjugation of the
p system. Upon oxidation with DDQ, all of the compounds
display a new absorption band centered around 435 nm, which
is ascribed to the p p* transition of the dipyrrin aromatic
system.[17, 18] In addition to the new band at 435 nm, dipyrrins
L1 and L4 display a second, less intense band centered at
342 nm for L1 and 332 nm for L4. This new band is not seen in
L2, but does appear to be present in L3, as a shoulder feature
of a more intense, higher energy absorption. These spectra
indicate that this transition only appears in dipyrrins where
the meso-phenyl group has para versus meta substitution, and
that the feature is not solely due to the formation of a dipyrrin
moiety. Additionally, this transition is affected by the
coordination of metal ions. In the copper and iron complexes
of L1 this band becomes better defined and shifts to slightly
lower energy at 356 and 348 nm, respectively (Figure 4). In
the complex [Cu(L4)2] this band shifts to lower energy at 354
Figure 3. Structural diagram of [Fe(L3)3] (top) with partial atom number-
ing schemes (ORTEP, 50% probability ellipsoids). Structural diagram of
one ligand from [Fe(L3)3] (bottom) with partial atom numbering schemes
(ORTEP, 50% probability ellipsoids), showing the notable bending of the
phenylacetylenylene portion of the ligand. Hydrogen atoms and solvent
have been omitted for clarity.
A search of the Cambridge Structural Database[29] revealed
only 17 structures containing a linear (central para substitu-
tion) phenyl-acetylene-phenyl-acetylene-phenyl oligomer,
several of which demonstrated bending along the acetylene
axis. Surprisingly, of these 17 compounds only one was found
to be a metal complex; a thiol-terminated oligomer that was
appended to a tris(osmium) cluster.[30] As such, the system
reported here represents the first structurally characterized
metal complex that contains multiple, chelating ligands
appended with these extended molecular units.
Attempts to crystallize the complexes containing the
ligands L2 or L4 were not successful. The high solubility of
these complexes in a variety of organic solvents (vide supra)
precluded the use of solvent diffusion methods. Attempts to
grow crystals by slow evaporation always resulted in forma-
tion of thin films, never the desired crystalline materials.
Electrochemistry: The electrochemical behavior of the iron
complexes was examined by cyclic voltammetry. Similar to
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S. M. Cohen and S. R. Halper
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dependent on the nature of the metal center,[17, 18] but not on
the nature of the phenylacetylenylene group as would be
anticipated for a metal dipyrrin charge transfer process. For
the iron complexes, two new broad absorptions appear
centered at around 444 and 490 nm. These two new transitions
are relatively close in intensity with extinction coefficients of
47900 and 36200mÀ1 cmÀ1, respectively. In the copper com-
plexes, two new transitions also arise, centered at 468 and
500 nm, but the intensities of these transitions differ more
significantly from one another (61700 versus 32600mÀ1 cmÀ1).
These spectral features of these metal complexes are con-
18]
sistent with similar compounds reported in the literature.[16
Fluorescence spectroscopy: The use of phenylacetyleny-
6]
lene[4 and boron-dipyrrin (BODIPY) groups[31, 32] in light-
harvesting systems prompted the examination of the fluo-
rescence properties of the compounds prepared in this study.
The fluorescence emission of the phenylacetylenylene alde-
hydes, dipyrromethanes, dipyrromethenes, and metal com-
plexes were examined as solutions in CH2Cl2. Of all the
aldehydes (1, 3, 7, 10) and dipyrromethanes synthesized (2, 4,
8, 11), only the para-substituted compounds 7 and 8 exhibited
a significant fluorescence emission (Figure 5). The emission
Figure 4. UV/Vis spectra for dipyrrin-metal complexes ([Fe(LN)3] top,
[Cu(LN)2] bottom) as determined in CH2Cl2 solution; complexes: ––:
2
3
L1;
: L ;
: L ;
: L4.
* * * *
*
*
and in [Fe(L4)3] to 344 nm. Based on these observations, this
transition is tentatively assigned as a p p* charge transfer
process between the p system of the phenylacetylenylene
group and the p system of the dipyrrin moiety. Continuing
studies of meso-substituted phenyl dipyrrins will be required
to more concretely elucidate the nature of this absorption
feature.
In solution, the metal complexes of these ligands appear
bright red, while in the solid state they are either deep red or
lustrous green in color. The absorption spectroscopy of the
metal complexes (Figure 4) preserves some of the features
found in the free ligands and generates additional charge
transfer transitions. The maintained transitions are those
associated with the phenylacetylenylene p p* transitions and
the cautiously assigned p p* charge transfer process between
the phenylacetylenylene and dipyrrin p systems as described
above. However the strong absorption features associated
solely with the dipyrrin p p* transitions, centered at
ꢀ435 nm is lost in favor of new features. The new bands are
3
* * * *
*
*
Figure 5. Fluorescence spectra for compounds 7 (
), 8 (
), L (
),
[Cu(L3)2] (––, no significant emission), and [Fe(L3)3] (- - - -, no significant
emission). Only compounds 7 and 8 show significant fluorescence emission.
Excitation wavelength ˆ 320 nm.
from the dipyrromethane 8 was considerably stronger than
that observed from aldehyde 7, probably due to the known
quenching properties of aldehyde substituents.[33, 34] The
fluorescence spectrum of 8 exhibited emission maxima at
352 and 368 nm consistent with the known emission features
of the extended phenylacetylenylene functionality.[30] In
addition a strong emission centered at ꢀ460 nm was ob-
served; the exact origin of this band has not been determined,
but the feature appears to have some concentration depend-
ent behavior and may be related to solution aggregation. The
dipyrrin oxidation products were all found to be virtually non-
fluorescent, and subsequently, none of the metal complexes
showed any emission properties.
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Phenylacetylene Rods with meso-Substituted Dipyrrin Ligands
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Method 1: Dipyrromethane 2 (0.080 g, 0.25 mmol) was dissolved in CHCl3
(150 mL) and stirred in an ice bath. DDQ (0.057 g, 0.25 mmol) was
dissolved in benzene (100 mL) and added slowly dropwise over the course
of 1 h. The solvent was then evaporated and the product was purified by
column chromatography (SiO2; CHCl3) to afford a yellow film. Yield: 30%
(0.024 g). 1H NMR (CDCl3 400 MHz, 258C): d ˆ 6.43 (d, 2H, J ˆ 4.4 Hz,
pyrH), 6.63 (d, 2H, J ˆ 4.4 Hz), 7.38 7.41 (m, 3H), 7.52 (d, 2H, J ˆ 8.1 Hz),
7.58 7.60 (m, 2H), 7.64 (d, 2H, J ˆ 8.1 Hz), 7.66 ppm (bs, 2H); 13C NMR
(CDCl3 100 MHz, 258C): d ˆ 88.8, 90.7, 117.6, 122.8, 123.8, 128.2, 128.3,
128.4, 130.6, 130.7, 131.5, 137.0, 140.5, 140.8, 143.6 ppm; ESI-MS: m/z: 321.3
Conclusion
Several routes have been explored for the preparation of a
new series of phenylacetylenylene compounds that contain a
dipyrrin porphrinoid unit. These studies have led to a general
method for the synthesis of metal-chelating ligands containing
these extended unsaturated groups. Eight different metal
complexes have been prepared and their electrochemical and
spectroscopic features have been studied. Three of these
metal complexes have been structurally characterized clearly
demonstrating that the metal centers can assemble and
organize these 'molecular rods' in a stoichiometric and
spatially defined fashion. The high symmetry and extended
structure of these complexes suggest their use as components
for supramolecular assembly; efforts to utilize these com-
pounds in expanded structures and molecular solids are
currently underway.
‡
[M ‡ H] ; lmax ˆ 286, 342, 436 nm.
Method 2: Dipyrromethane 2 (0.139 g, 0.43 mmol) was dissolved in CHCl3
(150 mL) and stirred in an ice bath. DDQ (0.109 g, 0.48 mmol) was
dissolved in benzene (100 mL) and added slowly dropwise. The solvent was
then evaporated to one-half the volume and Cu(acac)2 (0.068 g, 0.26 mmol)
was added to form the copper complex, which was purified by column
chromatography (vide infra). The copper complex was dissolved in THF
(75 mL). Potassium cyanide (0.200 g, 3.07 mmol) dissolved in H2O (20 mL)
was added to the copper complex, and the mixture was stirred overnight.
The solution turned from red to orange. The reaction mixture was
evaporated to dryness and the resulting residue was dissolved in CH2Cl2
(50 mL), washed with brine (50 mL) and H2O (50 mL), dried with Mg2SO4,
vacuum filtered, and the filtrate evaporated to dryness to afford a yellow
film. Yield: 36% (0.050 g, from 2; 57% from [Cu(L1)2]).
[Cu(L1)2]: Dipyrromethane 2 (0.139 g, 0.43 mmol) was dissolved in CHCl3
(150 mL) and stirred in an ice bath. DDQ (0.109 g, 0.48 mmol) was
dissolved in benzene (100 mL) and added slowly dropwise. The solvent was
then evaporated to one-half the volume and Cu(acac)2 (0.068 g, 0.26 mmol)
was added and the solution was stirred at room temperature for 5 10 min.
The reaction mixture was then evaporated to dryness and the resulting
residue was purified by column chromatography (SiO2; CHCl3) to afford a
dichroic red/green film. Yield: 63% (0.095 g). m.p. >3008C. APCI-MS:
Experimental Section
General: Unless otherwise noted, starting materials were obtained from
commercial suppliers and used without further purification. Mass spec-
trometry was performed either at the University of California, San Diego
Mass Spectrometry Facility in the Department of Chemistry and Bio-
chemistry, or at University of Arizona Mass Spectrometry Facility in the
Department of Chemistry. Elemental analysis was performed at the
University of California, Berkeley Analytical Facility. 1H/13CNMR spectra
were recorded on a Varian FT-NMR spectrometer running at 400 MHz at
the Department of Chemistry and Biochemistry, University of California,
San Diego. UV/Vis spectra were recorded in CH2Cl2 using a Hewlett-
Packard 4582A spectrophotometer under PC control using the ChemSta-
tion software suite.
‡
m/z: 702.1 [M ‡ H] ; elemental analysis calcd (%) for C46H30N4Cu ¥ H2O ¥
benzene: C 78.22, H 4.80, N 7.02; found: C 78.40, H 4.66, N 6.99; lmax ˆ 282,
292, 356, 468, 502 nm.
[Fe(L1)3]: Dipyrromethane 2 (0.150 g, 0.47 mmol) was dissolved in CHCl3
(150 mL) and stirred in an ice bath. DDQ (0.117 g, 0.51 mmol) was
dissolved in benzene (100 mL) and added slowly dropwise. After addition,
the reaction mixture was then evaporated to dryness and the resulting dark
residue was redissolved in a 1:1 mixture of CHCl3/MeOH (100 mL).
Triethylamine (2 mL) and FeCl3 ¥ 6H2O dissolved in MeOH (5 mL) was
added to the CHCl3/MeOH solution. The resulting mixture was heated to
reflux overnight (ꢀ14 h). The solution was evaporated to dryness and the
product was purified by column chromatography (SiO2; CHCl3) to afford a
4-(Phenylacetylenyl)benzaldehyde (1): A mixture of 4-bromobenzalde-
hyde (0.150 g, 0.81 mmol), phenylacetylenylene (0.331 g, 3.24 mmol),
triethylamine (0.123 g, 1.22 mmol), [Pd(PPh3)2Cl2] (0.028 g, 0.04 mmol),
triphenylphosphine (0.005 g, 0.02 mmol), CuI (0.002 g, 0.008 mmol), and
dry THF(15 mL) was stirred under nitrogen for 24 h. The reaction mixture
was diluted with CH2Cl2 (50 mL), washed with 0.1m EDTA (50 mL) and
brine (50 mL), and then dried over Mg2SO4. The Mg2SO4 was removed by
vacuum filtration, and the filtrate was evaporated to dryness. The resulting
brown oil was purified by column chromatography (SiO2; hexanes/CH2Cl2,
4:1) to afford a yellow solid. Yield: 64% (0.107 g). 1H NMR (CDCl3
400 MHz, 258C): d ˆ 7.34 7.36 (m, 3H), 7.51 7.54 (m, 2H), 7.67 (d, 2H,
J ˆ 8.0 Hz), 7.85 (d, 2H, J ˆ 8.4 Hz), 9.99 ppm (s, 1H, CHO); 13C NMR
(CDCl3 100 MHz, 258C): d ˆ 88.4, 93.7, 122.6, 128.7, 129.2, 129.7, 132.0,
dichroic red/green film. Yield: 59% (0.092 g); m.p. 2048C. APCI-MS: m/z:
‡
1013.7 [M ‡ H] ; analysis calcd (%) for C69H45N6F e ¥ HO ¥ hexane: C 80.56,
2
H 5.50, N 7.52; found: C 80.37, H 5.18, N 7.66; lmax ˆ 280, 292, 348, 444,
490 nm.
3-(Phenylacetylenyl)benzaldehyde (3): The same procedure was used as in
the synthesis of 1, starting from 3-iodobenzaldehyde (0.250 g, 1.08 mmol).
Yield: 77% (0.171 g); 1H NMR (CDCl3 400 MHz, 258C): d ˆ 7.35 7.37 (m,
3H), 7.49 (t, 1H, J ˆ 15.6 Hz), 7.54 7.56 (m, 2H), 7.74 7.76 (dt, 1H, J ˆ
8.4 Hz), 7.80 7.83 (dt, 1H, J ˆ 8.0 Hz), 8.01 (t, 1H, J ˆ 1.2 Hz), 9.99 ppm (s,
1H, CHO); 13C NMR (CDCl3 100 MHz, 258C): d ˆ 88.0, 91.1, 122.7, 124.6,
128.5, 128.8, 128.9, 129.2, 131.7, 133.0, 136.5, 137.1, 191.5 ppm; GC-EIMS:
‡
132.2, 132.6, 135.5, 191.4 ppm; APCI-MS: m/z: 207.2 [M ‡ H] ; lmax ˆ 312,
326 nm.
5-(4-Phenylacetylenylphenyl)dipyrromethane (2): Aldehyde 1 (0.107 g,
0.52 mmol) was dissolved in neat pyrrole (10 mL) and degassed by
bubbling with nitrogen for 20 min. Trifluoroacetic acid (0.01 mL,
0.09 mmol) was added. The solution was stirred for 10 min. It was diluted
with CH2Cl2 (50 mL), washed with 0.1m NaOH (50 mL) and water (50 mL)
then dried over Mg2SO4. The Mg2SO4 was removed by vacuum filtration
and the filtrate was evaporated to remove CH2Cl2. The remaining pyrrole
was removed by vacuum distillation with gentle heating. The product was
purified by column chromatography (SiO2; hexanes/CH2Cl2, 1:1) to afford
a yellow foam. Yield: 83% (0.139 g). 1H NMR (CDCl3 400 MHz, 258C):
d ˆ 5.46 (s, 1H) 5.95 (s, 2H), 6.23 (q, 2H, J ˆ 2.8 Hz, J ˆ 2.8 Hz), 6.71 (m,
2H), 7.23 (d, 2H, J ˆ 8.4 Hz), 7.39 7.41 (m, 3H), 7.55 (d, 2H, J ˆ 8.4 Hz),
7.58 7.61 (m, 2H), 7.88 ppm (bs, 2H, NH); 13C NMR (CDCl3 100 MHz,
258C): d ˆ 44.2, 89.5, 89.8, 107.7, 108.7, 117.7, 122.1, 123.4, 128.5, 128.6, 128.7,
.
‡
m/z: 206.1 [M ] ; lmax ˆ 282, 298 nm.
5-(3-Phenylacetylenylphenyl)dipyrromethane (4): The same procedure
was used as in the synthesis of 2, starting from 3 (0.171 g, (0.83 mmol).
Yield: 76% (0.204 g); 1H NMR (CD2Cl2 400 MHz, 258C): d ˆ 5.48 (s, 1H),
5.96 (m, 2H), 6.23 (q, 2H, J ˆ 2.8, Hz J ˆ 2.4 Hz), 6.73 (q, 2H, J ˆ 2.0, Hz
J ˆ 2.4 Hz), 7.26 (d, 1H, J ˆ 8.4 Hz), 7.38 (t, 1H, J ˆ 7.6 Hz), 7.42 7.45 (m,
3H), 7.47 (s, 1H), 7.52 (d, 1H, J ˆ 8.0 Hz), 7.60 7.62 (m, 2H), 7.99 ppm (bs,
2H, NH); 13C NMR (CDCl3 100 MHz, 258C): d ˆ 44.1, 89.5, 89.6, 107.5,
108.6, 117.7, 123.3, 123.6, 128.5, 128.6, 128.7, 128.9, 130.3, 131.5, 131.8, 132.3,
‡
‡
143.1 ppm; APCI-MS: m/z: 323.1 [M ‡ H] , 256.3 [M À pyrrole] ; lmax
ˆ
284, 302 nm.
5-(3-Phenylacetylenylphenyl)-4,6-dipyrromethene (L2): The same proce-
dure was used as in the synthesis of L1 (Method 1), starting from 4 (0.204 g,
‡
131.8, 132.0, 132.2, 142.6 ppm; APCI-MS: m/z: 323.1 [M ‡ H] , 256.3 [M À
‡
1
pyrrole] ; lmax ˆ 288, 306 nm.
0.63 mmol). Yield: 42% (0.086 g); H NMR (CDCl3 400 MHz, 258C): d ˆ
5-(4-Phenylacetylenylphenyl)-4,6-dipyrromethene (L1):
6.42 (d, 2H, J ˆ 2.8 Hz), 6.62 (d, 2H, J ˆ 2.8 Hz), 7.33 7.34 (m, 3H), 7.42
Chem. Eur. J. 2003, 9, 4661 4669
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4667

S. M. Cohen and S. R. Halper
FULL PAPER
‡
131.5, 137.2, 140.5, 140.8, 143.7 ppm; ESI-MS: m/z: 421.3 [M ‡ H] ; lmax
ˆ
7.43 (m, 2H), 7.51 7.53 (m, 2H), 7.64 7.66 (m, 2H), 7.70 ppm (t, 2H, J ˆ
1.2 Hz); 13C NMR (CDCl3 100 MHz, 258C): d ˆ 88.6, 90.1, 117.6, 122.7,
122.8, 127.6, 128.2, 128.3, 129.6, 130.4, 131.4, 131.5, 132.0, 133.4, 137.2, 139.3,
324, 436 nm.
[Cu(L3)2]: The same procedure was used as in the synthesis of [Cu(L1)2],
starting from 8 (0.130 g, 0.31 mmol). Yield: 69% (0.096 g). m.p. >3008C;
‡
143.7 ppm; APCI-MS: m/z: 321.3 [M ‡ H] ; lmax ˆ 288, 434 nm.
‡
MALDI-TOF-MS: m/z: 902.40 [M ‡ H] ; analysis calcd for C62H38N4Cu: C
[Cu(L2)2]: The same procedure was used as in the synthesis of [Cu(L1)2],
82.51, H 4.24, N 6.21; found: C 82.43, H 4.58, N 5.97. lmax ˆ 322, 468, 500 nm.
starting from purified L2 (0.034 g, 0.11 mmol). Yield: 81% (0.030 g); m.p.
[Fe(L3)3]: The same procedure was used as in the synthesis of [Fe(L1)3],
starting from 8 (0.340 g, 0.80 mmol). Yield: 48% (0.170 g). m.p. 1968C.
‡
1468C; MALDI-TOF-MS: m/z: 702.58 [M ‡ H] ; elemental analysis calcd
(%) for C46H30N4Cu: C 78.67, H 4.31, N 7.98; found: C 78.85, H 4.42, N 7.68;
‡
MALDI-TOF-MS: m/z: 1313.44 [M ‡ H] ; analysis calcd (%) for
lmax ˆ 284, 298, 468, 500 nm.
C93H57N6Fe: C 84.99, H 4.37, N 6.39; found: C 85.00, H 4.36, N 6.50;
[Fe(L2)3]: The same procedure was used as in the synthesis of [Fe(L1)3],
lmax ˆ 320, 444, 490 nm.
starting from purified L2 (0.026 g, 0.081 mmol). Yield: 91% (0.025 g); m.p.
4-(3-Iodophenylacetylenyl)benzaldehyde (9): A mixture of 5 (0.200 g,
1.54 mmol), 1,3-diiodobenzene (1.52 g, 4.61 mmol), triethylamine (0.155 g,
1.54 mmol), [Pd(PPh3)2Cl2] (0.054 g, 0.08 mmol), triphenylphosphine
(0.010 g, 0.04 mmol), CuI (0.006 mg, 0.03 mmol), and dry THF(15 mL)
was stirred under nitrogen for three days. The reaction mixture was diluted
with CH2Cl2 (50 mL), washed with 0.1m EDTA (50 mL) and brine (50 mL),
and was then dried over Mg2SO4. The Mg2SO4 was removed by vacuum
filtration and the filtrate was evaporated to dryness. The remaining residue
was purified by column chromatography (SiO2; hexanes/CH2Cl2, 1:1) to
afford a yellow solid. Yield: 82% (0.420 g). 1H NMR (CDCl3 400 MHz,
258C): d ˆ 7.11 (t, 1H, J ˆ 8.0 Hz), 7.52 (dt, 1H, J ˆ 8.0 Hz), 7.67 (d, 2H, J ˆ
8.0 Hz), 7.72 (dt, 1H, J ˆ 8.0 Hz), 7.88 (d, 2H, J ˆ 8.4 Hz), 7.91 (t, 1H, J ˆ
2.0 Hz), 10.02 ppm (s, 1H, CHO); 13C NMR (CDCl3 100 MHz, 258C): d ˆ
89.6, 91.4, 93.7, 124.4, 128.8, 129.4, 129.80, 130.7, 132.0, 135.4, 137.7, 140.1,
‡
1768C; APCI-MS: m/z: 1013.8 [M ‡ H] ; elemental analysis calcd (%) for
C69H45N6Fe: C 81.73, H 4.47, N 8.29; found: C 81.70, H 4.55, N 8.22; lmax
284, 300, 444, 496 nm.
ˆ
4-(Ethynyl)benzaldehyde (5): 4-[(Trimethylsilyl)ethynyl]benzaldehyde
(1.00 g, 4.94 mmol) was dissolved in methanol (50 mL) to which K2CO3
(0.500 g, 3.62 mmol) was added. The reaction mixture was stirred for
15 min at which point the starting material was completely consumed as
judged by TLC and GC-MS. The reaction mixture was evaporated to
dryness and dissolved in CH2Cl2 (50 mL), washed with aqueous sodium
bicarbonate (50 mL), and dried over Mg2SO4. The Mg2SO4 was removed by
vacuum filtration, and the filtrate was evaporated to dryness to afford a
yellow solid. Yield: 96% (0.617 g). 1H NMR (CDCl3 400 MHz, 258C): d ˆ
3.30 (s, 1H), 7.57 (d, 2H, J ˆ 8.0 Hz), 7.78 (d, 2H, J ˆ 8.4 Hz), 9.94 ppm (s,
1H, CHO); 13C NMR (CDCl3 100 MHz, 258C): d ˆ 81.5, 82.9, 128.3, 129.6,
.
‡
191.1 ppm; GC-EIMS: m/z: 332.1 [M ] ; lmax ˆ 310, 328 nm.
.
‡
132.8, 136.0, 191.3. GC-EIMS: m/z: 130.7 [M ] .
4-[3-(Phenylacetylenyl)phenylacetylenyl]benzaldehyde (10): The same
procedure was used as in the synthesis of 1, starting from 9 (0.400 g,
1.20 mmol) and phenylacetylenylene (0.369 g, 3.60 mmol). After three
days, the reaction mixture was diluted with CH2Cl2 (50 mL), washed with
0.1m EDTA (50 mL) and brine (50 mL), and was then dried over Mg2SO4.
The Mg2SO4 was removed by vacuum filtration and the filtrate was
evaporated to dryness. The remaining residue was purified by column
chromatography (SiO2; CH2Cl2) to afford a yellow solid. Yield: 90%
(0.332 g). 1H NMR (CDCl3 400 MHz, 258C): d ˆ 7.33 7.37 (m, 4H), 7.49
7.56 (m, 4H), 7.68 (d, 2H, J ˆ 7.6 Hz), 7.74 (s, 1H), 7.87 (d, 2H, J ˆ 8.0 Hz),
10.01 ppm (s, 1H, CHO); 13C NMR (CDCl3 100 MHz, 258C): d ˆ 88.2, 89.0,
90.2, 92.4, 122.6, 122.7, 123.6, 128.2, 128.3, 128.4, 129.0, 129.4, 131.2, 131.4,
4-(4-Iodophenylacetylenyl)benzaldehyde (6): A mixture of 5 (0.300 g,
2.31 mmol), 1,4-diiodobenzene (3.042 g, 9.22 mmol), triethylamine
(0.349 g, 3.46 mmol), [Pd(PPh3)2Cl2] (0.081 g, 0.12 mmol), triphenylphos-
phine (0.015 g, 0.06 mmol), CuI (0.009 g, 0.05 mmol), and dry THF(15 mL)
was stirred under nitrogen for four days. The reaction mixture was diluted
with CH2Cl2 (50 mL), washed with 0.1m EDTA (50 mL) and brine (50 mL),
and was then dried over Mg2SO4. The Mg2SO4 was removed by vacuum
filtration and the filtrate was evaporated to dryness. The remaining residue
was purified by column chromatography (SiO2; hexanes/CH2Cl2, 1:1) to
afford a yellow solid. Yield: 73% (0.560 g). 1H NMR (CDCl3 400 MHz,
258C): d ˆ 7.28 (d, 2H, J ˆ 8.4 Hz), 7.67 (d, 2H, J ˆ 8.4 Hz), 7.72 (d, 2H, J ˆ
8.4 Hz), 7.87 (d, 2H, J ˆ 8.4 Hz), 10.02 ppm (s, 1H, CHO); 13C NMR
(CDCl3 100 MHz, 258C): d 89.8, 92.3, 95.0, 121.8, 127.7, 129.0, 129.4, 131.8,
.
‡
131.7, 131.9, 134.5, 135.3, 191.0 ppm; GC-EIMS: m/z: 306.3 [M ] ; lmax
286, 304 nm.
ˆ
.
‡
133.0, 137.5, 191.0 ppm; GC-EIMS: m/z: 332.1 [M ] . lmax ˆ 320, 334 nm.
5-[3-((Phenylacetylenyl)phenylacetylenyl)phenyl]dipyrromethane
(11):
The same procedure was used as in the synthesis of 2, starting from 10
(0.330 g, 1.08 mmol). Yield: 90% (0.410 g). 1H NMR (CDCl3 400 MHz,
258C): d ˆ 5.49 (s, 1H), 5.93 (m, 2H), 6.18 (q, 2H, J ˆ 3.2 Hz, J ˆ 2.8 Hz),
6.72 (m, 2H), 7.22 (d, 2H, J ˆ 8.0 Hz), 7.32 7.38 (m, 4H), 7.48 7.51 (m,
4H), 7.55 7.56 (m, 2H), 7.72 (t, 1H, J ˆ 1.6 Hz), 7.94 ppm (bs, 2H, NH);
13C NMR (CDCl3 100 MHz, 258C): d ˆ 43.9, 88.4, 88.5, 89.6, 89.9, 107.3,
108.4, 117.3, 121.5, 122.8, 123.4, 123.5, 128.2, 128.3, 131.1, 131.5, 131.7, 134.4,
4-[4-(Phenylacetylenyl)phenylacetylenyl]benzaldehyde (7): The same pro-
cedure was used as in the synthesis of 1, starting from 6 (0.200 g, 0.60 mmol)
and phenylacetylenylene (0.184 g, 1.8 mmol). After three days, the reaction
mixture was diluted with CH2Cl2 (50 mL), washed with 0.1m EDTA
(50 mL) and brine (50 mL), and was then dried over Mg2SO4. The Mg2SO4
was removed by vacuum filtration and the filtrate was evaporated to
dryness. The remaining residue was purified by column chromatography
(SiO2; CH2Cl2) to afford a yellow solid. Yield: 72% (0.133 g); 1H NMR
(CDCl3 400MHz, 258C): d ˆ 7.36 (m, 3H), 7.54 (m, 6H), 7.69 (d, 2H, J ˆ
8.0 Hz), 7.89 (d, 2H, J ˆ 8.0 Hz), 10.03 ppm (s, 1H, CHO); 13C NMR
(CDCl3 100 MHz, 258C): d ˆ 88.9, 90.2, 91.6, 93.0, 122.1, 122.7, 123.8, 128.3,
128.4, 129.2, 129.5, 131.4, 131.5, 131.6, 132.0, 135.3, 191.1 ppm; GC-EIMS:
‡
142.3 ppm; MALDI-TOF-MS: m/z: 421.23 [M ‡ H] ; lmax ˆ 286, 302 nm.
5-[3-((Phenylacetylenyl)phenylacetylenyl)phenyl]-4,6-dipyrromethene
(L4): The same procedure was used as in the synthesis of L1 (Method 2),
starting from 11 (0.250 g, 0.59 mmol). Yield: 36% (0.090 g); 1H NMR
(CDCl3 400 MHz, 258C): d ˆ 6.43 (d, 2H, J ˆ 2.8 Hz), 6.64 (d, 2H, J ˆ
3.2 Hz), 7.37 7.39 (m, 4H), 7.51 7.58 (m, 6H), 7.63 (d, 2H, J ˆ 8.8 Hz), 7.67
(s, 2H), 7.79 ppm (s, 1H); 13C NMR (CDCl3 100 MHz, 258C): d ˆ 88.4, 89.4,
89.9, 90.1, 117.7, 122.8, 123.2, 123.5, 123.6, 128.2, 128.3, 128.4, 128.5, 130.7,
131.1, 131.3, 131.5, 134.5, 137.2, 140.5, 140.8, 143.6 ppm; ESI-MS: m/z: 421.3
.
‡
m/z: 306.3 [M ] . lmax ˆ 338 nm.
5-[4-((Phenylacetylenyl)phenylacetylenyl)phenyl]dipyrromethane
(8):
The same procedure was used as in the synthesis of 2, starting from 7
(0.133 g, 0.43 mmol). Yield: 75% (0.138 g); 1H NMR (CDCl3 400 MHz,
258C): d ˆ 5.48 (s, 1H), 5.93 (m, 2H), 6.19 (q, 2H, J ˆ 2.8 Hz, J ˆ 3.2 Hz),
6.71 (m, 2H), 7.22 (d, 2H, J ˆ 8.0 Hz), 7.37 (m, 3H), 7.49 7.57 (m, 8H),
7.90 ppm (bs, 2H, NH); 13C NMR (CDCl3 100 MHz, 258C): d ˆ 43.8, 89.0,
89.1, 90.9, 91.2, 107.3, 108.4, 117.3, 121.5, 122.8, 122.9, 123.0, 128.2, 128.3,
131.3, 131.4, 131.7, 131.8, 142.3 ppm; MALDI-TOF-MS: m/z: 422.23 [M ‡
‡
[M ‡ H] ; lmax ˆ 286, 302, 332, 432 nm.
[Cu(L4)2]: The same procedure was used as in the synthesis of [Cu(L1)2],
starting from 11 (0.250 g, 0.59 mmol). Yield: 47% (0.125 g); m.p. 1008C;
‡
MALDI-TOF-MS: m/z: 901.20 [M ‡ H] ; elemental analysis calcd (%) for
C62H38N4Cu: C 82.51, H 4.24, N 6.21; found: C 82.25, H 4.36, N 6.23; lmax
284, 354, 470, 502 nm.
ˆ
‡
H] ; lmax ˆ 324, 346 nm.
[Fe(L4)3]: The same procedure was used as in the synthesis of [Fe(L1)3],
starting from 11 (0.150 g, 0.36 mmol). Yield: 57% (0.088 g); m.p. 1578C.
5-[4-((Phenylacetylenyl)phenylacetylenyl)phenyl]-4,6-dipyrromethene
(L3): The same procedure was used as in the synthesis of L1 starting from 8
(0.202 g, 0.48 mmol). Yield: 13% (0.026 g); 1H NMR (CDCl3 400 MHz,
258C): d ˆ 6.42 (d, 2H, J ˆ 2.8 Hz), 6.62 (d, 2H, J ˆ 3.2 Hz), 7.36 7.39 (m,
3H), 7.52 (d, 2H, J ˆ 8.0 Hz), 7.55 7.57 (m, 6H), 7.63 (d, 2H, J ˆ 8.0 Hz),
7.66 ppm (s, 2H); 13C NMR (CDCl3 100 MHz, 258C): d 89.0, 90.4, 90.6, 91.4,
117.7, 122.6, 122.8, 123.2, 123.6, 128.3, 128.4, 128.5, 130.7, 130.8, 131.3, 131.4,
‡
MALDI-TOF-MS: m/z: 1313.38 [M ‡ H] ; analysis calcd for C93H57N6Fe:
C 84.99, H 4.37, N 6.39; found: C 84.77, H 4.55, N 6.45; lmax ˆ 284, 344, 444,
494 nm.
X-ray crystallographic analysis: Data was collected on a Bruker AXS area
detector diffractometer. Crystals were mounted on quartz capillaries by
4668
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 4661 4669

Phenylacetylene Rods with meso-Substituted Dipyrrin Ligands
4661 4669
using Paratone oil and were cooled in a nitrogen stream (Kryo-flex
controlled) on the diffractometer (À1738C). Peak integrations were
performed with the Siemens SAINT software package with absorption
corrections applied using the program SADABS. Space group determi-
nations were performed by the program XPREP and the structures were
solved (by direct or Patterson methods) and refined with the SHELXTL
software package.[35] Unless noted otherwise, all hydrogen atoms were fixed
at calculated positions with isotropic thermal parameters; all non-hydrogen
atoms were refined anisotropically.
University of California, San Diego, the Chris and Warren Hellman Faculty
Scholar award (S.M.C.), and GAANN Fellowship Number GM-60202 03
(S.R.H.).
[1] S. Hˆger, V. Enkelmann, K. Bonrad, C. Tschierske, Angew. Chem.
2000, 112, 2355; Angew. Chem. Int. Ed. 2000, 39, 2267.
[2] J. Zhang, J. S. Moore, J. Am. Chem. Soc. 1994, 116, 2655.
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[4] C. Devadoss, P. Bharathi, J. S. Moore, J. Am. Chem. Soc. 1996, 118,
9635.
[5] J. S. Melinger, Y. Pan, V. D. Kleiman, Z. Peng, B. L. Davis, D.
McMorrow, M. Lu, J. Am. Chem. Soc. 2002, 124, 12002.
[6] Z. Xu, M. Kahr, K. L. Walker, C. L. Wilkins, J. S. Moore, J. Am. Chem.
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[7] C. B. Gorman, J. C. Smith, M. W. Hager, B. L. Parkhurst, H. Sierzpu-
towska-Gracz, C. A. Haney, J. Am. Chem. Soc. 1999, 121, 9958.
[8] Y.-H. Kiang, G. B. Gardner, S. Lee, Z. Xu, E. B. Lobkovsky, J. Am.
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[9] Y.-H. Kiang, S. Lee, Z. Xu, W. Choe, G. B. Gardner, Adv. Mater. 2000,
12, 767.
CCDC-208199, CCDC-208200, and CCDC-208201 contain the supplemen-
tary crystallographic data for this paper. These data can be obtained free of
charge via www.ccdc.can.ac.uk/conts/retrieving.html (or from the Cam-
bridge Crystallographic Center, 12 Union Road, Cambridge CB21EZ,
UK; Fax: (‡44)1223-336033; or deposit@ccdc.cam.ac.uk).
[Cu(L1)2]: Dark green blocks were grown out of a solution of the complex
in a mixture of CH2Cl2 containing a small amount of benzene diffused with
≈
hexanes. The complex crystallized in the triclinic space group P1 (Z ˆ 2,
a ˆ 9.378, b ˆ 13.821, c ˆ 16.635 ä, a ˆ 104.721, b ˆ 99.250, g ˆ 104.7538).
The complex co-crystallized with one molecule of benzene in the
asymmetric unit.
[Fe(L1)3]: Dark green hexagons were grown out of a solution of the
[10] M. P. Suh, H. J. Choi, S. M. So, B. M. Kim, Inorg. Chem. 2003, 42, 676.
[11] J. P. Novak, D. L. Feldheim, J. Am. Chem. Soc. 2000, 122, 3979.
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complex in benzene diffused with hexanes. The complex crystallized in the
≈
rhombohedral space group R3c (Z ˆ 2, a ˆ 14.455 ä, a ˆ 84.7388). The
asymmetric unit contains a molecule of highly disordered benzene. It was
treated as a diffuse contribution using the program SQUEEZE (A. Spek,
Platon Library). Electron count/unit cell: 92 (found), 84 (expected). The
determined and calculated intensive properties include the solvent
molecule, but individual atoms do not appear in the atom lists.
[Fe(L3)3]: Dark green thin plates were grown out of a solution of the
complex in benzene diffused with cyclohexane. The complex crystallized in
the monoclinic space group P21/c (Z ˆ 4, a ˆ 28.896, b ˆ 15.122, c ˆ
17.094 ä, b ˆ 91.4848). The complex co-crystallized with one molecule of
cyclohexane in the asymmetric unit.
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Electrochemistry: Cyclic voltammetry experiments were performed by
using a Bioanalytical Systems (BAS) CV-50W voltametric analyzer under
PC control.[16] Solutions were prepared by dissolving 5 15 mg of metal
complex in dried, degassed CH2Cl2 containing 0.1m nBu4N(PF6). The
auxiliary and reference electrodes were a platinum wire and a silver
electrode (Ag/AgCl(aq)), respectively. A platinum electrode (BAS) was
used for the working electrode. Samples were purged with N2(g) for
ꢀ2 minutes before experiments were performed. Sweep rates were varied
from 0.050 to 1.500 VsÀ1 to check the reversibility of the couple. All data
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are reported at ambient temperature (258C) with
a sweep rate of
‡
0.500 VsÀ1. The ferrocenium/ferrocene couple (Fc /Fc8) was measured
under identical conditions for use as a reference measurement (E1/2
ˆ
‡0.471 V, DEp ˆ 0.127 V, 0.500 VsÀ1). All potentials are reported relative
‡
to Fc /Fc8, unless otherwise stated. Potentials reported relative to the
aqueous standard calomel electrode (SCE), were adjusted using the
SCE
Fc
equation E1/2 ˆ E1/2 ‡ 0.46 V, based on the data obtained here and
reports in the literature[36 38] indicating that the ferrocene couple in CH2Cl2
with nBu4N(PF6) electrolyte is approximately ‡0.46 V relative to SCE.
Fluorescence measurements: Measurements were performed on a Photon
Technologies International QuantaMaster 2000 spectrophotometer. Sol-
utions of each compound were prepared in CH2Cl2 to a concentration of
ꢀ10À5 m; no efforts were made to exclude air or water. All reported
measurements were taken in a 1.0 cm quartz cuvette at a slit width of 3 nm
with an excitation wavelength of 320 nm.
[34] G. G. Guilbault, Practical Fluorescence, 2nd ed., Marcel Dekker, New
York, 1990.
[35] G. M. Sheldrick, in SHELXTL vers. 5.1 Software Reference Manual,
Brucker AXS, Madison, WI, 1997.
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1659; Angew. Chem. Int. Ed. 1998, 37, 1556.
Acknowledgement
We thank Jesse Mello and Prof. Nathaniel Finney (U.C. San Diego) for use
and assistance with their fluorimeter, Dr. Lev N. Zakharov and Prof.
Arnold L. Rheingold (U.C. San Diego) for assistance with the crystallog-
raphy, Dr. Linda Breci (U. of Arizona) for assistance with obtaining several
mass spectra, and Dr. Ulla N˘rklit Andersen (U.C. Berkeley) for assistance
with obtaining the elemental analysis. This work was supported by the
[38] M. T. Miller, P. K. Gantzel, T. B. Karpishin, Inorg. Chem. 1999, 38,
3414.
Received: April 12, 2003 [F5041]
Chem. Eur. J. 2003, 9, 4661 4669
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4669