Synthesis of 5,10-diphenylporphyrin

Article abstract of DOI:10.1016/S0040-4020(02)00408-8

The synthesis and spectroscopic properties of hitherto unknown 5,10-diphenylporphyrin (3) are described. 2+2 and 3+1 Pathways were tested for the making of 5,10-diphenylporphyrin. The most successful method involved the condensation of an appropriately substituted dipyrromethane dicarbinol with dipyrromethane to provide the title compound in up to 20% yield. The structure of 3 was unambiguously established by ¹H and ¹³C NMR spectroscopy. The UV-vis, fluorescence and NMR data of 5,10-diphenylporphyrin and its Zn(II) and Ni(II) complexes are described and contrasted with those for the isomeric 5,15-diphenyl- and 5,10,15,20-tetraphenylporphyrin.

Full text of DOI:10.1016/S0040-4020(02)00408-8

TETRAHEDRON
Pergamon
Tetrahedron 58 )2002) 4375±4381
Synthesis of 5,10-diphenylporphyrin
Raymond P. BrinÄas and Christian BruÈcknerp
Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060, USA
Received 27 February 2002; accepted 12 April 2002
AbstractÐThe synthesis and spectroscopic properties of hitherto unknown 5,10-diphenylporphyrin )3) are described. 212 and 311 Path-
ways were tested for the making of 5,10-diphenylporphyrin. The most successful method involved the condensation of an appropriately
substituted dipyrromethane dicarbinol with dipyrromethane to provide the title compound in up to 20% yield. The structure of 3 was
1
unambiguously established by H and 13C NMR spectroscopy. The UV±vis, ¯uorescence and NMR data of 5,10-diphenylporphyrin and
its Zn)II) and Ni)II) complexes are described and contrasted with those for the isomeric 5,15-diphenyl- and 5,10,15,20-tetraphenylporphyrin.
q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
novel water-soluble meso-sulfonated porphyrins,11
ABCD-12 and A2B2-type porphyrins,5 5,15-diphenyl-
porphyrin derivatives with non-linear optical properties,13,14
and multiporphyrin assemblies.15,16 Modern strategies for
the synthesis of 5,15-DPP are available.8,9,17,18
Arguably, the most studied synthetic porphyrin family are
the 5,10,15,20-tetraarylporphyrins )TPP, 1). The synthetic
protocols toward the synthesis of tetraarylporphyrins
containing identical or differing aryl groups have developed
in recent years to a high degree of sophistication.1±5 5,10,15-
Triaryl-6 and 5,15-diaryl-porphyrins )5,15-DPP, 2)7±9 are
much less studied.
The cis-isomer to 5,15-DPP, 5,10-diphenylporphyrin )5,10-
DPP, 3) has not been described, though a 5,10-diarylchlorin
made via tetrahydrobilene cyclization was recently
reported.19 Aretrosynthetic analysis of 5,10-DPP
rationalizes this seemingly surprising fact )Fig. 1). Unlike
symmetrically substituted 5,15-DPP or TPP, 5,10-DPP
cannot be prepared by simple condensation of two identical
dipyrrolic subunits. Instead, two more complex approaches
are plausible. Option A: a disconnection based on a 311
condensation of known 5,10-diphenyltripyrrane 4 with an
electrophilic monopyrrolic synthon 5 such as 2,5-diformyl-
pyrrole or its )formal) reduction product 2,5-di)hydroxy-
They are, however, interesting because they combine some
features of meso-tetraarylporphyrins, namely the unsubsti-
tuted b-positions and the meso-aryl groups, with features of
the b-octaalkylporphyrins, namely the unsubstituted meso-
positions. These features have been utilized in the synthesis
of, for instance, benzochlorins,10 bio-conjugated porphyrins,10
Keywords: 5,10-diphenylporphyrin; dipyrromethane; 212 synthesis; 311
synthesis.
p
Corresponding author. Tel.: 11-860-486-2743; fax: 11-860-486-2981;
e-mail: c.bruckner@uconn.edu
Figure 1. Retrosynthetic analysis of 3.
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020)02)00408-8

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R. P. BrinÄas, C. Bruckner / Tetrahedron 58 +2002) 4375±4381
4376
methyl)-pyrrole. Anumber of successful 3 11 approaches
toward the synthesis of porphyrins and porphyrin analogs
were reported recently.20±22 Option B: a disconnection
based on a 212-type condensation of known dipyrro-
methane 6 with a 1,9-disubstituted dipyrromethane synthon
of type 7, such as the corresponding dicarbinol. Such
dicarbinol is accessible by reduction of the corresponding
1-benzoyl-5-phenyl-9-formyl-dipyrromethane, itself per-
ceivably a product of a sequential formylation and benzoyl-
ation of known 5-phenyl-dipyrromethane 8.18,23,24
The stepwise syntheses of tetraarylporphyrins carrying four
different aryl groups serve as precedent cases for such
condensations. The condensation conditions leading to a
minimal amount of `scrambling' of the meso-aryl groups
for these and related condensations were investigated in
detail by Lindsey and co-workers, and served as a starting
point in the search for the reaction conditions best suited for
the condensations at hand.25,26
We present here the results of our investigation to synthe-
size 5,10-DPP )3) using 311 and 212 approaches. We also
report on some notable spectroscopic properties of this
novel compound and its zinc)II) and nickel)II) complexes.
2. Results and discussion
2.1. 311 Synthesis of 5,10-diphenylporphyrin $3)
Scheme 2. Reaction conditions: )i) DMF, BzCl; )ii) pyridine; )iii) HgO,
HBF4; )iv) EtMgBr, BzCl; )v) )1) NaBH4, )2) aq. NH4Cl; )vi) )1) TFA, )2)
DDQ; )vii) Zn)OAc)2 or Ni)OAc)2.
Following the retrosynthetic analysis detailed above, we
sought a 311 route for the synthesis of 5,10-DPP
)Scheme 1). Condensation of benzaldehyde )10) with excess
methyl cyanomalonate produces pyrrole derivative 14.
Subsequent Vilsmeyer±Haack formylation followed by
deprotection produces 2,5-pyrrole bisaldehyde 12.35,36
Condensation of 12 with tripyrrane 4 under typical
MacDonald conditions )HBr/acetic acid catalysis), followed
by DDQ oxidation, resulted in the formation of small
amounts ),5%) of porphyrinic materials. ESI-MS of this
material analyzed it to be a mixture of di- )m/zˆ463 for
MH1), tri- )m/zˆ539 for MH1), and tetraphenylporphyrins
)m/zˆ615 for MH1). Evidently, substantial scrambling of
the building blocks had taken place under the harshly acidic
conditions. As either milder acids failed to bring the
bisaldehyde to reaction or other condensation/oxidation
protocols also resulted in the formation of low yields of
product mixtures,20,29±33 this 311 pathway was abandoned
and an alternative pathway sought.
pyrrole )9) provides 5-phenyldipyrromethane
8 and
diphenyltripyrrane 4 which can be separated by sub-
limation.17,27,28 Bisaldehyde 12 is available in 19% overall
yield from pyrrole 9:20,29±33 Vilsmeyer±Haak formylation of
pyrrole,34 followed by Knoevenagel condensation with
Condensation of biscarbinol 11 with tripyrrane 4 was antici-
pated to be possible under milder acid catalysis. Biscarbinol
11 is formally available by reduction of bisaldehyde 12 or,
more conveniently, in a one-step procedure from pyrrole
and formaldehyde under basic conditions.22 Condensation
of 11 with tripyrrane 4 in dry CH2Cl2 using either BF3´OEt2
or TFAas catalyst, followed by DDQ oxidation and
chromatographic work-up, resulted in the formation of a
small ),5%) fraction of porphyrins. ESI-MS proved this
fraction again to be a mixture of di-, tri- and tetraphenyl-
porphyrins. However, as judged by the 1H NMR of the crude
mixture, 5,10-DPP was the main product )vide infra).
Scrambling was also observed using the `low scrambling
conditions' )i.e. CH3CN, TFA, 08C) described by Lindsey
Scheme 1. Reaction conditions: )i) TFA, room temperature; )ii) )1) DMF,
POCl3, )2) aq. NaHCO3; )iii) CH2O, H2O, acetone K2CO3, 08C; )iv) )1)
BF3´Et2O, 08C, )2) DDQ; )v) )1) NCCH2COOEt, NHEt2; )vi) )1) DMF,
POCl3, )2) aq. NaOH, )3) aq. H2SO4; )vii) )1) HBr/HOAc, )2) DDQ.

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R. P. BrinÄas, C. Bruckner / Tetrahedron 58 +2002) 4375±4381
4377
The type of acid used and the particular reaction conditions
were demonstrated to have a profound effect on the outcome
of related condensation reactions.26,37±40 Thus, a thorough
screening of different reaction conditions may eventually
lead to a more successful 311 synthesis of the target
molecule.
2.2. 212 Synthesis of 5,10-diphenylporphyrin $3)
The key intermediate in the 212 routes toward the target
porphyrin is benzoylformyl-dipyrromethane 18 )Scheme 2).
We found that known monoformyl-5-phenyl-dipyrro-
methane 15, available from dipyrromethane 8 in 57%
yield adopting established methods,41 can be benzoylated
in pyridine using 3 equiv. of the 2-phenyl-1,3-benzoxa-
thiolium tetra¯uoro-borate salt )16) as the benzoylating
agent.3,42±44 Masked benzoylformyldipyrromethane 17 was
then deprotected using HgO/HBF4,45 affording key inter-
mediate 18 in 66% yield from dipyrromethane 15. Alternate
benzoylation methods are available.46,47
Figure 2. )A) )Ð) UV±vis spectrum of 5,10-DPP )3) in CHCl3/trace of
Et3N; )- - -) UV±vis spectrum of 3 in CHCl3/1% TFA; )B) uncorrected
¯uorescence emission spectrum of 3 in CHCl3, lexcitationˆ406 nm.
Following established procedures,4,47 dicarbonyl 18 was
reduced with NaBH4 to the corresponding dicarbinol-
dipyrromethane 19. Due to its high reactivity and low
stability, the dicarbinol was generally not isolated and puri-
®ed but immediately condensed under acid catalysis with
known dipyrromethane 67,17,41 at low scrambling conditions
)CH3CN, 2.5 mM reactant concentrations, 30 mM TFA,
258C, 10 min).4 Oxidation with DDQ followed by column
chromatography and recrystallization afforded 5,10-DPP 3
in 10±20% yield in analytical purity. Crystallization
experiments with the goal of obtaining crystals for X-ray
diffractometry studies resulted only in the formation of
unsuitably thin needles. ESI mass spectrometry of the
recrystallized product indicated the absence of tri- or tetra-
phenylporphyrin. Conversion of free base 3 to the corre-
sponding Ni)II)- )3-Ni) and Zn)II)-complexes )3-Zn) using
standard metal insertion protocols proceeded in near-
quantitative yields.
Figure 3. )A) UV±Vis spectrum of 5,10-DPPZn )3-Zn) in CHCl3;
)B) uncorrected ¯uorescence emission spectrum of 3-Zn in CHCl3,
lexcitationˆ411 nm.
and co-workers for related 212 condensation.25 This may
indicate the larger susceptibility of tripyrranes to acid-
catalyzed scrambling as compared to that of dipyrranes
for which the conditions were optimized. Separation of
the observed porphyrinic mixture by preparative thin layer
chromatography is challenging and impractical at prepara-
tive useful scales. As a result, we abandoned the 311 routes
all together and focused on the development of 212 routes
toward a practical synthesis of 5,10-DPP.
2.3. UV±Vis and ¯uorescence spectroscopic properties of
5,10-diphenylporphyrin $3) and its metal complexes
As expected, the UV±vis spectrum of 3 is porphyrin-like
1
Figure 4. H NMR spectrum )400 MHz, CDCl3, 258C) of 5,10-DPP )3).

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R. P. BrinÄas, C. Bruckner / Tetrahedron 58 +2002) 4375±4381
4378
Figure 5. Comparison of the 13C NMR spectra )100 MHz, CDCl3, 258C) spectra of 3 )A) and 3-Zn )B).
with a Soret band at 406 nm and four Q bands )502, 534,
576, 630 nm) )Fig. 2)A)). Surprisingly, however, the
spectrum is a phyllo-type spectrum, i.e. the intensity of
the Q-bands follows the order I.III.II.IV.48
porphyrins.50 In contrast, Edwards and co-workers reported
in a recent contribution that the carbon NMR spectrum of
free base 5,15-DPP is not broadened.51 They attributed this
effect to a faster tautomeric NH exchange rate promoted by
the lower symmetry of DPP as compared to that of TPP
)medium rate of tautomeric exchange rateÐline broaden-
ing). Following their arguments )which we cannot agree
with), 5,10-DPP 3 of even lower symmetry than 5,15-DPP
ought to display a non-broadened 13C NMR. This, however,
is clearly not observed. Thus, the observed line broadening
effect in free base porphyrins still awaits full explanation.
The ¯uorescence spectrum of 3 )Fig. 2)B)) displays
emission bands at 634 and 698 nm. Comparable emission
wavelengths but with reversed intensity ratios are observed
for 5,15-DPP and TPP.49 The electronic spectra for the
¯uorescent Zn-complex 3-Zn )Fig. 3) and )non-¯uorescent)
3-Ni are as expected.
1
Fig. 6 shows the assignments of H NMR and 13C NMR
2.4. 1H and 13C NMR spectroscopic properties of 5,10-
diphenylporphyrin 3 and its metal complexes
signals for 3-Zn. These were determined using 2D NMR
experiments: HETCOR, HMBC, and NOE. The tertiary
meso-carbon )105.1 ppm) was unambiguously identi®ed
by HETCOR while the quaternary meso-carbon
)120.9 ppm) was assigned using HMBC through its two-
bond coupling with the ortho-carbon of the phenyl ring
)134.6 ppm). The assignments for the two singlet b-protons
)9.01 and 9.34 ppm) were veri®ed by NOE experiment.
Irradiation at 9.34 ppm )b-H) exhibited a through-space
The 1H NMR spectrum of 3 is shown in Fig. 4. Most diag-
nostic for the presence of meso-protons in 3 is the singlet at
10.25 ppm )cf. singlet at 10.3 ppm in 5,15-DPP). The 5,10-
disubstitution pattern of 3 can be deduced from the resulting
)idealized) point group C2v, mandating two singlets )2H
each), and two doublets )also 2H each) for the b-protons
)region 9±9.5 ppm). 5,15-DPP 2 of higher point group D2h,
on the other hand, displays only two doublets )4H each).
The remaining signals can be assigned to the o-protons
)8.3 ppm), and m- and p-protons )7.85 ppm) of the two
equivalent phenyl groups. The highly shielded pyrrolic
NH protons are observed at 23.34 ppm.
The 13C NMR spectrum of free base 5,10-diphenyl-
porphyrin 3 is shown in Fig. 5)A). Remarkably, of the 14
non-equivalent carbons, only six provide well-de®ned
signals. All other signals are severely broadened even
when recording 10k scans using long )2.5 s) delay times.
The spectrum of the diamagnetic metal complex 3-Zn is
shown in Fig. 5)B). In contrast to the free base porphyrin
spectrum, 12 sharp signals are observable, even using
relatively fast scans )1.0 s delay time). This severe line
broadening, especially for the a-pyrrolic carbon signals
)around 149±150 ppm), is due to either extremely long
relaxation times or NH-tautomerism effects. This broaden-
ing was observed before in free base TPP, among other
Figure 6. Assignment of 1H and 13C NMR signals )CDCl3, 258C) in 3-Zn as
determined by 2D NMR techniques.

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R. P. BrinÄas, C. Bruckner / Tetrahedron 58 +2002) 4375±4381
4379
coupling with the peak at 10.14 ppm )meso-carbon) while
irradiation at 8.24 ppm )ortho-carbon of phenyl substituent)
gave a through-space coupling with the peak at around
9.01 ppm )b-H). The a-carbons, however, were not
resolved enough to assign them to particular a-positions
in the macrocycle.
3.1.2.
1-[2-$2-Phenyl-1,3-benzoxathiolyl)]-5-phenyl-9-
formyldipyrromethane $17). 1-Formyl-5-phenydipyrro-
methane 15 )50 mg, 0.20 mmol) was dissolved in a mixture
of pyridine )0.16 mL) and acetonitrile )5 mL). 2-Phenyl-
1,3-benzoxathiolium tetra¯uoroborate salt )60 mg,
0.60 mmol) was added to the solution.42 After 1 h at room
temperature, H2O )50 mL) was added and the reaction
mixture was extracted with CHCl3 )3£50 mL). The
combined organic layers were washed with 5% aq. NaOH,
H2O and dried )Na2CO3). The solvent was evaporated under
vacuum to produce a red solid in quantitative yield. The
product was found suf®ciently pure to be used in the next
In summary, 5,10-DPP 3 can be synthesized using a 311
methodology. However, due to the formation of a number of
hard to separate scrambling products, this method proved to
be impractical. A2 12 strategy produced pure product in
moderate yields. The NMR, UV±vis and ¯uorescent
spectroscopic properties of 5,10-DPP were distinctly
different from those of the isomeric 5,15-DPP. This obser-
vation highlights the effects meso-substituents have on the
electronic properties of porphyrins.52 It is hoped that this
contribution will pave the path toward the synthesis of
5,10-DPP derivatives for applications which take advantage
of the orthogonal arrangement of the two phenyl
substituents.
1
step without further puri®cation )see procedure below). H
NMR )400 MHz, CDCl3): d 9.70±9.90 )m, 1H), 9.24 )s,
1H), 8.98±8.87 )m, 1H), 7.69 )d, Jˆ7.7 Hz, 2H), 7.40±
7.30 )m, 7H), 7.10±6.80 )m, 5H), 6.13 )m, 1H), 5.80±5.90
)m, 2H), 5.54 )s, 1H); 13C NMR )CDCl3): d 178.7, 154.0,
142.3, 142.0, 140.0, 133.4, 132.4, 131.1, 128.9, 128.6,
128.4, 127.8, 127.5, 126.5, 126.2, 125.9, 122.8, 121.8,
112.0, 110.9, 108.2, 98.4; IR )KBr) nmax: 1638 )CvO)
cm21. LR-MS )APCI1) m/z 463 [MH1]; HRMS-FAB m/z
calcd )found) for C29H23N2O2S1: 463.1480 )463.1496).
3. Experimental
3.1.3. 1-Benzoyl-5-phenyl-9-formylphenyldipyrromethane
$18)Ðtwo-step, one-pot procedure from 1-formyl-5-
phenyl-dipyrromethane $15). 2-Phenyl-1,3-benzoxa-
thiolium tetra¯uoroborate )0.80 g, 2.7 mmol) was added
under stirring into a solution of 1-formyl-5-phenyldipyrro-
methane 15 )0.22 g, 0.9 mmol) and pyridine )0.22 mL,
2.7 mmol) in dry acetonitrile )20 mL). After 1 h at room
temperature, a mixture of HgO )0.58 g, 2.7 mmol), 48%
aq. HBF4 )1 mL), and DMSO )20 mL) were added. The
stirred reaction mixture was warmed to 608C for 1 h. TLC
monitoring of the reaction was performed using aliquots
treated with aq. KI. Upon the disappearance of starting
material, the mixture was treated with 10% aq. KI )6 mL)
and extracted with CHCl3 )3£50 mL). The organic layers
were collected, washed with 10% aq. KI )2£20 mL), water
)2£20 mL), 5% aq. NaOH )2£20 mL), and then water
again, and dried )Na2SO4). The crude product was concen-
trated and separated by column chromatography )silica gel,
CHCl3/5±10% ethyl acetate). The second fraction was
collected and the solvent was evaporated under vacuum to
afford 18 as a lightly colored foamy solid in 66% yield
)0.21 g). The product is susceptible to slow decomposition
at room temperature. Rfˆ0.61 )silica gel±CH2Cl2/20%
3.1. Materials and instrumentation
CH2Cl2, THF, and pyrrole were dried over and distilled
from CaH2, Na/benzophenone ketyl, and KOH, respec-
tively. All other solvents and reagents were used as
received. The alumina used was Selecto Scienti®c Alumina
B, Super I, 63±150 mm. The ¯ash column silica gel used
was Geduran Silica Gel 60, 35±75 mm, the analytical TLC
plates were Silicycle ultra pure silica gel 60, 250 mm, with
F-254 indicator. 1H and 13C NMR spectra were recorded on
a Bruker DRX400. UV±vis spectra were recorded on Cary
50 and ¯uorescence spectra on a Cary Eclipse spectro-
photometer. IR spectra were measured on a Jasco 410
FT-IR. Elemental analysis of compound 3 was provided
by Numega Resonance Labs Inc., San Diego, CA, high
resolution mass spectra were obtained by the University of
Notre Dame, Chem. Dept. mass spectrometry facility )B.
Boggess).
3.1.1. 1-Formyl-5-phenyldipyrromethane $15). Benzoyl
chloride )1.7 mL, 14 mmol) was added to a cooled mixture
of DMF )2.8 mL, 36 mmol) and 5-phenyl-dipyrromethane 8
)2.0 g, 9.0 mmol) under an atmosphere of dry N2. The
mixture was stirred at 08C for 2 h and then another 2 h at
room temperature. The reaction mixture was quenched by
addition of Na2CO3 )2.0 g) dissolved in 50% aq. EtOH
)150 mL). The resulting solution was extracted with
CH2Cl2 )2£100 mL). The organic phase was dried
)Na2SO4) and evaporated to dryness under vacuum. The
residue was separated using ¯ash column chromatography
)silica gel, CH2Cl2/10% ethyl acetate). The ®rst fraction
contained the desired product )Rfˆ0.73, silica gel±
CH2Cl2/20% EtOAc). Evaporation of the solvent produced
15 in 57% yield )1.3 g) as a tan solid. Spectroscopic and
analytical data were comparable to those described before.17
Asecond fraction eluting from the column was identi®ed to
be the 1,9-bisformyl-5-phenyldipyrrane )Rfˆ0.30, silica
gel±CH2Cl2/20% EtOAc).17
1
EtOAc); H NMR )400 MHz, CDCl3): d 11.34±11.26 )m,
2H), 9.17 )s, 1H), 7.83±7.80 )m, 2H), 7.60±7.33 )m, 8H),
6.81 )m, 1H), 6.70 )m, 1H) 6.10±6.00 )m, 2H), 5.70 )s, 1H);
13C NMR )CDCl3): d 184.6, 179.0, 171.2, 142.5, 140.8,
139.8, 138.0, 132.6, 131.8, 131.0, 129.6, 128.9, 128.7,
128.1, 127.5, 122.6, 120.8, 111.8, 111.3, 44.7; IR )KBr)
n
max: 1643 )CvO, aldehyde), 1609 )CvO, ketone) cm21
;
LR-MS )APCI1): m/z 355 [MH1]; HRMS-FAB m/z calcd
)found) for C23H19N2O21: 355.1447 )355.1421).
3.1.4. 5,10-Diphenylporphyrin $3). To a stirred solution of
diacyldipyrromethane 18 )50 mg, 0.14 mmol) in THF/
methanol )10:1, 6 mL) was added, under N2, NaBH4
)0.11 g, 2.8 mmol) in small portions ),every 2 min).
After 40 min at room temperature, the reaction mixture
was poured into a mixture of saturated aq. NH4Cl and
CHCl3 )1:1, 20 mL). The organic phase was isolated,

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R. P. BrinÄas, C. Bruckner / Tetrahedron 58 +2002) 4375±4381
4380
washed with water )2£) and dried )Na2CO3). The solvent
was evaporated under vacuum. The residue was dissolved in
acetonitrile )56 mL), dipyrromethane )21 mg, 0.14 mmol)
was added. The resulting mixture was stirred for 5 min at
room temperature, TFA)0.13 mL, 1.7 mmol) was added,
and the mixture was stirred for 10 min. DDQ )0.10 g,
0.44 mmol) in toluene ),10 mL) was then added. After
mixing for 1 h at room temperature, triethylamine
)0.24 mL, 1.7 mmol) was added. The crude mixture was
®ltered through a pad of alumina. CHCl3 ),50 mL) was
used to extract the ®lter cake. The porphyrin-containing
fractions )as assessed by UV±vis) were concentrated and
passed through a plug of silica )eluted with CHCl3). The
DPP fractions were combined. Evaporation of the solvent
in vacuo afforded up to 20% yield of microcrystalline purple
product )13 mg). An experiment using 0.30 g )0.85 mmol)
of dipyrrane 18 gave 37 mg )9.5 % yield) of 5,10-DPP 3.
Rfˆ0.58 )silica gel±CH2Cl2/50% pet. ether 30±60). UV±vis
)CDCl3) lmax )log 1): 406 )5.6), 502 )4.2), 534 )3.4), 576
)3.7), 630 )2.9) nm; UV±vis )CDCl31drops of TFA) lmax
d 143.0 142.9, 142.6, 142.5, 141.2, 133.8, 132.5, 132.0,
131.9, 127.7, 126.8, 119.1, 104.3; LR-MS )APCI1):
m/zˆ518.6 [M1], expected isotope cluster for C32H22N4Ni
is observed; HRMS-FAB m/z calcd )found) for C32H22N4Ni:
518.1041 )518.1019).
Acknowledgements
The work was supported by the UConn Research Founda-
tion. We are indebted to Dr Martha Morton at the NMR
facility at UConn for her assistance.
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and heated to re¯ux for about 10 min. To the mixture was
added water )10 mL) and the organic layer was isolated and
dried )Na2SO4). The solvent was evaporated by vacuum to
provide a red violet residue. This residue was recrystallized
from CHCl3/pentane to yield purple microcrystals of 3-Zn.
Rfˆ0.46 )silica gel±CH2Cl2/50% pet. ether 30±60); UV±
vis )CDCl3) lmax )log 1): 411 )5.4), 539 )4.1) nm; 1H NMR
)CDCl3): d 10.14 )s, 2H), 9.45±9.32 )m, 4H), 9.09 )d,
Jˆ4.3 Hz, 2H), 9.01 )s, 2H), 8.30±8.17 )m, 4H), 7.85±
7.70 )m, 6H); 13C NMR )CDCl3): d 149.7, 149.6, 142.9,
134.6, 132.5, 132.0, 131.8, 131.6, 127.5, 126.5, 120.9,
105.1; LR-MS )APCI1): m/z 524 [M1], expected isotope
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