Synthesis and optical properties of tetrapyrazinoporphyrazines containing asymmetrical alkyl chains and t-butylphenyl groups

Article abstract of DOI:10.1142/S1088424610002355

Tetrapyrazinoporphyrazine magnesium complexes with four long alkyl groups and four 4-tert-butyl phenyl groups at the peripheral positions were synthesized from 2,3-dicyano-5-(4-tert-butylphenyl)-6-alkyl pyrazine derivatives using freshly prepared solutions of magnesium butoxide in n-butanol. The corresponding metal-free derivatives were obtained through treatment with p-toluenesulfonic acid. The resulting chromophores contained alkyl chains substituted at their peripheries and showed good solubility in organic solvents. The fluorescence of the tetrapyrazinoporphyrazine magnesium complexes was greatly influenced by the intermolecular aggregation. Q band spectra of the porphyrazine magnesium complexes in DMF exhibited the characteristic patterns of the monomeric species, with fluorescence maxima at 653-658 nm. These new compounds were characterized using UV-visible spectroscopy, MALDI-TOF-MS and ¹H NMR spectroscopy.

Full text of DOI:10.1142/S1088424610002355

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2010; 14: 531–539
DOI: 10.1142/S1088424610002355
Published at http://www.worldscinet.com/jpp/
Synthesis and optical properties of
tetrapyrazinoporphyrazines containing asymmetrical
alkyl chains and t-butylphenyl groups
Chun Keun Jang, Song Hak Kim and Jae-Yun Jaung*
Department of Fiber and Polymer Engineering, Hanyang University 17 Haengdang-dong, Seongdong-gu,
Seoul 133791, Korea
Received 15 December 2009
Accepted 24 March 2010
ABSTRACT: Tetrapyrazinoporphyrazine magnesium complexes with four long alkyl groups and four
4-tert-butyl phenyl groups at the peripheral positions were synthesized from 2,3-dicyano-5-(4-tert-
butylphenyl)-6-alkyl pyrazine derivatives using freshly prepared solutions of magnesium butoxide in
n-butanol. The corresponding metal-free derivatives were obtained through treatment with p-toluene-
sulfonic acid. The resulting chromophores contained alkyl chains substituted at their peripheries
and showed good solubility in organic solvents. The fluorescence of the tetrapyrazinoporphyrazine
magnesium complexes was greatly influenced by the intermolecular aggregation. Q band spectra of the
porphyrazine magnesium complexes in DMF exhibited the characteristic patterns of the monomeric
species, with fluorescence maxima at 653–658 nm. These new compounds were characterized using
UV-visible spectroscopy, MALDI-TOF-MS and 1H NMR spectroscopy.
KEYWORDS: 2,3-dicyanopyrazine, tetrapyrazinoporphyrazine, tert-butyl group, fluorescence, spectral
properties.
tetravalent transition metal as the core of the macrocycle,
INTRODUCTION
along with a coordination compound that contains an
Since Braun and Tscherniac first discovered phthalo-
axial ligand from a central metal [3]. The second method
cyanine in 1907, many technological applications, such as
involves the introduction of various peripheral substitu-
optical disks, laser dyes, liquid crystals, electro-catalysts,
ents into the macrocycle [4, 5]. Bulky substituents steri-
and chemical sensors, have been investigated for these
compounds [1, 2].
cally reduce the intermolecular π-π interactions, which
minimizes the formation of aggregates, thereby improv-
Unsubstituted metallophthalocyanines have intense
ing solubility [6].
colors but are generally insoluble in organic solvents or
Like phthalocyanine, tetrapyrazinoprophyrazine is
water, thereby limiting their use to just a few fields. The
also a macrocycle ring system. It is a tetramerized struc-
insolubility of the metal phthalocyanine derivatives is
ture of 2,3-dicyanopyrazine derivatives, which can be
caused by molecular stacking, which is created by strong
obtained in high yield by condensation of diaminoma-
intermolecular interactions between the macrocycles
leonitrile (DAMN) with various kinds of 1,2-diones.
in the phthalocyanine molecules. However, two meth-
Similar to phthalocyanines, pyrazinoporphyrazines usu-
ods can be used to improve the solubility in almost all
ally have Q bands under red region, and thus have similar
solvents. The first method involves the use of a tri- or
areas of practical application. In addition, they have the
same tendency of π-π interaction with macrocycles as
phthalocyanines, so the same methods were researched
to reduce aggregation.
SPP full
Student member in good standing
Segregation between the rigid aromatic moieties and the
flexible alkyl chains generally occurs for phthalocyanine
*Correspondence to: Jae-Yun Jaung, email: jjy1004@hanyang.
ac.kr, tel: +82 2-2220-0492, fax: +82 2-2220-4092
Copyright © 2010 World Scientific Publishing Company

532
C.K. Jang et al.
macrocycles substituted with long alkyl chains, causing
the formation of columnar mesophases. Therefore, the
stability of phthalocyanine can be improved through
the introduction of an adequate functional substituent at
the peripheral positions of the phthalocyanine ring, which
causes a substantial disruption in the strong interaction
between the macrocycle rings. The increased stability
expands the potential applications of phthalocyanines
[7, 8].
sodium sulfate. The mixture was concentrated under a
reduced pressure to form 2a (yellow liquid, 94%). H
1
NMR (300 MHz, CDCl3): δ, ppm 1.08 (t, J = 6.0 Hz,
-CH3, 3H), 1.36 (s, -t-Bu, 9H), 2.02–2.35 (m, -CH2-, 2H),
5.14 (t, J = 7.5 Hz, Br-C-H, 1H), 7.51 (d, J = 9.0 Hz,
Ar-H, 2H), 7.99 (d, J = 9.0 Hz, Ar-H, 2H). 13C NMR (300
MHz, CDCl3): δ, ppm 11.73, 26.34, 31.16, 34.35, 54.51,
120.89, 124.10, 127.88, 152.53, 190.52. Anal. calcd. for
C14H19BrO; C, 59.37; H, 6.76; Br, 28.21. Found C, 58.55;
1
On the other hand, the aggregation behavior of phthal-
ocyanines is important because it decreases solubility and
makes purification of the compound difficult. Further-
more, aggregation shortens the triplet-state lifetime and
reduces the singlet oxygen quantum yield. Aggregation
can be controlled using various techniques. For example,
aggregation can be suppressed through the introduction
of long alkyl chains or bulky substituents at the periphery
of the phthalocyanine ring [9, 10]. Disaggregation behav-
ior is exhibited in the basic condition because of the
anionic effect, such as binding or deprotonation with the
macrocycle ring. Phthalocyanines can be used as anion
chemical sensors because of their optical changes.
The synthesis of functional dye materials based on
2,3-dicyanopyrazine chromophores was investigated, and
the physical properties were correlated with their
structures [11]. In this study, metal and metal-free
tetrapyrazinoporphyrazines derived from 2,3-dicyano-5-
(4-tert-butylphenyl)-6-alkyl pyrazine derivatives were
designed and synthesized. This study focused on the
change in the optical properties caused by the structure
of the peripheral substituent, and the external conditions
around the macrocycle.
H, 6.69. 2b (yellow liquid, 90%). H NMR (300 MHz,
CDCl3): δ, ppm 0.89 (t, J = 6.0 Hz, -CH3, 3H), 1.27 (br
s, -CH2-, 16H), 1.36 (s, -t-Bu, 9H), 2.02–2.31 (m, -CH2-,
2H), 5.14 (t, J = 7.5 Hz, Br-C-H, 1H), 7.51 (d, J = 9.0
Hz, Ar-H, 2H), 7.98 (d, J = 9.0 Hz, Ar-H, 2H). 13C NMR
(300 MHz, CDCl3): δ, ppm 14.12, 22.72, 25.31, 28.64,
29.69, 31.30, 31.9, 34.23, 54.35, 124.90, 128.40, 133.61,
155.68, 191.20. Anal. calcd. for C22H35BrO; C, 66.82; H,
8.92; Br, 20.21. Found C, 66.81; H, 8.81. 2c (yellow liq-
uid, 92%). 1H NMR (300 MHz, CDCl3): δ, ppm 0.88 (t,
J = 6.0 Hz, -CH3, 3H), 1.26 (br s, -CH2-, 16H), 1.34 (s,
-t-Bu, 9H), 2.02–2.28 (m, -CH2-, 2H), 5.14 (t, J = 7.5 Hz,
Br-C-H, 1H), 7.50 (d, J = 9.0 Hz, Ar-H, 2H), 7.97 (d, J =
9.0 Hz, Ar-H, 2H). 13C NMR (300 MHz, CDCl3): δ, ppm
14.12, 22.72, 25.31, 28.65, 29.69, 31.30, 31.9, 33.02,
34.23, 54.35, 124.90, 128.40, 133.61, 155.70, 191.20.
Anal. calcd. for C24H39BrO; C, 68.07; H, 9.28; Br, 18.87;
O, 3.78. Found C, 68.24; H, 9.16.
Typical procedure to synthesize 3a. Brominated pre-
cursor 2a (56.64 g, 0.2 mol) and potassium acetate (68.7 g,
0.7 mol) were refluxed in 200 mL of acetone. The solu-
tion was filtered and the solvent was removed in vacuo.
The acetoxy group containing precursor was hydrolized
in 60 mL of 10% NaOH in a methanol solution. After
hydrolysis, the solution was filtered with methanol and
extracted with 200 mL ethyl acetate and 250 mL of
water. The organic layer was dried with sodium sulfate
and evaporated in vacuo. The product was crystallized
in n-hexane, and the resulting white crystal was filtered.
EXPERIMENTAL
General
1
3a (white crystal, 30%). H NMR (300 MHz, CDCl3):
Flash chromatography was performed using a Merck-
1
δ, ppm 0.90 (t, J = 6.0 Hz, -CH3, 3H), 1.35 (s, -t-Bu,
9H), 1.67 (m, -CH2-, 2H), 3.73 (s, -OH, 1H), 4.95 (s,
-O-CH, 1H), 7.51 (d, J = 9.0 Hz, Ar-H, 2H), 7.86 (d, J =
9.0 Hz, Ar-H, 2H). 13C NMR (300 MHz, CDCl3): δ, ppm
9.11, 24.37, 31.39, 34.27, 86.60, 124.89, 128.48, 131.13,
155.76, 197.02. Anal. calcd. for C14H20O2; C, 76.33;
H, 9.15; O, 14.52. Found C, 75.78; H, 9.34. 3b (white
crystal, 28%). 1H NMR (300 MHz, CDCl3): δ, ppm 0.87
(t, J = 6.0 Hz, -CH3, 3H), 1.24 (br s, -CH2-, 14H), 1.35
(s, -t-Bu, 9H), 1.52 (m, -CH2-, 2H), 1.86 (t, J = 6.0 Hz,
-O-C-CH2, 2H), 3.73 (s, -OH, 1H), 5.05 (s, -O-CH, 1H),
7.51 (d, J = 9.0 Hz, Ar-H, 2H), 7.86 (d, J = 9.0 Hz, Ar-H,
2H). 13C NMR (300 MHz, CDCl3): δ, ppm 14.12, 22.72,
24.81, 29.33, 29.61, 31.31, 31.92, 34.20, 84.40, 124.96,
128.40, 131.11, 155.76, 197.0. Anal. calcd. for C22H36O2;
C, 79.46; H, 10.91; O, 9.62. Found C, 79.16; H, 10.86.
EM Type 60 (230–400 mesh) silica gel (flash). The H
NMR spectra were recorded using a VARIAN Uni-
tyInova 300 MHz FT-NMR spectrometer. UV-visible and
fluorescence spectra were measured using Scinco S-4100
and Shimadzu RF-5301PC spectrophotometers, respec-
tively. The MALDI-TOF-MS spectra were obtained
using a Waters Limited MALDI-TOF spectrometer with
dithranol as the matrix. The reagents and solvents used
in the synthesis were all synthetic grade, and were used
as received. The chemicals used for the spectroscopic
analysis were all analytical reagent grade.
Typical procedure to synthesize 2a. Br2 (40.0 g,
0.25 mol) was added dropwise to a solution of 4-(tert-
butyl)butan-1-one derivative 1 (50.0 g, 0.25 mol) in 150
mL of CHCl3 with stirring at 10 °C. After 2 h at room
temperature, the mixture was diluted with ice water and
extracted with 300 mL of dichloromethane. The organic
layer was washed with water and dried with anhydrous
1
3c (white crystal, 31%). H NMR (300 MHz, CDCl3):
δ, ppm 0.87 (t, J = 6.0 Hz, -CH3, 3H), 1.24 (br s, -CH2-,
Copyright © 2010 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2010; 14: 532–539

SyntheSIS anD OPtICal PrOPertIeS Of tetraPyrazInOPOrPhyrazIneS
533
18H), 1.35 (s, -t-Bu, 9H), 1.52 (m, -CH2-, 2H), 1.86 (t,
129.94, 130.27, 131.31, 151.31, 158.15, 162.34. Anal.
calcd. for C18H18N4; C, 74.46; H, 6.25; N, 19.30. Found
C, 73.38; H, 6.15; N, 18.84. 5b (yellow solid, 36%). H
J = 6.0 Hz, -O-C-CH2, 2H), 3.73 (s, -OH, 1H), 5.05 (dd,
J1 = 6.0 Hz, J2 = 3.0 Hz, -O-CH, 1H), 7.51 (d, J = 9.0
Hz, Ar-H, 2H), 7.86 (d, J = 9.0 Hz, Ar-H, 2H). 13C NMR
(300 MHz, CDCl3): δ, ppm 14.12, 22.72, 24.81, 29.34,
29.60, 31.31, 31.60, 31.92, 34.20, 84.40, 124.95, 128.40,
131.11, 155.76, 197.0. Anal. calcd. for C24H40O2; C,
79.94; H, 11.18; O, 8.87. Found C, 79.74; H, 11.02.
Typical procedure to synthesize 4a. 1-(4-tert-
butylphenyl)-2-hydroxybutan-1-one 3a (18.06 g, 82
mmol) was added to a mixture of CuSO4·5H2O (42.5 g,
0.17 mol) in 42 mL of pyridine and 16 mL of water. The
mixturewasrefluxedandmonitoredusingthin-layerchro-
matography (TLC, ethyl acetate/n-hexane = 1/5). Then,
the mixture was poured into 30 mL of a 10% HCl aque-
ous solution and 100 mL ice water and was vigorously
stirred. After filtration, the filtrate was extracted with
200 mL ethyl acetate. The organic layer was dried with
sodium sulfate, and the solvent was removed in vacuo.
4a (yellow liquid, 75%). 1H NMR (300 MHz, CDCl3): δ,
ppm 0.88 (t, J = 6.0 Hz, -CH3, 3H), 1.34 (s, -t-Bu, 9H),
2.01 (s, -CH2-, 2H), 7.51 (d, J = 9.0 Hz, Ar-H, 2H), 7.92
(d, J = 9.0 Hz, Ar-H, 2H). 13C NMR (300 MHz, CDCl3):
δ, ppm 8.21, 27.48, 31.32, 34.23, 125.54, 128.41, 129.52,
157.10, 190.49, 197.55. Anal. calcd. for C14H18O2; C,
77.03; H, 8.31; O, 14.66. Found C, 77.08; H, 8.28. 4b
1
NMR (300 MHz, CDCl3): δ, ppm 0.87 (t, J = 6.0 Hz,
-CH3, 3H), 1.24 (br s, -CH2-, 14H), 1.38 (s, -t-Bu, 9H),
1.71–1.81 (m, -CH2-, 2H), 3.07 (t, J = 7.5 Hz, -CH2-,
2H), 7.57 (s, Ar-H, 4H). 13C NMR (300 MHz, CDCl3):
δ, ppm 14.13, 22.76, 29.20, 29.31, 29.67, 31.35, 31.90,
34.24, 34.31, 117.14, 125.48, 125.57, 129.94, 130.10,
133.0, 151.33, 159.12, 161.22. Anal. calcd. for C26H34N4;
C, 77.57; H, 8.51; N, 13.92. Found C, 77.64; H, 8.14;
1
N, 13.89. 5c (yellow solid, 32%). H NMR (300 MHz,
CDCl3): δ, ppm 0.87 (t, J = 6.0 Hz, -CH3, 3H), 1.24 (br
s, -CH2-, 18H), 1.38 (s, -t-Bu, 9H), 1.70–1.80 (m, -CH2-,
2H), 3.05 (t, J = 7.5 Hz, -CH2-, 2H), 7.56 (s, Ar-H, 4H).
13C NMR (300 MHz, CDCl3): δ, ppm 14.13, 22.76, 29.20,
29.31, 29.67, 31.35, 31.90, 34.24, 34.33, 117.10, 125.48,
125.57, 129.94, 130.10, 133.0, 151.33, 159.12, 161.21.
Anal. calcd. for C28H38N4; C, 78.10; H, 8.89; N, 13.01.
Found C, 76.94; H, 8.34; N, 14.08.
Typical procedure to synthesize 6a. A suspension
of Mg turnings (2 g, 0.08 mol), one small iodine crys-
tal, and 150 mL of n-butanol was heated under reflux
for 4 h. Then, the reaction mixture was cooled to room
temperature and dicyanopyrazine 5a (5.9 g, 0.02 mol)
was added. The reaction mixture was quickly reheated
to reflux, After approximately 10 min, the reaction mix-
ture become dark green in color. After 1 h, the mixture
was quenched through the addition of 200 mL of metha-
nol and was filtered, The crude product was dark green
and was purified using column chromatography with a
silica gel as the stationary phase and chloroform/metha-
1
(yellow liquid, 43%). H NMR (300 MHz, CDCl3): δ,
ppm 0.88 (t, J = 6.0 Hz, -CH3, 3H), 1.26 (br s, -CH2-,
14H), 1.34 (s, -t-Bu, 9H), 1.64–1.73 (m, -CH2-, 2H), 2.86
(t, J = 7.5 Hz, -CH2-, 2H), 7.51 (d, J = 9.0 Hz, Ar-H,
2H), 7.92 (d, J = 9.0 Hz, Ar-H, 2H). 13C NMR (300 MHz,
CDCl3): δ, ppm 14.11, 22.72, 24.81, 29.12, 29.30, 29.60,
31.31, 31.94, 34.25, 125.58, 128.48, 129.50, 157.17,
190.54, 197.53. Anal. calcd. for C22H34O2; C, 79.95; H,
10.37; O, 9.68. Found C, 78.74; H, 10.01. 4c (yellow
1
nol (30/1) as the eluant. 6a (dark green solid, 24%). H
NMR (300 MHz, CDCl3): δ, ppm 1.27 (broad s, CH3,
12H), 1.57 (broad s, C(CH3)3, 36H), 3.66 (broad s, CH2,
8H), 7.79 (broad s, Ar-H, 8H), 8.10 (broad s, Ar-H, 8H).
UV-vis (log ε, CHCl3): λ, nm 362 (4.90), 625 (4.52),
725 (4.41). Anal. calcd. for C72H72MgN16: C, 72.93;
H, 6.12; N, 18.90. Found: C, 71.07; H, 6.05; N, 18.74.
MS (MALDI-TOF): m/z 1186.96 (calcd. 1185.75). 6b
1
liquid, 40%). H NMR (300 MHz, CDCl3): δ, ppm 0.87
(t, J = 6.0 Hz, -CH3, 3H), 1.26 (br s, -CH2-, 18H), 1.34
(s, -t-Bu, 9H), 1.64–1.73 (m, -CH2-, 2H), 2.86 (t, J =
7.5 Hz, -CH2-, 2H), 7.51 (d, J = 9.0 Hz, Ar-H, 2H), 7.92
(d, J = 9.0 Hz, Ar-H, 2H). 13C NMR (300 MHz, CDCl3):
δ, ppm 14.11, 22.72, 25.51, 29.12, 29.30, 29.60, 31.31,
31.94, 34.25, 125.58, 128.48, 129.50, 157.18, 190.54,
197.53. Anal. calcd. for C24H38O2; C, 80.39; H, 10.68; O,
8.92. Found C, 80.41; H, 9.98.
1
(dark green solid, 26%). H NMR (300 MHz, CDCl3):
δ, ppm 0.95 (broad s, CH3, 12H), 1.12–1.38 (broad m,
methylene, 56H), 1.35 (broad s, C(CH3)3, 36H), 1.62
(broad s, Py-C-CH2, 8H), 2.05 (broad s, Py-CH2, 8H),
7.80 (broad s, Ar-H, 8 protons), 8.08 (broad s, Ar-H, 8
protons). UV-vis (log ε, CHCl3): λ, nm 361 (4.94), 624
(4.62), 708 (4.55). Anal. calcd. for C104H136MgN16: C,
76.42; H, 8.39; N, 13.71. Found: C, 75.88; H, 8.31; N,
13.64. MS (MALDI-TOF): m/z 1636.5 (calcd. 1634.6).
6c (dark green solid, 20%). 1H NMR (300 MHz, CDCl3):
δ, ppm 0.97 (broad s, CH3, 12H), 1.20–1.57 (broad m,
methylene, 72H), 1.38 (broad s, C(CH3)3, 36H), 1.70
(broad s, Py-C-CH2, 8H), 2.25 (broad s, Py-CH2, 8H),
7.80 (broad s, Ar-H, 8 protons), 8.10 (broad s, Ar-H, 8
protons). UV-vis (log ε, CHCl3): λ, nm 361 (4.96), 625
(4.65), 708 (4.52). Anal. calcd. for C112H152MgN16: C,
77.01; H, 8.77; Mg, 1.39; N, 12.83. Found: C, 76.31; H,
Typical procedure to synthesize 5a. 1-(4-tert-
butylphenyl)butane-1,2-dione 4a (8.3 g, 38 mmol) was
refluxed with 2,3-diaminomaleonitrile (4.09 g, 38 mmol)
in 50 mL of methanol and amount of p-toluenesulfo-
nic acid catalyst for 2 h. The reaction was monitored
using TLC (ethyl acetate/n-hexane = 1/5). The solvent
was removed in vacuo and the crude product was puri-
fied using column chromatography (silica gel, ethyl
acetate/n-hexane = 1/5 as the eluant). 5a (yellow solid,
1
70%). H NMR (300 MHz, CDCl3): δ, ppm 0.87 (t, J =
6.0 Hz, -CH3, 3H), 1.38 (s, -t-Bu, 9H), 2.54 (s, -CH2-,
2H), 7.57 (s, Ar-H, 4H). 13C NMR (300 MHz, CDCl3): δ,
ppm 13.33, 29.01, 31.30, 34.23, 117.11, 125.42, 125.56,
Copyright © 2010 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2010; 14: 533–539

534
C.K. Jang et al.
8.73; N, 11.99. MS (MALDI-TOF): m/z 1747.64 (calcd.
1746.82).
RESULTS AND DISCUSSION
Typical procedure to synthesize 7a. p-toluenesul-
fonic acid (27.5 g, 0.16 mol) was added to a solution of
Mg tetrapyrazinoporphyrazine (6a) (3.7 g, 3.1 mmol) in
THF 100 mL, and the resulting mixture was stirred at
room temperature for 30 min. The solvent was removed
in vacuo, leaving a dark green solid as the crude product,
which was purified using column chromatography with
a silica gel as the stationary phase and chloroform/meth-
anol (30/1) as the eluant. 7a (dark green solid, 50%). 1H
NMR (300 MHz, CDCl3): δ, ppm -1.47 (s, N-H, 2H),
1.51–1.54 (m, C(CH3)3, 36H), 1.69–1.75 (m, CH3, 12H),
1.76–1.79 (m, CH2, 8H), 7.74 (broad s, Ar-H, J = 9.0 Hz,
8H), 8.08 (m, Ar-H, J = 9.0 Hz, 8H). UV-vis (log ε,
CHCl3): λ, nm 345 (4.80), 628 (4.81), 661 (4.97). Anal.
calcd. for C72H74N16: C, 74.33; H, 6.41; N, 19.26. Found:
C, 74.63; H, 6.32; N, 19.08. MS (MALDI-TOF): m/z
1164.84 (calcd. 1163.47). 7b (dark green solid, 44%).
1H NMR (300 MHz, CDCl3): δ, ppm -0.97 (s, N-H, 2H),
0.80–1.02 (m, CH3, 12H), 1.05–1.43 (m, methylene,
56H), 1.50–1.55 (m, C(CH3)3, 36 protons), 2.16–2.40
(m, Py-C-CH2, 8 protons), 3.52–3.70 (m, Py-CH2, 8H),
7.65–7.79 (m, Ar-H, 8 protons), 7.92–8.05 (m, Ar-H,
8 protons). UV-vis (log ε, CHCl3): λ, nm 347 (4.83),
628 (4.84), 661 (4.96). Anal. calcd. for C104H138N16:
C, 77.47; H, 8.63; N, 13.90. Found: C, 77.24; H, 8.70;
N, 13.75. MS (MALDI-TOF): m/z 1613.29 (calcd.
Preparation of Mg and metal-free tetrapyrazinopor-
phyrazine compounds
1-(4-tert-butylphenyl)butan-1-one (1a), 1-(4-tert-
butylphenyl)dodecan-1-one (1b), and 1-(4-tert-bu-
tylphenyl)tetradecan-1-one (1c) were synthesized using
the method described in previous literature [12]. These
4-(tert-butyl)alkylphenone derivatives 1 were treated
with one equivalent of bromine in chloroform at room
temperature to produce an 89–95% yield of α-brominated
4-(tert-butyl)alkyl phenone derivatives (2). The reaction
of α-brominated ketones with an excess (2.8 equiv.)
of anhydrous potassium acetate in acetone afforded
α-acetoxylated 4-(tert-butyl)alkyl phenone [13, 14].
This compound was reacted with 10% methanolic NaOH
under reflux conditions to produce the corresponding
compounds of 1-(4-tert-butylphenyl)-2-hydroxybutan-1-
one (3a), 1-(4-tert-butylphenyl)-2-hydroxydodecan-1-one
(3b), and 1-(4-tert-butylphenyl)-2-hydroxytetradecan-
1-one (3c). α-diketones 4 were obtained through the
oxidation of α-hydroxyketones 3 with copper sulfate in
aqueous pyridine solution. The dicyanopyrazine pre-
cursors 5 were synthesized from the condensation
of α-diketones and 2,3-diaminomaleonitrile (DAMN) in
the presence of a catalytic amount of p-toluenesulfonic
acid in methanol. This reaction route is summarized in
Scheme 1.
1
1612.32). 7c (dark green solid, 38%). H NMR (300
MHz, CDCl3): δ, ppm -0.90 (s, N-H, 2H), 0.82–0.98
(m, CH3, 12H), 1.20–1.45 (m, methylene, 72H), 1.50–
1.65 (m, C(CH3)3, 36H), 2.08–2.20 (m, Py-C-CH2, 8H),
3.60–3.70 (m, Py-CH2, 8H), 7.64–7.80 (m, Ar-H, 8H),
7.98–8.12 (m, Ar-H, 8H). UV-vis (log ε, CHCl3): λ,
nm 341 (4.71), 629 (4.57), 661 (4.61). Anal. calcd.
for C112H154N16: C, 78.00; H, 9.00; N, 13.00. Found:
C, 75.90; H, 9.09; N, 12.65. MS (MALDI-TOF): m/z
1725.07 (calcd. 1724.53).
The final tetrapyrazinoporphyrazine magnesium com-
plexes 6 were successfully synthesized using excess
magnesium butoxide in n-butanol under reflux condi-
tions. If required, these magnesium complexes were eas-
ily demetalated through stirring at room temperature for
30 min in excess amounts of p-toluenesulfonic acid in
THF to produce 7 (in a yield range of 38–50%).
The chemical structures of the complexes are shown in
Scheme 2. The structural assignments were established
i) CH3COOK/acetone
reflux for 12 h
Br2
ii) NaOH 10% methanolic
solution
CHCl3
(CH2)nCH3
(CH2)nCH3
O
O
O
CH2(CH2)nCH3
OH
Br
3
1
2
CuSO4·5H2O
pyridine/water
DAMN
MeOH
NC
NC
N
N
(CH2)nCH3
(CH2)nCH3
O
O
5a: n = 1
5b: n = 9
5c: n = 11
4
Scheme 1. Reaction route of the tetrapyrazinoporphyrazine derivatives
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SyntheSIS anD OPtICal PrOPertIeS Of tetraPyrazInOPOrPhyrazIneS
535
(CH2)nCH3
(CH2)nCH3
N
N
N
N
N
N
N
N
N
H
N
Mg
N
N
N
N
N
N
N
H3Cn(H2C)
H3Cn(H2C)
THF
n-butanol
Mg/I2
N
N
N
N
5
(CH2)nCH3
(CH2)nCH3
H
N
N
p-toluenesulfonic
acid
N
N
N
N
N
N
N
N
N
H3Cn(H2C)
H3Cn(H2C)
6a: n = 1
6b: n = 9
6c: n = 11
7a: n = 1
7b: n = 9
7c: n = 11
Scheme 2. Reaction route of the magnesium and metal-free tetrapyrazinoporphyrazine complexes
for the tetrapyrazinoporphyrazinato magnesium com-
plexes 6 was the relatively broad chemical shift attributed
to the presence of aggregated species.
1
The H NMR analysis of 6 and 7 showed the char-
acteristic signals of both the tert-butyl group (-C(CH3)3,
0.97–1.57 ppm) and the aliphatic methyl group (-CH3,
1.26–1.76 ppm) at an expected ratio of 3:1.
The aromatic protons of 7 appeared downfield
between 7.75 and 8.09 ppm, whereas the chemical shift
of the proton of inner nitrogen was observed from -0.90
to -1.47 ppm, much further downfield than phthalocya-
nine at -3.41 ppm. These downfield shifts were attributed
to the electron-withdrawing effect of the pyrazine ring.
Spectroscopic characterization by UV-vis and fluores-
cence
Fig. 1. 1H NMR spectra of 6c and 7c in CDCl3
Table 1 shows the absorption and fluorescence spec-
tral data of tetrapyrazinoporphyrazines 6 and 7. In chlo-
roform, the absorption maxima in the visible spectra of 6
and 7 appeared between 625–705 nm because of the π-π*
transition that is commonly referred to as the Q band.
The B band (Soret band) was observed as a broad peak
between 341–362 nm. The small broad area around the
Q band region of 6 was attributed to structural mixtures
resulting from their unsymmetrical structure. However,
1
based on MALDI-TOF mass, H NMR, and UV-visible
spectroscopy results.
In the MALDI-TOF MS spectra, tetrapyrazinopor-
phyrazines 6a and 7a displayed a single peak at m/z =
1185.75 (calcd. 1187.0) and 1163.47 (calcd. 1164.8),
respectively, corresponding to [M]+.
Figure 1 shows H NMR spectra of 6c and 7c. Com-
pared to 7, a common feature of the proton NMR spectra
1
Table 1. Absorption and fluorescence spectra of tetrapyrazinoporphyrazines
d
Compound
n
M
λ
max, nma
Fmax, nm
ΦF
Soret band (B band)
Q band
625, 705
624, 708
625, 708
628, 661
628, 661
6a
6b
6c
7a
7b
1
Mg
Mg
Mg
2H
2H
2H
362
361
361
345
347
341
653b
654b
654b
657c
657c
658c
0.63
0.67
0.74
0.39
0.44
0.48
9
11
1
9
7c
11
629, 661
a
b
c
In chloroform. Fluorescence maximum excited by 645 nm in DMF. Fluorescence maximum excited by
628 nm in CHCl3. d Measured by Williams method with Zn phthalocyanine.
Copyright © 2010 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2010; 14: 535–539

536
C.K. Jang et al.
The absorption spectra of the aggregate species exhib-
ited a split Q band at 625 and 705 nm, which caused cou-
pling of the transition moment between a pair (or more)
of chromophores. Mizuguchi et al. reported that the
molecular distortion of titanylphthalocyanine in a solid
state produced a doubly degenerate excited level, causing
split absorption bands [15]. The reduction of the molecu-
lar symmetry from the monomeric state to the dimeric
state resolved the doubly degenerate level of the LUMO
and gave two π-π* transitions which were orthogonal and
on the molecular plane.
Visible absorption spectra of metal-free tetrapyrazi-
noporphyrazines (7) exhibited a well-resolved split-
ting of the Qx/Qy bands at 627–662 nm (in Fig. 4). The
Q band spectra exhibited the characteristic patterns of
a monomeric species with a strong red fluorescence.
The absorption spectra of 6 in DMF did not have split
Qx/Qy bands because of the electronic coupling between
Fig. 2. The effects of the solvent polarity on the absorption
spectra of 6a (2.70 × 10-5 M)
the strange absorption curve observed in the chlorinated
solvent was attributed to the molecular aggregation in
the solution. Figure 2 shows the various changes in the
absorption spectra depending on the solvent in arbitrary
concentrations; the B band absorbances were matched to
compare the Q bands.
Tetrapyrazinoporphyrazinato magnesium complexes
(6) in N,N-dimethylformamide (DMF) showed red fluo-
rescence with small Stoke’s shift values. This indicates
a high energy transformation efficiency for the absorbed
light energy into the fluorescence. The fluorescence of 6a
was greatly influenced by the molecular aggregation. The
Q band spectrum caused the first π-π* transition of 6 in
DMF and showed a characteristic pattern of a monomeric
species, with a fluorescence maxima at 653–658 nm. On
the other hand, 6 in chloroform did not show any fluores-
cence and had the characteristic patterns of an aggregate
(in Fig. 3).
Fig. 4. The effects of the solvent polarity on the absorption
spectra of 7a (3.44 × 10-5 M)
Fig. 3. Emission spectra of 6a (4.17 × 10-6 M) in DMF and CHCl3
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SyntheSIS anD OPtICal PrOPertIeS Of tetraPyrazInOPOrPhyrazIneS
537
a pair (or more) of porphyrazine units. However, the
Previous research showed that the F- anions can bind
within the cores of metallophthalocyanines and form
F--coordinated complexes [17]. On the other hand, 7b
shows single peak of Q bands and the molar absorptivity
(λmax = 651 nm, log ε = 4.49) was decreased. It can be
assumed that anions can cause the deprotonation of the
pyrrole NH group of metal-free pyrazinoporphyrazines,
leading to an optical change in metal-free tetrapyrazi-
noporphyrazine [18, 19].
spectra recorded for the 10-5 and 10-6 M solutions of
7 in chloroform, carbon tetrachloride, and THF were
identical in shape, implying that the aggregation was
not very effective for metal-free porphyrazines 7 due
to the bulky nature of the substituents that prevented
the interaction between the porphyrazine cores at these
concentrations.
Mg tetrapyrazinoporphyrazines exhibited no emis-
sion peaks in chloroform, but a strong emission peak
was observed at around 600–700 nm when TBAF was
added into the solution (Fig. 6). In contrast, unexpected
results were observed in the metal-free porphyrazines.
7a, 7b and 7c show the abnormal fluorescence quench-
ing repeatedly. They show high PL in chloroform with
no additive, and their emission disappeared when TBAF
was added. In a previous study, the emission spectra of
metal-free tetrapyrazinoporphyrazines typically had a
Spectral change upon the addition of a base
A great deal of research has focused on the optical
sensitivity of phthalocyanines because of their acid-base
properties [16]. Figure 5 shows the UV-visible spectral
changes of 6b and 7b upon the addition of tetrabutylam-
monium fluoride monohydrate (TBAF). Each of the
Q band spectra contained a sharp peak, and the molar
absorptivities of 6b (λmax = 647 nm, log ε = 4.76) were
higher than the solutions without addition of TBAF.
Fig. 5. Absorption spectral changes of 6b, 7b (7.0 × 10-5 M) with TBAF
Fig. 6. The emission spectra of 6b, 7b (7.0 × 10-7 M) with TBAF (molar ratio)
Copyright © 2010 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2010; 14: 537–539

538
C.K. Jang et al.
Table 2. Tendencies of 6 and 7 under the condition of solution
in chloroform
intermolecular interaction by concentration as shown in
Fig. 7. Thus, we assumed it is more appropriate that this
occurs as a result of the binding effect of the anion rather
than from an aggregation effect between macrocycles.
More investigation with regard to these phenomena will
be carried out in further research.
6
7
No TBAF
Aggregated form Monomeric form
PL quenched High PL
Addition of TBAF Monomeric form Aggregate-like form
High PL PL quenched
CONCLUSION
In summary, we successfully synthesized organic-
soluble tetrapyrazinoporphyrazines bearing long, linear
alkyl and tert-butyl phenyl substituents at peripheral
positions. Porphyrazines 6 and 7 have a satisfactory solu-
bility in chlorinated hydrocarbons, THF, toluene, and
n-hexane, but are practically insoluble in alcohols. Their
UV-visible spectra show the typical shape of phthalocya-
nines, and this changed by solvatochromism due to the
existence of different aggregated species.
Acknowledgements
This study was supported by a grant from the Funda-
mental R&D Program (M200701004) for Core Technol-
ogy of Materials funded by the Ministry of Commerce,
Industry and Energy in Korea.
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