Synthesis and aggregation study of optically active tetra-β-[(S)-2- octanyloxy]-substituted copper and nickel phthalocyanines

Article abstract of DOI:10.1007/s12039-010-0069-9

The optically active tetra-β-[(S)-2-octanyloxy]-substituted copper and nickel phthalocyanines were synthesized via a two-step route with 4-nitro-phthalonitrile and (S)-2-octanol as the starting materials. Both compounds are fully characterized by MS,

Full text of DOI:10.1007/s12039-010-0069-9

J. Chem. Sci., Vol. 122, No. 6, November 2010, pp. 813–818. © Indian Academy of Sciences.
Synthesis and aggregation study of optically active tetra-β-
[(S)-2-octanyloxy]-substituted copper and nickel phthalocyanines
a,b
c
b
b
a
FANG-DI CONG , GUI GAO , JIAN-XIN LI , GUO-QING HUANG , ZHEN WEI ,
a
a,b,
a,
FENG-YANG YU , XI-GUANG DU * and KE-ZHI XING *
a
Tianjin Key Laboratory of Aqua-ecology and Aquaculture, Department of Basic Sciences,
Tianjin Agricultural University, Tianjin 300384, China
b
Faculty of Chemistry, Northeast Normal University, Changchun 130024, China
c
Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education,
Jilin University, Changchun 130021, China
e-mail: xgdu@yahoo.cn; kzxing@yahoo.com.cn
MS received 29 December 2009; revised 24 June 2010; accepted 19 July 2010
Abstract. The optically active tetra-β-[(S)-2-octanyloxy]-substituted copper and nickel phthalocyanines
were synthesized via a two-step route with 4-nitro-phthalonitrile and (S)-2-octanol as the starting materi-
1
als. Both compounds are fully characterized by MS, H NMR, UV-Vis, IR, CD and elemental analysis,
and soluble in common organic solvents except methanol. The results showed that they were dispersed
into single molecules in chloroform and dichloromethane, but prone to congregate into H-type aggregates
in ethanol and diethyl ether. They assembled to H-type aggregates with left-handed helix when deposited
as thin films.
Keywords. Synthesis; spectra; aggregation; chirality.
1. Introduction
optically active Pcs were too less to meet require-
ment of investigation on chiral stacking due to ra-
cemization of chiral chain substrates at reaction
temperature even if some of them were commer-
cially available. In order to obtain new optically
active Pcs, here (S)-2-octanol was selected as the
original chiral molecules to synthesize optically
active tetra-β-[(S)-2-octanyloxy]-substituted copper
and nickel phthalocyanines (4a and 4b) at 135°C by
Phthalocyanine (Pc) compounds have received much
attention for their potential applications in optoelec-
1
2
tronic technologies, catalytic materials and film
3
materials , etc. All these applications were attributed
to the largely flat 18-electron π-conjugated system
4
and the central metal of them. Moreover, they could
be modified by introducing various substituents on
the periphery moiety of Pc ring to generate new de-
11
a modified synthetic method and for that no race-
5
rivatives with enhanced solubility or novel func-
mization was found for (S)-2-octanol at more than
6
12
tionality. Hence, a considerable effort has been
140°C. The characterization on them showed that
made to obtain structurally desired Pc compounds
they were optically active and had strong intermo-
lecular forces in some organic solvents though they
had excellent solubility, which compelled Pc mole-
cules to form H-type aggregates.
7
for practicality. Among them, optically active Pcs
have attracted chemists in the last ten years for their
8,9
special chiral stacking.
Optically active Pcs reported to date, could fall
mainly into three groups: (i) Pcs containing chiral
carbons in the side chain; (ii) Pcs with optically ac-
2. Experimental
tive aromatic molecules; (iii) Pcs with planar asym-
2.1 Materials and methods
8–10
metry.
More attention was given to the first
group of optically active Pcs usually behaved multiple 2-(Dimethylamino)ethanol (DMAE) was distilled
10
liquid crystal mesophases. However, this kind of from Na prior to use. DMSO was pre-dried over
BaO and distilled under reduced pressure. (S)-2-
*For correspondence
octanol (99% ee) was bought from Sigma-Aldrich
813

814
Fang-Di Cong et al
(St. Louis, MO). Column chromatography purifica- under nitrogen for 24 h. After cooling under nitro-
tion was preformed on silica gel. All other reagents gen to room temperature, the dark solution was di-
and solvents were of commercial grade and used luted with methanol and filtered in vacuo to afford a
without further purification.
solid, which was extracted with a Soxhlet apparatus
1
H NMR spectra were recorded on an INOVA- using methanol as the solvent and then further puri-
500 spectrometer. IR spectra were measured on a fied by silica gel column chromatography with chlo-
Magna 560 FT–IR spectrometer. UV-Vis spectra roform as mobile phase to give pure blue solid 4a:
1
were taken on a Cary 500 UV–VIS–NIR spectropho- 2⋅26 g, Yield: 52%; H NMR (500 MHz, CDCl ): δ
3
tometer. MS spectra were obtained on a LDI–1700– 11⋅22–8⋅47 (s, broad, 12H, ArH), 4⋅38–4⋅85
TOF mass spectrometer. Elemental analyses were (s, broad, 4H, 4OCH), 2⋅01–0⋅88 (m, broad, 64H,
performed on a Perkin–Elmer 2400 Elemental Ana- 4CH (CH ) and 4CH ); MS (CHCl ): m/z calcd. for
3
2 5
3
3
lyzer. Circular dichroism (CD) spectra were meas- [M]: 1088⋅9, found: 1088⋅4 [M]; UV-Vis (CHCl ):
3
ured at room temperature on a JASCO-810 system.
λ
= 288, 339, 384, 617, 685 nm; IR (KBr): 1234
max
–1
Optical rotation was measured with a WZZ–1S digi- vs cm (C–O–C); Anal. Calcd. for C H N O Cu
64 80 8 4
tal automatic polarimeter.
(1088⋅9): C 70⋅59, H 7⋅41, N 10⋅29, Found: C 70⋅62,
H 7⋅53, N 10⋅22.
The compound 4b obtained by the aforesaid
2.2 Synthesis of 4-[(S)-2-octanyloxy]phthalonitrile 3
1
procedure gave: 2⋅95 g, yield: 68%; H NMR
(500 MHz, CDCl ): δ 8⋅09–6⋅05 (m, broad, 12H,
3
10⋅39 g 1 (60 mmol) and 7⋅81 g 2 (60 mmol) were
added to 100 mL anhydrous DMSO at room tem-
perature. The reaction mixture was stirred and then
3⋅6 g LiOH (150 mmol) was interfused over 2 h. The
mixture was continually stirred and monitored by
TLC. After 24 h, the mixture was then poured into
300 mL 10% NaCl solution and extracted with
100 mL chloroform twice. The combined organic
layer was washed by 100 mL water and dried with
anhydrous Na SO . The product was collected by
ArH), 4⋅77–4⋅93 (m, broad, 4H, 4OCH), 2⋅14–1⋅04
(m, broad, 64H, 4CH (CH ) and 4CH ); MS
3
2 5
3
(CHCl ): m/z calcd. for [M]: 1084⋅1, found: 1083⋅7
3
[M]; UV-Vis (CHCl ): λ = 302, 328, 385, 610,
3 max
–1
678 nm; IR (KBr): 1235 vs cm (C–O–C); Anal.
Calcd. for C H N O Ni (1084⋅1): C 70⋅91, H 7⋅44,
64 80
8
4
N 10⋅34, Found: C 70⋅87, H 7⋅47, N 10⋅26.
2.4 Preparation of depositing films
2
4
removing solvent and further purified by flash col-
umn chromatography with chloroform as mobile The preparation of films of 4a and 4b deposited
phase to afford light yellow adhered liquid 3: on quartz glass was carried out as follows. A piece
1
12⋅46 g, yield: 81%; b.p. > 200°C; H NMR of thin quartz glass (10 × 10 × 0⋅2 mm) was pre-
(500 MHz, CDCl ): δ 7⋅69 (d, J = 9, 1H, ArH), 7⋅22 cleaned with acetone and dried in air, and then
3
(s, 1H, ArH), 7⋅14 (d, J = 9, 1H, ArH), 4⋅45 (m, 1H, immersed in 10 mL solution of 4a or 4b in CHCl
OCH), 1⋅75 (m, 2H, CH ), 1⋅62 (m, 3H, CH ), 1⋅42 (1⋅0 × 10 mol/L) in a 50 mL beaker. Subsequently,
3
–5
2
3
(m, 2H, CH ), 1⋅28–1⋅35 (m, 6H, CH CH CH ), 0⋅88 the beaker was covered by a filter paper and set
2
2
2
2
(m, 3H, CH ); MS (CHCl ): m/z calcd. for aside for one day to let chloroform evaporate to
3 3
+
[M + Na] : 279⋅3, found: 279⋅6 (an isotopic cluster leave behind the blue film deposited on quartz glass.
peak) [M + Na] ; IR (KBr): 2231 vs cm (C≡N),
+
–1
–1
1253 vs cm
(C–O–C); UV-Vis (CHCl ):
3
3. Results and discussion
20
λ
= 264, 302, 310 nm. [α]
(0⋅69%, CHCl )
3
max
D
+15⋅6; Anal. Calcd. for C H N O (256⋅3): C 74⋅97,
16 12
2
3.1 Synthesis and characterization
H 7⋅86, N 10⋅93, Found: C 74⋅93, H 7⋅63, N 10⋅85.
Following the general synthetic route for tetra-
substituted Pcs involving the aromatic nucleophilic
substitution reaction between nitrophthalonitriles
and a suitable oxygen nucleophile followed by
cyclotetramerization of the resultant phthalonitrile
2.3 Synthesis of 4a and 4b
4⋅10 g Phthalonitrile derivative 3 (16⋅0 mmol) and
0⋅87 g Cu(OAc) ⋅2H O (4⋅0 mmol) were added to a
2
2
11
derivatives, a modified procedure was employed to
stirred DMAE (15 mL) in a 50 mL one-neck round-
bottomed flask equipped with an air condenser. The
resulting solution was stirred and heated at 135°C
synthesize Pc compounds 4a and 4b (scheme 1).
Phthalonitrile (1) and optically active (S)-2-octanol

Optically active tetra-β-[(S)-2-octanyloxy]-substituted copper and nickel phthalocyanines
815
Scheme 1.
(2) were chosen as starting materials to synthesize ence was that the Q band of 4b shifted blue 7 nm
phthalonitrile derivative 3 with good yield in the than 4a, which was caused by much electron-pulling
presence of LiOH and anhydrous DMSO at room power of Ni (II) for its less d electrons relative to Cu
temperature. Because phthalonitrile (3) was a light (II), to decrease electron cloud of Pc ring and bring
14
yellow viscous liquid, so it was firstly separated blue shift of Q band.
from the reaction mixtures by extraction with chlo-
roform and then purified by flash column chroma-
3.2 Understanding UV-Vis spectra
tography. Upon treatment with Cu(OAc) or NiCl
2
2
in DMAE under nitrogen at 135°C, 4a and 4b were
synthesized from phthalonitrile (3), respectively.
They could be first washed by Soxhlet extraction
with methanol to remove most of impurities, and
further purified by flash column chromatography
with chloroform as mobile phase. The synthesized
Besides methanol, both 4a and 4b could be dis-
solved in common organic solvents. Especially in
chloroform and diethyl ether, they showed excellent
solubility. But the dispersed states of them in two
organic solvents were very different, which could be
understood by UV-Vis spectra analysis (figure 2 and
table 1). For example 4a, in chloroform, a high Q
band (685 nm) and a little shoulder peak (617 nm)
were observed, which shows that Pc molecules were
1
Pc compounds were characterized by MS, H NMR,
UV-Vis, IR, CD and elemental analysis, which were
consistent with the proposed structures (scheme 1).
In their mass spectra, the peaks of singly charged
molecular ions were obvious, e.g. mass spectrum of
15
dispersed well. But in ethyl ether, the shoulder
1
peak increased greatly and the Q band lowered
some. Moreover, when the volume ratio of chloro-
form/diethyl ether changed from 1 : 0 to 0 : 1, the Q
band gradually shifted blue from 685 to 676 nm and
the logarithm of molar extinction coefficient (log ε)
decreased from 5⋅20 to 5⋅13. Synchronously the
shoulder peak shifted red from 617 to 623 nm and
the log ε increased from 4⋅55 to 4⋅91. Accordingly,
the colour of solution changed from primal cyan
to final blue. The phenomena implied that
H-aggregates gradually formed from Pc molecules
4a (figure 1). The H NMR spectra of them were
strongly impacted by paramagnetism of the center
13
Cu (II) and Ni (II) in a square planar environment,
which resulted in that both 4a and 4b displayed
1
three broad bands in H NMR spectra: 4a, δ 11⋅22–
8⋅47 (H bonding with aromatic ring), 4⋅38–4⋅85 (H
bonding with chiral carbon), 2⋅01–0⋅88 (H bonding
with non-chiral carbons in (S)-2-octanyloxyl); 4b,
δ 8⋅09–6⋅05, 4⋅77–4⋅93, 2⋅14–1⋅04 (corresponding to
the aforementioned three kinds of hydrogen, respec-
–1
tively). The IR absorptions at 1234 cm (C–O–C)
16
–1
according to a co-facial method, namely 4a was
for 4a and at 1235 cm (C–O–C) for 4b meant the
inclined to form H-aggregates in ethyl ether. Further
the same aggregation tendency was found for 4a and
4b in some molecule-oxygenic solvents, such as
ethanol, acetic ether, tetrahydrofuran, etc. Contrarily,
no similar phenomena were observed for them in
characteristic vibration of chemical bond linking
(S)-2-octanyloxy group and Pc ring. From the UV-
vis spectra of 4a and 4b in chloroform, it was found
that the typical Q-band absorptions were at 685 nm
and 678 nm, respectively (figure 2). The only differ-

816
Fang-Di Cong et al
Figure 1. MS of synthesized Pc 4a.
Figure 2. The UV-Vis spectra of solutions of 4a and 4b in chloroform/ethyl ether (1⋅0 ×
10 mol/L, v/v, 1 : 0 (a); 2 : 1 (b); 1 : 1 (c); 1 : 2 (d); 0 : 1 (e)), and films of them (f) prepared
–5
by deposition of them on thin quartz glass.
molecule-oxygen-free solvents, e.g. chloroform and phobic regions between Pc molecules and disperse
dichloromethane. them nicely. But it was not easy for ethyl ether
The aforementioned phenomena might be under- molecules to approach Pc ring owing to the exis-
stood through following points. There were two tence of hydrophilic ether-oxygen atom. Accord-
main intermolecular actions between solvent and Pc ingly the coordination of the ether–oxygen atom
molecules. One was the strong affinity between sol- with the center metals Cu (II) or Ni (II) was also too
17
vent and 2-octanyloxy groups around Pc rings, weak to disperse 4a or 4b. The result was that the
which prevented Pc molecules from depositing and intermolecular action compelled them to congregate
caused them to show excellent solubility in chloro- to some H-aggregates. The phenomenon is similar to
form or ethyl ether. The other one was the weak ac- the water-soluble Pc compounds, which usually
tion between solvents and 18-electron π-conjugated formed H-aggregates and generated broad Q bands
systems of Pcs, which led to different dispersed in water in which though they could be easily dis-
18
states for them in two kinds of solvents. The chloro- solved. The excellent solubility of water-soluble
form molecules could readily insert into the hydro- Pcs is mainly derived from the affinity between water

Optically active tetra-β-[(S)-2-octanyloxy]-substituted copper and nickel phthalocyanines
817
–5
Table 1. UV-Vis spectral parameters of 4a and 4b in chloroform/ethyl ether (1⋅0 × 10 mol/L), and the
solid films.
Chloroform/ethyl ether (v/v)
Samples λ (nm), log ε
1 : 0
2 : 1
1 : 1
1 : 2
0 : 1
Films
Q
685, 5⋅20
617, 4⋅55
678, 5⋅22
610, 4⋅53
683, 5⋅19
617, 4⋅65
676, 5⋅20
610, 4⋅62
681, 5⋅17
618, 4⋅74
674, 5⋅18
622, 4⋅73
679, 5⋅15
623, 4⋅81
673, 5⋅17
622, 4⋅87
676, 5⋅13
623, 4⋅91
669, 5⋅14
622, 4⋅98
618
–
4a
S *
4a
Q
615
–
4b
S *
4b
*‘S’ represents the shoulder peak near left of Q band. –, means unobvious peak.
the instrument fell in the range of the great Q ab-
sorbance (550–750 nm) of Pc compounds. But they
could be indirectly estimated to be optical active by
measuring the optical rotation of unreacted 3 sepa-
rated from remnants, which showed that 3 was not
racemized after undergoing the reaction conditions
under which to synthesize 4a and 4b. Thereby the
optical activity of 3 was concluded to be kept in the
synthesized Pc compounds.
As we all know, CD spectra were from a chiral
stacking of large numbers of optically active mole-
cules or were induced by enough big chiral mole-
9
cules, e.g. protein and nucleic acid. It was found 4a
and 4b in chloroform or ethyl ether did not offer any
CD activity. This accounted for that 4a and 4b
mainly existed in the form of single molecules or
small H-type dimmers and oligomers in solution. H-
type aggregates formed were not enough in solution
to bring CD activity for excellent solubility of them.
However, the deposition films of 4a and 4b on thin
quartz glass displayed characteristic CD spectra
(figure 3). It was deduced that the films must result
from a stacking of large numbers of chiral mole-
cules. According to a chiral exciton coupling theory
Figure 3. CD spectra of films for 4a (1) and 4b (2).
and hydrophilic substituents around Pc ring, but the
water molecules could not effectively insert in-
between hydrophobic Pc rings to prevent them from
forming H-aggregates.
The transmission UV-Vis spectra of solid films of
4a and 4b deposited on thin quartz glasses all dis-
played broad and shift-blue Q bands relative to the
liquid UV-Vis spectra. For example 4a, there were a
main absorption band around 618 nm and an unob-
vious absorption band at around 680 nm (figure 2).
The main band shifted blue 67 nm relative to the Q
band in chloroform, which meant that 4a mainly
existed in the form of H-aggregates in solid state for
that, as a rule, the Q bands of Pc H-aggregates in
solid markedly shifted blue relative to Pc molecules
20
attested in the literature, the positive CD patterns
corresponding to the main Q bands (at around
620 nm) suggested that the molecules stacked mainly
in the form of a left-handed helix in solid films.
Contrarily, the deposition films of metal Pcs substi-
tuted by racemic 2-octanyloxy groups synthesized by
same method did not show any CD activity, which
implied that the racemic molecules in films did not
stack by chiral method. Combining the UV-Vis with
CD spectra of solid films, it was known that the
molecules of 4a and 4b mainly existed in the form
of H-aggregates with left-handed helix in films.
19
in solutions.
3.3 Chirality and CD spectra
4. Conclusions
The optical rotation of 4a and 4b could not be ob-
tained on a WZZ-1S digital automatic polarimeter
since the wavelength (589 nm) of sodium lamp in
In summary, two optically active Pc derivatives 4a
and 4b have been successfully synthesized from

818
Fang-Di Cong et al
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1
terized by MS, H NMR, UV-Vis, IR and CD spec-
tra. They have excellent solubility in common organic
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exist mainly as H-type aggregates forming a left-
handed helix.
6. Drechsler U, Pfaff M and Hanack M. 1999 Eur.
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Acknowledgements
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Authors thank the National Science Foundation of
China (NSFC 20472014, E030905-90505008), the
Scientific Program of Tianjin City (06TXT
JJC14200), the Jiangsu Province Science Foundation
of China (JSSFC BK2005126), and the 41st Post-
doctoral Science Foundation of China (20070
410332), for financial support. We also thank Dr
Chunyu Ma, Shanghai ChemPartner Co. Ltd. for his
help in English language corrections.
11. Ma C, Tian D, Hou X, Chang Y, Cong F, Yu H, Du X
and Du G 2005 Synthesis-stuttgart 2005 741
12. Cong F, Wang Y, Ma C, Yu H, Han S, Tao J and Cao
S 2005 Enzyme Microb. Tech. 4 595
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2005 Dyes Pigments 66 149
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