Preparation and optical properties of polyimide films linked with porphyrinato Pd (II) and Pt (II) complexes through a triazine ring and application toward oxygen sensors

Article abstract of DOI:10.1002/pola.28469

5-(3-Aminophenyl)-10,15,20-tri(4-methylphenyl) porphyrinato Pd (II) and Pt (II) complexes (2a-Pd) and (2a-Pt), respectively, were prepared from 5-(3-nitrophenyl)-10,15,20-tri(4-methyl-phenyl)porphyrin via two-step reactions, and reacted with cyanuric chloride to produce corresponding porphyrin derivatives (3a-Pd) and (3a-Pt) with a dichlorotriazine ring. Aromatic polyimides were prepared using diamine (4); triazine dichlorides having porphyrin units (3a-Pd), (3a-Pt), (3c-Pd), and (3c-Pt); fluoro-functionality 6-(p-perfluorononenyl oxyanilino)triazine-2,4-dichloride (6); and tetracarboxylic dianhydride (5) in N-methyl-2-pyrrolidone (NMP) at an elevated temperature up to 300 °C. The resulting viscous polymeric solution was cast on a glass plate, affording well-proportioned reddish transparent films with number-average molecular weights of 25,000–38,000. Glass transition temperatures of the polymers were ～230 °C; the films were stable up to 400 °C in air. The film emission spectra showed a broad peak ～670 nm, similar to those of porphyrins (2a-Pd) and (2a-Pt) dispersed in a polystyrene matrix. While the luminescence of these polymer films was quenched with oxygen, it rapidly recovered under a deoxygenated atmosphere. The polyimide film sensitivity to oxygen was higher under low oxygen concentrations than those of porphyrins (2a-Pd) and (2a-Pt) dispersed in polystyrene.

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Preparation and Optical Properties of Polyimide Films Linked with
Porphyrinato Pd (II) and Pt (II) Complexes Through a Triazine Ring
and Application Toward Oxygen Sensors
Takeshi Kimura,1 Shuichi Watanabe,1 Shin-ichi Sawada,2 Yuji Shibasaki,2 Yoshiyuki Oishi2
1Center for Instrumental Analysis, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551, Japan
2Department of Chemistry & Biological Sciences, Faculty of Science & Engineering, Iwate University, 4-3-5 Ueda, Morioka,
Iwate 020-8551, Japan
Correspondence to: T. Kimura (E-mail: kimura@iwate-u.ac.jp) or Y. Shibasaki (E-mail: yshibasa@iwate-u.ac.jp) or Y. Oishi (E-mail: yosh-
iyu@ iwate-u.ac.jp)
Received 18 October 2016; accepted 29 November 2016; published online in Wiley Online Library
DOI: 10.1002/pola.28469
ABSTRACT: 5-(3-Aminophenyl)-10,15,20-tri(4-methylphenyl) porphyr-
inato Pd (II) and Pt (II) complexes (2a-Pd) and (2a-Pt), respectively,
were prepared from 5-(3-nitrophenyl)-10,15,20-tri(4-methyl-phenyl)-
porphyrin via two-step reactions, and reacted with cyanuric chloride
to produce corresponding porphyrin derivatives (3a-Pd) and (3a-Pt)
with a dichlorotriazine ring. Aromatic polyimides were prepared
using diamine (4); triazine dichlorides having porphyrin units (3a-Pd),
(3a-Pt), (3c-Pd), and (3c-Pt); fluoro-functionality 6-(p-perfluorono-
nenyl oxyanilino)triazine-2,4-dichloride (6); and tetracarboxylic dia-
nhydride (5) in N-methyl-2-pyrrolidone (NMP) at an elevated
temperature up to 300 8C. The resulting viscous polymeric solution
was cast on a glass plate, affording well-proportioned reddish trans-
parent films with number-average molecular weights of 25,000–
38,000. Glass transition temperatures of the polymers were ꢀ230 8C;
the films were stable up to 400 8C in air. The film emission spectra
showed a broad peak ꢀ670 nm, similar to those of porphyrins (2a-
Pd) and (2a-Pt) dispersed in a polystyrene matrix. While the lumines-
cence of these polymer films was quenched with oxygen, it rapidly
recovered under a deoxygenated atmosphere. The polyimide film
sensitivity to oxygen was higher under low oxygen concentrations
than those of porphyrins (2a-Pd) and (2a-Pt) dispersed in polysty-
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KEYWORDS: gas permeation; luminescence; polyimides; porphyrin
complex; thermostability
systems.17 In order to construct sensors using porphyrin and
metalloporphyrin derivatives, these luminous compounds
should be deposited on a basal plate or included in polymer-
ic compounds. In addition, polymers as supports for lumi-
nous molecules are easily shaped as thin films and possess
high molecular permeability. Recently, Amao et al. reported
porphyrin-oxygen sensors supported by thin polystyrene and
other polymer films, which contained porphyrinato palladi-
um (II) or platinum (II) complexes in a noncovalent man-
ner18–20 and used in a velocity measurement device for
airplanes as pressure sensitive paint.21
INTRODUCTION Porphyrins and their metalated derivatives
have attracted much attention for their structural properties
and potential applications in many photoelectronic materi-
als.1–5 In the past few decades, many porphyrin derivatives
have been studied for their biological and pharmaceutical
activities.6,7 In addition to simple porphyrins, covalently
linked porphyrins, multiporphyrin oligomeres, widespread
porphyrine nanosheets, and related compounds have been
constructed to develop new types of functional materials.8–16
These molecules are also used to investigate the mechanism
of natural photosynthetic systems and to progress develop-
ment of sensors, optoelectronic devices, photovoltaic cells,
and photo-catalysis of photodynamic therapies for cancer.
One of the most useful characteristics of porphyrins and
metalloporphyrins is strong emission in solution and solid
states. Porphyrinato palladium (II) and platinum (II) com-
plexes are known to show strong emissions that can be
quenched in the presence of oxygen; hence, these com-
pounds can be used for molecular recognition in sensor
The three chlorine atoms in cyanuric chloride are known to be
able to be substituted in a step-by-step manner through a
temperature-controlled reaction.22–24 This procedure has been
applied to the synthesis of polymers, dendrimers, chiral mole-
cules, and related supramolecules.1,25–27 Polyimide (PI) is one
of the most useful polymers due to its unique properties such
as thermostability, transparency, low-dielectricity, and low
Additional Supporting Information may be found in the online version of this article.
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coefficient of thermal expansion.28–30 Therefore, this polymer an Ostwald viscometer. Thermal analyses were performed on a
is widely used for films, coatings, insulating material, electron-
ic components, and other functional applications. PI is general-
ly prepared by the reaction of tetracarboxylic anhydrides and
diamines, allowing mono-substituted triazine dichloride to be
used as one of the building blocks. We have reported the syn-
thesis and properties of triazine-containing thermoplastic31
and thermosetting32 PIs with unusual high solubility in organic
solvents and good mechanical properties.
Seiko thermal analyzer (SCC 5200 system) at a heating rate of
10 8C/min for thermogravimetric analysis (TGA by TG/DTA
320) under air or nitrogen. Differential scanning calorimetry
(DSC) was analyzed on a Shimadzu DSC-60 at a heating rate of
20 8C/min under nitrogen.
Aminophenylporphyrin Derivatives
5-(3-Aminophenyl)-10,15,20-tris(4-methylphenyl)porphyrin
(2a),37 5-(4-aminophenyl)-10,15,20- tris-(4-methylphenyl)-
porphyrin (2b),40 and 5-(4-aminophenyl)-10,15,20-triphe-
nylporphyrin (2c)41 were prepared by the methods
reported previously.
In the course of our study of phthalocyanine and tetraazapor-
phyrin derivatives,33–36 we have thought that PI films have poten-
tial applications in sensors, optoelectronic devices, and
photovoltaic cells if porphyrin derivatives could be conjugated to
the PI backbone. Therefore, we designed PI directly bonded to
metalloporphyrin derivatives as functional groups and, in this
case, the triazine ring served as a linker between the polymer
main-chains and porphyrin moieties. In this article, we report (1)
the construction of porphyrinato palladium (II) and platinum (II)
derivatives with a dichlorotriazine unit as building block for PIs,
(2) the preparation of the aromatic PI films directly linked
with porphyrin derivatives via the triazine spacer, and (3) the
examination of oxygen sensitivity of the films by observing the
emission of metalloporphyrins with palladium (II) and platinum
(II) metals.
Pt(II)-5-(3-aminophenyl)-10,15,20-tris(4-
methylphenyl)porphyrin (2a-Pt)
5-(3-Aminophenyl)-10,15,20-tris(4-methylphenyl)porphyrin
(2a) (0.1342 g, 0.2000 mmol), platinum bis(acetylacetonate)
(0.0463 g, 0.150 mmol), and phenol (20 mL) were placed in a
glass reactor and the mixture was refluxed for 24 h. After cooling
to room temperature, hot water and aqueous sodium hydroxide
solution were added and the precipitate was filtered. The resi-
due was dissolved in CHCl3 and washed with water. The organ-
ic layer was dried over MgSO4 and concentrated. The product
was purified by column chromatography (silica gel, CHCl3) to
afford orange crystals of the title compound in 52% yield
(0.0897 g).
EXPERIMENTAL
1H NMR (400 MHz, CDCl3) d 2.67 (s, 9H, CH3), 3.87 (bs, 2H,
NH2), 7.04 (d, J 5 7.9 Hz, 2H, Ar-H), 7.43–7.49 (m, 2H, Ar-H),
7.51 (d, J 5 7.4 Hz, 6H, Ar-H), 7.56 (d, J 5 7.4 Hz, 1H, Ar-H),
8.03 (d, J 5 7.4 Hz, 6H, Ar-H), 8.80 (d, J 5 4.9 Hz, 2H, Por-H),
8.81 (s, 4H, Por-H), 8.88 ppm (d, J 5 4.9 Hz, 2H, Por-H); UV
(kmax) 403, 511 nm (CHCl3); IR (KBr) 3324, 3028, 1617,
801 cm21; FABMS (m/z) 864 (M1).
Materials
4,4’-(Hexafluoroisopropylidene)diphthalic anhydride (5) was
purchased from Aldrich and purified by sublimation prior to use.
4,4’-(Hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline (4)
was kindly donated by Seika, Japan. 4,6-Dichloro-N-(4-((1,1,1,
4,5,5,5-heptafluoro-3-(perfluoropropan-2-yl)-4-(trifluoromethyl)-
pent-2-en-2-yl)oxy)phenyl)-1,3,5-triazin-2-amine (6) was kindly
donated by NIPPON FUSSO and used as received. N,O-Bis(trime-
thylsilyl)trifluoroacetamide (BSTFA) was kindly donated by Shin-
Etsu Chemical and used as received.
Pt(II)-5-(4-aminophenyl)-10,15,20-tris(4-
methylphenyl)porphyrin (2b-Pt)
Orange crystals; 1H NMR (400 MHz, CDCl3) d 2.69 (s, 9H,
CH3), 4.00 (bs, 2H, NH2), 7.04 (d, J 5 8.1 Hz, 2H, Ar-H), 7.53
(d, J 5 7.7 Hz, 6H, Ar-H), 7.91 (d, J 5 8.1 Hz, 2H, Ar-H), 8.02
(d, J 5 7.7 Hz, 6H, Ar-H), 8.75 (bs, 4H, Por-H), 8.76 (d, J 5 4.9
Hz, 2H, Por-H), 8.83 ppm (d, J 5 4.9 Hz, 2H, Por-H); UV
Measurements
NMR spectra were measured with a Bruker AVANCE 500 III
spectrometer and a Bruker AC 400 spectrometer. Mass spectra
were obtained using a JEOL JMS-700 mass spectrometer and a
Hitachi M2000 mass spectrometer. Matrix assisted laser
desorption ionization-time of flight (MALDI-TOF) mass spec-
trometry was examined with a Bruker BIFLEX (III) mass spec-
trometer. UV–vis spectra were recorded with a JASCO Ubest V-
570 spectrophotometer. For IR measurements, a JASCO FT/IR-
4200 spectrometer was employed. Emission spectra were
measured by a JASCO FP-6500 spectrometer. The number-
average molecular weights (Mn), weight-average molecular
weights (Mw), and dispersities (Mw/Mn) were determined
using a Tosoh HLC-8220 gel permeation chromatograph (GPC)
equipped with refractive index and UV detectors, and a consec-
utive polystyrene gel column (TSK-GEL a-M 3 2) at 40 8C and
eluted with N-methylpyrollidone (NMP) at a flow rate of
(kmax
) 403, 512 nm (CHCl3); IR (KBr) 3320, 1616,
800 cm21; FABMS (m/z) 864 (M1).
Pt(II)-5-(4-aminophenyl)-10,15,20-tetraphenylporphyrin
(2c-Pt)
Orange crystals; 1H NMR (400 MHz, CDCl3) d 3.99 (bs, 2H,
NH2), 7.03 (d, J 5 8.2 Hz, 2H, Ar-H), 7.66–7.80 (m, 9H, Ar-H),
7.91 (d, J 5 8.2 Hz, 6H, Ar-H), 8.12–8.18 (m, 6H, Ar-H), 8.73
(bs, 4H, Por-H), 8.74 (d, J 5 4.7 Hz, 2H, Por-H), 8.85 ppm (d,
J 5 4.7 Hz, 2H, Por-H); UV (kmax) 407, 511 nm (CHCl3); IR
(KBr) 3025, 1618, 796 cm21 (NH2); FABMS (m/s) 822 (M1).
Pd(II)-5-(3-aminophenyl)-10,15,20-tris(4-
methylphenyl)porphyrin (2a-Pd)
1.0 mL/min. The inherent viscosities of the polymers were Orange crystals; 1H NMR (400 MHz, CDCl3) d 2.69 (s, 9H,
determined for solutions of 0.1 g/20 mL in NMP at 30 8C using
CH3), 3.90 (bs, 2H, NH2), 7.04–7.09 (m, 1H, Ar-H), 7.45–7.59
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(m, 9H, Ar-H), 8.01–8.06 (m, 6H, Ar-H), 8.811 (s, 4H, Por-H),
8.814 (d, J 5 4.9 Hz, 2H), 8.88 ppm (d, J 5 4.9 Hz, 2H, Ar-H);
UV (kmax) 419, 487, 525, 556 nm (CHCl3); IR (KBr) 3324,
3028, 1617, 801 cm21; SIMS (m/z) 775 (M1).
Pd(II)-5-[4-amino(1,3,5-triazine-2,4-dichloride)phenyl]-
10,15,20-triphenylporphyrin (3c-Pd)
Orange crystals; 1H NMR (400 MHz, CDCl3) d 7.69–7.80 (m,
9H, Ar-H), 7.83 (bs, 1H, NH), 7.88 (d, J 5 8.3 Hz, 2H, Ar-H),
8.13–8.21 (m, 8H,), 8.80 (d, J 5 5.0 Hz, 2H, Por-H), 8.81(s,
4H, Por-H), 8.82 ppm (d, J 5 5.0 Hz, 2H, Por-H); UV (kmax
416, 525 nm (CHCl3); IR (KBr) 3286, 2923, 1610, 1542,
1166, 799 cm21; FABMS (m/z) 881 (MH1).
)
Pd(II)-5-(4-aminophenyl)-10,15,20-tris(4-
methylphenyl)porphyrin (2b-Pd)
Orange crystals; 1H NMR (400 MHz, CDCl3) d 2.69 (s, 9H,
CH3), 4.01 (bs, 2H, NH2), 7.04 (d, J 5 8.3 Hz, 2H, Ar-H), 7.53
(d, J 5 7.7 Hz, 6H, Ar-H), 7.93 (d, J 5 8.3 Hz, 2H, Ar-H), 8.04
(d, J 5 7.7 Hz, 6H, Ar-H), 8.807 (bs, 4H, Por-H), 8.813 (d,
J 5 4.8 Hz, 2H, Por-H), 8.89 ppm (d, J 5 4.8 Hz, 2H, Por-H);
UV (kmax) 414, 525 nm (CHCl3); IR (KBr) 3323, 3028, 1618,
800 cm21; FABMS (m/z) 775 (M1).
Pt(II)-5-[4-amino(1,3,5-triazine-2,4-dichloride)phenyl]-
10,15,20-triphenylporphyrin (3c-Pt)
Orange crystals; 1H NMR (400 MHz, CDCl3) d 7.66–7.79 (m,
10H, NH, Ar-H), 7.83 (d, J 5 8.4 Hz, 2H, Ar-H), 8.09–8.18 (m,
8H, Ar-H), 8.23 (d, J 5 5.2 Hz, 2H, Por-H), 8.75 (s, 4H, Por-H),
8.76 ppm (d, J 5 5.2 Hz, 2H, Por-H); UV (kmax) 405, 510 nm
(CHCl3); FABMS (m/z) 970 (MH1).
Pd(II)-5-(4-aminophenyl)-10,15,20-tetraphenylporphyrin
(2c-Pd)
Synthesis of PIs and the Film Fabrication
Typical Procedure for 0.5 mol % 3a-Pd PI
Orange crystals; 1H NMR (400 MHz, CDCl3) d 4.01 (bs, 2H,
NH2), 7.04 (d, J 5 8.3 Hz, 2H, Ar-H), 7.68–7.80 (m, 9H, Ar-H),
7.94 (d, J 5 8.3 Hz, 6H, Ar-H), 8.13–8.20 (m, 6H, Ar-H), 8.79
(bs, 4H, Por-H), 8.80 (d, J 5 4.9 Hz, 2H, Por-H), 8.91 ppm (d,
J 5 4.9 Hz, 2H, Por-H); UV (kmax) 416, 525 nm (CHCl3); IR
(KBr) 3025, 1617 cm21 (NH2); FABMS (m/s) 733 (M1).
To a solution of compound (4) (2.092 g, 5.000 mmol) in dry
NMP (12.5 mmol) cooled with an ice bath, N,O-bis(trimethyl-
silyl)trifluoroacetoamide (BSTFA) (3.20 mL, 10.0 mmol) was
added through a syringe and the solution was stirred at 0 8C
for 0.5 h and 20 8C for 15 min. 4,4’-(hexafluoroisopropylide-
ne)diphthalic anhydride (5) (2.221 g, 2.500 mmol), 6-(p-
perfluorononenyloxy anilino)-1,3-triazine-2,4-dichloride (6)
(1.709 g, 2.488 mmol) and the porphyrin complex (3a-Pd)
(0.0230 g, 0.0249 mmol) were simultaneously added at 0 8C
and the solution was stirred at 20 8C for 4 h, then stirred at
160 8C for 24 h. The resulting viscous mixture was poured
into methanol to precipitate the polymer, which was dried at
80 8C under vacuum for 9 h (quantitative yield). The poly-
mer was dissolved in NMP, cast on a glass plate, dried at 20,
100, 150, 200, 250, and 300 8C for 6 h each under reduced
pressure to produce a reddish transparent self-standing film.
IR (KBr) 3500 (NH), 2950 (C-HAr), 1786 (imide C@O), 1731
(imide C@O), 1500 (C@CAr), 1417 (imide CAN), 1250 (ether)
Pd(II)-5-[3-amino(triazine-2,4-dichloride)phenyl]-
10,15,20-tris(4-methylphenyl)porphyrin (3a-Pd)
Orange crystals; 1H NMR (400 MHz, CDCl3) d 2.63 (s, 9H,
CH3), 7.46 (d, J 5 7.9 Hz, 6H, Ar-H), 7.620 (s, 1H, NH), 7.621
(dd, J 5 8.3, 7.6 Hz, 1H, Ar-H), 7.83 (dd, J 5 8.3, 1.6 Hz, 1H,
Ar-H), 7.95 (dd, J 5 7.6, 1.6 Hz, 1H, Ar-H), 8.00 (d, J 5 7.9 Hz,
6HAr-H), 8.10 (t, J 5 1.6 Hz, 1H, Ar-H), 8.79 (d, J 5 5.0 Hz,
2H, Por-H), 8.81 (s, 4H, Por-H), 8.82 ppm (d, J 5 5.0 Hz, 2H,
Por-H); UV (kmax) 418, 525 nm (CHCl3); IR (KBr) 3286,
2923, 1610, 1542, 1166, 1015, 799 cm21; MALDI-TOFMS
(m/z) 921.853 (M1).
cm21; elemental analysis (C228.5H118.3F87.30N20.18O22.49Pd0.0249
calcd (%) C: 53.07, H: 2.33, N: 5.45; found (%) C: 52.59, H: 2.39,
N: 5.98.
)
Pt(II)-5-[3-amino(triazine-2,4-dichloride)phenyl]-
10,15,20-tris(4-methylphenyl)porphyrin (3a-Pt)
To a solution of cyanuric chloride (0.0374 g, 0.200 mmol) in
tetrahydrofuran (THF) (15 mL), Pt(II)-5-(3-amino-phenyl)-
10,15,20-tris(4-methylphenyl)porphyrin (2a-Pt) (0.1286 g,
0.1500 mmol) in THF was slowly added at 0 8C and the solu-
tion was stirred for 2 h. An aqueous potassium carbonate
solution was added slowly, and the solution was stirred for
another 3 h. The organic layer was dried over MgSO4 and
the solvent was concentrated. The product was purified by
column chromatography (silica gel, CH2Cl2) to afford orange
crystals of the title compound in 90% yield (0.1356 g).
RESULTS AND DISCUSSION
Preparation of Aminophenylporphyrin Derivatives
As a typical procedure for preparation of unsymmetrically
substituted porphyrins, the statistical reaction of pyrrole with
p-tolaldehyde and m-nitrobenzaldehyde (reaction ratio 5 4:3:1
in mol) was conducted in chloroform at room temperature
under nitrogen in the presence of trifluoroborane-etherate.
The reaction mixture was treated with chloranil, according to a
method previously reported.37–40 The reaction gave symmetri-
cand unsymmetrical five porphyrin isomers, together with the
desired 5-(3-nitrophenyl)-10,15,20-tri(4-methylphenyl)por-
phyrin (1a), which was isolated from by column chromatogra-
phy. Mono(4-nitrophenyl)porphyrin (1b) was prepared by a
similar procedure using p-nitrobenzaldehyde. Subsequently,
the nitro group of the products was reduced by tin(II) chloride
in concentrated hydrochloric acid and the reaction gave 5-(3-
1H NMR (400 MHz, CDCl3) d 2.67 (s, 9H, CH3), 7.52 (d,
J 5 7.7 Hz, 6H, Ar-H), 7.66 (bs, 1H, NH), 7.73 (t, J 5 7.5 Hz,
1H, Ar-H), 7.94–8.03 (m, 2H, Ar-H), 8.01 (d, J 5 7.7, 6H,
Ar-H), 8.17 (bs, 1H, Ar-H), 8.76 (d, J 5 5.1 Hz, 2H, Por-H),
8.77 (s, 4H, Por-H), 8.79 ppm (d, J 5 5.1 Hz, 2H, Por-H); UV
(kmax) 405, 510 nm (CHCl3); IR (KBr) 2918, 1540, 1166,
1017, 797 cm21; FABMS (m/z) 1012 (MH1).
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SCHEME 1 Preparation of aminophenylporphyrinato Pd (II) and Pt (II) derivatives.
aminophenyl)- and 5-(4-aminophenyl)-10,15,20-tri (4-methyl-
phenyl)porphyrin derivatives (2a) and (2b) in 94 and 84%
yields, respectively (Scheme 1). 5-(4-Aminophenyl)-10,15,20-
triphenylporphyrin (2c) was successfully prepared using
Kruper’s procedure.41 To introduce palladium and platinum
atoms to the free base porphyrins, we treated 2a, 2b, and 2c
with palladium (II) acetate or platinum (II) acetylacetonate in
phenol at reflux temperature. These reactions produced the
corresponding palladium (II) or platinum (II) complexes in 67
(2a-Pd), 70 (2b-Pd), 58 (2c-Pd), 52 (2a-Pt), 57 (2b-Pt), and
57% (2c-Pt) yields.
Pd), and 89% (3c-Pt) yields. The structure of the products
1
was confirmed by H NMR spectroscopy and mass spectrom-
1
etry. While the H NMR spectra showed the amino groups of
3a-Pd and 3a-Pt in the aromatic region at d 5 7.62 and
d 5 7.66 ppm, respectively, a singlet assigned to the methyl
groups was observed at d 5 2.63 ppm (3a-Pd) and d 5 2.67
ppm (3a-Pt). The spectra showed the peripheral pyrrole pro-
tons as one singlet peak and two doublet peaks. In the mass
spectra of the products, the corresponding molecular ion
peaks were observed for the respective compounds; MALDI
TOF MS for 3a-Pd m/z 5 921.853 (M1), FABMS for 3a-Pt m/
z 5 1012 (MH1), FABMS for 3c-Pd m/z 5 881 (MH1), and
FABMS for 3c-Pt m/z 5 970 (MH1).
The structure of the products was determined by 1H NMR
1
spectra and MS spectrometry. H NMR signals for the amino
Preparation of PI and the Film
groups of 2a-Pd and 2a-Pt were observed as a broad singlet
together with a singlet from the methyl groups; 2a-Pd
d 5 2.69 (CH3, 9H) and 3.90 (NH2, 2H) ppm; 2a-Pt d 5 2.67
(CH3, 9H) and 3.87 (NH2, 2H) ppm. The peripheral pyrrole
protons were observed as one singlet peak and two doublet
peaks. The mass spectrometry showed molecular ion peaks;
SIMS for 2a-Pd m/z 5 775 (M1), FABMS for 2b-Pd
m/z 5 775 (M1), FABMS for 2c-Pd m/z 5 733 (M1), FABMS
for 2a-Pt m/z 5 864 (M1), FABMS for 2b-Pt m/z 5 864
(M1), and FABMS for 2c-Pt m/z 5 823 (MH1). The UV–vis
spectra of 2a-Pd and 2a-Pt measured in chloroform showed
the Soret band at 419 nm and the Q bands at 487, 525, and
556 nm for 2a-Pd and the Soret band at 403 nm and a Q
band at 511 nm for 2a-Pt.
Cyanuric chloride and its mono-substituted dichloro deriva-
tives can be utilized as building blocks of PI; hence, we used
porphyrin derivatives 3a-Pd, 3a-Pt, 3c-Pd, and 3c-Pt as start-
ing compounds for PI synthesis (Scheme 3). Importantly, oxy-
gen sensors using thin polymer films are affected by the
characteristics of the polymeric materials, so they need high
oxygen permeability. In order to increase oxygen permeability
of the polymer film, we introduced fluorinated substituents on
the polymer chain by selecting a fluorine-based dichloride
monomer (6) as a building block, in addition to the aromatic
diamine (4) and aromatic tetracarboxylic anhydride (5). In
advance of polymerization, compound 6 was prepared by reac-
tion of p-perfluorononenyloxy aniline with cyanuric chloride.
Reaction of Monoaminophenylporphyrin Derivatives with
Cyanuric Chloride
To prepare a triazine derivative containing only one porphy-
rin group on the ring, we reacted cyanuric chloride with por-
phyrins 2a-Pd, 2b-Pd, 2c-Pd, 2a-Pt, 2b-Pt, and 2c-Pt at low
temperature; however, for these compounds, the solubility of
2b-Pd and 2b-Pt, with three 4-methylphenyl groups and one
4-aminophenyl group, was lower than that of 2a-Pd, 2c-Pd,
2a-Pt, and 2c-Pt. For this reason, compounds 2a-Pd, 2c-Pd,
2a-Pt, and 2c-Pt were reacted with 1 equivalent of cyanuric
chloride in THF at 0 8C under nitrogen and an aqueous
potassium carbonate solution was added slowly (Scheme 2).
The reaction produced porphyrin derivatives with one
dichlorotriazine group in 100 (3a-Pd), 90 (3a-Pt), 95 (3c-
SCHEME 2 Reaction of aminophenylporphyrins 2a and 2c with
cyanuric chloride.
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SCHEME 3 Preparation of PI with aminophenylporphyrins.
To prepare the aromatic PIs, we utilized an in situ N-
silylated method (Scheme 3). Thus, aromatic diamine (4),
aromatic tetracarboxylic anhydride (5), dichlorotriazine (6),
and porphyrin complexes 3a-Pd, 3a-Pt, 3c-Pd, and 3c-Pt
were simultaneously mixed in NMP at room temperature for
4 h in the presence of the silylation reagent BSTFA, then at
160 8C for 24 h to afford the corresponding poly(amic acid)
solution. The feed of porphyrins 3a-Pt, 3c-Pd, and 3c-Pt was
fixed at 1 mol % against 6, and the concentration of 3a-Pd
varied from 0.5 to 3 mol %. The polymer solution was cast
on a glass plate and successively heated under reduced pres-
sure to give the PI film. The formation of PI was confirmed
by IR spectroscopy (Supporting Information Fig. 1S). Since
the polymerization temperature was very high at 160 8C for
24 h, the dried film at 100 8C for 1 h did not have the char-
acteristic amide absorptions at 1640 cm21. With the curing
temperature, an absorption assignable to the imide ring at
1786 and 1731 cm21 became stronger, then saturated after
1 h at 250 8C. In order to ensure imidization, the curing
temperature was up to 300 8C (see Experimental section).
The formation of the PI was also supported by elemental
analysis.
Table 1 summarizes the results of the polymerization. All
polymers were obtained quantitatively after precipitation
from methanol, and the viscosity was sufficiently high, from
0.28 to 0.75 (dL/g) in NMP, to fabricate homogeneous thin
films. Molecular weights of lower viscosity samples were
estimated by GPC from 25,000 to 56,000 for Mn with reason-
able Mw/Mn values (1.7–3.0). The resulting PI samples all
show high thermostability of Td5 around 420 8C in air, and
the Tg values were around 230 8C as estimated by DSC. Since
the introduction of the porphyrin unit in this experiment is
less than 3 mol % (2 wt %), there does not seem to be a sig-
nificant influence on the thermal properties of the polymers.
The Mn and Mw/Mn values of the 3a-Pt derivative are higher
than those of the 3c-Pt derivative, which may result from
their structures.
TABLE 1 Viscosity and Thermal Properties of Porphyrin-PIs
Td5 (8C)d
Td10 (8C)d
Dichloride
Mn 3 1023
Mw/Mn
ginh (dL/g)
Tg (8C)
Air
N2
Air
N2
a
a
b
c
Monomer
Conc. (mol %)
e
e
3a-Pd
3a-Pd
3a-Pd
3a-Pd
3a-Pt
3c-Pd
3c-Pt
0.5
1.0
2.0
3.0
1.0
1.0
1.0
–
-
0.75
0.62
0.63
0.28
0.42
0.51
0.44
233
229
230
227
231
231
235
415
420
415
410
430
425
415
420
425
420
425
435
430
420
435
435
435
430
450
450
435
440
440
435
430
455
450
440
e
e
-
-
e
e
-
-
25.0
56.0
38.0
29.0
1.7
3.0
2.6
1.6
a
d
Determined by GPC (NMP with LiBr, PSt).
Measured in NMP (0.5 g/dL) at 30 8C.
Determined by DSC (20 8C/min).
Td5 and Td10 are the temperatures for 5% and 10% decomposition,
respectively (10 8C/min).
b
c
e
Insoluble in NMP.
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FIGURE 1 The emission spectra, kmax intensity relative to oxygen concentration, and Stern-Volmer plots of the porphyrin-
polystyrene films 2a-Pd (1 wt %) (left) and 2a-Pt (1 wt %) (right). [Color figure can be viewed at wileyonlinelibrary.com]
Optical Properties of Porphyrin Derivatives Contained
in a Polystyrene Film
The polystyrene film of the platinum derivative 2a-Pt was
excited with 403.5 nm light [Fig. 1(b)]. When the oxygen
concentration was 0%, the film showed strong emission
around 660 nm. The intensity of the emission also decreased
with an increase in oxygen concentration [Fig. 1(d)]. In these
cases, the Stern-Volmer plot of the spectra showed a linear
correlation [Fig. 1(f)]. As a result, the polystyrene film of the
platinum derivative 2a-Pt exhibited stronger emission at an
oxygen concentration of 0% compared to the palladium
derivative 2a-Pd.
The porphyrin derivatives (2a-Pd and 2a-Pt) were dispersed
into a polystyrene matrix by mixing the porphyrin com-
pounds with polystyrene in chloroform, followed by casting
the film.18–20 The porphyrin content was fixed to be 1 wt %
against the matrix polymer. The emission spectra of the
prepared film were measured under oxygen concentrations
of 0, 5, 10, 15, 20, 25, 50, and 100% at room temperature. As
shown in Figure 1(a), the spectra showed emission around
690 nm (excited with 418.5 nm light) for a 2a-Pd film dis-
persed in polystyrene matrix. When the oxygen concentration
was 0%, the emission showed maximum intensity. The emis-
sion intensity of the spectra decreased with an increase in
oxygen concentration [Fig. 1(c)]. In these cases, the Stern-
Volmer plot of the spectra showed a curved line [Fig. 1(e)].
Since the Stern-Volmer plot did not show a linear relation-
ship for the polystyrene film of 2a-Pd, palladium derivatives
could be only used as sensors at low concentrations of oxy-
gen. On the other hand, the polystyrene film of platinum
derivative 2a-Pt could be utilized as an oxygen sensor under
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FIGURE 2 The emission spectra, kmax intensity with respect to oxygen concentration, Stern-Volmer plot, and on/off switching
property of porphyrin-PI film 3a-Pd (3 mol %) in response to oxygen. [Color figure can be viewed at wileyonlinelibrary.com]
oxygen concentrations between 0% and 100%. Since the
platinum and palladium complexes of octaethylporphyrin
were reported to show strong phosphorescence at room
temperature, oxygen sensing system using 2a-Pd and 2a-Pt
are expected to quench the triplet state of these complexes.
Figure 2(d). The luminescence of this polymer film appeared
to be quenched by oxygen and recovered under deoxygenat-
ed conditions. The results using 3c-Pd are similar to that of
3a-Pd (not shown); hence, these compounds can be utilized
as sensors for low oxygen concentrations.
Optical Properties of Porphyrin Derivatives
Linked to a PI Film
The emission spectra of a film of platinum derivative 3a-Pt
were measured under oxygen concentrations of 0, 2, 4, 6, 8,
10, 20, and 100%. The spectrum was obtained using
403.5 nm excitation light when the oxygen concentration
was 0%. As shown in Figure 3(a), the emission spectra of
3a-Pt (1 mol %) showed a strong emission around 660 nm,
similar to the polystyrene film [Fig. 1(b)]. On the other
hand, when the concentration of oxygen increased, the
intensity of the emission in the spectra decreased [Fig.
3(b)]. In this case, the Stern-Volmer plot of the spectra
showed a linear correlation [Fig. 3(c)]. As shown, since the
intensity of the emission of the platinum derivatives were
strong, 1 mol % of the porphyrin derivative is sufficient to
utilize the compound in an oxygen sensor. The intensity of
the emission of the film appeared strong under an oxygen
concentration of 0% but weak under a 100% oxygen atmo-
sphere; however, the intensity recovered under deoxygenat-
ed condition. As such, the film could repeatedly be used as
an oxygen sensor [Fig. 3(d)]. Additionally, it appeared
that the sensitivity to oxygen of the PI film is higher than
that of porphyrins (2a-Pd) and (2a-Pt) contained in a poly-
styrene film.
The concentration of porphyrin 3a-Pd was varied from 0.5
to 3 mol % in the poly(amic acid) matrix by changing the
feed ratio of the monomers 6 and 3 (total 2.5 mmol) in the
polymerization reaction. PI films containing the porphyrin
derivative 3a-Pd were obtained by thermal treatment of the
poly(amic acid) films at an elevated temperature up to 300
8C as described above. When the emission of the film con-
taining 0.5, 1.0, and 2.0 mol % of porphyrin 3a-Pd was mea-
sured under 0% oxygen concentration, the intensity was
very low; hence, the results of the emission are shown in
Figure 2 using a film containing 3.0 mol % of porphyrin 3a-
Pd. The emission spectra of the film were measured under
oxygen concentrations of 0, 2, 4, 6, 8, 10, 20, and 100%, and
porphyrin 3a-Pd was excited using 418.5 nm light. Under an
oxygen concentration of 0%, the spectra showed emission
around 690 nm and the intensity of the emission decreased
with increasing oxygen concentration [Fig. 2(a,b)]. In these
cases, the Stern-Volmer plot of the spectra showed a curved
line [Fig. 2(c)]. When the oxygen concentration was reduced
to 0%, the strength of the emission recovered, as shown in
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FIGURE 3 The emission spectra, kmax intensity with respect to oxygen concentration, Stern-Volmer plot, and on/off switching property
of a porphyrin-polyimide film of 3a-Pt (1 mol %) in response to oxygen. [Color figure can be viewed at wileyonlinelibrary.com]
FIGURE 4 The emission spectra, kmax intensity with respect to oxygen concentration, Stern-Volmer plot, and on/off switching
property of a polyimide film of 3c-Pt (1 mol %) in response to oxygen. [Color figure can be viewed at wileyonlinelibrary.com]
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13 G. Bottari, G. de la Torre, D. M. Guldi, T. Torres, Chem. Rev.
2010, 110, 6768–6816.
As shown in Figure 4(a), the emission spectra of 3c-Pt
(1 mol %) were also measured at room temperature. The
emission spectra of a film of 3c-Pt was measured under oxy-
gen concentrations of 0, 2, 4, 6, 8, 10, 20, and 100%. The
intensity of the emission in the spectra varied with an
increase in the oxygen concentration, and the Stern-Volmer
plot of the spectra showed a linear correlation [Fig. 4(b,c)].
The intensity of the emission was repeatedly varied with
changing oxygen concentration [Fig. 4(d)].
14 A. Tsuda, A. Osuka, Science 2001, 293, 79–82.
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5-(3-Aminophenyl)-10,15,20-tristolylporphyrinato Pd (II) and
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zine ring as a linker substituent. Compounds (3a-Pd) and (3a-
Pt) showed a broad emission band around 670 nm and were
utilized as a building block for polyimide (PI) polymers. Porphy-
rin units were directly linked to the PI backbone a luminous
component. The emission spectra of the films were similar to
those of porphyrins (2a-Pd) and (2a-Pt). The luminescence of
this polymer film was quenched by oxygen. While the Stern-
Volmer plot did not show a linear correlation in PI films of 3a-
Pd and 3d-Pd, films of 3a-Pt and 3a-Pt exhibited a linear rela-
tionship in the plot. Films of the platinum derivatives, 3a-Pt and
3c-Pt, can be used as oxygen sensors at oxygen concentration
between 0% and 100%, and the sensitivity of these PI films are
slightly higher than that of the compounds in a polystyrene film.
19 Y. Amao, Y. Ishikawa, I. Okura, Anal. Chim. Acta 2001, 445,
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