The synthesis and spectroscopic properties of novel, photochromic indolinobenzospiropyran-based homopolymers prepared via ring-opening metathesis polymerization

Article abstract of DOI:10.1016/j.dyepig.2009.12.002

Three types of novel photochromic indolinobenzospiropyran-based homopolymers were prepared via the ring-opening metathesis polymerization of the strained bicyclic indolinobenzospiropyran derivative. The homopolymers were soluble in common organic solvents and displayed unusually high polydispersity as determined by gel permeation chromatographic analysis. UV-visible absorption spectroscopy analysis in solution revealed that the appealing photochromic behaviour exhibited by the respective monomers was retained.

Full text of DOI:10.1016/j.dyepig.2009.12.002

Dyes and Pigments 86 (2010) 74e80
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Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
The synthesis and spectroscopic properties of novel, photochromic
indolinobenzospiropyran-based homopolymers prepared via
ring-opening metathesis polymerization
*
Sam-Rok Keum , Su-Mi Ahn, Se-Jung Roh, So-Young Ma
Department of Advanced Material Chemistry, Korea University, Jochiwon 339-700, South Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Three types of novel photochromic indolinobenzospiropyran-based homopolymers were prepared via the
ring-opening metathesis polymerization of the strained bicyclic indolinobenzospiropyran derivative. The
homopolymers were soluble in common organic solvents and displayed unusually high polydispersity as
determined by gel permeation chromatographic analysis. UVevisible absorption spectroscopy analysis in
solution revealed that the appealing photochromic behaviour exhibited by the respective monomers was
retained.
Received 6 October 2009
Received in revised form
2 December 2009
Accepted 3 December 2009
Available online 16 December 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Photochromic indolinobenzospiropyran
Homopolymer
Ring-opening metathesis polymerization
Grubbs' catalyst
Number-average molecular weights
1. Introduction
such polymeric photochromic systems comprise polymer matrices
that are either doped or side-chain-modified with photochromes to
Photo- and thermochromic spiropyrans (SP) have recently
received considerable attention owing to their potential application
in many new technologies, such as data recording and storage,
optical switching, displays and nonlinear optics [1,2]. Despite the
potential applications of photochromic SP's, earlier studies mainly
focused on evaluating the utility of monomeric SP systems in
solution [3,4]. The photo- and thermochromic behaviour of mono-
meric spiropyrans is based on an equilibrium between the colorless
“closed” spiropyran form and the colored “open” merocyanine (MC)
form. Their photo- and thermochromic behaviour is normally based
on UV irradiation promoting the opening of the spiro ring form to
produce the colored MC species and photo and/or thermal relaxa-
tion regenerating the SP as in Fig. 1.
display photochromic behaviour [5e8]. Therefore, the concentra-
tion of photochromic component is low in the polymer and so the
photochromic processes are weak. The use of homopolymers
increases the concentration of the photochromic component
in the polymer, which is desirable for many photochromic
processes.
Ring-opening metathesis polymerization (ROMP) is a well-
known polymerization method in which strained cyclic olefins (e.g.
norbornene, 7-oxonorbornene) are polymerized in the presence
of a metathesis catalyst [9]. In this work, the second generation
catalyst, benzylidene [1,3-bis(2,4,6-trimethylphenyl)-2-imidazoli-
dinylidene]dichloro-(tricyclohexylphosphine)ruthenium, was used
as the Grubbs' catalyst [10,11]. As one phosphine ligand is replaced
by N-heterocyclic carbene (NHC) and ruthenium is coordinated to
the two carbene groups, the second generation catalyst becomes
highly active and oxygen/water sensitive. Therefore this catalyst
needs to be handled under a nitrogen or argon, with a big caution
(see MSDAS data provided by Aldrich). The ROMP technique has
become very popular owing to the mild reaction conditions
employed and their compatibility with a wide range of functional
groups [12]. Additionally, as the polymer chain length can readily
In the context of the practical applications, such as films, sheets,
fibres, etc., polymeric rather than photochromic materials are
preferred. Although various photochromic polymers that comprise
spiropyran or other photochromic derivatives have been reported,
* Corresponding author. Tel.: þ82 41 860 1332; fax: þ82 41 865 5396.
E-mail address: keum@korea.ac.kr (S.-R. Keum).
0143-7208/$ e see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2009.12.002

S.-R. Keum et al. / Dyes and Pigments 86 (2010) 74e80
75
according to the known method [12]. The reaction mixture was
cooled to room temperature and the precipitate filtered, washed
with water and dried in vacuo to obtain compound 2 as a white
solid with a yield of 68% (2.10 g, 8.16 mmol). Mp ¼ 171.9 ꢂC; 1H NMR
NO2
hv1
N
O
NO2
Δ
2
N
R
O
(300 MHz, DMSO-d6)
6.83 (d, J ¼ 8.75 Hz, 2H),
1H); 13C NMR (75.49 MHz, DMSO-d6)
d 3.02 (s, 2H), d 5.21(s, 2H), d 6.58 (s, 2H),
R
MC
SP
d
d
6.95 (d, J ¼ 8.75 Hz, 2H),
d
9.71 (s, OH,
d
175.9 (C), 157.3 (C), 136.5
Fig. 1. Photo- and thermochromic behaviour of monomeric spiropyrans.
(CH), 127.9 (C), 123.2 (CH), 115.4 (C), 80.7 (CH), 47.2 (CH); IR
(acetone, cmꢁ1): 3328 (m, nOH), 3101 (w,
n
]CeH), 2924 (w, namine),
1772 (m, nimide), 1693 (s, nCO), 1610 (m, naromatic), 1448 (m, naromatic);
MS (EI): (m/z) 257 [M]þ, 189 [MeC4H4O]þ.
be adjusted to vary the catalyst:substrate stoichiometry, this
makes the ROMP method an attractive choice to complement the
photochromic versatility of the spiropyran photochrome.
In this paper, the novel photochromic spiropyran homopoly-
mers, P1eP3, were prepared via the ROMP of the strained bicyclic
olefinated indolinobenzospiropyrans derivatives (Fig. 2).
2.2. Synthesis of 3-chloromethyl-5-nitrosalicylaldehyde 4
5-Nitrosalicylaldehyde(2.00 g, 12.0 mmol) was dissolved in dry
chloromethyl methyl ether (20 mL), to which sublimed aluminum
trichloride (caution: reacts violently with water; prolonged storage
may lead to pressure build-up; incompatible with alcohols and
many other materials; 8.01 g, 60.0 mmol) was added under
a nitrogen atmosphere, according to the reported method [13]. The
reaction mixture was stirred for an hour at room temperature and
then refluxed for 2.5 h after which time, ice-cooled water was
added and the resulting off-white residue was recrystallized from
hot hexane solution (500 mL), yielding colorless needles of
compound 4 with a 66% yield (1.86 g, 8.63 mmol). Mp ¼ 95 ꢂC; 1H
2. Experimental
All reagents used were purchased from Aldrich. 1,3-bis-
(2,4,6-trimethylphenyl-2-imidazolidin
ylidene)dichloro(phenyl-
methylene)e(hexylphosphine)ruthenium was purchased from
Aldrich and was stored and weighed under a nitrogen atmosphere.
Dichloroethane used for the ROMP reaction was degassed using the
FreezeePumpeThaw method [12] THF distilled over sodium
chloride was distilled over calcium hydride before use. All other
solvents were used as received. Column chromatography was
performed using the silica gel 60 (230e400 mesh) from Merck.
Melting points were determined using a FischereJones melting
point apparatus and were uncorrected. The 1H nuclear magnetic
resonance (NMR) spectra were obtained using a Bruker AMX-300
spectrometer in DMSO-d6. The IR spectra were taken with an Analet
Instrument FT-IR (MAP-60) spectrometer using KBr pellets. The
UVevis absorption spectra were recorded using a Varian Cary 1E
UVeVis spectrophotometer. Photoirradiation was accomplished
using a mercury lamp (Ushio, 1 ꢀ 10ꢁ3 m2 kg sꢁ3) as the excitation
light source. The GPC analyses (calibrated by polystyrene) were
performed on the THF solutions of the polymers using a Waters 515
HPLC pump and a 2410 refractive index or a 486 tunable absorbance
detector at a flow rate of 1.0 mL/min through a 7.8 ꢀ 300 mm
column at 30 ꢂC.
NMR (300 MHz, CDCl3):
d 4.7 (s, CH2Cl, 2H), d 8.5 (s, aromatic, 2H),
d
10.0 (s, CHO, 1H),
d
12.1 (s, OH, 1H); IR (acetone, cmꢁ1): 3080
(w, nOH), 2871 (w, nCeH), 1663 (s, nCHO), 1625 (m, naromatic), 1532
(m, nasNO), 1440 (m, naromatic), 1346 (s, nsNO).
2.3. Synthesis of 1-(2-carboxyethyl)-2,3,3-trimetyl-3H-indolium
bromide 6 and 1-(2-carboxypentyl)-2,3,3-trimetyl-3H-indolium
bromide 7
A mixture of 2,3,3-trimethyl-3H-indole (3 g, 18.84 mmol) 5 and
3-bromo-propionic acid (3.6 g, 23.53 mmol) or 6-bromohexanoic
acid (4.6 g, 23.58 mmol) was heated to 80 ꢂC for 12 h, according to
the known method [14]. During this time, the highly viscous
product came out of the solution; upon cooling, the reaction
mixture was extracted with 200 mL of Et2O three times to remove
unreacted starting material. The remaining crystalline solid was
dissolved in 10 mL of water and extracted three times each with
50 mL of Et2O and 25 mL of CH2Cl2. The aqueous layer was sepa-
rated and concentrated under vacuum (1.0 mmHg, 24 h) until it was
dry. The resulting solid was crystallized from CH2Cl2 (20 mL) to
compound 6 or 7 in the form of a pale pink solid.
2.1. Synthesis of exo-N-(p-hydroxyphenyl)-3,6-epoxy-
4-cyclohexene-1,2-dicarboximide 2
A mixture of 7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic
anhydride 1 (caution: avoid contact with water/moisture and
oxidants; 2.0 g, 12 mmol) and p-aminophenol (1.31 g, 12 mmol)
were heated at reflux for 10 min in glacial acetic acid (3 mL),
6: Yield 66%; Mp ¼ 81.3 ꢂC; 1H NMR (300 MHz, DMSO-d6):
d 1.53
(s, 6H),
2H),
d
2.71 (t, J ¼ 7.2 Hz, 2H),
d
2.87 (s, 3H),
d
4.66 (t, J ¼ 7.6 Hz,
7.99 (d,
196.5 (C), 177.3
d
7.59e7.62 (m, 2H),
d
7.83 (d, J ¼ 9.3 Hz, 1H),
d
J ¼ 9.3 Hz, 1H); 13C NMR (75.49 MHz, DMSO-d6):
d
(C), 148.0 (C), 141.7 (C), 128.5 (CH), 126.2 (CH), 126.0 (CH), 125.7
(CH), 47.1 (CH2), 31.6 (CH2), 22.0 (CH3), 14.0 (CH3); IR (acetone,
cmꢁ1): 3398 (w, nOH), 2972 (m, nCeH),1724 (s, nCOOH); Anal. Calcd. for
C14H18NO2; C, 72.39; H, 7.81; N, 6.03; O, 13.77, Found; C, 72.18;
H, 7.79; N, 6.21; O, 13.82.
Ph
O
N
O
NO2
N
O
NO2
Ph
O
O
m
O
N
O
O
N
O O
7: Yield 48%; Mp ¼ 81.3 ꢂC;
d
1.6 (s, 6H),
4.45 (t, J ¼ 7.6 Hz, 2H),
7.87 (d, J ¼ 9.3 Hz,
196.5 (C), 174.2 (C), 141.8
d 1.51e1,85 (m, 6H),
O
Hn
n
P2a-c, P3a-c
P1a-c
d
d
2.24 (t, J ¼ 7.2 Hz, 2H),
d 2.87 (s, 3H), d
H
7.26e7.64 (m, 2H),
d
7.78 (d, J ¼ 9.3 Hz, 1H),
d
P2: m=1 & P3: m=4
1H); 13C NMR (75.49 MHz, DMSO-d6):
d
a : n = 25, b: n = 50, c: n = 100
(C), 141.0 (C), 129.3 (CH), 128.9 (CH), 123.5 (CH), 115.4 (CH), 54.1 (C),
47.4 (CH2), 33.3 (CH2), 26.9 (CH2), 25.4 (CH2), 24.0 (CH2), 22.0
(CH3), 14.0 (CH3); IR (acetone, cmꢁ1): 3398 (w, nOH), 2972 (m, nCeH),
1724 (s, nCOOH); Anal. Calcd. for C17H24NO2; C, 74.42; H, 8.82; N, 5.10;
O, 11.66, Found; C, 74.52; H, 8.90; N, 5.24; O, 11.34.
Fig. 2. General structure of the polymer prepared via ROMP of the strained bicyclic
olefinated indolinobenzospiropyran derivatives. aec denote the polymers prepared
with three different catalyst-to-substrate stoichiometries (n
¼
25, 50 & 100,
respectively).

76
S.-R. Keum et al. / Dyes and Pigments 86 (2010) 74e80
2.4. Synthesis of 1,3,3-trimethyl-6-nitrospiro-[(2H)-
1-benzopyran-2,2-indoline] derivatives SP1eSP3
in acetonitrile (80 mL), and then 8-chloromethyl-1,3,3-trimethyl-
6-nitrospiro-[(2H)-1-benzopyran-2,2-indoline] SP1 (500 mg,
1.35 mmol) was added. The reaction mixture was heated at 70 ꢂC
for 24 h in the dark. After evaporation of the solvent, the resulting
red wax was purified using silicagel column chromatography in the
dark with a mixture of ethylacetate/hexane (2/1). The product was
recrystallized from a mixture of dichloromethane/hexane (1/10) to
form the violet colored material SPM1 with a yield of 17% (140 mg,
The indolinobenzospiropyran derivatives SP1eSP3 were
prepared by the reaction of 1,3,3-trimethyl-2-methyleneindoline
(FB) in acetone and an acetone solution of 3-chloromethyl-
5-nitrosalicylaldehyde, using a 1:1 mol ratio, employing a method
adapted from the known method [4].
A representative example of this method is the following: 1,3,3-
Trimethyl-2-methyleneindoline (400 mg, 2.31 mmol) in acetone
(20 mL) was added to the acetone solution (60 mL) of 3-chlor-
omethyl-5-nitrosalicylaldehyde (500 mg, 2.32 mmol). The reaction
mixture was heated at 40 ꢂC for 12 h in the dark. After evaporation
of the solvent, the resulting red wax was purified using silicagel
column chromatography in the dark with a mixture of ethylacetate/
hexane (1/60). The resulting yellow solid was recrystallized from
a mixture of CH2Cl2/hexane (1/10) to form pure products.
0.236 mmol). Mp ¼ 147.4 ꢂC; 1H NMR (300 MHz, DMSO-d6):
d
1.21
4.81
(s, 3H),
(s, 2H),
d
1.30 (s, 3H),
5.38 (s, 2H),
6.66 (s, J ¼ 7.8 Hz, 1H),
6.96 (d, J ¼ 7.8 Hz, 1H),
7.10 (d, J ¼ 8.75 Hz, 2H), 7.16 (t, J ¼ 7.8 Hz, 1H),
8.23 (s,1H); 13C NMR (75.49 MHz, DMSO-d6):
176.1 (C),160.1 (C),
d 2.71 (s, NeMe, 3H), d 2.72 (s, 2H), d
d
d
5.91 (d, J ¼ 10.2 Hz, 1H),
6.80 (d, J ¼ 7.5 Hz, 1H),
7.05 (d, J ¼ 8.75 Hz, 1H),
8.00 (s, 1H),
d
6.58 (s, J ¼ 7.8 Hz,
2H),
d
d
d
6.86 (t,
J ¼ 10.2 Hz, 1H),
d
d
d
d
d
d
d
156.2 (C), 147.6 (C), 141.0 (C), 137.5 (CH), 136.3 (C), 128.9 (C), 128.1
(C), 127.9, (CH), 126.9 (CH), 126.8 (CH), 125.9 (CH), 123.3 (C), 122.7
(CH), 121.8 (CH), 118.8 (CH), 118.9 (C), 115.4 (CH), 115.1 (CH), 106.6
(C), 80.9 (CH), 60.4 (CH2), 52.4 (C), 47.3 (CH), 29.2 (CH3), 26.0 (CH3),
SP1: yellow cubes; 38% yield; Mp ¼ 137.3 ꢂC; 1H NMR (300 MHz,
CDCl3):
J ¼ 7.5 Hz, 2H),
6.78 (d, J ¼ 10.2 Hz, 1H),
J ¼ 7.8 Hz, 1H), 7.19 (t, J ¼ 7.8 Hz, 1H),
13C NMR (75.49 MHz, DMSO-d6):
160.1 (C), 147.8 (C), 140.2 (C),
d 1.19 (s, 3H), d 1.32 (s, 3H), d 2.75 (s, 3H), d 4.35 (d,
d
5.88 (d, J ¼ 10.2 Hz, 1H),
6.89 (t, J ¼ 7.5 Hz, 1H),
8.00 (s, 1H), 8.14 (s, 1H);
d
6.56 (d, J ¼ 7.8 Hz, 1H),
20.1 (CH3); IR (acetone, cmꢁ1): 3078 (w,
n]CeH), 2958 (w, nCeH),
d
d
d
6.96 (d,
2855 (w, namine), 1776 (w, nimide), 1707 (s, nCO), 1608 (m, naromatic),
1511 (s, nasNO), 1450 (m, naromatic), 1335 (s, nsNO); Anal. Calcd. for
C34H29N3O7; C, 69.03; H, 4.94; N, 7.10; O, 18.93, Found; C, 68.94; H,
5.04; N, 6.97; O, 19.05.
d
d
d
d
136.2 (C), 127.9, (CH), 127.0 (CH), 126.8 (CH), 126.0 (CH), 124.3 (C),
122.8 (CH), 121.8 (CH), 119.9 (CH), 118.8 (C), 115.2 (CH), 52.4 (C), 40.8
(CH2), 29.0 (CH3), 26.0 (CH3), 20.1 (CH3); IR (acetone, cmꢁ1): 3052
2.6. Synthesis of the strained bicyclic olefinated SP-monomers
SPM2eSPM3
(w, n]CeH), 2970 (w, nCeH), 2869 (w, namine), 1609 (m, naromatic), 1520
(m, nasNO), 1448 (m, naromatic), 1335 (s, nsNO); m/z (ESI): 335.1 (100%
[MeCl]þ); Anal. Calcd. for C20H19ClN2O3; C, 64.78; H, 5.16; Cl, 9.56;
N, 7.55; O, 12.94, Found; C, 64.34; H, 5.37; Cl, 10.21; N, 7.76; O,12.32.
SP2: green solid; yield 56%; Mp ¼ 211.4 ꢂC; 1H NMR (300 MHz,
The strained bicyclic olefinated SP-monomers SPM2 and SPM3
were prepared from the reaction of exo-N-(p-hydroxyphenyl)-
3,6-epoxy-4-cyclohexene-1,2-dicarboximide 2 with SP2 or SP3 in
the presence of DCC and DMAP in THF, according to the reported
method [15].
DMSO-d6):
2H), 3.31e3.54 (m, 2H),
6.78 (d, J ¼ 10.2 Hz, 1H),
7.11 (d, J ¼ 7.5 Hz,1H),
8.04 (d, J ¼ 7.8 Hz, 1H),
8.21 (s, 1H); 13C NMR (75.49 MHz,
159.9 (C), 147.8 (C), 140.9 (C), 136.2 (C), 127.9, (CH),
d
1.18 (s, 3H),
d
1.32 (s, 3H),
6.00 (d, J ¼ 10.2 Hz, 1H),
6.80 (t, J ¼ 7.5 Hz, 1H),
7.19 (d, J ¼ 7.8 Hz,
d
2.40e2.63 (m, Ne1eCH2,
d
d
d
6.66 (d,
J ¼ 7.8 Hz, 1H),
d
d
d
6.96 (d, J ¼ 7.8 Hz,1H),
d
d
a
1H),
d
d
O
O
H
H
H
p-H2NC6H4OH
DMSO-d6):
d
O
O
O
N
OH
AcOH , reflux , 68%
127.0 (CH), 126.0 (CH), 122.8 (CH), 121.8 (CH), 121.7 (CH), 119.9 (CH),
118.8 (CH), 115.6 (CH), 115.2 (CH), 106.5 (CH), 52.4 (C), 38.0 (CH2),
36.4 (CH2), 26.0 (CH3), 20.1 (CH3),; IR (acetone, cmꢁ1): 2969 (w,
nCeH), 2869 (w, namine), 1707 (s, nCOOH), 1606 (w, naromatic), 1508 (m,
nasNO), 1440(m, naromatic), 1328 (s, nsNO); Anal. Calcd. for C21H20N2O5;
C, 66.31; H, 5.30; N, 7.36; O, 21.03, Found; C, 66.50; H, 5.19; N, 7.41;
O, 20.90.
H
O
O
2
1
O
OH
O
OH
AlCl3,
N
ClCH2OCH3
H
H
Cl
N
O
NO2
reflux, 66%
Acetone, 40 o
38%
C
NO2
NO2
Cl
3
SP1
4
SP3: pink solid; yield 49.74% (1.9 g, 4.5 mmol). Mp ¼ 211.4 ꢂC; 1H
NMR (300 MHz, CDCl3):
d
1.07 (s, 3H),
d
1.18 (s, 3H),
3.31e3.54 (m, 2H), d
d
1.52e1.65 (m,
6.00
6.80 (t, J ¼ 7.8 Hz,1H),
6.96 (d, J ¼ 7.8 Hz, 1H), 7.11
7.19 (t, J ¼ 7.8 Hz, 1H), 8.04 (d, J ¼ 7.8 Hz, 1H),
8.21 (s, 1H); 13C NMR (75.49 MHz, DMSO-d6):
159.8 (C), 147.8
6H),
(d, J ¼ 10.2 Hz,1H),
6.86 (d, J ¼ 10.2 Hz, 1H),
(d, J ¼ 7.5 Hz, 1H),
d
2.40e2.63 (m, N1eCH2, 2H),
d
2, K2CO3
N
O
NO2
d
6.66 (d, J ¼ 7.8 Hz,1H),
d
O
AcCN, reflux
17%
H
d
d
d
O
O
N
SP Monomer
SPM1
d
d
H
O
d
d
(C), 140.9 (C), 136.2 (C), 127.9, (CH), 127.0 (CH), 126.0 (CH), 122.8
(CH), 121.8 (CH), 121.7 (CH), 119.9 (CH), 118.8 (CH), 115.6 (CH), 115.2
(CH), 106.5 (CH), 52.4 (C), 43.7 (CH2), 36.1 (CH2), 28.4 (CH2), 26.8
(CH2), 26.0 (CH3), 24.5 (CH2), 20.1 (CH3); IR (acetone, cmꢁ1): 2969
(w, nCeH), 2869 (w, namine), 1707 (s, nCOOH), 1606 (w, naromatic), 1508
(m, nasNO), 14,401(m, naromatic), 1328 (s, nsNO); Anal. Calcd. for
C24H26N2O5; C, 68.23; H, 6.20; N, 6.63; O, 18.94, Found; C, 68.31; H,
6.32; N, 6.56; O, 18.81.
b
3, TEA
Br(CH2)m+1COOH
reflux, 66%
N
O
NO2
N+Br-
EtOH, reflux
56%
N
m
m
5
6, 7
O
OH
O
OH
SP2 & SP3
2, DCC,
DMAP
N
O
NO2
O
2.5. Synthesis of the strained bicyclic olefinated SP-monomer SPM1
SP Monomer
SPM2 (m=1) & SPM3 (m=4)
H
H
m
THF, 64%
O
O
O
N
O
A
mixture of exo-N-(p-hydroxyphenyl)-3,6-epoxy-4-cyclo-
hexene-1,2-dicarboximide (347 mg, 1.35 mmol) 2 and potassium
carbonate (93 mg, 0.673 mmol) were heated under reflux for 1 h
Fig. 3. Synthetic procedures for a) SPM1 and b) SPM2eSPM3.

S.-R. Keum et al. / Dyes and Pigments 86 (2010) 74e80
77
3
N
N
6
N
N
NO2
O
1)
Cl
Cl
Ru
in MC
Ph
8
SPM1
P(Cy)3
Photochromic polymers
Photochromic SP
SP1, SP2 & SP3
P1, P2 & P3
2) Ethylvinylether
53 ~ 83 %
ROMP
NO2
O
SPM2 & SPM3
O
O
O
N
O
SP-based strained olefin
Fig. 4. Synthetic procedures for polymers P1eP3 via the ROMP.
A representative example of this method is the following: SP2
(0.87 g, 2.29 mmol) and 2 (0.59 g, 2.29 mmol) were placed in a 250-
mL round-bottomed flask. After the solution was dissolved in dry
THF (30 mL) and cooled to 0 ꢂC, a solution of DCC (0.57 g,
2.76 mmol) and DMAP (0.12 g, 0.98 mmol) in THF (10 mL) was
added dropwise over the course of 1 h. The mixture was stirred at
0 ꢂC for an additional 2 h and then gradually warmed to 25 ꢂC over
the course of 24 h. During the warming period, a dicyclohexyl urea
(DCU) precipitate formed, which was filtered and washed with THF
(3 ꢀ 50 mL). After the filtrate was evaporated, the resulting red wax
was purified using silicagel column chromatography in the dark
with a mixture of ethylacetate/dichloromethane/hexane (1/5/1).
The solution was recrystallized from a mixture of dichloromethane/
hexane (1/10) to form the products.
d
d
2.76e3.02 (m, NeCH2, 2H),
5.38 (s, 2H),
5.90 (d, J ¼ 10.2 Hz, 1H),
6.80 (t, J ¼ 7.8 Hz, 1H), 6.86 (d, J ¼ 10.2 Hz, 1H),
6.96 (d, J ¼ 7.8 Hz, 1H), 7.05 (d, J ¼ 8.75 Hz, 2H), 7.10 (d,
7.11 (d, J ¼ 7.5 Hz, 1H), 7.19 (t, J ¼ 7.8 Hz, 1H),
8.21 (s,1H); 13C NMR (75.49 MHz, DMSO-
175.4 (C), 175.1 (C), 159.9 (C), 156.2 (C), 147.8 (C), 140.8 (C),
d
3.01 (s, 2H),
d
3.55e3.81 (m, 2H),
d
d 6.58 (s, 2H), d 6.67 (d,
J ¼ 7.8 Hz, 1H),
d
d
d
d
J ¼ 8.75 Hz, 2H),
d
d
d
8.04 (d, J ¼ 7.8 Hz,1H),
d
d6):
d
138.5 (CH), 136.3 (C), 129.1 (C), 128.1 (CH), 127.0 (CH), 126.1 (CH),
123.0 (CH), 122.9 (CH), 121.8 (CH), 121.7 (CH), 119.9 (CH), 118.9 (CH),
115.6 (CH), 115.3 (CH), 115.2 (CH), 106.5 (CH), 80.7 (CH), 52.3 (C),
47.6 (CH), 43.9 (CH2), 36.2 (CH2), 29.2 (CH2), 26.8 (CH2), 24.4 (CH2),
26.0 (CH3), 20.1 (CH3); IR (acetone, cmꢁ1): 3071 (w,
n]CeH), 2967
(w, nCeH), 2869 (w, namine), 1757 (m, nimide), 1711 (s, nCO), 1610 (w,
naromatic), 1508 (m, nasNO), 1481(m, naromatic), 1337 (m, nsNO); Anal.
Calcd. for C38H35N3O8; C, 68.97; H, 5.33; N, 6.35; O, 19.34, Found;
C, 69.05; H, 5.46; N, 6.47; O, 19.02.
SPM2: green colored; yield 64%; Mp ¼ 124.4 ꢂC; 1H NMR
(300 MHz, CDCl3):
d
1.16 (s, 3H),
d
1.27 (s, 3H),
d
2.72 (s, 2H),
d
d
d
2.76e3.02 (m, NeCH2, 2H),
d
3.55e3.81 (m, 2H), d 5.38 (s, 2H),
5.90 (d, J ¼ 10.2 Hz, 1H),
d
6.58 (s, 2H),
d
6.67 (d, J ¼ 7.8 Hz, 1H),
6.96 (d,
7.10 (d, J ¼ 8.75 Hz, 2H),
7.19 (t, J ¼ 7.8 Hz, 1H), 8.04 (d, J ¼ 7.8 Hz,
8.21 (s, 1H); 13C NMR (75.49 MHz, DMSO-d6):
176.2 (C),
2.7. Synthesis of spiropyran-based homopolymer P1eP3
6.80 (t, J ¼ 7.8 Hz, 1H),
d
6.86 (d, J ¼ 10.2 Hz, 1H),
d
J ¼ 7.8 Hz, 1H),
d
7.05 (d, J ¼ 8.75 Hz, 2H),
d
In a typical procedure, a solution of the monomer SPM1e3 in
rigorously inert CH2Cl2 was poured into a CH2Cl2 solution of
(1,3-bis-(2,4,6-trimethylphenyl)-2-imimidazolidinylidene)dichloro
(phenylmethylene)(tricyclohexylphosphine)ruthenium (0.01, 0.02
and 0.04 equivalents for a, b & c, respectively) in a Schlenk tube
[10,12]. The final monomer concentrations were all 5 mM. Excess
ethyl vinyl ether was added after stirring at room temperature for
14 h and then the solutions were stirred while exposed to the
atmosphere for 30 min. The polymers were precipitated by pouring
the reaction solutions into cold ether and collecting the precipitates
using vacuum filtration.
d
7.11 (d, J ¼ 7.5 Hz, 1H),
d
d
1H),
d
d
175.3 (C), 159.9 (C), 156.2 (C), 148.0 (C), 140.9 (C), 138.5 (CH), 136.3
(C), 128.9, (CH), 127.9 (CH), 127.0 (CH), 126.0 (CH), 123.3 (CH), 122.8
(CH), 121.8 (CH), 121.7 (CH), 119.8 (CH), 118.8 (CH), 115.6 (CH), 115.4
(CH), 115.2 (CH), 106.4 (CH), 80.8 (CH), 52.4 (C), 47.5 (CH), 38.0
(CH2), 36.4 (CH2), 26.0 (CH3), 20.1 (CH3); IR (acetone, cmꢁ1): 3071
(w, n]CeH), 2967 (w, nCeH), 2869 (w, namine), 1757 (m, nimide), 1711
(s, nCO), 1610 (w, naromatic), 1508 (m, nasNO), 1481(m, naromatic), 1337
(m, nsNO); Anal. Calcd. for C35H29N3O8; C, 67.84; H, 4.72; N, 6.78; O,
20.66, Found; 67.68; H, 4.63; N, 6.48; O, 21.21.
SPM3: green colored; yield 44%; Mp ¼ 124.4 ꢂC; 1H NMR
Table 2
UVevisible spectroscopic data for spiropyrans SP1e3 and their corresponding
monomers SPM1eSPM3 and polymers P1eP3.
(300 MHz, CDCl3):
d
1.16 (s, 3H),
d
1.27 (s, 3H),
d
1.52e1.65 (m, 6H),
Table 1
Compounds
lmax/nm
Color of the
MC form
(3
ꢀ 10ꢁ4 L molꢁ1 cmꢁ1
)
Polymerization yields and polymer characterization.
Monomer (equivalents)a
% yield
Mw
10,089
Mn
PDI (Mw/Mn)
SP form
MC form
SP1
SPM1
P1c
261 (0.449)
261 (0.155)
267 (1.594)
549 (0.307)
545 (0.412)
554 (0.468)
Reddish
Reddish
Reddish
P1a (25)
P1b (50)
P1c (100)
P2a (25)
P2b (50)
P2c (100)
P3a (25)
P3b (50)
P3c (100)
78
83
82
74
76
79
53
57
64
27,261
51,890
1,21,266
68,817
1,91,827
4,28,589
21,902
2.74
3.67
3.92
2.85
2.77
2.80
1.73
2.18
2.04
14,131
30,971
24,121
69,224
1,52,961
12,654
12,926
15,785
SP2
SPM2
P2c
266 (0.114)
264 (0.127)
276 (3.796)
548 (0.448)
551 (0.224)
572 (0.296)
Purple
Purple
Purple
28,205
32,309
SP3
SPM3
P3c
265 (0.229)
265 (0.842)
271 (2.973)
543 (0.171)
544 (0.656)
570 (0.488)
Purple
Purple
Purple
a
Relative to the molar equivalents of catalyst used.

78
S.-R. Keum et al. / Dyes and Pigments 86 (2010) 74e80
A 0.8
C1.0
B0.8
P1c
SPM1
SP1
0.7
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.8
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.6
0.4
0.2
0.0
545nm
554nm
549nm
400
500
Wavelength (nm)
600
700
300
400 500
Wavelength (nm)
600
700
300
400 500
Wavelength (nm)
600
700
Fig. 5. UVevis spectroscopic behaviors of SP1 (A), monomer SPM1 (B) in EtOH (3.03 ꢀ 10ꢁ5 M) and polymer P1c (C) in DMF (1.07 ꢀ 10ꢁ5 M) in every 3 min after UV light irradiation.
P1aec: Yields: 78% for P1a, 83% for P1b, and 82% for P1c, 1H
NMR (300 MHz, CDCl3): 8.10 (br s), 7.93 (br s), 7.02 (m), 6.78
(m), 6.47 (br s), 6.11 (br s), 5.86 (br s), 4.74(m), 3.42 (br s),
2.7 (br s), 1.59 (br s), 1.25 (br s).
P2aec: Yields: 74% for P2a, 76% for P2b, and 79% for P2c, 1H
NMR (300 MHz, CDCl3): 7.93 (br s), 7.20 (m), 7.07 (m), 7.03
(m), 6.87 (br s), 6.64 (br s), 6.07 (br s), 5.84(br s), 3.69 (m),
3.58 (m), 3.42 (br s), 2.79 (m), 1.25 (br s), 1.12 (br s).
P3aec: Yields: 53% for P3a, 57% for P3b, and 64% for P3c, 1H
NMR (300 MHz, CDCl3): 7.94 (br s), 7.10 (m), 7.07 (m), 6.84
(br s), 6.69 (br s), 6.56 (br s), 6.10 (br s), 5.84(br s), 5.18 (m),
4.63(m), 3.74 (m), 3.45 (br s), 3.15 (br s), 2.49 (m), 1.69
(br s), 1.59 (br s), 1.40 (m), 1.25 (br s), 1.14 (br s).
The polymerization of the three monomers SPM1eSPM3, which
were obtained from the corresponding precursors SP1eSP3, relied
on the presence of the strained bicyclic olefins 5 in order to facili-
tate the ROMP process and generate the polymers P1eP3. Polymer
P1 was connected to a strained olefin fragment with an alkyl ether
group on the 8-position of the spiropyran moiety, whereas poly-
mers P2 and P3 were both connected on the ring nitrogen of the
indole group with a carboxylic linkage. Polymers P2 and P3 differed
only in the length of the N-alkyl chain of the indole group, which
led to a difference in the distance between the polymer backbone
and the photochromic pendant.
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
3.1. Synthesis of the strained bicyclic olefinated spiropyrans
(monomers)
3. Results and discussion
Fig. 3a and b shows the detailed processes for the synthesis of
the strained bicyclic olefinated spiropyrans (monomers) of SPM1
and SPM2, respectively. These monomers were then polymerized
using the ROMP technique.
The second generation Grubbs' catalyst, benzylidene[1,3-
bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(tricyclo-
hexylphosphine)ruthenium, was used in this work. Unlike the first
generation catalyst, one phosphine ligand was replaced with N-
heterocyclic carbene (NHC), and ruthenium was coordinated to the
two NHC groups. This catalyst was very highly active and oxygen/
water sensitive and therefore, had to be handled under a nitrogen or
argon atmosphere.
The strained bicyclic olefin, 7-oxanorbornene 2, was readily
prepared with a good yield using a known procedure, [12] through
the condensation of 7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic
anhydride 1 with p-aminophenol. Chloromethylated spiropyran SP1
was prepared from the reaction of 1,3,3-trimethyl-2-methyleneindo-
line (Fischer base) and 3-chloromethyl-5-nitrosalicylaldehyde 4,
which was obtained from the reaction of 5-nitrosalicylaldehyde 3 with
chloromethyl methyl ether, according to a known method [13].
The N-carboxy alkylated spiropyran-based monomers SPM2
(m ¼ 1) and SPM3 (m ¼ 4) were then obtained from the reaction of
the carboxyethylated indolium compounds 6 & 7, respectively, with
compound 3 in the presence of TEA. The carboxyethylated indolium
compounds 6 & 7 were prepared through the reaction of 2,3,3-
trimethyl-3H-indole 5 with 3-bromo-propionic acid and 6-bro-
mohaxanonic acid, respectively, according to a previously reported
method [16].
7
6
P1c
P3c
5
4
P2c
3
2
1
3.2. Synthesis and characterization of polymers P1e3
Monomers M1eM3 were subjected to the ROMP conditions in
Fig. 4.
A CH2Cl2 solution of commercially available (1,3-bis-(2,4,6-tri-
methylphenyl)-2-imidazolidinylidene)dichloro(phenylmethylene)
(tricyclohexylphosphine)ruthenium (Grubbs' 2nd catalyst) is can-
nulated into a vigorously stirred CH2Cl2 solution of the appropriate
monomer under anhydrous conditions in a typical polymerization
procedure [10,11]. The resulting homogeneous solution was stirred
for 14 h at room temperature, and then the polymerization was
0
50
100
Time (min)
150
200
Fig. 6. The first-order kinetic treatment for the thermal isomerization of polymers
P1eP3 by plotting ꢁln(Aꢂ ꢁ A) against time, where A and Aꢂ denotes the absorbance at
time t and infinite time.

S.-R. Keum et al. / Dyes and Pigments 86 (2010) 74e80
79
Table 3
movement can be somewhat restrained, which makes it more
difficult to be converted into the open form.
Ring-formation rates of the open chain merocyanine forms of SP-monomers
SPM1eSPM3 and their corresponding polymers P1eP3.
The rate of reversion to the colorless spiro ring (MC / SP) was
measured after UV irradiation in EtOH and DMF for the monomer
SPM1 and the polymers P1e3, respectively, by following the
disappearance of the absorption band in the 540e570 nm region.
The decay rate of the photo-induced colored transients obeyed
good first-order kinetics for all substrates examined in this work.
The first-order kinetic treatments for the thermal isomerization of
polymers P1eP3 are shown in Fig. 6, by plotting ꢁln(Aꢂ ꢁ A)
against time, where A and Aꢂ denotes the absorbance at time t and
infinite time.
Compounds
kobs ꢀ 10ꢁ2
t1/2
(min)
N
r
Wavelengths
followed (nm)
Solvent
EtOH
(sꢁ1
)
SPM1
SPM2
SPM3
2.87
7.41
3.41
24.1
9.35
20.3
9
8
10
0.999
0.999
0.999
545
551
544
P1c
P2c
P3c
7.96
14.4
2.22
8.71
4.81
31.2
7
8
7
0.997
0.992
0.998
554
572
570
DMF
The rate constants, kobs, of the ring-formation of opened mer-
ocyanine forms are 2.87e7.41 ꢀ 10ꢁ2 sꢁ1 and 2.22e14.4 ꢀ 10ꢁ2 sꢁ1
,
terminated by quenching the reaction mixtures with excess ethyl
vinyl ether. The homopolymers were conveniently isolated in their
pure forms by precipitating them from the cold ether and then
washing them with the same solvent to remove the catalyst and
any unreacted monomer.
The chain length of the polymers could be tailored by varying
the relative molar ratios between the monomer SPM1 and the
ROMP catalyst used. Three different polymers P1aec were
prepared from the same monomer SPM1.
for the monomer SPM1e3 and the polymers P1e3, respectively.
These are summarized in Table 3.
4. Conclusion
Novel photochromic indolinobenzospiropyran-based homo-
polymers were prepared through the ring-opening metathesis
polymerization of the strained bicyclic indolinobenzospiropyran
derivatives. When 1, 2, and 4 mol% of the Grubbs' catalyst were
used in the ROMP reaction, the 100-mer (c), the 50-mer (b), and the
25-mer (a) were isolated, respectively. The gel permeation chro-
matography (GPC) analysis revealed that the relative ratio of the
number-average molecular weights for c:b:a was approximately
4:2:1 for P1 and P2 but not for P3. All of the prepared homopoly-
mers were soluble in common organic solvents, had high poly-
dispersity indices (PDI, Mw/Mn) in P1, P2 and P3 and retained their
photochromic properties in the polymeric systems. The PDI values
obtained are unusually high for ROMP without any clear reasons.
P1 and P3 showed excellent photochromic behaviors, while P2
(m ¼ 1) had a much weaker photochromic character, in the UVevis
spectroscopy. The UVevis absorption spectroscopic behaviors of
the polymers revealed that they retained the appealing photo-
chromism of their corresponding monomers, as an example for SP1,
SPM1 & P1 in Fig. 5.
When 1, 2, and 4 mol% of the Grubbs' catalyst were used in the
ROMP reaction, the 100-mer (P1c), the 50-mer (P1b), and the 25-
mer (P1a) were isolated, respectively. In Table 1, the gel permeation
chromatography (GPC) revealed that the relative ratio of the
number-average molecular weights, Mn, for P1c:P1b:P1a was
approximately 4:2:1, as expected from the stoichiometries
(100:50:25) used in the polymerization process. The prepared
polymers P1 and P2 showed similar tendencies, while the Mn
values of 32,300, 28,200 and 21,900 were relatively constant the P3
polymers P3c, P3b, and P3a, respectively.
The 1H NMR spectra of all of the polymers P1e3 showed
broadened peaks compared to those of the monomers and the
absence of the peak for the vinyl proton of the strained olefin. The
GPC analysis of the polymers showed extremely high poly-
dispersity indices (PDI, Mw/Mn) in P1, P2 & P3, in Table 1.
3.3. UVeVis absorption spectroscopy
Acknowledgment
Table 2 summarizes the UVevis spectroscopic properties of the
DMF solution of the novel polymers P1e3 along with those for the
EtOH solutions of spiropyrans SP1e3 and the monomeric mole-
cules SPM1e3, for comparison.
This work was supported by the Korea Research Foundation
(KRF) grant funded by the Korea government (MEST) (No. 2009-
0071425) and partly by the Brain Korea 21 project.
Photoinduced SP ¼ MC isomerization was observed for all of the
compounds studied at 335 nm with a short-wavelength UV lamp.
All of the polymers showed typical absorbances for the colored-
open forms of the spiropyran photochrome at 550e570 nm. Spec-
tral changes were monitored in the UVevisible region after UV light
irradiation in Fig. 5.
After previous irradiation of UV light for a standard period,
interception produced a gradual decrease in the absorbances cor-
responding to the open form of the spiropyran photochrome at
543e572 nm. The decrease in these absorbances was accompanied
by the increase in the absorbances for the colorless closed form of
the photochrome centered at 330e350 nm.
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