Synthesis, crystal structure and photochromism of a novel spiro[indoline-naphthaline]oxazine derivative

Article abstract of DOI:10.1016/j.molstruc.2015.01.050

A new spiro[indoline-naphthaline]oxazine derivative, 12-methoxy-14,14-dimethyl-17-(piperidin-1-yl)-7,8,14,15a-tetrahydro-4bH-naphtho[1″,2″:5′,6′][1,4]oxazino[3′,2′:2,3][1,4]oxazino[4,3-a]indole (1), was successfully synthesized, and its structure was characterized by ¹H NMR, ¹³C NMR, IR, HRMS and single-crystal X-ray diffraction method. X-ray diffraction indicates that benzene and naphthalene rings of compound 1 are almost perpendicular, and the piperidine ring at the 6′-C site is in a chair conformation. In the packing diagram, a couple of short intermolecular distances such as the intermolecular short contact are observed. The photochromic properties of compound 1 have been fully investigated in different solvents, it was found that it exhibited excellent photochromism properties in solvents.

Full text of DOI:10.1016/j.molstruc.2015.01.050

Accepted Manuscript
Synthesis, Crystal Structure and Photochromism of a novel spiro [indoline-
naphthaline]oxazine deriative
Hong Li, Meili Pang, Bianpeng Wu, Jiben Meng
PII:
S0022-2860(15)00069-1
DOI:
http://dx.doi.org/10.1016/j.molstruc.2015.01.050
MOLSTR 21295
Reference:
Journal of Molecular Structure
To appear in:
Received Date:
Revised Date:
Accepted Date:
5 December 2014
27 January 2015
29 January 2015
Please cite this article as: H. Li, M. Pang, B. Wu, J. Meng, Synthesis, Crystal Structure and Photochromism of a
novel spiro [indoline-naphthaline]oxazine deriative, Journal of Molecular Structure (2015), doi: http://dx.doi.org/
10.1016/j.molstruc.2015.01.050
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Synthesis, Crystal Structure and Photochromism of a novel spiro
[indoline-naphthaline]oxazine deriative
Hong Lia Meili Panga,* Bianpeng Wub Jiben Menga
aCollege of Chemistry, Collaborative Innovation Center of Chemical Science and Engineering
(Tianjin), Nankai University, Tianjin 300071, People’s Republic of China
bCollege of Science, Tianjin Chengjian University, Tianjin 300071, People’s Republic of China
E-mail: pangmeili@nankai.edu.cn
Abstract:
A
new spiro[indoline-naphthaline]oxazine derivative, 12-methoxy-14,14-dimethyl-1
7-(piperidin-1-yl)-7,8,14,15a-tetrahydro-4bH-naphtho[1'',2'':5',6'][1,4]oxazino[3',2':2,3][1,4]oxazino[4,3-
a]indole (1), was successfully synthesized, and its structure was characterized by 1H NMR, 13C NMR, IR,
HRMS and single-crystal X-ray diffraction method. X-ray diffraction indicates that benzene and
naphthalene rings of compound 1 are almost perpendicular, and the piperidine ring at the 6’-C site is in a
chair conformation. In the packing diagram, a couple of short intermolecular distances such as the
intermolecular short contact are observed. The photochromic properties of compound 1 have been fully
investigated in different solvents, it was found that it exhibited excellent photochromism properties in
solvents.
Keywords: Crystal structure; Spiroindolinonaphthooxazine; Photochromism; Acidichromism;
Fluorescence properties
1

1. Introduction
Organic photochromic materials have been widely investigated because of their potential applications in
molecular photonic devices such as optical memories and switching devices [1-8]. Among all kinds of
photochromic compounds, because of the ability to give intense photocolouration, fast thermal
relaxation and excellent fatigue resistance, spiroindolinonaphthooxazine (SO) derivatives are most
promising candidates for applications as multifunctional optoelectronic materials [9-10]. As illustrated in
Scheme 1, the photochromism of SO derivatives is due to the photochemical cleavage of the spiro C—O
bond upon UV light irradiation，which leads to the extension of π-conjugation in the colored
photomerocyanine (PMC) and thus shifts the absorption to the visible region [11-12]. The colored PMC
can revert to the colorless SO form by a thermally induced ring-closure reaction when the UV light
irradiation ceases.
<Scheme 1>
For commercial application of multifunctional optoelectronic materials, it is essential to maintain
photochromic molecules with fast photoresponse, large steady-state optical density and high
fatigue-resistance [13]. In the present investigation, we report the synthesis, crystal structure and
photochromism of a new SO derivative 1．The synthetic route and the structure of compound 1 in this
work were shown in Scheme 2. Interestingly, to the best of our knowledge, such a SO derivative has not
been reported so far. A remarkable characteristic of compound 1 is that its indoline and naphthoxazine
moieties are linked by a bridged chain. X-ray diffraction indicates that compound 1 belongs to
orthorhombic system. The dihedral angles between benzene (atoms C1-C6) and naphthalene rings
2

(atoms C14–C23) are 89.56 Å. There are four molecules in one unit cell, and the structure consists of the
packing molecules with normal van der Waals. Especially, in solvents, the title compound 1 displayed
excellent photochromism, acidichromism and strong fluorescence properties, indicative of an extensive
application in future development of high-performance photochromic materials.
<Scheme 2>
2. Experimental
2.1. General remarks
All chemicals were purchased from commercial sources, and solvents used were dried and purified by
distillation before use. Melting points were determined with an X4 Micro-melting point apparatus
1
13
uncorrected. H NMR and C NMR spectra were recorded using a Bruker 400 MHz spectrometer with
TMS as internal standard. IR spectra were recorded on a TENSOR 37 spectrophotometer using KBr
disks and wavenumbers were given in cm-1. Mass spectra were measured on a 7070E-HE spectrometer.
Fluorescence spectra were measured on a F-2500 FL Spectrophotometer. X-ray Crystal Diffraction were
measured on a Rigaku 007 Saturn 70 diffractometer.
2.2. Synthesis of 5-methoxy-2,3,3-trimethyl-3H-indole
A synthetic procedure was based on the literature method [14] with slight modifications.
4-methoxy-phenylhydrazine hydrochloride (0.223 g, 1.62 mmol) and isopropyl methyl ketone (0.139 g,
1.62 mmol) were added to glacial acetic acid (10 ml). The mixture was refluxed for 10 h with stirring.
Then the mixture was cooled and neutralized with 1 M Na2CO3 then diluted with water (100 mL) and
3

extracted with CHCl3 (3 × 100 mL). Following the drying of the organic layer over MgSO4, the solvent
was removed by means of evaporation. A red, viscous oil of 5-methoxy-2,3,3-trimethyl-3H-indole was
obtained in high yield (95%).
2.3. Synthesis of 1-(2-Hydroxyethyl)-5-methoxy-2,3,3-trimethyl-3H-indolium Bromide
A synthetic procedure was based on the literature method [15] with some modifications. A solution of
5-methoxy-2,3,3-trimethyl-3H-indole (0.502 g, 1.60 mmol) and 2-bromoethanol (0.198 g, 2.00 mmol) in
MeCN (20 mL) was maintained under N2 and heated under reflux for 1 day. After the mixture was
cooled to ambient temperature, the solvent was distilled off under reduced pressure. The resulting solid
was recrystallized from CHCl3 (35 mL), then filtered and dried, to afford the targeted compound in high
yield (68%).
2.4. Synthesis of 1-nitroso-2-naphthol copper salt
1.34 g (10.00 mmol) CuCl2 in 40 mL aqueous solution was added to the 80 mL mixed solution of
tetrahydrofuran and water (1:1 v/v) containing 3.98 g (24.00 mmol) 1-nitroso-2-naphthol while stirring.
The reaction was completed after 20 min at room temperature, the raw product of 1-nitroso-2-naphthol
copper salt was filtered, then washed with water, and dried under an infrared heat lamp. Yield: 96%.
2.5. Synthesis of 12-methoxy-14,14-dimethyl-17-(piperidin-1-yl)-7,8,14,15a-tetrahydro-4bH-naphtho
[1'',2'':5',6'][1,4]oxazino[3',2':2,3][1,4]oxazino[4,3-a]indole (1)
1-Nitroso-2-naphthol copper salt (0.408 g, 1.0 mmol) and piperidine (0.425 g, 5.0 mmol) were added to 20
mL ethanol. The resulting mixture was stirred for
4
h
at reflux. The mixture of
1-(2-Hydroxyethyl)-5-methoxy-2,3,3-trimethyl-3H-indolium Bromide (0.367 g, 1.8 mmol) and
4

triethylamine (1 mL) in 20 mL ethanol after stirred for 30 min at room temperature was added to the
solution, and stirred for 8 h at reflux. After removal of the solvent, the residue was purified by column
chromatography on silica gel with petroleum ether/ethyl acetate (5:1v/v) as the eluent to give light yellow
solid 1 in 24% yield.
1
m.p. 202-204℃. H NMR (CDCl3, 400 MHz) δ: 8.40 (d, J=10.8 Hz, 1H, Ar-H), 8.09-8.11 (m, 1H,
Ar-H), 7.39-7.50 (m, 2H, Ar-H), 6.56-6.76 (m, 4H, Ar-H), 4.35-4.39 (m, 2H, O-CH2)，3.66-3.96 (m, 5H,
N-CH2, OCH3), 3.02-3.03 (m, 4H, N(CH2)2), 1.83-1.84 (m, 4H, CH2(CH2)2),1.58-1.66 (m, 2H,
CH2(CH2)2) 1.31 (s, 3H, C-CH3), 1.28 (3H, s, C-CH3) 13C NMR (CDCl3, 100 MHz) δ: 155.5, 152.2,
142.6, 139.9, 138.7, 130.6, 126.6, 125.3, 125.2, 123.8, 123.7, 122.5, 113.3, 111.6, 109.0, 105.9, 99.9,
67.0, 55.8, 54.8, 52.3, 44.8, 27.8, 26.7, 26.4, 24.4. IR (KBr); ν: 2935，1635，1587，1498，1458，1280，
1257，1236，1217，1155，1128，1051，1033，825，771 cm-1; HRMS calcd for C29H31O3N3 [M+H]+
470.2444, Found [M+H]+ 470.2435.
2.6. X-ray crystallography
By recrystallization from the mixture solvents (ethanol and trichloromethane) at room temperature,
colorless single crystals were obtained for X-ray diffraction analysis．The diffraction measurements were
made on a Rigaku Saturn 724 CCD diffractometer MoKα radiation (λ =0.71073 Å). The data were
collected at 113(2) K. Linear absorption coefficient 0.086 mm-1. In the range of 1.99 < <27.91°. 30258
integrated reflections were collected, reducing to a data set of 3191 unique with Rint = 0.0494, and
completeness of data (to theta = 27.91°) of 99.6%. Data were collected and processed using Crystal
Clear (Rigaku). An empirical absorption correction was applied using Crystal Clear (Rigaku). The
structure was solved by direct methods with SHELXS-97 program [16]. Refinements were done by the
5

full-matrix least-squares on F2 with SHELXL-97 program [17]. The crystal structure and packing
diagram were depicted using MERCURY [18]. All of the non-H atoms were refined anisotropically by
2
2
full-matrix least-squares to give the final R = 0.0387, wR = 0.0898, (w =1/[σ (Fo ) + (0.0589P)2 +
0.0159P], where P = (Fo2 +2Fc2)/3) with (Δ/σ)max = 0.002 and S = 1.074 by using the SHELXL program.
All of the hydrogen atoms were placed by calculation geometry and took part in refinement. The
corrections for absorption were multi-scan, Tmin = 0.9831 and Tmax = 0.9898. Selective crystal data for the
title compound 1 are shown in Table 1.
<Table 1>
2.7. Spectral measurements
The solutions of compound 1 in trichloromethane, carbontetrachloride and cyclohexane with the
concentration of 1×10-4 mol L-1 were prepared. The UV–vis absorption spectra were measured at room
temperature using a Shimadzu UV-2101PC spectrophotometer. The samples were irradiated with a 12 W
ultraviolet lamp at 365 nm. The fatigue resistance was examined after 10-cycle irradiation of UV and
visible lights.
3. Results and discussion
3.1. Structure analysis
The title compound 1 was synthesized in four steps. The method is simple, starting from commercially
13
available compound 4-methoxy-phenylhydrazine hydrochloride. The 1H NMR， C NMR, IR and HRMS
are in good agreement with the title compound 1. Piperidine group as electron-donating group was
6

appended on the SO skeleton in order to increase the electronic density of the molecular system.
Different from conventional SO derivatives, 1 and 2' position of the title compound 1 are linked to form
three ring system by a donor –O–alkyl chain. Owing to a special design of molecular structure, the
unusual 'oxazino bridged' compound 1 showed an obvious change in photochromic properties compared
with the relative non 'oxazino bridged' compound 1a (Scheme 3) [19].
<Scheme 3>
3.2. Crystal structure description
The 1H NMR, 13C NMR, IR and HRMS were used to determine the structure of the title compound 1，
and single-crystal X-ray diffraction study was involved to confirm its configuration (Fig. 1). As
illustrated in Table 2, the torsion angles of C(16)–C(17)–C(22)–C(23) and C(21)–C(22)–C(17)–C(18)
are respectively -0.6(2)° and -1.4(2)°, indicating that the naphthalene ring is similarly planar. The six
membered heterocycle containing spiro Csp3–O is nonplanar. The dihedral angles between benzene
(atoms C1-C6 ) and naphthalene rings (atoms C14–C23 ) is 89.56°, suggesting that benzene and
naphthalene rings are almost orthogonal to each other, and thus, there is no conjugation between the two
moieties. Atoms N1, N2, N3 and O2 are approximately coplanar with the naphthalene ring plane, with
deviations of 0.102, 0.096, 0.107 and 0.076 Å, respectively. The five-membered rings
(C1/N1/C6/C10/C11) adopt envelope conformations, with the flaps at C10. The piperidine ring at the
6'-C site is in a chair conformation. The oxazine rings (the key zone of the photochromism) suggest bond
delocalization involving the C, N and O atoms, including the adjacent aromatic ring. This is also
confirmed by the bond lengths involving the C, N and O atoms. For instance, the C6—N1 bond lengths
7

are 1.424(2) Å, which is between the value of 1.48 Å for a C—N single bond and 1.28 Å for a C—N
double bond, showing partial delocalization of the π-electron density over the indole ring. Similarly, the
C14—O2 bond lengths are 1.374(2) Å, which is between the value of 1.39 Å for a C—O single bond
and 1.23 Å for a C—O double bond [20]. The C23—N2 bond lengths are 1.408(2) Å, indicating that
atoms O2 and N2 in the oxazine ring are conjugated with the π-electron system of the naphthalene ring.
All of these delocalizations are favorable for the stabilization of the open PMC structure of the title
compound 1.
The Cspiro—N and Cspiro—O bond lengths are two key points in the structure of spirooxazine. The former
exerts an important influence on the stability of the open PMC form, and the latter cleaves upon UV
light irradiation to give open PMC form of the spirooxazine.
3.2.1. Cspiro–N1 bond length
In molecule 1, Cspiro—N bond lengths are shortened to 1.446(2) Å for C10—N1, which is consistent
with that observed for photochromic spirooxazines [21]. A short Cspiro–N1 bond is an indication of
donation of lone pair electrons from N1 to Cspiro, which would stabilize the cation that develops on Cspiro
of the open PMC form.
It was found that the crystallographic bond angles around the spiro carbon atom of molecule 1 are
between 106.15° and 114.01°. Both this distortion from the tetrahedral angle and the short Cspiro–N1
bond length indicate that the spiro carbon possesses a degree of sp2 -character. The sum of the bond
angles at N1 was found to be 339.64°, which lies between the sum for sp3 hybridized bond angles (327°)
and the sum for sp2 hybridized bond angles (360°). The sum of the bond angles, as well as the shorter
Cspiro–N distance described above, indicates that N1 has some sp2 character to stabilize a developing
8

positive charge on Cspiro
.
3.2.2. Cspiro–O2 bond length
The Cspiro—O bond lengths are elongated to 1.451(2) Å for C10—O2. A longer Cspiro–O bond facilitates
efficient Cspiro–O bond cleavage and is associated with photochromism in spirooxazines [21,22]. The
bond length shows that there is no significant differences compared with other photochromic
spirooxazines [23].
<Fig. 1>
<Table 2>
3.3. Crystallography and intermolecular contacts
Four molecules in one unit cell and the structure consists of the packing molecules with normal van der
Waals (Fig. 2). Compound 1 crystallized in the P212121 space group as colorless crystals. One interesting
feature of the structure is the presence of several short van der Waals intermolecular distances (Table 3).
For example, edge to face interactions are detected between aromatic systems, such as the intermolecular
short contact observed between H5 and C21, displaced from the centroid (H5-centroid distance is 3.383
Å). In addition, there is a strong C–H-π interaction between H27B and C4, H7B and C17, respectively
(H27B-centroid distance is 2.804 Å; H7B-centroid distance is 2.747 Å). The crystal lattice is further
stabilized by the presence of short intermolecular contacts between carbon atoms. For instance, the
H7A–C27 distance is 2.860 Å and the C29–N1 distance is 3.128 Å.
<Fig. 2>
9

<Table 3>
3.4. Photochromic properties
Photochromic properties of the title compound 1 were studied in different solvents, it was found that
compound 1 in various solutions could undergo photochemical reaction within 5 s upon UV light
irradiation. As illustrated in Fig. 3, Ultraviolet λ
365 nm irradiation of compound 1 in
max
trichloromethane and carbontetrachloride solution led to increase in absorption intensity in the visible
region of the band, accompanied by the coloration variations of trichloromethane and
carbontetrachloride solution (Fig. 4). The new band can be attributed to the absorption of the colored
PMC structure. The λ
values of the longest wavelength absorption bands is at 674 and 521 nm in
max
trichloromethane and carbontetrachloride solution, respectively, indicating that the polar solvents can
impart bathochromic shifts for the λmax of the PMC form of compound 1. Because of the steric hindrance
effect caused by the substituent in the 2'-position of the oxazine moiety and the methyl groups in
3-position of the indoline moiety, the thermal decoloration rate of compound 1 in solvents became slow,
and a complete fading was achieved within 20 s. Obviously, the open PMC form of compound 1
possesses long lifetime, which in principle is useful for technological applications of SO derivatives,
such as data storage.
Fatigue resistance is an important factor to consider for applicable photochromic material. To further
investigate the photochromic properties of compound 1, fatigue resistance in different solvents was
investigated by turning UV light of 365 nm on and off. As presented in Fig. 5, after 10-cycle irradiation
of UV and visible lights, even in the presence of molecular oxygen, the absorbance was kept in 87.4%
and 85.4% in trichloromethane and carbontetrachloride, respectively (Fig. 5). It showed that the new title
10

compound 1 exhibited high fatigue resistance in trichloromethane and carbontetrachloride solution.
<Fig. 3>
<Fig. 4>
<Fig. 5>
3.5. Acidichromism properties
Halochromism, a term introduced by von Baeyer [24], mainly denotes the color change of a dye on
addition of acids or bases. We also investigated the acidichromic phenomenon of compound 1 (1.0 ×
10-4 mol L−1) in trichloromethane and cyclohexane solution (Fig. 6). When trifluoroacetic acid was
added to the solution of compound 1, it is found that colorless solution turned blue immediately, which
was due to the formation of a protonated photomerocyanine (PMCH). The colored PMCH species shows
thermal stability and photoinactivity. When triethylamine was added, the decoloration of the blue
solution could be performed completely, indicating that the ring-opening and ring-closing
interconversion of spirooxazine derivative can be performed by acid and base trigger via complexing
and decomplexing. The principle of SPO and PMCH form interconversion with acid and base trigger is
outlined in Scheme 4. Interestingly, the color switching could be cycled with acid (trifluoroacetic acid)
and base (triethylamine) trigger in different solvents (Fig. 7), this provides a promising way of
manipulating ring-opening and ring-closing interconversion for spirooxazine derivatives
<Scheme 4>
<Fig. 6>
11

<Fig. 7>
3.6. Fluorescence properties
Excitation of compound 1 in trichloromethane solution at λ of 310nm at room temperature produced
max
strong fluorescence, and fluorescence intensity was stronger upon UV light irradiation (Fig. 8) than that
before UV light irradiation, this may be explained by the fact that PMC form after UV irradiation
enhance the electron density of the conjugation bone, and increase the molecular rigidity. Compound 1
with strong fluorescence properties may have broad potential applications in designing high efficiency
fluorescent probes, high performance light-emitting materials, etc.
<Fig. 8>
4. Conclusion
A new spiro[indoline-naphthaline]oxazine derivative 1 has been successfully synthesized and
characterized, and its crystal structure has been obtained by recrystallization from the mixture solvents at
room temperature. The crystal structure indicated that benzene and naphthalene rings in molecule 1 are
similarly perpendicular, and atoms N1, N2, N3 and O2 are approximately coplanar with the naphthalene
ring plane. Short intermolecular distances in the packing diagram were also investigated. In solvents, the
title compound 1 exhibited excellent photochromic properties. The new photochromic compound 1 with
high fatigue resistence may be successfully used as sunglasses, optical switching, optical data storage,
etc.
Acknowledgement
12

We are grateful to the National Natural Science Foundation of China for financial supports (Nos.
20971071 and 20602020), and we thank the Natural Science Foundation of Tianjin for financial supports
(14JCZDJC38000).
References
[1]
B.L. Feringa, Molecular Switches. Wiley-VCH: Weinheim. (2001).
M. Irie, Chem. Rev. 100 (2000) 1685-1716.
[2]
[3]
N. Xie, Y. Chen, J. Mater. Chem. 16 (2006) 982-985.
[4]
K. Guo, Y. Chen, J. Mater. Chem. 19 (2009) 5790-5793.
[5]
H. Liu, H.Y. Chen, Dyes and Pigments. 89 (2011) 212-216.
[6]
C.C. Ko, V.W.W. Yam, Supramolecular Chemistry: From Molecules to Nanomaterials. (2012).
L. Liu, D.Z. Jia, Y.L. Ji, K.B. Yu, Journal of Molecular Structure. 655(2003) 221-227.
R.M. Christie, K.M. Morgan, A. Rasheed, M. Aldib, G. Rosair, Dyes Pigment 98 (2013) 263-72.
Q. Zou, X. Li, J. Zhou, K. Bai, H. Ågren. Dyes and Pigments, 107 (2014) 174-181.
S.V. Paramonov, V. Lokshin, O.A. Fedorova, J. Photochem. Photobiol. C. 12 (2011) 209-36.
D.L. Watkins, T. Fujiwara, J. Photochem. Photobiol. A. 228 (2012) 51-9.
X.L. Li, Y.M. Wang, T. Matsuura, J.B. Meng, J. Photochem. Photobiol. A. 161 (2004) 201–213.
L.W. Song, Y.H. Yang, Q. Zhang, H. Tian, W.H. Zhu, J. Phys. Chem. B. 115 (2011) 14648-58.
S. Sami, V. Hooshang, M.L. Abdolhossien, Omid. Part I. Molecules. 15 (2010) 2491-2498.
M.R. Francüisco, G. Silvia, J. Org. Chem. 68 (2003) 4158-4169.
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
G.M. Sheldrick, Acta. Cryst. 46 (1990) 467-473.
G.M. Sheldrick, University of Gottingen, Germany. (1997).
13

[18]
C.F. Macrae, I.J. Bruno, J.A. Chisholm, P.R. Edgington, P. McCabe, L. EPidcock. Rodriguez-Mong
e, R. Taylor, J. van de Streek, P.A. Wood, J. Appl. Crystallogr. 4 (2008) 466–470.
M.L. Pang, H.J. Zhang, P.P. Liu, Z.H. Zou, J. Han, J.B. Meng, SYNTHESIS 20 (2010) 3418–3422.
F.H. Allen, O. Kennard, D.G. L. Brammer, A.G. Orpen, R. Taylor, J. Chem. Soc. Perkin Trans. 2
(1987) S1–19.
[19]
[20]
[21]
[22]
[23]
[24]
K. Satish, V. Kriya, M. Alison, Journal of Molecular Structure. 968 (2010) 13–18.
S.M. Aldoshin, V.M. Anisimov, J. Mol. Struct. 419 (1997) 77.
H. Guo, Y.B. Gao, Y.X. Li, J. Han, J.B. Meng, Acta. Cryst. 61 (2005) 988–989.
A. Baeyer, V. Villiger. Ber. Dtsch. Chem. Ges. 35 (1902) 1189-1201.
14

Scheme 1 The structural interchange between the SO and PMC isomers
15

Scheme 2 The synthetic route and selective atom numbering of SO derivative 1
16

Scheme 3 Structure and atom numbering of compound 1 and non-bridged compound 1a.
17

Scheme 4 The principle of ring-opening and ring-closing interconversion of compound 1
with acid and base trigger
18

Figure and Table Captions
Table 1. Selected crystallographic data for the title compound 1
Table 2. Selected Bond Lengths (Å), Bond Angles (°) and Torsion Angles (°) for the title compound 1
Table 3. Short van der Waals intermolecular distances in crystal packing diagram of compound 1
Fig. 1. A view of the molecule of the title compound 1 with atomic numbering scheme
Fig. 2. Crystal packing diagram of compound 1 showing short intermolecular contacts view along b
axis
Fig. 3. UV-vis spectra (1.0×10-4 mol L-1) in trichloromethane (a) and in carbontetrachloride (b): a
before irradiation of UV light; b after irradiation of UV light
Fig. 4. Photographs of photochromic processes of compound 1 in trichloromethane (a) and in
carbontetrachloride (b)
Fig. 5.
Photoinduced absorption changes of compound 1 in trichloromethane (a) and in
carbontetrachloride (b); photoirradiation started at each point of top for visible light and then finished at
the point of bottom for UV light
Fig. 6. UV-vis spectra of compound 1 (1.0×10-4 mol L-1) before addition of CF3COOH (black), after
addition of CF3COOH (green) and after addition of triethylamine (magenta) in trichloromethane (a) and
in cyclohexane (b)
Fig. 7. Cycle number of coloration and decoloration with CF3COOH and triethylamine trigger in
trichloromethane (a) and in cyclohexane (b)
Fig. 8. Fluorescence spectra of compound 1 (1.0×10−4 mol L-1) at excitation wavelength at 310 nm
before UV irradiation (black) and after UV irradiation (red) in trichloromethane at room temperature
19

Table 1
Empirical formula
Formula weight
Temperature/K
Wavelength/Å
Crystal system
space group
a/Å
C29 H31 N3 O3
469.57
113(2)
0.71073
Orthorhombic
P212121
11.335(2)
14.198(3)
14.777(3)
b/Å
c/Å
α/(°)
90
90
90
β/(°)
γ/(°)
Volume/ Å3
2378.2(8)
4
Z
Calculated density/(g•cm－3
)
1.311
F(000)
1000
Crystal size (mm)
Reflections collected
Reflections unique
Rint
0.20 x 0.18 x 0.12
30258
3191
0.0494
Goodness-of-fit on F2
1.074
Final R indices [I>2σ (I)]
R＝0.0387, wR＝0.0898
Largest diff. peak and hole / e.Å-3
0.260 and -0.203
20

Table 2
Bond
Dist
Bond
Dist
Bond
Dist
O(1)-C(3)
O(1)-C(29)
O(2)-C(14)
O(2)-C(10)
O(3)-C(8)
N(1)-C(6)
C(4)-H(4)
Bond
1.375(2)
1.424(2)
1.374(2)
1.451(2)
1.460(2)
1.424(2)
0.9500
C(1)-C(6)
C(1)-C(2)
C(1)-C(11)
C(2)-C(3)
C(2)-H(2)
C(3)-C(4)
C(4)-C(5)
1.385(2)
1.397(3)
1.513(2)
1.396(3)
0.9500
N(1)-C(10)
N(1)-C(7)
N(2)-C(9)
N(2)-C(23)
N(3)-C(16)
N(3)-C(24)
N(3)-C(28)
Bond
1.446(2)
1.466(2)
1.272(2)
1.408(2)
1.432(2)
1.471(2)
1.482(2)
angle (°)
1.395(3)
1.387(3)
angle (°)
Bond
angle (°)
105.58(13)
112.25(14)
106.52(14)
111.25(15)
127.67(16)
109.98(14)
109.7
C(6)-N(1)-C(10)
C(6)-N(1)-C(7)
C(10)-N(1)-C(7)
C(9)-N(2)-C(23)
C(24)-N(3)-C(28)
C(6)-C(1)-C(2)
C(6)-C(1)-C(11)
Torsion angle
108.81(14)
117.70(14)
113.13(14)
115.50(15)
110.08(14)
120.57(17)
110.85(15)
(°)
N(1)-C(10)-O(2)
N(1)-C(10)-C(9)
O(2)-C(10)-C(9)
C(1)-C(6)-N(1)
C(5)-C(6)-N(1)
N(1)-C(7)-C(8)
N(1)-C(7)-H(7A)
Torsion angle
O(3)-C(9)-C(10)
O(3)-C(8)-C(7)
117.94(14)
110.93(14)
124.60(16)
117.36(16)
109.7
N(2)-C(9)-C(10)
N(2)-C(9)-O(3)
N(1)-C(7)-H(7B)
C(8)-C(7)-H(7B)
H(7A)-C(7)-H(7B)
Torsion angle
109.7
108.2
(°)
(°)
C(26)-C(27)-C(28)-N(3) 55.6(2)
C(6)-C(1)-C(2)-C(3)
1.4(3)
C(6)-N(1)-C(10)-C(11)
C(7)-N(1)-C(10)-C(11)
-12.12(18)
-144.93(14)
C(25)-C(26)-C(27)-C(28) -53.0(2) C(11)-C(1)-C(2)-C(3)
177.43(17)
-177.52(15)
3.8(3)
C(29)-O(1)-C(3)-C(4)
C(16)-C(17)-C(22)-C(23) -0.6(2）
C(29)-O(1)-C(3)-C(2)
C(14)-O(2)-C(10)-N(1) -165.20(13)
C(14)-O(2)-C(10)-C(9)
C(14)-O(2)-C(10)-C(11)
N(2)-C(9)-C(10)-N(1)
O(3)-C(9)-C(10)-N(1)
-45.68(18)
79.28(17)
152.56(16)
-31.1 (2)
C(18)-C(17)-C(22)-C(21) -1.4 (2)
C(1)-C(2)-C(3)-O(1)
C(1)-C(2)-C(3)-C(4)
O(1)-C(3)-C(4)-C(5)
177.27(18)
-1.3(3)
N(1)-C(7)-C(8)-O(3)
C(9)-O(3)-C(8)-C(7)
-51.6(2)
2.2(2)
-178.01(17)
C(23)-N(2)-C(9)-C(10) -6.4(2)
21

Table 3
Atom 1
Atom 2
Length
length-vdw
H27B
C28
C4
H8A
N1
2.852
2.859
3.128
2.860
2.209
2.871
2.745
2.837
2.750
2.838
-0.048
-0.041
-0.122
-0.040
-0.191
-0.029
-0.005
-0.063
-0.150
-0.062
C29
H7A
H7A
H24A
N2
C27
H27A
C20
H4
C17
H7B
H5
C21
C22
H5
22

Fig. 1
23

Fig. 2
24

Fig. 3
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
2.0
1.5
1.0
0.5
0.0
b
b
a
a
300
400
500
600
700
800
300
400
500
600
700
800
wavelength (nm)
wavelength (nm)
a
b
25

Fig. 4
a
b
26

Fig. 5
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
0
2
4
6
8
10
0
2
4
6
8
10
time of cycle
time of cycle
a
b
27

Fig. 6
3.0
2.5
2.0
1.5
1.0
0.5
0.0
3.0
2.5
2.0
1.5
1.0
0.5
0.0
300
400
500
600
700
800
900
300
400
500
600
700
800
900
wavelength (nm)
wavelength (nm)
a
b
28

Fig. 7
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
0
1
2
3
4
5
0
1
2
3
4
5
cycle number
cycle number
a
b
29