Novel photochromic spiroheterocyclic molecules via oxidation of 1,8-diaminonaphthalene

Article abstract of DOI:10.1021/ol050138s

(Chemical Equation Presented) Novel spiroheterocyclic molecules, namely, 2,3-dihydro-2-spiro-7′-[8′-imino-7′,8′- dihydronaphthalen-1′-amine]perimidine, PNI, and 2,3-dihydro-2-spiro- 4′-[8′-aminonaphthalen-1′(4H)-one]perimidine, PNO-p, were obtained by oxi

Full text of DOI:10.1021/ol050138s

ORGANIC
LETTERS
2
005
Vol. 7, No. 8
461-1464
Novel Photochromic Spiroheterocyclic
Molecules via Oxidation of
1
1,8-Diaminonaphthalene
Riju Davis and Nobuyuki Tamaoki*
Molecular Smart System Group, Nanotechnology Research Institute, National Institute
of AdVanced Industrial Science and Technology, Central 5, 1-1-1 Higashi, Tsukuba,
Ibaraki 305-8565, Japan
n.tamaoki@aist.go.jp
Received January 21, 2005
ABSTRACT
Novel spiroheterocyclic molecules, namely, 2,3-dihydro-2-spiro-7′-[8′-imino-7′,8′-dihydronaphthalen-1′-amine]perimidine, PNI, and 2,3-dihydro-
2
-spiro-4 -[8 -aminonaphthalen-1 (4H)-one]perimidine, PNO-p, were obtained by oxidation of 1,8-diaminonaphthalene using manganese dioxide.
′
′
′
These molecules exhibit thermally reversible photochromism with good photofatigue resistance, and their photogenerated forms possess
broad absorption in the visible region.
Photomodulation of the chemical structure of organic
molecules forms the basis of a host of light-driven molecular
devices and switches wherein photochromic materials form
a vital entity. The superior photochromic properties of
spiroheterocyclic molecules such as spiropyrans, spirooxa-
zines, and chromenes have attracted intense research that
has identified their wide application prospects in the area of
photonic materials.
1
a,b,f,2
Photochromism in these systems involves a photoinduced
C-X (X ) O, N,or S) bond cleavage at the spiro junction
that leads to an extended π-conjugation between two
aromatic units that are orthogonally oriented in the initial
spiro form. During the course of our studies, we observed
that oxidation of 1,8-diaminonaphthalene using manganese
dioxide yields novel spiroheterocyclic photochromic mol-
ecules. These molecules exhibit thermally and photochemi-
cally reversible photochromism and possess good photofa-
tigue resistance. The photogenerated forms of these molecules
exhibit broad absorption in the visible spectrum which is a
1
(1) (a) Photochromism-Molecules and Systems; D u¨ rr, H., Bouas-Laurent,
H., Eds.; Elsevier: Amsterdam, 1990. (b) Organic Photochromic and
Thermochromic Compounds; Crano, J. C., Guglielmetti, R. J., Eds.; Plenum
Press: New York, 1999; Vols.1 and 2. (c) Molecular Switches; Ferringa,
B. L., Ed.; Wiley-VCH: Weinheim, 2001. (d) Photochromism: Memories
and Switches, Special issue, Chem. ReV. 2000, 100, 1683-1890. (e)
Molecular Machines, Special issue, Acc. Chem. Res. 2001, 34, 409-522.
(
f) Bousas-Laurent, H.; D u¨ rr, H. Pure Appl. Chem. 2001, 73, 639. (g)
PhotoreactiVe Materials for Ultrahigh-Density Optical Memory; Irie, M.,
Ed.; Elsevier: Amsterdam, 1994. (h) Myles, A. J.; Branda, N. R. AdV. Funct.
Mater. 2002, 12, 167.
(2) Minkin, V. I. Chem. ReV. 2004, 104, 2751.
1
0.1021/ol050138s CCC: $30.25
© 2005 American Chemical Society
Published on Web 03/22/2005

Figure 1. ORTEP diagrams of the oxidation products of 1,8-diaminonaphthalene.
prerequisite of materials used in photochromic opthalmic
lenses. In most cases, neutrality of the activated color,
characterized by the broadness of the visible light absorption,
has been accomplished by mixing several photochromic
molecules possessing absorption over different parts of the
visible region.1b,3,4 In this paper we describe the preparation
and photochromic properties of the newly obtained spiro-
heterocyclic molecules that are expected to form potential
candidates in generating photochromic materials.
The structures of these products were unequivocally eluci-
dated using H NMR, single-crystal X-ray diffraction, and
1
elemental analyses. Figure 1 shows the ORTEP diagram of
the products obtained. Using a high dilution (×25 times)
reaction condition, in which a benzene solution of DAN was
slowly added (over 50 h) to a suspension of manganese
dioxide in benzene, we observed the formation of an inter-
mediate product, 8-amino-1-iminonaphthalen-2(1H)-one.5
The formation of the spiroheterocyclic product, PNI, hence
became conceivable to result from the condensation of DAN
with this intermediate.
1,8-Diaminonaphthalene, DAN, was oxidized in the pres-
ence of manganese dioxide as shown in Scheme 1. The
PNI undergoes a complete transformation into two mol-
ecules, 2,3-dihydro-2-spiro-2′-[8′-aminonaphthalen-1′(2H)-
one]perimidine, PNO, and a diiminoaminonaphthalene het-
Scheme 1
Scheme 2
erocycle, DIAN (Scheme 2 and Figure 2), in the presence
5
of silica gel used for column chromatography.
reaction yielded two spiroheterocyclic products, 2,3-dihydro-
2
-spiro-7′-[8′-imino-7′,8′-dihydronaphthalen-1′- amine]peri-
midine, PNI, and 2,3-dihydro-2-spiro-4′- [8′- aminonaphthalen-
′(4H)-one] perimidine, PNO-p, along with (E)-8-((8′-
aminonaphthalen-1-yl)diazenyl)naphthalen-1-amine, ANAzo.
1
(
3) Crano, J. C.; Flood, T.; Knowles, D.; Kumar, A.; Gemert, B. V. Pure
Appl. Chem. 1996, 7, 1395.
4) Salemi-Delvaux, C.; Pottier, E.; Guglielmetti, R. J.; Dubest, R.;
Aubard, J. Dyes Pigm. 1999, 40, 157.
(
Figure 2. ORTEP diagrams of PNO and DIAN.
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Org. Lett., Vol. 7, No. 8, 2005

-
5
Figure 3. Absorption spectral changes upon photolysis of a toluene solution using 405 nm light at 25 °C: (A) PNI (c ) 2.8 × 10 M),
-
5
(
(
a) 0 s, (b) 10 s, (c) 20 s, (d) 30 s, (e) 40 s, (f) 50 s, (g) 60 s, (h) 90 s, (i) 180s (PSS); (B) PNO-p (c ) 1.7 × 10 M), (a) 0 s, (b) 10 s,
c) 30 s, (d) 1 min, (e) 2 min, (f) 3 min, (g) 4 min (PSS). Repeated ring close-open-close cycles of the photochromic molecules using 405
nm (blue line) and 532 nm lasers (green line) have also been shown.
The transformation of PNI to PNO involves the hydrolysis
of the imino group to a ketone moiety. This solvent-
Minkin et al. have studied various related spiroheterocyclic
systems whose photochromic reactions have been established
to involve an initial photoinduced C-N bond cleavage at
the spiro junction to form a zwitter ionic state following
which a proton transfer occurs to form a molecule having
extended conjugation and hence deep coloration.2
6
independent transformation of PNI persisted even on de-
gassing a dehydrated solution of PNI by bubbling Ar gas
for at least 30 min to remove any dissolved gases, prior to
the addition of silica gel. However, PNI is highly stable in
solution, the solid state, and over surface-modified silica used
in HPLC normal-phase columns.
,7
The photochromic reaction in the present molecules may
be described as shown in Scheme 3, where upon photolysis,
PNI and PNO-p exhibit efficient photochromic reactions.
Upon photolysis of a toluene solution of PNI, using 405 nm
light, its absorption band centered at 410 nm decreases in
intensity with a concomitant increase in that of a new band
centered at 490 nm (sh 600 nm) as depicted in Figure 3A.
During this change, the initial yellow solution of PNI turns
deep brown. Similarly, photolysis of a toluene solution of
PNO-p brought about a decrease in the absorbance of the
band centered at 398 nm with an associated increase in that
of a broad band centered at 560 nm (Figure 3B). In the case
of PNO-p, upon photolysis the initial yellow solution turns
deep blue. It is interesting to note that the absorption bands
of the activated forms of these spiroheterocycles are fairly
broad covering a major portion of the visible spectra. In each
case, the photogenerated species fully reverts to the initial
form both thermally and photochemically using visible light.
The photochromic reactions of both PNI and PNO-p proceed
through an isosbestic point at 443 nm, which indicate a clear
interconversion between two states. In toluene, at 30 °C, the
lifetimes of the photoactivated colored forms of PNI and
PNO-p were estimated to be 4.4 and 1.7 h, respectively.
Scheme 3
the intial ring-closed spiro form transforms to a ring-opened
species having an extended conjugation that results in the
formation of a deep coloration. PNI and PNO-p undergo
ring-opening reaction only in the presence of light. In the
(
7) (a) Minkin, V. I.; Komissarov, V. N.; Kharlanov, V. A. Perim-
idinespirocyclohexadienones. In Organic Photochromic and Thermochromic
Compounds; Crano, J. C., Guglielmetti, R. J., Eds.; Plenum Press: New
York, 1999; Vol. 1, pp 315-340. (b) Komissarov, V. N.; Gruzdeva, E. N.;
Kharlanov, V. A.; Olekhnovich, L. P.; Borodkin, G. S.; Khrustalev, V. N.;
Lindeman, S. V.; Struchkov, Y. T.; Kogan, V. A.; Minkin, V. I. IzV. Akad.
Nauk. SSSR 1997, 46, 2028. (c) Komissarov, V. N.; Kharlanov, V. A.;
Ukhin, L. Y.; Morkovnik, Z. S.; Minkin, V. I. Zh. Org. Khim. 1990, 26,
1
106. (d) Minkin, V. I.; Komissarov, V. N. Mol. Cryst. Liq. Cryst. 1997,
(
5) See the Supporting Information.
297, 205. (e) Komissarov, V. N.; Kharlanov, V. A.; Ukhin, L. Y.; Minkin,
V. I. Dokl. Phys. Chem. 1988, 301, 692. (f) Komissarov, V. N.; Kharlanov,
V. A.; Ukhin, L. Y.; Minkin, V. I. Dokl. Akad. Nauk. SSSR 1988, 301,
902.
(6) (a) Cordes, E. H.; Jencks, W. P. J. Am. Chem. Soc. 1963, 85, 2843.
(
b) Hine, J.; Craig, Jr., J. C.; Underwood, J. G., II; Via, F. A. J. Am. Chem.
Soc. 1970, 92, 5194.
Org. Lett., Vol. 7, No. 8, 2005
1463

dark, even at elevated temperatures, their initial spiro forms
remain unchanged. This property of the newly obtained pho-
tochromic molecules distinguishes them from related peri-
midine based spiroheterocyclic derivatives that undergo spon-
taneous formation of an equilibrium between ring-closed and
similar to that of PNI, indicating the formation of its ring-
opened form. Thermal and photochemical reversal of the
5
ring-opened form also resulted in the formation of an
irreversible product that was isolated and characterized to
5
be PNO-P1 (Scheme 4). PNO-P1 transformed thermally
2,7a,b
ring-opened states upon dissolution in nonpolar solvents.
The composition of the closed and opened forms of these
photochromic molecules in the ring-opening reaction (using
Scheme 4
1
4
05 nm light) was estimated using H NMR analysis. In
benzene, at the photostationary state, PNI and PNO-p exist
predominantly in the ring-opened forms with their percent-
5
ages being 65 and 82%, respectively. Table 1 summarizes
Table 1. Spectroscopic Data of the Photochromic Molecules
and photochemically to another product whose structure has
yet to be characterized.
closed form
λmax, nm
open form
λmax, nm
(ꢀ, Μ-1 cm-1
In conclusion, we have described the photochromic
properties of two novel spiroheterocyclic molecules. The
efficient photochromism, good photofatigue resistance, and
broad activated absorption in the visible region of these
molecules are expected to make them useful in the field of
photochromic materials. By judicious structural modification
of these molecules their properties can be enhanced and
hence these also form useful models to obtain superior
photochromic materials.
solvent (ꢀ, Μ- cm-1
1
)
)
Φ(close-open)
entry
PNI
toluene
410 (18 700)
398 (9100)
490 (18 400)
520 (6500),
0.06
0.05
PNO-p toluene
595 (6200)
the spectroscopic data of the current photochromic com-
pounds. The photofatigue resistance of these derivatives was
examined by carrying out a series of ring close-open-close
cycles using 405 and 532 nm light (Figure 3). Even after
several successive cycles involving long hours of laser
irradiation (532 nm), achieving a recovery of >95% of the
spiro form in each cycle, the isosbestic point remained intact.
This indicates that no other photoreactions interfere with
these photochromic reactions. Although PNI and PNO were
structurally similar, the photoreactivity of PNO was varied.
Upon photolysis in toluene, the yellow solution of PNO
turned deeply colored with absorption spectral changes
Acknowledgment. We thank Ms. Midori Goto for X-ray
crystallographic analyses.
Supporting Information Available: Details of experi-
mental procedure, structure characterization, X-ray crystal
analyses data, and figures. This material is available free of
charge via the Internet at http://pubs.acs.org.
OL050138S
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Org. Lett., Vol. 7, No. 8, 2005