4-Styrylquinolines: Synthesis and study of [2 + 2]-photocycloaddition reactions in thin films and single crystals

Article abstract of DOI:10.1039/b615056j

Four new (E)-4-styrylquinoline compounds containing two methoxy substituents or an 18-crown-6-ether fragment were synthesized in order to investigate the [2 + 2]-photocycloaddition (PCA) reaction in the solid state. These compounds reveal different abilit

Full text of DOI:10.1039/b615056j

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PAPER
www.rsc.org/njc | New Journal of Chemistry
4-Styrylquinolines: synthesis and study of [2 + 2]-photocycloaddition
reactions in thin films and single crystalswz
Lyudmila G. Kuz’mina,*a Artem I. Vedernikov,b Natalia A. Lobova,b Andrei V. Churakov,a
Judith A. K. Howard,c Michael V. Alfimovb and Sergey P. Gromov*b
Received (in Montpellier, France) 16th October 2006, Accepted 11th January 2007
First published as an Advance Article on the web 17th April 2007
DOI: 10.1039/b615056j
Four new (E)-4-styrylquinoline compounds containing two methoxy substituents or an 18-crown-
6-ether fragment were synthesized in order to investigate the [2 + 2]-photocycloaddition (PCA)
reaction in the solid state. These compounds reveal different abilities to undergo the
photoreaction depending on the packing of the quinoline molecules in thin polycrystalline films
and single crystals. The only products from the irradiation of (E)-4-styrylquinolines were an rctt
isomer of 1,2,3,4-tetrasubstituted cyclobutane and, rarely, a Z isomer of the styrylquinoline. The
rctt cyclobutane derivative was formed as a result of the PCA of centrosymmetric syn-‘head-to-
tail’ dimeric pairs of the reactant species that are preorganized in such a way as to promote this
reaction. Peculiarities in the crystal packing motifs that are typical for single crystals of 4-
styrylquinoline compounds are discussed. The solvate molecules can affect significantly the
packing of styrylquinolines. Benzene solvate molecules create a soft, flexible, shell about the
dimeric pairs that facilitates the PCA in the single crystal without causing degradation of the
crystal. In crystal packing that contains CH2Cl2 and H2O solvate molecules, they are prone to
form complicated systems of hydrogen bonds with crown-ether oxygen atoms and each other.
This results in distorting the organic molecule geometry toward non-planarity and accomplishing
a new type of crystal packing uncommon for styrylheterocycles, in which the PCA is impossible.
The topochemical single-crystal-to-single-crystal PCA reaction was monitored for one of the
species. Two cyclobutane derivatives obtained in single crystals were subjected to recrystallization
from a solution. The new single crystals formed belong to different crystal systems, with different
unit cell parameters as compared with initial single crystals; significant differences in the geometry
of the cyclobutane molecules were also found. This implies that the cyclobutane derivatives
obtained in the solid phase have a molecular geometry that is somewhat stressed.
distance between these units, d1, should be equal to 3.6–4.2 A
Introduction
(Scheme 1). In the most cases these requirements are
Unsaturated compounds containing ethylene CQC bonds,
such as stilbenes, their aza analogues and vinylogues, are
realized although several exceptions to these requirements
are known and associated with more distant mutual arrange-
known to undergo [2 + 2]-photocycloaddition (PCA) in the
ment of the ethylene groups participating in the PCA or
solid state, or in concentrated solutions.1 It has been estab-
crossed arrangement of the ethylene groups in the parallel
planes.1n,o
lished that there are important specific geometric requirements
for the olefin dimer that is a precursor for this reaction. These
Previously, we have found that crown-ether stilbene-like
compounds participate in stereoselective PCA reactions.2,3
requirements are: (1) the two olefin units should be situated in
parallel planes one above the other and (2) the interplanar
For crown-ether styryl and butadienyl dyes bearing an N-
sulfonatoalkyl spacer, this reaction usually takes place in
a N. S. Kurnakov Institute of General and Inorganic Chemistry, the
Russian Academy of Sciences, Leninskiy prosp. 31, 119991 Moscow,
Russian Federation. E-mail: kuzmina@igic.ras.ru; Fax: +7 (495)
954 1279
solution in the presence of metal cations. Crown-ether styryl
dyes containing an ammonioalkyl group in their heterocyclic
moiety undergo efficient and stereospecific PCA both in solu-
tion and in the crystal state. We have established2 that the
presence of an additional functional group (SO3ꢀ or NH3+) in
the dye molecule assists in the preorganization of the structur-
al units to give specific dimeric complexes with a parallel
arrangement of the ethylene fragments (Scheme 1). Metal
cations with large ionic radii (Sr2+, Ba2+) and alkanediam-
monium compounds were also found to be able to assemble
unsaturated crown ethers into sandwich-like structures to
enable the PCA reaction to proceed.3
b Photochemistry Center, the Russian Academy of Sciences, 7A
Novatorov str., 119421 Moscow, Russian Federation.
E-mail: gromov@photonics.ru; Fax: +7 (495) 936 1255
c Department of Chemistry, University of Durham, South Road,
Durham, UK DH1 3LE. E-mail: j.a.k.howard@durham.ac.uk
Fax: +44 (0191) 373 374
w Electronic supplementary information (ESI) available: formation of
cyclobutane rctt-11, crystal structures and packings, crystal data, and
selected geometric parameters. See DOI: 10.1039/b615056j
z The HTML version of this article has been enhanced with colour
images.
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DMF under basic conditions. This reaction afforded the target
product 3 (yield 48%) along with the bisheterocyclic derivative
4, which is produced as a result of the Michael addition of a
second molecule of lepidine to the double bond of 3. It should
be noted that compound 4 was formed in a manner that is
unlike the similar condensation reaction between lepidine and
(4-formylbenzo)-15-crown-5 ether.5 Furthermore, using a five-
fold excess of lepidine was found to substantially increase the
yield of 4 (45 vs. 10%), which became the only product of the
reaction. The crown containing styryl dye, 5, was obtained
from 3 in a similar way to the synthesis of 2 from 1.
According to the vicinal coupling constants for the ethylene
3
bond protons, JH(a),H(b) = 15.7–16.1 Hz, compounds 1–3,
and 5 were obtained as E isomers.
1H NMR study
In solution, compound (E)-1 was revealed5 to be present as a
mixture of s-cis- and s-trans-conformers, which differ by the
orientation of dimethoxybenzene moiety with respect to ethy-
lene fragment of the molecule. Dyes 2 and 5 and the neutral
compound 3 have a similar conformational composition in
DMSO-d6 solution; this is confirmed by the presence of intense
NOE cross signals between protons H(20), H(60), H(a), and
H(b) (see Scheme 2 for atom numbering). Irradiation of
solutions of 1–3 and 5 with visible light only brings about
the reversible E–Z isomerization of the compounds about the
ethylene bond. This type of photoreaction has been observed
for the styryl dyes of a pyridine series, and in related com-
pounds studied by us previously.2b,e,6
Scheme 1 The precursor dimer for the PCA reaction, and examples
of the self-assembly in solution of two crown-ether stilbene-like
molecules.
This specific sandwich-like mutual arrangement of two units
may also be supported by a crystal lattice, consequently PCA
reactions are often observed in the solid state. It is obvious
that the PCA reaction should proceed inside the volume
specified by the initial dimer unit. Therefore, this reaction
may be accomplished without crystal degradation, which is to
say, as a single-crystal-to-single-crystal transformation. In the
last few years many observations of these processes in single
crystals have been reported.1f,4 However, so far systematic
investigations, and predictions as to the particular type of
crystal packing that permits such a transformation to occur
without crystal degradation, are lacking.
Herein we report the synthesis, 1H NMR and X-ray studies,
of the structure and PCA reaction for four new 4-styrylquino-
line compounds, namely, the neutral 1-quinolyl-2-phenylethy-
lenes 1 and 3, and the related cationic styryl dyes 2 and 5, and
the products of their PCA reactions, and some other related
compounds. Peculiarities in their crystal packing motifs and
geometric characteristics are also discussed.
Visible light irradiation of compounds 1, 2, and 5 as thin
polycrystalline films resulted in the relatively fast and sub-
1
stantial reduction in their colour. Analysis of H NMR data
for the photoproducts showed that the initial compounds
disappeared gradually and that in each case only a single
product was present in the final reaction mixture. For these
photoproducts, the signals for the protons and carbon atoms
of the ethylene bond are absent from the aromatic region of
the spectra, and two new signals appear at d 5.1–5.5 ppm (Fig.
1) and at d 43–50 ppm in the 1H and 13C NMR spectra,
respectively. The positions of these peaks are typical of the
cyclobutane derivatives of styryl dyes that have been observed
previously, and are known to form upon the photoirradiation
of these dyes.2b,e,6
Thus, the solid-phase photoreactions of 1, 2, and 5 gave rise
to cyclobutane derivatives 6, 7, and 9, respectively. The
presence of only one set of signals in the NMR spectra is
indicative of the formation of a single stereoisomer. The
proton signals due to the cyclobutane fragments within the
resulting photoadducts appear as symmetric AA0BB0 spin
systems (Fig. 1), with vicinal coupling constants of 9.1–10.5
and 5.6–7.0 Hz. The difference in the coupling constants is
associated with the difference in the endocyclic dihedral angles
in the cyclobutane moieties. Since the signals for the cyclobu-
tane protons comprise two doublets of doublets,6 the solid-
phase photocycloaddition affords the rctt stereoisomers of
cyclobutanes 6, 7, 9 and, hence, the cycloaddition of (E)-1,
(E)-2, and (E)-5 takes place within the syn-‘head-to-tail’
arrangement of the dimeric pairs (Scheme 3).
Results and discussion
Synthesis
The synthetic route for the preparation of the compounds is
presented in Scheme 2. Recently obtained5 4-styrylquinoline 1
was quaternized with ethyl p-toluenesulfonate, followed by
anion exchange with perchloric acid to give rise to the corre-
sponding styryl dye 2 in good overall yield. The new com-
pound 3 was synthesized by condensation of (4-formylbenzo)-
18-crown-6 ether with lepidine in a near equimolar ratio in
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Scheme 2 The synthetic route affording 4-styrylquinoline compounds 2, 3, 5 and the bisheterocycle 4.
benzene fragments, respectively, and for the protons of the
30-OCH2 group (DdH = 0.52–1.03 ppm). This suggests that the
quinoline residue is arranged under the benzocrown-ether
fragment in (Z)-3 in the predominant conformation shown
in Scheme 3. The above-mentioned protons are shielded by the
aromatic units and consequently the signals for these protons
appear at higher field compared to those of (E)-3.
It is interesting to compare the rates of cyclobutane forma-
tion in thin films of compounds 1–3 and 5. Irradiation of the
films under the same conditions (visible light, 10 h) resulted in
different extents of conversion to the cyclobutane derivatives
for these compounds, being much higher for 1 and 5 than for 2
and 3 (Table 1). This difference might arise due to the different
mutual arrangement of the two styryl molecules in the pre-
cursor dimeric pair and, hence, owing to the different distances
separating the CQC bonds that are to react. The results from
the X-ray study of dye 2 showed that a closed mutual
arrangement of the reacting molecules in the dimeric pair is
attained by inserting benzene solvate molecules into the crystal
lattice of the compound (see X-ray section). Preparation of a
thin film of 2 in the presence of benzene did lead to a
considerable increase in the extent of conversion to cyclobu-
tane rctt-7 (70 vs. 23%). Thus, altering the solvent of crystal-
lization allows ones to control the efficiency of the [2 + 2]-
photocycloaddition reaction in the solid state. It should be
noted that prolonged irradiation of the films of 1 and 5
resulted in complete photoconversion (total 20 h). In contrast
to this, complete photoconversion did not occur for 2 and 3
even after irradiation for a total of 150 h. This means that films
prepared from compounds 2 and 3 are probably a mixture of
crystals with different crystal packings, some of which are
unfavourable for PCA.
Fig. 1 The 1H NMR spectra (region of the cyclobutane protons) in
DMSO-d6 at 25 1C: (a) the product of the photoirradiation of (E)-1 as
a thin film for 20 h (rctt-6); (b) product of the photoirradiation of (E)-2
as a thin film for 35 h (rctt-7).
In contrast to compounds 1, 2, and 5, irradiation of a thin
film prepared from the crown-containing 4-styrylquinoline 3
led to cyclobutane rctt-8 formation, along with E - Z
isomerization of the initial compound (Scheme 3). The pre-
sence of the Z isomer of 3 in the reaction mixture is caused by
a special mutual arrangement of the molecules (E)-3 in the
solid state, affording a molecular arrangement that is less
favourable with respect to allowing the PCA reaction to
proceed (see also X-ray section). A change in the geometry
of the Z isomer compared to that of the E isomer results in a
substantial decrease in the conjugation within the chromopho-
ric fragment, and to a twist of this fragment due to the steric
interactions of the bulky aromatic substituents at the ethylene
1
bond. This is displayed in the H NMR spectrum as upfield
X-Ray diffraction study
shifts of the signals for the majority of the protons, the most
substantial shifts being observed for the protons of the ethy-
lene fragment, protons H(5) and H(20) of the quinoline and
Recently,6 we reported a solid phase PCA of the crown-ether
styryl dye of the pyridine series (E)-10 (Scheme 4) that
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Scheme 4 Structure of dye 10 (above), its crystal packing (middle)
and a schematic showing the structure of a stack of molecular
sandwiches (below).
two adjacent sandwiches are related by a symmetry center, but
in general they are spaced farther from one another than the
two molecules within a sandwich (d2 4 d1, see Scheme 4).
Moreover, the nearest ethylene groups to a given sandwich
belong to adjacent sandwiches, and are significantly shifted
with respect to each other within the parallel planes because
the b axis is inclined to the ethylene planes. It is important that
if the solid phase PCA reaction is accomplished within a
sandwich that no change in the local symmetry of crystal
occurs as a result of the transformation. Actually, the cyclo-
butane derivative 11 formed from 10 was generated as the rctt
centrosymmetric isomer (Scheme 1S, ESIw) and, therefore, the
symmetry of the single crystal after the reaction finished
turned out to be unchanged from the initial crystal.
Scheme 3 Solid-phase synthetic routes for the formation of cyclobu-
tanes rctt-6–9.
occurred without crystal degradation (Scheme 1S, ESIw). In
single crystals of the starting compound 10, charged dye
molecules are arranged in centrosymmetric syn-‘head-to-tail’
sandwiches, in which two ethylene units are in close vicinity to
each other. These sandwiches form stacks running along the b
axis (Scheme 4; ovals and R1 denote benzocrown-ether sub-
stituents and R2 denotes pyridine substituents at the ethylene
bonds).
Adjacent stacks are separated by a double layer of very
loosely packed crown-ether fragments. In a given stack, any
The above mentioned stacking type of crystal packing is the
most abundant (there are two forms of stacking: ‘head-to-tail’
and ‘head-to-head’), this is typical for crown-ether styryl and
butadienyl dyes.7 We suggested that PCA reactions in the solid
state, including those that proceed without crystal degrada-
tion, may be expected for the many compounds of this class
that display the ‘head-to-tail’ stacking motif in their crystal
packing. In order to check this idea, we performed an X-ray
structural analysis of an orange single crystal of styryl dye 2,
irradiated it with visible light, and then repeated the X-ray
structural investigation.
Table 1 The content of the photoproducts,a and the extent of
conversion of the reactants to cyclobutane derivatives, after irradia-
tion for 10 h of thin films of the 4-styrylquinolines 1–3, and 5
Photoproduct contenta/
molar ratio
rctt
Cyclobutane
E isomer Z isomer derivative
Conversion extent
into cyclobutane
derivative (%)
Initial
compound
(E)-1
(E)-2
(E)-2b
(E)-3
(E)-5
1
6.9
1
5.7
1
0
0
0
3.7
0
4.3
1
1.2
1
90
23
70
18
83
Structure of dye 2 and cyclobutane 7. The structure of the
benzene solvate of compound 2 is shown in Fig. 2. The dye
molecule is nearly planar. The dihedral angles between the
quinoline and ethylene groups, and between the ethylene and
2.5
a
1
From H NMR data. The film was prepared using benzene.
b
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Fig. 2 Structure of compound 2. Thermal ellipsoids are drawn at the
50% probability level.
benzene groups, are equal to 6.9 and 6.51, respectively. The
dihedral angle between the quinoline and benzene groups is
0.71. The bond lengths in the C(6)–C(9)–C(10)–C(11) fragment
are 1.460(2), 1.343(2), and 1.456(2) A, respectively, being
indicative of a rather localized CQC ethylene bond.
Compound 2 crystallizes in the space group P21/n. Benzene
solvate molecules occupy symmetry centers, so that half a
benzene molecule per dye molecule is found in this crystal. The
crystal packing of this compound, in two projections, is shown
in Fig. 3. The dye molecules are packed in stacks, with a
centrosymmetric ‘head-to-tail’ arrangement between any two
adjacent molecules, similar to the packing of dye 10 (Scheme
4). In this packing arrangement, adjacent stacks of sandwiches
are isolated from one another by perchlorate anions and
benzene solvate molecules.
Fig. 3 Crystal packing of 2 as viewed down the b axis (above) and
down the a axis (below).
1.615(12), 1.508(10), and 1.503(10) A, respectively. The bond
angles C(9)–C(10)–C(11), C(11)–C(10)–C(9A), C(9)–C(10)–
C(9A), C(6)–C(9)–C(10A), C(6)–C(9)–C(10), and C(10)–C(9)–
C(10A) are 113.1(6), 119.3(6), 90.2(6), 118.0(6), 117.2(6), and
89.8(6)1, respectively.
The structure of a single sandwich is shown in Fig. 4. The
interatomic distances between the ethylene carbon atoms
C(9)ꢂ ꢂ ꢂC(10B) and C(10)ꢂ ꢂ ꢂC(9B) are rather short, 3.492 A,
and satisfy the above mentioned geometric requirements for
the PCA reaction to occur.
It is interesting to note that not only the structural units
participating in the PCA changed their positions within the
crystal unit cell. Fig. 6 shows a superposition of the same areas
of the unit cell in the initial compound 2, and the product of its
PCA transformation, 7. The perchlorate anions and the
benzene molecules have also changed their positions. The
benzene molecules and perchlorate anions create a soft flexible
shell around the sandwiches (see Fig. 3), and thus can com-
pensate somewhat for the stress that is generated in the crystal
as the result of the large atomic displacements that happen
within the sandwiches during the course of the PCA reaction.
In the above mentioned single-crystal-to-single-crystal trans-
formation 10 - 11 the function of the ‘soft environment’ was
performed by the crown-ether moieties and perchlorate anions
that were wrapped about the stacks. These species also chan-
ged their geometry within crystal as a result of the PCA
transformation.
After finishing the data collection, the single crystal was
taken off the diffractometer and subjected to irradiation with
visible light over a period of 30 h. The crystal became much
lighter in colour. Then this single crystal was mounted back on
the diffractometer and a second X-ray data collection was
performed. The complete conversion of the initial compound 2
into the rctt isomer of cyclobutane 7 had occurred (Fig. 5).
The molecule rctt-7 is situated on the symmetry center; the
formation of the product compound in the single crystal does
not destroy the crystal symmetry. The crystal system and the
space group have remained as for 2, that is, monoclinic P21/n.
During the PCA reaction, the volume of the crystal unit cell
was insignificantly increased from 2172.1(3) A3 for 2 to
2206.2(4) A3 for 7, a 1.6% increase.
It should be added that our attempts to monitor the PCA
reaction in 2 failed. X-Ray data collected on the initial crystal
after 6 and 15 h of irradiation resulted only in structural
models displaying an increase in thermal displacement para-
meters for all atoms, and only after 30 h of irradiation were
The dihedral angle between the quinoline and benzene
fragments [N(1). . .C(11)–C(19) and C(3A). . .C(8A)] is equal
to 25.71. The bond distances C(9)–C(10A), C(9)–C(10),
C(6)–C(9), and C(10)–C(11) are equal to 1.568(10),
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Fig. 6 Superposition of the same areas of crystal unit cell for 2
(dashed lines) and 7 (solid lines); the additional letter ‘A’ indicates that
atoms are at (1 ꢀ x, 1 ꢀ y, 1 ꢀ z).
Fig. 4 Structure of a sandwich of 2 in two projections. In the below
projection the upper molecule is drawn with hollow lines, and all
hydrogen atoms are omitted for clarity; the additional letter ‘B’
indicates that atoms are at (1 ꢀ x, 1 ꢀ y, 1 ꢀ z).
meters for 7a are as follows: bond lengths C(3)–C(10), C(10)
–C(11A), C(10)–C(11), C(11)–C(12) are 1.504(3), 1.552(3),
1.587(3), 1.507(3) A; bond angles C(3)–C(10)–C(11A),
C(3)–C(10)–C(11), C(11)–C(10)–C(11A), C(12)–C(11)–C(10A),
C(10)–C(11)–C(12), C(10)–C(11)–C(10A) are 120.1(2), 118.7(2),
90.8(1), 117.2(2), 120.0(2), 89.2(1)1, respectively. The torsion
angle C(3)–C(10)–C(11A)–C(12A) is equal to 112.01, and the
dihedral angle between the quinoline N(1)–C(11). . .C(19) and
benzene C(12A). . .C(17A) planes, is 54.91. These data show
that the differences between the angular parameters found in 7
and in 7a are significant. Fig. 8 clearly demonstrates this
difference.
informative data obtained. Perhaps a reason for these findings
is that the reaction starts slowly at a localised site, most likely
within a defect of the crystal lattice, and then the PCA
transformation proceeds rapidly throughout the remainder
of the crystal.
Structure of cyclobutane 7a. It was of interest to compare the
geometry of cyclobutane 7 obtained in the course of a solid
phase PCA, with that of a crystal of 7 grown from solution.
Such crystals were obtained by recrystallization of rctt-7 from
a MeCN–benzene mixture. The resultant crystals belong to the
Thus, the geometry of the organic skeleton of 7 obtained as
a result of the solid phase PCA reaction is rather stressed. This
geometry cannot be reproduced in solution. Therefore, crys-
tals of 7 belonging to the monoclinic space group P21/n cannot
be crystallized from solution, instead they are only formed as a
result of a single-crystal-to-single-crystal PCA reaction.
ꢀ
triclinic P1 space group; the structure of this compound (7a) is
shown in Fig. 7. Compound 7a is also a benzene solvate, but
the rctt-7 : benzene ratio turned out to be different from the
ratio seen for compound 7 obtained from the PCA reaction, 1 :
3 vs. 1 : 1.
The rctt isomer of the substituted cyclobutane, and one of
the benzene solvate molecules, are situated at symmetry
centers; the other benzene molecules and the perchlorate
anions occupy general positions. Selected geometric para-
Other possible packing motifs in styryl dyes and their neutral
precursors. In general, styryl dyes display only two types of
Fig. 5 Structure of the rctt cation of compound 7; the additional
letter ‘A’ indicates that atoms are at (1 ꢀ x, 1 ꢀ y, 1 ꢀ z).
Fig. 7 The structure of rctt-7a; the additional ‘A’ letter indicates that
atoms are at (1 ꢀ x, ꢀy, 1 ꢀ z).
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Scheme 6 Stacks of unsaturated molecules formed via mirror planes
(left side), two-fold axes (middle), and a combination of a two-fold
axis with symmetry center (right side).
Fig. 8 Superposition of the cyclobutane molecules in 7 (hollow lines)
and 7a (dashed lines).
crystal packing, but both incorporate stacks of the dye mole-
cules. One type involves the ‘head-to-tail’ stacking of the
molecules (Scheme 4),6,7a–d and the other is ‘head-to-head’
stacking.7b,e In the latter packing motif, any two adjacent
molecules are related by translation (Scheme 5). This motif is
usually characterized by a significant shift of two adjacent
molecules that lie in parallel planes with respect to each other,
so that the ethylene bonds in these molecules are well spaced
from one another. Even if the adjacent molecules were not
shifted, the PCA reaction between any two adjacent molecules
would result in an alteration in the local symmetry of the
crystal, a development which would create a set of defects
within the crystal lattice that would eventually lead to crystal
degradation. However, nothing prevents this reaction from
proceeding successfully in solution.3
does not restrict the twist of two adjacent ethylene bonds
about a theoretical axis joining the middles of the ethylene
bonds. This symmetry also permits a relatively small twist in
the mutual arrangement of the ethylene groups (case b rather
than case a, Scheme 7) to give a close to optimal disposition
for the PCA reaction to occur.
In most cases the twist of two conjugated molecules with E
configuration about a line joining the middles of the ethylene
bonds means less efficient overlapping of the conjugated
systems (Scheme 7, a and b) with respect to the centrosymme-
trically or mirror-plane related molecules (Scheme 7, c). There-
fore, if stacking interactions and Coulomb repulsion forces are
important in molecular self-assembly, it is most likely that the
centrosymmetric dimers form, rather than dimers in which the
molecules are related by 2-fold axes or mirror-planes. In
principle, a specific case could arise in which a relatively small
twist in the ethylene moieties allows for orbital overlap.
Such an arrangement should bring about the rtct isomer of
cyclobutane derivative as a result of the PCA reaction. How-
ever, we observed this geometry of the styryl dye dimers, and
the subsequent formation of the rtct-cyclobutanes, only in
solution.2b,d
In principle, one may deduce other variations in the sym-
metry relationships between adjacent molecules in a stack that
would not result in a local symmetry infraction during the
course of a PCA solid phase reaction (Scheme 6).
In the left-hand stack in Scheme 6 the molecules are related
by mirror planes. In reality this variant cannot be achieved in
crystals formed by molecules with essential intramolecular
charge separation because with this symmetry identically
charged moieties of two adjacent molecules within a stack
are in the vicinity of each other, which is not optimal because
this arrangement is associated with a high degree of electro-
static repulsion. Indeed, we never observe this type of molecule
packing for styryl dyes and related compounds.
In the middle stack in Scheme 6 the molecules are related by
two-fold axes. In general, this symmetry means a mutually
crossed arrangement of two adjacent ethylene bonds, which is
not optimal for the PCA reaction. However, 2-fold symmetry
Scheme 7 Possible mutual arrangements of styryl dye molecules in
dimeric pair. Here circles denote phenyl substituents and triangles are
heterocyclic moieties.
Scheme 5 ‘Head-to-head’ crystal packing motif.
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The right-hand case in Scheme 6 represents molecular stacks
that are generated by a combination of two-fold axes and
symmetry centers. This type of packing motif has been ob-
served previously within crystals of a KI complex of a 15-
crown-5-ether styryl dye of the quinoline series.8 In this
crystal, 2-fold related crown-ether dye sandwiches formed
via interactions of the crown-ether fragments with the K+
ions are observed (Fig. 1S, ESIw). Only the quinoline frag-
ments of the dye molecules overlap in these sandwiches. In the
crystal these sandwiches are packed in stacks. Any two
adjacent sandwiches in a stack are related by symmetry
centers, and have short interatomic distances between the
ethylene bonds, and extensive overlapping over the conjugated
systems. This geometry might only allow the solid phase PCA
reaction to occur between the sandwiches rather than inside
them. However, no cases of two-fold related units within a
stack were observed in styryl compounds without foreign
support (e.g. metal cations).
Fig. 9 A fragment of crystal packing of 1.
Single crystal of the initial compound 1 belongs to the
monoclinic crystal system and the P21/c space group. A
fragment of the crystal packing is shown in Fig. 9. It can be
seen that the molecular packing displays the parquet sandwich
motif c (see Scheme 8). In a centrosymmetric sandwich unit
(Fig. 3S, ESIw) the ethylene fragments are situated in parallel
planes, and the C(10A)ꢂ ꢂ ꢂC(11E) and C(11A)ꢂ ꢂ ꢂC(10E) inter-
planar distances between the ethylene carbon atoms (Fig. 9)
are equal to 3.629 A. These geometric parameters satisfy the
aforementioned geometric conditions to enable the PCA reac-
tion to happen.
Contrary to styryl dyes, their neutral precursors, 1-hetaryl-
2-phenylethylenes, are usually characterized5,7d by three pack-
ing motifs: staircase (a), parquet (b), and parquet sandwich (c)
(Scheme 8). No stacking motifs that are characteristic of styryl
dyes were observed for these compounds. However, in the
parquet sandwich packing motif c, centrosymmetric sand-
wiches pre-organized towards the PCA reaction occur. Pre-
viously,5 we have performed an X-ray structural
determination of 4-styrylquinoline 1 and established that a
parquet sandwich packing motif, with centrosymmetric ‘head-
to-tail’ sandwiches, is present in the crystals. We presumed
that the single-crystal-to-single-crystal PCA might be observed
for this compound too. In order to check this idea we
performed an X-ray investigation of a single crystal of com-
pound 1, followed by its irradiation with visible light, and then
repeated the X-ray determination.
After the data collection with a single crystal of 1 was
completed, this single crystal was taken off the diffractometer
and subjected to irradiation with visible light for 6 h. It has
become lighter in colour. This single crystal was then re-
mounted on the diffractometer, and the X-ray structural
experiment was repeated.
The result of irradiation of 1 for 6 h is shown in Fig. 10. Two
compounds, 1 and 6, simultaneously occur in the same single
crystal in the ratio 0.66 : 0.34. The centrosymmetric rctt isomer
of cyclobutane 6 is partly formed as a result of the PCA
reaction that occurs in the single crystal of 1. The formation of
this isomer does not affect the local symmetry of the crystal.
Significant atomic displacements during the course of the
reaction do not alter the crystal environment of the sandwich
because they proceed inside the volume specified by the initial
sandwich. The geometric parameters for the central fragment
of the substituted cyclobutane product are as follows: bond
lengths C(30)–C(100) 1.519(12), C(100)–C(110) 1.560(7), C(110)–
C(120) 1.504(16), C(100)–C(11B) 1.610(8) A; bond angles
C(30)–C(100)–C(110) 117.9(7), C(30)–C(100)–C(11B) 115.4(6),
C(110)–C(100)–C(11B) 90.7(4), C(100)–C(110)–C(120) 118.0(7),
C(120)–C(110)–C(10B) 114.0(5), C(100)–C(110)–C(10B) 89.3(4)1;
torsion angle C(120)–C(110)–C(100)–C(30) 123.51.
Structure of quinolylphenylethylene 1 and cyclobutane 6. The
molecule of the light yellow compound 1 is nearly planar (Fig.
2S, ESIw). The dihedral angles between the ethylene group
C(3)–C(10)–C(11)–C(12) and its substituents, the quinoline
and benzene fragments, are equal to 16.0 and 16.61, whereas
the dihedral angle between the planes of the quinoline and
benzene moieties is 2.31. The geometric parameters in the
ethylene unit have the following values: the C(3)–C(10),
C(10)–C(11), and C(11)–C(12) bond lengths are equal to
1.471(1), 1.341(2), and 1.469(2) A, respectively; the angles
C(3)–C(10)–C(11) and C(10)–C(11)–C(12) are 123.8(1) and
127.1(1)1, respectively; the torsion angle C(3)–C(10)–C(11)–
C(12) is 179.81. These values agree well with those observed by
us in our previous X-ray determination of this compound.5
Interestingly, in crystals of quinoline 1 the PCA reaction
required less than 6 h of irradiation to start, whereas, in our
previous experiments with the related dye 2, the reaction
required a much longer exposure. It should be noted that
the crystal of this compound does not contain other structural
units (such as the perchlorate anions and solvate benzene
molecules in 2) that could create a flexible shell around the
sandwich unit. It is likely that a parquet sandwich packing
motif provides a more spacious environment for the molecular
sandwiches than a stacking packing motif.
Scheme 8 Packing motifs in crystals of 1-hetaryl-2-phenylethylenes:
staircase (a), parquet (b), and parquet sandwich (c). Solid lines denote
the profiles of the conjugated fragments of the molecules.
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.
Structure of cyclobutane 6 2HClO4. It was of interest to
know whether it is possible to grow crystals of 6 from solution
that are of the same polymorphic form as those obtained from
the PCA reaction. Our attempts to grow crystals of 6 from
different solutions turned out to be successful only in the
presence of perchloric acid. The compound crystallized as a
.
salt 6 2HClO4, the crystals of which belong to the triclinic
ꢀ
space group P1 with Z = 2. The structure of formula units is
shown in Fig. 12. The cation of the compound occupies a
general position within the unit cell. Both nitrogen atoms are
protonated. Although the compound is a salt rather than a
neutral compound, we may expect that the geometric para-
meters for the central parts of the substituted cyclobutanes
formed from quinolines 1 and 2 should be identical.
Fig. 10 The X-ray structure of 1/6 obtained after 6 h irradiation of 1.
The atoms belonging to 6 are connected by hollow lines; the additional
letter ‘A’ or ‘B’ indicates that atoms are at (3 ꢀ x, 1 ꢀ y, 1 ꢀ z). The
thermal ellipsoids are drawn at the 50% probability level.
The bond lengths in the cyclobutane fragment of the cation
.
in 6 2HClO4 are insignificantly different to these in 6:
C(10)–C(11) and C(29)–C(30) are 1.544(4) and 1.554(4) A,
C(10)–C(30) and C(11)–C(29) are 1.584(4) and 1.579(4) A,
C(3)–C(10) and C(22)–C(29) are 1.493(4) and 1.485(4) A, C(11)
–C(12) and C(30)–C(31) are 1.499(4) and 1.490(4) A, respec-
tively. Whereas the bond and dihedral angles have markedly
different values: C(3)–C(10)–C(11) and C(22)–C(29)–C(30) are
both 120.1(2)1, C(3)–C(10)–C(30) and C(11)–C(29)–C(22) are
120.3(2) and 119.7(2)1, C(10)–C(11)–C(12) and C(29)–C(30)
–C(31) are 116.5(2) and 114.8(2)1, C(12)–C(11)–C(29) and
C(10)–C(30)–C(31) are 122.5(2) and 123.3(2)1, respectively,
torsion angles C(3)–C(10)–C(11)–C(12) and C(22)–C(29)–
C(30)–C(31) are 106.6 and ꢀ108.31, respectively, and dihedral
angles N(1)–C(1). . .C(9)/C(12). . .C(17) and N(2)–C(20). . .
C(28)/C(31). . .C(36) are 60.6 and 65.01, respectively. Interest-
ingly, the dihedral angles between the aromatic moieties in this
molecule (60.6 and 65.01) are markedly greater than the
corresponding value (54.91) in cyclobutane 7a.
The difference in the geometry of the substituted cyclobu-
tanes 6 and 6 ꢂ 2HClO4 is well demonstrated in Fig. 13. This
significant difference in geometry shows that in crystals of 6
the molecular structure is stressed. This stressed geometry
cannot be reproduced in solution. Hence, crystals belonging
to the monoclinic space group P21/c with geometric para-
meters close to those in 6 cannot be obtained from solution.
After conducting the second X-ray experiment, this parti-
cular single crystal was taken off the diffractometer and
subjected to further irradiation for 24 h. The single crystal
became colourless. It was then mounted on the diffractometer
again, and its X-ray structure determined for the third time.
After the irradiation of compound 1 for a total of 30 h, full
PCA transformation of the initial compound 1 to the rctt
isomer of cyclobutane 6 was observed. The structure of the
product compound is shown in Fig. 11. The rctt isomer of
cyclobutane 6 is situated at the symmetry center. It is impor-
tant that the formation of this new compound in the single
crystal does not destroy crystal symmetry. The crystal system
and the space group remain as for 1, that is, monoclinic P21/c.
The dihedral angle between the quinoline and benzene
fragments [N(1)–C(1). . .C(9) and C(12A). . .C(17A)] is equal
to 16.01. The geometric parameters for the central fragment of
the substituted cyclobutane product are as follows: bond
lengths C(3)–C(10) 1.505(3), C(10)–C(11A) 1.549(3),
C(11)–C(12) 1.510(3), C(10)–C(11) 1.603(3) A; bond angles
C(3)–C(10)–C(11A) 119.9(2), C(3)–C(10)–C(11) 113.6(2),
C(11)–C(10)–C(11A) 90.3(2), C(10A)–C(11)–C(12) 118.1(2),
C(10)–C(11)–C(12) 115.3(2), C(10)–C(11)–C(10A) 89.7(2)1;
torsion angle C(3)–C(10)–C(11A)–C(12A) ꢀ123.51.
During the PCA reaction the volume of the crystal unit cell
is insignificantly decreased from 1457.39(7) A3 in 1 to
1444.8(3) A3 in 6, a change in volume corresponding to 0.9%.
Structure of quinolylphenylethylene 3. The nearest relative of
quinoline 1 is its 18-crown-6-containing analogue 3. We have
managed to grow crystals of compound 3 but only in a
Fig. 11 The structure of compound 6 obtained after 30 h irradiation
of 1; the additional letter ‘A’ indicates that atoms are at (2 ꢀ x, 2 ꢀ y,
1 ꢀ z). Thermal ellipsoids are drawn at the 50% probability level.
Fig. 12 The structure of 6 ꢂ 2HClO4. Thermal ellipsoids are drawn at
the 50% probability level.
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pates in a hydrogen bond with the water molecule (the
Cl(1)ꢂ ꢂ ꢂO(1S) distance is 3.343 A). In turn the water molecule
forms at least two more bifurcate hydrogen bonds with atoms
O(1) and O(6) of a crown-ether fragment of a translation-
related molecule of 3. The corresponding Hꢂ ꢂ ꢂO distances are
2.37 and 2.53 A and the angles O–Hꢂ ꢂ ꢂO(1)/O(6) are equal to
155, 1421. It is this system of hydrogen bonds that defines the
staircase packing motif.
In the two nearest centrosymmetrically related molecules of
3 that are in adjacent staircases, the linear ethylene groups are
not projected onto one another (Fig. 16), and their carbon
atoms C(10A), C(11B) and C(11A), C(10B), are spaced at a
distance of 4.945 A from each other, a distance that exceeds
the above mentioned upper limit for the PCA reaction to be
possible.
Fig. 13 Superposition of cyclobutane units in 6 (full lines) and
6 ꢂ 2HClO4 (dashed lines). All hydrogen atoms are omitted for clarity.
These data mean that the PCA reaction is impossible in this
single crystal. Just in case, the compound was subjected to
irradiation with visible light for a period of two weeks without
any change in the crystal, as expected.
solvated form incorporating water and dichloromethane
molecules. The X-ray structure of this compound is shown
in Fig. 14.
The presence of the solvate molecules, water and dichlor-
omethane, which tend to form hydrogen bonds, significantly
affects the geometry of the molecule of 3 and its packing
arrangement in the crystal. First of all, the molecule is not
planar: the dihedral angle between the quinoline and benzene
substituents of the ethylene group is equal to 55.01, between
the ethylene group and benzene ring it is 13.31, and between
the ethylene and quinoline groups it is 41.71. Thus, the quino-
line residue is strongly twisted from the styrene mean plane.
Additionally, the packing motif exhibited in the crystal struc-
ture of this compound cannot be classified as one of the above
mentioned packing motifs that are typical for 1-hetaryl-2-
phenylethylenes. In these motifs all the conjugated moieties
are usually planar.5,7d
Conclusions
Solid phase PCA reactions involving styryl dyes, including
those that proceed without crystal degradation, can be accom-
plished in many of the compounds reported herein that exhibit
the ‘head-to-tail’ molecular stacking motif in their crystal
packing. The stacks comprise molecular sandwiches, with
In the crystal adjacent molecules of 3 are related by transla-
tions along the b axis to give a staircase packing motif (Fig. 4S,
ESIw). Two adjacent staircases are related by symmetry cen-
ters. The staircase arrangement is due to a system of hydrogen
bonds in which the crown-ether fragments, water and dichloro-
methane molecules all participate (Fig. 15). Both hydrogen
atoms of the dichloromethane molecule form bifurcate hydro-
gen bonds with atoms O(2), O(3) and O(5), O(6) of the crown-
ether fragment (the corresponding Hꢂ ꢂ ꢂO distances are 2.51,
2.59 and 2.67, 2.55 A). Atom Cl(1) of this molecule partici-
Fig. 15 Two projections of two adjacent molecules of 3 in a staircase;
the additional ‘A’ letter indicates that atoms are at (x, 1 + y, z).
Hydrogen bonds are shown as dashed lines. Hydrogen atoms of 3 that
are not involved in secondary interactions are omitted for clarity.
Fig. 14 The structure of 3. Thermal ellipsoids are drawn at the 50%
probability level.
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reference; 1H–1H COSY and NOESY spectra and 1H–13C
COSY (HSQC and HMBC) spectra were used to assign the
proton and carbon signals.y Absorption spectra were mea-
sured on a UV-3101PC spectrophotometer (Shimadzu) in the
range of 200–550 nm with an increment of 0.5 nm. The mass
spectra were obtained on a Varian MAT 311A instrument
with direct inlet of the sample into the ionization source; the
ionization energy was 70 eV. Elemental analyses were per-
formed at the microanalytical laboratory of the A. N. Nes-
meyanov Institute of Organoelement Compounds (Moscow,
Russian Federation); the samples for elemental analyses were
dried in vacuo at 80 1C.
Preparations
Lepidine, veratraldehyde, (4-formylbenzo)-18-crown-6 ether,
ethyl p-toluenesulfonate, and anhydrous DMF were used as
received (Aldrich, Merck).
4-[(E)-2-(3,4-Dimethoxyphenyl)ethenyl]quinoline ((E)-1). This
was prepared by the condensation of lepidine with veratralde-
hyde in anhydrous DMF in the presence of t-BuOK; yellowish
crystals (yield 46%), mp 130–132 1C (lit. data:5 mp 130–132
1C). 1H NMR (CDCl3, 30 1C) d: 3.96 (s, 3H, 40-MeO), 4.01 (s,
3H, 30-MeO), 6.95 (d, J = 8.2 Hz, 1H, H(50)), 7.20 (d, J = 1.6
Hz, 1H, H(20)), 7.23 (dd, J = 8.2 Hz, J = 1.6 Hz, 1H, H(60)),
7.39 (d, J = 15.9 Hz, 1H, H(b)), 7.66 (m, 1H, H(6)), 7.68 (d,
J = 4.8 Hz, 1H, H(3)), 7.70 (d, J = 15.9 Hz, 1H, H(a)), 7.81
(m, 1H, H(7)), 8.29 (m, 2H, H(5), H(8)), 8.89 (d, J = 4.8 Hz,
Fig. 16 Two centrosymmetrically related molecules of 3 in different
projections; the additional letter ‘B’ indicates that atoms are at (2 ꢀ x,
1 ꢀ y, 1 ꢀ z). All hydrogen atoms and solvate molecules are omitted
for clarity.
13
1H, H(2)). C NMR (DMSO-d6, 30 1C) d: 55.44 (40-OMe),
55.61 (30-OMe), 109.86 (C(20)), 111.57 (C(50)), 116.05 (C(3)),
119.74 (C(a)), 121.50 (C(60)), 124.11 (C(5)), 125.68 (C(10)),
126.17 (C(6)), 129.17 (C(7)), 129.30 (C(10)), 129.38 (C(8)),
135.02 (C(b)), 142.40 (C(4)), 148.28 (C(9)), 148.97 (C(30)),
149.64 (C(40)), 150.02 (C(2)). UV-Vis (c = 5 ꢃ 10ꢀ5 M, MeCN,
22 1C) lmax: 353 nm (e = 29 500 Mꢀ1 cmꢀ1).
shorter distance between the ethylene fragments inside a
sandwich than between adjacent sandwiches. The general
problem of unpredictability in the crystal packing is overcome
here, based on the general observation that compounds of this
class form only stacking packing motifs, the ‘head-to-tail’
stacking that is favorable for PCA reactions being more
abundant than the ‘head-to-head’ stacking packing arrange-
ment that is unfavorable for PCA. The presence of benzene
solvate molecules, together with perchlorate anions, that are
able to rotate within the crystal are important for creating a
soft flexible shell about each sandwich. This shell permits
significant atomic displacements to occur during the course
of the PCA transformation by ‘absorbing’ the lattice stress
caused by these displacements. Analogous PCA reactions also
can be accomplished in related neutral compounds, 1-hetaryl-
2-phenylethylenes. However, in this case only one of three
typical packing motifs turned out to be favorable for the solid
phase PCA, enabling the reaction to proceed without crystal
degradation, and this was the parquet sandwich motif.
4-[(E)-2-(3,4-Dimethoxyphenyl)ethenyl]-1-ethylquinolinium
perchlorate ((E)-2). A mixture of compound (E)-1 (103 mg;
0.35 mmol) and ethyl p-toluenesulfonate (212 mg; 1.06 mmol)
was heated at 120 1C (oil bath) for 2 h. The resulting red mass
was extracted with hot benzene (10 mL) and the insoluble
residue was decanted and then dissolved in methanol (5 mL).
Then 70% aq. HClO4 (61 mL; 0.71 mmol) was added to the
methanolic solution and after cooling to ꢀ10 1C, the precipi-
tate formed and was filtered and washed with cold methanol
(3 ꢃ 2 mL) to give dye (E)-2 as orange powder in 71% overall
yield; mp 168–171 1C. 1H NMR (DMSO-d6, 25 1C) d: 1.60 (t,
J = 7.2 Hz, 3H, MeCH2), 3.86 (s, 3H, 40-MeO), 3.92 (s, 3H,
30-MeO), 5.00 (q, J = 7.2 Hz, 2H, CH2), 7.11 (d, J = 8.1 Hz,
1H, H(50)), 7.50 (dd, J = 8.1 Hz, J = 2.3 Hz, 1H, H(60)), 7.66
(d, J = 2.3 Hz, 1H, H(20)), 8.05 (m, 1H, H(6)), 8.16 (d, J =
15.9 Hz, 1H, H(b)), 8.20 (d, J = 15.9 Hz, 1H, H(a)), 8.26 (m,
1H, H(7)), 8.45 (d, J = 6.6 Hz, 1H, H(3)), 8.53 (d, J = 8.6 Hz,
1H, H(8)), 9.07 (d, J = 8.1 Hz, 1H, H(5)), 9.33 (d, J = 6.6 Hz,
1H, H(2)). 13C NMR (DMSO-d6, 30 1C) d: 14.96 (MeCH2),
51.87 (CH2), 55.58 (40-MeO), 55.75 (30-MeO), 110.54 (C(20)),
111.57 (C(50)), 115.74 (C(3)), 117.07 (C(a)), 118.80 (C(8)),
124.20 (C(60)), 126.45 (C(10)), 126.73 (C(5)), 128.29 (C(10)),
Experimental
General methods
The melting points were measured with a MEL-Temp II
apparatus with in a capillary, and are uncorrected. The 1H
and 13C NMR spectra were recorded on a Bruker DRX500
instrument in DMSO-d6 or CDCl3 using the solvent as internal
y See Scheme 2 for atom numbering.
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128.82 (C(6)), 134.94 (C(7)), 137.53 (C(9)), 143.51 (C(b)),
146.70 (C(2)), 149.05 (C(30)), 151.49 (C(40)), 152.99 (C(4)).
UV-Vis (c = 5 ꢂ 10ꢀ5 M, MeCN, 22 1C) lmax: 440 nm (e =
23 200 Mꢀ1 cmꢀ1). Anal. calcld for C21H22ClNO6: C, 60.07; H,
5.28; N, 3.34; found: C, 59.93; H, 5.49; N, 3.20%.
C(5)), 126.08 (2 C(6)), 127.01 (2 C(10)), 128.76 (2 C(7)), 129.60
(2 C(8)), 135.29 (C(10)), 145.78 (2 C(9)), 146.66 (C(40)), 147.75
(2 C(4), C(30)), 149.64 (2 C(2)). UV-Vis (c = 5 ꢃ 10ꢀ5 M,
MeCN, 22 1C) lmax: 274 nm (e = 13 400 Mꢀ1 cmꢀ1). MS
(Irel (%)) m/z: 609 (23), 608 [M]+ (61), 467 (29), 466 (100), 378
(18), 290 (15), 154 (95), 143 (31), 142 (20), 115 (12). Anal. calcd
for C37H40N2O6: C, 73.00; H, 6.62; N, 4.60; found: C, 73.17;
H, 6.64; N, 4.56%.
4-[(E)-2-(2,3,5,6,8,9,11,12,14,15-Decahydro-1,4,7,10,13,16-
benzohexaoxacyclooctadecin-18-yl)-1-ethenyl]quinoline ((E)-3)
and 4-[2-(2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10,13,16-ben-
zohexaoxacyclooctadecin-18-yl)-3-(4-quinolyl)propyl]quinoline
(4). A mixture of lepidine (0.43 mL, 3.0 mmol) and potassium
tert-butoxide (prepared by dissolution of potassium (0.127 g,
3.2 mmol) in dry tert-butyl alcohol followed by concentration
to dryness), in anhydrous DMF (15 mL) was stirred at room
temperature for 30 min. Then (4-formylbenzo)-18-crown-6
ether (1.00 g, 2.9 mmol) was added and the reaction mixture
was stirred at room temperature for 25 h. After adding water
(150 mL), the reaction mixture was extracted with benzene (4
ꢃ 70 mL), the organic extracts were concentrated in vacuo at
90 1C, and the residue was chromatographed on a column with
Al2O3 (Aluminium oxide 150 basic, Typ E, 0.063–0.200 mm,
Merck) using an acetonitrile–benzene gradient (up to 50% of
the former) as the eluent. Two fractions were collected. The
first contained compound (E)-3 (0.65 g, 48%) as yellowish
4-[(E)-2-(2,3,5,6,8,9,11,12,14,15-Decahydro-1,4,7,10,13,16-
benzohexaoxacyclooctadecin-18-yl)ethenyl]-1-ethylquinolinium
perchlorate ((E)-5). A mixture of compound (E)-3 (46 mg, 0.1
mmol) and ethyl p-toluenesulfonate (60 mg; 0.3 mmol) was
heated at 120 1C (oil bath) for 3 h. The resulting mass was
extracted with hot benzene (4 ꢃ 20 mL) and the insoluble
residue was decanted and then dissolved in a minimal quantity
of hot ethanol. Then 70% aq. HClO4 (13 mL, 0.15 mmol) was
added to the ethanolic solution and after cooling to ꢀ10 1C,
the precipitate formed and was filtered to give dye (E)-5 as an
orange powder (33 mg, 54% overall yield); mp 136–139 1C. 1H
NMR (DMSO-d6, 25 1C) d: 1.59 (t, J = 7.2 Hz, 3H, Me), 3.55
(s, 4H, 2 OCH2), 3.58 (m, 4H, 2 OCH2), 3.65 (m, 4H, 2 OCH2),
3.80 (m, 2H, 40-OCH2CH2), 3.84 (m, 2H, 30-OCH2CH2), 4.19
(m, 2H, 40-OCH2), 4.27 (m, 2H, 30-OCH2), 4.99 (q, J = 7.2
Hz, 2H, CH2N), 7.11 (d, J = 8.2 Hz, 1H, H(50)), 7.47 (dd, J =
8.2 Hz, J = 1.8 Hz, 1H, H(60)), 7.68 (d, J = 1.8 Hz, 1H,
H(20)), 8.04 (m, 1H, H(6)), 8.12 (d, J = 15.7 Hz, 1H, H(b)),
8.19 (d, J = 15.7 Hz, 1H, H(a)), 8.26 (m, 1H, H(7)), 8.44 (d,
J = 6.6 Hz, 1H, H(3)), 8.53 (d, J = 8.6 Hz, 1H, H(8)), 9.07 (d,
J = 8.2 Hz, 1H, H(5)), 9.33 (d, J=6.6 Hz, 1H, H(2)). 13C
NMR (DMSO-d6, 30 1C) d: 14.98 (Me), 51.90 (CH2N), 68.17
(40-OCH2), 68.35 (30-OCH2), 68.46 (40-OCH2CH2), 68.60 (30-
OCH2CH2), 69.61 (OCH2), 69.71 (3 OCH2), 69.83 (OCH2),
69.86 (OCH2), 111.62 (C(20)), 112.54 (C(50)), 115.73 (C(3)),
117.11 (C(a)), 118.81 (C(8)), 124.38 (C(60)), 126.45 (C(10)),
126.75 (C(5)), 128.30 (C(10)), 128.82 (C(6)), 134.96 (C(7)),
137.54 (C(9)), 143.46 (C(b)), 146.70 (C(2)), 148.36 (C(30)),
150.90 (C(40)), 152.98 (C(4)). UV-Vis (c = 5 ꢃ 10ꢀ5 M, MeCN,
22 1C) lmax: 434 nm (e = 33 900 Mꢀ1 cmꢀ1). Anal. calcd for
C29H36ClNO10 ꢃ H2O: C, 56.91; H, 6.26; N, 2.29; found: C,
56.79; H, 6.11; N, 2.13%.
1
powder, mp 88–90 1C (from hexane). H NMR (DMSO-d6,
25 1C) d: 3.55 (s, 4H, 2 CH2O), 3.58 (m, 4H, 2 CH2O), 3.64
(m, 4H, 2 CH2O), 3.79 (m, 2H, 40-OCH2CH2), 3.82 (m, 2H, 30-
OCH2CH2), 4.14 (m, 2H, 40-OCH2), 4.24 (m, 2H, 30-OCH2),
7.01 (d, J = 7.9 Hz, 1H, H(50)), 7.28 (dd, J = 7.9 Hz, J = 1.8
Hz, 1H, H(60)), 7.52 (d, J = 1.8 Hz, 1H, H(20)), 7.52 (d, J =
15.9 Hz, 1H, H(b)), 7.66 (m, 1H, H(6)), 7.78 (m, 1H, H(7)),
7.81 (d, J = 4.9 Hz, 1H, H(3)), 7.96 (d, J = 15.9 Hz, 1H,
H(a)), 8.03 (d, J = 7.9 Hz, 1H, H(8)), 8.55 (d, J = 8.5 Hz, 1H,
H(5)), 8.86 (d, J = 4.9 Hz, 1H, H(2)). 13C NMR (DMSO-d6,
30 1C) d: 68.10 (40-OCH2), 68.24 (30-OCH2), 68.59
(40-OCH2CH2), 68.68 (30-OCH2CH2), 69.71 (4 OCH2), 69.81
(2 OCH2), 111.09 (C(20)), 112.79 (C(50)), 116.03 (C(3)), 119.76
(C(a)), 121.67 (C(60)), 124.13 (C(5)), 125.67 (C(10)), 126.16
(C(6)), 129.16 (C(7)), 129.37 (C(8), C(10)), 134.97 (C(b)),
142.39 (C(4)), 148.27 (C(9)), 148.34 (C(30)), 149.05 (C(40)),
150.01 (C(2)). UV-Vis (c = 5 ꢂ 10ꢀ5 M, MeCN, 22 1C) lmax
:
354 nm (e = 32 600 Mꢀ1 cmꢀ1). MS (Irel (%)) m/z: 466 (30),
465 [M]+ (100), 290 (50), 289 (28), 288 (20), 276 (19), 263 (41),
217 (13), 216 (13), 109 (16). Anal. calcd for C27H31NO6: C,
69.66; H, 6.71; N, 3.01; found: C, 69.84; H, 6.79; N, 2.96%.
The second fraction contained 4 (0.18 g, 10%) as yellowish
solid, mp 64–66 1C. 1H NMR (DMSO-d6, 25 1C) d: 3.47
(m, 1H, CH(CH2)2), 3.48 (m, 2H, (CHaHb)2CH), 3.52 (s, 4H, 2
r-4-[c-2,t-4-Bis(3,4-dimethoxyphenyl)-t-3-(4-quinolyl)cyclobutyl]
quinoline (rctt-6). A solution of compound (E)-1 (9.4 mg) in
acetonitrile (0.5 mL) was evaporated in a Petri dish (d = 10
cm) with formation of a thin polycrystalline film of the
compound. This film was then irradiated with light from a
60 W incandescent lamp (35 h; distance from the light source
= 15 cm) to give rctt-6 as colourless solid (498%), mp 67–
70 1C. 1H NMR (DMSO-d6, 25 1C) d: 3.35 (s, 6H, 2 30-MeO),
3.52 (s, 6H, 2 40-MeO), 5.09 (dd, J = 10.5 Hz, J = 5.6 Hz, 2H,
2 H(b)), 5.14 (dd, J = 10.5 Hz, J = 5.6 Hz, 2H, 2 H(a)), 6.57
(d, J = 8.4 Hz, 2H, 2 H(50)), 6.70 (d, J = 1.9 Hz, 2H, 2 H(20)),
6.92 (dd, J = 8.4 Hz, J = 1.9 Hz, 2H, 2 H(60)), 7.58 (m, 2H, 2
H(6)), 7.68 (m, 2H, 2 H(7)), 7.77 (d, J = 4.6 Hz, 2H, 2 H(3)),
7.90 (d, J = 7.9 Hz, 2H, 2 H(8)), 8.41 (d, J = 8.2 Hz, 2H, 2
H(5)), 8.82 (d, J = 4.6 Hz, 2H, 2 H(2)). 13C NMR (DMSO-d6,
30 1C) d: 43.59 (2 C(a)), 44.62 (2 C(b)), 54.89 (2 30-MeO), 55.04
(2 40-MeO), 110.78 (2 C(50)), 112.48 (2 C(20)), 119.27 (2 C(3)),
OCH2), 3.53–3.58 (m, 8H,
4 OCH2), 3.59 (m, 2H,
(CHaHb)2CH), 3.67 (m, 4H, 2 CH2CH2OAr), 3.90 (m, 2H,
40-OCH2), 3.98 (m, 2H, 30-OCH2), 6.39 (dd, J = 8.2 Hz, J =
1.6 Hz, 1H, H(60)), 6.59 (d, J = 8.2 Hz, 1H, H(50)), 6.89 (d,
J = 1.6 Hz, 1H, H(20)), 7.16 (d, J = 4.3 Hz, 2H, 2 H(3)), 7.52
(m, 2H, 2 H(6)), 7.71 (m, 2H, 2 H(7)), 7.97 (d, J = 8.2 Hz, 2H,
2 H(8)), 8.03 (d, J = 8.6 Hz, 2H, 2 H(5)), 8.66 (d, J = 4.3 Hz,
2H,
2
H(2)). 13C NMR (DMSO-d6, 30 1C) d: 37.85
(CH(CH2)2), 46.45 (CH(CH2)2), 67.83 (40-CH2O), 68.05 (30-
CH2O), 68.62 (2 CH2CH2OAr), 69.66 and 69.71 (6 CH2O),
112.54 (C(20), C(50)), 119.99 (C(60)), 121.97 (2 C(3)), 123.66 (2
ꢁc
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119.67 (2 C(60)), 125.07 (2 C(5)), 125.73 (2 C(6)), 127.17 (2
C(10)), 128.75 (2 C(7)), 129.09 (2 C(8)), 131.88 (2 C(10)),
146.15 (2 C(4)), 146.97 (2 C(40)), 147.38 (2 C(9)), 147.47 (2
C(30)), 149.84 (2 C(2)). UV-Vis (c = 2.5 ꢃ 10ꢀ5 M, MeCN, 22
1C) lmax: 282 nm (e = 8600 Mꢀ1 cmꢀ1), 226 nm (e = 41 500
Mꢀ1 cmꢀ1). MS (Irel (%)) m/z: 582 [M]+ (0.8), 292 (12), 291
(69), 101 (18), 82 (22), 69 (15), 59 (44), 58 (100), 57 (17), 55
(27). Anal. calcd for C38H34N2O4 ꢂ 0.67H2O: C, 76.74; H, 5.99;
N, 4.71; found: C, 76.88; H, 5.56; N, 4.83%.
CH2O), 3.58 (m, 8H, 4 CH2O), 3.71 (m, 4H, 2 CH2O), 3.77 (m,
4H, 2 CH2O), 5.05 (dd, J = 10.0 Hz, J = 6.3 Hz, 2H, 2 H(b)),
5.14 (dd, J = 10.0 Hz, J = 6.3 Hz, 2H, 2 H(a)), 6.55 (d, J =
8.4 Hz, 2H, 2 H(50)), 6.73 (d, J = 1.9 Hz, 2H, 2 H(20)), 6.86
(dd, J = 8.4 Hz, J = 1.9 Hz, 2H, 2 H(60)), 7.57 (m, 2H, 2
H(6)), 7.66 (m, 2H, 2 H(7)), 7.74 (d, J = 4.5 Hz, 2H, 2 H(3)),
7.89 (d, J = 8.1 Hz, 2H, 2 H(8)), 8.37 (d, J = 8.6 Hz, 2H, 2
H(5)), 8.81 (d, J = 4.5 Hz, 2H, 2 H(2)). 13C NMR (DMSO-d6,
30 1C) d: 43.63 (2 C(a)), 44.58 (2 C(b)).
r-4-[c-2,t-4-Bis(2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10,13,
16-benzohexaoxacyclooctadecin-18-yl)-t-3-(1-ethyl-4-quinoliniumyl)
cyclobutyl]-1-ethylquinolinium diperchlorate (rctt-9). This was
obtained in a similar way to rctt-6, namely, by the irradiation
r-4-[c-2,t-4-Bis(3,4-dimethoxyphenyl)-t-3-(1-ethyl-4-quinoli-
niumyl)cyclobutyl]-1-ethylquinolinium diperchlorate (rctt-7). A
solution of compound (E)-2 (14.3 mg) in a mixture of acet-
onitrile (0.5 mL) and benzene (0.3 mL) was evaporated in a
Petri dish (d = 10 cm) with formation of a thin polycrystalline
film of the compound. This film was irradiated with light from
a 60 W incandescent lamp (80 h; distance from the light source
= 15 cm) to give a mixture of (E)-2 and rctt-7. Compound
rctt-7 was separated by crystallization from a MeCN–benzene
solution; orangey crystals (9.2 mg, yield 64%), mp 235–236 1C
(decomp.). 1H NMR (DMSO-d6, 25 1C) d: 1.48 (t, J = 7.1 Hz,
6H, 2 MeCH2), 3.46 (s, 6H, 2 30-MeO), 3.52 (s, 6H, 2 40-MeO),
5.02 (m, 4H, 2 CH2), 5.44 (dd, J = 10.3 Hz, J = 6.7 Hz, 2H, 2
H(b)), 5.50 (dd, J = 10.3 Hz, J = 6.7 Hz, 2H, 2 H(a)), 6.57
(d, J = 8.3 Hz, 2H, 2 H(50)), 6.79 (d, J = 1.7 Hz, 2H, 2 H(20)),
6.95 (dd, J = 8.3 Hz, J = 1.7 Hz, 2H, 2 H(60)), 8.01 (m, 2H, 2
H(6)), 8.19 (m, 2H, 2 H(7)), 8.42 (d, J = 6.2 Hz, 2H, 2 H(3)),
8.46 (d, J = 8.8 Hz, 2H, 2 H(8)), 8.85 (d, J = 8.4 Hz, 2H, 2
H(5)), 9.45 (d, J = 6.2 Hz, 2H, 2 H(2)). 13C NMR (DMSO-d6,
30 1C) d: 15.14 (2 MeCH2), 44.90 (2 C(a)), 45.32 (2 C(b)), 52.42
(2 CH2Me), 55.22 (4 MeO), 110.96 (2 C(50)), 112.58 (2 C(20)),
118.73 (2 C(8)), 120.18 (2 C(60)), 120.44 (2 C(3)), 127.94 (2
C(5)), 128.33 (2 C(10)), 128.95 (2 C(6)), 130.07 (2 C(10)), 134.85
(2 C(7)), 136.11 (2 C(9)), 147.54 (2 C(40)), 147.70 (2 C(30)),
147.75 (2 C(2)), 159.19 (2 C(4)). UV-Vis (c = 2.5 ꢃ 10ꢀ5 M,
MeCN, 22 1C) lmax: 310 nm (e = 7900 Mꢀ1 cmꢀ1), 229 nm (e
= 45 000 Mꢀ1 cmꢀ1). Anal. calcd for C42H44Cl2N2O12: C,
60.07; H, 5.28; N, 3.34; found: C, 60.12; H, 5.16; N, 3.27%.
1
for 20 h of a thin polycrystalline film of compound (E)-5. H
NMR (DMSO-d6, 30 1C) d: 1.50 (t, J = 7.2 Hz, 6H, 2
MeCH2), 3.48 (s, 8H, 4 CH2O), 3.52 (m, 16H, 8 CH2O),
3.59 (m, 8H, 4 CH2O), 3.74 (m, 4H, 2, 40-OCH2), 3.82 (m,
4H, 2 30-OCH2), 4.95–5.11 (m, 4H, 2 MeCH2), 5.41 (dd, J =
9.1 Hz, J = 7.0 Hz, 2H, 2 H(b)), 5.48 (dd, J = 9.1 Hz, J = 7.0
Hz, 2H, 2 H(a)), 6.58 (d, J = 8.4 Hz, 2H, 2 H(50)), 6.82 (d, J =
1.9 Hz, 2H, 2 H(20)), 6.93 (dd, J = 8.4 Hz, J = 1.9 Hz, 2H, 2
H(60)), 8.00 (m, 2H, 2 H(6)), 8.19 (m, 2H, 2 H(7)), 8.40 (d, J =
6.3 Hz, 2H, 2 H(3)), 8.47 (d, J = 9.0 Hz, 2H, 2 H(8)), 8.82 (d,
J = 8.3 Hz, 2H, 2 H(5)), 9.45 (d, J = 6.3 Hz, 2H, 2 H(2)).
X-Ray crystallography
Crystals of 1 and 3 were obtained by the slow evaporation of
CH2Cl2–hexane solutions in darkness. Crystals of 2,
6 ꢂ 2HClO4, and 7a were obtained by the slow saturation of
MeCN solutions with benzene by vapour diffusion methods
(in darkness for 2). Single crystals of all compounds were
coated with perfluorinated oil and mounted on a Bruker
SMART-CCD diffractometer (graphite monochromatized
Mo-Ka radiation, l = 0.71073 A, o scan mode).
A set of experimental reflections for 1 were measured using a
light yellow single crystal of dimensions 0.38 ꢃ 0.34 ꢃ 0.26
mm3. The structure was solved by direct methods and refined
with anisotropic thermal parameters. All hydrogen atoms were
located in the difference Fourier synthesis, but for further
refinement their geometrically calculated positions were
used. All hydrogen atoms were refined with an isotropic
approximation.
4-[(Z)-2-(2,3,5,6,8,9,11,12,14,15-Decahydro-1,4,7,10,13,16-
benzohexaoxacyclooctadecin-18-yl)-1-ethenyl]quinoline ((Z)-3)
and r-4-[c-2,t-4-bis(2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10,
13,16-benzohexaoxacyclooctadecin-18-yl)-t-3-(4-quinolyl)cyclo-
butyl]quinoline (rctt-8). A solution of compound (E)-3 (10 mg)
in acetonitrile (0.5 mL) was evaporated in a Petri dish (d = 10
cm) with formation of a thin polycrystalline film of the
compound. This film was irradiated with light from a 60 W
incandescent lamp (distance from the light source = 15 cm) to
give a mixture of (E)-3, (Z)-3, and rctt-8 in a 5.7 : 3.7 : 1 molar
Crystallographic data for 1. C19H17NO2, monoclinic, space
group P21/c (no. 14), a = 10.6020(3), b = 10.9717(3), c =
12.6859(4) A, b = 99.022(2)1, V = 1457.39(7) A3, Z = 4, d =
1.328 g cmꢀ3, 11 822 reflections measured, 3839 unique reflec-
tions [R(int) = 0.0319], R1 = 0.0434, wR2 = 0.1209 for 3181
reflections with I 4 2s(I), R1 = 0.0538, wR2 = 0.1262 for all
reflections.
1
ratio (from H NMR) after 10 h and in a 1.2 : 1 : 2.4 molar
ratio after 150 h of light exposure. (Z)-3: 1H NMR (DMSO-d6,
30 1C) d: 3.43 (m, 2H, 30-OCH2), 3.48–3.60 (m, 12H, 6 CH2O),
3.66 (m, 4H, 30-OCH2CH2, 40-OCH2CH2), 3.98 (m, 2H, 40-
OCH2), 6.49 (d, J = 1.9 Hz, 1H, H(20)), 6.64 (dd, J = 8.5 Hz,
J = 1.9 Hz, 1H, H(60)), 6.75 (d, J = 8.5 Hz, 1H, H(50)), 6.93
(s, 2H, H(a), H(b)), 7.35 (d, J = 4.4 Hz, 1H, H(3)), 7.58 (m,
1H, H(6)), 7.77 (m, 1H, H(7)), 8.03 (d, J = 8.4 Hz, 1H, H(5)),
8.06 (d, J = 8.2 Hz, 1H, H(8)), 8.83 (d, J = 4.4 Hz, 1H, H(2)).
A single crystal of 1 was subjected to irradiation with visible
light from a standard incandescent lamp (60 W, distance from
the light source was B15 cm) over a period of 6 h to form 1/6.
The single crystal of 1/6 was lighter in colour with respect to
the initial crystal. A set of experimental reflections for 1/6 was
measured with the same diffractometer. The structure was
solved by direct methods. The structure simultaneously con-
tains the initial compound and the cyclobutane product in a
0.66 : 0.34 ratio. The refinement of all non-hydrogen atoms
1
rctt-8: H NMR (DMSO-d6, 30 1C) d: 3.46–3.55 (m, 24H, 12
ꢁc
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was performed with an anisotropic approximation. The posi-
tions of the hydrogen atoms were calculated, and their refine-
ment was carried out with an isotropic approximation,
excluding the hydrogen atoms of the cyclobutane fragment
which were refined using a riding model.
atoms were refined using a riding model, or isotropically with
fixed values for the thermal parameters. All peaks of electron
density in the difference Fourier map are located in the vicinity
of the perchlorate anion, which point out somewhat rotational
disorder of the perchlorate anion over several positions.
However, a refinement of these peaks as new oxygen atoms
with partial occupation factors did not result in essential
improvement of structure accuracy and change of geometrical
parameters of the organic skeleton.
Crystallographic data for 1/6. C38H34N2O4, monoclinic,
space group P21/c (no. 14), a = 10.7020(7), b = 10.9624(7),
c = 12.5151(8) A, b = 98.443(3)1, V = 1452.35(16) A3, Z =
2, d = 1.332 g cmꢀ3, 11 419 reflections measured, 3798 unique
reflections [R(int) = 0.0324], R1 = 0.0648, wR2 = 0.1466 for
2903 reflections with I 4 2s(I), R1 = 0.0864, wR2 = 0.1558
for all reflections.
Crystallographic data for 7. C48H50Cl2N2O12, monoclinic,
space group P21/n (no. 14), a = 7.7053(9), b = 20.304(2), c =
14.3081(15) A, b = 99.737(5)1, V = 2206.2(4) A3, Z = 2, d =
1.382 g cmꢀ3, 11 384 reflections measured, 5204 unique reflec-
tions [R(int) = 0.1426], R1 = 0.1495, wR2 = 0.3078 for 2180
reflections with I 4 2s(I), R1 = 0.2886, wR2 = 0.3606 for all
reflections.
The single crystal of 1/6 transforms into colourless 6 after its
further irradiation under the same conditions for 24 h. A set of
experimental reflections for 6 was measured with the same
diffractometer. The structure was solved by direct method and
refined with an anisotropic approximation. All hydrogen
atoms were refined with an isotropic approximation.
Crystallographic data for 6. C38H34N2O4, monoclinic, space
group P21/c (no. 14), a = 10.9855(12), b = 10.8828(12),
c = 12.2120(13) A, b = 98.282(5)1, V = 1444.8(3) A3, Z =
2, d = 1.339 g cmꢀ3, 11 297 reflections measured, 3752 unique
reflections [R(int) = 0.0681], R1 = 0.0690, wR2 = 0.1333 for
2535 reflections with I 4 2s(I), R1 = 0.1123, wR2 = 0.1472
for all reflections.
Orange crystals of 7a were grown as a benzene solvate from
a MeCN–benzene mixture. A set of experimental reflections
for 7a was measured using a single crystal of dimensions
0.50 ꢃ 0.44 ꢃ 0.20 mm3. The structure was solved by direct
methods and refined with an anisotropic approximation for all
non-hydrogen atoms. All the hydrogen atoms were found in
the difference Fourier synthesis and refined with an isotropic
approximation.
Crystallographic data for 7a. C60H62Cl2N2O12, triclinic,
ꢀ
space group P1 (no. 2), a = 11.0230(4), b = 11.2484(4), c
A set of experimental reflections for 6 ꢂ 2HClO4 was mea-
sured using a very small single crystal of dimensions 0.16 ꢃ
0.08 ꢃ 0.04 mm3. The structure was solved by direct methods
and refined with an anisotropic approximation for all
non-hydrogen atoms. The hydrogen atoms were calculated
geometrically and refined with an isotropic approximation.
Crystallographic data for 6 ꢂ 2HClO4. C38H36Cl2N2O12, tri-
= 12.5132(5) A, a = 82.944(2), b = 76.649(2), g = 61.394(2)1,
V = 1325.19(9) A3, Z = 1, d = 1.346 g cmꢀ3, 9388 reflections
measured, 6577 unique reflections [R(int) = 0.0270], R1
=
0.0523, wR2 = 0.1156 for 4164 reflections with I 4 2s(I),
R1 = 0.0977, wR2 = 0.1283 for all reflections.
Yellowish crystals of 3 were grown as a water and dichlo-
romethane solvate. A set of experimental reflections for 3 was
measured using a plate-like crystal of dimensions 0.60 ꢃ 0.50
ꢃ 0.08 mm3. The structure was solved by direct methods and
refined with an anisotropic approximation for all non-hydro-
gen atoms. Almost all of the hydrogen atoms were located in
difference Fourier synthesis. However, for further refinement,
the hydrogen atoms were placed in geometrically calculated
positions and refined using a riding model. Two hydrogen
atoms of the water molecule present an exception. One of them
was objectively located and its positional and thermal para-
meters were fixed. The second hydrogen atom was not located
in the final difference Fourier synthesis, apparently, because of
its disorder over several positions. These positions may corre-
spond to hydrogen bonding of this hydrogen atom to the O(4)
atom or the Cl(1) atom related to the basis one through the b
translation. The corresponding distances Oꢂ ꢂ ꢂO and Oꢂ ꢂ ꢂCl
(2.909 and 3.343 A, respectively) fit well with this assumption.
Apparently, a combination of poor quality of the single crystal
and lacking of one H atom in the structure resulted in a
relatively high value of residual electron density.
ꢀ
clinic, space group P1 (no. 2), a = 11.4976(5), b = 12.2916(6),
c = 13.5348(6) A, a = 93.589(2), b = 110.545(2), g =
92.542(2)1, V = 1783.11(14) A3, Z = 2, d = 1.459 g cmꢀ3
,
12 884 reflections measured, 8721 unique reflections [R(int) =
0.0403], R1 = 0.0614, wR2 = 0.1350 for 5052 reflections with
I 4 2s(I), R1 = 0.1263, wR2 = 0.1547 for all reflections.
A set of experimental reflections for 2 was measured using
an orange single crystal of dimensions 0.48 ꢃ 0.40 ꢃ 0.36 mm3.
The structure was solved by direct methods. A benzene solvate
molecule situated at the symmetry center was found from the
Fourier synthesis. The structure was refined with an aniso-
tropic approximation for all non-hydrogen atoms, and an
isotropic approximation was applied to all hydrogen atoms.
Crystallographic data for 2. C24H25ClNO6, monoclinic,
space group P21/n (no. 14), a = 7.0340(5), b = 21.0718(14),
c = 14.6964(10) A, b = 94.3050(10)1, V = 2172.1(3) A3, Z =
4, d = 1.403 g cmꢀ3, 14 637 reflections measured, 5628 unique
reflections [R(int) = 0.0265], R1 = 0.0443, wR2 = 0.1220 for
4185 reflections with I 4 2s(I), R1 = 0.0662, wR2 = 0.1311
for all reflections.
After irradiation of the single crystal of 2 with visible light
from a standard incandescent lamp (60 W, distance from the
light source was B15 cm) for 30 h, a yellow single crystal 7
formed. A set of experimental reflections for 7 was measured
with the same diffractometer. The structure was solved by
direct methods. The structure was refined with an anisotropic
approximation for all non-hydrogen atoms. The hydrogen
Crystallographic data for 3. C28H35Cl2NO7, monoclinic,
space group P21/c (no. 14), a = 14.135(4), b = 7.983(2),
c = 25.020(7) A, b = 100.855(10)1, V = 2772.7(14) A3, Z =
4, d = 1.362 g cmꢀ3, 18 483 reflections measured, 7330 unique
reflections [R(int) = 0.2731], R1 = 0.1576, wR2 = 0.4168 for
2222 reflections with I 4 2s(I), R1 = 0.3390, wR2 = 0.4553
for all reflections.
ꢁc
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New J. Chem., 2007, 31, 980–994 | 993

View Article Online
All crystallographic data, data collection, solution and
refinement parameters for 1, 1/6, 6, 2, 3, 6 ꢂ 2HClO4, 7, and
7a are listed in Tables 1S–3S (ESIw). Selected bond lengths and
angles are given in Tables 4S–11S (ESI).
J. Saltiel, J. Phys. Chem. A, 2002, 106, 6213; (e) S. P. Gromov,
E. N. Ushakov, O. A. Fedorova, I. I. Baskin, A. V. Buevich,
E. N. Andryukhina, M. V. Alfimov, D. Johnels, U. G. Edlund,
J. K. Whitesell and M. A. Fox, J. Org. Chem., 2003, 68, 6115; (f) S.
P. Gromov, A. I. Vedernikov, N. A. Lobova, L. G. Kuz’mina, S.
N. Dmitrieva, O. V. Tikhonova and M. V. Alfimov, Patent
2278134 RF, Russia, 2006.
All the calculations were performed using the SHELXTL-
Plus software.9 CCDC reference numbers 630151 (1), 630152
3 (a) S. P. Gromov, O. A. Fedorova, E. N. Ushakov, A. V. Buevich,
I. I. Baskin, Yu. V. Pershina, B. Eliasson, U. Edlund and M. V.
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.
(1/6), 630153 (2), 630154 (3), 630155 (6), 630156 (6 2HClO4),
630157 (7), and 630158 (7a). For crystallographic data in CIF
or other electronic format see DOI: 10.1039/b615056j
Acknowledgements
Support from the Russian Foundation for Basic Research, the
INTAS (Grant 03-51-4696), the Russian Academy of Sciences,
the Royal Society (L. G. K. and A. V. C.), and the EPSRC for
a Senior Research Fellowship (J. A. K. H.) is gratefully
acknowledged.
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994 | New J. Chem., 2007, 31, 980–994