Synthesis, structure, and stereospecific cross-[2+2] photocycloaddition of pseudodimeric complexes based on ammonioalkyl derivatives of styryl dyes

Article abstract of DOI:10.1039/c5nj03500g

New 4-pyridine-derived styryl dyes having an ammonioalkyl N-substituent in the pyridine moiety and various substituents in the benzene moiety were synthesized. The formation of pseudodimeric complexes of ammonioalkyl styryl dye derivatives with 18-crown-6-containing styryl dyes of the 4-pyridine, 4-quinoline, and 2-benzothiazole series was studied by ¹H NMR in MeCN-d₃. It was found that the stability of supramolecular complexes is mainly determined by the monotopic interaction of the ammonioalkyl group with the crown ether moiety via hydrogen bonding. The components of pseudodimeric complexes undergo stereospecific cross-[2+2] photocycloaddition reaction to give unsymmetrical rctt isomers of cyclobutane derivatives owing to the syn-head-to-tail arrangement of components in the initial complex. The efficiency of photoreaction is affected by the N-substituent length, the nature of the substituent in the benzene ring of the ammonioalkyl component, and the nature of the heterocyclic residue of the crown-containing component. The structures of dyes, pseudodimeric complexes, and the cyclobutane derivative were studied by X-ray diffraction.

Full text of DOI:10.1039/c5nj03500g

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Synthesis, structure, and stereospecific
cross-[2+2] photocycloaddition of pseudodimeric
complexes based on ammonioalkyl derivatives of
styryl dyes†
Cite this:DOI: 10.1039/c5nj03500g
Sergey P. Gromov,*ab Artem I. Vedernikov,a Sergey K. Sazonov,a
Lyudmila G. Kuz’mina,c Natalia A. Lobova,a Yuri A. Strelenkod and
Judith A. K. Howarde
New 4-pyridine-derived styryl dyes having an ammonioalkyl N-substituent in the pyridine moiety and various
substituents in the benzene moiety were synthesized. The formation of pseudodimeric complexes of
ammonioalkyl styryl dye derivatives with 18-crown-6-containing styryl dyes of the 4-pyridine, 4-quinoline,
and 2-benzothiazole series was studied by 1H NMR in MeCN-d3. It was found that the stability of
supramolecular complexes is mainly determined by the monotopic interaction of the ammonioalkyl group
with the crown ether moiety via hydrogen bonding. The components of pseudodimeric complexes undergo
stereospecific cross-[2+2] photocycloaddition reaction to give unsymmetrical rctt isomers of cyclobutane
derivatives owing to the syn-head-to-tail arrangement of components in the initial complex. The efficiency
of photoreaction is affected by the N-substituent length, the nature of the substituent in the benzene ring of
the ammonioalkyl component, and the nature of the heterocyclic residue of the crown-containing
component. The structures of dyes, pseudodimeric complexes, and the cyclobutane derivative were studied
by X-ray diffraction.
Received (in Montpellier, France)
9th December 2015,
Accepted 21st June 2016
DOI: 10.1039/c5nj03500g
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useful properties of molecular assemblies not inherent in single
molecules.2
Introduction
Development of promising methods for the self-assembly of
It is well known3 that benzo-18-crown-6 ether and its derivatives
organic molecules via various non-covalent interactions such as efficiently bind primary ammonium ions via hydrogen bonding.
coordination, hydrogen bonding, Coulomb, ion–dipole, stacking, This feature underlies the supramolecular self-assembly of some
and hydrophobic interactions has been the subject of numerous photoactive compounds in which the benzo-18-crown-6 ether moiety
studies in supramolecular chemistry.1 The self-assembly of photo- can be a part of the conjugated system. The first studies along this
active compounds to supramolecular assemblies can considerably line were concerned with the properties of crown azobenzenes,
affect their photophysical and photochemical properties, as this which are capable of reversible E–Z photoisomerization.4
concentrates the sites responsible for these properties; interaction 18-Crown-6-substituted unsaturated compounds such as cinnamic
of these sites located at short distances often gives rise to new acid, stilbene, and styryl heterocycle derivatives are more promising.5
The CQC double bond contained in their chromophores can be
a Photochemistry Center, Russian Academy of Sciences, ul. Novatorov 7A-1,
Moscow 119421, Russian Federation. E-mail: spgromov@mail.ru
b Department of Chemistry, M. V. Lomonosov Moscow State University,
Leninskie Gory 1-3, Moscow 119991, Russian Federation
involved in photoinduced E–Z isomerization, [2+2] cycloaddition and
electrocyclization reactions. There are only a few examples of using
photoactive 18-crown-6-substituted unsaturated compounds in self-
+
assembly involving the RNH3 ions;6 they were mainly reported by
c N. S. Kurnakov Institute of General and Inorganic Chemistry,
Russian Academy of Sciences, Leninskiy prosp. 31, Moscow 119991,
Russian Federation
our research group.5c,d
Previously, we demonstrated7 that the E isomer of a 18-crown-6-
containing 2-benzothiazole styryl dye having a long ammoniohexyl
spacer in the heterocyclic residue, in a MeCN solution, sponta-
neously forms stable dimeric complexes (logKd = 6.1 [Mꢀ1]) with
the anti-head-to-tail arrangement of chromophores. Upon exposure
to light, this dye is converted almost completely to a cation-
capped Z isomer stabilized by intramolecular coordination of
d N. D. Zelinskiy Institute of Organic Chemistry, Russian Academy of Sciences,
Leninskiy prosp. 47, Moscow 119991, Russian Federation
e Chemistry Department, Durham University, South Road, Durham DH1 3LE, UK
† Electronic supplementary information (ESI) available: 1H and 13C NMR spectra,
UV-vis spectra, emission spectra, crystal packings, and X-ray crystallographic
data. CCDC 1430268–1430272. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/c5nj03500g
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Chart 1 Structure of 18-crown-6-containing styryl dye complexes based
on hydrogen bonding.
Scheme 1 Formation of cyclobutane rctt-3a from pseudodimeric
complex of two styryl dyes.
the ammonium group to the crown ether moiety (Chart 1a). The
E–Z isomerization is accompanied by a pronounced hypsochromic
shift of the long-wavelength absorption band (LWAB).
It is noteworthy that the examples of cross-PCA reactions that
usually accompany auto-PCA and/or afford mixtures of cyclobutane
isomers have been reported.5d,6b,10,11 In recent years, the regio- and
stereoselectivities of cross-PCA reactions have been increased by
using the protocol of encapsulation of the reactant molecules in
the cavities of zeolites and macroheterocyclic cavitands (cyclo-
dextrins, cucurbiturils, nanocages12) or by forming appropriate
crystal packings.13
The purpose of this study was to develop a method for the
synthesis of a series of 4-pyridine-derived styryl dyes 1b–i,
having N-ammonioalkyl substituents of different length in the
heterocyclic residue and various substituents in the benzene
ring. We studied how these factors influence the structure and
stability of the pseudodimeric complexes formed by these dyes
with 18-crown-6-containing 4-pyridine-derived styryl dye 2a and the
efficiency and stereoselectivity of cross-PCA in these complexes. For
comparison, the heterocyclic residue in the crown component was
also varied (4-quinoline- 2b and 2-benzothiazole-derived 2c dyes)
(Chart 2). The stability of the complexes was determined by 1H NMR
titration and the stereochemistry of the resulting cyclobutane
derivatives was elucidated by NMR spectroscopy. The structures
of some dyes, complexes, and cyclobutane derivatives were
determined by X-ray diffraction analysis.
The crown-containing 4-pyridine- and 4-quinoline-derived styryl
dyes, which have rather short ammonioalkyl N-substituents,
dimerize spontaneously according to the syn-head-to-tail pattern
both in solution and in the solid phase (Chart 1b).8 In MeCN, the
dimeric complexes are very stable, log Kd = 7.1–8.0 [Mꢀ1], due to
the homoditopic binding of the terminal ammonium groups
via hydrogen bonds with the 18-crown-6 ether fragments and
stacking interactions of the conjugated moieties. In the dimeric
complexes, the CQC double bonds are proximate and anti-
parallel, which promote an effective stereospecific auto-[2+2] photo-
cycloaddition (auto-PCA, i.e., two identical ethylene molecules take
part in the PCA) to give only the rctt isomer of cyclobutane
derivatives. Transition from the dimeric complexes to cyclobutane
derivatives is accompanied by a sharp change in the spectral
characteristics of compounds caused by the disruption of the
conjugated chain in the chromophore moieties.
We suggested that the components of the styryl dye dimers
can be held together even by monotopic interaction between
the ammonioalkyl group and the crown ether moiety. Preliminary
investigations showed9 that two different 4-pyridine-derived dyes,
one having an ammoniopropyl substituent (1a) and the other having
a crown ether moiety (2a), actually form a pseudodimeric complex.
Complex 1aꢁ2a is preorganized towards cross-[2+2] photocyclo-
addition (here ‘‘cross-PCA’’ means that two different ethylene com-
pounds react with each other10), i.e., the chromophore groups of the
Results and discussion
Synthesis of dyes
components are mainly located above each other owing to the The syntheses of 1a,9 1b,14 1g,15 2a,16 2b,17 and 2c7 were reported
stacking interaction of the dye conjugated systems. Irradiation of a in our previous publications. Dyes 1c,f,h,i were prepared by
solution containing an equimolar mixture of dyes 1a and 2a afforded fusing together the respective neutral 4-styrylpyridines 4a,c,f18
the only rctt isomer of the unsymmetrical cyclobutane derivative 3a with o-bromoalkylammonium bromides and subsequent anion
(Scheme 1). This opens up broad prospects for varying the structures exchange for perchlorate by treatment with concentrated HClO4
of both the ammonioalkyl styryl dye derivative and the crown styryl in ethanol (Scheme 2). In the synthesis of dyes 1d,e, quaterniza-
dye derivative and, hence, for fine tuning their spectral properties.
tion of 4d,e (R = SMe, NMe2) with 3-bromopropylammonium
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Scheme 2 Synthesis of dyes 1a–i.
induce a bathochromic shift of the peak by up to 134 nm with
respect to the unsubstituted dye (1b, lmax = 348 nm in MeCN),
whereas the LWAB of dyes with electron-withdrawing substituents
(NO2, Cl) undergoes only a slight hypsochromic shift (Dlmax up to
ꢀ3 nm) with respect to the LWAB of 1b. The position of the
LWAB maximum in the series of crown-containing dyes
depends on the electron-withdrawing properties of the hetero-
cyclic residue. The intramolecular charge transfer is facilitated
for compounds 2b and 2c with more electron-withdrawing
quinolinium and benzothiazolium residues (lmax = 434 and
431 nm, respectively) as compared with the less electron-
withdrawing pyridinium residue (for 2a lmax = 399 nm). Dyes
1a–e,g–i and 2c slightly fluoresce in MeCN solutions (see the
Experimental section and Fig. S22 in the ESI†). Dye 1f containing
the NO2 group is non-fluorescent.
Chart 2 Structure of dyes 1a–i and 2a–c.
bromide was carried out under milder conditions (boiling MeCN)
in order to avoid quaternization of sulfur or nitrogen of the
dimethylamino-group with excess alkylating agent. In the prepara-
Complex formation of dyes
tion of 1e, the ion exchange was accomplished by treatment of the Previously, we showed16 that crown-containing dye 2a with a
corresponding dye dibromide with a methanol solution of NaClO4 chromophoric group similar to that of dyes 1a,h,i shows also
in order to preclude the protonation of NMe2.
similar spectral characteristics. Indeed, in an MeCN solution,
1
The structures of the products were determined by H and dyes 1a and 2a have LWAB with lmax = 403 and 399 nm,
13C NMR spectroscopy and electronic spectroscopy methods respectively. Studies in acetonitrile solutions demonstrated
and confirmed by elemental analysis data (1H and 13C NMR that all styryl dyes 1a–i having ammonioalkyl substituents can
spectra and UV-vis and emission spectra of dyes 1a–i and 2c are form pseudodimeric complexes with 2a–c (Scheme 3). The
shown in Fig. S1–S22 in the ESI†). All dyes 1 and 2 have the E formation of complexes 1ꢁ2 is accompanied by a slight increase
configuration, judging by the spin–spin coupling constant in the electronic transition energy for dye 2, because the interaction
3JHCQCH = 15.7–16.5 Hz.
between the ammonium cation and the crown ether moiety
The chromophores of dyes 1a–i and 2a–c are donor–acceptor type involving hydrogen bonding weakens the electron-donating
conjugated systems.19 The long-wavelength band in the absorption properties of the benzocrown ether moiety. The absorption of
spectra of these compounds refers to intramolecular electronic dyes 1 is barely affected by the formation of complexes 1ꢁ2.15
transition accompanied by charge transfer from the benzene moiety
The formation of pseudodimeric complexes is clearly seen
to the quaternized heterocyclic residue. The nature of substituents from comparison of the 1H NMR spectra of free components
in the benzene ring of compounds 1a–i considerably affects the and equimolar mixtures. For example, in a solution in MeCN-d3,
position of the LWAB maximum. Electron-donating substituents the signals of ethylene and most aromatic protons of mixed dyes
(OMe, SMe, NMe2) in the para position to the ethylene bond 1b and 2a are shifted upfield to DdH = ꢀ0.09 ppm relative to free
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Scheme 3 Complex formation between dyes 1a–i and 2a–c.
1b and 2a (Fig. 1; the proton numbering is shown in Chart 2).
Previously, we showed20 that complexation of dye 2a with the EtNH3
+
Fig. 2 1H NMR spectra (aliphatic proton region) of (a) dye 1b, (b) a 1 : 1
mixture of dyes 1b and 2a, and (c) dye 2a (Cdye = 1 ꢂ 10ꢀ3 M), MeCN-d3,
30 1C.
ions results, conversely, in a slight downfield shift of all proton
signals of 2a. Indeed, the signals for crown ether CH2O groups of 2a
shift downfield by up to DdH = 0.07 ppm upon mixing with 1b, which
confirms the hydrogen bonding of the ammonium group with the
+
crown ether. Meanwhile, the (CH2)3NH3 signals of dye 1b and
The stability constants of complexes 1ꢁ2 were determined
using HYPNMR21 software by analyzing the variation of proton
signal positions of dye 2 as functions of the concentration of
dye 1 added. The results are summarized in Table 1.
ethyl group signals of dye 2a shift upfield upon mixing by up to
DdH = ꢀ0.15 ppm (Fig. 2). The observed upfield shift for mixed
dyes 1b and 2a can be attributed only to the preferred arrangement
of the planar conjugated moieties of the dyes approximately one
above the other in complex 1bꢁ2a (for example, see Scheme 1) and,
hence, to substantial anisotropic effects in this complex. Similar
changes were observed for mixtures of other dyes 1 with dyes 2
(Fig. S23–S31 in the ESI†).
Quantitative determination of the stability of complexes of
ammonioalkyl dye derivatives 1b–i with crown dyes 2a–c was
performed by 1H NMR titration in a MeCN-d3 solution. The
complex formation is described by the following equilibrium:
As compared with the dimeric complexes of styryl dyes shown in
Chart 1b, the stability of pseudodimeric complexes decreases by
more than 3 orders of magnitude. Evidently, the cause is the
presence of ditopic NH3+ꢁꢁꢁ18-crown-6 interactions in the dimeric
complexes and only monotopic interactions in complexes 1ꢁ2. The
stability of pseudodimeric complexes varies over a rather narrow
range of values, log K = 3.1–3.7, which implies the highest con-
tribution to the stability of hydrogen bonding between the primary
ammonium group and the 18-crown-6 ether moiety. The most
stable complexes are formed by dyes 1a,e,g,h and 2b,c, which
contain more extended conjugated systems, that additionally
stabilize pseudodimeric complexes owing to stacking interactions
(secondary interaction of the pz-orbitals of the conjugated systems)
between spatially proximate components. Noteworthy in this
respect is that the least stable complex is formed by dye 1b
devoid of substituents in the benzene ring. The nature of
substituents (donor or acceptor) in the benzene ring of dyes 1
has little influence on the stability of complexes. The length of the
ammonioalkyl chain in dyes 1 also affects only slightly the stability
of complexes with dye 2a. Only a minor stability decrease can be
noted on going from 1a,h (ammoniopropyl and ammonioethyl) to
K
ꢀ!
1bꢀi þ 2aꢀc
1bꢀi ꢁ 2aꢀc
ꢀ
where K/Mꢀ1 is the stability constant of the pseudodimeric
complex.
Table 1 Effective stability constants of pseudodimeric complexes of dyes
1a–i with dyes 2a–ca
Complex
log K
Complex
log K
1aꢁ2b
1aꢁ2c
1aꢁ2a
1hꢁ2a
1eꢁ2a
1gꢁ2a
3.7
3.6
3.5b
3.5
3.4
3.4
1dꢁ2a
1fꢁ2a
1iꢁ2a
1cꢁ2a
1bꢁ2a
3.3
3.3
3.3
3.3
3.1
Fig. 1 1H NMR spectra (aromatic proton region) of (a) dye 1b, (b) a 1 : 1 mixture
of dyes 1b and 2a, and (c) dye 2a (Cdye = 1 ꢂ 10ꢀ3 M), MeCN-d3, 30 1C.
a 1H NMR titration, MeCN-d3, 30 ꢃ 1 1C. The errors for determination of
b
constants K are ꢃ30%. From ref. 7.
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1i (ammoniopentyl). Apparently, the long N-substituent in dye
1i weakens the stacking interactions in the complex with 2a due
to the remote spatial positions of the conjugated moieties of
the components.
Pseudodimeric complexes were obtained in the solid state by
slow crystallization of equimolar mixtures of the components
(see the Experimental section and Fig. S32–S39 in the ESI†). The
composition of most complexes is 1 : 1 (1H NMR monitoring and
elemental analysis data). The only exception is the complex
formed by dyes 1a and 2a, which proved to have 1.5 : 1 composition
(a reproducible result from several crystallizations). Apparently, the
fine-grained crystalline phase formed consists of a co-crystallizate
of complex 1aꢁ2a with free 1a.
X-ray diffraction study of dyes and complexes
The X-ray diffraction investigations of dyes 1a, 2a, and 2b have
been previously reported.8,16,22 It was ascertained that in the
crystals, the organic cations of these dyes form centrosymmetric
syn-head-to-tail dimeric pairs with extensive stacking interactions of
conjugated moieties. In the dimeric pairs, the CQC bonds occupy
proximate positions at B3.6–4.0 Å distances and are strictly
antiparallel. These conditions proved to be favourable for the
solid-phase auto-PCA, which proceeded with retention of single
crystals for 1a and 2a.16,22 Note, however, that in solution, these
compounds do not undergo the auto-PCA reaction.
Fig. 3 Structures 2cꢁC4H8O2ꢁ3H2O (top) and 1fꢁ0.25H2O (bottom). Thermal
ellipsoids are drawn at the 50% probability level. Hydrogen bonds are drawn
with dash lines. The additional letters ‘‘A’’ indicate that atoms belong to
symmetrically related sites.
We succeeded in growing single crystals of free dyes 1f and
2c, which were studied by X-ray diffraction; the structures are
shown in Fig. 3.
The chromophore of dye 2c is generally planar: the dihedral
angle between the benzothiazole residue and benzene ring
The independent part of the unit cell of 2c contains a planes is only 3.81. The ethylene group is relatively localized:
dioxane molecule of solvation and three water molecules. This the C(8)QC(9) bond length is 1.335(4) Å, whereas the lengths of
structure was determined with high accuracy, which allowed the neighbouring formally single bonds, C(7)–C(8) and C(9)–C(10),
the location of hydrogen atoms of water molecules in electron are increased to 1.440(4) and 1.458(4) Å. This is a typical bond
density maps. Two water molecules, H2O(1W) and H2O(2W), length distribution in styryl dyes,8,16–18,22 which does not prevent
are arranged above and below the mean plane of the macro- efficient conjugation throughout the whole chromophore. Note
cyclic moiety and form weak directional or bifurcate hydrogen that for the PCA reaction to occur, the ethylene bond in the
bonds with their oxygen atoms.‡ The H2O(3W) water molecule chromophore should be substantially localized.
connects, via hydrogen bonding,§ the H2O(1WA) and H2O(2W)
The molecular cations of dye 2c form centrosymmetric
molecules of two neighbouring subunits separated by a transla- dimeric pairs arranged in the syn-head-to-tail fashion, which
tion. Thus, a continuous chain of hydrogen-bonded atoms is are stacked (Fig. S40 in the ESI†). The CQC double bonds in the
present in the 2cꢁC4H8O2ꢁ3H2O crystal (see Fig. S40 in the ESI†). dimeric pair approach each other to a distance of 3.77 Å and are
Note that a solvation water molecule hydrogen-bonded to strictly antiparallel. This packing of styryl dyes is favourable for the
the crown ether moiety was also found in the crystal structure solid-phase auto-PCA, which has been confirmed previously16,18 for
of dye 2a.16 This coordination of the water molecule hampers dye 2a and related 2-benzothiazole styryl dye devoid of the crown
complex formation between the crown ether moiety and the ether moiety. However, prolonged visible light irradiation of the
ammonium groups of dyes 1; therefore, a considerable content crystals of 2cꢁC4H8O2ꢁ3H2O did not bring about a change in their
of water in acetonitrile solution can markedly decrease the structure. Apparently, the numerous hydrogen bonds, mentioned
stability constants of complexes 1ꢁ2.
above, make the crystal structure more rigid, which prevents the
ethylene bond atoms from moving toward each other as needed to
form a cyclobutane derivative.
In the crystal of 1fꢁ0.25H2O, both independent perchlorate
anions are disordered over two sites each via rotation about one
of the Cl–O bonds.
The chromophore of dye 1f is planar, which is confirmed by
the dihedral angle of 5.41 between the pyridine and benzene
ring planes. The ethylene bond is also rather localized: the
‡ In 2cꢁC4H8O2ꢁ3H2O, the hydrogen bond parameters are as follows: the
O(1W)Hꢁ ꢁ ꢁO(4), O(1W)Hꢁ ꢁ ꢁO(5), O(1W)Hꢁ ꢁ ꢁO(6), O(2W)Hꢁ ꢁ ꢁO(3), O(2W)Hꢁ ꢁ ꢁO(1),
and O(2W)Hꢁ ꢁ ꢁO(6) distances are 1.99(5), 2.44(7), 2.42(7), 1.99(4), 2.46(5), and
2.49(5) Å, respectively, and the angles at the H atoms are 152(4)1, 121(5)1, 168(5)1,
167(3)1, 145(5)1, and 151(6)1, respectively.
§ Hydrogen bond parameters are as follows: the O(3W)Hꢁ ꢁ ꢁO(1WA) and
O(3W)Hꢁ ꢁ ꢁO(2W) distances are 2.00(4) and 1.77(5) Å and the angles are 174(4)1
and 165(4)1.
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distances in the C(6)–C(9)QC(10)–C(11) moiety are 1.469(7),
1.324(7), and 1.465(7) Å, respectively. The ammoniopropyl
N-substituent has a trans, gauche conformation, although the
steric and Coulomb interactions require that this substituent
be in all-transoid conformation. Evidently, the Coulomb inter-
actions are partially counterbalanced by the weak hydrogen
bonding of the ammonium group with the anions.¶
The cations of dye 1f are arranged in loose slanted stacks
formed in the head-to-head fashion in which the conjugated
moieties are projected only by the nitrostyrene groups (Fig. S41
in the ESI†). The ethylene-bond carbon atoms of adjacent
cations in the stack are separated by distances of 4.20–4.86 Å
and, moreover, these bonds are non-parallel. The solid-phase
auto-PCA reaction cannot occur in this packing for geometrical
reasons, which accounts for the stability of the crystals of 1fꢁ
0.25H2O on prolonged irradiation.
We also prepared single crystals for two pseudodimeric
complexes, 1dꢁ2a and 1fꢁ2a.
The structure of the major components of complex 1fꢁ2aꢁ
0.5C6H6ꢁ2H2O is shown in Fig. 4. The independent part of the
unit cell was found to contain the organic cations of dyes 1f and
2a, four disordered perchlorate anions, and molecules of
solvation.
The conjugated moiety of dye 2a is disordered over two sites,
i.e., the crystal contains simultaneously the s-anti and s-syn
conformers of 2a (see Chart 3). This is due to so-called ‘‘pedal’’
isomerization of the ethylene bond in the crystals of stilbene-
type compounds,23 which is typical of styryl dyes.18
Fig. 4 Stack of cations forming pseudodimeric complexes in structure
1fꢁ2aꢁ0.5C6H6ꢁ2H2O. Thermal ellipsoids are drawn at the 40% probability
level. Most of the hydrogen atoms are omitted for clarity. Hydrogen bonds
are drawn with dash lines. The additional letters ‘‘A’’ and ‘‘B’’ indicate that
atoms belong to symmetrically related sites.
Complex 1fꢁ2a is a pseudodimeric pair of dye cations
arranged in the head-to-tail fashion. The ammonium group of
1f is coordinated to the crown ether moiety of 2a via the
formation of directional hydrogen bonds with its oxygen
atoms.8 The conjugated moiety of dye 2a is nearly planar: the
dihedral angles between the pyridine and benzene rings in the
predominant and minor s-conformers are 10.51 and 7.01,
respectively. The chromophore of ammonium dye 1f is some-
what incurved (without twisting), the pyridine residue/benzene
ring dihedral angle being 13.31. The conjugated moieties of
both dyes are projected onto each other and lie in roughly
parallel planes: the dihedral angle between them is only 6.61.
However, the conjugated moieties of dyes 1f and 2a in the
crystalline pseudodimeric complex were found to be rather far
from each other. For example, the C(60)ꢁ ꢁ ꢁC(1000) and C(70)ꢁ ꢁ ꢁ (900)
Chart 3 Conformers of dye 2a.
distances are 6.85 and 6.81 Å, respectively. Such a structure of neighbouring complexes, which are arranged in the head-to-
the pseudodimer is a consequence of the given crystal packing. head fashion with a considerable shift, so that only the nitro
The complexes form very loose stacks extended along the group of 1f and the benzene ring of 2a are projected onto each
ab direction in which the conjugated moieties of dyes 1f and 2a other. The distances between the ethylene moieties of these
alternate in pairs (see Fig. 4). Therefore, proximate positions cations are too long for cross-PCA: the C(60)ꢁ ꢁ ꢁC(900A) and
are found for the molecular cations of dyes 1f and 2a from C(70)ꢁ ꢁ ꢁC(10B) distances are 6.08 and 5.69 Å. In a stack, two
neighbouring cations of dye 1f are arranged in the syn-head-to-
¶ For the N(1)Hꢁ ꢁ ꢁO(12), N(1)Hꢁ ꢁ ꢁO(15), and N(1)Hꢁ ꢁ ꢁO(21) bonds in structure 1fꢁ tail fashion in parallel planes with an interplanar spacing of
0.25H2O, the distances are 2.04, 2.10, and 2.01 Å, while the angles at hydrogen
B3.6 Å. However, despite the considerable degree of over-
lapping of their conjugated systems, auto-PCA is impossible
atoms are 1641, 1231, and 1621. Also, the ammonium group is hydrogen-bonded
to the NO2 group of the neighbouring molecular cation: the N(1)Hꢁ ꢁ ꢁO(2A)
because of a large distance between the ethylene moieties: the
contact has a length of 2.20 Å and an angle of 1691.
C(900)ꢁ ꢁ ꢁC(10B) and C(1000)ꢁ ꢁ ꢁC(900A) distances are 5.26 Å. The
8 In structure 1fꢁ2aꢁ0.5C6H6ꢁ2H2O, the length of the N(100)Hꢁ ꢁ ꢁO(2,4,6) contacts
varies in the range of 1.95–2.10 Å and the angles at H atoms are 148–1641.
two cations of dye 2a adjoining each other in the stacks are also
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arranged in the head-to-tail fashion in parallel planes at B3.4 Å
distance, thus enabling stacking interactions of the conjugated
moieties. The cations of 2a are substantially shifted relative to
each other; therefore their ethylene bonds are not projected.
The distances between the carbon atoms of the disordered
ethylene moieties, C(6)ꢁꢁꢁC(7B) and C(7)ꢁꢁꢁC(6B), C(60)ꢁꢁꢁC(70B) and
C(70)ꢁ ꢁ ꢁC(60B), are 4.20 and 4.02 Å, respectively. This geometry
is unsuitable for auto-PCA of the crown-containing dye. Indeed,
visible light irradiation of the crystal 1fꢁ2aꢁ0.5C6H6ꢁ2H2O for
eight days did not induce any structural change.
Complex 1dꢁ2a forms very unstable loose crystals, which
weakly reflect X-rays and, therefore, the accuracy of X-ray
experiments proved to be relatively low for all studied samples.
We still decided to include these results into the article only to
demonstrate a different structure of a pseudodimeric complex
as compared with the above-described structure of 1fꢁ2a. Therefore,
we do not dwell on fine structure details for the components of
complex 1dꢁ2a but consider only their general geometry and
relative positions in the crystal.
The independent part of the unit cell of 1dꢁ2aꢁ0.7C6H6ꢁ0.7H2O
was found to contain two cations of dye 1d, two cations of dye 2a,
ꢀ
six ClO4 anions, three benzene molecules of solvation, and six
Fig. 5 Stack of cations forming pseudodimeric complexes in structure 1dꢁ
2aꢁ0.7C6H6ꢁ0.7H2O. Most of the hydrogen atoms are omitted for clarity.
Hydrogen bonds are drawn with dash lines. The additional letters ‘‘A’’
indicate that atoms belong to symmetrically related sites.
water molecules. The vast majority of the unit cell components are
strongly disordered, which partly explains the weak reflecting
ability of the crystal (see the Experimental section).
The molecular cations of dyes 1d and 2a form two independent
head-to-tail pseudodimeric complexes, which are stacked along the are located above each other according to the syn-head-to-tail
b axis of the crystal (Fig. 5). In the stacks, the planar conjugated pattern; therefore, the CQC double bonds are antiparallel and
moieties of the neighbouring cations are projected onto each other spaced apart by only B3.5–4.0 Å. According to Schmidt’s
and are roughly parallel with interplanar spacings of B3.4–3.7 Å, criterion,24 these conditions are favourable for solid-phase
i.e., the stacking interactions are substantial throughout the whole PCA. Meanwhile, in solutions, dyes 1a, 2a, and 2b underwent
stack. Unlike 1fꢁ2aꢁ0.5C6H6ꢁ2H2O, the cations that form complexes only geometric E–Z isomerization. In this case, the PCA is
1dꢁ2a are spatially proximate, although in both structures, the evidently hampered by the short lifetime of the excited states
ammoniopropyl N-substituents assume the all-transoid conforma- of the molecules, potential participants of the photoreaction,
tion. This emphasizes the structure flexibility of the pseudodimeric and long distances between them.
complexes. In 1dꢁ2aꢁ0.7C6H6ꢁ0.7H2O, the dihedral angles between
Visible light irradiation of solutions of free dyes 1a–i in MeCN
the mean planes of the conjugated moieties of pseudodimer results, in most cases, in relatively fast decrease in LWAB intensity
components are only B8–91. Due to the pedal disorder, their (down to 33–81% of the initial value) and a slight hypsochromic shift
ethylene groups can be roughly antiparallel or crossed and spaced of the absorption maximum, which is caused by E–Z isomerization
apart by B3.7–4.4 Å. The ethylene groups in cations of the same of the dyes (see Fig. S42–S49 in the ESI†). Previously,16 we observed a
type adjacent in the stack are spaced apart by B4.2–4.6 Å, which similar behaviour of dye 2a (see also Fig. S50, ESI†). An exception is
implies that there are no conditions for auto-PCA to occur. Thus, dye 1e containing the NMe2 group for which the LWAB intensity
1dꢁ2aꢁ0.7C6H6ꢁ0.7H2O clearly demonstrates the typical structure of decreases only slightly (to 96% of the initial value, Fig. S46, ESI†).
pseudodimeric complexes, which is also retained in solutions Apparently, the high electron-donating properties of the substituent
(according to 1H NMR data). This structure of the complexes nitrogen as compared with other heteroatoms lead to a much higher
provides the conditions for selective cross-PCA in solutions in degree of conjugation in the chromophore of 1e and, hence, to fast
which the component mobility markedly increases but molecules thermal Z–E isomerization.25 Dyes having chromophores similar to
of the same type do not form stable dimers.
that of 1e are also prone to non-radiative transition from the excited
state to the ground state via the twisted internal charge transfer
(TICT) excited state.26
Cross-[2+2] photocycloaddition of pseudodimeric complexes
Previously, we found16,17,22 that dyes 1a, 2a, and 2b in the solid
As an example, Fig. 6 shows the changes for a solution of dye
phase (crystals and polycrystalline films) undergo auto-PCA upon 1f. It is noteworthy that after the photostationary equilibrium
exposure to visible light to give centrosymmetric rctt isomers of has been attained in solution of any dye 1, further long-term
cyclobutane derivatives. This is possible owing to the topochemical irradiation does not induce any spectral changes.
control of the crystal lattice which favours the formation of dimeric
It was ascertained above that in solutions of MeCN, dyes 1
pairs of the dyes. In these dimers, the planar molecular dye cations and 2 form relatively stable pseudodimeric complexes in which
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Scheme 4 Formation of cyclobutane derivatives rctt-3.
Fig. 6 Irradiation of the solution of dye 1f for 0, 1, 3, 6, 10, 20, 30, 50, 80,
and 110 min (MeCN, C1f = 1.11 ꢂ 10ꢀ4 M, 0.1 cm quartz cell, unfiltered light
from a 60 W incandescent lamp, distance to the light source B15 cm). The
green dash curve is a photostationary mixture consisting of E and Z
isomers of 1f.
the conjugated moieties are spatially proximate owing to stacking
interactions (see Schemes 1 and 3). Thus, complexes 1ꢁ2 are
preorganized towards cross-PCA.
Visible light irradiation of solutions of equimolar mixtures
of dyes 1a–d,f,h with 2a and 1a with 2b resulted in a more
pronounced decrease in the long-wavelength absorption intensity
as compared with free components (Fig. S51–S55 in the ESI†). The
disappearance of absorption in the region of 4330 nm is caused by
the disruption of the conjugated system in the chromophores of
both pseudodimer components as a result of cross-PCA to give
1,2,3,4-tetrasubstituted cyclobutanes 3 (Scheme 4).
Fig. 7 Irradiation of solution of an equimolar mixture of dyes 1d and 2a
for 0, 1, 6, 20, 40, and 80 min and 2, 4, 8, and 16 h (MeCN, C1d = C2a = 5 ꢂ
10ꢀ4 M, 0.1 cm quartz cell, unfiltered light from a 60 W incandescent lamp,
distance to the light source B15 cm). The blue dash curve is the spectrum
of cyclobutane rctt-3d (MeCN, C3d = 5 ꢂ 10ꢀ4 M, 0.1 cm quartz cell).
This is exemplified in Fig. 7, which shows data on the spatial proximity of the CQC bonds in the pseudodimeric complex
irradiation of a solution containing an equimolar mixture of 1iꢁ2a, which is necessary for PCA. The shortest ammonioethyl spacer
dyes 1d and 2a. In the beginning of irradiation, the absorption apparently makes the pseudodimeric complex molecule too rigid
intensity at about 400 nm rapidly decreases (in B30 min), as compared with longer and more flexible N-ammonioalkyl
which is caused by the fast E–Z isomerization of both dyes. This substituents, which prevents the ethylene bonds in the complex
is followed by slower changes caused by cross-PCA. However, in based on 1h from approaching each other. A similar dependence
none of the cases, the absorption at about 400 nm disappears of the auto-PCA rate on the length of the N-substituent has been
completely even after 4100 h due to insufficiently high stability demonstrated8 by styryl dyes shown in Chart 1b.
constants of complexes 1ꢁ2 (see Table 1). As the dyes are
In the complexes formed by 1e,g with 2a, the spectral
consumed in cross-PCA, their concentration decreases and, hence, variations depending on the irradiation time are similar to
the content of the complexed dyes decreases. For comparison, those for 1iꢁ2a (Fig. S56 and S57 in the ESI†). That is, in the case
Fig. 7 also shows the absorption spectrum of single rctt-3d, which of ammoniopropyl dyes with two electron-withdrawing substituents
was isolated by crystallization (see below). This compound barely (Cl) or with the most electron-donating substituent (NMe2) in the
absorbs light at l 4 330 nm.
benzene ring, cross-PCA is either very slow and gives cyclobutane
The variation of the absorbance at 397 nm for solutions of derivatives in only trace amounts or does not proceed at all. The
equimolar mixtures of dye 2a with dyes 1a,h,i depending on the absence of PCA with dye 1e is apparently due to the efficient
irradiation time is shown in Fig. 8. It can be clearly seen that formation of the TICT excited state.
cross-PCA occurs most rapidly in complex 1aꢁ2a and is some-
Varying the heterocyclic residue in the crown-containing dye
what slower in 1hꢁ2a. In the case of complex 1iꢁ2a, the decrease has a considerable effect on the cross-PCA rate. Indeed, in
in the long-wavelength absorption reaches B65% of the initial complex 1aꢁ2b, photocycloaddition occurs much more slowly
value, i.e., E–Z isomerization is the major process. Thus, the than in complex 1aꢁ2a: in 290 h, the degree of conversion to the
study of the effect of N-substituent length on the efficiency of corresponding cyclobutane derivative is 51% (1H NMR monitoring;
cross-PCA demonstrated that the ammoniopropyl spacer has the Fig. S58 in the ESI†). Complex 1aꢁ2c is not converted to the
length of choice, whereas in the system with the ammoniopentyl cyclobutane derivative at all. Apparently, the large quinoline or
N-substituent, this photoreaction barely occurs. Apparently, the benzothiazole residues sterically prevent the ethylene moieties in
too long spacer is unfavourable as regards the requirement of complexes 1aꢁ2b,c from approaching each other, which is necessary
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Fig. 8 Dependence of the absorbance at 397 nm on the time of irradiation
of solutions of equimolar mixtures of dye 2a with dyes 1a, 1h, and 1i (MeCN,
C1a,h,i = C2a = 5 ꢂ 10ꢀ4 M, 0.1 cm quartz cell).
for the formation of cyclobutanes 3. Moreover, an additional
obstacle to the proximity of ethylene bonds can be caused by
the closely located N-ethyl substituent in the benzothiazole
residue.
Scheme 5 Synthesis of cyclobutane derivatives rctt-3b–d.
1H NMR examination of the photolysis products of dye
mixtures 1a–i/2a–c confirmed the conclusions drawn from
UV-vis spectroscopy data concerning the reactivity of pseudo-
dimeric complexes. Thus, cross-PCA reaction efficiently occurs
in the complexes formed by 4-pyridine-derived dyes having a
relatively short ammoniopropyl N-substituent and electron-
donating substituents OMe and SMe (or without substituents)
in the benzene ring.
rctt-3b–d are shown in Fig. S61–S67 in the ESI†). The 13C NMR
spectra of rctt-3b–d exhibit four signals in the characteristic
43–47 ppm range, which correspond to the unsymmetrically
substituted cyclobutane ring. The positions of these signals are
similar to the positions of cyclobutane carbon signals of rctt-3a
prepared previously (cf. Fig. S60 in the ESI†). In the case of
cyclobutane derivatives formed from complexes 1fꢁ2a, 1hꢁ2a, and
1aꢁ2b, the photolysis products containing these cyclobutanes
were substantially contaminated by mixtures of geometric isomers
of the initial dyes; therefore, we were unable to isolate these
cyclobutanes in a pure state.
In all of the above cases where the cross-PCA reaction is
relatively efficient, only one stereoisomer of cyclobutane 3 is
formed. Apart from the signals of minor E and Z isomers of the
initial compounds 1a–d,f,h and 2a,b, the 1H NMR spectra of
photolysis products exhibit a new set of signals at about 5 ppm,
which is characteristic of cyclobutane derivatives of a similar
structure.8,14,16,18,22 While comparing these signals with analogous X-ray diffraction study of cyclobutane derivatives
signals of the previously studied isomer rctt-3a,9 we concluded that
A colourless crystal of cyclobutane derivative rctt-3c was studied
by X-ray diffraction; Fig. 10 shows the structure of its major
component (see the packing in Fig. S68 in the ESI†).
all of the obtained cyclobutanes have a rctt stereochemistry and,
hence, they are formed from pseudodimeric complexes 1ꢁ2 in
which the dyes were arranged in the syn-head-to-tail fashion (see
The cyclobutane derivative 3c identified in the crystal is the
Schemes 1 and 5). The signals of all cyclobutane protons of rctt-3a
rctt isomer. It should have been formed from the syn-head-to-
overlap little with each other; therefore, they all are doublets of
tail pseudodimeric complex 1cꢁ2a. This is direct evidence
doublets (ABCD type spin system). For cyclobutanes rctt-3b–d, the
a-H and d-H proton signals considerably overlap; therefore, the
supporting our conclusion based on 1H NMR spectroscopy data
about the prevailing structure of pseudodimeric complexes and
multiplicity pattern for all signals of the cyclobutane moiety is more
the stereochemistry of cyclobutanes 3 they form.
complex (i.e., it is a high-order 1H NMR spectrum), which compli-
cates the determination of spin–spin coupling constants (Fig. 9,
atom numbering is shown in Scheme 5).
+
In rctt-3cꢁ2C6H6ꢁ0.75MeCNꢁ0.25H2O, the NH3 group of the
N-ammoniopropylpyridinium moiety is coordinated intra-
molecularly by the benzocrown ether moiety that occupies the
cis-position to it via the formation of three hydrogen bonds.**
The pyridine and phenyl substituents, which are cis-arranged in
the cyclobutane ring, are not parallel due to the attachment to
sp3-hybridized carbon atoms: the dihedral angles between the
From photolysis products of complexes 1b–dꢁ2a in which
cross-PCA is most effective and can proceed to a 495% con-
version to cyclobutane derivatives, compounds rctt-3b–d were
isolated in 92–95% yields by fractional crystallization. Their
1
structures were characterized by H and 13C NMR spectroscopy
and UV-vis spectrometry and confirmed by elemental analysis
** In structure rctt-3cꢁ2C6H6ꢁ0.75MeCNꢁ0.25H2O, the N(2)Hꢁ ꢁ ꢁO(2,4,5) distances
data (1H and 13C NMR spectra and UV-vis spectra of compounds are 2.00–2.21 Å and the angles at the H atoms are 130–1581.
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The cyclobutane ring has a non-planar conformation: the
torsion angles in the C(6)–C(7)–C(34)–C(35) ring are ꢀ10.71,
10.61, ꢀ10.81, and 10.61. The distances in this ring are
1.563(11), 1.593(11), 1.565(11), and 1.572(12) Å. The endocyclic
angles in the cyclobutane ring are 88.8(6)–90.2(6)1. These values
are typical of 1,2,3,4-tetrasubstituted cyclobutanes that we
studied earlier.8,14,16,18,22
Conclusions
We developed a synthesis of a series of new 4-pyridine-derived
styryl dyes with N-ammonioalkyl spacers of various lengths and
various substituents in the benzene ring. In MeCN solutions,
these dyes form stable pseudodimeric complexes with 18-crown-
6-containing styryl dyes mainly due to monotopic hydrogen
bonding of the terminal ammonium group of one dye with the
macrocycle O atoms of the other dye. Additional contribution to
the stability of complexes is made by the stacking interactions of
the planar conjugated moieties of the dyes. Therefore, pseudo-
dimer components are mainly arranged according to the head-
to-tail pattern, their ethylene bonds being spatially proximate.
These complexes are preorganized towards stereospecific cross-
[2+2] photocycloaddition (cross-PCA) reaction to give the only rctt
isomer of cyclobutane derivatives out of 38 theoretically possible
isomers (considering the possible auto-PCA and cross-PCA reac-
tions in a mixture of two dyes). The structural characteristics of
the dyes that benefit more efficient cross-PCA were elucidated.
The targeted design of pseudodimeric complexes of styryl dyes
may provide for the elaboration of new promising optical data
recording systems operating with high efficiency in the specified
spectral range.
Fig. 9 1H NMR spectra (cyclobutane proton region) of compounds (a) rctt-3a,
(b) rctt-3b, (c) rctt-3c, and (d) rctt-3d, DMSO-d6, 30 1C.
planes of the indicated rings are 38.81 and 55.71. It is typical that
the C5H4N(3)/benzocrown pair is less twisted, obviously, due to
the ‘‘constricting’’ action of the complex formation between the
ammonium group and the macroheterocycle.
Experimental section
General
The melting points were measured using a Mel-Temp II apparatus
in a capillary and are uncorrected. The 1H and 13C NMR spectra
were recorded on a Bruker DRX500 instrument in DMSO-d6 and
MeCN-d3 using the solvent as the internal reference (dH 2.50
and 1.96, respectively; dC 39.43 for DMSO-d6); J values are given
13
in Hz. 2D NOESY spectra and 1Hꢀ C correlation spectra
(HSQC and HMBC) were used to assign the proton and carbon
signals (see Chart 2 and Scheme 5 for atom numbering in
compounds 1–3); the mixing time in the NOESY experiments
was 300 ms. Absorption and emission spectra were recorded on
a Cary 4000 spectrophotometer (Agilent) and a RF-5301PC
spectrofluorimeter (Shimadzu) in the range of 200–600 nm
and 320–750 nm, respectively, with an increment of 1 nm in
MeCN (spectroscopic grade, the water content r0.03% v/v,
Cryochrom, Russian Federation) at ambient temperature using
1 cm quartz cells. Elemental analyses were performed at the micro-
analytical laboratory of the A. N. Nesmeyanov Institute of Organoele-
ment Compounds (Moscow, Russian Federation); the samples for
elemental analysis were dried in vacuo at 80 1C. All of the obtained
compounds containing perchlorate anions are non-explosive.
Fig. 10 Structure of the main component in rctt-3cꢁ2C6H6ꢁ0.75MeCNꢁ
0.25H2O. Thermal ellipsoids are drawn at the 40% probability level.
Hydrogen bonds are drawn with dash lines.
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3
Preparation
7.38 (1 H, d, J 16.4, HC = CHPy), 7.72 (3 H, br s, NH3), 7.73
(2 H, d, 3J 8.6, 20-H, 60-H), 8.00 (1 H, d, 3J 16.4, HC = CHPy), 8.21
(2 H, d, 3J 6.6, 3-H, 5-H) and 8.86 (2 H, d, 3J 6.6, 2-H, 6-H);
dC(125.76 MHz; DMSO-d6; 30 1C) 28.4 (CH2CH2NH3), 35.7
(CH2NH3), 55.3 (MeO), 56.6 (CH2N), 114.6 (30-C, 50-C), 120.6
(HC = CHPy), 123.4 (3-C, 5-C), 127.7 (10-C), 130.0 (20-C, 60-C),
141.0 (HC = CHPy), 144.0 (2-C, 6-C), 153.5 (4-C) and 161.2 (40-C).
1-(3-Ammoniopropyl)-4-[(E)-2-(4-nitrophenyl)vinyl]pyridinium
diperchlorate (1f) was obtained in 48% yield as a light beige
powder: mp 269–270 1C (dec.) (Found: C, 39.83; H, 3.74; N, 8.42.
Calc. for C16H19Cl2N3O10 (484.24): C, 39.69; H, 3.95; N, 8.68%);
lambasx(MeCN)/nm 345 (e/dm3 molꢀ1 cmꢀ1 37800); dH(500.13 MHz;
DMSO-d6; 25 1C) 2.19 (2 H, m, CH2CH2NH3), 2.86 (2 H, m,
Styryl dyes 2a,16 2b,17 neutral 4-styrylpyridines 4a–g,18 and
5-bromopentylammonium bromide27 were synthesized according
to published procedures.
Dye 1a was obtained according to a published procedure;9
lambasx(MeCN)/nm 403 (e/dm3 molꢀ1 cmꢀ1 33 600); lfml ax(MeCN)/nm 550.
Dye 1b was obtained according to a published procedure;14
lambasx(MeCN)/nm 348 (e/dm3 molꢀ1 cmꢀ1 29 600); lfml ax(MeCN)/nm 367.
Dye 1g was obtained according to a published procedure;15
lambasx(MeCN)/nm 346 (e/dm3 molꢀ1 cmꢀ1 37 400); lfml ax(MeCN)/nm 438.
Dye 2c was obtained according to a published procedure;7
lmabasx(MeCN)/nm 431 (e/dm3 molꢀ1 cmꢀ1 41700); lmfl ax(MeCN)/nm
535; dC(125.76 MHz; DMSO-d6; 30 1C) 14.0 (Me), 44.2 (CH2N), 68.3
(40-CH2OAr), 68.4 (40-CH2CH2OAr), 68.5 (30-CH2OAr, 30-CH2CH2OAr),
69.6 (CH2O), 69.7 (3 ꢂ CH2O), 69.8 (CH2O), 69.9 (CH2O), 110.4
(HC = CHHet), 112.6 (50-C), 112.9 (20-C), 116.3 (4-C), 124.2 (7-C),
125.8 (60-C), 126.8 (10-C), 127.9 (7a-C), 128.1 (6-C), 129.3 (5-C),
140.8 (3a-C), 148.4 (30-C), 149.6 (HC = CHHet), 152.5 (40-C) and
171.6 (2-C).
3
CH2NH3), 4.59 (2 H, t, J 7.1, CH2N), 7.73 (3 H, br s, NH3), 7.78
(1 H, d, 3J 16.5, HC = CHPy), 8.01 (2 H, d, 3J 9.1, 20-H, 60-H), 8.14
3
3
(1 H, d, J 16.5, HC = CHPy), 8.35 (2 H, d, J 6.9, 3-H, 5-H), 8.36
3
(2 H, d, J 9.1, 30-H, 50-H) and 9.00 (2 H, d, 3J 6.9, 2-H, 6-H);
dC(125.76 MHz; DMSO-d6; 30 1C) 28.4 (CH2CH2NH3), 35.7
(CH2NH3), 57.1 (CH2N), 124.2 (30-C, 50-C), 124.7 (3-C, 5-C),
127.4 (HC = CHPy), 128.9 (20-C, 60-C), 138.1 (HC = CHPy), 141.4
(10-C), 144.6 (2-C, 6-C), 147.8 (40-C) and 152.1 (4-C).
Cyclobutane rctt-3a was obtained according to a published
procedure;9 lambasx(MeCN)/nm 231 and 281 (e/dm3 molꢀ1 cmꢀ1
34400 and 6300); dC(125.76 MHz; DMSO-d6; 30 1C) 16.2 (MeCH2),
28.1 (CH2CH2NH3), 35.7 (CH2NH3), 43.5 (d-CH), 44.6 (c-CH),
45.7 (b-CH), 46.6 (a-CH), 55.3 (30 00-MeO), 55.47 (CH2Me), 55.52
(400 0-MeO), 57.2 (CH2N), 67.1 (40-CH2OAr), 67.3 (30-CH2OAr), 68.3
(CH2CH2OAr), 68.4 (CH2CH2OAr), 68.6 (2 ꢂ CH2O), 69.1 (CH2O),
69.2 (CH2O), 69.6 (CH2O), 69.7 (CH2O), 111.2 (500 0-C), 111.4 (20-C,
50-C), 112.1 (20 0 0-C), 119.8 (60 0 0-C), 120.5 (60-C), 127.1 (3-C, 5-C),
1020 7.2 (300-C, 500-C), 130.0 (100 0-C), 130.4 (10-C), 143.2 (2-C, 6-C, 200-C,
6 -C), 145.6 (40-C), 146.4 (30-C), 147.6 (40 0 0-C), 148.4 (300 0-C), 160.2
(400-C) and 160.6 (4-C).
1-(2-Ammonioethyl)-4-[(E)-2-(3,4-dimethoxyphenyl)vinyl]pyridi-
nium diperchlorate (hydrate) (1h) was obtained in 67% yield as a
yellow powder: mp 235–237 1C (dec.) (Found: C, 39.47; H, 4.85; N,
5.83. Calc. for C17H22Cl2N2O10ꢁ1.5H2O (512.29): C, 39.86; H, 4.92;
N, 5.47%); lambasx(MeCN)/nm 407 (e/dm3 molꢀ1 cmꢀ1 34 300);
lfml ax(MeCN)/nm 550; dH(500.13 MHz; DMSO-d6; 30 1C) 3.49
(2 H, m, CH2NH3), 3.84 (3 H, s, 40-MeO), 3.86 (3 H, s, 30-MeO),
4.69 (2 H, m, CH2N), 7.09 (1 H, d, 3J 8.3, 50-H), 7.32 (1 H, dd, 3J 8.3,
4J 1.2, 60-H), 7.40 (1 H, d, 4J 1.2, 20-H), 7.44 (1 H, d, 3J 16.2, HC =
CHPy), 7.95 (3 H, br s, NH3), 8.01 (1 H, d, 3J 16.2, HC = CHPy), 8.21
(2 H, d, 3J 6.6, 3-H, 5-H) and 8.80 (2 H, d, 3J 6.6, 2-H, 6-H); dC(125.76
MHz; DMSO-d6; 30 1C) 38.8 (CH2NH3), 55.57 (MeO), 55.59 (MeO),
56.6 (CH2N), 110.1 (20-C), 111.7 (50-C), 120.7 (HC = CHPy), 123.3
Synthesis of dyes 1c,f–i (general procedure)
A mixture of 4-styrylpyridine 4a,c,f (1.25 mmol) and 3-bromo- (3-C, 5-C, 60-C), 127.9 (10-C), 141.7 (HC = CHPy), 144.5 (2-C, 6-C),
propylammonium bromide (0.82 g, 3.75 mmol) or 2-bromoethyl- 149.1 (30-C), 151.3 (40-C) and 154.0 (4-C).
ammonium bromide (0.77 g, 3.75 mmol) or 5-bromopentyl-
1-(5-Ammoniopentyl)-4-[(E)-2-(3,4-dimethoxyphenyl)vinyl]-
ammonium bromide (0.31 g, 1.25 mmol) was heated at 140–160 1C pyridinium diperchlorate (1i) was obtained in 17% yield as a
(oil bath) in the dark for 4–6 h. After cooling to room temperature, yellow powder: mp 207–210 1C (Found: C, 45.61; H, 5.36; N, 5.18.
the reaction mixture was triturated with hot abs. EtOH (5 cm3) and Calc. for C20H28Cl2N2O10 (527.35): C, 45.55; H, 5.35; N, 5.31%);
then cooled to ꢀ10 1C. The insoluble substance was filtered off, lambasx(MeCN)/nm 400 (e/dm3 molꢀ1 cmꢀ1 31 800); lfml ax(MeCN)/
washed with cold abs. EtOH (2 ꢂ 3 cm3) and CHCl3 (2 ꢂ 3 cm3) and nm 546; dH(500.13 MHz; DMSO-d6; 25 1C) 1.31 (2 H, m,
dried in air to give dibromide of the dye. This dibromide was CH2CH2CH2NH3), 1.57 (2 H, m, CH2CH2NH3), 1.93 (2 H, m,
dissolved in a mixture of abs. EtOH (5 cm3) and water (minimal CH2CH2N), 2.79 (2 H, m, CH2NH3), 3.83 (3 H, s, 40-MeO), 3.85
quantity) with heating, and 70% aq HClO4 (0.31 cm3, 3.6 mmol) (3 H, s, 30-MeO), 4.46 (2 H, t, 3J 7.5, CH2N), 7.08 (1 H, d, 3J 8.6, 50-H),
was added to this solution. After cooling to ꢀ10 1C, the precipitate 7.30 (1 H, dd, 3J 8.6, 4J 1.8, 60-H), 7.38 (1 H, d, 4J 1.8, 20-H), 7.41 (1 H,
thus formed was filtered off, washed with cold abs. EtOH d, 3J 16.2, HC = CHPy), 7.60 (3 H, br s, NH3), 7.97 (1 H, d, 3J 16.2, HC =
(2 ꢂ 2 cm3), and dried in air in the dark to give dye 1c,f,h,i.
CHPy), 8.17 (2 H, d, 3J 6.8, 3-H, 5-H) and 8.87 (2 H, d, 3J 6.8, 2-H, 6-H);
1-(3-Ammoniopropyl)-4-[(E)-2-(4-methoxyphenyl)vinyl]pyridinium dC(125.76 MHz; DMSO-d6; 30 1C) 22.3 (CH2CH2CH2NH3), 26.3
diperchlorate (1c) was obtained in 61% yield as a yellow (CH2CH2NH3), 29.7 (CH2CH2N), 38.5 (CH2NH3), 55.5 (30-MeO), 55.6
powder: mp 185–188 1C (dec.) (Found: C, 43.55; H, 4.57; N, (40-MeO), 59.3 (CH2N), 110.0 (20-C), 111.7 (50-C), 120.7 (HC = CHPy),
5.76. Calc. for C17H22Cl2N2O9 (469.27): C, 43.51; H, 4.73; N, 123.1 (60-C), 123.2 (3-C, 5-C), 127.9 (10-C), 141.2 (HC = CHPy), 143.9
5.97%); lambasx(MeCN)/nm 388 (e/dm3 molꢀ1 cmꢀ1 36400); (2-C, 6-C), 149.0 (30-C), 151.1 (40-C) and 153.2 (4-C).
lfml ax(MeCN)/nm 500; dH(500.13 MHz; DMSO-d6; 25 1C) 2.18
1-(3-Ammoniopropyl)-4-(E)-2-[4-(methylthio)phenyl]vinylpyr-
(2 H, m, CH2CH2NH3), 2.85 (2 H, m, CH2NH3), 3.84 (3 H, s, idinium diperchlorate (1d). A mixture of compound 4d (0.15 g,
MeO), 4.54 (2 H, t, 3J 7.0, CH2N), 7.08 (2 H, d, 3J 8.6, 30-H, 50-H), 0.66 mmol), 3-bromopropylammonium bromide (0.17 g, 0.78 mmol),
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NJC
and dry MeCN (10 cm3) was heated at 80 1C with stirring in the of the complex was proved by 1H NMR (in DMSO-d6; in this
dark for 30 h. After cooling to room temperature, an insoluble solvent, all complexes decompose to give a mixture of free dyes;
substance was filtered off, washed with dry MeCN (3 cm3), and see Fig. S32–S39 in the ESI†).
dried in air to give crude dibromide of the dye (0.19 g) as
Complex (1a)1.5ꢁ2a (hydrate) was obtained in 63% yield; water
a tawny powder. The dibromide was dissolved in abs. EtOH release 4115 1C, mp 230–235 1C (dec.) (Found: C, 47.12; H, 5.10; N,
(3 cm3) with heating, and 70% aq HClO4 (0.14 cm3, 1.62 mmol) 3.89. Calc. for 1.5C18H24Cl2N2O10ꢁC25H34ClNO10ꢁ1.5H2O (1319.96):
was added to the solution. After cooling to room temperature, C, 47.32; H, 5.57; N, 4.25%).
the precipitate thus formed was filtered off, washed with abs.
Complex 1bꢁ2a was obtained in 82% yield; mp 98–100 1C (dec.)
EtOH (2 ꢂ 2 cm3) and Et2O (5 cm3), and dried in air in the dark (Found: C, 50.14; H, 5.61; N, 4.19. Calc. for C16H20Cl2N2O8ꢁ
to give dye 1d (0.15 g, overall yield 47%) as a tawny powder: C25H34ClNO10 (983.23): C, 50.08; H, 5.54; N, 4.27%).
mp 207–210 1C (Found: C, 42.11; H, 4.61; N, 5.63. Calc. for
Complex 1cꢁ2a (hydrate) was obtained in 88% yield; glass
C
17H22Cl2N2O8S (485.34): C, 42.07; H, 4.57; N, 5.77%); transition 4110 1C (Found: C, 49.50; H, 5.71; N, 4.11. Calc. for
lmabasx(MeCN)/nm 400 (e/dm3 molꢀ1 cmꢀ1 30 700); lmfl ax(MeCN)/nm
C
17H22Cl2N2O9ꢁC25H34ClNO10ꢁ0.5H2O (1022.27): C, 49.35; H,
558; dH(500.13 MHz; DMSO-d6; 25 1C) 2.17 (2 H, m, CH2CH2NH3), 5.62; N, 4.11%).
2.54 (3 H, s, MeS), 2.84 (2 H, m, CH2NH3), 4.54 (2 H, t,
Complex 1dꢁ2a was obtained in 85% yield; mp 141–143 1C
3
3
3J 6.8, CH2N), 7.37 (2 H, d, J 8.4, 30-H, 50-H), 7.50 (1 H, d, J (dec.) (Found: C, 49.09; H, 5.54; N, 4.07. Calc. for C17H22Cl2N2O8Sꢁ
16.4, HC = CHPy), 7.70 (2 H, d, 3J 8.4, 20-H, 60-H), 7.73 (3 H, br s, C25H34ClNO10 (1029.33): C, 49.01; H, 5.48; N, 4.08%).
NH3), 8.01 (1 H, d, 3J 16.4, HC = CHPy), 8.24 (2 H, d, 3J 6.8,
Complex 1fꢁ2a was obtained in 64% yield; mp 139–142 1C
3-H, 5-H) and 8.90 (2 H, d, 3J 6.8, 2-H, 6-H); dC(125.76 MHz; (Found: C, 47.67; H, 5.21; N, 5.38. Calc. for C16H19Cl2N3O10ꢁ
DMSO-d6; 27 1C) 14.1 (MeS), 28.4 (CH2CH2NH3), 35.7 (CH2NH3),
56.7 (CH2N), 122.0 (HC = CHPy), 123.7 (3-C, 5-C), 125.7 (30-C,
C
25H34ClNO10 (1028.23): C, 47.89; H, 5.20; N, 5.45%).
Complex 1gꢁ2a was obtained in 90% yield;15 glass transition
50-C), 128.6 (20-C, 60-C), 131.4 (10-C), 140.6 (HC = CHPy), 142.0 B155 1C, mp 4 177 1C (dec.).
(40-C), 144.1 (2-C, 6-C) and 153.2 (4-C).
Complex 1aꢁ2b (hydrate) was obtained in 95% yield; mp 178–
1-(3-Ammoniopropyl)-4-(E)-2-[4-(dimethylamino)phenyl]vinyl- 182 1C (Found: C, 50.67; H, 5.60; N, 3.73. Calc. for C18H24Cl2N2O10ꢁ
pyridinium diperchlorate (1e). A mixture of compound 4e (0.22 g, C29H36ClNO10ꢁH2O (1111.36): C, 50.79; H, 5.62; N, 3.78%).
0.97 mmol), 3-bromopropylammonium bromide (0.26 g, 1.17 mmol),
Complex 1aꢁ2c was obtained in 63% yield; mp 168–172 1C
and dry MeCN (15 cm3) was heated at 80 1C with stirring in the dark (Found: C, 49.06; H, 5.28; N, 3.86. Calc. for C18H24Cl2N2O10ꢁ
for 60 h. After cooling to room temperature, an insoluble substance
was filtered off, washed with CHCl3 (3 ꢂ 10 cm3), abs. EtOH
(2 ꢂ 3 cm3), and benzene (10 cm3), and dried in air to give crude
dibromide of the dye (0.38 g) as a reddish-brown powder. The
C27H34ClNO10S (1099.37): C, 49.16; H, 5.32; N, 3.82%).
Synthesis of cyclobutane derivatives rctt-3b–d (general
procedure)
dibromide was dissolved in MeOH (15 cm3) with heating, and a A solution of a mixture of dye 1b–d (27 mmol) and dye 2a (14.8 mg,
solution of NaClO4 (0.25 g, 2.05 mmol) in MeOH (3 cm3) was 27 mmol) in dry MeCN (16 cm3) in a glass flask was irradiated with
added to the dye solution. After cooling to ꢀ10 1C, the pre- light from an incandescent lamp (power 60 W) from a distance of
cipitate thus formed was quickly filtered off and dried in air to B15 cm for 200 h. The reaction mixture was concentrated in vacuo
give dye 1e (0.20 g, overall yield 43%) as a dark red powder: mp to a volume of B5–6 cm3, and this solution was slowly saturated
201–204 1C (Found: C, 44.70; H, 5.33; N, 8.94. Calc. for with vapour of a benzene–dioxane mixture (B2 : 1, v/v) at room
abs
C
18H25Cl2N3O8 (482.31): C, 44.82; H, 5.23; N, 8.71%); l
temperature (for 1–2 weeks). The fine-grained crystalline precipitate
max
(MeCN)/nm 482 (e/dm3 molꢀ1 cmꢀ1 42500); lfml ax(MeCN)/nm thus formed was decanted and dried in air to give compound rctt-
634; dH(500.13 MHz; DMSO-d6; 24 1C) 2.15 (2 H, m, CH2CH2NH3), 3b–d as a yellowish powder.
3
2.83 (2 H, m, CH2NH3), 3.03 (6 H, s, Me2N), 4.47 (2 H, t, J 7.0,
1-(3-Ammoniopropyl)-4-r-[2-c-(2,3,5,6,8,9,11,12,14,15-decahydro-
3
3
CH2N), 6.80 (2 H, d, J 9.0, 30-H, 50-H), 7.19 (1 H, d, J 16.0, HC = 1,4,7,10,13,16-benzohexaoxacyclooctadecin-18-yl)-3-t-(1-ethylpyr-
3
CHPy), 7.60 (2 H, d, J 9.0, 20-H, 60-H), 7.71 (3 H, br s, NH3), 7.94 idinium-4-yl)-4-t-phenylcyclobutyl]pyridinium triperchlorate (rctt-3b)
(1 H, d, 3J 16.0, HC = CHPy), 8.09 (2 H, d, 3J 6.9, 3-H, 5-H) and 8.74 was obtained in 95% yield: mp 4 154 1C (dec.) (Found: C, 51.54; H,
3
(2 H, d, J 6.9, 2-H, 6-H); dC(125.76 MHz; DMSO-d6; 25 1C) 28.4 5.75; N, 3.96. Calc. for C41H54Cl3N3O18ꢁ0.5C6H6 (1022.29): C, 51.69;
(CH2CH2NH3), 35.7 (CH2NH3), 39.6 (Me2N), 56.1 (CH2N), 111.9 H, 5.62; N, 4.11%); lambasx(MeCN)/nm 225, B258sh and B285 sh
(30-C, 50-C), 117.0 (HC = CHPy), 122.5 (3-C, 5-C, 10-C), 130.2 (e/dm3 molꢀ1 cmꢀ1 29 700, 10 700 and 4700); dH(500.13 MHz;
(20-C, 60-C), 142.4 (HC = CHPy), 143.4 (2-C, 6-C), 151.9 (40-C) and DMSO-d6; 25 1C) 1.40 (3 H, t, 3J 7.3, Me), 2.12 (2 H, m, CH2CH2N),
154.0 (4-C).
2.28–2.43 (2 H, m, CH2NH3), 3.62 (4 H, s, 2 ꢂ CH2O), 3.65 (4 H, m,
Complexes between dyes 1a–d,f,g and 2a–c (general method). A 2 ꢂ CH2O), 3.71 (4 H, m, 2 ꢂ CH2O), 3.79 (4 H, m, 2 ꢂ
solution of a mixture of dye 1 (15 mmol) and dye 2 (15 mmol) in CH2CH2OAr), 3.92 (2 H, m, 30-CH2OAr), 4.08 (2 H, m,
MeCN (B4 cm3) was slowly (for 2–3 weeks) saturated with a vapour 40-CH2OAr), 4.48 (2 H, q, 3J 7.3, CH2Me), 4.55 (2 H, t, 3J 5.9,
of benzene or a benzene–dioxane mixture (B2 : 1, v/v) at room CH2N), 4.84 (1 H, m, b-CH), 4.97 (2 H, m, a-CH, d-CH), 5.09
temperature in the dark. The precipitate thus formed was decanted (1 H, m, c-CH), 6.53 (1 H, d, 4J 1.4, 20-H), 6.93 (1 H, d, 3J 8.6, 50-H),
and dried in air to give an appropriate complex 1ꢁ2 as a yellow 7.03 (1 H, dd, 3J 8.6, 4J 1.4, 60-H), 7.15 (1 H, br t, 3J 7.0, 400 0-H), 7.20
(for dye 2a) or orange (for dyes 2b,c) powder. The stoichiometry (3 H, br s, NH3), 7.24 (2 H, t, 3J 7.5, 300 0-H, 50 00-H), 7.28 (2 H, br d,
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3J 7.3, 20 00-H, 600 0-H), 7.94 (2 H, d, 3J 6.8, 300-H, 500-H), 7.97 (2 H, d, (2 H, d, 3J 6.7, 3-H, 5-H), 8.81 (2 H, d, J 6.7, 2-H, 6-H) and 8.89
3
3J 6.8, 3-H, 5-H), 8.82 (2 H, d, 3J 6.8, 2-H, 6-H) and 8.88 (2 H, d, J 6.7, 200-H, 600-H); dC(125.76 MHz; DMSO-d6; 30 1C)
3
(2 H, d, J 6.8, 200-H, 600-H); dC(125.76 MHz; DMSO-d6; 30 1C) 14.5 (MeS), 16.1 (MeCH2), 28.1 (CH2CH2NH3), 35.6 (CH2NH3),
16.2 (Me), 28.1 (CH2CH2NH3), 35.6 (CH2NH3), 43.5 (d-CH), 44.2 43.0 (d-CH), 44.2 (c-CH), 45.9 (b-CH), 46.6 (a-CH), 55.5 (CH2Me),
(c-C), 45.9 (b-CH), 46.5 (a-CH), 55.4 (CH2Me), 57.1 (CH2N), 57.2 (CH2N), 67.1 (40-CH2OAr), 67.2 (30-CH2OAr), 68.2 (CH2CH2-
67.1 (40-CH2OAr), 67.3 (30-CH2OAr), 68.2 (CH2CH2OAr), 68.4 OAr), 68.4 (CH2CH2OAr), 68.5 (2 ꢂ CH2O), 69.1 (CH2O), 69.2
(CH2CH2OAr), 68.6 (2 ꢂ CH2O), 69.1 (CH2O), 69.2 (CH2O), 69.6 (CH2O), 69.6 (CH2O), 69.7 (CH2O), 111.6 (20-C), 111.7 (50-C),
(CH2O), 69.7 (CH2O), 111.6 (20-C), 111.7 (50-C), 120.5 (60-C), 126.8 120.4 (60-C), 125.8 (30 0 0-C, 500 0-C), 127.0 (300-C, 500-C), 127.2 (3-C, 5-
(40 00-C), 127.0 (300-C, 500-C), 127.3 (3-C, 5-C), 127.8 (200 0-C, 600 0-C), C), 128.4 (20 00-C, 60 0 0-C), 130.2 (10-C), 134.3 (10 00-C), 136.7 (40 0 0-C),
128.3 (30 0 0-C, 50 00-C), 130.3 (10-C), 137.7 (10 0 0-C), 143.18 (2-C, 6-C), 143.2 (2-C, 6-C), 143.3 (200-C, 600-C), 145.7 (40-C), 146.4 (30-C),
143.24 (200-C, 600-C), 145.7 (40-C), 146.4 (30-C), 159.9 (400-C) and 159.8 (400-C) and 160.4 (4-C).
160.5 (4-C).
1H NMR titration
1-(3-Ammoniopropyl)-4-r-[2-c-(2,3,5,6,8,9,11,12,14,15-decahydro-
1,4,7,10,13,16-benzohexaoxacyclooctadecin-18-yl)-3-t-(1-ethyl- MeCN-d3 (water content o0.05% v/v, FGUP RNTs Prikladnaya
pyridinium-4-yl)-4-t-(4-methoxyphenyl)cyclobutyl]pyridinium triper- Khimiya, St. Petersburg, Russian Federation) was used as the
chlorate (rctt-3c) was obtained in 92% yield: mp 261–262 1C (dec.) solvent. The stability constants of the complexes of dyes 1a–i
(Found: C, 51.29; H, 5.81; N, 3.94. Calc. for C42H56Cl3N3O19ꢁ0.5C6H6 with dyes 2a–c were determined by analyzing the shifts of the
(1052.32): C, 51.36; H, 5.65; N, 3.99%); lambasx(MeCN)/nm 230 and proton signals of dyes 2a–c (DdH) depending on the concentration of
B280sh (e/dm3 molꢀ1 cmꢀ1 38 600 and 5700); dH(500.13 MHz; the added dye 1a–i. The total concentrations of dyes 2a–c did not
DMSO-d6; 30 1C) 1.42 (3 H, t, 3J 7.3, MeCH2), 2.11 (2 H, m, change being equal to B1 ꢂ 10ꢀ3 M, and the dye 1a–i concentra-
CH2CH2N), 2.29–2.44 (2 H, m, CH2NH3), 3.62 (4 H, s, 2 ꢂ CH2O), tions were varied starting from zero (the maximum 1 to 2 concen-
3.65 (4 H, m, 2 ꢂ CH2O), 3.67 (3 H, s, MeO), 3.71 (4 H, m, 2 ꢂ tration ratio was B3). The DdH values were measured to an accuracy
CH2O), 3.79 (4 H, m, 2 ꢂ CH2CH2OAr), 3.92 (2 H, m, 30-CH2OAr), of 0.001 ppm. The stability constants of the complexes were calcu-
4.08 (2 H, m, 40-CH2OAr), 4.50 (2 H, q, 3J 7.3, CH2Me), 4.55 (2 H, t, lated using the HYPNMR program21 and are shown in Table 1.
3J 6.0, CH2N), 4.82 (1 H, m, b-CH), 4.89 (2 H, m, a-CH, d-CH), 5.02
(1 H, m, c-CH), 6.52 (1 H, d, 4J 1.5, 20-H), 6.79 (2 H, d, 3J 8.7, 300 0-H,
Irradiation of dyes 1a–i (general procedure)
500 0-H), 6.93 (1 H, d, 3J 8.4, 50-H), 7.02 (1 H, dd, 3J 8.4, 4J 1.5, 60-H), UV-vis spectra of dyes 1a–i (MeCN, Cdye E 1 ꢂ 10ꢀ4 M, 0.1 cm
7.20 (2 H, d, 3J 8.7, 20 00-H, 600 0-H), 7.21 (3 H, br s, NH3), 7.91 (2 H, d, quartz cells, ambient temperature) and their photolysis products
3J 6.7, 300-H, 500-H), 7.94 (2 H, d, 3J 6.7, 3-H, 5-H), 8.80 (2 H, d, 3J 6.7, were recorded in the range 200–600 nm with an increment of
3
2-H, 6-H) and 8.88 (2 H, d, J 6.7, 200-H, 600-H); dC(125.76 MHz; 0.5 nm (Fig. 6 and Fig. S42–S50 in the ESI†). The unfiltered light
DMSO-d6; 30 1C) 16.2 (MeCH2), 28.1 (CH2CH2NH3), 35.7 (CH2NH3), of a 60 W incandescent lamp was used for irradiation, the
42.9 (d-CH), 44.3 (c-CH), 45.8 (b-CH), 46.9 (a-CH), 54.9 (MeO), 55.5 distance to the light source was B15 cm. The solutions were
(CH2Me), 57.2 (CH2N), 67.1 (40-CH2OAr), 67.2 (30-CH2OAr), 68.2 not degassed prior to irradiation, as an electrocyclic reaction of
(CH2CH2OAr), 68.4 (CH2CH2OAr), 68.5 (2 ꢂ CH2O), 69.1 (CH2O), the dyes, which could result in the formation of dihydrophenan-
69.2 (CH2O), 69.6 (CH2O), 69.7 (CH2O), 111.5 (20-C), 111.7 (50-C), threne analogues, does not occur.
113.7 (300 0-C, 500 0-C), 120.4 (60-C), 127.0 (300-C, 500-C), 127.2 (3-C, 5-C),
Irradiation of pseudodimeric complexes 1ꢁ2 (general
129.0 (20 00-C, 600 0-C), 129.5 (100 0-C), 130.3 (10-C), 143.2 (2-C, 6-C),
143.3 (200-C, 600-C), 145.6 (40-C), 146.4 (30-C), 158.0 (400 0-C), 160.1
(400-C) and 160.6 (4-C).
procedure)
UV-vis spectra of a mixture of dye 1a–i with dye 2a or dye 1a
1-(3-Ammoniopropyl)-4-r-2-c-(2,3,5,6,8,9,11,12,14,15-decahydro- with dye 2b,c (MeCN, C1 = C2 = 5 ꢂ 10ꢀ4 M, 0.1 cm quartz cell,
1,4,7,10,13,16-benzohexaoxacyclooctadecin-18-yl)-3-t-(1-ethylpyr- ambient temperature) and their photolysis products were
idinium-4-yl)-4-t-[4-(methylthio)phenyl]cyclobutylpyridinium tri- recorded in the range of 200–600 nm with an increment of
perchlorate (rctt-3d) was obtained in 93% yield: mp 258–259 1C 0.5 nm (Fig. 7 and Fig. S51–S57 in the ESI†). The unfiltered light
(dec.) (Found: C, 49.16; H, 5.37; N, 4.07. Calc. for C42H56Cl3- of a 60 W incandescent lamp was used for irradiation, the
N3O18S (1029.33): C, 49.01; H, 5.48; N, 4.08%); lambasx(MeCN)/nm distance to the light source was B15 cm. The solutions were
231, 258 and B280sh (e/dm3 molꢀ1 cmꢀ1 35 000, 25 300 and not degassed before irradiation.
8300); dH(500.13 MHz; DMSO-d6; 30 1C) 1.42 (3 H, t, 3J 7.3,
MeCH2), 2.11 (2 H, m, CH2CH2N), 2.29–2.43 (2 H, m, CH2NH3),
X-ray crystallography
2.39 (3 H, s, MeS), 3.62 (4 H, s, 2 ꢂ CH2O), 3.65 (4 H, m, 2 ꢂ The crystals of styryl dyes 1f and 2c, complexes 1dꢁ2a and 1fꢁ2a, and
CH2O), 3.71 (4 H, m, 2 ꢂ CH2O), 3.79 (4 H, m, 2 ꢂ CH2CH2OAr), cyclobutane rctt-3c were grown from MeCN solutions, which were
3.92 (2 H, m, 30-CH2OAr), 4.08 (2 H, m, 40-CH2OAr), 4.51 (2 H, q, slowly saturated with benzene or a benzene–dioxane mixture
3
3J 7.3, CH2Me), 4.55 (2 H, t, J 5.9, CH2N), 4.82 (1 H, m, b-CH), (B2 : 1, v/v) by the vapour diffusion method at ambient tempera-
4.92 (2 H, m, a-CH, d-CH), 5.04 (1 H, m, c-CH), 6.53 (1 H, d, ture in the dark. The single crystals of all compounds were
4J 1.7, 20-H), 6.93 (1 H, d, 3J 8.4, 50-H), 7.02 (1 H, dd, 3J 8.4, 4J 1.7, coated with perfluorinated oil and mounted on a Bruker SMART-
60-H), 7.12 (2 H, d, 3J 8.4, 30 0 0-H, 500 0-H), 7.21 (3 H, br s, NH3), 7.22 CCD diffractometer [graphite monochromatized Mo-Ka radia-
(2 H, d, 3J 8.4, 20 00-H, 60 0 0-H), 7.93 (2 H, d, 3J 6.7, 300-H, 500-H), 7.94 tion (l = 0.71073 Å) or Cu-Ka radiation (l = 1.54178 Å), o scan
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mode] under a stream of cold nitrogen. The sets of experimental two conformations with the occupancy ratio of 0.67: 0.33.
reflections were measured, and the structures were solved by The conjugated fragment of the second dye 2a cation is dis-
direct methods and refined with anisotropic thermal parameters ordered according to ‘‘pedal’’ isomerization and the s-conformer
for all non-hydrogen atoms (except for the disordered benzene occupancy ratio is 0.53: 0.47. The ethylene moiety of one of the
molecule in structure rctt-3cꢁ2C6H6ꢁ0.75MeCNꢁ0.25H2O and two independent dye 1d cations is also ‘‘pedal’’-disordered with
whole structure 1dꢁ2aꢁ0.7C6H6ꢁ0.7H2O, which were refined iso- the occupancy ratio of 0.62: 0.38. The MeS group of this cation is
tropically). In the case of 1fꢁ0.25H2O, absorption correction was disordered over two sites with the same occupancy ratio. Each of
applied using the SADABS method. The hydrogen atoms were the six independent perchlorate anions Cl(1)O4,. . .,Cl(6)O4 are
fixed at calculated positions at carbon atoms and then refined disordered over two sites with the occupancy ratios of 0.54: 0.46,
with an isotropic approximation for 2cꢁC4H8O2ꢁ3H2O or by using 0.56: 0.44, 0.73: 0.27, 0.59: 0.41, 0.59 : 0.41, and 0.61: 0.39,
a ‘‘riding’’ model for other structures. The hydrogen atoms of respectively. One of the three independent benzene molecules is
the NH3+ groups in all structures were calculated geometrically and situated at the symmetry centre. Another benzene molecule is
refined by using the ‘‘riding’’ model. The hydrogen atoms of the placed in the two-fold axis and is disordered over two sites via
water molecules of solvation in 2cꢁC4H8O2ꢁ3H2O were found from rotation in the own plane with the occupancy ratio of 0.72 : 0.28. The
the Fourier syntheses and then refined isotropically. In other third benzene molecule has the occupancy of 0.40 and alternates
hydrated structures, water hydrogen atoms were not located.
with water molecules H2O(2W),...,H2O(6W). All water molecules of
Crystal data for 1fꢁ0.25H2O: C16H19.5Cl2N3O10.25, M = 488.74, solvation have occupancies of 0.30 or 0.20. SADI commands were
orthorhombic, space group Pbcn (no. 60), yellowish plate, a = applied in order to constrain the disordered fragments. For the
16.3977(5) Å, b = 8.3891(3) Å, c = 29.1772(9) Å, V = 4013.7(2) Å3, reason of low accuracy of structure 1dꢁ2aꢁ0.7C6H6ꢁ0.7H2O we do not
T = 100(2) K, Z = 8, m = 3.501 mmꢀ1, rcalc = 1.618 g cmꢀ3
,
discuss its structural details, but consider only the general view, that
2ymax = 114.591, 11 130 reflections measured, 2475 unique is, the connectivity scheme that surely is realistic.
(Rint = 0.0614), R1 = 0.0588 (1891 reflections with I 4 2s(I)),
Crystal data for 1fꢁ2aꢁ0.5C6H6ꢁ2H2O: C44H60Cl3N4O22, M =
wR2 = 0.1179 (all data), goodness-of-fit on F2 = 1.035, 342 para- 1103.31, triclinic, space group P1 (no. 2), yellow needle, a =
%
meters, min/max residual electron density = ꢀ0.307/0.397 ꢀe Åꢀ3
.
10.7742(7) Å, b = 12.9619(9) Å, c = 19.5026(14) Å, a = 74.870(3)1,
The H2O(1W) water molecule of solvation lies in a two-fold axis b = 74.856(3)1, g = 80.051(3)1, V = 2521.9(3) Å3, T = 120(2) K,
with the occupancy of 0.25. Both independent perchlorate Z = 2, m = 0.267 mmꢀ1, rcalc = 1.453 gcmꢀ3, 2ymax = 51.9981,
anions are disordered over two sites with occupancy ratios of 14 526 reflections measured, 9469 unique (Rint = 0.0752), R1 =
0.89: 0.11 and 0.56: 0.44. ISOR command was applied to oxygen 0.0715 (4080 reflections with I 4 2s(I)), wR2 = 0.1942 (all data),
atoms of the disordered anions in order to constrain their goodness-of-fit on F2 = 0.873, 794 parameters, min/max residual
anisotropic thermal parameters.
electron density = ꢀ0.423/0.499 ꢀe Åꢀ3. The benzene molecule of
Crystal data for 2cꢁC4H8O2ꢁ3H2O: C31H48ClNO15S, M = 742.21, solvation is situated at the symmetry centre. The perchlorate
%
triclinic, space group P1 (no. 2), red block, a = 7.9257(5) Å, b = anion Cl(2)O4 and the conjugated moiety of the dye 2a cation
11.4270(7) Å, c = 19.6257(10) Å, a = 100.100(2)1, b = 100.108(2)1, g = are disordered over two sites with the occupancy ratios of
93.581(2)1, V = 1714.74(17) Å3, T = 120(2) K, Z = 2, m = 0.245 mmꢀ1
,
0.74 : 0.26 and 0.70 : 0.30, respectively. The anions Cl(3)O4 and
rcalc = 1.437 g cmꢀ3, 2ymax = 56.9981, 10 164 reflections measured, Cl(4)O4 are situated near the symmetry centres with equal
8476 unique (Rint = 0.0335), R1 = 0.0578 (4386 reflections with I 4 occupancies of 0.50. SADI and ISOR commands were applied
2s(I)), wR2 = 0.1381 (all data), goodness-of-fit on F2 = 0.875, 634 to constrain these disordered groups.
parameters, min/max residual electron density = ꢀ0.489/0.378 ꢀe Åꢀ3
.
Crystal data for rctt-3cꢁ2C6H6ꢁ0.75MeCNꢁ0.25H2O: C55.5H70.75
-
No constraints were applied.
Cl3N3.75O19.25, M = 1204.75, orthorhombic, space group Pca21
Crystal data for 1dꢁ2aꢁ0.7C6H6ꢁ0.7H2O: C46.2H61.6Cl3N3O18.7S, (no. 29), colourless plate, a = 14.0228(9) Å, b = 18.0075(11) Å, c =
M = 1096.59, monoclinic, space group C2/c (no. 15), yellow block, 22.8626(14) Å, V = 5773.2(6) Å3, T = 120(2) K, Z = 4, m =
a = 37.878(8) Å, b = 16.492(3) Å, c = 35.710(7) Å, b = 106.404(3)1, 0.237 mmꢀ1, rcalc = 1.386 g cmꢀ3, 2ymax = 56.0001, 57 119 reflections
V = 21399(8) Å3, T = 120(2) K, Z = 16, m = 0.284 mmꢀ1, rcalc
=
measured, 13 902 unique (Rint = 0.2335), R1 = 0.0818 (5745 reflections
1.361 g cmꢀ3, 2ymax = 54.0001, 100229 reflections measured, with I 4 2s(I)), wR2 = 0.1730 (all data), goodness-of-fit on F2
=
23352 unique (Rint = 0.2225), R1 = 0.1843 (6415 reflections with 0.898, 717 parameters, min/max residual electron density = ꢀ0.323/
ꢀ
I 4 2s(I)), wR2 = 0.5145 (all data), goodness-of-fit on F2 = 1.180, 0.510 e Åꢀ3. One of the two independent benzene molecules is
764 parameters, min/max residual electron density = ꢀ1.216/ disordered over two close sites with the occupancy ratio of 0.52 : 0.48.
ꢀ
1.285 e Åꢀ3. The reflections were collected from a weakly The MeCN, H2O(1W), and H2O(2W) molecules of solvation are
reflecting crystal (mean I/s(I) = 1.09). For this reason the final situated in one and the same site with the occupancies of 0.75,
parameters are characterized by low accuracy. Unfortunately, we 0.14, and 0.11, respectively. ISOR command was applied to these
failed to obtain better crystals and better structural data. Never- molecules to constrain their anisotropic thermal parameters.
theless, we include this structure in this article without discuss-
All the calculations were performed using the SHELXL28 and
ing subtle details of the geometry just in order to show one more Olex-229 software. CCDC reference numbers 1430268 (1fꢁ0.25H2O),
arrangement of two styryl dye cations within a pseudodimeric 1430269 (2cꢁC4H8O2ꢁ3H2O), 1430270 (1dꢁ2aꢁ0.7C6H6ꢁ0.7H2O),
complex. The peripheral part of the crown ether fragment of 1430271 (1fꢁ2aꢁ0.5C6H6ꢁ2H2O), and 1430272 (rctt-3cꢁ2C6H6ꢁ
one of the two independent dye 2a cations is disordered over 0.75MeCNꢁ0.25H2O).
New J. Chem.
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Paper
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Acknowledgements
Financial support from the Russian Science Foundation (project 14-
13-00076) and the Russian Academy of Sciences (in respect of X-ray
diffraction studies of the complexes) is gratefully acknowledged.
L. G. K. thanks the Royal Society of Chemistry for an International
Author Grant. The authors are grateful to Mr Pavel S. Loginov for his
help with the synthesis.
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11 (a) S. C. Coote, A. Pothig and T. Bach, Chem. – Eur. J., 2015,
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