Design of crystal packings of styrylheterocycles and [2+2] photocycloaddition reactions in their single crystals 7.* Crystal structures of 4-styrylpyridine hydroperchlorates and solid-state [2+2] autophotocycloaddition reactions of these compounds

Russian Chemical Bulletin, International Edition, Vol. 60, No. 8, pp. 1734—1761, August, 2011

1734

Design of crystal packings of styrylheterocycles and

[2+2] photocycloaddition reactions in their single crystals

7.* Crystal structures of 4ꢀstyrylpyridine hydroperchlorates and solidꢀstate

[2+2] autophotocycloaddition reactions of these compounds

L. G. Kuz´mina,^aA. I. Vedernikov,^bS. K. Sazonov,^bN. A. Lobova,^bA. V. Churakov,^a

E. Kh. Lermontova,^aJ. A. K. Howard,^cM. V. Alfimov,^band S. P. Gromov^b

^aN. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,

31 Leninsky prosp., 119991 Moscow, Russian Federation.

Fax: +7 (495) 954 1279. Eꢀmail: kuzmina@igic.ras.ru

^bPhotochemistry Center, Russian Academy of Sciences,

7Aꢀ1 ul. Novatorov, 119421 Moscow, Russian Federation.

Fax: +7 (495) 936 1255. Eꢀmail: spgromov@mail.ru

^cDepartment of Chemistry, University of Durham,

South Road, Durham DH1 3LE, UK

A series of 4ꢀstyrylpyridine hydroperchlorates were synthesized, and the [2+2] autophotoꢀ

cycloaddition (PCA) reaction in their polycrystalline films and single crystals resulting in the

centrosymmetric rctt isomers of 1,2,3,4ꢀtetrasubstituted cyclobutanes was investigated. Unlike

neutral styrylpyridines, their protonated forms are better preorganized for the solidꢀstate PCA

reaction. According to the Xꢀray diffraction data, the cations of these compounds, like related

styryl dyes, are mainly stacked in crystals in a headꢀtoꢀhead or headꢀtoꢀtail fashion with equal

probability. Only in the latter type of stacks, the PCA reaction is feasible as a singleꢀcrystalꢀtoꢀ

singleꢀcrystal transformation. The crystal packing is stabilized by hydrogen bonds between

organic cations and perchlorate anions, as well as by other weak directional interactions, for

example, by S...S interactions, thus preventing the atomic displacements in the course of PCA.

The completion of the PCA reaction in single crystals without their degradation was observed

only for 15ꢀcrownꢀ5ꢀcontaining 4ꢀstyrylpyridine hydroperchlorate. The crystals of the latter

compound are stabilized not by hydrogen bonds between the cations and anions but by

N⁺—H...O(macrocycle) hydrogen bonds resulting in the formation of headꢀtoꢀtail stacked

dimers. In the crystals, these dimers are surrounded by a soft shell formed by rotationally and

translationally mobile anions and benzene solvent molecules, as well as by conformationally

flexible crownꢀether moieties of adjacent dimer pairs. This leads to a decrease in the steric

strain that occurs in the crystals in the course of PCA and prevents the degradation of single

crystals. The PCA reaction is accompanied by the reduction in the crystal symmetry due to the

doubling of the unit cell.

Key words: styrylheterocycles, Xꢀray diffraction study, crystal packings, design of crystal

packings, solidꢀstate [2+2] photocycloaddition, cyclobutanes, NMR spectroscopy.

The [2+2] photocycloaddition (PCA) reaction of unꢀ

talline films and single crystals), under visible or UV irraꢀ

diation of unsaturated compounds. Photoreactions that

proceed as singleꢀcrystalꢀtoꢀsingleꢀcrystal transformations

(i.e., with the retention of the crystallinity of the sample)

were documented;^13—19however, the PCA reactions much

more often result in the degradation of single crystals to

form the amorphous (glassy) state or lead to substantial

cracking of single crystals.

saturated compounds giving cyclobutane derivatives,

which was discovered in the beginning of the 20th century

and then developed in 1960s,^2—4continues to attract great

interest,^5—11because this reaction provides a simple and

often the only possible approach to the synthesis of substiꢀ

tuted cyclobutanes and can be used in optical data recordꢀ

ing systems.¹²This reaction can take place in solutions,

gels, and micelles, as well as between solids (in polycrysꢀ

For the PCA reaction to occur, a particular spatial

preorganization of two starting unsaturated molecules is

required. Thus, the molecules should be arranged in paralꢀ

* For Part 6, see Ref. 1.

Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1708—1734, August, 2011.

Crystal packings of protonated styrylpyridines

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

1735

lel planes in such a way that their ethylene groups are

located one above another and are oriented parallel (or

antiparallel) to each other with the distance d₁between

the carbon atoms varying in the range of 3.3—4.2 Å

(Scheme 1). This preorganization can be provided by the

crystal lattice (topochemical control). Hence, the solidꢀ

state PCA reaction proceeds, as a rule, stereoselectively,

i.e., only a few isomers or the only isomer of the cycloꢀ

butane derivative out of a large number of theoretically

possible isomers are formed.

Scheme 1

R = Et (a), H (b); R´ = H (1), NO₂(2), NMe₂(3), OMe (4, 6), SMe (5),

Cl (7); n = 1 (8), 2 (9)

Earlier,^1,20—25we have studied the solidꢀstate PCA reꢀ

actions of styryl dyes of the general formula R—Het⁺—

CH=CH—Ar X^–, in which the quaternized nitrogen hetꢀ

erocycle is linked to the aryl moiety via an ethylene bridge,

and X^–is the inorganic counterion, as well as the PCA

reactions of their synthetic precursors, viz., neutral styrylꢀ

heterocycles Het—CH=CH—Ar. Since PCA can proceed

as the single crystalꢀtoꢀsingle crystal reaction, it is evident

that the crystal packing not only provides the preorganizaꢀ

tion of the structural units required for the reaction but

also ensures the existence of the resulting cyclobutane

structures within the starting crystals (i.e., in the same

space group, with the similar unit cell parameters, in the

presence of inclusions of the unreacted starting molecules).

For a large number of dyes belonging to 4ꢀstyrylpyridine

(for example, 1a—9a), 4ꢀstyrylquinoline, and 2ꢀstyrylꢀ

benzothiazole series, it was found^20—25that these comꢀ

pounds form predominantly stacked architectures in the

crystals (Fig. 1, a and b), in which the chromophoric moiꢀ

eties of adjacent molecules are projected onto each other,

i.e., the crystal lattice provides the preorganization of the

structural units favorable for the PCA reaction. These

packing motifs are not typical of the crystals of neuꢀ

tral styrylheterocycles.¹The latter compounds tend to

form ladder (с), ladderꢀherringbone (d), and sandwich

packings, for example, sandwichꢀherringbone packings (e)

(see Fig. 1).

their mutual projection disappears. The motifs e and f are

derived by the corresponding shifts of a pair of molecules

(rather than of one molecule) in the packings b and a,

a

b

c

d

Undoubtedly, there is a genetic relationship between

the stacking (a, b) and nonꢀstacking motifs (c—f). The

motifs с and d are derived from the motifs a and b, respecꢀ

tively, by the equal shifts of each molecule of the stack in

its own plane with respect to the previous molecule until

e

f

Fig. 1. Types of the crystal packings typical of styryl dyes (a, b)

and neutral styrylheterocycles (c—f); the line segments represent

the lateral projections of the πꢀconjugated systems.

1736

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

Kuz´mina et al.

respectively. The theoretically possible ladderꢀsandwich

motif f has not been observed in the crystal packings of

styryl dyes and neutral styrylheterocycles. Evidently, of

the four packing motifs possible for the latter compounds,

pairs of molecules (stacked dimer pairs) preorganized for

the PCA reaction in single crystals can exist only in two

sandwich motifs e and f, because chromophores are proꢀ

jected onto each other only in these motifs.^1,22

analysis. The absorption spectra of compounds 1b—9b are

similar to the spectra of related dyes 1a—9a (see Ref. 23

and the Experimental section), which confirms the simiꢀ

larity of the πꢀelectron structures of these compounds.

Compounds 1b—9b in the form of polycrystalline films

on glass substrates were irradiated with visible light under

comparable conditions. The compositions of the samples

1

thus obtained were analyzed by H NMR spectroscopy.

The aim of the present study was to modify neutral

styrylheterocycles in such a way that the formation of the

packing motifs e and f or even the transformation to the

stacking motifs a and b would be favorable. In the previous

paper,¹we have described our first approach to the crystal

design of these compounds. This approach is based on the

extension of the πꢀconjugation region in the molecules,

which increases the probability of the appearance of

stacked elements (dimer pairs) in the crystal packing. In

the present study, we developed an alternative approach

based on the use of protonated forms of styrylheterocyꢀ

cles, H—Het⁺—CH=CH—Ar X^–, which can be easily preꢀ

pared by the treatment of neutral styrylheterocycles with

strong mineral acids. We chose HClO₄as the mineral acid

because it has earlier been shown^20,23,24that perchlorate

anions are favorable for the solidꢀstate PCA reaction of

styryl dyes, including singleꢀcrystalꢀtoꢀsingleꢀcrystal reacꢀ

tions. The external shape and the electronic structure of

protonated styrylheterocycles are similar to those of the

corresponding styryl dyes. Hence, it would be expected

that the crystal packings of styrylheterocycles would be

similar to those of styryl dyes, i.e., styrylheterocycles would

primarily form stacks.

It should be noted that the stereoselective PCA reacꢀ

tions of protonated styrylheterocycles in solution were docꢀ

umented,^26—33including the reactions in the presence of

macrocyclic compounds (cucurbit[8]uril, γꢀcyclodextrin,

calix[n]arenes);^34—38however, the corresponding solidꢀ

state photoreactions are poorly known and were not sysꢀ

tematically studied.^26,39

In the present study, we report the synthesis and reꢀ

sults of the Xꢀray diffraction study of 4ꢀstyrylpyridine

hydroperchlorates 1b—9b and analyze their crystal packꢀ

ings. Single crystals were irradiated with visible light. The

crystals, which did not crack and were not transformed

into the amorphous state, were repeatedly studied by Xꢀray

diffraction. To confirm the occurrence of the solidꢀstate

PCA reaction and its stereochemical result, we also irraꢀ

diated polycrystalline films of compounds 1b—9b and anꢀ

alyzed the photoproducts by ¹H NMR spectroscopy.

The results are given in Table 1. It should be noted that,

although the films were prepared with the use of solutions

of the compounds in a MeCN—benzene mixture, the sigꢀ

nals of these solvents were observed in the ¹H NMR specꢀ

tra only in trace amounts. This indicates that the solvent

molecules were relatively rapidly evaporated from the films

upon heating with a closely placed incandescent lamp,

which was used as the light source.

Compounds 3b, 4b, and 6b proved to be insensitive to

light. By contrast, the irradiation of compounds 1b, 5b,

8b, and 9b resulted in the formation of centrosymmetric

rctt isomers of cyclobutane derivatives 10, 12, 13, and 14

(Scheme 2). The ¹H NMR spectra of the latter compounds

show characteristic^20,22,23signals of cyclobutane protons

at δ 5: two symmetrical doublets of doublets and the

AA´BB´ꢀtype spin system (see, for example, Fig. 2). This

is indicative of the existence of synꢀheadꢀtoꢀtail stacked

dimers in the solid state, which should precede the formaꢀ

tion of cyclobutanes with this stereochemistry. The rates

of the PCA reactions are substantially different. The photoꢀ

Table 1. The starting styrylpyridine (SP)ꢀtoꢀcyclobutane

(CB) derivative ratio and the degree of conversion (χ) in

polycrystalline films of compounds 1b—9b irradiated with

visible light

Comꢀ

pound

t/h^a

SP : CB^b

(mol/mol)

χ^b

(%)

1b

2b

20

50

20

140

50

70

20

80

20

140

20

1 : 10.2

0 : 1

1 : 0.02

1 : 0.57

1 : 0

0 : 1

1 : 0

1 : 0.04^c

1 : 0.06^c

1 : 0.66

1 : 4.2

1 : 8.6

0 : 1

95

100

5

53

0

100

0

3b

4b

5b

6b

7b

7

11

57

89

95

100

8b

80

200

20

9b

Results and Discussion

^aThe duration of irradiation.

^bBased on the ¹H NMR spectroscopic data.

Hydroperchlorates 1b—9b were synthesized by the reꢀ

action of the corresponding neutral (E)ꢀ4ꢀstyrylpyridines

with 70% perchloric acid. The resulting salts were characꢀ

^cThe reaction affords a mixture of two rctt isomers of cycloꢀ

butane, which corresponds to the PCA reaction proceedꢀ

ing in the synꢀheadꢀtoꢀtail and synꢀheadꢀtoꢀhead dimers,

in a ratio of ~2 : 1.

1

terized by UV and H NMR spectroscopy and elemental

Crystal packings of protonated styrylpyridines

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

1737

transformation proceeds most rapidly in styrylpyridines

1b, 5b, and 9b (almost quantitatively within 20 h), whereꢀ

as the complete conversion of crownꢀcontaining comꢀ

pound 8b was not achieved even within >200 h. In films of

nitro and dichloro derivatives 2b and 7b, the PCA reaction

proceeds slowly (the degree of conversion was 53 and 11%,

respectively, after 140 h) and with lower stereoselectivity;

in the case of 7b, a mixture of two rctt isomers of cyclobuꢀ

tane is formed, for which the cations in the starting dimers

should be arranged in a synꢀheadꢀtoꢀtail and synꢀheadꢀtoꢀ

head fashion.

ylsulfanyl groups in the benzene ring to form the cenꢀ

trosymmetric rctt isomers of cyclobutanes.²³This is assoꢀ

ciated with the motif b (see Fig. 1, the cations stacked in

a synꢀheadꢀtoꢀtail fashion) in the crystal packing and the

fact that these dyes show intense absorption in the visible

region, which facilitates the fast phototransformation unꢀ

der visible light irradiation. In the case of dye 1a containꢀ

ing the unsubstituted benzene ring and dyes 2a and 7a

containing electronꢀwithdrawing substituents, the PCA reꢀ

actions are much slower. The reactions of 2a and 7a proꢀ

ceed also with lower stereoselectivity and give mixtures of

two isomeric cyclobutane derivatives corresponding to the

cycloaddition in synꢀheadꢀtoꢀtail and synꢀheadꢀtoꢀhead

dimer pairs. These results correlate well with the shift of

the longꢀwavelength absorption maximum of these dyes

to the nearꢀUV region compared to the corresponding

characteristics of dyes 4a—6a, 8a, and 9a and, apparently,

with a larger diversity of the packing motifs in the crystals

of 2a and 7a. Like compound 3b, dye 3a containing the

dimethylamino group in the benzene ring was not involved

in the PCA reaction. Apparently, this is the common feaꢀ

ture of compounds having this structure due both to the

efficient conjugation between the highly electronꢀdonatꢀ

ing nitrogen atom of the substituent and the styryl chromoꢀ

phore and the packing mode of the molecules in the

crystals.^23,24

Scheme 2

The aboveꢀmentioned differences in the behavior of

protonated styrylpyridines 1b—9b and the corresponding

styryl dyes are difficult to explain without the considerꢀ

ation of the mutual orientation of the molecules in the

solid state. Hence, we studied the crystal packings of these

compounds.

Structural features of the formula units in the crystals of

compounds 1b—9b. Single crystals of compounds 1b—9b

were grown according to two procedures. In one method,

an excess of 70% perchloric acid was added to an acetoniꢀ

trile solution of the corresponding neutral 4ꢀstyrylpyridine

(or the previously synthesized individual compounds 1b—9b

were used), and the resulting solution was saturated with

a benzene or EtOAc vapor in the dark. Another method

was based on the crystallization of an equimolar mixture

of styrylpyridine and transition or heavy metal perchlorate

under the same conditions (see below). The structures of

the formula units in the crystals of compounds 1b—5b are

shown in Fig. 3.

i. hν, in the solid state

On the whole, the behavior of protonated styrylꢀ

pyridines 1b—9b substantially differs from that of the corꢀ

responding styryl dyes 1a—9a. The stereospecific PCA reꢀ

action proceeds relatively rapidly (the degree of converꢀ

sion was 85—92% within 10 h) in the case of dyes 4a—6a,

8a, and 9a containing electronꢀreleasing alkoxy or methꢀ

2 CHPy

2 CHAr

Compound 4b crystallizes in two modifications: without

solvent molecules or with the inclusion of benzene moleꢀ

cules if benzene is present in a mixture of the solvents. In

the structures of 1b, 3b•0.5C₆H₆, and 4b•0.5C₆H₆, the

molecular cations are disordered over two positions relatꢀ

ed to each other by the rotation by 180° about the long

axis. This disorder is a consequence of the temperatureꢀ

dependent solidꢀstate bicycleꢀpedal isomerization in the

crystals,^40,41when the ethylene group is rotated around

single bonds and the aromatic substituents are only slightꢀ

4.9

4.8

δ

Fig. 2. ¹H NMR spectrum (DMSOꢀd₆, 25 °C, the region of

cyclobutane protons) of the photoproduct (rctt isomer 12) preꢀ

pared as a polycrystalline film by irradiation of compound 5b

for 20 h.

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Kuz´mina et al.

O(11)

Cl(1)

O(1)

O(13)

Cl(1)

O(2)

O(12)

O(3)

O(14)

O(4)

O(1)

N(2)

N(1´)

N(1)

O(2)

1b

2b

N(3)

N(4)

N(5)

O(21)

Cl(2)

O(12)

O(11)

O(24)

O(14)

O(13)

O(23)

N(1)

O(22)

Cl(1)

N(2)

3b•0.5C₆H₆

O(14)

O(13)

O(14)

O(13)

O(12)

Cl(1)

O(11)

Cl(1)

O(11)

N(1)

O(1)

N(1)

N(2)

O(1)

4b

4b•0.5C₆H₆

O(11)

Cl(1)

O(14)

O(13)

O(12)

N(1)

S(1)

5b

Fig. 3. Structures of the formula units in the crystals of 1b (two s conformers), 2b, 3b•0.5C₆H₆(two independent molecules of 3b, one of them

as two s conformers, and the disordered benzene molecule), 4b, 4b•0.5C₆H₆(two s conformers), and 5b. The nonhydrogen atoms are shown

as displacement ellipsoids at the 50% probability level (except for the disordered benzene molecule in the structure of 3b•0.5C₆H₆).

Crystal packings of protonated styrylpyridines

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

1739

Cl(1)

Cl(4)

Cl(10)

Cl(9)

N(7)

Cl(6)

N(6)

Cl(5)

N(4)

Cl(3)

N(2)

Cl(11)

N(5)

Cl(7)

N(1)

Cl(8)

Cl(2)

N(3)

Cl(12)

N(8)

O(1W)

N(10´)

N(11)

N(9)

N(10)

O(2W)

S(6)

S(11)

S(3)

O(4W)

S(8)

S(10´)

S(7)

S(1)

S(10)

S(4)

S(9)

S(2)

S(5)

S(11´)

O(3W)

Fig. 4. Structures of the formula units in the crystal of 5b•0.76C₆H₆•0.14H₂O (11 independent molecules of 5b). The hydrogen bonds

are shown as dashed lines.

ly shifted in their own planes. The occupancy ratio for the

bicycleꢀpedal s conformers in the structures of 1b and

4b•0.5C₆H₆is 0.75 : 0.25 and 0.80 : 0.20, respectively. In

the structure of 3b•0.5C₆H₆, there are two independent

molecules 3b. One of them exhibits bicycleꢀpedal disorder

with the occupancy ratio of the s conformers equal to

0.73 : 0.27, whereas another molecule is ordered. The benzene

solvent molecule in this structure is disordered over three

positions with the occupancy ratio of 0.50 : 0.25 : 0.25 (the

displacement in the own plane). The perchlorate anions in

the structures of 3b•0.5C₆H₆, 4b, and 4b•0.5C₆H₆are

disordered (rotation about one of the Cl—O bonds).

The crystals of compound 5b were obtained as two

triclinic crystal modifications. In one of them (see Fig. 3),

solvent molecules are absent, whereas the composition

of another modification is described by the formula

5b•0.76C₆H₆•0.14H₂O. We unexpectedly obtained crysꢀ

tals of the latter modification from a solution containꢀ

ing methylsulfanylstyrylpyridine and Ni(ClO₄)₂in atꢀ

tempting to grow crystals of the corresponding coorꢀ

dination compound. In the triclinic unit cell of

5b•0.76C₆H₆•0.14H₂O, there are 11 independent styrylꢀ

pyridine molecules (Fig. 4). In some molecules, the cenꢀ

tral moiety is disordered, whereas the methylsulfanylꢀ

benzene moiety is disordered in other molecules, the latter

being alternatively replaced by benzene solvent molecules.

In the unit cell, there are also eight benzene solvent moleꢀ

cules with full occupancy. One of the styrylpyridine moleꢀ

cules occupies the position with half occupancy, and it is

alternatively replaced by several water molecules. One of

perchlorate anions is disordered over two closely spaced

positions.

The investigation of these structures by Xꢀray diffraction

is of great importance from the point of view of the further

development of supramolecular chemistry. However, it

should bear in mind that the low quality of Xꢀray diffracꢀ

tion data is an inherent property of these systems; the

quality of these data cannot be substantially improved.

The structures of the formula units in the crystals of

compound 6b are shown in Fig. 5. Compound 6b forms

O(12A)

O(11A)

Cl(1)

O(12)

O(11)

N(1)

O(1)

N(1´)

O(2)

O(22)

O(21A)

Cl(2)

O(22A)

O(21)

6b^m

O(2)

N(1)

These Xꢀray diffraction data were collected from

a weakly diffracting crystal, which has a very poor quality

due to a too large fraction of disorder elements and conꢀ

tains a huge number of independent formula units. Unꢀ

doubtedly, the structures of these imperfect crystals more

precisely describe supermolecules selfꢀorganized in soluꢀ

tion compared to the ideal crystal structures. These superꢀ

molecules have a structure (order), but the latter is less

well organized and more loose than crystal structures.⁴²

O(1)

Cl(1)

6b^o

Fig. 5. Structures of the formula units in the crystals of 6b^m(two s

conformers) and 6b^o. In the structure of 6b^m, the atoms of the

perchlorate anions labeled with A are related to the unlabeled

atoms by symmetry operations.

1740

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Kuz´mina et al.

two crystal modifications, viz., monoclinic (6b^m) and

orthorhombic (6b^o). The monoclinic modification was

found in attempting to cocrystallize neutral dimethoxyꢀ

styrylpyridine with the salts Zn(ClO₄)₂, Pb(ClO₄)₂, or

Cr(ClO₄)₃. Evidently, transition and heavy metal perchlorꢀ

ates are relatively easily hydrolyzed in the course of the

crystal growth, and styrylpyridine is protonated by perꢀ

chloric acid that is eliminated. Apparently, the presence

of the aboveꢀmentioned salts facilitates the nucleation and

growth of only the monoclinic modification, although the

salts are not included in the growing crystal as compoꢀ

nents. In the crystals of 6b^m, the cation is distributed beꢀ

tween two positions corresponding to the bicycleꢀpedal

disorder with the occupancy ratio of 0.75 : 0.25. Two perꢀ

chlorate anions occupy special positions on twofold axes.

In the orthorhombic modification of 6b^o, the bicycleꢀpedꢀ

al disorder also apparently takes place, as evidenced by the

elongated thermal ellipsoids of the atoms as potential parꢀ

ticipants of this process, the relatively high R factor, and

the presence of relatively high residual electron density

peaks in difference Fourier maps in the region of the ethylꢀ

ene bond. However, this fact cannot be conclusively esꢀ

tablished because of the insufficiently high quality of the

experimental data and the low content of the second s

conformer. It should also be noted that this crystal is

a racemic twin.

benzene solvent molecules occupying sites with half occuꢀ

pancy, and two water molecules with occupancies of 0.125,

which are substantially disordered in the vicinity of centers

of symmetry. Independent molecules 8b form a pseudoꢀ

centrosymmetric dimers. It is interesting that only one

molecule in the dimer shows bicycleꢀpedal disorder in the

form of two s conformers with almost equal occupancies

(0.53 : 0.47). The position of another molecule is rigidly fixed.

This is indicative of the difference in the crystal environꢀ

ment of the independent molecules. Thus, the environꢀ

ment of the "upper" molecule is looser because it allows it

to be slightly shifted in the course of the dynamic bicycleꢀ

pedal isomerization, whereas the crystal environment of

the "lower" molecule fixes it in the only possible position.

In this crystal, both independent perchlorate anions

are also disordered (top and pendulum models).

Finally, two types of crystals were obtained for comꢀ

pound 9b. In one of them, 9b crystallizes as a solvate with

acetonitrile and benzene molecules. In another type of

crystals, 9b crystallizes as a complex with ammonium perꢀ

chlorate.

In the structure of 9b•MeCN•0.5C₆H₆•H₂O (Fig. 8),

a part of the macrocycle distant from the benzene ring is

disordered over two positions with the occupancy ratio of

0.68 : 0.32. The organic solvent molecules are also subꢀ

stantially disordered due, apparently, to the relative "looseꢀ

ness" of the crystal packing, as indirectly evidenced by the

rapid degradation of the single crystals in air due to erosion.

The water molecule is encapsulated in the cavity of

the 18ꢀmembered macrocycle and forms hydrogen

bonds with the oxygen atoms of the macrocycle: the

O(1W)H...O(1)/O(6) bifurcated hydrogen bond (H...O,

2.20 and 2.37 Å; the angles at the H atom, 155 and 136°)

and the O(1W)H...O(4) single hydrogen bond characterꢀ

ized by the parameters 2.11 Å and 173°.

The crystal of 7b•0.5C₆H₆contains eight molecules

of the dichlorostyrylpyridinium salt and four benzene

solvent molecules per asymmetric unit (Fig. 6). Like

5b•0.76C₆H₆•0.14H₂O, this structure is an example of

a "loose" supramolecular assembly with a large number of

structural units.

In the crystal of protonated 15ꢀcrownꢀ5ꢀcontaining

styrylpyridine 8b (Fig. 7), there are two crystallographiꢀ

cally independent molecules of the major component, two

Cl(1)

Cl(1A)

O(13)

O(81)

O(84)

N(8)

O(12)

N(1)

Cl(2A)

Cl(8)

O(11)

O(82)

Cl(1H)

Cl(1B)

O(14)

N(2)

O(83)

O(74)

O(24)

N(7)

Cl(2H)

O(23)

O(71)

O(72)

Cl(2G)

Cl(2)

Cl(2B)

Cl(1C)

Cl(2C)

O(73)

O(61)

O(21)

O(31)

O(22)

Cl(2D)

Cl(7)

O(63)

N(6)

O(34)

O(33)

N(3)

Cl(3)

Cl(1G)

Cl(6)

Cl(2F)

Cl(1D)

O(64)

O(51)

Cl(5)

N(5)

O(62)

O(44)

O(32)

O(43)

Cl(1F)

Cl(1E)

O(53)

O(54)

Cl(4)

N(4)

O(52)

O(41)

Cl(2E)

O(42)

7b•0.5C₆H₆

Fig. 6. Structures of the formula units in the crystal of 7b•0.5C₆H₆(eight independent molecules of 7b). The nonhydrogen atoms are

shown as displacement ellipsoids at the 50% probability level. The hydrogen bonds are shown as dashed lines.

Crystal packings of protonated styrylpyridines

O(6)

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

1741

O(2)

N(2)

O(10)

O(7)

N(3)

O(3)

O(12)

O(14)

Cl(1)

O(1)

O(5)

N(1)

O(8)

O(16)

O(13)

O(9)

O(4)

O(11)

Cl(1´)

O(15)

O(21)

O(22)

O(27)

Cl(2)

O(26)

O(2W)

O(1W)

O(24)

O(25)

O(23)

8b•0.5C₆H₆•0.125H₂O

Fig. 7. Structures of the formula units in the crystal of 8b•0.5C₆H₆•0.125H₂O (two independent molecules of 8b, one of them as two s

conformers). The nonhydrogen atoms are shown as displacement ellipsoids at the 30% probability level. The hydrogen bonds are

shown as dashed lines.

In the structure of 9b•NH₄ClO₄, the inorganic salt

appears in the crystalline substance due, apparently, to

the relatively fast hydrolysis of acetonitrile in the presꢀ

Crystal packings of protonated styrylpyridines. The proꢀ

jection of the crystal packing of 1b along the b axis of the

crystal is shown in Fig. 9, a. This compound has the packꢀ

ing motif e (see Fig. 1) similar to one of the three packings

found^23,24in the crystalline phases of related styryl dye 1a.

In the dimers, the molecules are related by centers of symꢀ

metry due to which they are arranged in a headꢀtoꢀtail

fashion. In the dimer, the conjugated systems are projectꢀ

ed onto each other with the distances d₁(see Scheme 1)

between the ethylene carbon atoms equal to 3.70 and

3.69 Å for the major and minor s conformers, respectively,

+

ence of an excess of perchloric acid. The NH₄ion

is encapsulated in the cavity of the 18ꢀcrownꢀ6 moiety

and forms hydrogen bonds with the oxygen atoms. The

lengths of the N(2)H...O hydrogen bonds are in the range

of 1.78—2.40 Å, and the angles at the H atoms are in the

range of 130—162°. Two units of the macrocycle are disꢀ

ordered over two positions with the occupancy ratio

of 0.63 : 0.37.

N(2S)

N(1S)

O(22)

O(23)

Cl(2)

O(5)

O(11)

O(4´)

O(21)

O(24)

O(4)

O(3´)

O(13)

O(12)

O(2)

Cl(1)

O(3)

O(1W)

O(14)

N(1)

O(1)

O(6)

O(2´)

O(1)

O(13)

Cl(1)

O(2)

O(3)

N(2)

O(4)

N(1)

O(11)

O(14)

9b•NH₄ClO₄

O(12)

O(5)

9b•MeCN•0.5C₆H₆•H₂O

Fig. 8. Structures of the formula units in the crystals of 9b•MeCN•0.5C₆H₆•H₂O (the disordered moiety of the macrocycle and

solvent molecules) and 9b•NH₄ClO₄(the disordered moiety of the macrocycle). The nonhydrogen atoms are shown as displacement

ellipsoids at the 50% probability level. The hydrogen bonds are shown as dashed lines.

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Kuz´mina et al.

whereas the corresponding distances between the adjacent

dimers, d₂, are 5.56 and 5.51 Å in the absence of the

mutual overlap (Fig. 9, b). This geometry indicates that

the PCA reaction can proceed in this crystal to form

the centrosymmetric rctt isomer of the cyclobutane derivꢀ

ative, which correlates well with the relatively high rate

of this reaction in a polycrystalline film of compound 1b

(see Table 1).

in the probability of the PCA reaction for the following

reason. At each instant of time, four different mutual arꢀ

rangements of the molecules in dimers can take place in

the crystals.

The repeated Xꢀray diffraction study of a single crystal

irradiated with visible light for nine days was not perꢀ

formed because of a considerable loss in the quality of the

crystal, which was covered with cracks, became turbid,

and began to disintegrate. Evidently, the degradation of

the single crystal is caused by the PCA reaction that proꢀ

ceeds in the single crystal. It is known^20,22,24,25that the

presence of a soft mobile shell around the dimer preorgaꢀ

nized for the PCA reaction is essential for the single crysꢀ

tal to remain intact in the course of this reaction. In the

case of styryl dyes 1a—9a, this shell is created together by

translationally and rotationally mobile perchlorate anions

and solvent aromatic molecules, as well as by the conforꢀ

mationally flexible moieties of the dyes. In the crystals of

1b, which contain no solvent molecules and conformaꢀ

tionally flexible moieties, the dimers are surrounded only

Only two of these arrangements (1 and 2) meet the

conditions necessary for the reaction to occur, because

they contain antiparallel ethylene groups, whereas in the

two other cases (3 and 4), these groups are in a staggered

arrangement.

The crystal packing of protonated nitrostyrylpyridine

2b is shown in two projections in Fig. 10. It is similar to

the crystal packing of related styryl dye 2a.^23,24Both these

structures consist of centrosymmetric stacks arranged in

a synꢀheadꢀtoꢀtail fashion.

In the crystal of 2b, the stacks are composed of dimers

with a short distance between the ethylene groups in the

dimers (3.77 Å; in dye 2a, d₁= 3.71 Å) and a substantially

longer distance between the ethylene groups of the adjaꢀ

cent dimers in the stack (4.69 Å; in dye 2a, d₂= 4.59 Å),

which corresponds to the conditions of the PCA reaction.

In the dye, this reaction proceeds in the light quite rapidly.

The process became noticeable already after 30 min since

the crystals were cracked and turned turbid, which was

accompanied by the degradation of the single crystal. The

–

by ClO₄ions, whose mobility is apparently insufficient

for the formation of a soft shell. In addition, in this case

the shell created by the anions around the dimers has high

rigidity due to the formation of hydrogen bonds between

the anions and the N⁺—H groups of the cations. The

presence of these hydrogen bonds in the crystal results

in the formation of tetramers consisting of two cations

and two anions (see Fig. 9). The O...N/O...H distances

between the cations and anions are 3.00/2.19, 3.15/2.53

and 2.88/2.03, 3.31/2.82 Å for the major and minor s

conformers, respectively.

It should be noted that the dynamic process of the

bicycleꢀpedal isomerization inevitably leads to a decrease

a

b

a

b

0

c

Fig. 9. Projections of the crystal packing of 1b along the b axis (a) and a fragment of the sandwichꢀherringbone motif (b) in this packing.

Only the major s conformers of 1b are shown for simplicity. The hydrogen bonds are shown as dashed lines.

Crystal packings of protonated styrylpyridines

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

a

1743

b

0

c

a

c

0

b

Fig. 10. Projections of the crystal packing of 2b along the a (a) and b axes (b).

degradation of the single crystals of dye 2a upon their

irradiation occurs due to the absence of the soft mobile

shell around the dimers, whose role is to provide the reꢀ

duction of the steric strain in the crystal in the course of

the PCA reaction. The crystals of 2b exhibit high resisꢀ

tance to light and show no visual evidence of the degradaꢀ

tion upon irradiation for one week, which correlates with

the low rate of the photoreaction in a polycrystalline film

of this compound (see Table 1). This is due to hydrogen

bonds with the participation of the anions, N⁺—H, and

the nitro groups of the cations (Fig. 11).

The N⁺—H group of the cation is involved simultaꢀ

neously in two hydrogen bonds, viz., the bonds with

the perchlorate oxygen atom (the N(1)...O(11) and

H(1B)...O(11) distances are 2.86 and 2.11 Å, respectively)

and the oxygen atom of the nitro group of the adjacent

molecule (the N(1)...O(1A) and H(1B)...O(1A) distances

are 3.03 and 2.59 Å, respectively). This hydrogen bond

network results in a quite rigid framework preventing the

atoms from shifting in the course of the PCA reaction in

the crystal. However, at the ninth day of irradiation, first

evidence of the crystal degradation, such as the surface

cracking and turbidity, were observed. In this step, the

repeated singleꢀcrystal Xꢀray diffraction study was perꢀ

formed, which revealed the simultaneous presence of the

starting compound 2b and the centrosymmetric rctt isoꢀ

mer of cyclobutane 11 that was formed in the course of the

PCA reaction (Fig. 12).

As expected, the PCA reaction proceeds in dimers with

a relatively short distance between the ethylene groups

and is accompanied by a decrease in the unit cell volume

by 1%. The styrylpyridine/cyclobutane molar ratio in 2b/11

was 0.60 : 0.40 (the degree of conversion was 57%). The

anion experiences strong rotational motion. The subseꢀ

quent irradiation of the single crystal led to a considerable

loss in its quality, which made it impossible to follow the

accumulation of the photoreaction product. Therefore, in

the case under consideration, the single crystal finally unꢀ

derwent degradation; however, due to the low rate of the

PCA reaction, we succeeded in detecting the presence of

the cyclobutane derivative by Xꢀray diffraction.

The crystals of 3b•0.5C₆H₆(Fig. 13, a) are composed

of translationally related stacks of cations arranged in

a headꢀtoꢀhead fashion, the independent cations forming

Cl(1)

O(13)

O(12)

O(14)

O(11)

N(1)

O(1)

N(2)

H(1B)

N(1A)

O(1A)

N(2A)

O(2)

O(2A)

Fig. 11. Hydrogen bond network in the crystal structure of 2b.

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Kuz´mina et al.

O(2´)

N(2´)

O(2)

N(1)

O(17)

O(13)

O(11)

N(2)

Cl(1)

N(1´)

O(18)

Cl(1)

O(1´)

O(1)

O(16)

O(1´)

O(14)

O(15)

O(12)

O(1A)

N(2´A)

O(1´A)

N(1´A)

O(2´A)

N(2A)

N(1A)

O(2A)

Fig. 12. Structural units in the crystal of 2b/11 (irradiation for 9 days) showing the simultaneous presence of the starting styrylpyridine

and the rctt isomer of cyclobutane. The atoms labeled with A are related to the unlabeled atoms by symmetry operations. The

nonhydrogen atoms are shown as displacement ellipsoids at the 40% probability level. The hydrogen bonds are shown as dashed lines.

individual stacks. The disordered benzene solvent moleꢀ

cules are in the immediate vicinity of the stacks formed by

the disordered cations, in which the bicycleꢀpedal isomerꢀ

ization can take place. Evidently, this is indicative of the

dynamic character of the disorder of the solvent moleꢀ

cules. In addition, the disordered anions form hydrogen

bonds with the N⁺—H groups of the disordered cations,

which is also indicative of the dynamic character of disꢀ

order of these structural units. Apparently, the whole

sequence of dynamic processes has the common origin,

viz., the dynamic process of the bicycleꢀpedal isomerꢀ

ization.

In the crystals of 3b•0.5C₆H₆, both perchlorate anions

are involved in hydrogen bonds. The system of hydrogen

bonds, by which the ordered cations and anions are linked

to each other, is similar to that observed in the crystals of 1b

(Fig. 13, b). The O(11D)...N(1C) and O(11D)...H(11C)

distances are 3.33 and 2.85 Å, respectively; the

O(11C)...N(1C) and O(11C)...H(1C) distances are 2.90

and 2.10 Å, respectively. The disordered cations and anꢀ

ions are also linked together by hydrogen bonds to form

tetramers. The O...N and O...H distances for two s conꢀ

formers are in the ranges of 2.88—3.41 and 2.05—2.87 Å,

respectively.

is impossible because of the strong electronꢀdonating propꢀ

erties of the NMe₂substituent. Nevertheless, the structurꢀ

al studies of these compounds contribute to a deeper

knowledge on the possible types of crystal packings. Thereꢀ

fore, the PCA reaction in the crystal of 3b•0.5C₆H₆is

impossible not only because of the chemical nature of the

compound but also because of the formal crystallographic

reasons.

Based on the fact that the crystal packings of protonatꢀ

ed styrylpyridines 1b—3b and related dyes 1a—3a are pairꢀ

wise similar, the same situation would be expected for

compounds 4b and 5b containing the methoxy or methylꢀ

sulfanyl group, respectively, in the benzene ring. Styryl

dyes 4a and 5a crystallize in two pairs of isostructural

crystal modifications.^23,24One of these modifications conꢀ

sists of the centrosymmetrically related stacks formed by

cations arranged in a headꢀtoꢀtail fashion, whereas anothꢀ

er modification is composed of translationally related

headꢀtoꢀhead stacks. We succeeded in preparing two crysꢀ

tal modifications for both compounds 4b and 5b.

In the crystal packings of 4b and 4b•0.5C₆H₆(Fig. 14),

there are translationally related stacks of cations. In the

structure of 4b•0.5C₆H₆, these stacks form layers alterꢀ

nating with layers formed by anions and benzene solvent

molecules. The geometry of the hydrogen bond between the

cations and anions is similar to that found in the structures

of 1b and 3b•0.5C₆H₆; the corresponding O...N and O...H

distances are in the ranges of 2.91—3.23 and 2.05—2.63 Å,

respectively, The headꢀtoꢀhead packing motif, like that in

the structure of 3b•0.5C₆H₆, is associated with a substanꢀ

tial shift of the adjacent cations of 4b in the stacks in

parallel planes. In the crystals of 4b and 4b•0.5C₆H₆, the

In this case, it is evident that the packing motif of

protonated styrylpyridine 3b is similar to that of related

dye 3a.^23,24The headꢀtoꢀhead stacks found in 3b•0.5C₆H₆

are unpromising for the PCA reaction in the crystal. In

these stacks, adjacent cations are strongly shifted with

respect to each other (see Fig. 13, b), so that the distance

between the adjacent ethylene groups is 6.87 Å. Earlier, it

has been noted that the PCA reaction in compounds 3a,b

Crystal packings of protonated styrylpyridines

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

1745

a

c

0

a

c

b

Cl(1D)

N(1D)

N(2C)

O(11D)

N(2B)

N(2A)

O(11C)

H(1C)

N(1C)

N(1B)

N(1A)

Cl(1C)

Cl(1B)

Cl(1A)

Fig. 13. Projection of the crystal packing of 3b•0.5C₆H₆along the a axis (a) and a fragment of the stack formed by the ordered cations

projected onto the mean plane of the cation labeled with A (b). The hydrogen bonds are shown as dashed lines.

distances between the ethylene groups are 8.82 and 6.79 Å,

respectively, which indicates that the solidꢀstate PCA reꢀ

action cannot proceed. Evidently, similar types of the moꢀ

lecular packing take place in a polycrystalline film of comꢀ

pound 4b, which accounts for the absence of the [2+2]

cycloaddition products after the longꢀterm irradiation

(see Table 1).

The crystal packing of 5b consists of centrosymmetriꢀ

cally related stacks extended along the a axis of the crysꢀ

tal, with cations being arranged in a synꢀheadꢀtoꢀtail fashꢀ

ion (Fig. 15). These stacks are divided into dimers, like

those in the crystal of 2b. The distance d₁in the dimer is

3.79 Å, and the corresponding distance d₂between the

adjacent dimers is 4.55 Å, i.e., the conditions necessary

for the solidꢀstate PCA reaction are met.

This crystal also consists of tetramers formed by two

cations and two anions linked together by hydrogen bonds

(see Fig. 15). The O(11A)...N(1B), O(11A)...HN(1B) and

O(11B)...N(1B), O(11B)...HN(1B) distances are 3.07,

2.24 and 3.04, 2.20 Å, respectively, and the angles at the

H atoms are 134 and 136°.

Although the similar stacking motif is observed in the

crystal packing of one modification of dye 5a, the crystal

packing of compound 5b has substantial differences,

among which the formation of secondary bonds between

adjacent sulfur atoms is one of the most important feature.

The S...S distance is 3.386(5) Å, the S→S vector lies

almost on the extension of one of the bonds formed by the

sulfur atom, and the S...S—C_Arangle is 162.2(3)°. The

observed geometry corresponds to the nꢀσ* secondary bond

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Kuz´mina et al.

a

0

a

c

b

0

c

a

b

Fig. 14. Projections of the crystal packings of 4b (a) and 4b•0.5C₆H₆(b) along the a axis. Only the major s conformers of the cations in

the structure of 4b•0.5C₆H₆are shown for simplicity. The hydrogen bonds are shown as dashed lines.

with the participation of the unoccupied σ* orbital of the

S—C_Arbond of one sulfur atom and the lone pair at the

sp²ꢀhybrid orbital of another sulfur atom. This type of

interactions is often observed in organic compounds of

divalent sulfur. We analyzed the intermolecular S...S conꢀ

tacts based on the data deposited in the Cambridge Crysꢀ

tallographic Data Centre (CCDC, version 5.30).⁴³Figure 16

shows the histogram of these contacts. The shorter the

d(S...S) distance, the more pronounced the directionality

of this interaction. At shorter d(S...S) distances, the conꢀ

figuration of the bonds at the sulfur atom has a more proꢀ

nounced Tꢀshaped geometry. The distance determined in

the present study is approximately in the middle of the

range characteristic of S...S interactions.

Upon irradiation of crystals of compound 5b, they reꢀ

main intact during a certain period of time, but then they

start to crack and undergo rapid degradation. Attempts to

detect the intermediate formation of the photoproduct in

the crystal by Xꢀray diffraction failed; however, according

to the ¹H NMR spectroscopic data, the irradiation of

a polycrystalline film of compound 5b leads to a relatively

fast conversion into the corresponding rctt isomer of cycloꢀ

butane (see above). This is indicative of the similar packꢀ

ing motif of 5b in the film.

The crystal packing of 5b•0.76C₆H₆•0.14H₂O is also

similar to one modification of dye 5a. In the unit cell, all

11 independent molecules of protonated styrylpyridine

form very loose and poorly ordered headꢀtoꢀhead stacks

(see Fig. 4). In these stacks, the ethylene bonds of the

adjacent molecules have both parallel and staggered muꢀ

tual orientations. The distances between these molecules

are 4.64—6.76 Å, which is unfavorable for the PCA reacꢀ

tion.

The crystal packing of 6b^m(Fig. 17, a) consists of

alternating layers of anions and cations arranged both in

a headꢀtoꢀtail and headꢀtoꢀhead fashion. The aromatic

moieties are stacked onto each other in three different

ways: by pairs of dimethoxybenzene moieties, by pairs of

pyridine moieties, and by a combination of dimethoxyꢀ

benzene/pyridine moieties. The ethylene groups are not

Crystal packings of protonated styrylpyridines

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

1747

b

0

S(1A)

S(1E)

N(1E)

N(1A)

O(11A)

N(1B)

S(1 F)

S(1B)

O(11B)

N(1F)

c

S(1 C)

N(1G)

a

N(1C)

N(1D)

S(1G)

N(1H)

S(1H)

S(1D)

Fig. 15. The crystal packing of 5b. The hydrogen bonds and the S...S contacts are shown as dashed lines.

involved in the πꢀoverlap with each other; their mutual

shift is 6.09—7.07 Å, which is unsuitable for the PCA

reaction. The mutual arrangement of the cations in the

layer apparently corresponds to the optimal set of weak

interactions. These are, on the one hand, stacking interacꢀ

tions between the aromatic moieties and, on the other

hand, hydrogen bonds. The major s conformer forms a

N⁺—H...O hydrogen bond with one of the methoxy groups

of the adjacent cation related to the original cation by the

cꢀaxis translation. The N(1)...O(2A) and H(1N)...O(2A)

distances are 2.98 and 2.11 Å, respectively; the angle at

the H(1N) atom is 167°; these hydrogen bonds link the

cations together to form chains running along the с axis

(Fig. 17, b). The minor s conformer forms a weak hydroꢀ

gen bond with the Cl(2)O₄^–anion. The N(1´)...O(21) and

H(1´N)...O(21) distances are 3.02 and 2.35 Å, respecꢀ

tively; the angle at the H(1´N) atom is 133°.

The crystals of 6b^oconsist of translationally related

stacks of cations arranged in a headꢀtoꢀhead fashion (Fig. 18).

This packing is unsuitable for the PCA reaction, because

the distance between the ethylene groups of adjacent catꢀ

ions is too large (≥4.99 Å). Two symmetryꢀrelated perꢀ

chlorate anions form the N⁺—H...^–OClO₃hydrogen bonds

with the cation; the N...O and H...O distances are 2.91

and 2.06 Å, respectively; the angle at the H atom is 162°.

The crystal packings of 6b^mand 6b^ohave no analogies

with the packing of related styryl dye 6a, whose crystals

are composed of centrosymmetrically related stacks of catꢀ

ions arranged in a headꢀtoꢀtail fashion.^23,24This has a

crucial effect on the ability of compounds 6a and 6b to

undergo the solidꢀstate PCA reaction. In the case of a

polycrystalline film of dye 6a, the phototransformation

proceeds rapidly and quantitatively to form the rctt isomer

of the cyclobutane derivative, whereas a film of compound

6b proved to be insensitive to light (see Table 1).

Number of entries N

800

Compound 7b crystallizes as a benzene solvate

(7b•0.5C₆H₆) with eight crystallographically independent

formula units. In the crystal, independent cations are

arranged in two types of lowꢀsymmetry headꢀtoꢀhead

stacks (see Fig. 6) similar to those found in the crystals of

3b•0.5C₆H₆, 4b•0.5C₆H₆, 5b•0.76C₆H₆•0.14H₂O, and

6b^o. The distances between the atoms of the ethylene

groups of adjacent cations are very large (4.63—6.54 Å),

which excludes the PCA reaction in these crystals and

accounts for their resistance to light. The hydrogen bond

network in the crystal of 7b•0.5C₆H₆with the particiꢀ

600

400

200

pation of the N⁺—H groups and ClO₄ions is similar to

–

2.8

3.0

3.2

3.4 d(S...S)/Å

the aboveꢀconsidered cases: the cations are involved in

single and bifurcated hydrogen bonds with either one or

two anions.

Fig. 16. Histogram of S...S contacts in organic sulfur(II) comꢀ

pounds extracted from the CCDC.

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Kuz´mina et al.

a

0

c

a

b

O(1A)

O(1)

O(2)

O(2A)

N(1)

N(1A)

H(1N)

H(1´N)

N(1´)

O(22A)

N(1´A)

O(21)

Cl(2)

O(22)

O(21A)

Fig. 17. One layer of the cations in the crystal packing of 6b^m(a, only the major s conformers are shown) and the hydrogen bond

network (b). The hydrogen bonds are shown as dashed lines.

The longꢀterm irradiation of a polycrystalline film of

compound 7b led to a very slow accumulation of two isoꢀ

mers of the cyclobutane derivative (see Table 1), which

indicates that the translation motif prevails in the molecuꢀ

lar packing of this compound. In the crystals of dye 7a

related to this styrylpyridine, the cations are arranged in a

headꢀtoꢀtail fashion to form centrosymmetric stacks.²⁴In

these crystals, the solidꢀstate PCA reaction shows the same

stereoselectivity but proceeds much more rapidly and is

accompanied by the singleꢀcrystal degradation.

The crystal packing of compound 8b is shown in Fig. 19.

The presence of the 15ꢀcrownꢀ5 ether moiety in the

styrylpyridine molecule leads to the formation of dimers,

in which the cations are linked together by single or bifurꢀ

cated N⁺—H...O(macrocycle) hydrogen bonds. This is

possible due to the conformational flexibility of the polyꢀ

ether ring allowing the ring to be bent in such a way that

the oxygen atom of the macrocycle most distant from the

benzene ring is in close proximity to the N⁺—H group

of the second molecule of the dimer. The hydrogen

bonds (see Fig. 19, b) have the following parameters:

N(1B)H...O(8B), N(2B)H...O(2B), N(2B)H...O(3B), and

N(3B)H...O(3B), 1.92, 2.18, 2.15, and 1.90 Å, respectively;

the angles at the H atoms are 167, 131, 149, and 156°.

The dimers are arranged in stacks along the c axis of

the crystal. These stacks form layers, in which the conꢀ

tacts between adjacent stacks occur via the crown ether

moieties. These layers are separated from each other by

loose interlayers formed by the disordered anions and solꢀ

vent molecules (see Fig. 19, a). The high degree of disorꢀ

der of most of the components in the unit cell leads

to a substantial loss of the quality of the crystal of

8b•0.5C₆H₆•0.125H₂O. However, this results in the higher

stability of the crystal in the course of the possible PCA

Crystal packings of protonated styrylpyridines

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

1749

c

a

0

b

Fig. 18. Projection of the crystal packing of 6b^oalong the b axis. The hydrogen bonds are shown as dashed lines.

reaction, because such a loose shell around the dimer pairs

can reduce internal strains resulting from displacements

of atoms in going from the dimeric structure to cycloꢀ

butane. It should be noted that the packing motif in this

crystal is similar to that in the crystals of dye 9a, where we

have observed²⁰the PCA reaction without singleꢀcrystal

degradation.

Since each dimer consists of the ordered and disorꢀ

dered independent cations of 8b, the ethylene bonds in

these pairs are located one above another either in a stagꢀ

gered or almost antiparallel fashion (the twisting angle is

only 17°). The latter mode of the mutual arrangement

of the molecules meets the conditions of the solidꢀstate

PCA reaction, because the distances d₁are in the range of

3.45—3.62 Å. This is why the crystal was subjected to

longꢀterm irradiation, which was interrupted each second

day for a short period of time to check the unit cell paramꢀ

eters, whose change would be indicative of the PCA reacꢀ

tion. However, the visual evidence of the impairment of

the quality of the single crystal, such as the loss of the

color, the opacity, and the surface cracking, as well as

a slight change in the unit cell parameters, appeared only

at the 11th day of irradiation of the single crystal. The

Xꢀray diffraction study revealed the formation of the cycloꢀ

butane derivative along with the existence of the startꢀ

ing styrylpyridine in one and the same crystal of

(8b/13)•C₆H₆•0.25H₂O. The reflectivity of the single

crystal noticeably deteriorated due to the appearance of

numerous disordering elements. Figure 20 shows the main

unit cell components of the irradiated crystal. It can be

seen that the rctt isomer of cyclobutane is produced by the

cycloaddition of cations of 8b in syn orientations. The

occupancy ratio of two positions for the s conformers of

the disordered cation (0.60 : 0.40) changes only slightly

compared with the starting crystal, whereas the styrylpyriꢀ

dine/cyclobutane molar ratio is 0.73 : 0.27 (the degree of

conversion is 42%). This fact confirms the dynamic charꢀ

acter of the disorder with the result that the fraction of the

minor s conformer of the starting compound consumed in

the course of the PCA reaction is constantly replenished

due to the bicycleꢀpedal isomerization. Once the PCA

reaction partially proceeded, the unit cell volume decreased

by only 0.5% compared with the initial value, although

certain unit cell parameters substantially changed.

It is noteworthy that the further irradiation of the sinꢀ

gle crystal of (8b/13)•C₆H₆•0.25H₂O during a few hours

(the repeated experiment was performed 20 h after the

beginning of the further irradiation of the crystal of

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Kuz´mina et al.

a

c

0

b

0

O(3A)

O(2A)

b

N(3A)

a

N(2A)

b

O(8B)

N(1B)

O(8A)

N(1A)

c

N(2B)

O(3B)

O(2B)

N(3B)

Fig. 19. Projections of the crystal packing of 8b•0.5C₆H₆•0.125H₂O along the c (a) and a axes (b). The hydrogen bonds are shown as

dashed lines.

Crystal packings of protonated styrylpyridines

O(6)

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

1751

N(3)

O(2)

N(2)

O(7)

O(10)

N(4)

O(3)

N(1)

O(1)

O(8)

O(4)

O(5)

O(9)

Fig. 20. Structures of the main components in the crystal structure of (8b/13)•C₆H₆•0.25H₂O (irradiation for 11 days) showing the

simultaneous presence of the starting styrylpyridine and the rctt isomer of cyclobutane. The hydrogen bonds are shown as dashed lines.

(8b/13)•C₆H₆•0.25H₂O) led to the complete transforꢀ

mation of the starting compound into the corresponding

rctt isomer of cyclobutane derivative 13•C₆H₆•0.25H₂O.

A deep crack that formed in the single crystal resulted in

the partial loss of its volume during the mounting of the

crystal in a diffractometer. The processing of the experiꢀ

mental data gave the best result for the doubled unit cell

compared to the starting crystal, which is indicative of the

lowering of the symmetry. This is manifested in the disapꢀ

pearance of the centers of symmetry that relate the cations

in the stacks. Thus, the cations in the stacks are related

not strictly by a center of symmetry but by a pseudoꢀ

center of symmetry resulting in the presence of two crysꢀ

tallographically independent stacks. Figure 21 shows the

structure of 13•C₆H₆•0.25H₂O.

Each stack consists of unsymmetrical rcttꢀcyclobutane

molecules. The conformations of the independent cycloꢀ

butanes are substantially different, particularly, in the

region of the crown ether moieties, one of which is disorꢀ

dered, and the pyridine moieties (Fig. 22). The latter form

O(5)

O(1)

N(1)

O(9)

O(8)

O(4*)

O(4)

O(2)

O(7)

Cl(2)

O(10)

O(3)

O(1W)

O(6)

N(2)

Cl(3)

Cl(1)

O(1´)

N(3)

O(5´)

O(8´)

O(6´)

O(2´)

O(7´)

Cl(5)

O(4´)

O(9´)

N(4)

Cl(4)

O(3´)

O(10´)

Fig. 21. Structure of 13•C₆H₆•0.25H₂O (irradiation for 12 days). The nonhydrogen atoms are shown as displacement ellipsoids at the

30% probability level. Most of the hydrogen atoms are not shown. The hydrogen bonds are shown as dashed lines.

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Kuz´mina et al.

N(1)

N(4)

N(2)

N(3)

Fig. 22. Superposition of the independent cyclobutane dications in the structure of 13•C₆H₆•0.25H₂O using the cyclobutane rings and

the nearest carbon atoms.

hydrogen bonds with either one of the oxygen atoms of

the macrocycle or with the water solvent molecule

(N⁺(1)H...O(8), N⁺(2)H...O(1W), N⁺(3)H...O(8´), and

N⁺(4)H...O(3´), 1.88, 2.04, 1.90, and 1.88 Å, respectiveꢀ

ly, the angles at the H atoms are 176, 140, 163, and 173°,

respectively).

The independent cyclobutanes are rctt isomers, and

their fourꢀmembered rings are nonplanar: the torsion anꢀ

gles in the rings vary from –4 to 5° and from –15 to 14° in

two independent dications. This distinguishes cyclobutanes

13 from the earlier studied^{20—22,24,25,44}centrosymmetric

rctt isomers of cyclobutanes, which have been syntheꢀ

sized by PCA in solution and crystals of styryl dyes and

neutral 4ꢀstyrylquinoline, where the cyclobutane rings are

ideally planar.

Apparently, due to the lowering of the overall crystal

symmetry, the new structure is better adapted to the reꢀ

quirements of the crystal packing. The volume of the new

unit cell is only 0.8% smaller than the doubled volume of

the initial unit cell. The steric strains are partially reduced

due to the more ordered positions of the perchlorate anꢀ

ions and solvent molecules. Evidently, the volume of the

free space occupied by these small species decreases,

resulting in their fixation in particular positions with reꢀ

spect to other components of the unit cell.

The crystal packing of 9b•MeCN•0.5C₆H₆•H₂O

is similar to that of the aboveꢀconsidered structure of

8b•0.5C₆H₆•0.125H₂O. The cations of compound 9b

form stacks composed of centrosymmetric headꢀtoꢀtail

dimers related to each other by centers of symmetry. The

structure of the dimer formed via N⁺—H...O(macrocycle)

hydrogen bonds is shown in Fig. 23 (N(1)H...O(3A) and

N(1)H...O(3´A), 2.01 and 2.14 Å, respectively; the angles

at the H atoms are 155 and 170°). The ethylene bonds in

the dimers and between the dimers are strictly antiparallel.

The distance d₁in the dimers is 4.07 Å, and the distance

between the ethylene groups of adjacent dimers in the

stack, d₂, is even shorter (3.81 Å). Both distances are favorꢀ

able for the PCA reaction giving the centrosymmetric rctt

isomer of cyclobutane. However, the formation of cycloꢀ

butane between the adjacent dimers should be accompaꢀ

nied by the decomposition of the dimer and a deeper conꢀ

formational rearrangement of the cations. The process

occurring simultaneously at the contacts d₁and d₂should

be inevitably accompanied by the singleꢀcrystal degradaꢀ

tion. The irradiation of the crystal led to its degradation.

O(4´A)

O(1)

C(7)

O(5A)

N(1)

O(4A)

O(3A)

O(2)

C(6)

O(6)

O(3´A)

O(1W)

O(3´)

N(1A)

O(1WA)

O(6A)

O(3)

O(5)

O(2A)

O(4)

C(6A)

C(7A)

O(1A)

O(4´)

Fig. 23. Structure of the dimer pair in the crystal structure of 9b•MeCN•0.5C₆H₆•H₂O. The atoms labeled with A are related to the

unlabeled atoms by symmetry operations. The hydrogen bonds are shown as dashed lines.

Crystal packings of protonated styrylpyridines

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

1753

In the crystal of related styryl dye 9a, the molecular

cations encapsulating a water molecule in the crown ether

cavity are also arranged in centrosymmetric stacks in a synꢀ

headꢀtoꢀtail fashion, and the PCA reaction proceeds in

these stacks to form the corresponding rctt isomer of cycloꢀ

butane with the single crystal remaining intact.²⁰

In the crystals of 9b•NH₄ClO₄(Fig. 24), the organic

cations form stacks, which are surrounded by rotationally

mobile perchlorate anions and the crown ether moieties of

adjacent stacks. The ammonium cation encapsulated in

the cavity of the macrocycle forms a N⁺—H...^–OClO₃

hydrogen bond also with the perchlorate anion (N...O and

H...O, 2.90 and 2.18 Å, respectively; the angle at the H

atom is 165°). The stacks are arranged in a headꢀtoꢀhead

fashion with a substantial shift of the ethylene groups in

parallel planes (d = 6.23 Å), due to which the PCA reacꢀ

tion cannot take place in this crystal packing.

b

a

c

The structure of the rctt isomer of cyclobutane derivaꢀ

tive 14 produced upon irradiation of a film of compound

9b was confirmed by Xꢀray diffraction. For this purpose,

a sample of compound 9b irradiated in the solid phase was

crystallized with the addition of 70% HClO₄. Cyclobutane

14 was studied by singleꢀcrystal Xꢀray diffraction. The

structural units are shown in Fig. 25.

0

Fig. 24. Projection of the crystal packing of 9b•NH₄ClO₄along

the a axis. The hydrogen bonds are indicated by dashed lines.

In the structure of 14•NH₄ClO₄•H₂O, the position of

one of the two independent perchlorate anions is fixed,

whereas another anion is rotationally disordered over three

positions (the occupancy ratio is 0.45 : 0.35 : 0.20). The

Cl(1)O₄^–anion is involved in the hydrogen bond with the

pyridinium moiety C₅H₄N(1)⁺H or C₅H₄N(2)⁺H: the

The characteristic features of the crystal packing correlate

well with the fast photoreaction in a polycrystalline film of

compound 9b and its stereochemical result according to

the ¹H NMR spectroscopic data.

O(5)

O(10)

O(4)

O(11)

O(3)

O(9)

O(6)

N(1S)

N(1SA)

O(2)

O(12)

O(1)

O(7)

C(7)

O(8)

C(29)

Cl(2)

C(6)

C(30)

N(2)

O(12A)

O(12´)

Cl(1)

O(1W)

N(1)

O(13)

O(14)

O(11´)

Fig. 25. Structure of 14•NH₄ClO₄•H₂O. The nonhydrogen atoms are shown as displacement ellipsoids at the 50% probability level.

The N(1SA)⁺H₄ion and the O(12A) atom of the perchlorate anion are generated by symmetry operations. The hydrogen bonds are

shown as dashed lines.

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Kuz´mina et al.

N(1)...O(11´), N(1)H...O(11´) and N(2)...O(12A),

N(2)H...O(12A) distances are 2.86, 2.00 and 2.91, 2.11 Å;

the angles at the hydrogen atoms are 164 and 152°. In the

crystal, the water molecule H₂O(1W) forms hydrogen

bonds with the oxygen atoms of the disordered anion

Cl(2)O₄^–(O(1W)H...O, 2.19 and 2.25 Å). The cavities of

both crown ether moieties are occupied by ammonium

ions, which appeared in the course of crystallization due

to the hydrolysis of acetonitrile. The N—H...O hydrogen

bonds have the following parameters: the distances vary

from 1.94 to 2.45 Å and the angles at the H atoms are in

the range of 126—178°.

It is interesting that the rctt isomer of cyclobutane 14

characterized by a centrosymmetric bonding scheme ocꢀ

cupies a general position in the crystal, and its cycloꢀ

butane ring adopts a nonplanar conformation, like in the

crystal of 13•C₆H₆•0.25H₂O (the torsion angles in the

ring C(6)—C(7)—C(29)—C(30) vary from –18 to 18°). In

the centrosymmetric monoclinic unit cell (space group

P2/c), the dication lies on a twofold axis with half occuꢀ

pancy. This cyclobutane is transformed into another isoꢀ

mer occupying virtually the same position in the unit cell

by a twofold axis. The resulting pattern consists of two

disordered equally occupied orientations of the dication

(Fig. 26). Probably, this single crystal is a twin, with each

component having lower symmetry (Pc). However, the

lowering of the crystal symmetry by going to the space

group Pc leads to the same result, viz., the same disorder

of the molecule. An examination of the doubling of the

unit cell showed that it is impossible to go to the larger

unit cell. At the same time, it cannot be ruled out that the

observed type of disorder does occur in the crystal since, as

can be seen from Fig. 26, the disorder elements have an

almost single contour. It should be noted that these Xꢀray

diffraction data are characterized by high accuracy, which

allowed us to locate the hydrogen atoms of the cyclobuꢀ

tane corresponding to different disorder elements.

Therefore, the study of the characteristic features of

the crystal packings of protonated 4ꢀstyrylpyridines showed

that their crystals, as expected, consist primarily of stacks

similar to the structures of related 4ꢀstyrylpyridine dyes.

Many of them, particularly centrosymmetrically related

stacks, are favorable for the solidꢀstate PCA reaction.

However, the translationally related staks, which are unꢀ

favorable for the PCA reaction in the crystals, are equally

often observed. This distinguishes protonated styrylꢀ

pyridines from both neutral styrylpyridines, for which ladꢀ

der packings without stacking interactions are most typiꢀ

cal in the crystals, and the corresponding dyes, whose

crystals are, as a rule, composed of centrosymmetrically

related stacks formed by molecules arranged in a synꢀheadꢀ

toꢀtail fashion. This difference in the packing motifs of

these compounds is attributed to the formation of hydroꢀ

gen bonds between the N⁺—H group of the molecular

cation and the perchlorate anion. The presence of hydroꢀ

gen bonds in the crystal packing also leads to the higher

overall rigidity of the structure and results in a decrease in

the rate of the PCA reaction. Not only hydrogen bonds but

also other weak directional interactions, for example, the

S...S interaction, which is not observed in crystals of styryl

dyes, can also play the structureꢀstabilizing function.

In spite of the aboveꢀmentioned increase in the rigidity

of the structures, the photoreaction takes place both in

single crystals and polycrystalline films of almost all the

crystals under examination, which consist of centroꢀ

symmetrically related stacks composed of superimposed

stacked dimers preorganized for the PCA reaction. In sinꢀ

gle crystals of protonated styrylpyridines, these reactions

more often lead to their degradation than the correspondꢀ

ing reactions of related dyes.

In the single crystals of protonated 15ꢀcrownꢀ5ꢀconꢀ

taining styrylpyridine, which are stabilized not by hydroꢀ

gen bonds between the cations and anions but by the

N⁺—H...O(macrocycle) hydrogen bonds linking the catꢀ

O(11)

O(1A)

O(6A)

O(12)

N(2A)

O(8)

O(7)O(2A)

O(4)

O(10)

O(9)

N(1)

O(10A)

O(4A)

O(3A)

O(9A)

O(3)

O(11A)

O(5)

O(2)

O(6)

O(12A)

O(8A)

O(7A)

O(1)

N(1A)

N(2)

Fig. 26. Disorder of the cyclobutane dication in the crystal structure of 14•NH₄ClO₄•H₂O. The atoms labeled with A are related to

the unlabeled atoms by symmetry operations.

Crystal packings of protonated styrylpyridines

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

1755

ions to form hydrogenꢀbonded dimers, the PCA reaction

was observed to proceed as the singleꢀcrystalꢀtoꢀsingleꢀ

crystal reaction.

positions. Such crystals are best described by structures of

supramolecular assemblies that are formed in solution as

a result of selfꢀassembly.

Only rotationally and translationally mobile anions,

which are not fixed by hydrogen bonds, combined with

solvent molecules, as well as flexible crown ether moiꢀ

eties, facilitate the creation of a soft shell around the dimers

of organic cations, which efficiently reduces strains that

appear in the crystals in the course of the structural photoꢀ

transformation of the main components.

The approach, which we developed in terms of the

crystal design of specified packing of styrylheterocycles, is,

on the whole, correct. Although the protonated forms of

these compounds are somewhat less suitable for investigation

of solidꢀstate PCA reactions in single crystals compared to

related styryl dyes, these compounds are much more promꢀ

ising in this respect than neutral styrylheterocycles.

Protonated styrylpyridines were found to be prone to

the formation of crystals with a high degree of disorder or

of lowꢀsymmetry crystals of poor quality, which contain

a large number of crystallographically independent formula

units and are characterized by incomplete occupancy of

Experimental

The melting points (uncorrected) were measured in capillarꢀ

ies on a MelꢀTemp II instrument. The ¹H NMR spectra were

Table 2. Crystal parameters and the Xꢀray diffraction data collection and refinement statistics for compounds 1b, 7b•0.5C₆H₆, 2b,

and 2b/11

Parameter

1b

7b•0.5C₆H₆

2b

2b/11

Molecular formula

Molecular weight/g mol^–1

C₁₃H₁₂ClNO₄

281.69

C₁₆H₁₃Cl₃NO₄

389.62

C₁₃H₁₁ClN₂O₆

326.69

C₂₆H₂₂Cl₂N₄O₁₂

653.38

Crystal system

Space group

a/Å

b/Å

c/Å

Monoclinic

C2/c

9.8873(3)

12.6317(4)

19.9393(6)

90

92.1200(10)

90

2488.58(13)

8

Monoclinic

P2₁/n

21.9866(19)

17.5923(15)

36.269(3)

90

106.924(4)

90

13421(2)

32

Monoclinic

P2₁/n

7.9262(3)

13.8640(6)

12.9850(5)

90

101.976(2)

90

1395.85(10)

4

Monoclinic

P2₁/n

7.684(3)

14.157(5)

13.004(4)

90

102.453(6)

90

1381.3(8)

2

α/deg

β/deg

γ/deg

V/Å³

Z

ρ

_calc/g cm^–3

1.504

1.543

1.555

1.571

F(000)

μ(Mo/Kα)/mm^–1

1168

0.317

6368

0.566

672

0.306

672

0.309

Crystal dimensions/mm

Scan mode/θꢀScanning range/deg

Ranges of reflection indices

0.26×0.14×0.14

ω/2.78—29.00

–13 ≤ h ≤ 13,

–13 ≤ k ≤ 17,

–27 ≤ l ≤ 27

7703

0.24×0.20×0.14

ω/1.27—29.00

–27 ≤ h ≤ 29,

–24 ≤ k ≤ 24,

–49 ≤ l ≤ 46

114407

0.64×0.24×0.09

ω/2.78—30.00

–11 ≤ h ≤ 11,

–19 ≤ k ≤ 15,

–18 ≤ l ≤ 17

8725

0.64×0.24×0.09

ω/2.84—28.98

–10 ≤ h ≤ 10,

–19 ≤ k ≤ 9,

–13 ≤ l ≤ 17

7918

Number of measured reflections

Number of independent

3279 (0.0229)

35330 (0.5339)

3956 (0.0204)

3566 (0.1052)

reflections (R_int

)

Number of reflections with I > 2σ(I)

Number of refinement variables

2701

299

5951

1729

3055

243

1433

390

R Factors based on reflections

with I > 2σ(I)

R₁

wR₂

0.0363

0.1009

0.1042

0.2227

0.0509

0.1306

0.1216

0.3038

based on all reflections

R₁

wR₂

0.0460

0.1062

0.4625

0.3044

0.0684

0.1455

0.2583

0.3397

Goodnessꢀofꢀfit on F²

Residual electron density

(min/max), e/Å³

1.074

–0.386/0.312

0.705

–0.888/2.037

1.025

–0.629/0.976

1.010

–0.541/0.451

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Kuz´mina et al.

recorded on a Bruker DRX500 spectrometer (500.13 MHz) in

DMSOꢀd₆at 25—30 °C with the use of the solvent as the internal

1,4,7,10,13,16ꢀbenzohexaoxacyclooctadecinꢀ18ꢀyl)ꢀ1ꢀethenyl]ꢀ

pyridine, were synthesized according to known methods;^1,20,23

70% HClO₄(Aldrich) was used without additional purification.

Synthesis of styrylpyridine hydroperchlorates 1b—9b (general

procedure). To a solution of neutral 4ꢀstyrylpyridine (0.60 mmol)

in acetonitrile (2 mL), 70% HClO₄(62 μL, 0.72 mmol) was

added. The reaction mixture was diluted with 30 mL of benzene

(benzene—hexane mixture (2 : 1) for 7b and 9b) and cooled to

5 °C. The precipitate that formed was filtered off, washed with

distilled water (2×2 mL), and dried in air in the dark.

4ꢀ[(E)ꢀ1ꢀEthenylꢀ2ꢀphenyl]pyridinium perchlorate (1b). Paleꢀ

yellow powder (yield 89%), m.p. 228—230 °C. Found (%):

C, 55.25; H, 4.17; N, 4.96. C₁₃H₁₂ClNO₄. Calculated (%): C, 55.43;

H, 4.29; N, 4.97. ¹H NMR, δ: 7.45 (t, 1 H, H(4´), J = 7.3 Hz);

7.50 (t, 2 H, H(3´), H(5´), J = 7.3 Hz); 7.54 (d, 1 H, CH=CHPy,

J = 16.6 Hz); 7.76 (d, 2 H, H(2´), H(6´), J = 6.8 Hz); 7.99

(d, 1 H, CH=CHPy, J = 16.6 Hz); 8.18 (d, 2 H, H(3), H(5),

J = 6.4 Hz); 8.83 (d, 2 H, H(2), H(6), J = 6.4 Hz). UV (MeCN),

standard (δ 2.50). The chemical shifts and the spinꢀspin couꢀ

H

pling constants were measured with an accuracy of 0.01 ppm and

0.1 Hz, respectively. The absorption spectra of solutions (C =

= 5•10^–5mol L^–1) in acetonitrile were recorded on a UVꢀ3101PC

spectrophotometer (Shimadzu) in the region of 200—600 nm

(with 1 nm sampling interval) in 1 cm quartz cells. The elemenꢀ

tal analysis was carried out in the Laboratory of Microanalysis of

the A. N. Nesmeyanov Institute of Organoelement Compounds

of the Russian Academy of Sciences (Moscow) using samples

dried in vacuo at 60 °C.

Neutral styrylpyridines, viz., 4ꢀ[(E)ꢀ1ꢀethenylꢀ2ꢀphenyl]ꢀ

pyridine, 4ꢀ[(E)ꢀ1ꢀethenylꢀ2ꢀ(4ꢀnitrophenyl)]pyridine, 4ꢀ{(E)ꢀ

2ꢀ[4ꢀ(dimethylamino)phenyl]ꢀ1ꢀethenyl}pyridine, 4ꢀ[(E)ꢀ1ꢀ

ethenylꢀ2ꢀ(4ꢀmethoxyphenyl)]pyridine, 4ꢀ{(E)ꢀ1ꢀethenylꢀ2ꢀ

[4ꢀ(methylsulfanyl)phenyl]}pyridine, 4ꢀ[(E)ꢀ2ꢀ(3,4ꢀdimethꢀ

oxyphenyl)ꢀ1ꢀethenyl]pyridine, 4ꢀ[(E)ꢀ2ꢀ(3,4ꢀdichlorophenyl)ꢀ

1ꢀethenyl]pyridine, 4ꢀ[(E)ꢀ2ꢀ(2,3,5,6,8,9,11,12ꢀoctahydroꢀ

benzoꢀ1,4,7,10,13ꢀpentaoxacyclopentadecinꢀ15ꢀyl)ꢀ1ꢀethenyl]ꢀ

pyridine, and 4ꢀ[(E)ꢀ2ꢀ(2,3,5,6,8,9,11,12,14,15ꢀdecahydroꢀ

λ

_max/nm (ε): 343 (30300).

4ꢀ[(E)ꢀ1ꢀEthenylꢀ2ꢀ(4ꢀnitrophenyl)]pyridinium perchlorate

(2b). Paleꢀbrown powder (yield 49%), m.p. > 250 °C (with deꢀ

Table 3. Crystal parameters and the Xꢀray diffraction data collection and refinement statistics for compounds 3b•0.5C₆H₆, 4b,

and 4b•0.5C₆H₆

Parameter

3b•0.5C₆H₆

4b

4b•0.5C₆H₆

Molecular formula

Molecular weight/g mol^–1

C₁₈H₂₀ClN₂O₄

363.81

C₁₄H₁₄ClNO₅

311.71

C₁₇H₁₇ClNO₅

350.77

Crystal system

Space group

a/Å

b/Å

c/Å

Triclinic

P1

Triclinic

P1

Triclinic

P1

–

6.8729(2)

15.7931(4)

18.0432(5)

67.8120(10)

79.3560(10)

88.4630(10)

1780.28(8)

4

8.4042(14)

8.8189(15)

10.4718(19)

77.185(2)

87.499(3)

66.431(2)

692.8(2)

2

6.7884(2)

9.1562(3)

13.4368(4)

79.2000(10)

89.7030(10)

81.6910(10)

811.57(4)

2

α/deg

β/deg

γ/deg

V/Å³

Z

ρ

_calc/g cm^–3

1.357

1.494

1.435

F(000)

μ(Mo/Kα)/mm^–1

764

0.240

324

0.297

366

0.263

Crystal dimensions/mm

Scan mode/θꢀScanning range/deg

Ranges of reflection indices

0.36×0.22×0.18

ω/1.24—29.00

–5 ≤ h ≤ 9,

–21 ≤ k ≤ 21,

–24 ≤ l ≤ 22

15674

0.29×0.12×0.04

ω/2.00–29.00

–11 ≤ h ≤ 11,

–12 ≤ k ≤ 11,

–14 ≤ l ≤ 14

7702

0.28×0.20×0.12

ω/1.54−29.00

–9 ≤ h ≤ 9,

–12 ≤ k ≤ 12,

–18 ≤ l ≤ 18

8528

Number of measured reflections

Number of independent reflections (R_int

Number of reflections with I > 2σ(I)

Number of refinement variables

)

9131 (0.0321)

7184

3680 (0.0333)

2648

4274 (0.0164)

3699

670

300

394

R Factors based on reflections with I > 2σ(I )

R₁

wR₂

0.0647

0.1736

0.0461

0.1079

0.0312

0.0898

based on all reflections

R₁

0.0830

0.1858

1.046

0.0686

0.1164

1.009

0.0375

0.0935

1.065

wR₂

Goodnessꢀofꢀfit on F²

Residual electron density

(min/max), e/Å³

–0.535/0.695

–0.388/0.293

–0.336/0.296

Crystal packings of protonated styrylpyridines

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

1757

comp.). Found (%): C, 47.85; H, 3.35; N, 8.54. C₁₃H₁₁ClN₂O₆.

Calculated (%): C, 47.79; H, 3.39; N, 8.58. ¹H NMR, δ: 7.74

(d, 1 H, CH=CHPy, J = 16.6 Hz); 8.00 (d, 2 H, H(2´), H(6´),

J = 8.6 Hz); 8.06 (d, 1 H, CH=CHPy, J = 16.6 Hz); 8.20 (d, 2 H,

H(3), H(5), J = 6.8 Hz); 8.34 (d, 2 H, H(3´), H(5´), J = 8.6 Hz);

8.88 (d, 2 H, H(2), H(6), J = 6.8 Hz). UV (MeCN), λ_max/nm (ε):

340 (33100).

4ꢀ{(E)ꢀ2ꢀ[4ꢀ(Dimethylamino)phenyl]ꢀ1ꢀethenyl}pyridinium

perchlorate (3b). Redꢀbrown crystals (yield 71%), m.p. 221—223 °C

(with decomp.). Found (%): C, 56.28; H, 5.53; N, 7.86.

C₁₅H₁₇ClN₂O₄•0.3C₆H₆•0.6H₂O. Calculated (%): C, 56.21;

H, 5.62; N, 7.80. ¹H NMR, δ: 3.02 (s, 6 H, NMe₂); 6.79 (d, 2 H,

H(3´), H(5´), J = 8.9 Hz); 7.19 (d, 1 H, CH=CHPy, J = 16.1 Hz);

7.60 (d, 2 H, H(2´), H(6´), J = 8.9 Hz); 7.90 (d, 1 H, CH=CHPy,

J = 16.1 Hz); 8.02 (d, 2 H, H(3), H(5), J = 6.6 Hz); 8.67 (d, 2 H,

H(2), H(6), J = 6.6 Hz). UV (MeCN), λ_max/nm (ε): 470 (36700).

4ꢀ[(E)ꢀ1ꢀEthenylꢀ2ꢀ(4ꢀmethoxyphenyl)]pyridinium perꢀ

chlorate (4b). Paleꢀyellow powder (yield 56%), m.p. 228—231 °C

(with decomp.). Found (%): C, 53.97; H, 4.49; N, 4.48.

C₁₄H₁₄ClNO₅. Calculated (%): C, 53.94; H, 4.53; N, 4.49.

¹H NMR, δ: 3.83 (s, 3 H, OMe); 7.06 (d, 2 H, H(3´), H(5´),

J = 8.8 Hz); 7.37 (d, 1 H, CH=CHPy, J = 16.4 Hz); 7.72 (d, 2 H,

H(2´), H(6´), J = 8.8 Hz); 7.95 (d, 1 H, CH=CHPy, J = 16.4

Hz); 8.12 (d, 2 H, H(3), H(5), J = 6.8 Hz); 8.78 (d, 2 H, H(2),

H(6), J = 6.8 Hz). UV (MeCN), λ_max/nm (ε): 380 (31100).

4ꢀ{(E)ꢀ2ꢀ[1ꢀEthenylꢀ4ꢀ(methylsulfanyl)phenyl]}pyridinium

perchlorate (5b). Yellow powder (yield 73%), m.p. 228—230 °C

(with decomp.). Found (%): C, 51.28; H, 4.35; N, 4.21.

C₁₄H₁₄ClNO₄S. Calculated (%): C, 51.30; H, 4.31; N, 4.27.

¹H NMR, δ: 2.53 (s, 3 H, SMe); 7.36 (d, 2 H, H(3´), H(5´),

J = 8.3 Hz); 7.47 (d, 1 H, CH=CHPy, J = 16.4 Hz); 7.69 (d, 2 H,

H(2´), H(6´), J = 8.3 Hz); 7.93 (d, 1 H, CH=CHPy, J = 16.4 Hz);

8.12 (d, 2 H, H(3), H(5), J = 6.3 Hz); 8.79 (d, 2 H, H(2), H(6),

J = 6.3 Hz). UV (MeCN), λ_max/nm (ε): 392 (32500).

4ꢀ[(E)ꢀ2ꢀ(3,4ꢀDimethoxyphenyl)ꢀ1ꢀethenyl]pyridinium perꢀ

chlorate (6b). Yellow powder (yield 90%), m.p. 260—262 °C

(with decomp.). Found (%): C, 50.81; H, 4.69; N, 3.91.

C₁₅H₁₆ClNO₆•0.75H₂O. Calculated (%): C, 50.71; H, 4.97;

1

N, 3.94. H NMR, δ: 3.82 (s, 3 H, OMe); 3.85 (s, 3 H, OMe);

7.06 (d, 1 H, H(5´), J = 8.4 Hz); 7.29 (dd, 1 H, H(6´), J = 8.4 Hz,

J = 1.8 Hz); 7.39 (d, 1 H, H(2´), J = 1.8 Hz); 7.40 (d, 1 H,

CH=CHPy, J = 16.4 Hz); 7.91 (d, 1 H, CH=CHPy, J = 16.4 Hz);

Table 4. Crystal parameters and the Xꢀray diffraction data collection and refinement statistics for compounds 5b and

5b•0.76C₆H₆•0.14H₂O, 6b^mand 6b^o

Parameter

5b

5b•0.76C₆H₆•0.14H₂O

6b^m

6b^o

Molecular formula

Molecular weight/g mol^–1

C₁₄H₁₄ClNO₄S

327.77

C_18.57H_18.86ClNO_4.14

389.86

S

C₁₅H₁₆ClNO₆

341.74

C₁₅H₁₆ClNO₆

341.74

Crystal system

Space group

a/Å

b/Å

c/Å

Triclinic

P1

Triclinic

P1

Monoclinic

C2/c

18.7653(5)

13.4602(4)

12.5863(4)

90

109.8750(10)

90

2989.75(15)

8

Orthorhombic

Pca2₁

34.351(4)

4.9898(5)

8.9617(10)

90

–

8.0773(14)

9.6610(16)

10.0253(17)

93.815(7)

101.120(7)

106.520(6)

729.8(2)

14.764(4)

25.923(6)

27.154(7)

81.782(9)

77.770(11)

86.951(10)

10049(4)

21

α/deg

β/deg

γ/deg

90

V/Å³

1536.1(3)

4

1.478

Z

ρ

2

_calc/g cm^–3

1.492

1.353

1.518

F(000)

μ(Mo/Kα)/mm^–1

340

0.419

4272

0.332

1424

0.288

712

0.280

Crystal dimensions/mm

Scan mode/θꢀScanning range/deg

Ranges of reflection indices

0.24×0.22×0.16

ω/2.09—29.00

–11 ≤ h ≤ 10,

–13 ≤ k ≤ 13,

–13 ≤ l ≤ 13

5986

0.60×0.08×0.03

ω/1.18—29.00

–18 ≤ h ≤ 20,

–32 ≤ k ≤ 35,

–36 ≤ l ≤ 37

84512

0.24×0.22×0.20

ω/1.90—29.00

–25 ≤ h ≤ 25,

–18 ≤ k ≤ 17,

–17 ≤ l ≤ 17

15638

0.60×0.12×0.08

ω/1.19—28.50

–46 ≤ h ≤ 31,

–6 ≤ k ≤ 6,

–9 ≤ l ≤ 12

8231

Number of measured reflections

Number of independent reflections (R_int

Number of reflections with I > 2σ(I)

Number of refinement variables

)

3770 (0.0565)

2081

52435 (0.4538)

5001

3980 (0.0258)

3291

3535 (0.0592)

2302

194

865

337

208

R Factors based on reflections with I > 2σ(I)

R₁

wR₂

0.0926

0.2975

0.1973

0.3672

0.0393

0.1081

0.1089

0.2944

based on all reflections

R₁

0.1432

0.3133

1.104

0.6555

0.5165

0.764

0.0489

0.1142

1.044

0.1565

0.3444

1.237

wR₂

Goodnessꢀofꢀfit on F²

Residual electron density

(min/max), e/Å³

–0.790/0.876

–0.669/1.769

–0.369/0.449

–0.654/1.458

1758

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

Kuz´mina et al.

8.09 (d, 2 H, H(3), H(5), J = 6.1 Hz); 8.76 (d, 2 H, H(2), H(6),

J = 6.1 Hz). UV (MeCN), λ_max/nm (ε): 395 (29200).

H(5), J = 6.5 Hz); 8.76 (d, 2 H, H(2), H(6), J = 6.5 Hz).

UV (MeCN), λ_max/nm (ε): 394 (26500).

4ꢀ[(E)ꢀ2ꢀ(3,4ꢀDichlorophenyl)ꢀ1ꢀethenyl]pyridinium perchloꢀ

rate (7b). White powder (yield 76%), m.p. 210—212 °C. Found (%):

C, 44.51; H, 2.73; N, 3.91. C₁₃H₁₀Cl₃NO₄. Calculated (%):

C, 44.54; H, 2.88; N, 4.00. ¹H NMR, δ: 7.64 (d, 1 H, CH=CHPy,

J = 16.4 Hz); 7.71 (dd, 1 H, H(6´), J = 8.4 Hz, J = 1.8 Hz); 7.76

(d, 1 H, H(5´), J = 8.4 Hz); 7.92 (d, 1 H, CH=CHPy, J = 16.4

Hz); 8.04 (d, 1 H, H(2´), J = 1.8 Hz); 8.13 (d, 2 H, H(3), H(5),

J = 6.6 Hz); 8.86 (d, 2 H, H(2), H(6), J = 6.6 Hz). UV (MeCN),

4ꢀ[(E)ꢀ2ꢀ(2,3,5,6,8,9,11,12,14,15ꢀDecahydroꢀ1,4,7,10,13,16ꢀ

benzohexaoxacyclooctadecinꢀ18ꢀyl)ꢀ1ꢀethenyl]pyridinium percꢀ

hlorate (9b). Yellow powder (yield 95%), m.p. 233—235 °C

(with decomp.). Found (%): C, 51.90; H, 6.11; N, 2.63.

C₂₃H₃₀ClNO₁₀•H₂O. Calculated (%): C, 51.74; H, 6.04; N, 2.62.

¹H NMR, δ: 3.53 (s, 4 H, 2 CH₂O); 3.57 (m, 4 H, 2 CH₂O); 3.62

(m, 4 H, 2 CH₂O); 3.77 (m, 2 H, 4´ꢀCH₂CH₂OAr); 3.80 (m, 2 H,

3´ꢀCH₂CH₂OAr); 4.15 (m, 2 H, 4´ꢀCH₂OAr); 4.18 (m, 2 H,

3´ꢀCH₂OAr); 7.06 (d, 1 H, H(5´), J = 8.3 Hz); 7.27 (dd, 1 H,

H(6´), J = 8.3 Hz, J = 1.5 Hz); 7.39 (d, 1 H, CH=CHPy,

J = 16.3 Hz); 7.39 (d, 1 H, H(2´), J = 1.5 Hz); 7.89 (d, 1 H,

CH=CHPy, J = 16.3 Hz); 8.07 (d, 2 H, H(3), H(5), J = 6.4 Hz);

8.76 (d, 2 H, H(2), H(6), J = 6.4 Hz). UV (MeCN), λ_max/nm (ε):

389 (26800).

λ

_max/nm (ε): 339 (32100).

4ꢀ[(E)ꢀ2ꢀ(2,3,5,6,8,9,11,12ꢀOctahydroꢀ1,4,7,10,13ꢀbenzoꢀ

pentaoxacyclopentadecinꢀ15ꢀyl)ꢀ1ꢀethenyl]pyridinium perchlorꢀ

ate (8b). Yellow powder (yield 70%), m.p. 242—244 °C. Found (%):

C, 53.59; H, 5.68; N, 2.79. C₂₁H₂₆ClNO₉. Calculated (%):

C, 53.45; H, 5.55; N, 2.97. ¹H NMR, δ: 3.63 (m, 8 H, 4 CH₂O);

3.79 (m, 2 H, 4´ꢀCH₂CH₂OAr); 3.81 (m, 2 H, 3´ꢀCH₂CH₂OAr);

4.12 (m, 2 H, 4´ꢀCH₂OAr); 4.14 (m, 2 H, 3´ꢀCH₂OAr); 7.05

(d, 1 H, H(5´), J = 8.3 Hz); 7.28 (br.d, 1 H, H(6´), J = 8.3 Hz);

7.38 (d, 1 H, CH=CHPy, J = 16.3 Hz); 7.40 (br.s, 1 H, H(2´));

7.88 (d, 1 H, CH=CHPy, J = 16.3 Hz); 8.06 (d, 2 H, H(3),

Synthesis of cyclobutane derivatives from hydroperchlorates

1b—9b (general procedure). Benzene (0.3 mL) was added to

a solution of compounds 1b—9b (0.1 mmol) in MeCN (0.5—1 mL).

The reaction mixture was concentrated in a 10ꢀcm Petri dish to

form a polycrystalline film of the corresponding compound. The

Table 5. Crystal parameters and the Xꢀray diffraction data collection and refinement statistics for compounds 8b•0.5C₆H₆•0.125H₂O,

(8b/13)•C₆H₆•0.25H₂O, and 13•C₆H₆•0.25H₂O

Parameter

8b•0.5C₆H₆•0.125H₂O

(8b/13)•C₆H₆•0.25H₂O

13•C₆H₆•0.25H₂O

Molecular formula

Molecular weight/g mol^–1

C₂₄H_29.25ClNO_9.13

513.18

C₄₈H_58.5Cl₂N₂O_18.25

1026.37

C₄₈H_58.5Cl₂N₂O_18.25

1026.37

Crystal system

Space group

a/Å

b/Å

c/Å

Triclinic

–

P1

11.9327(16)

12.7937(16)

16.551(2)

79.986(7)

88.423(6)

77.531(6)

2429.4(5)

4

11.911(2)

12.921(2)

16.348(3)

79.280(9)

88.087(8)

77.918(8)

2417.2(7)

2

15.8911(8)

16.2070(8)

19.3135(9)

80.241(3)

85.211(3)

79.987(3)

4820.0(4)

4

α/deg

β/deg

γ/deg

V/Å³

Z

ρ

_calc/g cm^–3

1.403

1.410

1.414

F(000)

μ(Mo/Kα)/mm^–1

1081

0.212

1081

0.213

2162

0.214

Crystal dimensions/mm

Scan mode/θꢀScanning range/deg

Ranges of reflection indices

0.46×0.08×0.06

ω/1.25—29.00

–16 ≤ h ≤ 16,

–17 ≤ k ≤ 17,

–22 ≤ l ≤ 21

27380

0.46×0.08×0.06

ω/1.64—29.00

–16 ≤ h ≤ 16,

–17 ≤ k ≤ 17,

–22 ≤ l ≤ 22

30211

0.12×0.08×0.06

ω/1.29—18.96

–14 ≤ h ≤ 14,

–14 ≤ k ≤ 14,

–17 ≤ l ≤ 17

26012

Number of measured reflections

Number of independent reflections (R_int

Number of reflections with I > 2σ(I)

Number of refinement variables

)

12822 (0.1885)

2882

12716 (0.3006)

2428

7502 (0.0481)

5670

807

768

1343

R Factors based on reflections with I > 2σ(I)

R₁

wR₂

0.0929

0.1704

0.1152

0.1862

0.1021

0.2630

based on all reflections

R₁

0.3676

0.2198

0.787

0.4262

0.2459

0.783

0.1295

0.2802

1.089

wR₂

Goodnessꢀofꢀfit on F²

Residual electron density

(min/max), e/Å³

–0.247/0.384

–0.278/0.322

–0.316/0.734

Crystal packings of protonated styrylpyridines

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

1759

sample was irradiated with unfiltered light using a 60 W incanꢀ

descent lamp at a distance of 15 cm for 20—200 h. The resulting

compounds were collected mechanically. The compositions of

the products and the degree of conversion into cyclobutane deꢀ

rivatives were analyzed based on the ¹H NMR spectroscopic

data (in DMSOꢀd₆) by comparing the integrated intensities of

the signals for protons. The experimental data obtained at differꢀ

ent exposure times are given in Table 1. In the cases when the

degree of conversion was ≥95%, the characteristics of the resultꢀ

ing cyclobutane derivatives are given.

rꢀ4ꢀ[cꢀ2,tꢀ4ꢀDiphenylꢀtꢀ3ꢀ(pyridinioꢀ4ꢀyl)cyclobutyl]pyridiniꢀ

um diperchlorate (rcttꢀ10) was synthesized after irradiation for 50 h

as a white powder, m.p. 269—270 °C (with decomp.). Found (%):

C, 55.37; H, 4.21; N, 4.91. C₂₆H₂₄Cl₂N₂O₈. Calculated (%):

C, 55.43; H, 4.29; N, 4.97. ¹H NMR, δ: 4.87 (dd, 2 H, 2 CHAr,

J = 9.4 Hz, J = 7.4 Hz); 4.95 (dd, 2 H, 2 CHPy, J = 9.4 Hz,

J = 7.4 Hz); 7.12 (t, 2 H, 2 H(4´), J = 7.3 Hz); 7.21 (t, 4 H, 2 H(3´),

2 H(5´), J = 7.6 Hz); 7.26 (d, 4 H, 2 H(2´), 2 H(6´), J = 7.3 Hz);

7.81 (d, 4 H, 2 H(3), 2 H(5), J = 6.1 Hz); 8.66 (d, 4 H, 2 H(2),

2 H(6), J = 6.1 Hz). UV (MeCN), λ_max/nm (ε): 255 (13300).

rꢀ4ꢀ[cꢀ2,tꢀ4ꢀBis[4ꢀ(methylsulfanyl)phenyl]ꢀtꢀ3ꢀ(pyridinioꢀ4ꢀ

yl)cyclobutyl]pyridinium diperchlorate (rcttꢀ12) was synthesized

after irradiation for 20 h as a paleꢀyellow powder, m.p. > 214 °C

(with decomp.). Found (%): C, 49.97; H, 4.26; N, 4.17.

C₂₈H₂₈Cl₂N₂O₈S₂•H₂O. Calculated (%): C, 49.93; H, 4.49;

N, 4.16. ¹H NMR, δ: 2.38 (s, 6 H, 2 MeS); 4.80 (dd, 2 H,

2 CHAr, J = 9.1 Hz, J = 6.4 Hz); 4.86 (dd, 2 H, 2 CHPy,

J = 9.1 Hz, J = 6.4 Hz); 7.08 (d, 4 H, 2 H(3´), 2 H(5´), J = 8.2 Hz);

7.20 (d, 4 H, 2 H(2´), 2 H(6´), J = 8.2 Hz); 7.76 (d, 4 H, 2 H(3),

2 H(5), J = 5.9 Hz); 8.67 (d, 4 H, 2 H(2), 2 H(6), J = 5.9 Hz).

UV (MeCN), λ_max/nm (ε): 260 (31400).

rꢀ4ꢀ[cꢀ2,tꢀ4ꢀBis(2,3,5,6,8,9,11,12ꢀoctahydroꢀ1,4,7,10,13ꢀ

benzopentaoxacyclopentadecinꢀ15ꢀyl)ꢀtꢀ3ꢀ(pyridinioꢀ4ꢀyl)cycloꢀ

butyl]pyridinium diperchlorate (rcttꢀ13) was synthesized after

irradiation for 200 h as a paleꢀyellow powder, m.p. > 175 °C

(with decomp.). Found (%): C, 52.35; H, 5.47; N, 2.73.

C₄₂H₅₂Cl₂N₂O₁₈•H₂O. Calculated (%): C, 52.45; H, 5.66;

N, 2.91. ¹H NMR, δ: 3.58 (m, 16 H, 8 CH₂O); 3.70 (m, 8 H,

4 CH₂CH₂OAr); 3.93 (m, 8 H, 4 CH₂OAr); 4.75 (dd, 2 H,

2 CHAr, J = 8.5 Hz, J = 6.5 Hz); 4.82 (dd, 2 H, 2 CHPy,

J = 8.9 Hz, J = 6.5 Hz); 6.75 (d, 2 H, 2 H(5´), J = 8.3 Hz); 6.77

(br.d, 2 H, 2 H(6´), J = 8.3 Hz); 6.82 (br.s, 2 H, 2 H(2´)); 7.79

(d, 4 H, 2 H(3), 2 H(5), J = 5.8 Hz); 8.68 (d, 4 H, 2 H(2), 2 H(6),

J = 5.8 Hz). UV (MeCN), λ_max/nm (ε): 281 (7000).

Table 6. Crystal parameters and the Xꢀray diffraction data collection and refinement statistics for compounds 9b•MeCN•0.5C₆H₆•H₂O,

9b•NH₄ClO₄, and 14•NH₄ClO₄•H₂O

Parameter

9b•MeCN•0.5C₆H₆•H₂O

9b•NH₄ClO₄

14•NH₄ClO₄•H₂O

Molecular formula

Molecular weight/g mol^–1

C₂₈H₃₈ClN₂O₁₁

614.05

C₂₃H₃₄Cl₂N₂O₁₄

633.42

C₄₆H₇₀Cl₄N₄O₂₉

1284.86

Crystal system

Space group

a/Å

b/Å

c/Å

Triclinic

Monoclinic

P2/c

11.5375(4)

10.8660(4)

22.8582(8)

90

99.5780(10)

90

2825.70(17)

2

–

P1

7.691(2)

13.959(4)

14.546(4)

77.688(5)

84.591(5)

78.839(5)

1494.7(7)

2

6.2285(6)

12.3326(11)

19.1841(16)

82.251(4)

84.565(4)

76.145(3)

1414.7(2)

2

α/deg

β/deg

γ/deg

V/Å³

Z

ρ

_calc/g cm^–3

1.364

1.487

1.510

F(000)

μ(Mo/Kα)/mm^–1

650

0.190

664

0.302

1348

0.305

Crystal dimensions/mm

Scan mode/θꢀScanning range/deg

Ranges of reflection indices

0.22×0.12×0.10

ω/1.87—29.00

–10 ≤ h ≤ 10,

–19 ≤ k ≤18,

–19 ≤ l ≤ 19

14598

0.24×0.20×0.08

ω/1.07—25.00

–7 ≤ h ≤ 5,

–14 ≤ k ≤14,

–22 ≤ l ≤ 19

6705

0.29×0.22×0.06

ω/1.79—29.00

–15 ≤ h ≤ 15,

–14 ≤ k ≤ 14,

–31 ≤ l ≤ 31

34280

Number of measured reflections

Number of independent reflections (R_int

Number of reflections with I > 2σ(I)

Number of refinement variables

)

7647 (0.0670)

3977

4748 (0.0728)

2320

7517 (0.0471)

5077

500

408

681

R Factors based on reflections with I > 2σ(I)

R₁

wR₂

0.0674

0.1466

0.0921

0.1737

0.0744

0.1901

based on all reflections

R₁

wR₂

0.1363

0.1702

0.933

0.2007

0.2049

0.963

0.1105

0.2049

1.040

Goodnessꢀofꢀfit on F²

Residual electron density (min/max), e/Å³

–0.354/0.282

–0.428/0.578

–0.468/0.667

1760

Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011

Kuz´mina et al.

rꢀ4ꢀ[cꢀ2,tꢀ4ꢀBis(2,3,5,6,8,9,11,12,14,15ꢀdecahydroꢀ1,4,7,

10,13,16ꢀbenzohexaoxacyclooctadecinꢀ18ꢀyl)ꢀtꢀ3ꢀ(pyridinioꢀ4ꢀ

yl)cyclobutyl]pyridinium diperchlorate (rcttꢀ14) was synthesized

after irradiation for 20 h as a yellowish powder, m.p. 263—265 °C

(with decomp.). Found (%): C, 53.39; H, 5.75; N, 2.84.

C₄₆H₆₀Cl₂N₂O₂₀. Calculated (%): C, 53.54; H, 5.86; N, 2.72.

¹H NMR, δ: 3.51 (s, 8 H, 4 CH₂O); 3.52—3.60 (m, 16 H, 8 CH₂O);

3.68 (m, 8 H, 4 CH₂CH₂OAr); 3.95 (m, 8 H, 4 CH₂OAr); 4.70

(dd, 2 H, 2 CHAr, J = 9.5 Hz, J = 5.9 Hz); 4.76 (dd, 2 H,

2 CHPy, J = 9.5 Hz, J = 5.9 Hz); 6.76 (s, 4 H, 2 H(5´), 2 H(6´));

6.80 (s, 2 H, 2 H(2´)); 7.68 (br.s, 4 H, 2 H(3), 2 H(5)); 8.62 (br.s,

4 H, 2 H(2), 2 H(6)). UV (MeCN), λ_max/nm (ε): 283 (7500).

Xꢀray diffraction study. Single crystals of all compounds were

mounted on a Bruker SMARTꢀCCD or Bruker Microstar difꢀ

fractometer under a cold nitrogen stream (T = 150(2) K for 4b

and 9b•MeCN•0.5C₆H₆•H₂O and 120.0(2) K for the other

compounds). The unit cell parameters were measured and the

Xꢀray diffraction data sets were collected using MoꢀKα radiaꢀ

tion (λ = 0.71073 Å, graphite monochromator, ωꢀscan mode) on

the Bruker SMARTꢀCCD diffractometer or CuꢀKα radiation

(λ = 1.54184 Å, graphite monochromator, ωꢀscan mode) on the

Bruker Microstar diffractometer. The Xꢀray diffraction data were

processed with the use of the SAINT program.⁴⁵All structures were

solved by direct methods and refined by the leastꢀsquares method

with anisotropic displacement parameters for nonhydrogen atoms.

The exceptions were the oxygen atoms of the disordered perꢀ

chlorate anions in the structures of 3b•0.5C₆H₆, 13•C₆H₆•

•0.25H₂O, and 14•NH₄ClO₄•H₂O, the atoms of the disordered

pyridinium moieties in the structure of (8b/13)•C₆H₆•0.25H₂O,

and the whole structure of 5b•0.76C₆H₆•0.14H₂O, whose nonꢀ

hydrogen atoms were refined isotropically. The hydrogen atoms

at the C atoms were positioned geometrically and refined isotroꢀ

pically in the structures of 2b, 4b, and 4b•0.5C₆H₆(for the orꢀ

dered groups), 6b^m(for the ordered groups) or using a riding

model for the other structures. The hydrogen atoms at the N

atoms of the pyridinium moieties were positioned geometrically

and refined isotropically in the structures of 2b, 4b, 3b•0.5C₆H₆

(the ordered cation and the major s conformer of the disordered

cation), 5b, 9b•MeCN•0.5C₆H₆•H₂O, and 9b•NH₄ClO₄or

using a riding model for the other structures. The hydrogen atoms

with the CSD refcodes 778792 (1b), 778793 (2b), 778794 (2b/11),

778795 (3b•0.5C₆H₆), 778796 (4b), 778797 (4b•0.5C₆H₆),

778798 (5b), 778799 (5b•0.76C₆H₆•0.14H₂O), 778800 (6b^m),

778801 (6b^o), 778802 (7b•0.5C₆H₆), 778803 (8b•0.5C₆H₆•

•0.125H₂O), 778804 ((8b/13)•C₆H₆•0.25H₂O), 778805

(13•C₆H₆•0.25H₂O), 778806 (9b•MeCN•0.5C₆H₆•H₂O),

778807 (9b•NH₄ClO₄), and 778808 (14•NH₄ClO₄•H₂O).

This study was financially supported by the Russian

Foundation for Basic Research (Project No. 11ꢀ03ꢀ00647),

the Royal Society of the UK (L. G. Kuz´mina and J. A. K.

Howard), the Royal Society of Chemistry of the UK (L. G.

Kuz´mina and A. V. Churakov, Grants for Foreign

Authors), and the Photochemistry Center of the Russian

Academy of Sciences.

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Received June 11, 2010;

in revised form May 25, 2011

Article Doi

Design of crystal packings of styrylheterocycles and [2+2] photocycloaddition reactions in their single crystals 7.* Crystal structures of 4-styrylpyridine hydroperchlorates and solid-state [2+2] autophotocycloaddition reactions of these compounds

DOI: 10.1007/s11172-011-0259-8

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