Features of styryl dye crystal packings and their influence on [2 + 2] photocycloaddition reaction with single crystal retention

Abstract

A new styryl dye of the 2-benzothiazole series which contains three methoxy groups and an iodide anion was synthesized. Three triclinic crystal forms of this dye were investigated by single crystal X-ray diffraction.All the modifications were shown to contain centrosymmetrically related stacks of cations with the syn-"head-to-tail" mutual arrangement. Stacks of cations are arranged as dimeric pairs with short interatomic distances between the ethylene group carbon atoms, d 1 = 3.54-3.75 Å and significantly longer analogous distances between the adjacent pairs, d 2 = 4.61-4.68 Å. The main difference of the packing consists in various orientations of N-ethyl substituents with respect to the centre of the dimer. The solid phase [2 + 2] photocycloaddition (PCA) reaction resulting in rctt isomer of the cyclobutane derivative, only proceeds in pairs where N-substituents are oriented outward from the centre of the dimeric pair. PCA is accomplished as a "single crystal-to-single crystal" transformation. CrystEngCommThis journal is

Cation−π Interactions in Organic Synthesis

“…A similar head-to-tail arrangement was observed for the crystals of ( E )-4-(4-nitrostyryl)­pyridinium salts 477 , ( E )- N -ethyl-4-styrylpyidinium containing an 18-crown-6-ether fragment 478 , ( E )-4-(2-(1-naphthyl)­vinyl)­pyridine hydrochlorides 479 , N -ethylstyrylbenzothiazoles 480 , (Figure ) and styrylthiazoles 458c – 458e . The photodimerization reactions of these alkenes yielded syn HT dimers in high yields.…”

Structure–Property Relationships of Dibenzylidenecyclohexanones

“…The possibility and stereoselectivity of PCA can both be controlled by supramolecular preorganization of double bonds, i.e., by creating the most appropriate geometry of the preceding dimer. 17 − 19 In the case of pyridine derivatives in the crystal, this can be accomplished by supramolecular templating by metal complexes, 20 resorcinol (pyridine-containing monoenones 21 and acyclic dienones 22 ) or by treatment with silver ions (only pyridine-containing acyclic dienones were studied). 23 …”

“…One more important feature of carbonyl-conjugated double bonds is the ability to undergo [2+2]-photocycloaddition (PCA) reactions. ,, Furthermore, in the case of free dienones, transformations of this type can occur both in the crystal and in solution. The possibility and stereoselectivity of PCA can both be controlled by supramolecular preorganization of double bonds, i.e., by creating the most appropriate geometry of the preceding dimer. − In the case of pyridine derivatives in the crystal, this can be accomplished by supramolecular templating by metal complexes, resorcinol (pyridine-containing monoenones and acyclic dienones) or by treatment with silver ions (only pyridine-containing acyclic dienones were studied) …”

Peculiarities of styryl dyes of the benzoselenazole series crystal packings and their influence on solid phase [2 + 2] photocycloaddition reaction with single crystal retention

“…14), four of which (1-4) are favorable for PCA. 21,38,[41][42][43] In the packing motifs 1-4 (Fig. 14) isolated stacks or stacking dimeric pairs of cations occur, which themselves do not form any π-stacking interactions with the adjacent stacks or dimeric pairs.…”

“…Recently, 37,38 we published investigations of styryl dyes of the 2-benzothiazole series 1 and 2 (Scheme 1) in three crystal forms for each.…”