113:
204:
147:, and it has been suggested by some studies that dehydrogenation may even occur spontaneously. The dihydrophenanthrene intermediate has never been isolated, but it has been detected spectroscopically in pump-probe experiments by virtue of its long wavelength optical absorption band. Although both the E-Z isomerization and the 6Ď€ electrocyclization are
232:
of the ring closed form. Also often the two free α-positions on the double bond are connected in a 5 or 6-membered ring in order to lock the double bond into the cis-form. This makes the dithienylethene undergo only open-closed ring isomerization, unconfused by E-Z isomerization. More recently, based
233:
on recent findings showing that by-product formation most likely occurs exclusively from the lowest singlet excited state, a superior fatigue resistance of dithienylethenes upon visible-light excitation has been achieved by attaching small triplet-sensitizing moieties to the diarylethene core via a
215:
Ortho-substitution of the aromatic units results in a stabilization against oxidation, but the closed-ring form still has a low thermodynamic stability in most cases (e.g. 2,3-dimesityl-2-butene has a half-life of 90 seconds at 20°C). This problem can be addressed by lowering the aromaticity of the
108:
lies well towards the trans-form because of its lower energy (~15 kJ mol in stilbene). The activation energy for thermal E-Z isomerization is 150–190 kJ mol for stilbene, meaning that temperatures above 200°C are required to isomerize stilbene at a reasonable rate, but most derivatives have lower
223:
Dithienylethene derivatives have shown different types of photochemical side reactions, e.g., oxidation or elimination reactions of the ring-closed isomer and formation of an annulated ring isomer as a byproduct of the photochromic reaction. In order to overcome the first, the 2-position of the
297:
in particular. The closed form has a conjugated path from one end of the molecule to the other, whereas the open form has not. This allows for the electronic communication between functional groups attached to the far ends of the diarylethene to be switched on and off using
95:
character of these groups. The quantum yield of this reaction is generally less than 0.1, and in most diarylethenes the close-ring form is thermally unstable, reverting to the cis-form in a matter of seconds or minutes under ambient
240:
The dithienylethenes are also of interest for the fact that their isomerization requires very little change of shape. This means that their isomerization in a solid matrix can take place much more quickly than with most other
289:
potential. These properties can be readily controlled by reversible isomerization between the open- and closed-ring states using photoirradiation, and thus they have been suggested for use in
139:, which upon irradiation undergoes an E to Z isomerization, which can be followed by a 6Ď€ electrocyclization. Reaction of the product of this reaction with molecular
245:
molecules. In the case of some analogs, photochromic behavior can even be carried out in single crystals without disrupting the crystal structure.
549:
380:
109:
energy barriers (e.g. 65 kJ mol for 4-aminostilbene). The activation energy of the electrocyclization is 73 kJ mol for stilbene.
253:
Typically, the open-ring isomers are colorless compounds, whereas the closed-ring isomers have colors dependent on their
164:
566:
160:
131:
After the 6Ď€ electrocyclization of the Z form to the "close-ring" form, most unsubstituted diarylethenes are prone to
468:
448:
57:
571:
460:
294:
500:
372:
163:
to the carbon-carbon double bond by groups that can not be removed during the oxidation. Following the
508:
290:
266:
286:
282:
274:
148:
105:
541:
254:
176:
84:
72:
energy minimum where the aromatic rings lie at 90° to each other. This conformation drops to the
480:
258:
20:
278:
208:
192:
121:
49:
Under the influence of light, these compounds can generally perform two kinds of reversible
43:
27:
539:
N. Katsonis, T. Kudernac, M. Walko, S. J. van der Molen, B. J. van Wees, B. L. Feringa,
112:
352:
560:
443:
216:
system. The most commonly used example are the dithienylethenes, i.e. alkenes with a
125:
101:
77:
69:
50:
458:
D. Mendive-Tapia, A. Perrier, M. J. Bearpark, M. A. Robb, B. Lasorne, D. Jacquemin,
262:
242:
144:
136:
73:
488:
188:
180:
168:
35:
523:
425:
410:
203:
65:
229:
217:
135:, leading to a re-aromatization of the π-system. The most common example is
132:
92:
61:
39:
24:
273:. Moreover, these two isomers differ from one another not only in their
360:
184:
76:
and generally relaxes to trans and cis forms in a 1:1 ratio, thus the
225:
172:
159:
One solution to the problem of oxidation is to replace the hydrogens
140:
31:
478:
M. Herder, B. Schmidt, L. Grubert, M. Pätzel, J. Schwarz, S. Hecht,
277:
but also in various physical and chemical properties, such as their
151:
processes, this oxidation renders the entire sequence irreversible.
270:
202:
111:
261:
along the molecular backbone. Therefore, many diarylethenes have
187:
mixture. This approach also has the advantage that the thermal (
88:
171:
fashion, leading to products with an anti configuration of the
87:
of the Z form, leading to an additional bond between the two
350:
S. P. Kwasniewski, L. Claes, J.-P. François, M. S. Deleuze,
299:
441:
M. Irie, T. Lifka, K. Uchida, S. Kobatake and Y. Shindo,
498:
S. Fredrich, R. Göstl, M. Herder, L. Grubert, S. Hecht,
175:
substituents. As both methyl groups are attached to a
80:
for E-Z isomerization is very rarely greater than 0.5.
167:, the photochemical 6Ď€ cyclization takes place in a
116:
Stilbene isomerizations under the influence of light
370:V. Balzani, A. Credi, F. M. Raymo, J. F. Stoddart,
128:(reversible state changes from exposure to light).
155:Stabilization of the closed-ring form to oxidation
191:) ring closure can not take place because of
8:
104:is also possible. In E-Z isomerization, the
183:(R,R and S,S) are formed, normally as a
91:functionalities and a disruption of the
517:
515:
333:
331:
311:
60:to Z isomerizations, most common for
7:
120:Both processes are often applied in
19:is the general name of a class of
14:
224:thiophenes is substituted with a
195:between the substitution groups.
68:). This process goes through an
1:
588:
339:Advanced Organic Chemistry
320:Advances in Photochemistry
38:. The simplest example is
414:: Memories and Switches.
30:bonded to each end of a
461:Phys. Chem. Chem. Phys.
295:3D optical data storage
165:Woodward–Hoffmann rules
257:, due to the extended
220:ring on either side.
212:
117:
501:Angew. Chem. Int. Ed.
391:B. L. Feringa (ed.),
373:Angew. Chem. Int. Ed.
237:-conjugated linkage.
206:
115:
467::18463-18471 (2014)
318:H. Görner, J. Kuhn,
291:optical data storage
302:and visible light.
287:oxidation-reduction
283:dielectric constant
106:thermal equilibrium
85:electrocyclizations
567:Aromatic compounds
542:Advanced Materials
487::2738–2747 (2015)
408:May 2000 issue of
393:Molecular Switches
359::7823-7836 (2003)
275:absorption spectra
255:chemical structure
228:group, preventing
213:
177:stereogenic center
122:molecular switches
118:
21:chemical compounds
548:, 18, 1397–1400.
481:J. Am. Chem. Soc.
341:, 4th ed. (1992).
265:behavior both in
44:geometric isomers
28:functional groups
579:
551:
537:
531:
519:
510:
496:
490:
476:
470:
456:
450:
439:
433:
421:
415:
406:
400:
389:
383:
368:
362:
348:
342:
335:
326:
316:
279:refractive index
236:
209:molecular switch
207:Dithienylethene
199:Dithienylethenes
193:steric hindrance
42:, which has two
587:
586:
582:
581:
580:
578:
577:
576:
557:
556:
555:
554:
538:
534:
520:
513:
497:
493:
477:
473:
457:
453:
447:747–750 (1999)
440:
436:
422:
418:
407:
403:
390:
386:
369:
365:
349:
345:
336:
329:
325:, 1-117 (1995).
317:
313:
308:
251:
234:
201:
157:
12:
11:
5:
585:
583:
575:
574:
572:Photochemistry
569:
559:
558:
553:
552:
532:
511:
507:: 1208 (2016)
491:
471:
451:
434:
416:
401:
384:
363:
353:J. Chem. Phys.
343:
327:
310:
309:
307:
304:
250:
247:
200:
197:
156:
153:
98:
97:
81:
51:isomerizations
13:
10:
9:
6:
4:
3:
2:
584:
573:
570:
568:
565:
564:
562:
550:
547:
544:
543:
536:
533:
529:
526:
525:
518:
516:
512:
509:
506:
503:
502:
495:
492:
489:
486:
483:
482:
475:
472:
469:
466:
463:
462:
455:
452:
449:
446:
445:
444:Chem. Commun.
438:
435:
431:
428:
427:
420:
417:
413:
412:
405:
402:
398:
395:, Wiley-VCH,
394:
388:
385:
381:
378:
375:
374:
367:
364:
361:
358:
355:
354:
347:
344:
340:
334:
332:
328:
324:
321:
315:
312:
305:
303:
301:
296:
292:
288:
284:
280:
276:
272:
268:
264:
260:
256:
248:
246:
244:
238:
231:
227:
221:
219:
210:
205:
198:
196:
194:
190:
186:
182:
178:
174:
170:
166:
162:
154:
152:
150:
146:
142:
138:
134:
129:
127:
126:photochromism
123:
114:
110:
107:
103:
102:isomerization
94:
90:
86:
82:
79:
78:quantum yield
75:
71:
70:excited state
67:
63:
59:
56:
55:
54:
52:
47:
45:
41:
37:
33:
29:
26:
22:
18:
545:
540:
535:
530:, 100, 1685.
527:
522:
504:
499:
494:
484:
479:
474:
464:
459:
454:
442:
437:
432:, 100, 1685.
429:
424:
419:
409:
404:
396:
392:
387:
376:
371:
366:
356:
351:
346:
338:
322:
319:
314:
263:photochromic
252:
249:Applications
243:photochromic
239:
222:
214:
158:
145:phenanthrene
137:(E)-stilbene
130:
119:
99:
74:ground state
48:
17:Diarylethene
16:
15:
399:, Weinheim.
379:, 39, 3348
271:solid state
259:conjugation
189:disrotatory
181:enantiomers
169:conrotatory
96:conditions.
66:azobenzenes
46:, E and Z.
36:double bond
561:Categories
524:Chem. Rev.
426:Chem. Rev.
411:Chem. Rev.
337:J. March,
306:References
149:reversible
23:that have
521:M. Irie,
423:M. Irie,
230:oxidation
218:thiophene
133:oxidation
62:stilbenes
267:solution
143:affords
124:and for
100:Thermal
93:aromatic
40:stilbene
34:–carbon
25:aromatic
485:137 (7)
269:and in
185:racemic
285:, and
226:methyl
179:, two
173:methyl
141:oxygen
32:carbon
528:2000
161:ortho
64:(and
546:2006
430:2000
397:2001
377:2000
293:and
89:aryl
357:118
83:6Ď€
563::
514:^
505:55
465:16
330:^
323:19
300:UV
281:,
53::
382:.
235:Ď€
211:.
58:E
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
