Novel photochromic chemosensors for alkali-, alkali-earth and d-metal cations were synthesized and their photochemical and complexing properties investigated with the use of UV=vis, IR, 1 H= 7 Li NMR spectroscopy and quantum chemical calculations -DFT(B3LYP=6-31G).

The crown‐ether functionalized 2‐(N‐acetyl‐N‐arylaminomethylene)benzo[b]thiophene‐3(2H)‐ones exhibit photochromic behavior involving photoinitiated Z/E‐isomerization around the exocyclic CC bond followed by a fast thermal N → O acetyl migration and syn → anti isomerization of the resulting kinetically stable O‐acetyl isomers. The reverse rearrangement is an acid catalyzed reaction. The addition of alkali‐earth metal ions to solutions of N‐acyl isomers induces negligible changes in their UV/Vis spectra, which can be significantly enhanced after irradiation and conversion to the O‐acyl isomers. The compounds obtained may be used as sensitive photodynamic chemosensors with the ‘off‐on’ mechanism for alkali‐earth ions (Ca2+, Ba2+). Quantum‐chemical calculations using the DFT B3LYP/LanL2DZ method predict greater affinity of these sensors to Ca2+ ions (in the gas phase) and to Ba2+ ions (in acetonitrile). Copyright © 2007 John Wiley & Sons, Ltd.

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The novel heterocyclic fulgides, i.e. 3 isopropylidene 4 {1 [5 methoxy 1 (4 methoxy phenyl) 2 methyl 1H benzo[g]indol 3 yl]ethylidene}dihydrofuran 2,5 dione and 3 isopropyl idene 4 [1 (1 benzyl 5 methoxy 2 methyl 1H benzo[g]indol 3 yl)ethylidene]dihydrofuran 2,5 dione, were prepared and isolated as E isomers. Photochromism, E configuration, and high resistance to photocoloration-photobleaching of solutions of these fulgides as well as 3 isopropylidene 4 [1 (5 methoxy 2 methylnaphtho[1,2 b]furan 3 yl)ethylidene]dihydro furan 2,5 dione and 3 isopropylidene 4 [1 (5 methoxy 2 methyl 1 phenyl 1H benzo[g]indol 3 yl)ethylidene]dihydrofuran 2,5 dione synthesized previously were shown by X ray diffrac tion analysis, 1 H NMR spectroscopy and electronic absorption spectroscopy. The novel fulgides show fluorescence and high thermal stability of photogenerated cyclic form. Repeated photo coloration-photobleaching is accompanied by reversible photoinduced E-Z isomerization. Benzo[g]indolyl fulgides are characterized by the longer wavelength absorption of both original (E) and photoisomeric cyclic (C) forms as compared to naphthofuran fulgide.Photochromic heterocyclic fulgides are typically char acterized by thermal stability of a colored form and high resistance of isomers to repeated photocoloration-photo bleaching. These properties make fulgides (whose photo chromic mechanism is based on the hexatriene/cyclo hexadiene interconversion) promising candidates for use in optical memory devices and as molecular switches. 1,2Previously 3 we have reported on the photochromic prop erties and structure of novel N aryl 3 indolylfulgides giving fluorescent photogenerated isomers that is a neces sary condition for applicability of a molecular system in 3D optical data storage materials. 4-9 Preliminary results on the synthesis and photochromism of fulgides 1a,b have been presented elsewhere 10 but will be summarized here. In order to extend the family of such systems we have prepared new fulgides of benzo[g]indol series, 1c,d, and undertook the more detailed study of structure and photo chromic properties of fulgides 1a-d. Results and DiscussionFulgides 1c,d were synthesized analogously to fulgide 1a (Scheme 1) by reacting diethyl isopropylidene suc cinate with the appropriate ketones. 10 Fulgide 1b was obtained following the same scheme by a three step pro cedure with isolation of fulgenate 2b and fulgenic acid 3b, which provided increasing its yield to 60%.

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