Long-lived photoinduced charge separation in carbazole–pyrene–viologen system incorporated in Langmuir–Blodgett films of substituted diazacrown ethers

Role of microenvironment in the mixed Langmuir–Blodgett films

“…CA and its derivatives are also of great interest to the spectroscopists owing to their unique photo-physical characteristics like an intense and well characterized absorption and fluorescence spectra [5][6]. Owing to their excellent optical and electronic properties, various amphiphilic derivatives of carbazole were synthesized and studied in the Langmuir-Blodgett films [5][6][7][8][9][10][11][12][13]. However the synthesis of these amphiphilic carbazole derivatives and their purification are extremely difficult.…”

Ethynylpyrene Linked Benzocrown Ethers as Fluorescent Sensors for Metal Ions

“…In the case of 15-crown-5, response to Mg 2+ ion is found to be excellent. So far, many pyrene-crown ether based chemosensors have been developed and they selectively detect Li + (18), Na + (18,35,38), K + (17,22,28,33,(37)(38)(39)41,42,50), Cs + (38), Ca 2+ (31,34), Sr 2+ (21,31), Ba 2+ (28,43), Gd 3+ (46), Mn 2+ (19), Fe 2+ (20), Cu 2+ (40), Ag + (25), Zn 2+ (24,29), Hg 2+ (20, 26,27), Pb 2+ (32,39), NH 4 + (23) and methyl viologen (30,47,48) ions. However, to the best of our knowledge, Mg 2+ -selective chemosensors based on pyrene and crown ethers are unprecedent.…”

“…In the third group, sensing is based on monomer/excimer emission switching (28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43) induced by changes in spatial distances between two pyrene moieties. Moreover, the pyrene and crown ether groups in these types of sensors are normally linked by flexible chains, such as methylene (17)(18)(19)(20)(21)28,29,(44)(45)(46), ether (30,47,48), oligoethylene glycol (31)(32)(33)(34), ester (22), amine (49), amide (25)(26)(27)(35)(36)(37)(38)(39)(40)(41)50), imine (23), triazole (51), sulfoxide (24) and DNA…”

“…Pyrene and its derivatives are often used as fluorescent materials owing to several advantageous features including photochemical inertness, dual fluorescence (monomer/excimer) and high emission quantum yield . Thus far, many substances containing linked pyrenes and crown ethers have been designed to serve as fluorescent metal ion sensors . These types of sensors can be roughly categorized into three groups based on their response to metal ions.…”

“…In the third group, sensing is based on monomer/excimer emission switching induced by changes in spatial distances between two pyrene moieties. Moreover, the pyrene and crown ether groups in these types of sensors are normally linked by flexible chains, such as methylene (), ether , oligoethylene glycol , ester , amine , amide (), imine , triazole , sulfoxide and DNA units. As a consequence, decreases in fluorescence efficiencies by thermal (nonradiative) decay pathways arising from molecular motion are inevitable.…”