Abstract
The triflic-acid-promoted cyclization of 1-phenyl-3-(pyren-1-yl)-1H-pyrazole-4-carbaldehyde afforded a mixture of 9-phenyl-7,9-dihydropyreno (10,1-fg)indazole and 9-phenylpyreno(10,1-fg)indazole-7(9H)-one, readily separable by column chromatography. Both products contained a rigid six-ringed pyrazoolympicene backbone and exhibited bright fluorescence in chloroform solution and a weak fluorescence in the solid state. DFT and TD DFT calculations revealed that the lowest excited state (S1) of these compounds is populated via HOMO →LUMO π-π * transition. Furthermore, the synthesized compounds behaved as weak bases and their emission spectra showed substantial changes upon protonation. Therefore, they may be of interest for sensing of strongly acidic fluorophore environments.
Highlights
Pyrene hasto been the subject of interest in numerous studies aimed at studies aimed at its modification obtain useful fluorophores for practical applications its to obtain useful fluorophores foroptoelectronics practical applications in various branches in modification various branches of science, ranging from to biology and medicine of science, ranging from optoelectronics to biology and medicine
We found that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbitals (LUMO) of 3 and 4 were mostly localized on the pyrene fragment, with a certain degree of extension on the pyrazole ring and on the carbonyl group
We developed a simple method to synthesize a novel polycyclic N-heterocyclic fluorophore system, pyrazoolympicene, (7,9-dihydropyreno (10,1-fg) indazole), which exhibits intense fluorescence and may be used for sensing strongly acidic environments
Summary
Pyrene is one of the most interesting fluorophores, exhibiting intense and environPyrene is one of the most fluorophores,emission exhibiting(AIE). [3] and forming forming emissive and exciplexes [4,5,6] It can alsocapable be easilyoffunctionemissive excimers and exciplexes [4,5,6].pyrene. Pyrazoles [4,7,10,11,12,13,14] Pyrazoles are another class of small molecule fluorophores exhibiting intense are of small molecule studied fluorophores exhibiting intense and tunableitemission, andanother tunableclass emission, thoroughly in recent years [15,16,17,18,19,20]. We previously previouslyreported reportedthe thesynthesis synthesisand andfluorescent fluorescentproperties propertiesofofpyrazolylpyrenes pyrazolylpyrenes and
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