Highly Fluorescent Pyreno[2,1-b]pyrroles:  First Syntheses, Crystal Structure, and Intriguing Photophysical Properties

Abstract

A series of pyrrole analogues of benzo[a]pyrene have been synthesized in which pyreno[2,1-b]pyrrole exhibits highly fluorescent properties in solution as well as in crystalline form even possessing strong pi-pi stacking. The pi-stacking-induced fluorescence spectral changes lead to future applications such as molecular recognition feasible upon chemical modification.

Synthesis and Photophysical Studies of a Pyrenylindole and a Phenalenoindole Obtained from Dehydroamino Acid Derivatives – Application as Fluorescent Probes for Biological Systems

“…This result shows that the cyclizations of the parent compounds (Z)‐ 3 and (Z)‐ 4 were successful in producing molecules that are highly fluorescent in environments of different polarities. The Φ F value here obtained for the methyl 9‐methylphenalenoindole‐8‐carboxylate ( 6 ) in ethyl acetate is in total agreement with that reported for a similar compound in the same solvent 3d. In alcohols, especially in methanol, the pyrenylindole 5 exhibits a significant diminution in its Φ F value, probably caused by an increase in singlet→triplet intersystem crossing efficiency through H‐bond interaction, as implied by the positive deviations observable in the Lippert–Mataga plot.…”

“…A more pronounced vibrational structure can be detected in the absorption spectra of compound 6 (Figures 3 and 4), together with a 10 nm red shift in emission relative to the parent compound in cyclohexane 6. Absorption and fluorescence spectra are similar to those reported for similar pyreno[2,1‐ b ]pyrroles,3d as are the absorption and emission maximum values. In polar solvents compound 6 displays a small bathochromic shift in emission, together with an increase in the intensity ratio between the second and the first main peaks (Figures 3 and 4 and Table 1).…”

“…For further extension of pyrene systems, heterocyclic pyrene analogues containing thiophene, pyridine and pyrrole have been prepared 3. Recently, Fang et al described the synthesis and photophysical properties of a series of pyrene[2,1‐ b ]pyrroles 3d. These compounds were prepared by Hemetsberger–Knittel reactions, involving Knoevenagel condensation of a pyrene‐1‐aldehyde and methyl azidoacetate in the presence of sodium methoxide.…”

Synthesis and Photophysical Studies of New Fluorescent Indole Derivatives Obtained from β‐Bromodehydroamino Acids – Interaction with Fluoride Anions

“…[2] All other compounds, which had the indole moiety condensed in an extended aromatic system, presented a structured absorption spectrum in the lower-energy region, as observed for a phenalenoindole [2] and pyrene[2,1-b]pyrrole derivatives. [14] The fluorescence spectra of indoles 14, 17 and 20 were mainly unstructured bands, with large Stokes' shifts and appreciable solvatochromic behaviour, typical of the chargetransfer (CT) character of the excited state, even in nonpolar solvents. The influence of the solvent on the absorption spectral shape was negligible.…”

Synthesis of formyl-thienylpyrroles: versatile building blocks for NLO materials

“…The electron-rich five member aromatic N-substituted pyrrole, furan and thiophene are lithiated at C-2 by direct deprotonation with a lithium-containing base. Several authors have reported the α-lithiation of N-arylpyrroles using different experimental conditions: [49][50][51][52][53][54] Recently, novel methods for site-selective lithiation in α or benzylic positions of 1-(methoxyphenyl), 1-(chlorophenyl), 1-(bromophenyl), 1-(trifluoromethylphenyl) and 1-(methylphenyl)pyrroles have also been reported. [55][56][57][58][59] To our knowledge, the formylation of thienylpyrroles through lithiation followed by quenching with DMF has not been previously reported, and success would open the way to a new range of formyl-functionalized thienylpyrroles.…”