Synthesis, crystal structures, and optical properties of the π-π interacting pyrrolo[2,3-b]quinoxaline derivatives containing 2-thienyl substituent

Three (E/Z)-diastereoisomers, based on pyrrolo[2,3-b]quinoxaline system as fluorophore and containing: 2-thienylmethyl (1), bis(2-thienylmethyl)-2-aminoethyl (3a), bis(2-thienylmethyl)-3-aminopropyl (3b) groups as substituents, were synthesized and characterized by X-ray structural analysis, PXRD, N...

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Bibliographic Details
Published in:Journal of molecular structure 2017-10, Vol.1146, p.337-346
Main Authors: Goszczycki, Piotr, Stadnicka, Katarzyna, Brela, Mateusz Z., Grolik, Jarosław, Ostrowska, Katarzyna
Format: Article
Language:English
Subjects:
Aggregation induced emission enhancement
Non-covalent interaction
Pyrroloquinoxaline
Single-crystal X-ray analysis
Thienyl group
π-Dimers
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Summary:Three (E/Z)-diastereoisomers, based on pyrrolo[2,3-b]quinoxaline system as fluorophore and containing: 2-thienylmethyl (1), bis(2-thienylmethyl)-2-aminoethyl (3a), bis(2-thienylmethyl)-3-aminopropyl (3b) groups as substituents, were synthesized and characterized by X-ray structural analysis, PXRD, NMR, UV–Vis as well as fluorescence. These compounds are non-fluorescent in acetonitrile solution, however, they exhibit aggregation induced emission enhancement (AIEE) upon water addition and in solid state. X-ray structural analysis revealed that molecules with 2-thienylmethyl and bis(2-thienylmethyl)-2-aminoethyl groups form dimers and π-stacks through π-π interactions between anitiparallel oriented pyrroloquinoxaline cores with interplanar distances 3.45 Å and 3.20 Å, respectively. Conformation of bis(2-thienylmethyl)-3-aminopropyl group is imposed by incorporated DMSO-d6 solvent molecule and weak intermolecular S-π and CH-π interactions, that prevents π-π interaction between fluorophore cores. The correlation between crystal structure and fluorescent properties of synthesized molecules was discussed. The DFT calculations were performed to rationalize the differences between considered systems. [Display omitted] •SC-XRD analysis indicates formation of monomers, dimers, and π-stacks.•DFT calculations show the influence of thiophene rings on the charge distribution.•The S-π, CH-π, and π-π interactions in crystals affect fluorescent properties.
ISSN:0022-2860
1872-8014
DOI:10.1016/j.molstruc.2017.06.008