Experimental and theoretical investigation of fluorescence solvatochromism of dialkoxyphenyl-pyrene molecules

Abstract

We investigated the fluorescence properties of dialkoxyphenyl-pyrene molecules experimentally as well as theoretically. Our experiments confirmed fluorescence solvatochromism in 2,5-dimethoxyphenyl-pyrene and, in contrast there was no significant solvent-effect on the emission properties of the isomers, 3,5- and 2,6-dimethoxyphenyl-pyrene. This clear difference in the solvent-dependence would reflect the difference in character of the excited-state between the isomers, which differ only in the substitution positions of the two methoxy groups. The positional effects of the di-substituted molecules are successfully explained theoretically by the topologies of the highest occupied molecular orbital of the phenyl group that are governed by the relative positions of the two substituents, though it is somewhat contradictory to the meta-effect for the mono-substituted molecules. Theoretical calculations were also used to analyze the character of the excited states; 2,5-dimethoxyphenyl-pyrene alone exhibited an intramolecular charge transfer character for the excited state, which was responsible for the solvatochromism effect. The dynamics of the excited states were analyzed using time-resolved fluorescence measurements, in which a characteristic increase of the fluorescence intensity was observed for 2,5-dialkoxyphenyl-pyrene; this observation was supported by the theoretical calculations as well.

The endeavor of vibration-induced emission (VIE) for dynamic emissions

“…1a, the dual bands of an individual uorophore can generally be divided into small (normal) and large (abnormal) Stokes-shied emissions. [11][12][13] The overlap of the normal short-wavelength emission with the lowest-lying absorption band originates from the initial emissive state near the Franck-Condon excited state, while the red-shied emission far from the absorption band arises from the structurally transformed emissive state formed by additional excited-state transformations, such as enhanced charge transfer, [14][15][16][17][18][19] energy transfer, [20][21][22][23][24][25] complex formation, [26][27][28][29][30][31] and structural and/or conformational changes. Due to the signicant congurational and/or structural changes in the excited state, the ratio of short-and long-wavelength bands can be manipulated in a controllable and dynamic manner, activating unprecedented multi-colour luminescence.…”

Ab initio study on the excited states of pyrene and its derivatives using multi-reference perturbation theory methods

“…[56][57][58] Thus, the excited states of pyrene and its derivatives have been vigorously investigated and still continue to attract much interest from scientists with respect to both fundamental studies and practical applications. [59][60][61][62][63][64] Pyrene has two important excited states, 1 L a and 1 L b in Platt's notation. 65 These excited states are closely relevant to the absorption and uorescence emission behavior of pyrene.…”

Palladium‐catalysed room‐temperature Suzuki–Miyaura coupling in water extract of pomegranate ash, a bio‐derived sustainable and renewable medium

“…Biaryls and their heteroatom analogues are among the most important structural features of biologically active natural products, pharmaceuticals and agrochemicals . These motifs also serve as ligands in catalysts, functional materials, conductive polymers and theoretically interesting molecules . Due to the wide‐ranging usefulness of biaryls, transition‐metal‐mediated methods such as SMC, Stille, Negishi, Kumada and Hiyama reactions are realized by cross‐coupling of haloarenes with organometallic partners.…”

“…[5][6][7][8] These motifs also serve as ligands in catalysts, functional materials, conductive polymers and theoretically interesting molecules. [9][10][11][12] Due to the wide-ranging usefulness of biaryls, transition-metalmediated methods such as SMC, [13,14] Stille, [15,16] Negishi, [17] Kumada [18] and Hiyama [19,20] reactions are realized by cross-coupling of haloarenes with organometallic partners. Among these protocols, SMC is the most productive in synthesizing biaryls and offers several advantages like ready availability of substrates, use of safe and high-stability arylboronic acids, large functional group tolerance and ease of handling.…”