Substitution Effects of C-C Triple Bonds on Deactivation Processes from the Fluorescent State of Pyrene Studied by Emission and Transient Absorption Measurements

Abstract

Pyrenes substituted with tert-butylethynyl, trimethylsilylethynyl, and trimethylsilylbutadiynyl groups were prepared, and the fluorescence yields (Φ f ), lifetimes, and triplet-triplet absorption were measured in cyclohexane. Upon introduction of the groups possessing triple bond(s) to the pyrene skeleton, the fluorescence rate (k f ) increased. The variation of the terminating groups did not appreciably affect the Φ f and k f values. Increasing the number of the triple bond, the k f values increased by the magnitude of order whereas the Φ f were not varied. The effect of the ethynyl groups on the k f values was rationalized by the StricklerBerg equation considering an increase of the 1 L a transition moment. Triplet-triplet absorption spectra of pyrene derivatives were obtained. The intersystem crossing rates (k isc ) increased upon increasing the number of triple bonds terminated with the trimethylsilyl group whereas those between ethynylpyrenes were independent of the terminating groups. Heavy atom effect failed to rationalize the enhancement of the k isc values upon adding the triple bond to the pyrene moiety.

Photophysical studies of newly derivatized mono substituted phthalocyanines grafted onto silica nanoparticles via click chemistry

“…However both triplet and fluorescence yields increased. It has been reported that the presence of triple bonds enhances the intersystem crossing rate in addition to enhancing fluorescence as stated above [34]. Thus the presence of triple bonds enhances both fluorescence and triplet yields.…”

“…It has been reported that the introduction of groups containing triple bonds increases fluorescence rate [34]. It should also be noted that complexes 1, 2 and 3 are asymmetrical with only one substituent; this implies that any structural change to the Pcs at that point of substitution would also impact on the properties of the newly formed complexes.…”

Observation of the rare chrysene excimer

“…As a result of a reduction in symmetry, the forbidden S 0 / S 1 transition of chrysene becomes allowed, which is reected by an increase in the absorption coefficient (3). 65 The emission maximum of 3 is red-shied by 23 nm compared to chrysene (1). Furthermore, the uorescence quantum yield (F F ) increases from 0.14 for chrysene to 0.41 for the dialkynyl derivative 3 ( Table 2), also as a result of the aforementioned symmetry decrease.…”

Fluorescence properties of 1-(silylethynyl)naphthalenes and 1,4-bis(silylethynyl)naphthalenes in solutions, thin films and solid states

“…Organic substances have some advantages in applications to photoactive materials because they possess unique luminescence properties that are governed by precise molecular designs [1][2][3][4][5][6]. Previously, we and others observed that linking silyl and silylethynyl groups to fused aromatic substances such as naphthalene [7][8][9], anthracene [7,10,11], pyrene [7,[12][13][14][15][16][17] and perylene [18] often increases fluorescence efficiency. However, the highly emissive character of these molecules is limited to highly dilute solutions because fluorescence intensities generally decrease as the concentrations of solutions increase.…”