pH-Sensitive Fluorescence Lifetime Molecular Probes Based on Functionalized Tristyrylbenzene

Abstract

The dependence of the fluorescence on pH for two 1,3,5-tristyrylbenzenes decorated with polyamine (compound 1) and poly­(amidoamine) (compound 2) chains at the periphery was investigated. The highest fluorescence intensities were observed under acidic conditions because electrostatic repulsions between positively charged molecules reduce the fluorescence quenching. The slopes observed in the fluorescence pH titration curves were associated with deprotonation of the different types of amine groups, which results in quenching by photoinduced electron transfer and aggregation processes. The linear dependence of fluorescence lifetime observed for different pH ranges is a valuable property for applications in the field of fluorescence lifetime sensors and imaging microscopy. The influence of the pH and the peripheral chains on the aggregation processes was also analyzed by absorption and emission spectroscopy, dynamic light scattering measurements, and transmission electron microscopy. For compound 1, bands associated with the formation of aggregates were detected along with micrometric aggregates surrounded by fibers with lattice fringes typical of columnar mesophases. For compound 2, which contains longer peripheral chains with a higher degree of branching, aggregates with lower internal order were observed. In this case, the peripheral chains hindered aggregation by π-stacking although the amine groups did allow hydrogen bonding.

Understanding the Driving Mechanisms of Enhanced Luminescence Emission of Oligo(styryl)benzenes and Tri(styryl)‐s‐triazine

“…Consequently, the cross‐shaped core of compound 2 favors the formation of ordered structures with narrower lattice fringes than that in the case of star‐shaped molecules. A similar observation was made for the derivatives of 1 and 2 with −CH 2 −NH−(CH 2 ) 2 −NH 2 side chains instead of −CH 2 −(CH 2 ) 5 −OH, that is, the lattice‐fringe periodicity decreases from 0.34 to 0.20 nm for derivatives of 1 and 2 , respectively . Accordingly, the larger conjugated core of 2 seems to favor π‐stacking interactions, approximating molecules in the supramolecular structure, with dramatic effects on the luminescence emission properties because Φ F drops by up to 1.7 % in the solid state (see Figure S10 and Table S2 in the Supporting Information).…”

“…As imilar observation was made for the derivatives of 1 and 2 with ÀCH 2 À NHÀ(CH 2 ) 2 ÀNH 2 side chains instead of ÀCH 2 À(CH 2 ) 5 ÀOH, that is, the lattice-fringe periodicity decreases from 0.34 to 0.20 nm for derivatives of 1 and 2,r espectively. [69,70] Accordingly,t he larger conjugated core of 2 seems to favor p-stacking interactions, approximating molecules in the supramolecular structure, with dramatic effects on the luminescence emission properties be-cause F F drops by up to 1.7 %inthe solid state (see Figure S10 and Ta ble S2 in the Supporting Information). On the contrary,a high quantum yield of 50.0 % [43] was reported for compound 1; this value is associatedw ith Xa ggregation, which is the most effective molecular arrangement for preventing quenching in the solid state.…”

Combined Theoretical and Experimental Study on Intramolecular Charge Transfer Processes in Star-Shaped Conjugated Molecules

“…15 Note that light-emitting properties of tristyrylbenzene derivatives in solution or solid state, would strongly depend on supramolecular aggregation, thus modulating their possible technological and sensing applications as it has been recently disclosed in last years. [16][17][18][19] Concurrently, Coya et al demonstrated that tristyrylbenzene derivatives can be employed in the fabrication of OLEDs with satisfactory performance. 20,21 In this work, we have thus synthetized two novel molecules based on the (9H-carbazol-9-yl)styryl moieties connected to benzene, an electron donating core, and to s-triazine, a strong withdrawing core, compounds 1 and 2 in Scheme 1, with the aim of study their photophysical properties when a -bridge is preserved as meta-arrangement and the nature of the core is changed.…”

Functionalized CdSe/ZnS Quantum Dots for Intracellular pH Measurements by Fluorescence Lifetime Imaging Microscopy

“…Fluorescence lifetime imaging microscopy (FLIM) is, at the same time, an imaging technique and an absolute measurement method that allows obtaining reproducible pH values and concentrations of other biological analytes. ,, The main advantages of this technique over conventional FIM arise from its insensitivity to fluorophore concentration, excitation source intensity, and duration of light exposure, among others. ,, Currently, many efforts are being devoted to developing new fluorescent compounds with applicability as pH-sensitive probes for bioimaging applications . For instance, some small organic molecules such as hexamethylindo-tricarbocyanine (HITC) and derivatives of fluorescein (BCECF or BCPCF), , 1,3,5-tris­(styryl)­benzene, or perylene bisimide , have a potential use as fluorescence pH-sensitive probes. Nevertheless, the short fluorescence lifetimes typically associated with small organic molecules are comparable to the cellular autofluorescence lifetime (1–2 ns), limiting their application in FLIM for quantitative intracellular measurements.…”