Photophysical Properties of Coumarin 1 in Bile Salt Aggregates: An Insight into the Role of Bile Salt Structure on the Aggregation Behavior

Abstract

The photophysical behavior of Coumarin 1 (Cou1), a well-known 7-aminocoumarin derivative, is very sensitive to the microenvironment in which it resides. In the present study, the effect of six bile salt variants on the photophysical behavior of Cou1 has been investigated. Dihydroxy (deoxycholates) as well as trihydroxy (cholates) bile salts with conjugated and unconjugated side chains have been chosen to get insight into the role of bile salt structure on the microenvironment of Cou1. Cou1 photophysics was found to be extremely sensitive to the aggregation process of the bile salt variants. The reduced polarity of the micellar environment stabilizes the planar intramolecular charge transferred state of Cou1, resulting in significant modulation in its photophysics in the bile salt media. The changes in the fluorescence parameters such as fluorescence intensity, emission energy, fluorescence quantum yield, anisotropy, and lifetime of Cou1 reveal that there is a distinct difference in the aggregation behavior of deoxycholates from that of cholates. The deoxycholates form micelles more or less critically similar to those of conventional surfactants, whereas the cholates self-assemble rather noncritically over a wide concentration range, thus signifying the vital role of the extra hydroxyl group in the aggregation pattern of trihydroxy bile salts. The conjugated bile salts are found to provide a relatively more compact, rigid, and hydrophobic microenvironment to Cou1 as compared to their unconjugated counterparts. Considering the significant modulation in the photophysical properties of Cou1, it has been employed as a molecular reporter for monitoring the aggregation process of bile salt variants and important information could be obtained about the effect of bile salt structure on the aggregation pattern and also about the micellar properties.

MOF-Derived Hollow Tubular In2O3/MIIIn2S4 (MII: Ca, Mn, and Zn) Heterostructures: Synergetic Charge-Transfer Mechanism and Excellent Photocatalytic Performance to Boost Activation of Small Atmospheric Molecules

“…Moreover, the excited-state lifetime decay profile of bare HT-In 2 O 3 together with HT-In 2 O 3 /M II In 2 S 4 (1:1) heterostructures is probed by using a time-resolved photoluminescence (TRPL) technique (Figure c). The decay profiles are fitted with the biexponential decay expression presented in eq , and the average lifetime is calculated using the expression presented in eq Here, A i and τ i represent the intensity and individual lifetime values obtained from the exponential equation.…”

“…The decay profiles are fitted with the biexponential decay expression presented in eq 1, and the average lifetime is calculated using the expression presented in eq 2. 49 (1)…”

Synergistic dynamics of photoionization and photoinduced electron transfer probed by laser flash photolysis and ultrafast fluorescence spectroscopy

“…In this work, the excitedstate dynamics of coumarin 450 (C450, Scheme 1) were investigated by a combination of laser flash photolysis with steady-state and time-resolved fluorescence spectroscopy to gain more insight into the dynamics of photoinduced processes. In general, coumarin dyes are utilized as a fluorescent probe to investigating several physiochemical processes and the properties of microenvironments in heterogeneous media [23,25,27,[32][33][34][35]. Previously, we have investigated the photoionization and solvation dynamics of coumarin 307 (C307) in micelles in which the radicalion pair recombination dynamics were probed using timedependent Stokes shift in combination with time-resolved transient absorption studies [18].…”

Encapsulation and release of non-fluorescent crystal violet confined in bile-salt aggregates

“…This properties of bile-salts can be exploited in the medicinal eld. [1][2][3][4][5][6][7] Bile-salts (Scheme 1) are easily recognized by its fourmembered hydrocarbon core known as "cyclopentanoperhydrophenanthrene". All the natural as well as synthetic steroids are derivatives of this core.…”

“…making them very cheap, nontoxic and efficacious drug carrier vehicle for medical applications. 5,6 Bile salts have tendency to form micelles and aggregation behaviour beyond their critical micelle concentration (CMC). Bile salt aggregates are typically used as supramolecular host molecules.…”