Absorption and Fluorescence Features of an Amphiphilic meso-Pyrimidinylcorrole: Experimental Study and Quantum Chemical Calculations

Abstract

Corroles are emerging as an important class of macrocycles with numerous applications because of their peculiar photophysical and metal chelating properties. meso-Pyrimidinylcorroles are easily deprotonated in certain solvents, which changes their absorption and emission spectra as well as their accessible supramolecular structures. To enable control over the formation of supramolecular structures, the dominant corrole species, i.e., the deprotonated form or one of the two NH-tautomers, needs to be identified. Therefore, we focus in the present article on the determination of the UV-vis spectroscopic properties of the free-base NH-tautomers and the deprotonated form of a new amphiphilic meso-pyrimidinylcorrole that can assemble to supramolecular structures at heterointerfaces as utilized in the Langmuir-Blodgett and liquid-liquid interface precipitation techniques. After quantification of the polarities of the free-base NH-tautomers and the deprotonated form by means of quantum chemically derived electrostatic potential distributions at the corroles' van der Waals surfaces, the preferential stabilization of (some of) the considered species in solvents of different polarity is identified by means of absorption spectroscopy. For the solutions with complex mixtures of species, we applied fluorescence excitation spectroscopy to estimate the relative weights of the individual corrole species. This technique might also be applied to identify dominating species in molecularly thin films directly on the subphase' surface of Langmuir-Blodgett troughs. Supported by quantum chemical calculations we were able to differentiate between the spectral signatures of the individual NH-tautomers by means of fluorescence excitation spectroscopy.

Arylic versus Alkylic—Hydrophobic Linkers Determine the Supramolecular Structure and Optoelectronic Properties of Tripodal Amphiphilic Push–Pull Thiazoles

“…The absorption maximum slightly shifts from 448 nm in toluene to 464 nm in dimethyl sulfoxide (DMSO). This red shift upon increasing the solvent polarity from toluene to DMSO (see Table ) points to an increased dipole moment in the first excited state (S 1 state) as compared to the ground state, as also corroborated by the increasing Stokes shift shown in Figure . The amplitude of the maximum of the extinction coefficients does not change significantly upon varying solvent polarity.…”

Langmuir–Blodgett Films of Diketopyrrolopyrroles with Tunable Amphiphilicity

“…The UV–vis absorption and fluorescence spectra of the dissolved dyes are characterized by single dominating electronic transitions (λ­( A max ) of A , B , C : 595, 588, 660 nm, λ­(Fl max ): 607, 597, 692 nm) that show pronounced vibronic progression. According to the charge difference densities between S 0 and S 1 excited states derived from our time-dependent density functional theory (TDDFT) calculations ,, shown in Figure , the dominant electronic transitions feature a ππ* character and are centered at the diketopyrrolopyrroles. The very small Stokes shift ( A , B , C : ν ̃ = 333.2, 256.4, 701.5 cm -1 ) indicates only minute structural relaxation after photoexcitation of the planar and rigid chromophores.…”

Embedding an Amphiphilic 4-Hydroxy Thiazole Dye in Langmuir Matrices: Studying Miscibilities with Arylic and Alkylic Matrix Amphiphiles via Langmuir Isotherms and Photo-induced Force Microscopy

“…As an amphiphilic dye, we choose a 4-hydroxy thiazole − (see Figure ), whose 4-hydroxy position is connected to a hydrophilic carboxylic acid moiety via a flexible decyl chain that adds motional degrees of freedom during supramolecular structure formation in Langmuir layers. ,, This 4-hydroxy thiazole derivative, labeled 10 because of the number of CH 2 groups constituting the linker, hence consists of a chromophore bearing three aromatic rings and an alkylic acid. Following the “like dissolves like” rule, which can be explained via analysis of electrostatic surface potentials − and finally the “conductor-like screening model for real solutions”, − fatty acids or linear aromatic amphiphiles are chemically similar to the alkyl chain and the chromophore of 10 , respectively. Consequently, they appear to be suitable candidates for Langmuir matrix molecules as they resemble the aforementioned individual building blocks of the amphiphilic thiazole shown in Figure .…”