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

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.