P-032

Ivan Halimski

ivan.halimski@ftmc.lt

Jelizaveta Fedotova, Daniil Pashnev, Martynas Talaikis, Andrej Dementjev, Renata Karpicz, Jevgenij Chmeliov, Irmantas Kašalynas, Andžej Urbanovič, Bruno Robert, Patrizia Lamberti, Maksim Shundalau

Center for Physical Sciences and Technology (FTMC), Lithuania

Spectroscopic study of Tetraphenylporphyrin and 2D hexagonal boron nitride van der Waals complex

Porphyrins is a group of organic compounds, which is well-known for their unique electronic and optical properties, e.g., the porphyrin ring is a constituent part of chlorophylls, which are major parts of natural light harvesting complexes. Thus, playing a crucial role in natural photosynthesis, porphyrins are considered as a promising material for artificial photosynthesis as well as for sensing, catalysis and photovoltaics due to their electronic properties and for cancer photodynamic therapy due to long-lived triplet state. Recently, porphyrins were shown to be a good material for information storage. The large scope of present and possible applications of porphyrins encourages the interest in the study of interaction between porphyrins and other materials, especially 2-dimensional (2D) structures, which have their own large scope of applications, i.e., photonics, electronics, bioimaging and biomedicine. Van der Waals (vdW) structures, exhibiting properties of each part on the one hand and enhancing some particular properties on the other, are the promising in this context. Porphyrins vdW structures with graphene-based materials are well-characterized nowadays, but experimental characterization of their complexes with hexagonal boron nitride (hBN), which is structural relative of graphene and isoelectronic to it, but in contrast to graphene is an insulator, but has high chemical and thermal stability as well as thermal conductivity, is rare to date, especially with spectroscopic techniques. 

In this work we provide deep experimental (THz, Raman, FTIR, UV/vis absorption, steady-state fluorescence and decay kinetics) and theoretical (DFT calculations of structures and vibrational and electronic spectra) study of Tetraphenylporphyrin (TPP) and hBN vdW complex. THz spectrum of the complex exhibits additional low-frequency bands assigned to TPP vibrations relative to the hBN surface. Vibrations localized on TPP macrocycle exhibit red shifts in Raman and/or IR spectrum, while those correspond to benzene rings exhibit blue shifts. Electronic spectra (both UV/vis absorbance and fluorescence) exhibit notable red shifts. DFT analysis allows to explain these shifts as a result of uneven charge distribution with partial negative on the TPP macrocycle and partial positive on the benzene rings.

This work was supported by the Horizon Europe FLORIN project (No. 101086142) and the Research Council of Lithuania (Grant No. S-MIP-23-70).