Low-symmetry A3B type pentachlorocyclotriphosphazene substituted phthalocyanine with improved nonlinear optical properties: Synthesis, spectroscopic and ab initio/(TD)DFT study

In the present work, we performed structural modification of 2-hydroxy-9(10),16(17),23(24)-tri-tert-butyl-29H,31H-phthalocyanine (1) using phosphonitrilic chloride trimer (hexachlorocyclotriphosphazene). Despite the wide availability of phosphazenes and their derivatives, including polymeric materials based on them, this is one of the few examples of the introduction of an active phosphazene cycle into the structure of a macroheterocyclic compound. Target free-base ligand 2 was characterized by the MALDI-TOF/TOF mass spectrometry, as well as the 1H, 31P NMR and FT-IR spectroscopy. Also, a tendency towards H-aggregation in polar media was demonstrated. Theoretical calculations based on time-dependent Hartree-Fock approach for nonlinear optical properties have allowed revealing a self-defocusing effect in the case of phthalocyanine 2, which makes it an interesting candidate for all-optical switching, two-photon imaging, and optical power limiting applications.