Synthesis and Photoacoustic Characterization of Amphiphilic Ni(II) Phthalocyanines as Calorimetric References

This work describes the synthesis and photophysical characterization of a series comprised by four nonionic yet amphiphilic octa‐substituted Ni(II) phthalocyanines (NiPc) with peripheral or proximal decoration. The combination of MALDI–TOF mass spectrometry, ¹ H‐NMR, ¹³ C‐NMR, and UV–vis spectroscopy enabled an unambiguous structural elucidation. Notably, these NiPcs are soluble in both polar organic solvents and aqueous media. Since these complexes exhibit near‐infrared absorption ( λ _max  = 650–800 nm), are non‐emissive, and display remarkable chemical stability, a new experimental setup was developed to investigate their photoacoustic efficiency by combining transient absorption spectroscopy and laser‐induced photoacoustic calorimetry. This approach revealed that all complexes are equally suited and stable as photoacoustic references in both aqueous and organic media.