Herein, we show that the Zn complex of 1,4,8,11,15,18,22,28-octakis(butoxy)phthalocyanine exhibits solvatochromism and characterize the corresponding visible color changes. In particular, we reveal that although the variation of the solvent-dependent position of the Q band is relatively small (~100 nm), the solution colors change from red to yellow and green depending on the composition of the solvent mixture. Moreover, the above Q band was located at the border between the visible and near-IR regions, [Formula: see text]. its red shift could not be directly recognized by the human naked eye. Substituents on oxygen atoms were shown to influence phthalocyanine aggregation and thus affect near-IR absorption, with the observed near-IR solvatochromism providing a new strategy of color change in response to weak external stimuli.

A simple phthalocyanine zinc complex exhibits a visible color change in response to weak external stimuli, i.e., changes in solvent and temperature.