pH Dependent Self‐Assembly of Single‐Pyrene‐Armed Calix[4]arene: Modulation and Complexation with p‐Sulfonatocalix[6]arene

The photophysical behaviour of a single pyrene substituted calix[4]arene derivative (MPCX4) has been investigated, as a function of pH, using steady state fluorescence and time‐resolved emission spectroscopic techniques. An interesting dimer emission band has been observed exclusively in the alkaline solution (pH > 8) which has been attributed to the hydrophobic and stacking interaction between the pyrene moieties of the adjacent MPCX4 molecule. The self‐assembled MPCX4 is disrupted by the introduction of another calixarene based host, p‐sulfonatocalix[6]arene (SCX6), which eventually leads to the 1:1 complex formation between MPCX4 and SCX6, which is further characterised by 1H NMR, FT‐IR and HR‐MS techniques. This complexation between MPCX4 and SCX6 also leads to the modulation of the prototropic equilibrium of MPCX4. A single pyrene substituted calix[4]arene derivative (MPCX4) undergoes dimerization at alkaline pH (pH > 8) with the appearance of a distinct emission band for dimer species, which has been attributed to the hydrophobic and stacking interaction between the pyrene moieties of the adjacent MPCX4 molecule. The self‐assembled MPCX4 is disrupted by the introduction of another calixarene based host, p‐sulfonatocalix[6]arene (SCX6), which eventually leads to the complexation between MPCX4 and SCX6.