Acid-and hydrogen-bonding-induced switching between 22-and 18-electron conjugation in 2-aminothiazolo [ 4 , 5 c ] porphycenes

2-Aminothiazolo[4,5-c]porphycenes are a novel class of 22-π electron aromatic porphycene derivatives prepared by click reaction of porphycene isothiocyanates with primary and secondary amines with high potential as near-infrared theranostic labels. Herein, the optical and photophysical properties of 2-aminothiazolo[4,5-c]porphycenes have been studied, revealing a strong dependence on hydrogen bond donor solvents and acids. High hydrogen bond donor solvents and acids shift the absorption and fluorescence emission of 2-aminothiazolo[4,5-c]porphycenes to the blue due to a contraction of their aromatic system from 22-π to 18-π electrons. Finally, the aromatic shift has been successfully used to measure the pH using 2-aminothiazoloporphycene-labelled gold nanoclusters, paving the way for the use of these compounds as near infrared pH-sensitive probes.


HFIP effects on the absorption and fluorescence emission spectra of ATAZPo 2
ATAZPo 2 (1.34 μM) was dissolved in 1 mL of methanol and the absorption and fluorescence spectra were collected after the addition of increasing amounts of 1,1,1,3,3,3-hexafluoro-2propanol (HFIP) 5.9 M. Dilution-corrected absorption and fluorescence emission spectra of the titration experiments are presented below (Figure S5).

Excitation spectra of ATAZPo 2 in different solvents
Excitation spectra of ATAZPo 2 were measured in MeOH, HFIP and TFE by observing at 675 and 790 nm.Results are presented in figure S6.

Linear solvation energy relationships
Fitting values of the linear solvation energy relationships with the Kamlet-Taft and Catalan parameters are presented in Table S2.Fittings of Eq.1 and Eq.2 are presented in Figure S7.
Table S2.Fitting values for the dependence of  Max Abs (expressed in cm -1 ) of ATAZPo 2 on the Kamlet-Taft and Catalan solvent parameters.
Agilent 1260 infinity Series chromatograph equipped with photodiode array detector (200-600 nm) and coupled to an Agilent 6130 quadrupole LC/MS.Separation was achieved using a Discovery ® C18 (15m x 4.6 mm, 5µm particle size) column and an ACN:MeOH 85:15 mixture at 1.0 mL/min flow rate.The DAD detector was set at 400 nm matching the Soret band of porphycenes.API-ES positive ionization mode at 80V cone voltage was used.Fragmentations were scanned from 500 to 2500 m/z.Peaks were identified by their characteristic MS fragmentations.

Figure S5 :
Figure S5: Dilution-corrected absorption (top-left) and normalized fluorescence emission spectra (top-right) of ATAZPo 2 in MeOH with increasing volumes of HFIP 5.9 M. Bottom: time-resolved fluorescence emission spectra of ATAZPo 2 in MeOH (red line) and in HFIP (blue).

Figure S7 :
Figure S7: Top: plot of (exp) vs. (calc) for the absorption maxima of ATAZPo 2 in several solvents.A 

Figure S10 :Figure S11 :Figure S12 :
Figure S10: Dilution-corrected absorption (left) and normalized fluorescence emission spectra (right) of TPPo in MeOH (red line) and in MeOH-HFIP (green) and MeOH-HCl (blue) mixtures.The stock concentrations of HFIP and HCl were 5.9 M and 0.05 M respectively.

Figure S13 :
Figure S13: Dilution-corrected absorption (top-left) and normalized fluorescence emission spectra (topright) of ATAZPo 4 in MeOH (red line) and in MeOH-HCl (green) and MeOH-HFIP (blue) mixtures.The stock concentrations of HFIP and HCl were 5.9 M and 12 M respectively.Bottom: time-resolved fluorescence emission spectra of ATAZPo 4 in MeOH (red line) and in HFIP (blue).

Table S1 :
Amounts of citric acid 0.1 M and Na 2 HPO 4 0.2 M to prepare 100 mL of buffer at different