<p> Supporting Information</p><p>- Ratiometric fluorescence chemosensors for HSO4 ion based on pyrrole-substituted salicylimine based Zn2+ complex: nanomolar detection</p><p>Umesh Fegadeac, Jitendra Bhosalea, Hemant Sharmab, Narinder Singhb, Ratnamala Bendrea, Anil Kuwara* aSchool of Chemical Sciences, North Maharashtra University, Jalgaon, 425001 (MS) India. bDepartment of Chemistry, Indian Institute of Technology, Ropar, Rupanagar, Punjab, India *Corresponding author. E-mail addresses: [email protected], [email protected]. ------Stoichiometry of complexations</p><p>- To determine the binding stoichiometry between receptor 4 and HSO4 the continuous variation method was used. Fig. S7 shows the Job’s plot of the fluorescence intensity of free receptor 4 and the intensity of the system with the molar fraction of the host {[H]/([H]+[G])} for a series of solutions, in which the total concentration of host and guest was constant, with the molar fraction of host continuously varying. The results show that the formation of a 1:1 (Host: Guest) complex. Using the</p><p>2 equation: [G]tot = a/2K(1-a) [H]tot + a[H]tot/2, where [G]tot is total concentration of guest, [H]tot is the total concentration of host, a = (I- I0)/(Ii- I0) with I being the fluorescent intensity at a particular guest ion</p><p> concentration while I0 and Ii are the intensities at zero and infinite guest concentrations, respectively.</p><p>Figure S1. 1:1 Stoichiometry of the host guest relationship realised from the Job’s plot for receptor 4. The Benesi-Hildebrand Plot Using the Benesi-Hildebrand Plot (Eq.1) methodologies. We made the calculation of association constant K. </p><p>1/F-F0 = 1/(F∞ - F0)K[G] + 1/(F∞-F0) (Eq.1)</p><p>Figure S2. Benesi-Hildebrand Plot receptor 4 (adjusted equation: 1/F-F0 = -5.189+20235/[G], R=0.980) at the K value 38997 M-1.</p><p>The Stern–Volmer quenching constant The quenching can be mathematically expressed by the Stern–Volmer Eq. (2), which allows for calculating quenching constants. F0/F = = 1 + kq τ0 [Q] = 1 + Ksv[Q] (2)</p><p>Where F0 and F are the fluorescence intensities in the absence and presence of the quencher, kq is the bimolecular quenching constant, τ0 is the lifetime of the fluorescence in the absence of the quencher [Q] is the concentration of the quencher, and Ksv is the Stern–Volmer quenching constant. In the presence of a quencher (Lns), the fluorescence intensity is reduced from F0 to F. The ratio (F0/F) is directly proportional to the quencher concentration [Q]. Evidently:</p><p>Ksv = kq τ0 (3)</p><p>F0/F = 1 + Ksv[Q] (4)</p><p>According to Eq, a plot of F0/F versus [Q] shows a linear graph with an intercept of 4 and a slope of Ksv. - A typical plot of F0/F versus HSO4 concentration is shown in Fig S3.</p><p>- Figure S3. Stern–Volmer plots for titrations of receptor 4 with different concentrations of HSO4 anion.</p>