Complex Formation Equilibria between Ag(I) and Thioureas in Propan-2-ol

Abstract

(EnTu) in propan-2-ol as solvent medium have been investigated by potentiometry within the temperature range 10 ∘ C-40 ∘ C and self-determined ionic medium by (AgNO 3 ) concentration range 6.36 ⋅ 10 −6 -3.83 ⋅ 10 −5 m⋅dm −3 (no background electrolyte added). The experimental results can be interpreted with the stepwise formation of tris-coordinated complexes AgL ( = 1-3; hereafter charge is omitted). The stability constants log and the standard thermodynamic changes in enthalpy (Δ ∘ ) and entropy (Δ ∘ ) for overall complex formation reactions Ag(I) + L = AgL ( = 1-3) have been evaluated. The reactions are exothermic in nature and entropy disfavored for all the investigated ligands. The standard enthalpy and entropy changes for the stepwise reactionsThe stepwise enthalpy are mutually linearly related to the corresponding entropy changes with isoequilibrium temperatures iso = 285, 305, and 363 K for = 1, 2, or 3 respectively.

NanoPOP: Solution-Processable Fluorescent Porous Organic Polymer for Highly Sensitive, Selective, and Fast Naked Eye Detection of Mercury

“…We expect the size complementarity and soft acid/base pairing of Hg 2+ with thiosemicarbazide strongly drive selective binding. The mercury ion is comparatively much larger (Hg 2+ radius = 102 pm, Cu 2+ 73 pm, Fe 3+ 55 pm, Cd 2+ 95 pm, Cr 3+ 62 pm, Co 2+ 75 pm), and its equilibrium constant of the thiourea–Hg 2+ (lgβ = 22.1) complex is significantly higher than other metal cations, including comparatively soft Ag + (lgβ = 9.7), Cd 2+ (lgβ = 4.3), Cu 2+ (lgβ = 10.4), and Pb 2+ (lgβ = 0.5), indicative of its particularly strong bonding with thiosemicarbazide. − We further measured the Hg 2+ sensing performance of TPA-POP-TSC under competitive environment and found that the sensitivity toward Hg 2+ was barely influenced by other common metal cations that coexist in the solution, such as Na + , K + , Ca 2+ , Ba 2+ , Fe 3+ , Cr 3+ , Co 2+ , Pb 2+ , Cd 2+ , Ag + , and Cu 2+ (Figure S8). We also tested the stability of the TPA-POP-TSC nanoPOP at different pH values.…”