Supporting Information for
Peripheral Step-Wise Degradation of a Porphyrin J-Aggregates Ilaria Occhiuto, Giovanna De Luca, Mariachiara Trapani, Luigi Monsù Scolaro* and Robert F. Pasternack
Materials and methods. The porphyrin 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H2TPPS4) was obtained from Frontier Scientific as the tetrasodium salt. CuSO4·5 H2O, Na2SO4·10 H2O and sulfuric acid (ACS grade) were purchased from Aldrich Co. and used as received. Milli-Q water was used for all solutions. A concentrated stock solution of H2TPPS4 was prepared daily and the concentration determined using ε412 = 5.33 × 105 M-1cm-1 at the Soret maximum in water.[1] UV/Vis extinction spectra were recorded on a Agilent 8453 diode array spectrophotometer using 1 cm path-length quartz cells, and reported in absorbance units (abs. units). Resonance Light scattering (RLS) experiments were performed on a Jasco FP-750 spectrofluorimeter, adopting a synchronous scan protocol with right angle geometry.[2] RLS spectra were not corrected for the absorption of the samples. Kinetic runs were initiated in a quartz cell placed in the thermostated compartment (T = 298 K) of the spectrophotometer following one of several different protocols: (i) by adding a known volume of concentrated stock solution of H2TPPS4 (300 µM) to a pre-thermostated aqueous solution of CuSO4 (0.05 – 0.8 M) and H2SO4 (1.5 × 10-3 M) (porphyrin last protocol); (ii) by adding concentrated stock solutions of CuSO4 (final concentrations: 0.05 – 0.8 M) to a pre-acidified solution of H2TPPS4 (3 µM) in H2SO4 1.5 × 10-3 M (porphyrin first protocol); (iii) by mixing equal volumes of a solution containing CuSO4 , Na2SO4 and H2SO4 with a solution containing a preformed J-aggregate obtained by reacting H2TPPS4 in H2SO4 with Na2SO4 (final exp. conditions: SI1
[H2TPPS4]= 3 µM; [CuSO4] = 0.075-0.3 M; IS = 2 M, by addition of Na2SO4; [H2SO4] = 1.5 × 10-3 M). The pseudo-first order kinetics observed using protocol (ii) were analyzed by fitting the absorbance data to the equation: At = Ai + (Ao – Ai) exp (-kobs t), where At, Ai and Ao are the absorbance at time t, at the beginning and after completion of the reaction and kobs is the pseudo-first order kinetic constant (s-1). The pseudo-zero order kinetics observed using protocols (i) and (iii) were analyzed by a linear fit of the extinction data collected at 490 nm after normalization to unity. The concentration of aggregated monomers at any time has been obtained by subtracting the amount of diacid or metallated porphyrin (determined using literature values of the extinction coefficients)[1,3] to the initial H2TPPS4 concentration, obtaining pseudo-zero order kinetic constants (M–1 s–1) as slopes.
[1] Ribò, J. M.; Crusats, J.; Farrera, J. A.; Valero M. L. J. Chem. Soc., Chem. Commun., 1994, 681. [2] Pasternack, R. F.; Collings, P. J. Science 1995, 269, 935. [3] Hambright, P. In The Porphyrin Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic Press: New York, 2000; Vol. 3, p 129-210.
SI2
Extinction (abs. unit)
1.0
0.8
434 490 0.6
0.4
0
100
200
300
400
t (s) Figure SI1. Extinction changes at 490 nm (red circles) and 434 nm (black squares) for the aggregation of H4TPPS4 adding the porphyrin as last reagent and using Zn(II) sulfate as nonmetallating salt. Experimental conditions: [H4TPPS4] = 3 μM; [H2SO4] = 1.5 × 10-3 M; [ZnSO4] = 0.3M.
SI3
Figure SI2. Values of the slope obtained from a linear fit of the extinction changes at 490 nm during copper(II) insertion in H4TPPS4 as function of added CuSO4 at 298 K. Experimental conditions: [H4TPPS4] = 3 μM; [H2SO4] = 1.5 × 10-3 M; [CuSO4]: 0.05 - 0.8 M; T = 298 K; porphyrin added last.
SI4
Figure SI3. Linear regimes of the extinction changes at 490 nm for the copper(II) insertion in the J-aggregated porphyrin as a function of CuSO4 concentration at 298 K. An offset has been applied to the data to facilitate a visual comparison. to Experimental conditions: [H4TPPS4] = 3 μM; [H2SO4] = 1.5 × 10-3 M; [CuSO4] = 0.05 (open circles), 0.15 (black squares), 0.3 (black circles), 0.6 (open diamonds), 0.8 M (open squares); porphyrin added last.
SI5
