Aggregation of Photosensitisers: the role of dispersion and solvation on dimer formation energetics

F. Bettanin, T.A.C. Fontinelles, C.D. Maciel, L.G. Dias, M.D. CoutinhoNeto,

P. Homem-de-Mello

SUPPORTING INFORMATION

Molecular dynamics was used as a tool to investigate the behavior of dimers in solution. Emphasis was placed in the orientation dynamics between monomers. To this aim, a vector was defined whose endpoints were set connecting the hydrogen atoms bound to the pyrrole ring. The left panel in Figure SI1 shows the angular distribution between the vectors for each monomer with the most probable configurations for Pcbeing 10, 45 and 90 degrees. For MB, a vector was defined connectingthe nitrogen and sulphuratoms of the molecule central ring. The angular distribution obtained for MB shows a clear preference for anti-parallel dimers similar to the MBanticonformation (see Figure 2).

Figure SI1. Angle distribution between photosensitizers molecules in dimeric form in aqueous solution. At left we have the angle distribution of MB (blue)and at right Pc (red).

Table SI1. Solvation free energy contributions obtained in water, ethanol and diethylether for the Pc45 dimer configuration at BLYP/DGDZVP level

CPCM / SMD
Dimer / Monomer / Dimer / Monomer
Water / G0gsolv,el/ kcal mol-1 / -18.1 / -11.1 / -26.1 / -18.0
G0gsolv,cd/ kcal mol-1 / 47.5 / 11.3 / 2.5 / 2.1
Ethanol / G0gsolv,el/ kcal mol-1 / -15.9 / -9.8 / -24.5 / -17.0
G0gsolv,cd/ kcal mol-1 / 29.9 / 1.5 / -12.0 / -8.9
Diethylether / G0gsolv,el/ kcal mol-1 / -7.5 / -4.6 / -16.1 / -11.4
G0gsolv,cd/ kcal mol-1 / 34.7 / 7.1 / -24.4 / -19.4

Table SI2. CPCM continuum model free energy terms for Pc monomer and Pc45 dimer configuration obtained at BLYP(UAKS)/DGDZVP level

CPCM term / Water / Ethanol / Diethylether
Monomer / 1SASA/ Å2 / 523 / 521 / 577
2G0gsolv,cav/ kcal mol-1 / 58.4 / 43.1 / 45.7
3G0gsolv,disp/ kcal mol-1 / -55.6 / -48.7 / -45.1
4G0gsolv,rep/ kcal mol-1 / 8.5 / 7.1 / 6.6
Dimer / SASA/ Å2 / 736 / 725 / 762
G0gsolv,cav/ kcal mol-1 / 113.4 / 88.2 / 88.8
G0gsolv,disp/ kcal mol-1 / -77.7 / -68.0 / -63.0
G0gsolv,rep/ kcal mol-1 / 11.7 / 9.7 / 8.8

1SASA = solvent accessible surface area;2Cavitation term; 3Dispersion term;4Repulsion term.

Table SI3. Basis set dependence of the electrostatic free energy contribution as exemplified for MB in aqueous solution using SMD model at BLYP level

G0gsolv,el/ kcal mol-1
DGDZVP / def2-svp / def2-tzvpp
Dimer (a) / -137.1 / -133.1 / -135.9
Monomer (b) / -48.4 / -46.1 / -47.7
Total (a-2*b) / -40.3 / -40.9 / -40.5

Table SI4. Solvation free energy contributions obtained in water, ethanol and diethylether for the MBanti configuration at BLYP/DGDZVP level

CPCM / SMD
Dimer / Monomer / Dimer / Monomer
Water / G0gsolv,el/ kcal mol-1 / -126.2 / -41.4 / -137.1 / -48.4
G0gsolv,cd/ kcal mol-1 / 21.3 / 2.6 / 8.4 / 4.4
Ethanol / G0gsolv,el/ kcal mol-1 / -120.8 / -39.8 / -131.1 / -46.2
G0gsolv,cd/ kcal mol-1 / 8.4 / -3.0 / -4.1 / -2.3
Diethylether / G0gsolv,el/ kcal mol-1 / -88.1 / -27.7 / -94.0 / -32.8
G0gsolv,cd/ kcal mol-1 / 14.5 / 0.6 / -9.4 / -5.9

Table SI5. CPCM continuum model free energy terms for MB monomer and MBantidimer configuration obtained at BLYP(UAKS)/DGDZVP level

CPCM term / Water / Ethanol / Diethylether
Monomer / 1SASA/ Å2 / 330 / 330 / 358
2G0gsolv,cav/ kcal mol-1 / 34.7 / 25.6 / 27.0
3G0gsolv,disp/ kcal mol-1 / -39.6 / -52.0 / -48.2
4G0gsolv,rep/ kcal mol-1 / 7.5 / 6.2 / 5.6
Dimer / SASA/ Å2 / 503 / 498 / 530
G0gsolv,cav/ kcal mol-1 / 69.5 / 51.2 / 54.2
G0gsolv,disp/ kcal mol-1 / -59.5 / -34.7 / -32.1
G0gsolv,rep/ kcal mol-1 / 11.3 / 9.3 / 8.5

1SASA = solvent accessible surface area;2Cavitation term; 3Dispersion term;4Repulsion term.

Table SI6. Solvation free energy difference obtained in ethanol and diethylether for the more stable configurations of MB and Pc at BLYP/DGDZVP level

Model / G0gsolv,el/
kcal mol-1 / G0gsolv,cd/
kcal mol-1 / G0gsolv/
kcal mol-1
MBanti
CPCM/Ethanol / -41.2 / 14.4 / -26.8
CPCM/Diethylether / -32.7 / 13.4 / -19.3
SMD/Ethanol / -38.7 / 0.5 / -38.2
SMD/Diethylether / -28.3 / 2.4 / -25.9
Pc45
Model / G0gsolv,el/
kcal mol-1 / G0gsolv,cd/
kcal mol-1 / G0gsolv/
kcal mol-1
CPCM/Ethanol / 3.6 / 26.9 / 30.5
CPCM/Diethylether / 1.7 / 20.5 / 22.2
SMD/Ethanol / 9.5 / 5.8 / 15.3
SMD/Diethylether / 6.8 / 14.4 / 21.2

1