Competition studies of the free base octa alkyl substituted porphyrins for the protons were carried using H2TPP. The reaction with H2OEP produces the free base H2OEP, the dication H4OEP+2 and the monocation H3OEP+1. Although the monocation is easily seen in the solution, it is difficult to isolate. The cause appears to be a type of disproportionation reaction taking place upon crystallization, where the dication is formed at the expense of the monocation. In each experiment, an equimolar solution of two free-bases was made. Since H2TPP has a large absorption for the dication at 650 nm, it was always used as one of the free - bases. By adjusting the ratios of dications and free-bases, we concluded that H2TPP was again preferentially protonated and hence more basic than the octa alkyl substituted porphyrins (H2OEP, H2OMP H2etio1). Computations studies using MM+ and semiempirical methods were used to validate the porphyrin basicity.

Porphyrin basicity competition studies of octa alkyl substituted porphyrins with H2TPP

251st National Meeting (2016)

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