Ground state charge transfer complex formation of some metalloporphyrins with aromatic solvents

Formation of charge transfer complex between metalloporphyrins and aromatic solvents in tetrahydrofuran media: A density functional study

We have investigated the possible formation of charge transfer (CT) complexes of metallotetraphenylporphyrins (MTPhP with M = Mn, Fe, Co, Ni and Cu) and metallooctaethylporphyrins (MOEtP with M = Mn, Fe, Co, Ni, Cu and Zn) with the aromatic solvents, namely benzene, chlorobenzene, benzonitrile and toluene, respectively, in the tetrahydrofuran (THF) media. We have carried out energy minimization calculations of the hybrid systems (metalloporphyrins and aromatic solvents) in 1:1 and 1:2 stoichiometry in presence of THF media. We have analyzed the role of metal present in the metalloporphyrin in the formation of complexes for both 1:1 and 1:2 stoichiometry. Our analysis reveals that the MTPhP-solvent hybrid system is more stable compared to the MOEtP-solvent hybrid system.

Ground state charge transfer complex formation of some metalloporphyrins with aromatic solvents: Further theoretical and experimental investigations

In our earlier work (Chem. Phys. Letts. 592 (2014) 149-154), a new broad band was observed in the near infrared region (700-900nm) of the steady state absorption spectra of some metalloporphyrins (zinc tetraphenylporphyrin, zinc octaethylporphyrin and magnesium octaethylporphyrin) in aromatic solvents (chlorobenzene, 1,2-dichlorobenzene, benzonitrile, benzene and toluene) at high concentrations (~10^-4molL^-1). The band was ascribed to be due to ground state charge transfer complexation between solute and solvent molecules. In the present work, density functional theory calculations are carried out to study the possibility of such ground state charge transfer complex formation between zinc tetraphenylporphyrin and four aromatic solvents viz., benzene, toluene, chlorobenzene and benzonitrile with 1:1 and 2:1 solvent-solute stoichiometries. Also, we determined the association constants for the ground state charge transfer complex formation of zinc tetraphenylporphyrin and zinc octaethylporphyrin with two aromatic solvents (benzene and benzonitrile) by Benesi-Hildebrand method.

Fluorescence quenching of 9-cyanoanthracene by metallo-octaethylporphyrins in cyanobenzene

Investigations are carried out on the nature of photoinduced electron transfer reactions within some metallo-octaethylporphyrin (zinc octaethylporphyrin and magnesium octaethylporphyrin) donors and acceptor 9-cyanoanthracene in cyanobenzene at 300 K by steady state and time-resolved spectroscopic methods. Acceptor is selectively excited at 366 nm and 374 nm for steady state and time-resolved measurements, respectively, where donor metalloporphyrins possess negligible absorbance. Evidence is found for simultaneous occurrence of Förster's type singlet–singlet energy transfer process along with electron transfer. High exergonic values of Gibbs free energy change for both forward and back electron transfer reactions indicate the possibility of occurrences of these two consecutive processes in the Marcus inverted region.