Theoretical study on the electronic structure, formation and absorption spectra of lithium, sodium and potassium complexes of N-confused tetraphenylporphyrin

Abstract

The present work is a theoretical study on lithium, sodium and potassium complexes of N-confused tetraphenylporphyrin (NCTPP). Its purpose is to determine the stability, binding, absorption spectra and formation energy of the complexes of NCTPP with sodium and potassium, studied here for the first time. All calculations were carried out employing density functional theory (DFT) and time-dependent DFT, using the B3LYP, PBE0 and M06-2X functionals in conjunction with the 6-31G(d,p) basis set. The results show that the energy ordering of different low-lying minimum energy structures of the three metal complexes is not the same, with the global minimum energy structures of the lithium and sodium resulting from the same tautomer of NCTPP while potassium complexes result from another tautomer of NCTPP. The insertion of Li, Na and K into NCTPP in the presence of THF is exothermic with reaction energies calculated to be −68, −56 and −50kcal/mol using the corresponding metal bis-(trimethylsilyl)amide reagents. The absorption vis–UV spectra are similar for the different metals and the Q and Soret bands are slightly red shifted as the metal changes from Li to K.