Kinetic stability of lanthanide diphthalocyanines from praseodymium to lutetium

Dissociation kinetics and state of lanthanide diphthalocyanines (Pc) from praseodymium to lutetium in concentrated sulfuric acid were investigated. Rate constants and activation parameters of the complex dissociation reaction, as well as concentrational (as regards H3O+) dependence of the dissociation rate constants, were determined. The assumption on the existence of dimers of diphthalocyanines PcLnPc:PcLnPc in concentrated H2SO4 was substantiated. Tendency to the formation of the dimers decreases in the lanthanide series mentioned. Using the dependence of pk diss of Pc of rare earths from praseodymium to thulium on ordinal number of the elements, the presence of covalent contribution with participation of f-orbitals in the donor-acceptor bond was shown