ABSTRACT
Keywords: porphyrin, coordination core, chemical activation, reactivity control
Coordination cores in molecules of porphyrin ligands (H2P) and their complexes with p, d and f metals (MP) are some of their main reaction centres [1-3]. These are complex multifunctional centres, as a rule, N4H2 and MN4, respectively. Their unique reactivity is determined by a combination of a number of factors. They include not only the chemical affinity of atoms and atomic groupings constituting these cores, with respect to electrophilic-nucleophilic reagents, their capability of synchronous donor-acceptor interactions, the possibility of redistributing electronic density from one atomic grouping to another for reasons of their involvement in the united system of π-conjugation [1, 4]. One of the most effective factors is a relatively rigid shielding of these reaction centres by an atomic environment and π-electron cloud of the aromatic macrocycle (Fig. 1). The extent of shielding, in turn, can change under the influence of external effects. This phenomenon was given the name of the macrocyclic effect (MCE) of porphyrins and metalloporphyrins [4-8]. MCE affects the physicochemical properties and reactivity of H2P and MP by means of π-electronic and structural (steric) components. Their effects on various physicochemical processes occurring in the molecule are, as a rule, different and nonsymbate one to another [8].
