Computational design of ZnP(P)4 stacks: Three modes of binding

Abstract

A large variety of metalloporphyrin arrays, including stacks, have been synthesized and extensively explored for their numerous applications in molecular devices. Motivated by the phenomenon of formation of stacks by regular metalloporphyrins, we performed the computational check of the stack formation between the MP(P)4 species without any linkers or substituents. For this we chose the ZnP(P)4 species as the simplest MP(P)4 compound. Three modes of binding or coordination were found to be possible between the monomeric ZnP(P)4 units. The “convexity-to-convexity” dimer I generally is the most stable compound with the highest binding energy. The dimers II and III are generally bound significantly weaker than the “convexity-to-convexity” dimer I. In the dimer I, the strongly convex shape of both monomer units was demonstrated. The Zn–Zn distances in the dimer I, ca. 3.5[Formula: see text]Å, were computed to be significantly shorter than in two other dimers. This could lead to additional interactions between the metal centers with unpaired d-electrons involved in the formation of such a dimer. In the dimer I significant decrease of the charge was found on the Zn-centers, along with slight decrease of the positive charge on the P-centers coordinated to the Zn-centers of another monomer, and slight buildup of the positive charge on the P-centers not coordinated to the Zn-centers of another monomer.