Atomic structure and physical properties of fused porphyrin nanoclusters

Abstract

The atomic and electronic structures, mechanical properties and potential barriers of formation of a set of meso–meso β–β fused porphyrin/metalloporphyrin nanopages, nanotapes, nanotubes and 2D nanofabrics were studied by GGA LC-DFT technique using cluster and PBC models. The porphyrin pages of the nanoclusters are connected with each other by graphene fragments formed by meso–meso β–β links. Fusion of all the edges of six porphyrin/metalloporphyrin units produces a novel ~ 1 nm sized molecule of cubic symmetry with a hollow cage inside. It was found that all studied nanoclusters are metastable with formation energies 0.36–7.57 kcal/mol per atom. Under applied mechanical stress, the nanoclusters exhibit superelastic and ultrastrong properties with binding graphene fragments being the weakest links for mechanical rupture. Depending on the spin-dependent reaction pathways, the hollow caged nanoclusters exhibit almost zero or low potential energy barriers (1–10 kcal/mol) during the initial stages of self-assembly. All nanoclusters exibit the main features of the electronic structures of the parent porphyrins, in particular the nature of HOMO/LUMO states and the relative energetic positions of the metal d states. The induced curvature of the hollow cage nanoclusters leads to admixture of more than 2% of the dπ⊥ states to the dσ energy region and formation of vacant superatomic molecular orbitals of d character in cubic ligand field. The Fe -derived hollow-caged nanoclusters reveal extremely high spin states with small energy differences between ferromagnetic and antiferromagnetic configurations, which can be utilized for quantum holonomic computations.