DFT study of zinc, cadmium, mercury, copper, silver, and gold complexes of 21,23-dioxaporphyrin and one-dimensional arrays of those complexes.

Abstract

Complexes of 21,23-dioxaporphyrin with neutral Zn, Cd, Hg, Cu, Ag, and Au atoms as well as some one-dimensional arrays of those complexes containing up to ten repeat units were modeled at the PBE/def2-TZVPP level of theory with D3 empirical dispersion correction. The binding energy between the metal atom and the macrocycle was found to vary from 90 kcal/mol for Cu to -14 kcal/mol for Hg. Strong charge transfer from the metal to the macrocycle accompanied complex formation. The complexes were able to form dimers and nanoarrays that were held together mostly by dispersion forces. Different types of dimers were studied: face-to-face (F) and two types of parallel-displaced ones. F dimers were calculated to be the lowest-energy structures for Cu and Ag systems. Nanoarray formation was studied for these complexes. The band gaps (Eg) of the nanoarrays were found to be smaller than 1 eV, and decreased slightly as the number of repeat units in the nanoaggregates increased. The ionization potentials and electron affinities were greatly affected by the number of repeat units due to the delocalization of polarons over the entire nanoarray. The polaron delocalization and the related reorganization energies depended to a considerable extent on the metal present in the complex. For the studied nanoarrays, the reorganization energies for hole and electron transport decreased linearly with 1/n, where n is the number of repeat units in the nanoaggregate; for an infinitely long chain, the reorganization energy was zero for electron transport and 0.03-0.04 eV for hole transport.