To take full advantage of the opportunities offered by this synthetic advance, it is important to obtain guidance from theory concerning metalloporphene properties as a function of choice of metal and ligands. Such calculations have been published before, 19-24 but they invariably predicted zinc porphene (ZnP) to be a square metallic conductor. This is in disagreement with our experimental results on ZnP, which indicated an absence of metallic conductivity and showed a presence of infrared-active vibrations, revealing that ZnP is in fact a semiconductor (nonzero band gap). In section A of this paper, we show that an appropriate level of theory can account for the observed semiconducting nature of ZnP, and in section B we systematically investigate the electronic structure and geometry of metalloporphenes containing elements from the first transition row of the periodic table, Sc-Zn, revealing a rich landscape of tunable materials.