“…This class of compounds is present in a great variety of natural processes such as photosynthesis (Mg porphyrins), oxygen transport and storage (iron porphyrins), and many others [2]. Besides the interest in understanding these natural processes, porphyrins are also widely studied because of their potential applications in fields such as photonics [3], medicine (e.g., cancer therapy) [4,5], gas sensors [6], molecular devices [7,8], energy conversion, solar cells [9] and light harvesting [10]. In free-base types, two central nitrogen atoms of the porphyrin ring are protonated assuring structural stability [1].…”