QUANTUM COMPUTATIONAL STUDIES ON PORPHYCENE - Theoretical and Computational Research in the 21st Century - page 157

9.1 INTRODUCTION
Porphycene is a constitutional isomer of porphyrin that has attracted strong
interest because of its versatile medicinal use such as its use in the pho-
todynamic therapy, which is a promising treatment for cancer. The chem-
istry of porphycene is interesting because of its biological significance.
The aromatic macromolecule porphycene has been the object of physico-
chemical research for years. Porphycene exhibits high fluorescence yields,
which can be used for tumor detection [1].The compound possesses strong
intramolecular hydrogen bonds and it undergoes rapid tautomerization.
The compound and its derivatives show strong absorptions in the red re-
gion of the UV-vis spectrum. These unique physical and optical prop-
erties of the compounds have made them suitable for use in biomedical
applications and in the design of new materials. They are mainly used for
photodynamic therapy, which is a promising treatment for cancer. This
theoretical study was designed to provide more detailed information on
the various binding sites of the porphycene.
From the early days of modern science, the explanation of the molecu-
lar interactions has been a great challenge from the experimental as well
as theoretical point of view. A lot of endeavors have been made to explain
the nature of bonding and reactivity of molecular systems based on some
insightful ideas and pragmatic rules [2].
Porphyrins are a group of organic compounds having four pyrrol rings
in their structure. The interesting structures of naturally occurring porphy-
rins, its isomer, and substituted analogs have been perfected by nature to
give functional dyes par excellence [3]. The important roles these tetrapyr-
rolic macrocycles play in vital biological processes, in particular, chloro-
phyll (Mg-porphyrin) plays an important role in the photosynthesis, in
bloodoxygen transport occurs by hemoglobin (Fe-porphyrin), and in the
electron transport process, cytochromes (Fe-porphyrin) play a vital role.
These compounds are clinically effective and because ofthisbiological im-
portance, the porphyrins are called the “Pigments of Life” [3, 4]. The por-
phyrins are highly stable and thus also they are useful in material science
as components in organic metals, molecular wires, and other devicesat-
tributed to the presence of the conjugated π -electrons. Moreover, because
of the advent of photodynamic therapy, porphyrins are now very essential
in the treatment of cancer and dermatological diseases [5]. The porphyr-
ias constitute a heterogeneous group of diseases, all of which exhibit in-
creased excretion of porphyrin or porphyrin precursors. Some forms of