Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words χλωρός, khloros and φύλλον, phyllon ("leaf"). Chlorophyll allow plants to absorb energy from light.
Porphyrins are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (=CH−). In vertebrates, an essential member of the porphyrin group is heme, which is a component of hemoproteins, whose functions include carrying oxygen in the bloodstream. In plants, an essential porphyrin derivative is chlorophyll, which is involved in light harvesting and electron transfer in photosynthesis.
Photodynamic therapy (PDT) is a form of phototherapy involving light and a photosensitizing chemical substance used in conjunction with molecular oxygen to elicit cell death (phototoxicity).
δ-Aminolevulinic acid, an endogenous non-proteinogenic amino acid, is the first compound in the porphyrin synthesis pathway, the pathway that leads to heme in mammals, as well as chlorophyll in plants.
Bacteriochlorophylls (BChl) are photosynthetic pigments that occur in various phototrophic bacteria. They were discovered by C. B. van Niel in 1932. They are related to chlorophylls, which are the primary pigments in plants, algae, and cyanobacteria. Organisms that contain bacteriochlorophyll conduct photosynthesis to sustain their energy requirements, but the process is anoxygenic and does not produce oxygen as a byproduct. They use wavelengths of light not absorbed by plants or cyanobacteria. Replacement of Mg2+ with protons gives bacteriophaeophytin (BPh), the phaeophytin form.
Chlorophyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light, and it is a poor absorber of green and near-green portions of the spectrum. Chlorophyll does not reflect light but chlorophyll-containing tissues appear green because green light is diffusively reflected by structures like cell walls. This photosynthetic pigment is essential for photosynthesis in eukaryotes, cyanobacteria and prochlorophytes because of its role as primary electron donor in the electron transport chain. Chlorophyll a also transfers resonance energy in the antenna complex, ending in the reaction center where specific chlorophylls P680 and P700 are located.
Phthalocyanine is a large, aromatic, macrocyclic, organic compound with the formula (C8H4N2)4H2 and is of theoretical or specialized interest in chemical dyes and photoelectricity.
A corrole is an aromatic tetrapyrrole. The corrin ring is also present in cobalamin (vitamin B12). The ring consists of nineteen carbon atoms, with four nitrogen atoms in the core of the molecule. In this sense, corrole is very similar to porphyrin.
Photosensitizers are light absorbers that alter the course of a photochemical reaction. They usually are catalysts. They can function by many mechanisms, sometimes they donate an electron to the substrate, sometimes they abstract a hydrogen atom from the substrate. At the end of this process, the photosensitizer returns to its ground state, where it remains chemically intact, poised to absorb more light. One branch of chemistry which frequently utilizes photosensitizers is polymer chemistry, using photosensitizers in reactions such as photopolymerization, photocrosslinking, and photodegradation. Photosensitizers are also used to generate prolonged excited electronic states in organic molecules with uses in photocatalysis, photon upconversion and photodynamic therapy. Generally, photosensitizers absorb electromagnetic radiation consisting of infrared radiation, visible light radiation, and ultraviolet radiation and transfer absorbed energy into neighboring molecules. This absorption of light is made possible by photosensitizers' large de-localized π-systems, which lowers the energy of HOMO and LUMO orbitals to promote photoexcitation. While many photosensitizers are organic or organometallic compounds, there are also examples of using semiconductor quantum dots as photosensitizers.
Protoporphyrin IX is an organic compound, classified as a porphyrin, that plays an important role in living organisms as a precursor to other critical compounds like heme (hemoglobin) and chlorophyll. It is a deeply colored solid that is not soluble in water. The name is often abbreviated as PPIX.
Sir Alan Rushton Battersby was an English organic chemist best known for his work to define the chemical intermediates in the biosynthetic pathway to vitamin B12 and the reaction mechanisms of the enzymes involved. His research group was also notable for its synthesis of radiolabelled precursors to study alkaloid biosynthesis and the stereochemistry of enzymic reactions. He won numerous awards including the Royal Medal in 1984 and the Copley Medal in 2000. He was knighted in the 1992 New Year Honours. Battersby died in February 2018 at the age of 92.
Temoporfin (INN) is a photosensitizer used in photodynamic therapy for the treatment of squamous cell carcinoma of the head and neck . It is marketed in the European Union under the brand name Foscan. The U.S. Food and Drug Administration (FDA) declined to approve Foscan in 2000. The EU approved its use in June 2001.
Tetraphenylporphyrin, abbreviated TPP or H2TPP, is a synthetic heterocyclic compound that resembles naturally occurring porphyrins. Porphyrins are dyes and cofactors found in hemoglobin and cytochromes and are related to chlorophyll and vitamin B12. The study of naturally occurring porphyrins is complicated by their low symmetry and the presence of polar substituents. Tetraphenylporphyrin is hydrophobic, symmetrically substituted, and easily synthesized. The compound is a dark purple solid that dissolves in nonpolar organic solvents such as chloroform and benzene.
Pheophorbide or phaeophorbide is a product of chlorophyll breakdown and a derivative of pheophytin where both the central magnesium has been removed and the phytol tail has been hydrolyzed. It is used as a photosensitizer in photodynamic therapy.
In chemistry, tetradentate ligands are ligands that bind four donor atoms to a central atom to form a coordination complex. This number of donor atoms that bind is called denticity and is a method of classifying ligands.
Chlorophyllide a and Chlorophyllide b are the biosynthetic precursors of chlorophyll a and chlorophyll b respectively. Their propionic acid groups are converted to phytyl esters by the enzyme chlorophyll synthase in the final step of the pathway. Thus the main interest in these chemical compounds has been in the study of chlorophyll biosynthesis in plants, algae and cyanobacteria. Chlorophyllide a is also an intermediate in the biosynthesis of bacteriochlorophylls.
Dihydrosirohydrochlorin is one of several naturally occurring tetrapyrrole macrocyclic metabolic intermediates in the biosynthesis of vitamin B12 (cobalamin). Its oxidised form, sirohydrochlorin, is precursor to sirohaem, the iron-containing prosthetic group in sulfite reductase enzymes. Further biosynthetic transformations convert sirohydrochlorin to cofactor F430 for an enzyme which catalyzes the release of methane in the final step of methanogenesis.
Light harvesting materials harvest solar energy that can then be converted into chemical energy through photochemical processes. Synthetic light harvesting materials are inspired by photosynthetic biological systems such as light harvesting complexes and pigments that are present in plants and some photosynthetic bacteria. The dynamic and efficient antenna complexes that are present in photosynthetic organisms has inspired the design of synthetic light harvesting materials that mimic light harvesting machinery in biological systems. Examples of synthetic light harvesting materials are dendrimers, porphyrin arrays and assemblies, organic gels, biosynthetic and synthetic peptides, organic-inorganic hybrid materials, and semiconductor materials. Synthetic and biosynthetic light harvesting materials have applications in photovoltaics, photocatalysis, and photopolymerization.
Transition metal porphyrin complexes are a family of coordination complexes of the conjugate base of porphyrins. Iron porphyrin complexes occur widely in Nature, which has stimulated extensive studies on related synthetic complexes. The metal-porphyrin interaction is a strong one such that metalloporphyrins are thermally robust. They are catalysts and exhibit rich optical properties, although these complexes remain mainly of academic interest.
Phosphorus-centered porphyrins are conjugated polycyclic ring systems consisting of either four pyrroles with inward-facing nitrogens and a phosphorus atom at their core or porphyrins with one of the four pyrroles substituted for a phosphole. Unmodified porphyrins are composed of pyrroles and linked by unsaturated hydrocarbon bridges often acting as multidentate ligands centered around a transition metal like Cu II, Zn II, Co II, Fe III. Being highly conjugated molecules with many accessible energy levels, porphyrins are used in biological systems to perform light-energy conversion and modified synthetically to perform similar functions as a photoswitch or catalytic electron carriers. Phosphorus III and V ions are much smaller than the typical metal centers and bestow distinct photochemical properties unto the porphyrin. Similar compounds with other pnictogen cores or different polycyclic rings coordinated to phosphorus result in other changes to the porphyrin’s chemistry.
