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Related Concept Videos

Five-Membered Heterocyclic Aromatic Compounds: Overview01:13

Five-Membered Heterocyclic Aromatic Compounds: Overview

Heterocyclic aromatic compounds are cyclic compounds that are aromatic and have one or more heteroatoms—atoms other than carbon, in the ring. Depending upon the number of atoms present in the ring, they can be either five or six-membered. Examples of five-membered heterocyclic aromatic compounds include pyrrole, furan, thiophene, and imidazole. Pyrrole consists of one nitrogen atom having one lone pair of electrons. Furan and thiophene have one oxygen and one sulfur heteroatom, respectively.
Hybridization of Atomic Orbitals II03:35

Hybridization of Atomic Orbitals II

sp3d and sp3d 2 Hybridization
Structural Isomerism02:34

Structural Isomerism

Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group with both...
Aromatic Hydrocarbon Anions: Structural Overview01:18

Aromatic Hydrocarbon Anions: Structural Overview

Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
Due to the absence of continuous overlap of p...
Frost Circles for Different Conjugated Systems01:18

Frost Circles for Different Conjugated Systems

The inscribed polygon method is consistent with Hückel’s 4n + 2 rule and helps to learn whether the given cyclic compound is aromatic or not. The compound is stable and aromatic if every bonding molecular orbital (MO) is completely filled with a pair of electrons. However, if the non-bonding or antibonding orbitals are filled with electrons, the compound is unstable and not aromatic. Consider the Frost circle diagrams for cycloalkenes containing 4 to 8 carbons.

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Updated: Jul 7, 2026

Synthesis and Characterization of Multi-Modal Phase-Change Porphyrin Droplets
07:59

Synthesis and Characterization of Multi-Modal Phase-Change Porphyrin Droplets

Published on: October 15, 2021

Structural diversity in expanded porphyrins.

Rajneesh Misra1, Tavarekere K Chandrashekar

  • 1Department of Chemistry, Indian Institute of Technology, Kanpur - 208 016, India.

Accounts of Chemical Research
|February 20, 2008
PubMed
Summary
This summary is machine-generated.

Expanded porphyrins, versatile macrocyclic compounds, exhibit diverse structures and conformations influenced by substituents and heteroatoms. Understanding these structure-function relationships is key to optimizing their applications in areas like photodynamic therapy and nonlinear optics.

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Synthesis and Characterization of Multi-Modal Phase-Change Porphyrin Droplets
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Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
05:51

Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method

Published on: July 19, 2019

Area of Science:

  • Organic Chemistry
  • Supramolecular Chemistry
  • Materials Science

Background:

  • Porphyrin analogues, including expanded porphyrins, have garnered significant research interest.
  • Expanded porphyrins are macrocyclic compounds with tunable electronic properties, containing up to 64 pi electrons.
  • These molecules show promise in applications such as anion binding, photodynamic therapy (PDT), and nonlinear optics.

Purpose of the Study:

  • To systematically understand the structural diversity and conformational variations in expanded porphyrins.
  • To correlate the structure of expanded porphyrins with their function for targeted applications.
  • To provide a comprehensive overview of meso-aryl expanded porphyrins with five to ten pyrrolic macrocycles.

Main Methods:

  • Synthesis and characterization of expanded porphyrins with varying numbers of pyrrolic rings (five to ten).
  • Investigation of conformational changes induced by substituents (meso vs. beta-pyrrole positions) and heteroatom incorporation.
  • Analysis of structural diversity through techniques like X-ray crystallography and spectroscopy (implied).

Main Results:

  • Meso-substituted expanded porphyrins exhibit diverse conformations (normal, inverted, fused, confused, figure eight), influenced by linkage, heteroatoms, and protonation state.
  • Sapphyrins, rubyrins, heptaphyrins, and octaphyrins display rich structural diversity based on core modifications and substituent positions.
  • Planar, aromatic octaphyrins obeying Huckel's rule were achieved through chemical modification, avoiding the typical figure-eight conformation.

Conclusions:

  • The conformation and aromaticity of expanded porphyrins are highly sensitive to structural modifications, including heteroatom placement and protonation.
  • Tailoring the structure of expanded porphyrins allows for control over their properties and potential applications.
  • This work provides a foundation for the rational design of novel expanded porphyrin systems with enhanced functionalities.