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Updated: Jan 8, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

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Published on: June 10, 2021

メソ修飾ポルフィリノイド：刺激駆動型の構造可塑性、π共役の変調、およびビスRh(I)錯体形成

Rampal Vishwakarma¹, Mainak Das², A Srinivasan¹

¹School of Chemical Sciences, National Institute of Science Education and Research (NISER), An OCC of Homi Bhabha National Institute, Bhubaneswar 752050, Odisha, India.

Inorganic chemistry

|December 22, 2025

Abstract:

Topology and the extent of π-electron delocalization govern the (anti)aromatic behavior in macrocycles. We report meso-carbon-amended porphyrinoids with ortho-benzannulation at the periphery for rigidity and vinylogous linkages for flexibility. This design enables stimuli-responsive conformational plasticity and tunable (anti)aromaticity, manifesting as moderate Hückel antiaromaticity in freebases, weak Möbius aromaticity upon protonation, and nonaromaticity through bis-Rh(I) complexation, resulting in foldameric structures with η² coordination and panchromatic absorption. Thus, this design reveals topology-property relationships in π-conjugated macrocycles.

キーワード:

大環状化合物芳香族性構造可塑性 π共役系ロジウム錯体

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関連する概念動画

Photochemical Electrocyclic Reactions: Stereochemistry

Photochemical Electrocyclic Reactions: Stereochemistry

The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation

Structural Isomerism

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...

[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement

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The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.

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Sigmatropic rearrangements are a class of pericyclic reactions in which a σ bond migrates from one part of a π system to another. These are intramolecular rearrangements where the total number of σ and π bonds remain unchanged.
Sigmatropic shifts are classified based on an order term [i,&VeryThinSpace;j&VeryThinSpace;], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in 1,5-hexadiene, referred...

Stereoisomerism

Stereoisomerism

Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...

Valence Bond Theory

Valence Bond Theory

Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...