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Related Concept Videos

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...
Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene01:14

Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene

Electrophilic addition of halogens to alkenes proceeds via a cyclic halonium ion to form a 1,2-dihalide or a vicinal dihalide.
Formation of Halohydrin from Alkenes02:41

Formation of Halohydrin from Alkenes

An alkene, such as propene, reacts with bromine in the presence of water to yield a halohydrin. Halohydrins contain a halogen and a hydroxyl group attached to adjacent carbons. When the halogen is bromine, it is called a bromohydrin, while a chlorohydrin has chlorine as the halogen.
Halogenation of Alkenes02:46

Halogenation of Alkenes

Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Photochemical Electrocyclic Reactions: Stereochemistry01:26

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

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Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives
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Dual Macrocycle Strategy: CB[7]/CB[8] Encapsulation Unlocks Enhanced RTP in Aqueous Bromophenyl Pyridinium Cationic

Sk Samsul Ghaus1, Mridusmita Nath1, Bikram Das2

  • 1Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India.

Chemistry, an Asian Journal
|June 19, 2026
PubMed
Summary
This summary is machine-generated.

This study developed a metal-free, aqueous room-temperature phosphorescence (RTP) system using supramolecular host-guest chemistry. Cucurbiturils (CB[7]/[8]) encapsulate a pyridinium derivative, enhancing RTP emission and lifetime for bioimaging and sensing.

Keywords:
CB[7]/CB[8]ISCRTPhost–guest bindingsupramolecular assembly

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Area of Science:

  • Supramolecular Chemistry
  • Materials Science
  • Photophysics

Background:

  • Developing efficient room-temperature phosphorescence (RTP) in aqueous, metal-free systems is challenging.
  • Existing methods often rely on metal complexes or non-aqueous solvents.
  • There is a need for robust, environmentally friendly phosphorescent materials for various applications.

Purpose of the Study:

  • To demonstrate a supramolecular host-guest approach for activating and amplifying RTP in water.
  • To investigate the use of cucurbiturils (CB[7] and CB[8]) as molecular containers for a metal-free organic phosphor.
  • To enhance phosphorescence properties like emission intensity and lifetime.

Main Methods:

  • Utilized a brominated pyridinium derivative (PTPyBr) as the organic phosphor.
  • Employed cucurbit[7]uril (CB[7]) and cucurbit[8]uril (CB[8]) as supramolecular hosts.
  • Confirmed host-guest complexation using 1H NMR titration, Job's plot, and isothermal titration calorimetry.

Main Results:

  • Supramolecular encapsulation significantly enhanced RTP emission (2.27-fold with CB[7], 2.60-fold with CB[8]).
  • Phosphorescence lifetime was notably prolonged: 190 µs (free PTPyBr) to 390 µs (CB[7]) and 750 µs (CB[8]).
  • Demonstrated a 1:1 host-guest stoichiometry, indicating effective stabilization of the phosphor.

Conclusions:

  • A highly adaptable supramolecular methodology for generating robust, metal-free RTP in aqueous environments was introduced.
  • The host-guest approach effectively inhibits molecular motion and vibrational dissipation, boosting phosphorescence.
  • This strategy holds promise for applications in bioimaging, sensing technologies, and luminescent materials.