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Related Concept Videos

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
Thermal Electrocyclic Reactions: Stereochemistry01:17

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The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Formation of Complex Ions03:45

Formation of Complex Ions

A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...
Photochemical Electrocyclic Reactions: Stereochemistry01:26

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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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Thermal and Photochemical Electrocyclic Reactions: Overview

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Electron Transport Chain: Complex III and IV01:43

Electron Transport Chain: Complex III and IV

During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...

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Related Experiment Video

Updated: May 21, 2026

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
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Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene

Published on: March 20, 2017

Intimate electronic coupling in cationic homodimeric iridium(III) complexes.

Ahmed M Soliman1, Daniel Fortin, Pierre D Harvey

  • 1Département de Chimie, Université de Sherbrooke and the Centre Québécois sur les Matériaux Fonctionnels, Sherbrooke, QC, Canada J1K 2R1.

Dalton Transactions (Cambridge, England : 2003)
|June 28, 2012
PubMed
Summary

Two new iridium(III) dinuclear complexes exhibit electronic coupling between metal centers, influencing their photophysical properties. These findings advance understanding of charge-transfer transitions in organometallic compounds.

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Thermochemical Studies of Ni(II) and Zn(II) Ternary Complexes Using Ion Mobility-Mass Spectrometry
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Thermochemical Studies of Ni(II) and Zn(II) Ternary Complexes Using Ion Mobility-Mass Spectrometry

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Thermochemical Studies of Ni(II) and Zn(II) Ternary Complexes Using Ion Mobility-Mass Spectrometry
16:11

Thermochemical Studies of Ni(II) and Zn(II) Ternary Complexes Using Ion Mobility-Mass Spectrometry

Published on: June 8, 2022

Area of Science:

  • Organometallic Chemistry
  • Photophysics
  • Materials Science

Background:

  • Iridium(III) complexes are extensively studied for their photoluminescent properties.
  • Dinuclear metal complexes offer unique electronic interactions compared to mononuclear counterparts.
  • Diyne-linked ligands provide a rigid scaffold for constructing multinuclear metal systems.

Purpose of the Study:

  • To synthesize and characterize novel cationic iridium(III) homodinuclear complexes.
  • To investigate the electronic coupling and photophysical properties of these dinuclear complexes in comparison to mononuclear models.
  • To elucidate the charge-transfer characteristics and emission mechanisms.

Main Methods:

  • Synthesis of iridium(III) homodinuclear and mononuclear complexes.
  • Absorption and emission spectroscopy (UV-Vis, photoluminescence).
  • Electrochemical studies (cyclic voltammetry).
  • Density Functional Theory (DFT) and Time-Dependent DFT (TDDFT) calculations.

Main Results:

  • Dinuclear complexes show red-shifted absorption bands due to charge-transfer transitions.
  • Electrochemical studies reveal significant electronic coupling between iridium centers in one dinuclear complex, indicated by multiple oxidation waves and a reduced HOMO-LUMO gap.
  • Emission spectra are generally broad with modest quantum efficiencies, and DFT/TDDFT suggests a mixed metal-to-ligand/ligand-to-ligand charge transfer (MLCT/LLCT) emission process.

Conclusions:

  • The diyne linker facilitates electronic communication between iridium(III) centers in dinuclear complexes.
  • Photophysical properties, including absorption and emission, are modulated by the dinuclear structure and the nature of the cyclometallating ligands.
  • The emission mechanism involves a combination of MLCT and LLCT transitions, providing insights for designing advanced luminescent materials.