Related Experiment Video
Updated: Jun 22, 2026

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
Published on: March 20, 2017
Excited-state lifetime of propadienylidene, l-C3H2
Bastian Noller1, Markus Margraf, Christian Schröter
1Institute of Physical Chemistry, University of Würzburg, Am Hubland, D-97074, Würzburg, Germany.
Abstract:
The excited-state dynamics of the singlet carbene propadienylidene, l-C(3)H(2), were investigated by femtosecond time-resolved photoionisation. The carbene was excited into the C (1)A(1) state with 250 nm pulses and the subsequent excited state dynamics were probed by multiphoton ionization with 800 nm pulses. The lifetime of the C (1)A(1) state was determined to be 70 fs. In agreement with recent nanosecond experiments, we assume that the carbene deactivates to the electronic ground state where it subsequently dissociates. Since propadienylidene was generated from 3-bromo-1-iodopropyne, two further radical intermediates were studied, IC(3)H(2) and C(3)H(2)Br. For both species, an ultrafast excited state decay was observed with an upper limit of 40 fs for the respective lifetimes.
Related Concept Videos
π Molecular Orbitals of 1,3-Butadiene
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Stability of Conjugated Dienes
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
Diels–Alder Reaction: Characteristics of Dienes
Characteristics of the diene
Conformation
The simplest example of a diene is 1,3-butadiene, an acyclic conjugated π system. At room temperature, the molecule exists as a mixture of s-cis and s-trans conformers by virtue of rotation around the carbon–carbon single bond. Although the s-trans isomer is more stable, the...
Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...

